http://design.maji.go.tz/index.php?title=Special:NewPages&feed=atom&hideredirs=1&limit=50&offset=&namespace=0&username=&tagfilter=&size-mode=max&size=0Ministry of Water DCOM Manual - New pages [en]2024-03-28T15:30:35ZFrom Ministry of Water DCOM ManualMediaWiki 1.34.0http://design.maji.go.tz/index.php/Preface_VOL3Preface VOL32022-07-21T10:45:27Z<p>Juma: Created page with "==Preface== <div style="text-align:justify"> <div style="font-size:17px"> The Government of the United Republic of Tanzania, through the Ministry of Water, oversees the imple..."</p>
<hr />
<div>==Preface==<br />
<div style="text-align:justify"><br />
<div style="font-size:17px"><br />
The Government of the United Republic of Tanzania, through the Ministry <br />
of Water, oversees the implementation of the Water Supply and Sanitation <br />
projects in the country. The Ministry of Water has published several editions of <br />
the relevant Design Manuals. The First edition was the Water Supply and Waste <br />
Wastewater Disposal Manual of 1985/86. The Second edition was titled “Design <br />
Manual for Water Supply and Wastewater Disposal of 1997”. The Third edition <br />
was titled “Design Manual for Water Supply and Wastewater Disposal of 2009”. <br />
These manuals guided the Ministry and the general public in the planning and <br />
design of water supply and sanitation projects in the country. <br />
<br />
As it is now well over ten years since the Third Edition of the Design manual <br />
was adopted, and since many scientific and technological changes have taken <br />
place, including the conclusion of MDGs and adoption of the SDGs in 2015 as <br />
well as useful lessons learnt out of implementation of the WSDP I and WSDP <br />
II (which is still on-going), it has become necessary to revise the 2009 design <br />
manual. Notably, the 3rd Edition Design Manual has, among other things, limited <br />
coverage on the impact of climate change, application software and sanitation <br />
management issues.<br />
<br />
The Ministry is now at various stages of instituting policy and legal reforms that <br />
are deemed necessary for futuristic improvement in the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in Tanzania. Therefore, the 4th Edition of the Design, Construction Supervision, <br />
Operation and Maintenance (DCOM) Manual will make invaluable contribution <br />
in this regard. It is important to recall that the Government has established <br />
the Rural Water Supply and Sanitation Agency (RUWASA), which is responsible <br />
for the supervision, execution and management of rural water supply and <br />
sanitation projects. RUWASA is expected to improve the existing responsibility <br />
and accountability in the management of water and sanitation services in rural <br />
areas. The 4th Edition DCOM Manual will support the sector development and <br />
implementation institutions (including RUWASA, Water Supply and Sanitation <br />
Authorities, development partners, and civil society organisations), and will <br />
provide valuable information relating to implementation of water supply and <br />
sanitation projects in their various stages, from pre-feasibility and feasibility <br />
studies, to planning, designing, construction supervision and operation and <br />
maintenance. <br />
<br />
It is expected that the 4th Edition of the DCOM Manual will position the Ministry <br />
well to systematically and comprehensively implement the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in order to ensure the sustainability of water supply and sanitation projects in <br />
the country. This is also expected to contribute in realising the water sector’s <br />
contribution towards achieving the Tanzania Development Vision 2025, as well as <br />
the various national and international commitments and milestones in the water <br />
sector as also specified in the Agenda 2063 in the "Africa that we want" and the <br />
Sustainable Development Goals (SDGs) on water and sanitation (SDG No. 6). <br />
<br />
The preparation of this Water Supply and Sanitation Projects DCOM Manual <br />
required contributions in form of both human and financial resources. The <br />
Ministry of Water, therefore, takes this opportunity to thank the members of <br />
the Special Committee for Reviewing and Updating the 3rd Edition of the Design <br />
Manual for Water Supply and Wastewater Disposal of 2009, specifically for their <br />
efforts in preparation of this comprehensive 4th Edition of the DCOM Manual. <br />
Thanks are also due to the World Bank for financing the major part of the activities, <br />
and to all others who contributed in the preparation of this new DCOM Manual.<br />
<br />
In the future, the Ministry plans to periodically review and update the DCOM <br />
Manual in order to keep in pace and address emerging changes in policy and <br />
societal needs, emerging technologies, and sustainability concerns in the <br />
implementation of water supply and sanitation projects in the country. <br />
<br />
[[Image:MakameSignature.png|632px|link=DCOM_Volume_I]] <br><br />
<br />
<br />
Next Page: [[Acknowledgements_VOL3|Acknowledgements_VOL3]]<br />
</div><br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Acknowledgements_VOL3Acknowledgements VOL32022-07-21T10:43:34Z<p>Juma: </p>
<hr />
<div><div style="text-align: justify"><br />
<div style="font-size:16px"><br />
Changes of policy and technology have necessitated the preparation of this new <br />
edition of the DCOM Manual for the design, construction supervision, operation <br />
and maintenance of water supply and sanitation projects in Tanzania. The <br />
4th Edition of the DCOM Manual is expected to guide engineers and technicians <br />
in their design work, construction supervision as well as in operation and <br />
maintenance of relevant projects. The manual is to be adopted for all water <br />
supply and sanitation projects in the country.<br />
The 4th Edition of the DCOM Manual has been developed using the following <br />
approaches:<br />
* Review of the 3rd Edition, including benchmarking with design manuals from other countries,<br />
* Website reviews and review of other manuals prepared by consultants who have had working experience in Tanzania,<br />
* Review of Literature data collection and design methods review,<br />
* Data collection from stakeholders, namely: Primary stakeholders-MoW technical and management staff; Private companies that deal with implementation of water supply and sanitation projects; Beneficiaries of water supply and sanitation projects,<br />
* Collection and digitization of existing standard drawings after conversion into metric units as felt necessary,<br />
* Review of the 4th Edition drafts by various stakeholders including MoW staff and other stakeholders outside the MoW,<br />
* Revision of the 4th Edition by incorporating comments and views from all the stakeholders,<br />
* Preparation and submission of the 4th Edition of the DCOM Manual.<br />
<br />
The review and updating of the 3rd Edition of the DCOM Manual is considered to <br />
be a continuous process involving regular updating to incorporate changes in <br />
policy and societal needs, emerging issues, technologies or methods. The MoW <br />
welcomes comments on this new edition of the DCOM Manual from users in <br />
order to facilitate further improvement of future editions.<br />
<br />
The new features in the 4th Edition of the DCOM Manual include mainstreaming <br />
of climate change impacts and use of various types of software in the design <br />
of water supply and sanitation projects. These features have facilitated the <br />
faster and more accurate analysis of pertinent data. The DCOM manual has also<br />
encouraged the use of Supervisory Control and Data Acquisition Systems (SCADA) <br />
for large urban and generally national projects where local capacity building can <br />
be guaranteed by the providers. It should be borne in mind that relevant software <br />
allows a wide variety of scenarios to be considered. However, it should also <br />
be noted that, despite the critical role of software/models in guiding decision-making, its limits should be realized so as to avoid its becoming a substitute for <br />
critical practical evaluation.<br />
<br />
I wish to thank the different stakeholders for their active participation and support <br />
in contributing towards the various inputs during the course of preparation of this <br />
DCOM Manual. They include those from within and outside the Ministry of Water <br />
as well as Development Partners, NGOs, Consultants, Suppliers and Contractors <br />
as well as other Ministries. The review team of engineers and technicians from <br />
MoW, RUWASA, WSSA who worked with the Special Committee for three days in <br />
March 2020 are hereby gratefully acknowledged.<br />
<br />
Finally, I take this opportunity to thank the members of the Special Committee on <br />
Reviewing and Updating the 3rd Design Manual of 2009 under the Chairmanship <br />
of Eng. Prof. Tolly S. A. Mbwette for diligently undertaking this assignment.<br />
<br />
[[Image:Mkumbo_Signature.png|800px|link=Acknowledgements]] <br><br />
<br />
<br />
Previous Page: [[Preface_VOL3]] << >> Next Page: [[List_of_Special_Committee_Members_volume_III]]<br />
</div><br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_One:Introduction_VOL1Chapter One:Introduction VOL12022-07-21T10:36:54Z<p>Juma: Created page with "=Chapter One: Introduction= <div style="text-align:justify"> The preparation of this DCOM manual was preceded by an overview of five important global considerations of Water S..."</p>
<hr />
<div>=Chapter One: Introduction=<br />
<div style="text-align:justify"><br />
The preparation of this DCOM manual was preceded by an overview of five important global considerations of Water Supply and Sanitation prior to reviewing the water and sanitation sector in Tanzania. This was followed by an explanation of the rationale for the preparation of the 4th edition. The introductory chapter is concluded by presenting the organization of the manual as well as the purpose and content of this volume of the DCOM manual.<br />
<br />
==Global Consideration on Water Supply and Sanitation==<br />
=== Sustainable Development Goals (SDGs)===<br />
In 2015, world leaders convened at the United Nations Headquarters in New <br />
York and adopted the 2030 Agenda for Sustainable Development. Governments <br />
responded to the common development challenges then faced and to the changing <br />
world around them by uniting behind a truly forward-looking, yet urgent plan to <br />
end poverty and create shared prosperity on a healthy and peaceful planet. The <br />
central principle of Agenda 2030 is leaving no one behind in achieving the 17 <br />
SDGs through 169 targets.<br />
<br />
The 2030 Agenda for Sustainable Development adopted at the UN Summit <br />
includes SDG 6 on Water and Sanitation and in December 2016, the United Nations <br />
General Assembly unanimously adopted the resolution “International Decade <br />
for Action-Water for Sustainable Development” (2018–2028) in support of the <br />
achievement of SDG 6 on water and sanitation and the related targets (United <br />
Nations, 2015). It should also be noted that, water and sanitation are at the heart <br />
of the Paris Agreement on climate change 2015 (UNFCC (2015).<br />
<br />
<br />
Ensuring availability and sustainable management of water and sanitation for all <br />
has therefore been, for a long while, an important topic at the United Nations and <br />
is now turning this vision into a reality, through national leadership and global <br />
partnerships. Water and sanitation are at the core of sustainable development <br />
and the range of services they provide, underpin poverty reduction, economic <br />
growth and environmental sustainability. The world needs to transform the way <br />
it manages water resources and the way it delivers water and sanitation services <br />
for billions of people.<br />
<br />
The designers and engineers, therefore, have the responsibility to support the <br />
Government of Tanzania in achieving the SDG 6, where population growth and <br />
rapid urbanisation have intensified demand for water and sanitation services <br />
beyond all past thresholds.<br />
<br />
===Climate Change and Resilience to Climate Change===<br />
<br />
Climate change is now recognized as one of the defining challenges for the 21st <br />
century. More frequent, intense and extreme weather events continue to result in <br />
higher incidences of floods and droughts around the planet. The ensuing adverse <br />
impacts of climate change on water and sanitation services constitute a serious <br />
threat to human health and overall development of nations. Ensuring optimal <br />
resilience of water and sanitation services in a globally changing climate context <br />
will continue to be crucial for maintaining the momentum of making progress in <br />
health and general socio-economic development. Climate variability is already a <br />
threat to the sustainability of water supplies and sanitation infrastructure. <br />
<br />
Flood occurrences continue to cause shocks for affected populations and to <br />
challenge water and sanitation managers. In many places floods are likely to <br />
become more frequent with intensification of climate change, thus;<br />
<br />
* Floods can have catastrophic consequences for basic water and sanitation infrastructure. Such damage can take years to repair. <br />
* On a smaller scale, drinking-water infrastructure can be flooded and be put out of commission for days, weeks or months. <br />
* Where flooding of sanitation facilities occurs, there may not only be a break in services, but the resultant flooding may distribute human excreta and its attendant health risks across entire neighborhoods and communities.<br />
<br />
Droughts occur unpredictably worldwide. In many places they are likely to become <br />
more frequent and more widespread with climate change. For example: Falling <br />
groundwater tables and reduced surface water flows can lead to wells drying <br />
up, extending distances that must be travelled to collect water, and increasing <br />
water source pollution. In response, drilling rigs, which would otherwise be used <br />
to increase access, may be redeployed to renew or replace out-of-service wells, <br />
slowing the actual progress in extending access.<br />
<br />
Since climate change is likely to affect water sources and infrastructure in <br />
Tanzania, it must therefore be taken into consideration (i.e. ensure enhanced <br />
adaptation capacity) in design, operation and maintenance of water and sanitation <br />
infrastructure or projects. Globally, climate change studies are coordinated by <br />
the United Nations Framework Convention on Climate Change (UNFCCC) and <br />
the Inter-Governmental Panel on Climate Change (IPCC). Accordingly, designers <br />
should use the latest information, data and model predictions available and <br />
include statements on what measures, if any, have been allowed for in order <br />
to cope up with (or adapt to) climate change within the time frame of pertinent <br />
project design (i.e. design period)<br />
<br />
===Public Private Partnership in Water Supply and Sanitation Projects in Developing Countries===<br />
One of the key challenges faced by water authorities in Developing Countries (DC) <br />
is how best to manage service delivery obligations to rural communities. Even in <br />
decentralized sectors, water authorities may find it hard to provide services to <br />
remote rural communities. It is recognized that water user associations and/or <br />
local private operators may be best placed to provide services as they are close <br />
to the users. The majority of the agreements are currently in place in the short <br />
term (1 to 3 years) management or operation and maintenance contracts for <br />
existing systems that involve minimal investment from the private sector. One <br />
key issue that arises repeatedly though is how to effectively regulate and monitor <br />
performance of activities under these contracts.<br><br />
<br />
Globally, activities undertaken in 2005 suggest that private participation in the <br />
water sector is entering a new phase. New private firm involvement is continuously <br />
focusing on smaller projects and bulk facilities. Contractual arrangements <br />
involving utilities are combining private operations with public financing and new <br />
players are entering the market. <br><br />
<br />
In an infrastructure-intensive sector, improving access and service quality to meet <br />
the SDGs cannot be done without massive investment. Around the developing <br />
world, the water sector is chronically under-funded and inefficient in addition to <br />
giving low priority to sanitation. In this context, Public-Private Partnerships (PPPs) <br />
can be a mechanism (among others) to help Governments in funding the much <br />
needed investment and deploying technologies and efficiency that can improve <br />
the performance and financial sustainability of the water and sanitation sector.<br><br />
<br />
Governments are currently using private firms in the water and sanitation sector <br />
increasingly to finance and operate bulk water supply and wastewater treatment. <br />
New technologies and innovations such as desalination and wastewater re-use <br />
are currently being increasingly introduced, where traditional water sources have <br />
become scarce. Utilities are drawing on specific expertise, such as Non-Revenue <br />
Water (NRW) reduction and pressure management, to promote efficiency and <br />
improvement of services. Private investors and providers are increasingly <br />
becoming local and regional, and so raising competition and pushing down <br />
charges.<br><br />
<br />
Most utilities are increasingly turning to the private sector for turnkey solutions <br />
to the designing, building and operating water and wastewater treatment plants, <br />
and in some cases they also provide financing. With new technologies such as <br />
membrane filtration and in wastewater treatment; utilities have faced challenges <br />
in finding the capacity to operate and maintain these facilities and in selecting <br />
the most appropriate technology.<br><br />
Where a utility has the funds or is seeking financing to develop water or <br />
wastewater treatment plants but wishes to draw on the private sector to <br />
Design, Build and Operate (DBO) a facility, then the DBO approach is used.<br />
<br />
The International Financial Institutions (IFIs) are being asked to finance such <br />
approaches. In response, the WB has recently developed a suite of documents <br />
for DBO deployment in water and sanitation projects, including an initial <br />
selection document; a Request for Proposal (RFP) with DBO document based <br />
on The International Federation of Consulting Engineers (FIDIC), an acronym for <br />
its French name Fédération Internationale Des Ingénieurs-Conseils) Gold Book and <br />
a guidance note with guidance on when the DBO approach is appropriate and <br />
how to approach such projects; draft framework for Employer Requirements <br />
and draft Terms of Reference for Consultancy support to carry out the requisite <br />
studies and develop the documents (World Bank, 2010).<br />
<br />
===International Water Law===<br />
The URT is riparian to the following trans-boundary International River Basins: <br />
Congo River Basin, Kagera River Basin, Nile River Basin and Zambezi River Basin. <br />
These water sources are managed using international law on trans-boundary <br />
resources. <br />
<br />
International law is a culture of communication that “constitutes a method of <br />
communicating claims, counter-claims, expectations and anticipations, as well <br />
as providing a framework for assisting and prioritizing such demands” (Shaw, <br />
2008). International water law is the law of non-navigational uses of international <br />
watercourses.<br />
<br />
In international water law, there are two substantive principles that ought to be <br />
taken into consideration when sharing international waters:<br />
<br />
* The principle of equitable utilization which is a more subtle version of the doctrine of absolute sovereign territory. It argues that a (nation) state has absolute rights to all water flowing through its territory.<br />
* The principle of no significant harm is the delicate version of the doctrine of both absolute riparian integrity (every riparian state is entitled to the natural flow of a river system crossing its borders) and historic rights (where every riparian state is entitled to water that is tied to a prior or existing use) (Wolf, 1999).<br />
<br />
There are two relevant international water conventions for trans-boundary <br />
water cooperation. The 1997 Convention on the Law of the Non-navigational <br />
Uses of International Watercourses (i.e. UN Watercourses Convention, 1997), <br />
and the 1992 UNECE Convention on the Protection and Use of Trans-boundary <br />
Watercourses and International Lakes (i.e. UNECE Water Convention, 1992) <br />
which recently broadened its membership beyond the EU to a global audience. <br />
In March 2016, Water Convention became a global multilateral legal and Inter Governmental framework for trans-boundary water cooperation that is open to accession by all UN member states. The soft law of the SDGs provides further impetus to the management of trans-boundary water resources directly through Goal 6.5: ''Implement integrated water resources management at all levels, and through trans-boundary cooperation as appropriate'', and indirectly through Goal <br />
16: ''Promote peaceful and inclusive societies for sustainable development''. In this case, the contribution of designers and engineers is in the provision of tools and information or data to support the needed decision-making.<br />
<br />
The management of water resources that entails extraction of shared <br />
international water resources in the form of rivers, lakes, seas and oceans as <br />
sources are guided by International Conventions and/or Protocols that have to <br />
be subsequently ratified by respective national Parliaments before they become <br />
enforceable. Because Tanzania is a member of the EAC, SADC and the African <br />
Union, it has ratified a number of the conventions and/or protocols that are <br />
associated with water resources management and water supply and sanitation<br />
services. At an African level, Tanzania fully subscribes to the Agenda 2063 that <br />
ensures African development is guided by African experts to attain the aspirations <br />
of “The Africa that we want” with respect to water supply and sanitation services. <br />
Furthermore, as a member of the United Nations, Tanzania’s water supply and <br />
sanitation services are guided by the UN SDGs of 2015 as well as the UNFCCC <br />
(2015) as mentioned earlier on.<br />
<br />
==Development Agenda and Water and Sanitation Sector in Tanzania==<br />
<br />
The Tanzania Development Agenda includes the Tanzania Development Vision <br />
(TDV) 2025). The realization of TDV is carried out through Five Year Development <br />
Plans. Currently, the GoT is implementing the Second Five Year Development <br />
Plan (FYDP II), 2016/17 – 2020/21.<br />
<br />
The Government adopted the TDV in the mid-1986s for socio-economic reforms <br />
and the same continues to be implemented to date. Better and improved water <br />
and sanitation services contribute to one of the attributes of Vision 2025, which <br />
is on high quality livelihood. Thus, the review and update of this manual better <br />
shapes the future in which water and sanitation services will be delivered to <br />
enhance the health and improved livelihoods of normal citizens who are a critical <br />
national labour force.<br />
<br />
The FYDP II has integrated development frameworks of the first Five Year <br />
Development Plan (FYDP I, 2011/2012-2015/2016) and the National Strategy for <br />
Growth and Reduction of Poverty (NSGRP/MKUKUTA II, 2010/2011-2014/2015) <br />
further extended to 2015/2016 - 2019/2020. The FYDP II is built on three pillars <br />
of transformation: industrialization, human development, and implementation <br />
effectiveness, and is aligned to the relevant SDGs. Importantly, industrialization <br />
placeshigh demand on utility supplies e.g. energy and water, so subscribing on <br />
addressing the SDG Goals 6: on water and sanitation.<br />
<br />
Chapter 4 of the FYDP II, sub-chapter 4.3.4 on Water Supply and Sanitation <br />
Services sets key targets by 2020: Access to safe water in rural areas, 85%; regional <br />
centres and Dar es Salaam, 95%. Proportion of rural households with improved sanitation facilities, 75%; regional centres, 50% and Dar es Salaam, 40%. Non-revenue water (NRW) for regional centres, 25%; for Dar es Salaam, 30%. The Key <br />
targets by 2025 are: Access to safe water in rural areas, 90%; regional centres and <br />
Dar es Salaam, 100%. Proportion of rural households with improved sanitation <br />
facilities, 85%; regional centres, 70% and Dar es Salaam, 60%. Non-revenue <br />
water (NRW) for regional centres, 20%; for Dar es Salaam, 25%. One of the tools <br />
towards achieving the key targets of water supply and sanitation is the effective <br />
application of the DCOM manual.<br />
<br />
The Government has a comprehensive framework for sustainable development <br />
and management of water resources where there is an effective policy, legal and <br />
institutional framework. The water sector policy and strategy contains operational <br />
targets to be achieved in terms of coverage and timescale for improving water <br />
resources management, water supply and sanitation. The targets are reflected <br />
in the National Water Sector Development Strategy (NWSDS) of 2006. Based on <br />
the targets of the ruling party manifesto on water coverage for rural areas and <br />
urban areas are 85% and 95% by 2025, respectively which are also articulated in <br />
the WSDP.<br />
<br />
In the context of water supply and sanitation services in Tanzania Mainland, the <br />
Water Supply and Sanitation Authorities (WSSAs), in collaboration with Rural <br />
Water Supply and Sanitation Agency (RUWASA), are responsible for management <br />
of water supply and sanitation services mostly in the urban, towns and rural <br />
areas as well as in areas that used to be managed by National Water Utilities. <br />
The water sector status report of 2017/18 has set water coverage targets of <br />
95% for Dar es Salaam, 90% for other WSSAs and rural areas, 85%.<br />
<br />
The Community Based Water Supply Organisations (CBWSOs) are the basic units <br />
responsible for management of water supply and sanitation services in rural <br />
areas under the overall coordination of RUWASA. The WSSAs are regulated by <br />
the Energy and Water Utilities Regulating Authority (EWURA), while CBWSOs are <br />
regulated by the RUWASA under the Ministry of Water that is in turn responsible <br />
for rural water supply and sanitation services in Tanzania. As part of the ongoing reforms in the MoW, a number of small WSSAs have been clustered with urban WSSAs leading to reduction of WSSAs from 130 to 71. RUWASA has been charged with the task of supervising the operations of 50 small town WSSAs in addition to the CBWSO managed projects.<br />
<br />
The regulatory role of WSSAs is provided by the Energy and Water Utilities <br />
Regulatory Authority (EWURA) and to some extent by RUWASA. With regard to <br />
sanitation, the water sector status report 2017/18 has estimated an average <br />
coverage of sewerage systems to be 30% (2018) in urban areas. On sanitation <br />
achievements, the same report indicates that by 2018, safely managed sanitation <br />
was available to only 21.2% of the population compared to the target of 25%. <br />
When this is compared to the SDG target of 100% by 2030, it can be seen that <br />
Tanzania is lagging behind by far<br />
<br />
=== National Water Policy ===<br />
The National Water Policy (NAWAPO) of 2002 guides the management of the <br />
water sector in Tanzania with major emphasis being on the active participation <br />
of communities, the private sector and the local governments in protecting <br />
and conserving water sources, supplying water and management of water <br />
and sanitation infrastructure. Currently, the review of the NAWAPO is at fairly <br />
advanced stages.<br />
<br />
The main objective of the National Water Policy of 2002 was to develop a <br />
comprehensive framework for sustainable development and management of the <br />
Nation’s water resources, in which an effective legal and institutional framework <br />
for its implementation was put in place. The policy aimed at ensuring that water <br />
beneficiaries participate fully in planning, construction, operation, maintenance <br />
and management of community based domestic water supply schemes. <br />
This policy sought to address cross-sectoral interests in water, watershed <br />
management and integrated and participatory approaches for water resources <br />
planning, development and management. Also, the policy laid a foundation for <br />
sustainable development and management of water resources in the changing <br />
roles of the Government from service provider to that of coordination, policy <br />
and guidelines formulation, and regulation. Other objectives of the water policy <br />
included: increasing the productivity and health of the population through the <br />
assurance of improved water supply and sanitation services to the water users <br />
and to identify and preserve water sources.<br />
<br />
=== Legal and Institutional Framework for Water Supply and Sanitation ===<br />
'''Services'''<br><br />
Basically, the water and sanitation sector is governed by two main broad legal <br />
frameworks namely:<br><br />
I. Water Resource Management Act No.11 of 2009 <br><br />
II. Water Supply and Sanitation Act No. 5 of 2019.<br><br />
In the institutional framework, there are several organs under the Ministry <br />
of Water, which coordinates water supply and sanitation delivery service: the <br />
Directorate of Program Preparation, Coordination and Delivery Unit (PCDU), <br />
Directorate of Water Resources Management, Basin Water Boards (BWBs), <br />
Directorate of Water Supply and Sanitation, Directorate of Water Quality Services, <br />
Rural Water Supply and Sanitation Agency (RUWASA) and Water Supply and <br />
Sanitation Authorities (WSSAs). Special attention is hereby paid to RUWASA as, <br />
in collaboration with respective regional or district authorities is responsible for <br />
planning and managing, and supervising the rural water supply and sanitation <br />
projects, including financial and procurement management, as well as monitoring <br />
and evaluation for contracting consultants and local service providers to assist <br />
with planning and implementation of the projects at the district level and in the <br />
communities.<br />
<br />
Through implementation of WSDP I and II (up to 2019) projects, the role <br />
or participation of the beneficiaries in planning, construction, operation, <br />
maintenance and management of community based domestic water supply<br />
schemes was guaranteed in most of the implemented projects through <br />
establishments of COWSOs in every completed project that was given all the <br />
mandate of making sure the project is sustainable. Among the lessons learnt <br />
from the implementation of WSDP I & II projects was the need for engineers and <br />
consultants to use the MoW Design manuals in order to reduce or eliminate the <br />
many design flaws already observed.<br />
<br />
However, according to the Water Supply and Sanitation Act No. 5 of 2019, the <br />
COWSOs were replaced by CBWSOs and these are expected to have the frontline <br />
responsibility for sustaining rural water supply and sanitation services on behalf <br />
of the beneficiaries (communities). The members of CBWSOs are drawn from <br />
the users but their qualifications and experiences have been better specified <br />
under the Act No.5. The minimum qualifications of the technical staff employed <br />
by CBWSOs has also been explicitly specified to ensure they have the requisite <br />
capability and experience. Their roles as well as the assumed responsibility of <br />
CBWSOs are also explicitly highlighted in the Act No.5 as well as the roles of <br />
RUWASA at different levels.<br />
<br />
=== Coverage and Access to Water Supply Services ===<br />
While the responsibility for provision of sanitation services in rural areas is <br />
principally under the Ministry of Health, Community Development, Gender, <br />
Elderly and Children (MoHCDGEC); following enactment of the Water and <br />
Sanitation Act No. 5 of 2019, RUWASA has also been given some responsibility to <br />
coordinate delivery of sanitation services in areas that are under its jurisdiction. <br />
In areas served by former National Project Water Utilities (WSSA), it is expected <br />
that the MoHCDGEC will liaise closely with both the latter and RUWASA to deliver <br />
sanitation services. It is estimated that by 2019, on average 21.2% of Tanzanians <br />
had access to safely managed sanitation (MoW AGM, 2019) against a National <br />
target of 25%.<br />
<br />
=== Policy Environment for Water and Sanitation Services in Tanzania ===<br />
The management of water resources in Tanzania is guided by the National water <br />
policy of 2002 (URT, 2002) that has been in use over the last 18 years and was <br />
further articulated by the National Water Sector Development Strategy of 2006 <br />
- 2015 (URT, 2008) and the WSDP of 2006-2025. There are currently efforts to <br />
update the national water policy by the Ministry responsible for Water. The most <br />
important national legislation guiding water resources management include <br />
the Water Resources Management Act No.11 (URT, 2009) and all subsequent <br />
amendments as well as the various regulations prepared by the Ministry <br />
responsible for Water.The Water Supply and Sanitation Act No.5 (URT, 2019) and the associated <br />
regulations prepared by the Ministry responsible for Water guide the development <br />
of water supply and sanitation services in Tanzania. The users of this manual are <br />
referred to the URT website for further information. <br />
<br />
As regards sanitation, the Public Health Act of 2009 and The Health Policy of 2007 provide the relevant legal guidance. Other relevant guiding documents include The National Guidelines <br />
for Water, Sanitation and Hygiene for Tanzania Schools (MoEST, 2016), National <br />
Guidelines for Water, Sanitation and Hygiene in Health Care Facilities (MoHCDGEC, <br />
Oct. 2017), Guidelines for the Preparation of Water Safety Plans (MoW, Oct. <br />
2015), National Guidelines on Drinking Water Quality Monitoring & Reporting <br />
(MoW, Jan. 2018) and Guidelines for the Application of Small-Scale, Decentralized <br />
Wastewater Treatment Systems; A Code of Practice for Decision Makers (Mow, <br />
Dec. 2018). Another Swahili document is titled “Mwongozo wa Ujenzi wa Vyoo Bora <br />
na Usafi wa Mazingira” (Guidelines for Construction of Toilets and Sanitation), <br />
(MoHCDGEC, 2014).<br />
<br />
=== Major Stakeholders in Water Supply and Sanitation Projects ===<br />
Effective and efficient implementation of water supply and sanitation projects <br />
will be achieved through the contribution of a number of stakeholders. The <br />
stakeholders of significant importance are described below.<br><br />
<br />
'''(a) Regulatory Authorities'''<br><br />
In order to ensure the smooth implementations of water supply and sanitation<br />
projects, various regulatory authorities have been established from time to time. <br />
The latter, monitor professional conduct of the different parties involved in water <br />
and sanitation projects. These include:<br><br />
(i) Public Procurement Regulatory Authority (PPRA),<br><br />
(ii) Tanzania Bureau of Standards (TBS),<br><br />
(iii) Engineers Registration Board (ERB),<br><br />
(iv) Contractors’ Registration Board (CRB),<br><br />
(v) Energy and Water Utilities Regulating Authority (EWURA),<br><br />
(vi) The National Environmental Management Council (NEMC).<br><br />
<br />
'''(b) Contractors and Consultants''' <br><br />
Contractors are the firms that perform the actual construction of the water projects according to the agreed terms in the contracts. Consultants/Project Managers are firms that design water supply and sanitation projects and supervise the construction works depending on the terms and conditions specified in their respective contracts. Moreover, the consultant, on behalf of the client, approves <br />
completed structures with regards to the specifications given and the standards <br />
required as elaborated in chapter twelve of Volume I of the DCOM manual<br />
<br />
'''(c) National Water Supply and Sanitation NGOs and networks'''<br><br />
The following is a sample list of Non-Governmental Organizations (NGOs) that <br />
deal with a water supply and sanitation services in Tanzania and hence have a <br />
contributing role to the Ministry of Water (MoW):<br><br />
(i) Association of Tanzania Water Suppliers (ATAWAS),<br><br />
(ii) Tanzania Water Supply and Sanitation Network (TAWASANET),<br><br />
(iii) Tanzania Global Water Partnership (GWPTZ).<br><br />
<br />
=== Water Supply and Sanitation Public-Private Partnership in Tanzania ===<br />
The national water policy (NAWAPO) of 2002 (URT) envisaged devolution <br />
elements to be introduced as well as public and civil service reforms. It had <br />
assumed that the Central Government would provide technical and financial <br />
support, coordination and regulation of water supply development while the <br />
private sector was expected to support the communities in planning, design, <br />
construction and supply of materials, equipment, spare parts and to support <br />
operations in some cases. The Development Partners (DPs), NGOs and CBOs <br />
were expected to provide funding and technical assistance to supplement the <br />
Government’s efforts through basket funding.<br />
<br />
In support of the Government the Public-Private Partnership (PPP) policy of 2009 <br />
as also supported by EWURA which prepared the PPP guidelines for water supply<br />
and sanitation (EWURA, 2017) and the relevant legislation that was stipulated in <br />
NAWAPO 2002, the MoW has created the necessary environment for supporting <br />
the private sector such that, a sizeable proportion of the works, services and <br />
goods are procured from private sector Service Providers (SPs) hence assisting <br />
the Government in fulfilling its roles. <br />
<br />
Essentially, one of the successes of NAWAPO 2002 has been the inclusion <br />
of the private sector in water supply and sanitation projects implementation. <br />
Notwithstanding the good experiences, the MoW (2018) indicated that even though <br />
the Water Sector Development Programme (WSDP) Project Implementation <br />
Manual gave a lot of opportunities to the private sector that procured most of <br />
the works, field experience has shown that the capacity of the private sector <br />
in Tanzania is limited in terms of having only a few staff and thereby failing to <br />
supervise the works properly.<br />
<br />
On the other hand, the Ministry of Water organized a forum on enhancing <br />
public private partnership in the water sector. This was held in Dar es Salaam <br />
from 19 to 20 July 2018. In this forum, discussions were held with the private <br />
sector stakeholders where experiences, challenges and recommendations <br />
were obtained with regard to implementation of rural water supply projects in <br />
Tanzania. The forum was a follow up of the Five-Year Development Plan (FYDP) <br />
2016/17-2020/21. The fourth priority area of the FYDP is strengthening project <br />
implementation effectiveness, which earmarked water supply and sanitation one<br />
of the key interventions for achievement. In the forum, the following key issues <br />
were captured:<br><br />
(a) Contract management issues such as delays in decision making by the client,<br> <br />
(b) Payment problems,<br><br />
(c) Procurement problems,<br><br />
(d) Policy issues on Tax exemption for imports,<br><br />
(e) Political interference in the execution of works,<br><br />
(f) Knowledge gap on current technology available for groundwater exploration <br />
based on quality and quantity of water,<br> <br />
(g) Shortage of contractors with capacity to execute water supply projects,<br> <br />
(h) Database issues especially on water resources information, which often end <br />
up with over- or under- designing water supply facilities.<br><br />
(i) Design specifications based on the use of obsolete technologies was <br />
identified as a critical problem.<br> <br />
<br />
Privatization of some or all functions of Operation and Maintenance can be <br />
considered to achieve:<br> (i) efficiency<br> (ii) economy<br> (iii) professionalism and <br>(iv) <br />
financial viability of the system. <br><br />
In order to achieve the above stated objectives, <br />
the private entrepreneur needs to possess:<br> (i) adequately trained, qualified staff <br />
for operation and supervision of the services <br> (ii) equipment, material, testing <br />
and repairing facilities <br> (iii) experience in operating similar systems <br>(iv) financial <br />
soundness <br>(v) capacity to meet the emergency situations.<br><br />
<br />
In order to assist service providers/operators in ensuring financial viability of their <br />
projects through Public-Private Partnerships, the following were recommended:<br><br />
(a) The MoW, through the established in-house Design Unit should provide an <br />
option for on-demand engagement of the private sector at the project level, <br />
in cases where in-house capacity or technology is limited;<br><br />
(b) Enhancement of awareness on other operational modes in PPP as per water <br />
policy;<br><br />
(c) Where applicable, private operators should be engaged in operation and <br />
maintenance of water supply and sanitation services after due diligence; The <br />
same applies to contracting personnel with specialized skills for the repair <br />
and maintenance of specialized equipment or instrumentation as specialized <br />
services for maintenance of such equipment instead of employing additional <br />
staff. Such a practice may ensure proper functioning of the equipment with <br />
least cost;<br><br />
Private operators should be supervised closely to avoid challenges in operation <br />
and maintenance of water supply and sanitation projects (i.e. water supply <br />
connections, facilities and finances).<br />
<br />
== Rationale For The Preparation Of The Fourth Edition Dcom Manual ==<br />
The need to review and update the 2009 Design Manual was emphasised during <br />
the Private-Public Partnership (PPP) stakeholders’ meeting hosted by the MoW <br />
in 2018. During that meeting, the issue of providing designs/specifications that <br />
use old technologies in procurement was indicated as a concern as well as <br />
stressing the need to adopt the latest and appropriate technology. Among the <br />
Recommendations of the Special Committee on Audit of WSDP I & II projects <br />
in rural areas in Tanzania (URT, Nov. 2018), the need to review and update the <br />
design manual and to ensure that all consultants use it was emphasized. The four <br />
volumes of the DCOM manual have been prepared in order to facilitate effective <br />
complimentary planning, design, construction supervision as well as operation <br />
and maintenance of water supply and sanitation projects for urban, peri-urban <br />
and rural areas of Tanzania.<br />
<br />
The manuals will also assist the staff of the Ministry responsible for water and <br />
sanitation projects to effectively undertake their supervisory and coordination <br />
roles and the consultants to undertake designs using the guidelines recommended <br />
in the MoW manual. For Urban and National WSSA or RUWASA staff who may be <br />
involved in design, construction supervision of projects using the Force Account<br />
mode of implementation, the four manuals will prove to be useful in facilitating <br />
step by step supervision. On the other hand, for staff who will be implementing water supply and <br />
sanitation projects, the manuals will provide guidance on how they should <br />
involve all the principal stakeholders including the Community Based Water <br />
Supply Organizations (CBWSO) as foreseen in both the NAWAPO (URT,2002) as <br />
well as the NWSDS (URT, 2008). <br />
<br />
The manuals have been formatted in order to be <br />
more user friendly by allowing navigation within and across the manuals as well <br />
as having the capability to navigate into or from website links with ease using <br />
subject indices that enable a user to search for the needed information almost <br />
instantly. It is hoped that, the manuals will contribute towards improvement of <br />
the contract management capacity of the staff involved in project management <br />
and will eliminate the recurring problem of consultants designing water supply <br />
and sanitation management projects that are below minimum quality standards.<br />
<br />
== About The Fourth Edition Of The Dcom Manual ==<br />
The 4th edition of the DCOM Manual was prepared in 2020, following the review <br />
and updating of the Third Edition of the Water Supply and Wastewater Disposal <br />
Design Manual of 2009. The former manual was prepared in three separate <br />
volumes. These volumes included eight chapters on water supply, three chapters <br />
on wastewater disposal and one chapter on water pipelines standards and <br />
specifications. It should be remembered that the 2nd Edition of the Design Manual <br />
that was titled ''Design Manual for Water Supply and Wastewater Disposal'' was prepared in July 1997 in two volumes with eight chapters and three chapters, respectively. The 1st Edition of the Design Manual was prepared in 1985/86, a few years after the conclusion of the International Water and Sanitation Decade that ended in 1981. Thus, the current edition of the DCOM is adequately informed by <br />
previous edition reviews which incorporate topical and existing challenges and issues. <br />
<br />
A Special Committee of twelve members from The Ministry of Water, RUWASA, <br />
University of Dar es Salaam (UDSM), The Nelson Mandela African Institution of <br />
Science and Technology (NMAIST) and Private Sector undertook the preparation <br />
of the four volumes of this manual. The process of preparing the design manuals <br />
entailed a number of participatory consultations with key stakeholders from the <br />
water and sanitation sector as well as from Ministries of Education, Science & <br />
Technology, Ministry of Health, Community Development, Gender, Elderly and <br />
Children (MoHCDGEC), President’s Office Regional Administration and Local <br />
Government (PORALG) as well as Consultants, Contractors, Materials suppliers <br />
and Development Partners. It also involved undertaking an extensive search of <br />
literature from libraries, conference proceedings, journal publications, websites <br />
of various entities and design manuals from various global, East African and <br />
SADC countries<br />
<br />
== Organisation Of The 4th Edition Of The Dcom Manual ==<br />
The 4th Edition of the DCOM Manual has been prepared in four separate volumes <br />
that are divided as follows:<br />
* '''Volume I''' which presents ''Design of Water Supply Projects'' organized into thirteen chapters; <br />
* '''Volume II''' that dwells on ''Design of Sanitation Projects'' and is divided into six chapters;<br />
* '''Volume III''' titled ''Construction Supervision for Water Supply and Sanitation Projects'' has been structured into five chapters;and<br />
* '''Volume IV''' titled ''Operation and Maintenance for Water Supply and Sanitation Projects'' is organized into nineteen chapters. <br><br />
This Volume IV is organized into five parts as indicated below, and can be used as separate packages for training of different groups of users from the water sector:<br><br />
Part A: Essentials of Operation & Maintenance,<br><br />
Part B: O&M of the Water Supply Sources and Network,<br><br />
Part C: O&M of Water Treatment, Water & Wastewater Quality Compliance,<br><br />
Part D: O&M of Sanitation Projects,<br><br />
Part E: Water Audit, Revenue and Community Participation Management.<br><br />
<br />
== Purpose Of This Volume ==<br />
This volume has been prepared with the main aim of providing engineers <br />
and designers with step by step design approaches for water supply projects. <br />
Observations gathered during the audit of water projects by special audit <br />
committee revealed that one of the reasons for poor performance of water <br />
projects is an outdated design manual. This very first volume of DCOM has been <br />
organized in such a manner that it starts with planning for water projects. The <br />
water projects planning chapter which comes after the introductory chapter <br />
underlines and underscores the significant and major part of the water projects. <br />
Also, the volume covers detailed account of assessment of safe yield of water <br />
sources. Water intakes, treatment and pipelines hydraulic analysis have been <br />
well covered in this volume. Chapter four provides description designs and <br />
specification. The role of stakeholders on water projects has been stipulated in <br />
the last chapter.<br />
<br />
The preparation of this volume aimed to provide an opportunity to guide well <br />
engineers who have been given the responsibility for the design of either a <br />
complete water supply scheme or any component of the same as currently <br />
presented under 16 different topics. Volume I of the DCOM Manual has also <br />
provided the opportunity to link or hyperlink to many other websites and also to <br />
use the index provided at the end of the volume for ease of instant search<br />
<br />
</div><br />
<br />
'''REFERENCES'''<br />
<br />
MALCOLM N. SHAW 2008, International Law, Sixth edition, Cambridge University Press, <br />
Cambridge Uk.,<br><br />
<br />
Rocha Loures F & Rieu-Clarke A (eds) (2013). ''The UN Watercourese Convention in Force:'' <br />
''Strengthening international law for trans-boundary water management.'' Earthscan, Routledge.<br><br />
<br />
SIWI (2015). ''International water law''. Retrieved from: https://www.siwi.org/icwc-course-international-water-law <br><br />
<br />
UNFCC (2015). Paris Agreement on climate change 2015. Retrieved from: https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement <br><br />
<br />
UNFCCC (2015). Paris Agreement. United Nations Framework Convention on Climate Change (UNFCCC). <br><br />
<br />
United Nations (2015). Helping governments and stakeholders make the Sustainable Development Goals (SDGs) a reality. Retrieved from: https://sustainabledevelopment.un.org/ <br><br />
<br />
URT (2000). The Tanzania Development Vision 2025. Ministry of Finance and Planning. <br> <br />
https://www.mof.go.tz/mofdocs/overarch/vision2025.htm.<br />
<br />
URT (2002). The National Water Policy (NAWAPO). United Republic of Tanzania (URT).<br><br />
<br />
URT (2008). The National Water Sector Development Strategy (NWSDS). United Republic of Tanzania.<br />
<br />
URT (2014). ''Mwongozo wa Ujenzi wa Vyoo Bora na Usafi wa Mazingira''. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[List_of_Abbreviations_I|List_of_Abbreviations_I]] << >> Next Page: [[Chapter_Two:_Project_Planning|Chapter_Two:_Project_Planning]]</div>Jumahttp://design.maji.go.tz/index.php/Preface_VOL2Preface VOL22022-07-21T10:25:55Z<p>Juma: Created page with "==Preface== <div style="text-align:justify"> <div style="font-size:17px"> The Government of the United Republic of Tanzania, through the Ministry of Water, oversees the imple..."</p>
<hr />
<div>==Preface==<br />
<div style="text-align:justify"><br />
<div style="font-size:17px"><br />
The Government of the United Republic of Tanzania, through the Ministry <br />
of Water, oversees the implementation of the Water Supply and Sanitation <br />
projects in the country. The Ministry of Water has published several editions of <br />
the relevant Design Manuals. The First edition was the Water Supply and Waste <br />
Wastewater Disposal Manual of 1985/86. The Second edition was titled “Design <br />
Manual for Water Supply and Wastewater Disposal of 1997”. The Third edition <br />
was titled “Design Manual for Water Supply and Wastewater Disposal of 2009”. <br />
These manuals guided the Ministry and the general public in the planning and <br />
design of water supply and sanitation projects in the country. <br />
<br />
As it is now well over ten years since the Third Edition of the Design manual <br />
was adopted, and since many scientific and technological changes have taken <br />
place, including the conclusion of MDGs and adoption of the SDGs in 2015 as <br />
well as useful lessons learnt out of implementation of the WSDP I and WSDP <br />
II (which is still on-going), it has become necessary to revise the 2009 design <br />
manual. Notably, the 3rd Edition Design Manual has, among other things, limited <br />
coverage on the impact of climate change, application software and sanitation <br />
management issues.<br />
<br />
The Ministry is now at various stages of instituting policy and legal reforms that <br />
are deemed necessary for futuristic improvement in the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in Tanzania. Therefore, the 4th Edition of the Design, Construction Supervision, <br />
Operation and Maintenance (DCOM) Manual will make invaluable contribution <br />
in this regard. It is important to recall that the Government has established <br />
the Rural Water Supply and Sanitation Agency (RUWASA), which is responsible <br />
for the supervision, execution and management of rural water supply and <br />
sanitation projects. RUWASA is expected to improve the existing responsibility <br />
and accountability in the management of water and sanitation services in rural <br />
areas. The 4th Edition DCOM Manual will support the sector development and <br />
implementation institutions (including RUWASA, Water Supply and Sanitation <br />
Authorities, development partners, and civil society organisations), and will <br />
provide valuable information relating to implementation of water supply and <br />
sanitation projects in their various stages, from pre-feasibility and feasibility <br />
studies, to planning, designing, construction supervision and operation and <br />
maintenance. <br />
<br />
It is expected that the 4th Edition of the DCOM Manual will position the Ministry <br />
well to systematically and comprehensively implement the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in order to ensure the sustainability of water supply and sanitation projects in <br />
the country. This is also expected to contribute in realising the water sector’s <br />
contribution towards achieving the Tanzania Development Vision 2025, as well as <br />
the various national and international commitments and milestones in the water <br />
sector as also specified in the Agenda 2063 in the "Africa that we want" and the <br />
Sustainable Development Goals (SDGs) on water and sanitation (SDG No. 6). <br />
<br />
The preparation of this Water Supply and Sanitation Projects DCOM Manual <br />
required contributions in form of both human and financial resources. The <br />
Ministry of Water, therefore, takes this opportunity to thank the members of <br />
the Special Committee for Reviewing and Updating the 3rd Edition of the Design <br />
Manual for Water Supply and Wastewater Disposal of 2009, specifically for their <br />
efforts in preparation of this comprehensive 4th Edition of the DCOM Manual. <br />
Thanks are also due to the World Bank for financing the major part of the activities, <br />
and to all others who contributed in the preparation of this new DCOM Manual.<br />
<br />
In the future, the Ministry plans to periodically review and update the DCOM <br />
Manual in order to keep in pace and address emerging changes in policy and <br />
societal needs, emerging technologies, and sustainability concerns in the <br />
implementation of water supply and sanitation projects in the country. <br />
<br />
[[Image:MakameSignature.png|632px|link=DCOM_Volume_I]] <br><br />
<br />
<br />
Next Page: [[Acknowledgements_VOL2|Acknowledgements_VOL2]]<br />
</div><br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Acknowledgements_VOL2Acknowledgements VOL22022-07-21T10:23:22Z<p>Juma: </p>
<hr />
<div><div style="text-align: justify"><br />
<div style="font-size:16px"><br />
Changes of policy and technology have necessitated the preparation of this new <br />
edition of the DCOM Manual for the design, construction supervision, operation <br />
and maintenance of water supply and sanitation projects in Tanzania. The <br />
4th Edition of the DCOM Manual is expected to guide engineers and technicians <br />
in their design work, construction supervision as well as in operation and <br />
maintenance of relevant projects. The manual is to be adopted for all water <br />
supply and sanitation projects in the country.<br />
The 4th Edition of the DCOM Manual has been developed using the following <br />
approaches:<br />
* Review of the 3rd Edition, including benchmarking with design manuals from other countries,<br />
* Website reviews and review of other manuals prepared by consultants who have had working experience in Tanzania,<br />
* Review of Literature data collection and design methods review,<br />
* Data collection from stakeholders, namely: Primary stakeholders-MoW technical and management staff; Private companies that deal with implementation of water supply and sanitation projects; Beneficiaries of water supply and sanitation projects,<br />
* Collection and digitization of existing standard drawings after conversion into metric units as felt necessary,<br />
* Review of the 4th Edition drafts by various stakeholders including MoW staff and other stakeholders outside the MoW,<br />
* Revision of the 4th Edition by incorporating comments and views from all the stakeholders,<br />
* Preparation and submission of the 4th Edition of the DCOM Manual.<br />
<br />
The review and updating of the 3rd Edition of the DCOM Manual is considered to <br />
be a continuous process involving regular updating to incorporate changes in <br />
policy and societal needs, emerging issues, technologies or methods. The MoW <br />
welcomes comments on this new edition of the DCOM Manual from users in <br />
order to facilitate further improvement of future editions.<br />
<br />
The new features in the 4th Edition of the DCOM Manual include mainstreaming <br />
of climate change impacts and use of various types of software in the design <br />
of water supply and sanitation projects. These features have facilitated the <br />
faster and more accurate analysis of pertinent data. The DCOM manual has also<br />
encouraged the use of Supervisory Control and Data Acquisition Systems (SCADA) <br />
for large urban and generally national projects where local capacity building can <br />
be guaranteed by the providers. It should be borne in mind that relevant software <br />
allows a wide variety of scenarios to be considered. However, it should also <br />
be noted that, despite the critical role of software/models in guiding decision-making, its limits should be realized so as to avoid its becoming a substitute for <br />
critical practical evaluation.<br />
<br />
I wish to thank the different stakeholders for their active participation and support <br />
in contributing towards the various inputs during the course of preparation of this <br />
DCOM Manual. They include those from within and outside the Ministry of Water <br />
as well as Development Partners, NGOs, Consultants, Suppliers and Contractors <br />
as well as other Ministries. The review team of engineers and technicians from <br />
MoW, RUWASA, WSSA who worked with the Special Committee for three days in <br />
March 2020 are hereby gratefully acknowledged.<br />
<br />
Finally, I take this opportunity to thank the members of the Special Committee on <br />
Reviewing and Updating the 3rd Design Manual of 2009 under the Chairmanship <br />
of Eng. Prof. Tolly S. A. Mbwette for diligently undertaking this assignment.<br />
<br />
[[Image:Mkumbo_Signature.png|800px|link=Acknowledgements]] <br><br />
<br />
<br />
Previous Page: [[Preface_VOL2]] << >> Next Page: [[List_of_Special_Committee_Members]]<br />
</div><br />
</div></div>Jumahttp://design.maji.go.tz/index.php/List_of_Special_Committee_Members_VOL.1List of Special Committee Members VOL.12022-07-21T10:18:51Z<p>Juma: Created page with "LIST OF SPECIAL COMMITTEE MEMBERS ON REVIEWING AND UPDATING THE 3RD EDITION, <br> DESIGN MANUAL FOR WATER SUPPLY AND WASTEWATER DISPOSAL OF 2009 <br> File:Comiteemembers.PN..."</p>
<hr />
<div>LIST OF SPECIAL COMMITTEE MEMBERS ON REVIEWING AND UPDATING THE 3RD EDITION, <br> DESIGN MANUAL FOR WATER SUPPLY AND WASTEWATER DISPOSAL OF 2009<br />
<br><br />
<br />
[[File:Comiteemembers.PNG|710px]]<br><br />
<br />
[[Image:Dodoma.png|800px]] <br><br />
<br><br />
<br />
<br />
<br />
Previous Page: [[Acknowledgements_VOL.1]] << >> Next Page: [[List_of_Abbreviations I]]</div>Jumahttp://design.maji.go.tz/index.php/Acknowledgements_VOL.1Acknowledgements VOL.12022-07-21T10:12:42Z<p>Juma: </p>
<hr />
<div><div style="text-align: justify"><br />
<div style="font-size:16px"><br />
Changes of policy and technology have necessitated the preparation of this new <br />
edition of the DCOM Manual for the design, construction supervision, operation <br />
and maintenance of water supply and sanitation projects in Tanzania. The <br />
4th Edition of the DCOM Manual is expected to guide engineers and technicians <br />
in their design work, construction supervision as well as in operation and <br />
maintenance of relevant projects. The manual is to be adopted for all water <br />
supply and sanitation projects in the country.<br />
The 4th Edition of the DCOM Manual has been developed using the following <br />
approaches:<br />
* Review of the 3rd Edition, including benchmarking with design manuals from other countries,<br />
* Website reviews and review of other manuals prepared by consultants who have had working experience in Tanzania,<br />
* Review of Literature data collection and design methods review,<br />
* Data collection from stakeholders, namely: Primary stakeholders-MoW technical and management staff; Private companies that deal with implementation of water supply and sanitation projects; Beneficiaries of water supply and sanitation projects,<br />
* Collection and digitization of existing standard drawings after conversion into metric units as felt necessary,<br />
* Review of the 4th Edition drafts by various stakeholders including MoW staff and other stakeholders outside the MoW,<br />
* Revision of the 4th Edition by incorporating comments and views from all the stakeholders,<br />
* Preparation and submission of the 4th Edition of the DCOM Manual.<br />
<br />
The review and updating of the 3rd Edition of the DCOM Manual is considered to <br />
be a continuous process involving regular updating to incorporate changes in <br />
policy and societal needs, emerging issues, technologies or methods. The MoW <br />
welcomes comments on this new edition of the DCOM Manual from users in <br />
order to facilitate further improvement of future editions.<br />
<br />
The new features in the 4th Edition of the DCOM Manual include mainstreaming <br />
of climate change impacts and use of various types of software in the design <br />
of water supply and sanitation projects. These features have facilitated the <br />
faster and more accurate analysis of pertinent data. The DCOM manual has also<br />
encouraged the use of Supervisory Control and Data Acquisition Systems (SCADA) <br />
for large urban and generally national projects where local capacity building can <br />
be guaranteed by the providers. It should be borne in mind that relevant software <br />
allows a wide variety of scenarios to be considered. However, it should also <br />
be noted that, despite the critical role of software/models in guiding decision-making, its limits should be realized so as to avoid its becoming a substitute for <br />
critical practical evaluation.<br />
<br />
I wish to thank the different stakeholders for their active participation and support <br />
in contributing towards the various inputs during the course of preparation of this <br />
DCOM Manual. They include those from within and outside the Ministry of Water <br />
as well as Development Partners, NGOs, Consultants, Suppliers and Contractors <br />
as well as other Ministries. The review team of engineers and technicians from <br />
MoW, RUWASA, WSSA who worked with the Special Committee for three days in <br />
March 2020 are hereby gratefully acknowledged.<br />
<br />
Finally, I take this opportunity to thank the members of the Special Committee on <br />
Reviewing and Updating the 3rd Design Manual of 2009 under the Chairmanship <br />
of Eng. Prof. Tolly S. A. Mbwette for diligently undertaking this assignment.<br />
<br />
[[Image:Mkumbo_Signature.png|800px|link=Acknowledgements]] <br><br />
<br />
<br />
Previous Page: [[Preface_VOL.1]] << >> Next Page: [[List_of_Special_Committee_Members_VOL.1]]<br />
</div><br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_Five:_Design_Standards_and_Specifications:Chapter_Five:_Design_Standards_and_SpecificationsChapter Five: Design Standards and Specifications:Chapter Five: Design Standards and Specifications2022-07-21T05:57:22Z<p>Juma: Created page with "=Chapter Five: Design Standards and Specifications= ==DESIGN STANDARDS== <div style='text-align: justify'> A Standard is the limit of a measure of quality of a product prepare..."</p>
<hr />
<div>=Chapter Five: Design Standards and Specifications=<br />
==DESIGN STANDARDS==<br />
<div style='text-align: justify'><br />
A Standard is the limit of a measure of quality of a product prepared for judgement<br />
and compliance by an authoritative agency, professional or a recognized<br />
body. According to (Business Dictionary, 2020) Standards can be classified as:<br />
Government or statutory agency standards and specifications enforced by law,<br />
<br />
Proprietary standards developed by a firm or organization and placed in public<br />
domain to encourage widespread use, and<br />
<br />
Voluntary standards established through consultation and consensus and<br />
available for use by any person, organization, or industry. Once established,<br />
standards (like bureaucracies) are very difficult to change or dislodge. Standards<br />
that apply for Tanzania water projects will be from the Tanzania Bureau of<br />
Standards, and for construction works, British standards shall be used.<br />
<br />
A list of institutions whose standards are recommended for use in water supply<br />
and sanitation projects design include the following:<br><br />
(a) Tanzania Bureau of Standards,<br><br />
(b) British Standards (BS),<br><br />
(c) American Society for Testing and Materials (ASTM)<br><br />
(d) Deutsches Institut für Normung (DIN); German institute for standardisation,<br><br />
(e) American Association of State Highway and Transportation Officials<br />
(AASHTO),<br><br />
(f) European Standards (ES).<br><br />
<br />
Table 5.1 describes the standards codes of practise and relevant area for<br />
application in construction works.<br />
<br />
[[File:V2Table5.1.JPG|536px|link=Chapter_Five:_Design_Standards_and_Specifications]]<br />
[[File:V2Table5.1b.JPG|536px|link=Chapter_Five:_Design_Standards_and_Specifications]]<br />
<br />
==SPECIFICATIONS ==<br />
Specification is a detailed description of how work is to be performed or<br />
requirements to be achieved, dimensions to be met, materials to be used,<br />
standards to be followed and tests to be carried for the product to meet<br />
acceptance criteria.<br />
Specifications are normally drafted by the client to suit the need for a particular<br />
work. For the purpose of construction of water and sanitation projects standard<br />
specifications have been prepared for various woks as follows:<br><br />
(a) Standard Specifications for Civil Works,<br><br />
(b) Standard Specifications for Electrical works,<br><br />
(c) Standard Specifications for Mechanical works and<br><br />
(d) General Specifications.<br><br />
These documents can be downloaded from the Ministry’s Website and customized<br />
to fit the needs of particular works.<br />
<br />
==MATERIALS ==<br />
===Building Materials ===<br />
Building material is any material used for construction purposes such as<br />
materials for structures. Wood, cement, aggregates, metals,sand, bricks, concrete,<br />
clay. These are the most common types of building material used in construction.<br />
The choice of these materials is based on their quality and cost effectiveness for<br />
building projects.<br />
<br />
===Materials Testing ===<br />
Before a material is to be used for construction work, it is imperative to conduct<br />
appropriate tests as per applicable standards. The following are the minimum<br />
tests proposed to be conducted on various construction materials.<br />
<br />
'''Aggregates'''<br><br />
Test of aggregates explained below includes both fine and coarse aggregates.<br />
<br />
'''Flakiness indextest'''<br><br />
Flaky particles are those whose least dimension is 0.6 times lesser than the mean<br />
size. Thickness of these particles are comparatively smaller than the other two<br />
dimensions.<br />
<br />
Maximum allowable limit of the flaky particles in the mix is 30%. If it exceeds this<br />
value then the mix is considered unsuitable for construction purpose.<br />
<br />
Flakiness index is the percentage by weight of flaky particles in a sample. The<br />
flakiness index is calculated by expressing the weight of flaky particles as a<br />
percentage of the total weight of the sample , test procedure is as outlined in<br />
BS – 812 ,1995.<br />
<br />
'''Elongation index test'''<br><br />
Elongated particles are particles having length considerably larger than the other<br />
two dimensions, also one dimension is 1.8 times greater than the other two<br />
dimensions.<br />
<br />
Maximum allowable limit of the flaky particles in the mix is 30%. If it exceeds this<br />
value then the mix is considered unsuitable for construction purpose.<br />
<br />
Elongation index is the percentage by weight of elongated particles in a sample.<br />
The elongated Index is calculated by expressing the weight of elongated particles<br />
as a percentage of the total weight of the sample, test method is expalined in<br />
BS– 812,1995<br />
<br />
Flaky and elongated particles lower the workability of concrete mixes due to high<br />
ratio of surface area to volume. The presence of flaky and elongated particles<br />
also may cause inherent weakness in concrete with possibilities of breaking<br />
down under heavy loads.<br />
<br />
'''Abrasion (Los Angeles Abrasion Test)'''<br><br />
Abrasion test is the measure of aggregate toughness and abrasion resistance on<br />
crushing, degradation and disintegration. Tests for abrasion is conducted based<br />
on BS 812: Part 113: 1990.<br />
<br />
'''Organic impurities test'''<br><br />
Sand should be checked for the presence of organic impurities such as decayed<br />
vegetation, humus, and coal dust as these affect the quality of concrete. Test for<br />
organic impurities should be conducted as per. BS 812: Part 4: 1976.<br />
<br />
'''Crushing value (ACV) test'''<br />
Aggregate crushing value test on coarse aggregates is a relative measure of the<br />
resistance of an aggregate crushing under gradually applied compressive load.<br />
The method for the determination of Aggregate Crushing Value (ACV) is the Code:<br />
BS 812 Part 110.<br />
<br />
'''10% finer test'''<br><br />
The 10 per cent Fines Aggregate Crushing Value (10% FACT) is determined by<br />
measuring the load required to crush a prepared aggregate sample to give 10%<br />
material passing a specified sieve after crushing. The test procedure is outline in<br />
line with code BS 812: 1990 Part 111.<br />
<br />
'''Impact resistance value (AIC) test'''<br><br />
The aggregate impact resistance value is a measure of resistance to sudden impact<br />
or shock. This value may differ from resistance to gradually applied compressive<br />
load. The procedure of Aggregate impact resistance value is provided in code BS<br />
812 : Part 112 : 1990.<br />
<br />
'''Grading–sieve analysis test'''<br><br />
This is the classification of a coarse-grained soil based on the different particle<br />
sizes it contains. This aspect is important as it indicates the compressibility<br />
properties, shear strength and hydraulic conductivity. The standard gradation<br />
and sieve analysis test is provided under: BS 812: Section 103.1: Sieve Analysis of<br />
Fine and Coarse Aggregates.<br />
<br />
'''Absorption test'''<br><br />
Water absorption is the measure of the porosity of an aggregate. It gives an<br />
indication of the strength of aggregates. When more water is absorbed, the<br />
aggregates is more porous in nature and generally considered unsuitable unless<br />
found to be acceptable based on strength, impact and hardness tests. The<br />
standard method for Testing aggregates to water absorption test is according<br />
toBS 812-120:1989.<br />
<br />
'''Specific gravity test'''<br><br />
The specific gravity of an aggregate is the ratio of its mass to that of an equal<br />
volume of distilled water at a specified temperature. The standard method for<br />
Testing aggregates to determine the density is BS 812 : Part 2: 1995.<br />
<br />
'''Chemical content (pH, chloride and sulphate) in aggregates test'''<br><br />
This test aims at establishing the permissible levels of chlorides and sulfates in<br />
aggregate. Theigh levels of chemicals may result in deterioration of concrete<br />
by corrosion of steel reinforcement.Corrosion of steel affects serviceability and<br />
strength of concrete structures. The test to determine the content of chemicals<br />
in aggregates is conducted as perBS 812-Part 117 & 118:1988.<br />
<br />
===Water ===<br />
'''Impurities test'''<br><br />
Water for washing aggregates and for mixing concrete shall be in accordance with<br />
DIN 4030 and DIN 1045 and shall be clean and free from objectionable organic<br />
matter, alkali, salts and other impurities.<br />
<br />
'''Chemical content (chloride, PH values, sulphate) in water'''<br><br />
Samples of water being used or which is proposed for use for mixing concrete<br />
shall undergo testing for quality to determine the concentration of sulphates and<br />
chlorides, which shall be such that the concrete mix as a whole complies with the<br />
specified limit for salt content. Chemical content in water may be determined<br />
through procedure explained in the code APHA 21st:2005/ICP OES.<br />
<br />
===Cement ===<br />
'''Setting time test'''<br><br />
The settling time is the time required for cement to convert from a plastic paste<br />
to a non-plastic and rigid mass. The cement settling time is determined through<br />
procedure explained in the AASHTO T 131 and ASTM C 191: Time of Setting of<br />
Hydraulic Cement.<br />
<br />
'''Compressive strength test'''<br><br />
The compressive strength of cement is the measure of the strength it provides to<br />
the mix after it has hardened. The test enables the identification of the quantity<br />
of cement required and how much strength it will provide. The compressive<br />
strength of cement is the basic data needed for concrete mix design. Cement<br />
is basically identified by its compressive strength as grade 53 grade, 43 grade,<br />
33 grade of cement. The test procedure is as per code of practice BS EN 196-<br />
1:2005.<br />
<br />
===Concrete Works ===<br />
Tests conducted for concrete includes:<br />
<br />
'''Slump test'''<br><br />
Concrete slump test or slump cone test is done to determine the workability or<br />
consistency of concrete mix prepared at the laboratory or the construction site<br />
during progress of the work. Concrete slump tests should be carried out batch to<br />
batch to check the uniform quality of concrete during construction.The slump is<br />
carried out as per the procedures mentioned in ASTM C143 in the United States,<br />
and EN 12350-2 in Europe.<br />
<br />
'''Compressive strenght test'''<br><br />
Compressive strength of concrete is the ability of material or structure to carry<br />
the loads on its surface without any crack or deflection. The standard test method<br />
for Compressive Strength of Cylindrical Concrete Specimens is carried out by<br />
procedure as stated in American Society for Testing Materials ASTM C39/C39M.<br />
<br />
'''Concrete voids test'''<br><br />
This test method is related to the susceptibility of the cement paste portion of the<br />
concrete to damage by freezing and thawing. The test estimates the likelihood<br />
of damage of concrete due to cyclic freezing and thawing. The parameters of the<br />
air-void system of hardened concrete determined by the procedures described<br />
in the code AASHTO T 269.<br />
<br />
===Steel ===<br />
'''Tensile strength'''<br />
The tensile strength of steel is the measure of maximum amount of stress that can<br />
be taken before failure. Tensile strength should be conducted as per standards<br />
methods as provided in code of practise DIN 15018.<br />
<br />
===Other Materials ===<br />
Testing for materials used in construction such as sands, bricks/blocks, etc.<br />
should be done according to the recommended standards specified in volume I<br />
of DCOM or as may be recommended for a specific project.<br />
<br />
Previous Page: [[Chapter_Four:_Off-Site_Sanitation_Systems|Chapter_Four:_Off-Site_Sanitation_Systems]] << >> Next Page: [[Chapter_Six:_Stakeholder%27s_Participation_in_Design_of_Sanitation_Projects|Chapter_Six:_Stakeholder%27s_Participation_in_Design_of_Sanitation_Projects]]<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_Five:_Design_Standards_and_Specifications:_Design_Standards_and_SpecificationsChapter Five: Design Standards and Specifications: Design Standards and Specifications2022-07-21T05:47:13Z<p>Juma: /* 5.3.7 Other Materials */</p>
<hr />
<div>=Chapter Five: Design Standards and Specifications=<br />
== 5.1 DESIGN STANDARDS ==<br />
<div style='text-align: justify'><br />
A Standard is the limit of a measure of quality of a product prepared for judgement<br />
and compliance by an authoritative agency, professional or a recognized<br />
body. According to (Business Dictionary, 2020) Standards can be classified as:<br />
Government or statutory agency standards and specifications enforced by law,<br />
<br />
Proprietary standards developed by a firm or organization and placed in public<br />
domain to encourage widespread use, and<br />
<br />
Voluntary standards established through consultation and consensus and<br />
available for use by any person, organization, or industry. Once established,<br />
standards (like bureaucracies) are very difficult to change or dislodge. Standards<br />
that apply for Tanzania water projects will be from the Tanzania Bureau of<br />
Standards, and for construction works, British standards shall be used.<br />
<br />
A list of institutions whose standards are recommended for use in water supply<br />
and sanitation projects design include the following:<br><br />
(a) Tanzania Bureau of Standards,<br><br />
(b) British Standards (BS),<br><br />
(c) American Society for Testing and Materials (ASTM)<br><br />
(d) Deutsches Institut für Normung (DIN); German institute for standardisation,<br><br />
(e) American Association of State Highway and Transportation Officials<br />
(AASHTO),<br><br />
(f) European Standards (ES).<br><br />
<br />
Table 5.1 describes the standards codes of practise and relevant area for<br />
application in construction works.<br />
<br />
[[File:V2Table5.1.JPG|536px|link=Chapter_Five:_Design_Standards_and_Specifications]]<br />
[[File:V2Table5.1b.JPG|536px|link=Chapter_Five:_Design_Standards_and_Specifications]]<br />
<br />
== 5.2 SPECIFICATIONS ==<br />
Specification is a detailed description of how work is to be performed or<br />
requirements to be achieved, dimensions to be met, materials to be used,<br />
standards to be followed and tests to be carried for the product to meet<br />
acceptance criteria.<br />
Specifications are normally drafted by the client to suit the need for a particular<br />
work. For the purpose of construction of water and sanitation projects standard<br />
specifications have been prepared for various woks as follows:<br><br />
(a) Standard Specifications for Civil Works,<br><br />
(b) Standard Specifications for Electrical works,<br><br />
(c) Standard Specifications for Mechanical works and<br><br />
(d) General Specifications.<br><br />
These documents can be downloaded from the Ministry’s Website and customized<br />
to fit the needs of particular works.<br />
<br />
== 5.3 MATERIALS ==<br />
=== 5.3.1 Building Materials ===<br />
Building material is any material used for construction purposes such as<br />
materials for structures. Wood, cement, aggregates, metals,sand, bricks, concrete,<br />
clay. These are the most common types of building material used in construction.<br />
The choice of these materials is based on their quality and cost effectiveness for<br />
building projects.<br />
<br />
=== 5.3.2 Materials Testing ===<br />
Before a material is to be used for construction work, it is imperative to conduct<br />
appropriate tests as per applicable standards. The following are the minimum<br />
tests proposed to be conducted on various construction materials.<br />
<br />
'''Aggregates'''<br><br />
Test of aggregates explained below includes both fine and coarse aggregates.<br />
<br />
'''Flakiness indextest'''<br><br />
Flaky particles are those whose least dimension is 0.6 times lesser than the mean<br />
size. Thickness of these particles are comparatively smaller than the other two<br />
dimensions.<br />
<br />
Maximum allowable limit of the flaky particles in the mix is 30%. If it exceeds this<br />
value then the mix is considered unsuitable for construction purpose.<br />
<br />
Flakiness index is the percentage by weight of flaky particles in a sample. The<br />
flakiness index is calculated by expressing the weight of flaky particles as a<br />
percentage of the total weight of the sample , test procedure is as outlined in<br />
BS – 812 ,1995.<br />
<br />
'''Elongation index test'''<br><br />
Elongated particles are particles having length considerably larger than the other<br />
two dimensions, also one dimension is 1.8 times greater than the other two<br />
dimensions.<br />
<br />
Maximum allowable limit of the flaky particles in the mix is 30%. If it exceeds this<br />
value then the mix is considered unsuitable for construction purpose.<br />
<br />
Elongation index is the percentage by weight of elongated particles in a sample.<br />
The elongated Index is calculated by expressing the weight of elongated particles<br />
as a percentage of the total weight of the sample, test method is expalined in<br />
BS– 812,1995<br />
<br />
Flaky and elongated particles lower the workability of concrete mixes due to high<br />
ratio of surface area to volume. The presence of flaky and elongated particles<br />
also may cause inherent weakness in concrete with possibilities of breaking<br />
down under heavy loads.<br />
<br />
'''Abrasion (Los Angeles Abrasion Test)'''<br><br />
Abrasion test is the measure of aggregate toughness and abrasion resistance on<br />
crushing, degradation and disintegration. Tests for abrasion is conducted based<br />
on BS 812: Part 113: 1990.<br />
<br />
'''Organic impurities test'''<br><br />
Sand should be checked for the presence of organic impurities such as decayed<br />
vegetation, humus, and coal dust as these affect the quality of concrete. Test for<br />
organic impurities should be conducted as per. BS 812: Part 4: 1976.<br />
<br />
'''Crushing value (ACV) test'''<br />
Aggregate crushing value test on coarse aggregates is a relative measure of the<br />
resistance of an aggregate crushing under gradually applied compressive load.<br />
The method for the determination of Aggregate Crushing Value (ACV) is the Code:<br />
BS 812 Part 110.<br />
<br />
'''10% finer test'''<br><br />
The 10 per cent Fines Aggregate Crushing Value (10% FACT) is determined by<br />
measuring the load required to crush a prepared aggregate sample to give 10%<br />
material passing a specified sieve after crushing. The test procedure is outline in<br />
line with code BS 812: 1990 Part 111.<br />
<br />
'''Impact resistance value (AIC) test'''<br><br />
The aggregate impact resistance value is a measure of resistance to sudden impact<br />
or shock. This value may differ from resistance to gradually applied compressive<br />
load. The procedure of Aggregate impact resistance value is provided in code BS<br />
812 : Part 112 : 1990.<br />
<br />
'''Grading–sieve analysis test'''<br><br />
This is the classification of a coarse-grained soil based on the different particle<br />
sizes it contains. This aspect is important as it indicates the compressibility<br />
properties, shear strength and hydraulic conductivity. The standard gradation<br />
and sieve analysis test is provided under: BS 812: Section 103.1: Sieve Analysis of<br />
Fine and Coarse Aggregates.<br />
<br />
'''Absorption test'''<br><br />
Water absorption is the measure of the porosity of an aggregate. It gives an<br />
indication of the strength of aggregates. When more water is absorbed, the<br />
aggregates is more porous in nature and generally considered unsuitable unless<br />
found to be acceptable based on strength, impact and hardness tests. The<br />
standard method for Testing aggregates to water absorption test is according<br />
toBS 812-120:1989.<br />
<br />
'''Specific gravity test'''<br><br />
The specific gravity of an aggregate is the ratio of its mass to that of an equal<br />
volume of distilled water at a specified temperature. The standard method for<br />
Testing aggregates to determine the density is BS 812 : Part 2: 1995.<br />
<br />
'''Chemical content (pH, chloride and sulphate) in aggregates test'''<br><br />
This test aims at establishing the permissible levels of chlorides and sulfates in<br />
aggregate. Theigh levels of chemicals may result in deterioration of concrete<br />
by corrosion of steel reinforcement.Corrosion of steel affects serviceability and<br />
strength of concrete structures. The test to determine the content of chemicals<br />
in aggregates is conducted as perBS 812-Part 117 & 118:1988.<br />
<br />
=== 5.3.3 Water ===<br />
'''Impurities test'''<br><br />
Water for washing aggregates and for mixing concrete shall be in accordance with<br />
DIN 4030 and DIN 1045 and shall be clean and free from objectionable organic<br />
matter, alkali, salts and other impurities.<br />
<br />
'''Chemical content (chloride, PH values, sulphate) in water'''<br><br />
Samples of water being used or which is proposed for use for mixing concrete<br />
shall undergo testing for quality to determine the concentration of sulphates and<br />
chlorides, which shall be such that the concrete mix as a whole complies with the<br />
specified limit for salt content. Chemical content in water may be determined<br />
through procedure explained in the code APHA 21st:2005/ICP OES.<br />
<br />
=== 5.3.4 Cement ===<br />
'''Setting time test'''<br><br />
The settling time is the time required for cement to convert from a plastic paste<br />
to a non-plastic and rigid mass. The cement settling time is determined through<br />
procedure explained in the AASHTO T 131 and ASTM C 191: Time of Setting of<br />
Hydraulic Cement.<br />
<br />
'''Compressive strength test'''<br><br />
The compressive strength of cement is the measure of the strength it provides to<br />
the mix after it has hardened. The test enables the identification of the quantity<br />
of cement required and how much strength it will provide. The compressive<br />
strength of cement is the basic data needed for concrete mix design. Cement<br />
is basically identified by its compressive strength as grade 53 grade, 43 grade,<br />
33 grade of cement. The test procedure is as per code of practice BS EN 196-<br />
1:2005.<br />
<br />
=== 5.3.5 Concrete Works ===<br />
Tests conducted for concrete includes:<br />
<br />
'''Slump test'''<br><br />
Concrete slump test or slump cone test is done to determine the workability or<br />
consistency of concrete mix prepared at the laboratory or the construction site<br />
during progress of the work. Concrete slump tests should be carried out batch to<br />
batch to check the uniform quality of concrete during construction.The slump is<br />
carried out as per the procedures mentioned in ASTM C143 in the United States,<br />
and EN 12350-2 in Europe.<br />
<br />
'''Compressive strenght test'''<br><br />
Compressive strength of concrete is the ability of material or structure to carry<br />
the loads on its surface without any crack or deflection. The standard test method<br />
for Compressive Strength of Cylindrical Concrete Specimens is carried out by<br />
procedure as stated in American Society for Testing Materials ASTM C39/C39M.<br />
<br />
'''Concrete voids test'''<br><br />
This test method is related to the susceptibility of the cement paste portion of the<br />
concrete to damage by freezing and thawing. The test estimates the likelihood<br />
of damage of concrete due to cyclic freezing and thawing. The parameters of the<br />
air-void system of hardened concrete determined by the procedures described<br />
in the code AASHTO T 269.<br />
<br />
=== 5.3.6 Steel ===<br />
'''Tensile strength'''<br />
The tensile strength of steel is the measure of maximum amount of stress that can<br />
be taken before failure. Tensile strength should be conducted as per standards<br />
methods as provided in code of practise DIN 15018.<br />
<br />
=== 5.3.7 Other Materials ===<br />
Testing for materials used in construction such as sands, bricks/blocks, etc.<br />
should be done according to the recommended standards specified in volume I<br />
of DCOM or as may be recommended for a specific project.<br />
</div><br />
Previous Page: [[Chapter_Four:_Off-Site_Sanitation_Systems|Chapter_Four:_Off-Site_Sanitation_Systems]] << >> Next Page: [[Chapter_Six:_Stakeholder%27s_Participation_in_Design_of_Sanitation_Projects|Chapter_Six:_Stakeholder%27s_Participation_in_Design_of_Sanitation_Projects]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Four:_Off-Site_Sanitation_Systems:Chapter_Four:_Off-Site_Sanitation_SystemsChapter Four: Off-Site Sanitation Systems:Chapter Four: Off-Site Sanitation Systems2022-07-21T05:42:02Z<p>Juma: </p>
<hr />
<div>=Chapter Four: Off-site Sanitation Systems=<br />
<div style="text-align:justify"><br />
Off-site sanitation refers to a sanitation system in which wastewater and excreta are collected and conveyed away from the plot where they are generated. An off-site sanitation system relies on a sewer technology (simplified sewer, solid free sewer or conventional sewer) for conveyance of excreta.<br />
<br />
==Decentralized Wastewater Treatment Systems (DEWATS)==<br />
Decentralized wastewater management systems (DEWATS) include all parts of a onsite-sanitation system. In comparison to centralized systems, these systems are located at or near the point of wastewater generation. DEWATS can be characterized and differentiated from centralized systems along the following lines.<br />
* Volume: Decentralized systems treat relatively small volumes of water (typically 1-1,000 m³/day),<br />
* Sewer type: Centralized systems typically use conventional gravity sewers, while decentralized systems typically use small-diameter gravity sewers, often employing intermediate settlers for solid-free sewers.<br />
<br />
==Components of DEWATS==<br />
The components of DEWATS are presented in the schematic layout shown in Figure 4.1<br><br />
[[File:Treatment_Flow_Sheet_for_Components_of_DEWATS.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.27: Treatment Flow Sheet for Components of DEWATS <br />
(Source: MoW, 2018)<br />
===Containment===<br />
Containment technologies collect and store wastewater at the user interface on-site. Containment technologies are usually applicable for low-cost, non-sewered sanitation (FS) systems as intermediate storage, but can also serve as pre-treatment modules for small-scale wastewater treatment systems. The main containment technology applicable for wastewater treatment technologies is a septic tank (see Figure 4 .28).<br><br />
<br />
[[File:The_Cross_Section_of_a_Septic.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br><br />
Figure 4.28: The Cross Section of a Septic Tank<br />
(Source: MoW, 2018)<br><br />
<br />
In the vast majority of situations, containment systems are already installed on-site but are often improperly designed, constructed and maintained, which poses severe environmental hazards. Apart from septic tanks providing some degree of pre-treatment, the effluent usually contains high concentrations of pollutants, which can carry severe public health and environmental burdens, especially in densely populated urban areas and in the vicinity of drinking water sources. Hence, proper sealing of containment options is crucial for environmental sanitation. Containment systems can also be implemented to buffer peak flows.<br />
<br />
===Design of Septic Tank===<br />
The capacity of septic tank depends on number of users and interval of sludge removal. Normally sludge should be removed every 2 years. The liquid capacity of the tank is taken as 130 litres to 70 litres per head. For small number of users 130 litres per head is sufficient.<br />
<br />
A septic tank is usually provided with brick walls in which cement mortar [not less than 20 cm (9 inch)] thick and the foundation floor is of cement concrete<br />
1:2:4. Both inside and outside faces of the wall and top of the floor are plastered with minimum thickness of 12mm thick cement mortar 1:3 mix.<br />
<br />
All inside corners of the septic tank are rounded. Water proofing agent (such as Impermo, Cem-seal or Accoproof, etc.) is added to the mortar at the rate of 2% of the cement weight. Water proofing agent is to be added in similar proportion in to the concrete also for making the floor of the tank.<br />
<br />
For proper convenience in collection and removal of the sludge, the floor of the septic tank is given a slope of 1:10 to 1:20 towards the inlet side. Which means that the floor of the outlet side will be on the higher elevation than the floor at the inlet side.<br />
====Dimensioning a Septic Tank====<br />
'''(A) Length, Width and Depth of Septic Tank'''<br><br />
Width = 750 mm (minimum)<br />
Length = 2 to 4 times width<br />
Depth = 1,000 to 1,300 mm. (min below water level) + 300 to 450 mm free board<br />
Maximum depth = 1,800 mm + 450 mm free board<br />
Capacity = 1 cubic metre (minimum)<br />
<br />
'''(B) Detention period'''<br><br />
Detention period of 24hrs (is mostly) considered in septic tank design. The rate of flow of effluent must be equal to the rate of flow of the influent.<br />
<br />
'''(C) Inlet and outlet pipes'''<br><br />
An elbow or T pipe of 100mm diameter is submerged to a depth of 250-600 mm below the liquid level. For the outlet pipe an elbow or T type of 100mm diameter pipe is submerged to a depth of 200-500 mm below the liquid level. Pipes may be of stone ware or asbestos or PVC.<br />
<br />
'''(D) Baffle Walls of the Septic Tank'''<br><br />
For small tanks, RCC hanging type scum baffle walls are provided in septic tanks. Baffle walls are provided near the inlet. It is optional near the outlet. The inlet baffle wall is placed at a distance of L/5 from the wall, where L is the length of the wall. The baffle wall is generally extended 150 mm above to scum level and 400-700 mm below it.<br />
<br />
Scum being light, generally floats at the water level in the tank. Thickness of the wall varies from 50 mm to 100 mm. For large tanks the lower portion has holes for flow of sludge.<br />
<br />
'''(E) Roofing Slab of the Septic Tank'''<br><br />
The top of the septic tank is covered with a RCC slab of thickness of 75-100 mm depending upon the size of the tank. Circular manholes of 500mm clear diameter are provided for inspection and desludging. In case of rectangular opening clear size is kept as 600 x 450 mm.<br />
<br />
'''(F) Ventilation Pipe'''<br><br />
For outlet of foul gases and ventilation purpose cast iron or asbestos pipe of 50-100 mm diameter is provided which should extend 2m (minimum) above ground level. Top of the ventilation pipe is provided with a mosquito proof wire mesh or cowl.<br />
<br />
===Conveyance===<br />
Technologies presented in this section are sewer-based technologies, using water from waterborne toilets as a conveying medium.<br />
====Simplified Sewer====<br />
A simplified sewer describes a sewerage network that is constructed using smaller diameter pipes laid at a shallower depth and at a flatter gradient than conventional sewers (Figure 4.3).<br><br />
<br />
[[File:Sketch_of_a_Simplified_Sewer.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br><br />
Figure 4.29: Sketch of a Simplified Sewer<br />
(Source: MoW, 2018)<br />
<br />
This sewer system generally does not apply pumping. For this reason, a simplified sewer allows for a more flexible design at lower cost. Simplified sewers can be installed in almost all types of settlements and are especially appropriate for densely populated urban areas where space for on-site technologies is limited. The sewers should be considered as an option where there is significant population density (about 150 inhabitants per hectare) and a reliable water supply system (at least 60 L/capita/day).<br />
=====Design considerations for simplified sewers=====<br />
In contrast to conventional sewers that are designed to ensure a minimum self-cleansing velocity, the design of simplified sewers is based on a minimum tractive tension of 1 N/m2 (1 Pa) at peak flow. The minimum peak flow should be 1.5 L/s and a minimum sewer diameter of 100 mm is required. A gradient of 0.5% is usually sufficient. For example, a 100 mm sewer laid at a gradient of 1m in 200 m will serve around 2,800 users with a wastewater flow of 60 L/person/day. PVC pipes are recommended for use. The depth at which they should be laid depends mainly on the amount of traffic. Below sidewalks, soil covers of 40 to 65 cm are typical. The simplified design can also be applied to sewer mains. They can also be laid at a shallow depth, provided that they are placed away from traffic.<br />
<br />
Expensive manholes are normally not needed. At each junction or change in direction, simple inspection chambers (or cleanouts) are provided as can be seen on Figure 4 .29. Inspection boxes are also used at each house connection. Where kitchen grey water contains an appreciable amount of oil and grease. The installation of grease traps is recommended to prevent clogging. Grey water should be discharged into the sewer to ensure adequate hydraulic loading, but storm water connections should be discouraged. In practice it is difficult to exclude all storm water flows, especially where there is no alternative for storm drainage. The design of sewers (and treatment plants) should, therefore, take into account the extra flow that may result from storm water inflows.<br />
=====Design Procedures for Simplified Sewers=====<br />
'''Step 1. Estimation of the wastewater flow'''<br><br />
'''Daily peak flows'''<br><br />
The value of the wastewater flow used for sewer design is the daily peak flow. This can be estimated as follows:<br><br />
<br />
[[File:Equation1.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
where:<br />
q = daily peak flow, l/s<br />
k<sub>1</sub> = peak factor (=daily peak flow divided by average daily flow)<br />
k<sub>2</sub> = return factor (=wastewater flow divided by water consumption)<br />
P = population served by length of sewer under consideration<br />
w = average water consumption, litres per person per day and 86,400 is the number of seconds in a day.<br />
<br />
A suitable design value for k<sub>1</sub> for simplified sewerage is 1.8 and k<sub>2</sub> may be taken as 0.85.<br />
Thus, equation 4.1 becomes:<br><br />
[[File:Equation2.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Variations in the value of k2 have a much lower impact on design, except in middle and high-income areas where a large proportion of water consumption is also for lawn-watering and car-washing. In peri-urban areas in Brazil a k2 value of 0.85 has been used successfully, although other counties use a value of 0.65, even in low income areas and without any reported operational problems (Luduvice, 2000). However higher values may be more appropriate elsewhere–for example, in areas where the water supply is based on a system of public standpipes, values up to 0.95 may be used.<br />
<br />
'''Step 2. Sizing of a simplified sewer'''<br><br />
The flow in simplified sewers is always assumed to be an open channel flow–that is to say, there is always some free space above the flow of wastewater in the sewer. The hydraulic design of simplified sewers requires knowledge of the area of flow and the hydraulic radius. Both these parameters vary with the depth of flow. <br />
<br />
From Figure 4 .30 shows the trigonometric relationships which can be derived for the following parameters:<br />
<br />
(i) The area of flow(a), expressed in m2;<br><br />
(ii) The wetted perimeter(p), m;<br><br />
(iii) The hydraulic radius(r), m; and<br><br />
(iv) The breadth of flow (b), m.<br />
<br />
The hydraulic radius (sometimes called the hydraulic mean depth) is the area of flow divided by the wetted perimeter.<br />
<br />
[[File:Definition_of_Parameters_for_Open_Channel_Flow_in_a_Circular_Sewer.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Figure 4.30: Definition of Parameters for Open Channel Flow in a Circular Sewer<br />
(Source: Mara, 1996)<br />
<br />
If the angle of flow is measured in degrees, it must be converted to radians by multiplying by (2π/360), since 360o equals 2π radians.<br />
<br />
The ratio d/D is termed the proportional depth of flow (which is dimensionless). In simplified sewerage systems the usual limits for d/D are as follows:<br />
<br />
0.2 <d/D < 0.8<br />
<br />
The lower limit ensures that there is sufficient velocity of flow to prevent solids deposition in the initial part of the design period, and the upper limit provides for sufficient ventilation at the end of the design period. The equations are as follows:<br />
<br />
Angle of flow, θ = 2 cos<sup>-1</sup> [1 – 2 (d/D)] .....................................................................(4.3)<br />
<br />
Area of flow, a = D<sup>2</sup> [(θ – sin θ) / 8] ..........................................................................(4.4)<br />
<br />
Wetted perimeter, p = θ D/2 .....................................................................................(4.5)<br />
<br />
Hydraulic radius (= a/p), r = (D/4) [1 – ((sin θ) /θ)]....................................................(4.6)<br />
<br />
Breadth of flow, b = D sin (θ/2), ................................................................................(4.7)<br />
<br />
When d = D (that is, when the sewer is flowing just flow), then a = A = π D2/4; p = P = πD and r = R = D/4.<br />
The following equations for ‘’a’’ and ‘’r’’ are used in designing simplified sewers:<br><br />
a =k<sub>a</sub>D .......................................................................................................................(4.8)<br><br />
r = k<sub>r</sub>D .......................................................................................................................(4.9)<br>.<br />
The coefficients k<sub>a</sub> and k<sub>r</sub> are given from equations 4.8 and 4.9 as:<br><br />
[[File:Equation3.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
'''Step 3. Velocity of flow'''<br />
In 1889, Robert Manning (an Irish civil engineer, 1816-1897) presented his formula relating to the velocity of flow in a sewer to the sewer gradient and the hydraulic radius (Manning, 1890). The formula is commonly, but improperly, known as the Manning equation; as pointed out by Williams (1970) and Chanson (1999). it should be known as the Gauckler-Manning equation since Philippe Gauckler (a French civil engineer,1826-1905) published the same equation 4.12 years earlier (Gauckler, 1867 and1868).<br />
<br />
<br />
The Gauckler-Manning equation is <br><br />
[[File:Equation4.12.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Where <br />
V = velocity of flow at d/D, m/s<br />
n = Ganguillet-Kutter roughness coefficient, dimensionless <br />
r = hydraulic radius at d/D, m<br />
i = sewer gradient, m/m (i.e. dimensionless)<br><br />
Since flow = area × velocity<br />
<br />
[[File:Equation4.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Where q = flow in sewer at d/D, m3/s <br />
Using equations 4.8 and 4.9, equation 4.14 becomes:<br><br />
[[File:Equation5.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
The usual design value of the Ganguillet - Kutter roughness coefficient, n is 0.013. This value is used for any relatively smooth sewer pipe material (concrete, PVC or vitrified clay) as it depends not so much on the roughness of the material itself, but on the roughness of the bacterial slime layer which grows on the sewer wall.<br />
<br />
====Solids-free Sewer====<br />
Solids-free sewers are also referred to as settled, small-bore, variable-grade gravity, or septic tank effluent gravity sewers. A precondition for solids-free sewers is efficient primary treatment at the household level. Figure 4 .31 presents section of solids free sewers.<br />
[[File:Section_of_Solids_Free_Sewers.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Figure 4.31: Section of Solids Free Sewers (Source: Tilleyet al., 2014)<br><br />
An interceptor, typically a single-chamber septic tank, captures settleable particles that could clog small pipes. The solids interceptor also functions to attenuate peak discharges. Because there is little risk of depositions and clogging, solids-free sewers do not have to be self-cleansing, i.e., no minimum flow velocity or tractive tension is needed. They require few inspection points, can have inflective gradients (i.e., negative slopes) and follow the topography. When the sewer roughly follows the ground contours, the flow is allowed to vary between open channel and pressure (full-bore) flow.<br />
=====Design Considerations for Solid Free Sewers=====<br />
If the interceptors are correctly designed and operated, this type of sewer does not require self-cleansing velocities or minimum slopes. Even inflective gradients are possible, as long as the downstream end of the sewer is lower than the upstream end. Solids-free sewers do not have to be installed on a uniform gradient with a straight alignment between inspection points. The alignment may curve to avoid obstacles, allowing for greater construction tolerance. At high points in sections with pressure flow, the pipes must be ventilated. A minimum diameter of 75 mm is required to facilitate cleaning. <br />
<br />
Expensive manholes are not needed because access for mechanical cleaning equipment is not necessary. Cleanouts or flushing points are sufficient and are installed at upstream ends, high points, intersections, or major changes in direction or pipe size. Compared to manholes, cleanouts can be more tightly sealed to prevent storm water from entering. Storm water must be excluded as it could exceed pipe capacity and lead to blockages due to grit depositions. Ideally, there should not be any storm- and groundwater in the sewers, but, in practice, some imperfectly sealed pipe joints must be expected. Estimates of groundwater infiltration and storm water inflow must, therefore, be made when designing the system. The use of PVC pipes can minimize the risk of leakages.<br />
=====Design Steps for Solids Free Sewers=====<br />
A similar equation to simplified sewers can be used to design the size of a sewer in case of very large flow rate of the wastewater. The design of solids free sewers follows the following steps:<br><br />
'''Step 1. Estimation of the waste water flow'''<br><br />
'''Daily peak flows'''<br><br />
The value of the wastewater flow used for sewer design is the daily peak flow. This can be estimated as follows:<br />
[[File:Equation7.15.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
where<br />
<br />
q = daily peak flow, l/s<br />
k<sub>1</sub> = peak factor (=daily peak flow divided by average daily flow)<br />
k<sub>2</sub> = return factor (=wastewater flow divided by water consumption)<br />
P = population served by length of sewer under consideration<br />
w = average water consumption, litres per person per day and<br />
86,400 is the number of seconds in a day<br />
<br />
A suitable design value for k<sub>1</sub> for simplified sewerage is 1.8 and k<sub>2</sub> may be taken as 0.85.<br />
<br />
Thus, equation 4.1 becomes;<br />
<br />
q = 1.8 × 10<sup>-5</sup>P………………...........................................................................…...…(4.16)<br><br />
Variations in the value of k<sub>2</sub> have a much lower impact on design, except in middle and high-income areas where a large proportion of water consumption is used for lawn-watering and car-washing. In peri-urban areas in Brazil a k<sub>2</sub> value of 0.85 has been used successfully, although other countries use a value of 0.65, even in low income areas and without any reported operational problems (Luduvice, 2,000). However higher values may be more appropriate elsewhere – for example, in areas where the water supply is based on a system of public standpipes, values up to 0.95 may be used.<br />
<br />
'''Step 2: Sizing of conventional gravity sewers'''<br><br />
The flow in simplified sewers is always assumed to be an open channel flow–that is to say, there is always some free space above the flow of wastewater in the sewer. The hydraulic design of conventional gravity sewers requires knowledge of the area of flow and the hydraulic radius. Both these parameters vary with the depth of flow. From figure below trigonometric relationships can be derived for the following parameters:<br><br />
(a) The area of flow (a), expressed in m2;<br><br />
(b) The wetted perimeter(p), m;<br><br />
(c) The hydraulic radius (r), m; and<br><br />
(d) The breadth of flow (b), m.<br><br />
The hydraulic radius (sometimes called the hydraulic mean depth) is the area of flow divided by the wetted perimeter.<br><br />
[[File:Definition_of_Parameters_for_Open_Channel_Flow_in_a_Circular_Sewer.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.32: Definition of Parameters for Open Channel Flow in a Circular Sewer<br />
(Source: Mara, 1996)<br><br />
If the angle of flow is measured in degrees, then it must be converted to radians by multiplying by (2π/360), since 360<sup>o</sup> equals 2π radians. The ratio d/D is termed the proportional depth of flow (which is dimensionless). In simplified sewerage pipes the usual limits for d/D are as follows:<br />
0.2 <d/D < 0.8<br />
<br />
The lower limit ensures that there is sufficient velocity of flow to prevent solids deposition in the initial part of the design period, and the upper limit provides for sufficient ventilation at the end of the design period. The equations are as follows:<br />
<br />
Angle of flow, θ = 2 cos<sup>-1</sup> [1 – 2 (d/D)]………………….....…………..…......(4.17)<br />
<br />
Area of flow, a = D<sup>2</sup> [(θ – sin θ) / 8].....……..………………………...……….(4.18)<br />
<br />
Wetted perimeter, p = θ D/2.........……………………………...…..................(4.19)<br />
<br />
Hydraulic radius (= a/p), r = (D/4) [1 – ((sin θ) /θ)].....………….………........(4.20)<br />
<br />
Breadth of flow, b = D sin (θ/2)......………………………………..……..……..(4.21)<br />
<br />
When d = D (that is, when the sewer is flowing just flow), then a = A = π D2/4; p = P = πD and r = R = D/4.<br />
<br />
The following equations for ‘’a’’ and ‘’r’’ are used in designing simplified sewers:<br />
<br />
a = k<sub>a</sub>D<sup>2</sup> ………………………………………………………………….........................(4.22)<br><br />
<br />
r = k<sub>r</sub>D……………………………….………………………..…………..........................(4.23)<br />
<br />
The coefficients k<sub>a</sub> and k<sub>r</sub> are given from equations 4.22 and 4.23 as:<br><br />
<br />
[[File:Equation8.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
====Conventional Gravity Sewer====<br />
Conventional gravity sewers are large networks of underground pipes that convey backwater, grey water and, in many cases, storm water from individual households to a (semi-)centralised treatment facility using gravity (and pumps when necessary). Schematic layout sketch of a conventional gravity sewer is presented in Figure 4 .33.<br><br />
[[File:Schematic_Layout_Sketch_of_a_Conventional_Gravity_Sewer.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.33: Schematic Layout Sketch of a Conventional Gravity Sewer <br />
(Source: MoW, 2018)<br><br />
Since they can be designed to carry large volumes, conventional gravity sewers are very appropriate to transport wastewater to a (semi-) centralised treatment facility. The construction of conventional sewer systems in dense, urban areas is complicated because it disrupts urban activities and traffic. Conventional gravity sewers are expensive to build and a professional management system must be in place, as the installation of a sewer line is disruptive and requires extensive coordination between related authorities, construction companies and property owners.<br />
=====Design Considerations=====<br />
Conventional gravity sewers normally do not require on-site pre-treatment, primary treatment or storage of the household wastewater before it is discharged. The sewer must be designed, however, such that it maintains self-cleansing velocity (i.e., a flow that will not allow particles to accumulate). For typical sewer diameter s, a minimum velocity of 0.6 to 0.7 m/s during peak dry weather conditions should be adopted. A constant downhill gradient must be guaranteed along the length of the sewer to maintain self-cleansing flows, which can require deep excavations. When a downhill grade cannot be maintained, a manhole must be installed. Primary sewers are laid beneath roads, at depths of 1.5 to 3 m to avoid damages caused by traffic loads. The depth also depends on the groundwater table, the lowest point to be served (e.g., a basement) and the topography. The selection of the pipe diameter depends on the projected average and peak flows. Commonly used materials are concrete, PVC, and ductile or cast iron pipes.<br />
<br />
Access manholes are placed at set intervals above the sewer, at pipe intersections and at changes in pipeline direction (vertically and horizontally). Manholes should be designed such that they do not become a source of storm water inflow or groundwater infiltration.<br />
=====Design Steps for Conventional Gravity Sewers=====<br />
The design steps for the conventional gravity sewers should be the same as those for simplified and solids free sewers. In addition, the design for the system should allow for weir for discharge measurements. Please refer to these sections for the design of conventional gravity sewers. For conventional gravity sewer lines, the following should be observed on the pipe sizes to be applied because of potential abuse by users by introducing solids into the sewer lines:<br />
<br />
(a) Any new sewer connection should use plastic pipes of diameter not less than 150 mm or (6") for further extensions (limited number of connected customers not more than 5 in number for domestic use only).<br />
(b) Lateral sewers, incorporating more than 5 sewer connections and that may need further extensions in future should involve plastic pipes of diameter not less than 200 mm or (8").<br />
(c) Commercial and public sewer connections at lodges, hotels, business centres, institutions, industries, apartments and others should use plastic pipes of not less than 200 mm (8"). <br />
(d) All main sewers should start with pipes not less than 200 mm (8").<br />
<br />
Note that: The previously designed plastic pipes of more than 500 mm were discouraged to provide room for concrete pipes from that diameter. From field practical experience concrete pipes have higher roughness than plastic pipes and are easily corroded by sewage. Plastic pipes of various diameters and appurtenances for application in sewerage lines are currently manufactured and available in Tanzania.<br />
===Wastewater Treatment===<br />
Wastewater treatment is a process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with minimum impact on the environment, or directly reused (https://en.wikipedia.org/wiki/Wastewater_treatment). The typical wastewater treatment flow sheet is presented Figure 4 .34.<br><br />
<br />
[[File:A_Typical_Flow_Sheet_for_a_Wastewater_Treatment_Plant_.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems#A Typical Flow Sheet for a Wastewater Treatment Plant]]<br><br />
Figure 4.34: A Typical Flow Sheet for a Wastewater Treatment Plant <br />
(Source: MoW, 2018)<br><br />
<br />
===Preliminary Treatment===<br />
=====Grease Trap=====<br />
Fats, oils and grease are a major component of human food stuffs. The term 'grease' is commonly used and sometimes includes the fats, oils, waxes, and other related constituents found in waste water. Greases are solid products (as long as the temperature is sufficiently low) of animal or vegetable origin present in municipal waste water and in some industrial waste waters. <br />
<br />
At municipal and industrial wastewater treatment plants where large quantities of grease and fat are to be removed, both aided and induced flotation systems are used to separate the grease and fat from the sewage. These systems involve the use of gas (normally air) bubbles to promote the separation of fat and grease particles from the liquid medium in which they are carried. The rising velocity of the gas bubble determines the efficiency of removal of grease and fat. shows section view of a grease trap. The rising velocity of the gas bubble This is sometimes calculated from Stokes equation which is as follows:<br />
<br />
Stokes Equation<br />
<br />
[[File:Equation9.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems#Equation9]]<br><br />
Where: <br><br />
V = the rising velocity; <br><br />
d = diameter of air bubbles; <br><br />
P<sub>g</sub> = density of the gas; <br><br />
P<sub>i</sub>= density of the liquid:<br><br />
n= absolute viscosity; and <br><br />
g = gravitational acceleration<br><br />
[[File:Section_View_of_a_Grease_Trap.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems#Grease_Trap]]<br><br />
Figure 4.35: Section View of a Grease Trap (Source: Tilley et al., 2014)<br />
<br />
====Design Considerations for Grease Trap====<br />
The minimum requirements for grease trap design are:<br><br />
'''(a)''' Provision of sufficient capacity to slowdown the passing wastewater, giving greasy waste, the opportunity to separate out. Check the size of an existing grease trap or determine the approximate size of a new grease trap.<br><br />
<br />
'''(b)''' The length of the trap should be equal to between 1.3 and 2.0 times the total depth. Note that usually, the grease trap contents occupy 2/3 of the total depth; the top 1/3 of the trap is head space. Do not include wall and cover thickness in the length and depth measurements if the grease trap is built of concrete. <br><br />
<br />
'''(c)''' The surface area of the trap (the length times the width in square millimetres) should be equal to between 1,000 and 2,000 times the total depth measured in millimetres. Again, do not include wall and cover thickness in measuring a concrete trap. <br><br />
<br />
'''(d)''' Prevent wastewater entering the grease trap from mixing up the top greasy waste layer. A baffle should be present at the trap inlet to slow down the incoming wastewater and keep it separate from the top waste layer. The inlet pipe should end in a 90° downwards bend so that incoming wastewater enters the trap at least 100 mm below the water surface. The inlet pipe should not terminate above the liquid surface such that wastewater drops into the trap. <br><br />
<br />
'''(e)''' Allow access to the trap for maintenance so that all covers can be lifted and accumulated material removed from both the top and bottom of the trap. Except for very large grease traps, the total depth of liquid should never exceed 1200 mm. A sampling hole with an appropriate cover must also be provided if the opening for maintenance access does not also give access to the grease trap outlet. <br><br />
<br />
'''(f)''' Provide necessary safety features. All grease traps must be vented. Under-floor grease traps and grease traps with over 1000 litre capacity must be provided with a prominent sign to show location, to indicate both total and liquid depth, and the maximum allowable thickness of the greasy waste layer (30%).<br />
<br />
====Screens====<br />
Screening is the first unit operation used at wastewater treatment plants (WWTPs). Screening removes objects such as rags, paper, plastics, and metals to prevent damage and clogging of downstream equipment, piping, and appurtenances. Some modern wastewater treatment plants use both coarse screens and fine screens.<br />
<br />
'''(a) Coarse Screens '''<br><br />
Coarse screens remove large solids, rags, and debris from wastewater, and typically have openings of 6 mm (0.25 in) or larger. Types of coarse screens include mechanically and manually cleaned bar screens, including trash racks. Table 4.1 provide a description of wastewater screen types. <br />
<br />
'''Table 4.25: Description of Coarse Screens'''<br />
{| class="wikitable"<br />
|-<br />
! Screen Type !! Description<br />
|-<br />
| Trash rack||Designed to prevent logs, timbers, stumps, and other large debris from entering treatment processes.<br>Opening size: 38 to 150 mm <br />
|-<br />
| Manually cleaned bar screen || Designed to remove large solids, rags, and debris.<br>Opening size: 30 to 50 mm <br>Bars are set at 30 to 45 degrees from vertical to facilitate cleaning. Primarily used in older or smaller treatment facilities, or in bypass channels<br />
|-<br />
| Mechanically cleaned bar screen||Designed to remove large solids, rags, and debris. <br>Opening size: 6 to 38mm<br>Bars are set at 0 to 30 degrees from vertical. Almost always used in new installations because of a large number of advantages relative to other screens.<br />
|}<br><br />
<br />
'''(b) Fine Screens'''<br><br />
Fine screens are typically used to remove material that may create operation and maintenance problems in downstream processes, particularly in systems that lack primary treatment. Typical opening sizes for fine screens are 1.5 to 6 mm. Very fine screens with openings of 0.2 to 1.5 mm placed after coarse or fine screens can reduce suspended solids to levels near those achieved by primary clarification.<br />
<br />
'''(c) Screen Design Steps'''<br><br />
'''Step 1: Selection'''<br><br />
The specific screen to be selected will depend on the application. In general, the approach as set out in Table 4 .26is suggested.<br />
<br />
'''Table 4.26: Screen Selection'''<br />
{| class="wikitable"<br />
|-<br />
! Application !! Aperture !! Type<br />
|-<br />
| Large Pump houses || 50 - 15 mm || Trash rack<br> R.B.I.<br />
|-<br />
| Small Pump houses || 50 mm || Liftable cage <br>Bar screen<br />
|-<br />
| Small Wastewater Treatment Plants (Without Sludge Treatment) || 15 - 25 mm || Curved bar screen <br>Vertical bar screen<br>Inclined bar screen<br />
|-<br />
| Small Wastewater Treatment Plant (With Sludge Treatment) || 5 - 10 mm || Inclined bar screen<br> Vertical bar screen <br>Band screen<br />
|-<br />
| Medium Wastewater Treatment Plant (With Sludge Treatment) || 5 - 10 mm || Inclined bar screen<br> Vertical bar screen <br>Band screen <br>Screezer (V.D.S.) <br>Rotomat <br>Contra-shear<br />
|-<br />
| rowspan="2" | Large Wastewater Treatment Plants (With Sludge Treatment)<br />
| 15 - 50mm (Before Fine Screen) || Vertical bar screen<br />
|-<br />
| 5 - 10 mm<br />
|| Band screen <br>Drum screen <br>Cup screen.<br>Screezer (V.D.S.)<br>Rotomat.<br>Contra-shear<br />
|-<br />
| Overflows (Retain Screenings in Foul Flow) || 5 - 10 mm || Discreen <br>J&A Weir Mount<br />
|}<br />
(Source: Clay et al., 1996)<br><br />
<br />
'''(d) Design Factor for Screens'''<br><br />
The basic design of a bar screen should be such that the velocity through the screen would he sufficient for matter to attach itself to the screen without producing an excessive loss of head or complete clogging of the bars. At the same time, velocities in the channel upstream should be sufficient to avoid deposition of solids. In all cases the shape of the bar should be tapered from the upstream side so that any solids which pass the upstream face of the screen cannot be jammed in the screen, thereby causing a trip out of the raking mechanism. Table 4 .27 gives the design factors for bar screens:<br><br />
'''Table 4.27: Bar Screen Design Factors'''<br />
{| class="wikitable"<br />
|-<br />
! Item!! Manually cleaned !! Mechanically cleaned<br />
|-<br />
| Bar Size: Width (mm) <br>Depth (mm) || 5 - 15 <br>25 - 80 || 5- 15<br>25 - 80<br />
|-<br />
| Aperture (mm) || 20 - 50 || 5 - 80<br />
|-<br />
| Slope to Flow (Deg) || 45<sup>0</sup> - 60<sup>0</sup> || 18<sup>0</sup> - 90<sup>0</sup><br />
|-<br />
| Velocity Through Screen (m/s) || 0.3 - 0.6 || 0.6 - 1.0 (Max. 1.4)<br />
|-<br />
|}<br />
(Source: Clay et al., 1996)<br><br />
The following equations may be used for standard bar screens to calculate the width of channel required and the head loss through the screen:<br />
<br />
Width of Channel, W can be calculated as follows;<br><br />
<br />
[[File:Equation10.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems#Equation9]]<br><br />
<br />
Where<br />
Q = Maximum Flow (m<sup>3</sup>Is) <br />
V = Velocity Through Screen (mis) <br />
v = Velocity in Upstream Channel (m/s)<br />
D = Depth of Flow (m) W = Width of Channel (m) <br />
S = % Screen Open Area. <br />
HL = Head Loss Through Screen (m) <br />
g = 9.81 m/s<sup>2</sup> (gravity). <br />
h = Head on Screen Upstream (m) <br />
A = Submerged Aperture Area (mm2) <br />
B = Bar Width (mm) <br />
ɵ = Angle of inclination of bars. <br />
C = Coefficient which should be checked with the manufacturer. <br />
ß= Bar Shape Factor.<br />
<br />
<br />
The values of bar shape factors for clean rack are summarised as presented in Table 4 .28.<br />
<br />
'''Table 4.28: Bar Shape Factor'''<br />
{| class="wikitable"<br />
|-<br />
! Bar type !! Bar shape factor<br />
|-<br />
| Sharp-edged rectangular || 2.42<br />
|-<br />
| Rectangular with semi- circular upstream face. || 1.83<br />
|-<br />
| Circular. || 1.79<br />
|-<br />
| Rectangular with semi- circular upstream and downstream faces. || 1.67<br />
|-<br />
| Tear shape. || 0.76<br />
|}<br><br />
<br />
=====Comminutors and Grinders=====<br />
Processing coarse solids reduces their size so they can be removed during downstream treatment operations, such as primary clarification, where both floating and settleable solids are removed. Comminuting and grinding devices are installed in the wastewater flow channel to grind and shred material up to 6 to 19 mm in size. Comminutors consist of a rotating slotted cylinder through which wastewater flow passes. Solids that are too large to pass through the slots are cut by blades as the cylinder rotates, reducing their size until they pass through the slot openings. <br />
<br />
Grinders consist of two sets of counter-rotating, intermeshing cutters that trap and shear wastewater solids into a consistent particle size, typically 6 mm (0.25 in). The cutters are mounted on two drive shafts with intermediate spacers. The shafts counter-rotate at different speeds to clean the cutters. The chopping action of the grinder reduces the formation of rag “balls” and rag “ropes” (an inherent problem with comminutors). Wastewaters that contain large quantities of rags and solids, such as prison wastewaters, utilize grinders downstream from coarse screens to help prevent frequent jamming and excessive wear.<br />
'''Caution: A designer must satisfy oneself as to why the materials need to be shredded down into small pieces and eventually design how to remove them from the wastewaters.''' <br />
=====Grit Chamber=====<br />
Grit consists of sand, gravel, stones, soil, cinders, bone chips, coffee grounds, seeds, eggshells, glass fragments, metals and other materials present in wastewater which do not putrefy. In general, grit as defined above has a specific gravity between 1.5 and 2.7 as opposed to a specific gravity for organics of approximately 1.02. In addition, grit settles as discrete particles, rather than as flocculant solids which is the case with organics.<br />
<br />
Grit consists of discrete particles which settle independent of one another with a constant velocity. When a discrete particle is left alone in a liquid at rest, it is subjected to a settlement force of gravity and to a resistance resulting from the viscosity of the fluid and inertia. For any given size and density of particle, there is a particular settling velocity. This settling velocity is changed somewhat when the liquid in which the particle is contained is subjected to a horizontal velocity. Grit settlement is generally regarded as following Stokes' Law which may be stated as:<br />
<br />
'''Stokes Law'''<br><br />
[[File:Equation_4.31.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Where: <br />
V<sub>n</sub> = settling velocity (m/s):<br><br />
g = gravitational acceleration (m/s<sup>2</sup>):<br> <br />
n= viscosity of liquid (kg/ms): Table 4 .37 Comparison of LRTF and HRTF<br><br />
l<sub>s</sub> = density of particle (kg/m<sup>3</sup>):<br><br />
l<sub>i</sub>= density of liquid (kg/m<sup>3</sup>): and <br><br />
d = diameter of particle (m)<br><br />
<br />
====Primary Treatment====<br />
<br />
=====Septic Tanks=====<br />
Please refer to the section 4.2.2 on the design of septic tank as a primary treatment<br />
=====Settler/Clarifier/Sedimentation Tank=====<br />
The main purpose of a settler is to facilitate sedimentation by reducing the velocity and turbulence of the wastewater stream. Settlers are circular or rectangular tanks that are typically designed for a hydraulic retention time of 1.5-2.5 h. Less time is needed if the BOD level should not be too low for the next biological step. The tank should be designed to ensure satisfactory performance at peak flow. In order to prevent eddy currents and short-circuiting, as well as to retain scum inside the basin, a good inlet and outlet construction with an efficient distribution and collection system (baffles, weirs or T-shaped pipes) is important.<br />
<br />
Depending on the design selected, desludging can be done using a hand pump, airlift, vacuum pump, or by gravity using a bottom outlet. Large primary clarifiers are often equipped with mechanical collectors that continually scrape the settled solids towards a sludge hopper in the base of the tank, from where it is pumped to sludge treatment facilities. A sufficiently sloped tank bottom facilitates sludge removal. Scum removal can also be done either manually or by a collection mechanism. presents a typical cross section through the settler. The design considerations and procedures should follow like those ones for grit chamber.<br />
<br />
[[File:Figure_4.36.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.36: Section View of a Settler<br> <br />
(Source: adapted from Tilley, et al., 2014)<br><br />
<br />
=====Biogas Settler=====<br />
A DEWATS Biogas Settler is usually a gas- and watertight dome-shaped sub-surface structure. It is typically constructed with bricks or cement mortar/plaster. The primary function of the settler is to separate the incoming wastewater into liquid and solid components, and so allowing the digestion of organic solids. <br />
[[File:Figure_4.37.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Figure 4.37: Biogas Settler <br />
(Source: Tilley et al., 2014)<br />
<br />
The microbial digestion process occurs under anaerobic conditions (without oxygen) and results in the generation of biogas. The by-products of this process are (a) a digested slurry (digestate) that is stabilised and thus can be used as a soil amendment and (b) biogas that can be used for energy production. Biogas is a mixture of methane, carbon dioxide and other trace gases which can be converted to heat, electricity or light. presents a schematic sketch of a biogas settler.<br />
<br />
=====Design Principles of a Biogas Settler=====<br />
Biogas settlers are similar in construction and design as a fixed-dome or floating drum biogas plants. However, in opposition to biogas reactors, biogas settlers are designed for the retention of biomass and are thus typical high-rate biogas reactors. Other high-rate biogas plants are Anaerobic Baffled Reactors ABRs; Anaerobic Filters AF; and Up-flow Anaerobic Sludge Blanket Reactors (UASB). High-rate biogas reactors are characterized by a mixed flow regime: the liquid (e.g. flushing, anal cleansing or grey water) flows through (continuous flow), while the sludge (e.g. faeces, paper etc.) is retained (batch) and treated over a long time until it is removed and used as fertilizer. Thus, biogas settlers are characterized by relatively short hydraulic retention times (HRT) for the liquor and high sludge retention times (SRT) for the solid fraction (organic and inorganic). The settled sludge is transformed into biogas by anaerobic digestion). Gas bubbles to the top of the reactor are collected for use.<br />
At this point it is important to note that much of the design details can be refined through greater experience and empirical data. The following instructions are only a suggestion of design techniques brought together from a number of published articles.<br />
<br />
'''Digester (including gas holder)'''<br><br />
The size of the digester largely depends on the amount of waste to be added. Digester shape should enable a minimum surface area: volume ratio to be reached to reduce heat loss and construction costs. Hemispherical digesters with a conical floor often work best. To calculate the required digester volume (VD) use Equation 4.32:<br />
<br />
VD = VB x HRT ………………………………………………………………...............(4.32)<br />
<br />
Where:<br><br />
VD = Volume of the digester (m<sup>3</sup>)<br><br />
VB = Volume of biomass added per day (m<sup>3</sup>/day)<br><br />
HRT = Retention time required (days)<br />
<br />
The amount of human waste produced varies from person to person but generally lies in the region of 0.2-0.4kg (solid) and 1-1.3kg (liquid) per day (depending on diet, health, etc.). If other waste (animal dung, organic food waste, etc.) is added then this should also be taken into account. Clearly it is almost impossible to control the rates of waste input (especially in the case of latrines) so some discretion and common sense should be used when dealing with the numbers.<br />
<br />
The volume of the gas holder VG depends on the relative rates of gas production and consumption. To calculate the daily gas production (G) either Equation 4.33or Equation 4.34 can be used (it may be good to use both and take an average since data for Gy varies greatly):<br />
<br />
G = MB x Gy (moist mass) ………………………………………………………......(4.33)<br />
<br />
G = LSU x Gy (species) ………………………………………………..………….(4.34)<br />
<br />
Where:<br><br />
G = Daily gas production rate (m<sup>3</sup>/day)<br><br />
MB = Mass of biomass added per day (kg/day)<br><br />
LSU = Number of livestock units (number)<br><br />
Gy (moist mass) = Gas yield per kg of excreta per day (m<sup>3</sup>/kg/day)<br><br />
Gy (species) =Gas yield per kg of livestock unit per day(m<sup>3</sup>/kg/day)<br />
<br />
The gas holder must be designed such as to cover the peak consumption rate (VG1) (if the primary reason for construction is based on biogas demand) and the longest period of zero consumption (VG<sub>2</sub>) (if the primary reason for construction is safe excreta treatment/disposal). The larger of these 2 volumes should be used to specify the gas holder volume with an additional 20% safety margin. The following equations should be used to calculate VG<sub>1</sub>and VG<sub>2</sub><br />
<br />
VG<sub>1</sub> = Gcmax x Tcmax ………………………………………………………... (4.35)<br />
<br />
VG<sub>2</sub> = G x Tczero ………………………………………………………………... (4.36)<br />
<br />
Where:<br><br />
VG1= Gas holder volume 1 (m<sup>3</sup>)<br><br />
VG2= Gas holder volume 2 (m<sup>3</sup>)<br><br />
Gcmax= Maximum rate of gas consumption (m<sup>3</sup>/day)<br><br />
Tcmax= Maximum time of gas consumption (days)<br><br />
G = Daily gas production rate (m<sup>3</sup>/day)<br><br />
Tczero= Maximum time of zero gas consumption (days)<br />
<br />
Based on experience the ratio of digester volume: gas holder volume (i.e. VD:VG) usually lies in the range 3-10:1. Since the hemispherical design of the fixed-dome generator combines the digester volume (VD) with the gas holder volume (VG), the total volume of the hemispherical dome (VH) can then be calculated:<br />
<br />
VH = V<sub>D</sub>V<sub>G</sub>………………………………………………………………………… (4.37)<br />
<br />
The final part of the calculation is to determine the required radius (r) of the hemisphere. This can be done using Equation 4.38:<br />
<br />
r=((3Vh)/ (2)) <sup>1/3</sup> ………………………………………………………………… (4.38)<br />
<br />
NB: Any calculated value should be taken as only an estimate–there are so many variables in the inputs (Hydraulic Retention Time (HRT), waste addition rate, gas consumption rate, climate, etc.) so the value should be used with caution.<br><br />
<br />
'''Displacement tank''' –There are a number of different options for the design (size, shape, etc.) of displacement tanks. The tank could be a fully buried hemispherical structure (much the same as but smaller than the digester), a simple column tank or a large open drying bed. Available materials, workforce skills level, safety and space are factors which need assessing before choosing a befitting design. The primary functions of the displacement tank are to provide a buffer for the pressure of the gas inside the digester and to allow digested slurry to be removed. The main parameters of the design are volume of the tank and height of the slurry overflow. The required size largely depends on the fluctuation in gas volume/pressure over time (e.g. 1 day). If the gas volume fluctuates a large amount then a large tank is required to prevent too much slurry being lost through the overflow during times of high gas pressure (which will cause a low pressure of the next batch/collection of gas). If the gas volume does not fluctuate at all (e.g. rates of gas production/use are the same) then in theory a displacement tank may not be needed at all (which is unlikely).<br />
According to experience the volume of the displacement tank should be roughly equal to that of the gasholder. However, there is a lot of variance between designs since the shape of the displacement tank can vary so much (from a simple self-contained tank with an overflow to a large drying bed structure).<br />
<br />
====Secondary Treatment====<br />
=====Anaerobic Baffled Reactor=====<br />
An ABR () is a modified septic tank with a series of baffles under which the wastewater is forced to flow. The increased contact time with the active biomass (sludge) results in improved treatment. The up-flow chambers provide enhanced removal and digestion of organic matter. The BOD can be reduced by 70% to 90%, which is far superior to its removal in a conventional septic tank. The main function of an ABR is the conversion of particulate matter into soluble BOD, as well as a certain percentage of soluble BOD into Methane (CH4). This is achieved by de-coupling HRT from Solids Retention Time.<br><br />
<br />
[[File:Section_View_of_an_ABR.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.38: Section View of an ABR (Source: Tilley, 2014).<br><br />
<br />
'''(a) Design Parameters'''<br><br />
The classic ABR process design consists of a number of equally dimensioned compartments. For a specific wastewater flow, the design is fully specified by fixing the following six independent parameters:<br> <br />
(i) Design hydraulic retention time,<br> <br />
(ii) Number of compartments,<br> <br />
(iii) Peak up-flow velocity,<br> <br />
(iv) Compartment width to length ratio,<br> <br />
(v) Reactor depth and <br><br />
(vi) Compartment up-flow to down-flow area ratio.<br> <br />
<br />
The civil design of the reactor interior also requires values for hanging baffle clearance, headspace height, baffle construction and inlet and outlet construction. All other internal features such as length and width individual compartments dimensions are dependent on the first six parameters.<br />
<br />
'''Fixing the design'''<br><br />
Table 4 .29presents the recommended ranges for the values needed for the design parameters for an ABR treating domestic wastewater. Although the limits of operation have not been fully tested, these values have been selected based on experiences gained through 5 years of observing laboratory-and pilot-scale reactors in operation.<br><br />
<br />
Table 4.29: Recommended Ranges for Parameters in the Design of an ABR (Source: Foxon et al., 2004)<br><br />
[[File:Recommended_Ranges_for_Parameters_in_the_Design_of_an_ABR.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
=====Anaerobic Filter (AF)=====<br />
An AF () is a fixed-bed reactor in an anaerobic contact process, with one or more filtration chambers in series. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the active biomass that is attached to the surface of the filter material. Filter material can be gravel, rocks or specially formed plastic pellets. To reduce costs, locally available material shall be used. For example, in Tanzania, coconut husks can be used or in Indonesia volcanic rock might be a good solution. Good filter material provides 90m2 to 300m2 surface area per m3. With this technology, TSS and BOD<br />
removal can be as high as 90%, but typically ranges between 50% and 80%. Nitrogen removal is limited and normally does not exceed 15% in terms of total nitrogen (TN).<br />
<br />
[[File:Section_of_an_AF.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.39: Section of an AF (Source: Tilley, 2014)<br><br />
<br />
'''(b) Design criteria and procedures'''<br><br />
The use of AFs for the treatment of domestic wastewater has been intended mainly for the polishing of effluents from septic tanks, UASB reactors and ABRs. In this configuration, the main design consideration is described below:<br />
<br />
'''(c) Hydraulic detention time'''<br><br />
The hydraulic detention time refers to the average time of residence of the liquid inside the filter, calculated by the following expression:<br />
<br />
[[File:Equation_4.39.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
'''(d) Temperature '''<br><br />
Anaerobic filters can be satisfactorily operated at temperatures ranging from 25 to 38<sup>o</sup>C. Usually, the degradation of complex wastewater, whose first stage of the fermentation process is hydrolysis, requires temperature higher than 25<sup>o</sup>C. Otherwise, hydrolysis may become the limiting stage of the process.<br><br />
'''(e) Packing medium height'''<br><br />
Based on the Brazilian experience, it is recommended for most applications that the packed bed height should be between 0.8 and 3.0 m. The upper height limit of the packed bed is more appropriate for reactors with lower risk of bed obstruction, which depends mostly on the flow direction, on the type packing material and on the influent concentrations. Amore usual value should amount to approximately 1.5 m. <br><br />
'''(f) Hydraulic Loading rate'''<br><br />
The hydraulic loading rate to the volume of wastewater applied daily per unit area of the filter packing medium, can be calculated by equation 4.40.<br><br />
[[File:Equation_4.40.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
'''(g) Organic Loading rate'''<br><br />
The volumetric organic loading rate refers to the load of organic matter applied daily per unit volume of the filter or packing medium, as calculated by Equation 4.41<br><br />
[[File:Equation_4.41.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
'''Effluent distribution and collection systems'''<br><br />
A very important aspect of the design of AFs concerns the detailing of the wastewater inlet and outlet devices, since the efficiency of the treatment system depends substantially on the good distribution of the flow on the packing bed, and this distribution is subject to the correct calculation of the inlet and outlet devices. <br />
<br />
In the case of Up-flow Anaerobic Filters, the flow distribution tube has been used for every 2.0 to 4.0m<sup>2</sup> of filter bottom area. shows the wastewater distribution device, through perforated tubes, and the effluent collection launder.<br />
[[File:Figure_4.40.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.40: (a) and (b) Sewage Distribution Device at the Bottom of an AF and Effluent Collection Launder on the Top of the AF<br><br />
'''(h) Efficiency of Anaerobic Filters'''<br><br />
The expected efficiencies for AFs can be estimated from the performance relationship presented in equation 4.42<br><br />
[[File:Equation_4.42.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
In situations where anaerobic filters are used as post-treatment units for effluents from septic tanks and UASB reactors, the BOD removal efficiency expected for the system as a whole varies from 75% to 85%.<br />
<br />
From the efficiency expected for the system, the COD or BOD concentration in the final effluent can be estimated as follows:<br />
[[File:Equation_4.3.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Table 4.30: Design Criteria for Anaerobic Filters Applied to the Post-treatment of Effluents from Anaerobic Reactors (Source: Tilley et al., 2014)<br><br />
[[File:Table_4.30.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
=====Up-flow Anaerobic Sludge Blanket Reactor (UASB)=====<br />
The UASB (Figure 4 .41) is a single-tank process. Wastewater enters the reactor from the bottom and flows upward. A suspended sludge blanket filters and treats the wastewater as the wastewater flow through it. <br />
<br />
A UASB is not appropriate for small or rural communities without a constant water supply or electricity. The technology is relatively simple to design and build, but developing the granulated sludge may take several months. The UASB has the potential to produce higher quality effluent than septic tanks and a Biogas Settler and can do so in a smaller reactor volume. Although it is a well-established process for large-scale industrial wastewater treatment and high organic loading rates up to 10 kg BOD/m3/d, its application to domestic sewage is still relatively new.<br><br />
[[File:Fig_4.41.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.41: Section View of an UASB Reactor (Source: Tilley et al., 2014)<br />
<br />
'''Design procedures for UASB Reactor'''<br />
<br />
'''Determine nominal volume of UASB Reactor'''<br><br />
[[File:Equation_4.44_and_Equation_4.45.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
'''Determine total liquid volume of UASB Reactor'''<br><br />
Consider factor of effectiveness = 0.80<br><br />
[[File:Equation_4.46.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where:<br><br />
VL, total liquid volume of the reactor (m3),<br> E the effectiveness factor (unit less).<br />
<br />
'''Find out an area of UASB Reactor'''<br><br />
'''Calculate Diameter of UASB Reactor'''<br />
<br />
[[File:Equation_4.48.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''Find out the new volume of reactor'''<br><br />
[[File:Equation_4.49.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''Determine the total Liquid Height of the UASB Reactor'''<br><br />
The gas collection volume is additional to the reactor volume and adds an additional height of 2.5 m-3 m; hence the total height of the reactor is given by:<br><br />
[[File:Equation_4.50.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where<br> HT is the total height of the reactor (m) and<br> HG is the total height of the gas collection and storage (m).<br><br />
'''Calculate hydraulic Retention Time (HRT) in UASB Reactor'''<br><br />
The hydraulic retention time,τ is given by:<br />
<br />
[[File:Equation_4.51.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''The Sludge Retention Time (SRT) in UASB'''<br><br />
The value of SRT can be estimated by assuming that all the wasted biological solids are in the effluent. The design approach is to assume that the given effluent VSS concentration consists of biomass (Metcalf and Eddy, 2004).<br />
<br />
'''The Solid Wasted'''<br />
<br />
[[File:Equation_4.52.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where:<br><br />
Q flow rate m<sup>3</sup>/d and<br> Xe is particulate COD.<br />
<br />
[[File:Equation_4.53.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where:<br><br />
y = Biomass yield M of cell formed per M of substrate consumed <br><br />
k<sub>d</sub>= Endogenous decay coefficient <br><br />
f<sub>d</sub> =Fraction of cell mass remaining as cell debris=VSS cell debris/g VSS biomass decay<br><br />
nbVSS = non-biodegradable volatile suspended solids, mg/L<br><br />
S<sub>o</sub> = Initial substrate concentration (COD) at time t = 0, mg/L,<br> <br />
S = Substrate concentration (COD) at time t, mg/L<br><br />
SRT = Sludge Retention Time, d<br><br />
μm = Maximum growth rate.<br />
<br />
'''Data for Determining SRT'''<br />
<br />
'''Effluent COD (S) at COD removal efficiency'''<br />
<br />
[[File:Equation_4.54.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Where:<br><br />
S is effluent COD, mg/l, S<sub>o</sub> is influent COD, mg/l and <br><br />
ξ is reactor COD removal efficiency<br><br />
The effluent VSS concentration <br><br />
Consider that efficiency (ε) 50% of influent VSS is degraded (Metcalf and Eddy, 2004)<br />
<br />
[[File:Equation_4.55.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''The particulate COD (Xe)'''<br> <br />
Consider at efficiency (ε) 50% of COD degraded (Metcalf and Eddy, 2004).<br><br />
<br />
[[File:Equation_4.56.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''Solve for SRT'''<br />
<br />
[[File:Equation_4.57.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
'''Effluent COD due to calculated SRT'''<br />
<br />
[[File:Equation_4.58.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''Check for adequacy of computed SRT'''<br />
<br />
[[File:Equation_4.59.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
If the fraction of COD<sub>infl</sub> in effluent is higher than 15% remaining in effluent, then the process SRT is inadequate.<br />
<br />
'''Check for concentration in biomass zone of the UASB reactor (XTSS)'''<br><br />
The recommended range is 50-100g/L at bottom of reactor and 5-40g/L in a more diffuse zone at the top of the UASB sludge blanket (Metcalf and Eddy, 2004).<br />
<br />
[[File:Equation_4.60.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''Effluents BOD<sub>5</sub>'''<br><br />
Since, the ratio of COD to BOD<sub>5</sub> for industrial wastewater can be approximated as 2-2.5 <br />
(COD = 2.25BOD<sub>5</sub>), hence;<br />
<br />
[[File:Equation_4.61.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
====Tertiary Treatment====<br />
=====Horizontal Subsurface Flow Constructed Wetland=====<br />
A Horizontal Sub-Surface Flow Constructed Wetland (HSSF-CW) (Figure 4 .42) also known as Planted Gravel Filter is a large gravel and sand-filled basin that is planted with wetland vegetation. As wastewater flows horizontally through the basin, the filter material filters out particles and micro-organisms degrade the organics. The filter media acts simultaneously as a filter for removing solids, a fixed surface upon which bacteria can attach, and a base for the vegetation. Although facultative and anaerobic bacteria degrade most organics, the vegetation transfers a small amount of oxygen to the root zone so that aerobic bacteria can colonise the area and degrade organics there as well. The plant roots play an important role in maintaining the permeability of the filter. This technology has been intensively researched at UDSM since early 1990 (IWSA Conference Proceedings, Vol I and II, 2002). Several systems have been installed in Tanzania (Figure 4 .43).<br />
<br />
[[File:Fig_4.42.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.42: Section View of a Horizontal Sub-surface Flow Constructed Wetland<br><br />
(Source: Kadlec, 2008)<br><br />
<br />
'''(a) Design Considerations for the CWs'''<br><br />
The design work should be based on good engineering practice and standards. It must also integrate the local practices and economics. The design should consider the following technical and environmental factors: <br />
<br />
* The design has to adopt first order, plug flow reaction kinetics for BOD removals and check for compliance with Total Suspended Solids (TSS), Nitrate (NO<sub>3</sub>), Ammonia (NH<sub>3</sub>), Total Phosphorus (P) and Faecal Coliforms.<br><br />
* Considering sensitivity of the location (bordered by a natural wetland), the old Reed approach(Reference) which considers temperature based pollutant removal rate constant and provide for maximum surface area enough to carry the treatment, was used.<br><br />
* The systems should be designed to meet the local and international discharge limits as the treatment goals.<br />
<br />
'''(b) Design procedures for CW'''<br><br />
'''Determine Design Population'''<br><br />
The estimation and projection of the population to be served is the first step in estimation of the quantity of the wastewater to be treated.<br />
<br />
'''Determine Water Demand'''<br><br />
Literature suggests that 80% of the water consumption will be wastewater, therefore it is important to measure or estimate the water demand based on the per capita water demand and the population to be served.<br />
<br />
[[File:Fig_4.43.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.43: Constructed Wetland Polishing the Wastewater from Aeration Unit of Mwanza City Abattoir Wastewater Treatment System<br />
<br />
'''Determine the Design Flow and wastewater characteristics'''<br><br />
Wastewater flows form the basis on which the CW and sewer sizes are determined. The wastewater flow rates are based on the existing water consumption and are derived by multiplying the water consumption rates by a factor less than unity, referred to as the ‘reduction factor’. The reduction factor takes into account the water that is supplied to the users but does not eventually end up as wastewater in the treatment system. A reduction factor of 20% is applied to estimate the quantity of wastewater generated.<br />
<br />
'''Determine the design Equations'''<br><br />
[[File:Table_2.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''BOD removal'''<br><br />
[[File:Equation_4.63.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where<br> <br />
C<sub>e</sub> = the effluent parameter mg/l<br><br />
C<sub>o</sub>= influent parameter mg/l<br><br />
K= First order removal rate constant (d<sup>-1</sup>)<br><br />
t = is Residence time ranges from 4-15 days for wetland.<br><br />
T = Temperature (<sup>o</sup>C)<br><br />
k<sub>20</sub> is a parameter specific.<br />
<br />
The Table 4 .31 presents k<sub>20</sub> values for different parameters<br><br />
Table 4.31: Values of K<sub>20</sub> for Different Parameters<br />
<br />
[[File:Table_4.31.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br> <br />
(Source: Cooper et al., 1996)<br><br />
<br />
'''Determine Surface area of a constructed wetland'''<br><br />
Assumptions<br><br />
Porosity=0.33 for coarse aggregate (adopted)<br><br />
Total depth=1 m<br> <br />
Effective depth (h) =0.6 m<br><br />
Freeboard=0.4 m<br><br />
[[File:Equation_4.65.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where:<br> <br />
HLR - Hydraulic Loading Rate should not exceed 5cm/day.<br> <br />
However Tanzanian experience reveals that hydraulic loading of up to 20cm/day provides sufficient wastewater treatment.<br><br />
NOTE: If the HRL does not fall within the specified limit, a new area is calculated by substituting the limit HRL.<br><br />
<br />
'''Total Suspended Solids removal'''<br><br />
[[File:Equation_4.66.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''TP removal'''<br><br />
[[File:Equation_4.67.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
K<sub>p</sub> = First order phosphorous removal rate constant = 2.73 cm/day<br><br />
<br />
'''Pathogen Removal'''<br><br />
[[File:Equation_4.68.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Check organic loading rate<br><br />
[[File:Equation_4.69.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
The BOD loading for HSSF-CW should not exceed 133 kg/ha.day (Metcalf and Eddy, 1991).<br><br />
<br />
'''Inlet Zone'''<br><br />
'''(c)''' The CW is designed to receive wastewater from a source through an inlet pipe/sewer. At an inlet zone it '''Layout and Configurations'''<br><br />
comprises of the pipes and the inspection chambers.<br><br />
<br />
'''Macrophyte and Substrate Zone'''<br><br />
This zone includes substrates (clean and graded granitic aggregates 1.3-1.9 cm) well packed, 65 cm thick), plants (diverse), a water column, invertebrate and vertebrates, and an aerobic and anaerobic microbial population. The water flow is maintained at 50cm above the bed surface. Within the water column, the stems and roots of wetland plants significantly provide the surface area for the attachment of microbial population. This zone therefore, is designed to provide the substrate with high hydraulic conductivity; to provide surface for the growth of Biofilm to aid in the removal of fine particles by sedimentation or filtration; to provide suitable support for the development of extensive root and rhizome system for the emergent plants.<br><br />
<br />
'''Outlet Zone'''<br><br />
This encompasses the following main components:<br> '''(a)''' An outlet pipe to collect effluent water and control the depth of the water without creating dead zones in the wetlands.<br> <br />
'''(b)''' Boulder stones (50–100 cm diameter size) to ensure for even collection of treated water across the full width of the CW<br><br />
'''(c)''' Wash out pipe to cater for flushing purposes during blockage and other functional problems<br><br />
'''(d)''' An outlet chamber to provide access for sampling and flow monitoring<br><br />
'''(e)''' A sewer line to the disposal area.<br> <br />
<br />
'''Geometrical and Hydraulic Data'''<br><br />
The CW unit is commonly built as a trapezoidal structure. However systems with vertical walls have also been designed and constructed and built in Tanzania especially when using bricks and cement blocks for the walls. The overall depth is 1.05m whereby substrate level is 0.65m and free board is 0.4m. The depth of water in the constructed wetland will be maintained at 0.6m from the bottom of the bed.<br><br />
<br />
Table 4.32: Geometrical, Hydraulic, Structural and Functional Features for the CW<br><br />
<br />
[[File:Table_4.32.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Source: Modified from (Kadlec and Wallace, 2009)<br><br />
<br />
====Treatment of Sludge from DEWATS====<br />
After desludging a Biogas Settler or ABR, the sludge should be treated in drying beds where pathogens are killed off through exposure to oxygen and UV-radiation. In addition, dewatering (or “thickening”) of sludge is an important treatment objective, as sludge contains a high proportion of liquid, and the reduction in this volume will simplify and greatly reduce the costs of subsequent treatment steps. Environmental and public health treatment objectives are achieved through pathogen reduction, stabilisation of organic matter and nutrients, and the safe end use or disposal of treatment end-products.<br />
=====Unplanted Sludge Drying Beds (USDB)=====<br />
An unplanted drying bed (USDB) is a simple, permeable bed that, when loaded with sludge, collects percolated leachate and allows the sludge to dry by evaporation. Approximately 50% to 80% of the sludge volume drains off as liquid or evaporates. presents section view of an Unplanted Sludge Drying Bed.<br />
<br />
[[File:Fig_4.44.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Figure 4.44: Section View of an Unplanted Sludge Drying Bed<br> <br />
(Source: Tilley, et al., 2014)<br />
<br />
'''Design Considerations'''<br><br />
The requirements for the design of a sludge drying bed are; volume of the sludge, climate, temperature and location. The bottom layer shall be of uniform gravel, and layer of clean sand lay over. Under-drains lay over the gravel layer for drainage of percolated liquid through these layers (Chatterjee, 1996).<br />
<br />
The bottom of the drying bed is lined with perforated pipes to drain away the leachate that percolates through the bed. On top of the pipes are layers of gravel and sand that support the sludge and allow the liquid to infiltrate and collect in the pipe. These layers should not be too thick (maximum 20 cm), or the sludge will not dry effectively. The final moisture content after 10 to 15 days of drying should be approximately 60%. When the sludge is dried, it must be separated from the sand layer and transported for further treatment, end-use or final disposal. The leachate that is collected in the drainage pipes must also be treated properly, depending on where it is to be reused or disposed.<br />
<br />
'''Design procedures and steps for unplanted sludge drying beds'''<br><br />
The design procedures for unplanted sludge drying beds is the same as for similar unit for FSM. The user of this manual is instructed to consult section 3.2.7.2.<br><br />
<br />
=====Planted Sludge Drying Beds=====<br />
The design procedures for the Planted Sludge Drying Bed see section 3.2.7.3.<br><br />
<br />
==Simplified Sewerage System (Condominial System)==<br />
<br />
Simplified sewerage is an off-site sanitation technology that removes all wastewater from the household environment. Conceptually, it is the same as conventional sewerage, but with conscious efforts made to eliminate unnecessarily conservative design features and to match design standards to the local situation. Simplified sewerage, also known as condominial system, is an important sanitation option in peri-urban areas of DC, especially as it is often the only technically feasible solution in the high-density areas. It is a sanitation technology widely known and used in Latin America. However, it is much less well known and applied in Africa and Asia and particularly Tanzania.<br><br />
<br />
===Key Features of a Simplified Sewerage System===<br />
Key features of the condominium system include the following:<br><br />
(a) '''Layout''': in-block system (Figure 4 .45), rather than–as with conventional sewerage –an in-road system. The key feature of an in-block system is that sewers are routed in private land, through either back or front yards. This in-block or back-yard system of simplified sewerage is often termed condominium sewerage in recognition of the fact that tertiary sewers are located in private or semi-private space within the boundaries of the `condominium’.<br> <br />
(b) '''Depth and diameter''': simplified sewers are laid at shallow depths, often with covers of 400 mm or less. The minimum allowable sewer diameter is 100 mm, rather than the 150 mm or more that is normally required for conventional sewerage. The relatively shallow depth allows small access chambers to be used rather than large expensive manholes.<br><br />
[[File:Fig_4.45.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.45: Layouts of In-block Simplified (Condominial) Sewerage for Unplanned and Planned Peri-urban Housing Areas <br />
(Source: Sinnatamby, 1983)<br><br />
[[File:Fig_4.46.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.46: Alternative Routes for Simplified Sewers (Source: Sinnatamby, 1983)<br><br />
<br />
===Planning for Simplified Sewerage System===<br />
This section is subdivided into two parts: Part one is concerned with the initial assessment of sanitation options. The assessment of technical options is explained and the issues relating to the management options for simplified sewerage are explored. Part two sets out the sewerage planning process, from the decision to adopt simplified sewerage system to the development of the overall sewerage layout. It explains what information is needed for the planning process and explores the factors that will influence the area to be included in a sewerage scheme. This leads in to the development of a draft sewerage plan. <br><br />
'''A.a Initial assessment of Sanitation Options'''<br><br />
Two basic questions should be asked at the beginning of the planning process. These are:<br><br />
* What sanitation options are feasible in the local situation? and <br><br />
* Assuming that simplified sewerage is feasible, what arrangements are possible for managing the construction and subsequent operation and maintenance of the local condominial systems?<br />
<br />
'''i Technical options'''<br><br />
This is the stage at which the decision to use simplified sewerage will be made. Simplified sewerage should only be considered where a reliable water supply is or can be made available on or near each plot so that total water use is at least 60 litres per person per day.<br />
<br />
Other factors to be considered are:<br><br />
*population density, <br><br />
* the arrangements for effluent disposal and the preferences of the local people; for evaluating on-site sanitations options the plot size,<br><br />
* the infiltration capacity of the soil and <br><br />
* the potential for groundwater pollution should also be considered (see Franceys et al., 1992; Cotton and Saywell, 1998; and GHK Research and Training, 2000).<br />
<br />
'''ii Management options'''<br><br />
It is important to consider the possible management options for any proposed sanitation system from the very beginning of the planning process. In general, the more small-scale and local a sanitation system is the better the prospects for local management. So, it would appear that on-plot sanitation systems such as pit latrines and pour-flush toilets discharging to leach pits can be managed by individual householders, while city-wide sewage disposal systems must be managed at the municipal level.<br />
'''A.b Planning for simplified sewerage systems '''<br><br />
This section describes the steps to be taken during planning and adoption of a simplified sewerage system. These steps can be summarized as follows: <br><br />
i. Collect existing information, focusing particularly on maps and plans of the area to be sewered and adjacent areas,<br> <br />
ii. Determine the area to be included in the sewerage plan, based on topography, the location of existing sewers and the limits of existing and future development, <br><br />
iii. Develop a draft sewerage plan, showing the routes of the main collector sewers and the approximate areas of the various condominial systems,<br><br />
iv. Undertake additional surveys as required to allow sewer routes and the areas of condominial systems to be confirmed, so that detailed design can be carried out, and <br><br />
v. Finalise the overall sewerage plan and plot the sewer routes at an appropriate scale or scales.<br />
<br />
'''A.c Collection of existing information'''<br><br />
The first task in the planning process is to collect all available information on the area to be sewered. In particular, existing topographical maps and any maps showing the routes of any existing drains and sewers should be collected, as these are needed to define the area to be sewered and to determine the overall sewer layout. This information may be available on a number of maps and plans; if this is the case, as much information as possible should be transferred to one base plan. Information on the existing management arrangements and responsibilities also needs to be collected.<br />
<br />
'''A.d Areas to be included'''<br><br />
The next task is to decide the area to be included in the scheme. There are two possible situations. The first is that the design is for an exclusively local system, which can be connected to a local treatment facility or an existing collector sewer. The second is that there is a need to look at the sewerage needs of a wider area, including both local condominial sewers and public collector sewers. In the first case, the decision on the area to be included in the scheme is relatively straightforward.<br />
<br />
'''A.e Development of a draft sewerage plan'''<br><br />
It should now be possible to develop a draft sewerage plan. The first step is to decide the routes of the main public collector sewers and then consider how local condominial systems can be joined to them. In general, public collector sewers should be designed to include flows from all parts of the drainage area that are or are likely to be sewered. Failure to do this will mean that the sewers will be undersized, if not immediately then certainly in the future.<br />
<br />
'''A.f Physical and social surveys'''<br><br />
If accurate survey information is not available, detailed physical and social surveys are generally required. Each is briefly considered in turn below.<br />
<br />
'''A.g Physical surveys'''<br><br />
Physical surveys are required in order to determine sewer routes and levels. If existing plans exist, it may be possible to use them, at least for preliminary design.<br />
<br />
'''A.h Social surveys'''<br><br />
Simple social surveys should be used to provide information on household sizes and incomes, existing sanitation and water supply facilities, attitudes to sanitation and user preferences. Questionnaire surveys are useful for providing quantitative information. Semi-structured interviews and focused group discussions are more likely to provide information on attitudes and preferences.<br />
<br />
'''A.i Final sewer routes'''<br><br />
Once good survey information has been obtained, it can be recorded on suitable plans and detailed design of the system can commence. Minor changes to the routes of collector sewers may be required as a result of improved survey information. More substantive changes may be necessary in condominial systems as a result of the findings of both the physical and social surveys.<br />
<br />
===Detailed Design Considerations and Procedures===<br />
The design procedures for simplified sewerage system follows that on conveyance section under DEWAT section 4.2.<br />
<br />
==Centralized Wastewater Treatment==<br />
===Overview===<br />
A centralized system uses a series of sewer pipes, tunnels, and pumps to collect wastewater and to transport it to a central treatment plant. The sewer pipes can be combined (including stormwater runoff) or separate. The sewer is the pipe or conduit for carrying sewage. It is generally closed and flow takes place under gravity (Atmospheric Pressure). There are two types of sewers for central systems, central system and simplified sewerage system also known as condominial system.<br />
===Design Consideration for Central Sewer===<br />
====Sewage Flow====<br />
It is flow derived from sewage that is the raw water from these industries and houses, Also it means it has direct relation with the amount of water consumed. Generally 80 to 90% of the water consumption is taken as sewage or wastewater flow.<br />
Design of Sewer System<br />
'''a Variation in sewage flow'''<br><br />
Like water supply, sewage flow varies from time to time. Since sewers must be able to accommodate Maximum Rate of Flow, the variation in the sewage flow must be studied. Generally Herman Formula is used to estimate the ratio of Maximum to Average Flow.<br><br />
[[File:Equation_4.70.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
P is population in thousands. Sewer System<br><br />
Design considers the following relationship for sewer design:<br><br />
Table 4.33: Relationship Between Average Sewage Flow and Peak Factor<br />
[[File:Table_4.33.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] (Source: Tchobanoglous et al., 2003)<br><br />
'''(b) Infiltration'''<br><br />
This is amount of water that enters into the sewers through poor joints, cracked pipes, walls and covers of manholes. Design of Sewer System<br><br />
* It is non-existent during dry weather but increases during rainy season.<br><br />
* During the wet season, the following infiltration rates for the design of sewer system are recommended.<br><br />
<br />
Table 4.34: The Relationship Between Sewer Diameter and Infiltration<br />
[[File:Table_4.34.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
(Source: Tchobanoglous et al, 2003)<br><br />
<br />
'''Design Procedures'''<br />
<br />
'''(a) Design Flow'''<br><br />
Calculate the average sewage flow on the basis of water consumption and the population at the end of the design period. That is at the full development of the area. Then the design flow for sanitary sewer and partially combined sewers can by calculated by using the following formulae.<br><br />
Design of Sewer System<br><br />
For sanitary sewer<br><br />
Q<sub>design</sub>= Peak sewage flow + infiltration<br><br />
For partially combined sewer (WASA Criteria)<br><br />
Q<sub>design</sub> = 2xPeak sewage flow + infiltration<br><br />
'''(b) Determine flow velocity using design Equation'''<br><br />
Manning’s Equation is used for sewers flowing under gravity<br><br />
[[File:Equation_4.71.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where:<br><br />
V = Velocity of flow in m/sec<br><br />
R = Hydraulic mean depth (A/P) = D/4 when pipe is flowing full or half full<br><br />
S = Slope of the sewer<br><br />
n = Coefficient of roughness for pipes<br><br />
<br />
'''(c) Flow velocity selection<br>'''<br />
<br />
'''(i) Minimum (Self Cleansing) Velocity<br>'''<br />
Sewage should flow at all times with sufficient velocity to prevent the settlement of solid matter in the sewer. Self-Cleansing Velocity is the minimum delivery speed that ensures non settlement of suspended matter in the sewer. The following minimum velocities are generally employed;<br><br />
* Sanitary sewer = 0.6 m/sec<br><br />
* Storm sewer = 1.0 m/sec<br><br />
* Partially combined sewer = 0.7 m/sec<br><br />
<br />
'''(ii) Maximum velocity<br>'''<br />
The maximum velocities in the sewer pipes should not exceed more than 2.4 m/sec. This max velocity in the sewer should not exceed this limit of 2.4 m/sec. It is to avoid the excessive sewer abrasion and also to avoid steep slopes.<br><br />
<br />
'''(d) Minimum Sewer Size<br><br />
225 mm is taken as the minimum sewer size. The reason being that, the choking does not take place even with the bigger size particles, which are usually thrown into the sewer through manholes.<br><br />
Design of Sewer System<br><br />
'''(e) Minimum Cover of Sewe'''r<br><br />
1m is taken as the minimum cover over the sewers to avoid damage from live loads coming on the sewer.<br><br />
<br />
'''(f) Spacing of Manhole '''<br><br />
For (Sewer Size) 225 mm to 380 mm - spacing not more than 100 m<br><br />
For (Sewer Size) 460 mm to 760 mm spacing not more than 120 m<br><br />
For (Sewer Size) greater than 760 mm spacing not more than 150 m<br><br />
<br />
'''(g) Direction of Sewer Line'''<br><br />
Sewer should flow, as for as possible the Natural Slope. Design of Sewer System<br><br />
<br />
'''(h) Design of the Sewer'''<br><br />
'''(i) Size of Sewer'''<br><br />
Use the following relation to find the diameter of sewer<br><br />
<br />
Q<sub>f</sub> = A x V ………………………………………………………..…….................(4.72)<br />
<br />
'''ii Slope of Sewer'''<br><br />
Select the minimum velocity value and use the Manning’s formula<br />
<br />
[[File:Equation4.73.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''iii Invert Level'''<br><br />
The lowest inside level at any cross-section of a sewer pipe is known as invert level at that cross-section.<br />
Design System<br />
Invert Level = NGSL/Road Level – Depth of Sewer – Thickness of Sewer – Diameter of Sewer<br />
<br />
[[File:Figure4.47.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.47: Invert Level of Sewer pipe<br><br />
(Adapted from http://www.hkius.org.hk)<br><br />
<br />
'''iv Joints in Sewers''' <br />
* Bell & Spigot Joint<br />
* Tongue &Groove Joint<br />
<br />
Typical Steps of Sewage Treatment system<br><br />
Figure 4.22 provides a flow diagram of a typical wastewater treatment system.<br><br />
<br />
[[File:Fig_4.48.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
<br />
Figure 4.48: Flow Diagram of a Typical Wastewater Treatment System<br />
<br />
Preliminary treatment<br />
Under this category, the units involved include Screens, Grit chamber, FOG trap etc. The design procedures and considerations follow those presented under DEWAT Section 3.3.1. The use of comminattors is not encouraged in practice.<br />
<br />
Primary treatment<br />
Examples of primary treatment units are septic tanks, primary sedimentation, and anaerobic ponds. With exception of roughing filters and anaerobic ponds (which is presented under WSP section) the other units follow the design procedures as the ones presented in Section 3.3.1 of DEWAT.<br />
<br />
Secondary treatment<br />
The design procedures and considerations for other systems are provided in secondary treatment system other than the DEWAT. It is only trickling filters, activated sludge systems and waste stabilization ponds which are presented in this section.<br />
<br />
=====Waste Stabilization Ponds=====<br />
Waste Stabilization Ponds (WSPs) are large, shallow basins in which raw sewage is treated by entirely natural processes involving both algae and bacteria. They are used extensively for sewage treatment in moderate and tropical climates, and represent one of the most cost-effective, reliable and an easily operated process for the treatment of domestic and industrial wastes. WSP are very effective for the removal of faecal coliform, which is an indicator of pathogenic organisms. Sunlight energy is the only requirement for its operation. It requires minimum supervision for its daily operation by cleaning the outlets and inlet works. <br />
<br />
'''(a) Types of Waste Stabilization Ponds and Their Specific Uses'''<br><br />
Waste stabilization pond systems comprise a single series of anaerobic, facultative and maturation ponds or several such series in parallel. Figure 4.49 presents the schematic layout of types of WSPs.<br><br />
<br />
[[File:Fig_4.49.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
</div><br />
Figure 4.49: Schematic Layout of Types of WSP<br />
(Source:https://commons.wikimedia.org/w/index.php?sort=relevance&search=waste+stabilization+pond)<br />
<div style='text-align: justify'><br />
In essence, anaerobic and facultative ponds are designed for BOD removal and maturation ponds for pathogen removal. Some BOD removal occurs in maturation ponds and some pathogen removal in anaerobic and facultative ponds (Mara, 1987). Maturation ponds are required only when the effluent is to be used for unrestricted irrigation and has to therefore, comply with the WHO guideline of >1000 faecal coliforms per 100 ml. <br />
<br />
'''(b) Estimation of design flow and BOD concentration''' <br><br />
There are four most important design parameters for WSP; temperature, net evaporation, flow and BOD. Faecal coliforms and helminth egg numbers are very important if the final effluent is to be used in agriculture or aquaculture.<br> <br />
The mean flow should be carefully estimated, since this has direct effect on the size of the pond and costs of construction. A suitable design is 85% of the in-house water consumption. The BOD may be measured if the wastewater exists based on 24 hour flows. Alternatively, the BOD may be estimated from the following equation;<br />
<br />
[[File:Equation_4.74.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where: <br>Li is wastewater BOD (mg/l), <br>B is BOD contribution (g/cap.day), <br>q is wastewater flow (L/cap/day).<br />
<br />
The values of B vary between 30 and 70g per capita per day with rich communities producing more BOD than the poor communities (Campos and von Sperling, 1996). In medium sized towns, a value of 50g per cap/ day is more suitable (Mara and Pearson, 1987). A typical design figure for an urban area in a developing country would be 40 to 50 grams BOD5/cap/day (Arthur, 1976). A BOD5 contribution per capita of 40 grams/day with a wastewater contribution of about 100 litres/cap/day is probably a reasonable initial estimate where there is a household water supply, although flows may be considerably less. The usual range of faecal coliform in the domestic wastewater is 107–108 faecal coliform per 100 ml, and a suitable design value is 5 x 107 per 100 ml.<br />
<br />
'''(c) Design of anaerobic ponds'''<br />
Anaerobic pond is designed based on volumetric loading (λv, g/m<sup>3</sup>/d), which is given by:<br />
<br />
[[File:Equation_4.75.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where: Li is influent BOD (mg/l), Q is flow rate (m<sup>3</sup>/day), V<sub>a</sub> is anaerobic pond volume (m<sup>3</sup>). <br />
<br />
Meiring et al., (1998) recommends that the loading should be between 100 and 400g/m3.d in order to maintain anaerobic conditions. The hydraulic retention time is then calculated using equation.<br />
<br />
[[File:Equation_4.76.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
The retention time of less than one day should not be used for anaerobic ponds, if it happens then a retention time of one day should be used and a volume of the pond should be recalculated. Table 4 .35 shows the permissible loading to the anaerobic ponds.<br />
<br />
Table 4.35: Design Value of Permissible Volumetric BOD Loadings on and Percentage BOD Removal in Anaerobic Ponds at Various Temperatures<br />
[[File:Table4.35.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
T = temperature in <sup>o</sup>C <br><br />
(Source: Mara and Pearson, 1986 and Mara et al., 1997)<br><br />
<br />
'''(d) Design of facultative ponds'''<br />
Facultative ponds may be designed based on kinetic or empirical models. Use is made of kinetic models for design of facultative ponds as follows;<br />
<br />
Mathematically is as shown in equation<br />
<br />
[[File:Equation_4.77.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where:<br><br />
L is the amount of BOD remaining (=organic matter to be oxidized) at time “t” and <br><br />
k1 is first order rate constant for BOD removal (day-1). <br />
<br />
The rational equation for the design is as shown in equation;<br />
<br />
[[File:Equation_4.78.png|600px|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Rearranging the equation <br />
<br />
[[File:Equation4.79.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where: t is the retention time (days).<br />
<br />
The mid-depth area of the pond is calculated using equation:<br />
<br />
[[File:Equation_4.80.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where: <br>Q is the volumetric flow rate (m3/day), <br>D is the pond depth (m) and <br>A is the mid-depth area (m2). <br />
<br />
Substituting “t” from equation 4.79 into equation 4.80 the mid-depth area of the pond will be:<br />
<br />
[[File:Equation4.81.png|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
The value for k<sub>1</sub> at 20<sup>o</sup>C was found to be 0.3 day-1, while the value of k<sub>T</sub> are calculated using equation 4.82. Note that the rate k<sub>1</sub> is a gross measure of bacterial activity and in common with almost all parameters describing a biological growth process, its value is strongly temperature dependent. <br />
<br />
Its variation with temperature is usually described by an Arrhenius equation <br />
<br />
[[File:Equation4.82.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
[[File:Theta1.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
'''Empirical models for design of facultative pond'''<br><br />
Although there are several methods available for designing facultative ponds, Mara, 1976, recommends that facultative ponds should be designed on the basis of surface loading (with the reasons stated in sections above λ<sub>s</sub>, kg/ha.day) which is given by equation (4.83)<br><br />
<br />
[[File:Equation_4.83.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where: Li is the concentration of influent sewage (mg/l), A<sub>f</sub> is the facultative pond area, (m<sup>2</sup>). <br />
<br />
The selection of permissible design value of λ<sub>s</sub> is usually based on the temperature. <br />
<br />
The earliest relationship between λ<sub>s</sub> and temperature was given by McGarry and Pescode (1970), and later on by Mara (1976). The Mara (1976) equation is as shown in equation (4.84)<br />
<br />
[[File:Equation_4.84.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
However a most appropriate s and temperature relationship was presented by Mara (1987) and is termed as a global design equation;<br />
<br />
[[File:Equation4.85.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Once the surface loading has been selected then the area of the facultative pond is calculated from equation (4.83) and its retention time (θ<sub>f</sub>, day) is calculated from equation (4.86)<br />
<br />
[[File:Equation_4.86.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where; D is the pond depth (usually 1.5 m), Q<sub>m</sub> is the mean flow (m<sup>3</sup>/day).<br><br />
The mean flow is the mean of the influent and effluent flows (Q<sub>i</sub> and Q<sub>e</sub>), the latter being the former less net evaporation and seepage. Thus equation (4.86) becomes<br />
<br />
[[File:Equation_4.87.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
If seepage is negligible, Q<sub>e</sub> is given by<br><br />
<br />
<br />
[[File:Equation_4.88.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where: e is net evaporation rate, mm/day.<br> <br />
Hence equation (4.88) becomes:<br><br />
<br />
[[File:Equation_4.89.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
A minimum value of retention time of 5 days should be adopted for temperature below 20<sup>o</sup>C, and 4 days for temperature above 20<sup>o</sup>C. This is to minimize hydraulic short-circuiting and to give algae sufficient time to multiply (i.e. to prevent algal washout).<br><br />
<br />
'''(e) Design of Maturation ponds for faecal coliforms removal'''<br><br />
The method of Marais (1974) is generally used to design a pond series for faecal coliforms removal assuming first order kinetic model.<br><br />
<br />
[[File:Equation_4.90.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where;<br><br />
N<sub>e</sub> and N<sub>i</sub> is the number of FC per 100 ml in the effluent and influent, k<sub>T</sub> is the first order rate constant for FC removal, d<sup>-1</sup> θ is a retention time, (day).<br />
<br />
For a series of anaerobic, facultative and maturation ponds, equation (4.90) becomes:<br />
<br />
[[File:Equation_4.91.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where; the sub-scripts a, f and m refer to the anaerobic, facultative and maturation ponds; and n is the number of maturation ponds. It is assumed in equation (4.91) that all the maturation ponds are equally sized, this is the most efficient configuration (Marais, 1974), but may not be topographically possible (in which case the last term of the denominator in equation (4.91) is replaced by; [(1+k<sub>T</sub>θ<sub>m1</sub>) (1+k<sub>T</sub>θ<sub>m2</sub>).……. (1+k<sub>T</sub>θ<sub>mn</sub>)]).<br />
<br />
The value of k<sub>T</sub> is highly temperature dependent. Marais (1974) found that: <br />
<br />
k<sub>T</sub>=2.6(1.19)<sup>T-20</sup>...…………………………………………………………….....(4.92)<br />
<br />
'''(f) Helminth eggs removal'''<br><br />
Helminth eggs are normally removed by sedimentation and the process occurs in anaerobic or primary facultative ponds. If the final effluent is to be used for restricted irrigation, then it is necessary to ensure that it contains no more than one egg per litre. Analysis of eggs removal in the pond has yielded the following relation reported by Ayres et al.(1992). <br />
<br />
[[File:Equation4.93.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Where, R is percentage egg removal, θ is a retention time (day). The equation corresponding to lower 95 percent confidence limit of equation (4.93) is <br />
<br />
[[File:Equation4.94.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
<br />
Equation (4.93) or Table 4.36 is recommended to be used for the design. <br />
<br />
Table 4.36: Design Values of Helminth Egg Removal R(%) in Anaerobic, Facultative or Maturation Ponds at Various Hydraulic Retention Times<br />
[[File:Table_4.36.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
(Source: Ayres et al., 1992)<br><br />
<br />
'''(g) Design of WSP for nutrient removal'''<br><br />
Design equation for nutrient removal in WSP is based on the equation developed in North America and designers should use these with precaution that it might not accurately predict the performance as expected. The equation for ammoniacal nitrogen (NH<sub>3</sub> + NH<sup>+</sup><sub>4</sub>) removal in individual facultative ponds was presented by Pono and Middlebrooks (1982). The equation for the temperatures below 20oC is as follows:<br><br />
<br />
[[File:Equation4.95.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
For temperatures above 20<sup>o</sup>C;<br><br />
<br />
[[File:Equation4.96.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where;<br><br />
C<sub>e</sub>is ammoniacal nitrogen concentration in the pond effluent (mg N/L),<br> <br />
C<sub>i</sub> is ammoniacal nitrogen concentration in the pond influent, (mg N/L),<br> <br />
A is pond area (m<sup>2</sup>), and<br><br />
Q is influent flow rate (m<sup>3</sup>/day).<br />
<br />
The removal of total nitrogen in the individual facultative and maturation ponds was presented by Reed (1995) as follows;<br />
<br />
[[File:Equation4.97.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where,<br><br />
C<sub>e</sub> and C<sub>i</sub> is the total nitrogen concentration in the pond effluent and influent, respectively (mg N/L),<br>T is temperature (<sup>o</sup>C range 1-28(<sup>o</sup>C) and<br> θ is retention time (days; range 5 to 231 days). The pH values used in the above equations may be estimated as follows;<br />
<br />
[[File:Equation_4.98.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Where: A is influent alkalinity, mg CaCO<sub>3</sub>/L.<br><br />
<br />
=====Activated Sludge=====<br />
Activated Sludge Treatment is a biological wastewater treatment process which speeds up waste decomposition by adding activated sludge into wastewater, and the mixture is aerated and agitated for a specified amount of time thereby allowing the activated sludge to settle out by sedimentation and is disposed of (wasted) or reused (returned to the Aeration Tank as indicated in Figure 4.50). <br />
<br />
The activated sludge process has the advantage of producing a high quality effluent for a reasonable operating and maintenance costs. The activated sludge process uses micro-organisms to feed on organic contaminants in wastewater, producing a high-quality effluent. The basic principle behind all activated sludge processes is that as micro-organisms grow, they form particles that clump together. These particles (flocs) are allowed to settle to the bottom of the tank, leaving a relatively clear liquid free of organic materials and suspended solids.<br />
<br />
'''Design Considerations'''<br />
The items for consideration in the design of activated sludge plant are;<br><br />
'''(a)''' aeration tank capacity and dimensions,<br> <br />
'''(b)''' aeration facilities, <br><br />
'''(c)''' secondary sludge settling and <br><br />
'''(d)''' recycle and excess sludge wasting or re-use.<br><br />
<br />
[[File:Fig_4.50.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Figure 4.50: Schematic Diagram of a Typical Activated Sludge Process<br><br />
(Source: Chai, 2006)<br><br />
<br />
=====Aeration Tank=====<br />
The volume of Aeration Tank is calculated for the selected value of qc by assuming a suitable value of Mixed liquor Suspended Solids–(MLSS) concentration, X;<br><br />
<br />
[[File:Equation_4.99.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br />
<br />
Where,<br> <br />
V= volume of aeration tank, m<sup>3</sup><br><br />
X = MLSS concentration, mg/L<br><br />
Q = flow rate, m<sup>3</sup>/day<br><br />
S<sub>0</sub> = Influent sludge concentration, mg/L, (incoming BOD<sub>5</sub>)<br><br />
S = effluent sludge concentration, mg/L, (incoming BOD<sub>5</sub>)<br><br />
Y = Sludge yield coefficient<br><br />
k<sub>d</sub> = decay constant, d<sup>-1</sup><br><br />
<br />
Alternately, the tank capacity may be designed from;<br><br />
<br />
[[File:Equation_4.100.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br><br />
<br />
F = organic loading, kgBOD<sub>5</sub>/day<br><br />
M = mass, kg<br><br />
<br />
'''Design steps for Aeration Tank'''<br><br />
<br />
(a) Choose a suitable value of qc(or F/M)<br><br />
qc depends on: <br><br />
(i) the expected weather temperature of mixed liquor,<br> <br />
(ii) the type of reactor,<br><br />
(iii) expected settling characteristics of the sludge and <br><br />
(iv) the nitrification required.<br> <br />
<br />
The choice generally lies between 5 days in warmer climates to 10 days in temperate zones where nitrification is desired along with good BOD removal, and complete mixing systems are employed.<br />
<br />
(b) Select two interrelated parameters HRT, t and MLSS concentration<br />
<br />
It is seen that economy in reactor volume can be achieved by assuming a large value of X. However, it is seldom taken to be more than 5,000 g/m<sup>3</sup>. For typical domestic sewage, the MLSS value of 2000-3000 mg/l if conventional plug flow type aeration system is provided, or 3,000-5,000 mg/l for completely mixed types. <br />
<br />
Considerations which govern the upper limit are:<br> <br />
• initial and running cost of sludge recirculation system to maintain a high value of MLSS,limitations <br />
of oxygen transfer equipment to supply oxygen at required rate in small reactor volume,<br><br />
• increased solids loading on secondary clarifier which may necessitate a larger surface area,<br> <br />
• design criteria for the tank and minimum HRT for the aeration tank.<br><br />
<br />
The length of the tank depends on the type of activated sludge plant. Except in the case of extended aeration plants and completely mixed plants, aeration tanks are designed as long narrow channels. The width and depth of the aeration tank depend on the type of aeration equipment employed. The depth controls the aeration efficiency and usually ranges from 3 to 4.5 m. The width controls the mixing and is usually kept between 5 to 10 m. Width-depth ratio should be adjusted to be between 1.2 and 2.2. The length should not be less than 30 or not ordinarily longer than 100 m.<br />
<br />
'''Oxygen Requirements'''<br />
Oxygen is required in the activated sludge process for the oxidation of the influent organic matter and also for the endogenous respiration of the micro-organisms in the system. The total oxygen requirement of the process may be formulated as follows:<br />
<br />
O<sub>2</sub> required (g/d) =- 1.42Q<sub>w</sub>X<sub>r</sub> …………………………….................(4.101) <br />
<br />
Parameters in equation 4.101 have been defined in equations 4.99 and 4.100<br />
<br />
Where: f = ratio of BOD<sub>5</sub> to ultimate BOD and 1.42 = oxygen demand of biomass (g/g). <br />
The formula does not allow for nitrification but allows only for carbonaceous BOD removal.<br />
<br />
'''Aeration Facilities'''<br />
A of the activated sludge plant are designed to provide for the calculated oxygen demand of the wastewater against a specific level of dissolved oxygen in the wastewater.<br />
<br />
'''Secondary Settling'''<br />
Secondary settling tanks, which receive the biologically treated flow undergo zone or compression settling. Zone settling occurs beyond a certain concentration when the particles are close enough together that inter particulate forces may hold the particles fixed relative to one another so that the whole mass tends to settle as a single layer or "blanket" of sludge. The rate at which a sludge blanket settles can be determined by timing its position in a settling column test.<br />
<br />
Compression settling may occur at the bottom of a tank if particles are in such a concentration as to be in physical contact with one another. The weight of particles is partly supported by the lower layers of particles, leading to progressively greater compression with depth and thickening of sludge. From the settling column test, the limiting solids flux required to reach any desired underflow concentration can be estimated, from which the required tank area can be computed. <br />
<br />
The solids load on the clarifier is estimated in terms of (Q+R)X, while the overflow rate or surface loading is estimated in terms of flow Q only (not Q+R) since the quantity R is withdrawn from the bottom and does not contribute to the overflow from the tank. The secondary settling tank is particularly sensitive to fluctuations in flow rate and on this account it is recommended that the units be designed not only for average overflow rate but also for peak overflow rates. Beyond an MLSS concentration of 2000 mg/l the clarifier design is often controlled by the solids loading rate rather than the overflow rate. The recommended design values for treating domestic sewage in final clarifiers and mechanical thickeners (which also fall in this category of compression settling) are given in Eddy and Metacalf, (2004).<br />
<br />
'''Sludge Recycle'''<br />
The MLSS concentration in the aeration tank is controlled by the sludge recirculation rate and the sludge settleability and thickening in the secondary sedimentation tank.[[File:Equation_4.102.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br />
<br />
Where:<br> Q<sub>r</sub> = Sludge recirculation rate, m<sup>3</sup>/d,<br>Parameters X and Q have been previously defined in equations 4.100 and 4.101<br><br />
<br />
The sludge settleability is determined by, Sludge Volume Index (SVI) defined as volume occupied in mL by one gram of solids in the mixed liquor after settling for 30 min. If it is assumed that sedimentation of suspended solids in the laboratory is similar to that in sedimentation tank, then X<sub>r</sub> = 106/SVI. Values of SVI between 100 and 150 ml/g indicate good settling of suspended solids. The X<sub>r</sub> value may not be taken more than 10,000 g/m<sup>3</sup> unless separate thickeners are provided to concentrate the settled solids or secondary sedimentation tank is designed to yield a higher value.<br />
<br />
'''Excess Sludge Wasting'''<br><br />
The sludge in the aeration tank has to be wasted to maintain a steady level of MLSS (mixed-liquor suspended solids) in the system. The excess sludge quantity will increase with increasing F/M (Food to microbe ratio) and decrease with increasing temperature. Excess sludge may be wasted either from the sludge return line or directly from the aeration tank as mixed liquor. The latter is preferred as the sludge concentration is fairly steady in that case. The excess sludge generated under steady state operation may be estimated by;<br />
<br />
[[File:Equation4.103.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br />
<br />
All parameters in equation (4.103) have been previously defined.<br />
<br />
Some important definition in as far as activated sludge is concerned;<br />
Floc –clumps of bacteria<br />
Flocculation–agitating wastewater to induce the small, suspended particles to bunch together into heavier particles (floc) and settle out.<br />
Loading -a quantity of material added to the process at one time<br />
MLVSS –volatile mixed-liquor suspended solids<br />
Mixed liquor –activated sludge mixed with raw wastewater Package plant –pre-manufactured treatment facility small communities or individual properties use to treat wastewater<br />
SRT –solids retention time<br />
Sludge –the solids that settle out during the process<br />
Supernatant –the liquid that is removed from settled sludge. It commonly refers to the liquid between the sludge on the bottom and the scum on the surface.<br />
TSS –total suspended solids<br />
Wasting –removing excess microorganism’s small package plants being used today<br />
<br />
=====Trickling Filters=====<br />
A trickling filter is an attached growth process i.e. process in which micro-organisms responsible for treatment are attached to an inert packing material. Packing material used in attached growth processes include rock, gravel, slag, sand, redwood, and a wide range of plastics and other synthetic materials. Figure 4 .51 presents high rate trickling filter which has been adapted from https://edurev.in<br />
<br />
[[File:Fig_4.51.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.51: High Rate Trickling Filter<br />
<br />
'''Types of Filters'''<br> <br />
Trickling filters are classified as high rate or low rate, based on the organic and hydraulic loading applied to the unit. Table 4 .37 presents comparison of low and high rate filters.<br><br />
Table 4.37: Comparison of LRTF and HRTF (Source:Tchobanoglous et al., 2003)<br />
[[File:Table_4.37.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
'''Key features'''<br><br />
(a) The hydraulic loading rate is the total flow including recirculation applied on unit area of the filter in a day, while the organic loading rate is the 5 day 20°C BOD, excluding the BOD of the recirculant, applied per unit volume in a day.<br> <br />
(b) Recirculation is generally not adopted in low rate filters.<br> <br />
(c) A well operated low rate trickling filter in combination with secondary settling tank may remove 75 to 90% BOD and produce highly nitrified effluent. It is suitable for treatment of low to medium strength domestic wastewaters.<br> <br />
(d) The high rate trickling filter, single stage or two stage are recommended for medium to relatively high strength domestic and industrial wastewater. The BOD removal efficiency is around 75 to 90% but the effluent is only partially nitrified.<br><br />
(e) Single stage unit consists of a primary settling tank, filter, secondary settling tank and facilities for recirculation of the effluent. Two stage filters consist of two filters in series with a primary settling tank, an intermediate settling tank which may be omitted in certain cases and a final settling tank.<br> <br />
<br />
'''Process Design'''<br><br />
[[File:Fig_4.52.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.52: Flow Sheet of a Trickling Filter System<br><br />
(Source: https://www.chegg.com)<br><br />
<br />
Generally trickling filter design is based on empirical relationships to find the required filter volume for a designed degree of wastewater treatment.<br> <br />
<br />
Types of equations:<br><br />
(a) NRC equations (National Research Council of USA);<br><br />
(b) Rankins equation;<br><br />
(c) Eckenfilder equation and<br><br />
(d) Galler and Gotaas equation.<br><br />
<br />
NRC and Rankin's equations are commonly used. NRC equations give satisfactory values when there is no re-circulation, the seasonal variations in temperature are not large and fluctuations with high organic loading. Rankin's equation is used for high rate filters.<br><br />
<br />
NRC equations: These equations are applicable to both low rate and high rate filters. The efficiency of single stage or first stage of two stage filters, E<sub>2</sub>is given by<br><br />
<br />
[[File:Equation_4.104.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br />
<br />
For the second stage filter, the efficiency E3 is given by<br><br />
<br />
[[File:Equation_4.105.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br />
<br />
Where:<br><br />
E<sub>2</sub>= % efficiency in BOD removal of single stage or first stage of two-stage filter,<br> <br />
E<sub>3</sub>=% efficiency of second stage filter, <br><br />
F<sub>1.BOD</sub>= BOD loading of settled raw sewage in single stage of the two-stage filter in kg/d,<br> <br />
F<sub>2.BOD</sub>= F1.BOD(1- E2) = BOD loading on second-stage filter in kg/d, <br><br />
V<sub>1</sub>= volume of first stage filter, m<sub>3</sub>;<br> <br />
V<sub>2</sub>= volume of second stage filter, m<sub>3</sub>;<br> <br />
Rf<sub>1</sub>= Recirculation factor for first stage,<br> <br />
R<sub>1</sub>= Recirculation ratio for first stage filter, <br><br />
Rf<sub>2</sub>= Recirculation factor for second stage,<br> <br />
R<sub>1</sub>= Recirculation ratio for second stage filter.<br><br />
'''Rankin’s equation''': This equation also known as Tentative Method of Ten States USA has been successfully used over wide range of temperature. It requires the following conditions to be observed for single stage filters:<br><br />
*Raw settled domestic sewage BOD applied to filters should not exceed 1.2 kg BOD<sub>5</sub>/day/ m<sup>3</sup> filter volume.<br><br />
* Hydraulic load (including recirculation) should not exceed 30 m<sub>3</sub>/m<sub>2</sub> filter surface-day.<br><br />
* Recirculation ratio (R/Q) should be such that the BOD entering filter (including recirculation) is not more than three times the BOD expected in effluent. This implies that as long as the above conditions are satisfied efficiency is only a function of recirculation and is given by:<br><br />
[[File:Equation_4.106.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]] <br />
<br />
Where;<br><br />
R = Total recirculation ratio of filer beds in Trickling filters<br><br />
Q = flow rate<br><br />
'''Tertiary Treatment'''<br><br />
The treatment units that fall under this treatment level are CWs, Sludge dewatering beds and Roughing filters. The design steps for CW and sludge dewatering bed follow those described under DEWATS in Section 4.2.<br />
<br />
==Design guidelines for School WASH facilities==<br />
===Overview===<br />
The Schools Water, Sanitation and Hygiene (SWASH) mapping survey conducted in 2009) in all primary and secondary schools in 16Districts of Tanzania indicated that the pertinent water, sanitation and hygiene situation is very poor. Only 11% of the schools surveyed met the national standard of 20 girls and 25 boys per drop hole. Twenty percent of the schools have more than 100pupils per drop hole and 6% of schools have no latrines at all. It was also found that 96% of schools do not have facilities that are suitable or accessible to children with disabilities. Furthermore, around 40% of latrines have doors (however, these do not always guarantee privacy) and very few have hygienic facilities such as soap (1%) or sufficient water for hand-washing (8%) and just 7% of the latrines were free from smell or soiling. Regarding water supply, 62% of the schools in these Districts reported to have access to piped or other protected water supply options. However, some schools that reported having access to piped water or other protected water supply options do not have water on a regular basis and not all of these schools actually have the water supply sources within the school premises.<br />
<br />
The overall picture from the SWASH mapping indicates that most of the schools are characterized by a non-existent or insufficient water supply, poor sanitation and lack of hand-washing facilities. In other cases, facilities do exist but many are broken, unhygienic or unsafe. Moreover, SWASH facilities (e.g. latrines) in most schools do not reflect the needs of girls, pre-primary school children and children with disabilities. There is a risk of low school attendance of girls (during their menstruation period) due to poor sanitation and hygiene facilities, denying them the necessary privacy and the right of getting education like their counterpart (boys).<br />
===Design Considerations and Procedures===<br />
This design manual recommends that anyone who wishes to design WASH in schools should refer to the National Guideline for Water, Sanitation and Hygiene For Tanzania Schools which was published by the Ministry of Education, Science and Technology in 2016 available at https://www.unicef.org/tanzania/reports/national-guideline-water-sanitation-and-hygiene-tanzania-schools<br />
<br />
==Design Guidelines for Health Care WASH Facilities==<br />
===Introduction===<br />
Recently, the provision of improved water, sanitation and hygiene (WASH) services in health care facilities (HCFs) has attracted the attention of governments, Development Partners (DPs) and the international public health institutions. This is due to the fact that, although HCFs provide essential medical care to the sick, most of them especially in DC lack basic WASH services and thus compromising their ability to provide quality health care and consequently posing serious health risks not only to people who seek treatment but also to health care workers (HCWs) and careers. <br />
<br />
There are numerous consequences of poor WASH services in HCFs. Several studies have revealed that, due to inadequate provision of WASH services, patients are potentially at higher risk of developing health care associated infections (HCAIs). The risk of infection is particularly high in new-borns leading to sepsis which in most cases is fatal. The risks associated with sepsis are reported to be 34 times greater in DC. Further, lack of adequate WASH services may discourage women from giving birth in HCFs or causing delays in care-seeking. Therefore, addressing the inadequate provision of WASH services in HCFs will not only improve the quality of care but also attract many people to seek care including delivery services to pregnant women and most importantly contribute in the prevention of HCAIs<br />
===Design Considerations and Procedures===<br />
Any user of this manual who would wish to design, construct and operate and maintain WASH in health care facilities is encouraged to consult the National Guidelines for Water, Sanitation and Hygiene in HealthCare Facilities which was prepared and published by Ministry Of Health, Community Development, Gender, Elderly and Children (MoHCDGEC) of the URT in 2017. The guidelines may be accessed through https://washmatters.wateraid.org/publications/national-guidelines-for-wash-services-in-health-care-facilities-in-tanzania<br><br />
Overall, these guidelines have put in place a uniform and harmonized approach in the provision of WASH services in public and private HCFs all over the country. Specifically, they offer practical guidance for planning and budgeting as well as technical designing and construction of recommended WASH facilities, operation and maintenance (O&M), and monitoring of the performance of the services.<br />
<br />
==Design Guidelines/Options for Small Towns or Emerging Towns==<br />
<br />
===Characteristics of Small Towns in Tanzania===<br />
a/ Start as settlements and grow uncontrollably<br><br />
b/ Not Planned<br><br />
c/ Combination of small businesses and mainly agrarian economy<br><br />
d/ Low capital to implement large projects<br><br />
e/ Low level infrastructure for water and sanitation<br><br />
f/ More of community supply systems than in-house<br><br />
g/ Combination of sources (shallow wells, surface sources and piped water systems)<br><br />
h/ Mainly pit latrines of different kinds <br><br />
i/ Higher percentages of dry type of sanitation than wet sanitation (For example Babati Town Council has 61.9% dry and 32.9% wet facilities1) <br><br />
<br />
===Guidelines for Water Supply in Small Towns===<br />
<br />
a/ Identify water supply schemes that are community based and demand driven<br><br />
b/ Provide appropriate and affordable technology. Remember that the cost of technology includes also the operation and maintenance costs of the technology.<br> <br />
c/ Standardize technology <br><br />
d/ Supplement water supply with alternatives sources such as rainwater harvesting (Refer to Volume 1 Chapter 3 sections 3.2.1, 3.6.1 and Chapter 9 section 9.1.6).<br><br />
<br />
===Guidelines for Sanitation Services in Small Towns===<br />
a/ Provide guidance on sitting of sanitation facilities in relation to water sources. Consider the geology of the area, soil type )<br><br />
b/ Plan and provide systems for dealing with on-site sanitation facilities (sludge collection from septic tank, pit latrines, transportation of sludge and acceptable disposal facility)<br><br />
c/ Designate appropriate areas for managing FS<br><br />
d/ Provide a FS treatment facility that is reasonably placed to minimize sludge transport costs.(Refer Section 3.2.6)<br><br />
e/ Consider a decentralised wastewater treatment systems (DEWATS) Section 4.2<br><br />
f/ Include possibilities of recovery of useful materials (biogas, nutrients, briquettes made from dried sludge and water)<br><br />
<br />
==Sanitation Resources Recovery and Reuse==<br />
===Introduction===<br />
Ideally, both wastewater and FS should be seen as a resource that can be recovered, rather than a waste that needs to be managed and disposed of. With adequate collection and treatment, wastewater and FS can be transformed into products that can be sold and utilized. For example, water, organic matter, and nutrients in FS can be beneficial for soil properties and plant growth. The organic matter is beneficial for water retention, which can increase water-holding capacity and reduce the effects of drought, reduce soil erosion, and benefit the soil microbial community. It is important to consider the protection of public health, as well as public perception, with the use of recycled products. For safe resource recovery by end-users, it is important that pathogen levels are adequately controlled for the intended end-use, for example commercially available compost versus industrial fuel. Similarly, considering social acceptance of the product by the intended market is critical, for example selling FS briquettes to individuals as a household cooking fuel, as opposed to industrial customers. Error: Reference source not foundshows a typical process flow sheet of wastewater treatment that includes resource recovery. The units are defined in general terms for example the bio-reactor can be any of the biological contacting systems discussed in the previous sections such as bio-digesters for biogas, activated sludge process, oxidation ponds etc. The type of actual units depends on the feed concentration of organics, what needs to be recovered and the use of the recovered components<br><br />
[[File:Fig_4.53.PNG|600px|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.53: Example of Wastewater Treatment Process Flow Sheet with Resource Reuse/Recovery<br> <br />
===Fecal Sludge Treatment End Products===<br />
Resource recovery can be from both the solid and liquid fractions of FS. The types of treatment products will depend on the initial characteristics and on the treatment technologies. Examples of established forms of resource recovery include dewatered or dried sludge produced from unplanted drying beds for land application; co-composting of FS and organic solid waste; plants from planted drying beds (see section 3.2.2-FSM); deep-row entrenchment of untreated FS; or effluent from waste stabilization ponds used for irrigation or in aquaculture. Recovered products or resources include biogas from the anaerobic digestion of faecal, larvae from the treatment with black soldier fly and carbonization of FS. Figure 4.54 shows level of FS treatment technologies and the corresponding recoverable resources or end-products.<br><br />
[[File:Fig_4.55.PNG|600px|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.55: Level of Establishment of FS Treatment Technologies and the Corresponding End-Products (Source: Linda and Miriam, 2018)<br />
===Application===<br />
Another way to think about resource recovery is by the actual resource that it provides, which is especially useful when thinking about the potential market demand. Recovered products can also be further processed to increase their market value. For example, further processing of char into briquettes that are suitable for recovery of its energy in institutions, or pelletizing of compost or dewatered (dried) sludge for easier transport. Table 4.38 presents a summary of the potential resources and the end products.<br />
</div><br />
Table 4.39: Summary of the Potential Resources and the Recoverable Products<br />
[[File:Table_4.39.PNG|600px|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
(Source: Schoebitz, et al., 2016)<br />
===Suitable FS Characteristics for Resource Recovery===<br />
<div style='text-align: justify'><br />
Different characteristics of wastewater and FS will affect the quality of the end-product, and will need to be evaluated to ensure that they meet market needs, and also to protect public and environmental health. Therefore, the multi-barrier approach (see Guidelines on sanitation and health. WHO, 2018 and MoW Water Safety Guidelines, 2015) can be used to protect public and environmental health when using FS as a treatment product. Figure 4.56 shows process flow diagram of the FS treatment.<br><br />
[[File:Fig_4.57.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.57: Process Flow Diagram of the FS treatment (Source: Englund and Strande, 2019)<br><br />
Key:<br><br />
1. Feeding Tank<br><br />
2. Biogas Digester<br><br />
3. Stabilization Tank<br><br />
4. Planted Sludge Drying Bed<br><br />
5. Anaerobic Baffle Reactor and Anaerobic Filter<br><br />
6. Planted Gravel Filter<br><br />
<br />
'''Land application'''<br><br />
Nutrients such as nitrogen, phosphorus and potassium are essential for plant growth and important for the use of effluent for irrigation, and as a soil conditioner, compost or fertilizer. Heavy metals, such as cadmium, lead and zinc, and salinity are important as they can be toxic to plants and people. Indicators of pathogens for both liquid and solid streams ensure that resource recovery adequately protects public health. Error: Reference source not found shows an example of a banana field irrigated by treated water.<br><br />
[[File:Fig_4.58.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.58: Banana Field Irrigated by Treated Wastewater at NM-AIST, Arusha Tanzania<br />
<br />
'''Solid fuels'''<br><br />
A calorific value is a measure of the energy content of a fuel, and is important for the characterization of solid fuel. Ash content is a metric of the non-combustible, inorganic fraction contained in FS, and it does not contribute to the calorific value. It needs to be disposed of, or used for phosphorus recovery. Indicators of pathogens are important depending on the final end-use, and risks need to be managed with a multi-barrier approach.<br />
<br />
===Biogas===<br />
Fractions of methane and carbon dioxide are important parameters for biogas, as higher methane and lower carbon dioxide concentrations increase the fuel potential.<br />
<br />
===Animal feed===<br />
Protein, fat and mineral contents are important for the use of insect larvae and plants as animal feed. Indicators of pathogens are important to ensure that no pathogens are transmitted to animals. <br />
<br />
===Treatment Technologies for Sanitation Resource Recovery and Re-use===<br />
The treatment technology options for resources recovery and re-use is presented in Figure 4.31.<br />
<br />
[[File:Fig_4.59.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
<br />
Figure 4.59: FST Plant Layout and Flow Diagram (Source: Linda et al., 2018)<br><br />
<br />
The preparation for dewatered faecal sludge cake is presented in figure 4.32<br />
<br />
[[File:Fig_4.60.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br><br />
Figure 4.60: Preparation of the Dewatered Sludge Cakes in Faridpur, Blangladesh, Prior to Transportation to the Nearby Co-composting Plant (Source: Linda et al., 2018)<br><br />
===Design Procedures for Treatment Technologies for Resources Recovery===<br />
The design procedures for treatment technologies meant for sanitation resource recovery and re-use follow those under FSM and DEWAT sections in this manual. The user of this manual is thus advised to refer to these sections for the relevant design procedures.<br />
<br />
==Safeguarding of Sanitation Infrastructure==<br />
Given the reality of impacts of climate change to WASH infrastructure and the fact that the 3rd Edition of Design Manual didn't take into account climate resilience, this current edition has attempted to factor in the design of WASH infrastructure. The design manual takes into account the dynamic of weather extreme events as articulated in section 2.4. Specifically, the manual takes into account climate resilience issues into WASH infrastructure design into the following components; intake location (when considering combined systems) and its operation, the sitting and construction of wastewater and FS treatment facilities as well as collection/transmission lines from the waste generation points. It is envisaged that the user of this manual will find it useful. They are encouraged to critically and thoroughly take on board climate change issues into design of WASH infrastructure.<br><br />
<br />
==Application Software==<br />
===Recommended Software===<br />
The common software in use in sanitation projects include the following:<br><br />
(a) SewerCAD- an easy-to-use sanitary sewer modelling and design software product that thousands of municipalities, utilities, and engineering firms around the world trust to design, analyse, and plan wastewater collection systems.<br><br />
(b) STELLA-stands for Structural Thinking Experimental Learning Laboratory with Animation. It is the ecological definitive modelling tool to create professional simulations. It seamlessly create, design and publish models to share with anyone, anywhere, anytime. The software package creates diagrams, charts, and uses animation to help in the discovery of relationships between variables and helps simplify model building.<br><br />
(c) PC-based simplified sewer design–is a program to aid the design of simplified sewerage systems. It seeks to do this by:<br><br />
* Automating–and thus speeding up the necessary design calculations;<br><br />
* Providing a tool for analyzing different design permutations/configurations; and<br><br />
* Being suitable for training/learning purposes.<br><br />
<br />
==Technical Spreadsheets==<br />
This section has been adapted partly to pages 241-246 in the book Decentralised Wastewater Treatment Systems (DEWATS) and Sanitation in DC 2009, (Gutterer, 2009). A practical guide useful in assisting designers to use spreadsheets for sizing some of the unit operations discussed in Chapter 4.The purpose of this section is to provide the engineer with an example of a tool to produce own spreadsheets for sizing DEWATS in any computer programme that he/she is familiar with. The exercise of producing one’s own tables will compel engineers to deepen their understanding of design. Computerised calculations can be very helpful, particularly if the formulas and the input data are correct. Flawed assumptions or wrong data, on the other hand, will definitely result in worthless results. It is the duty of the design engineer to ensure that the assumptions made are reasonable and the data entered is correct. For detail explanations on the use of spreadsheet calculations and the limitations, engineers are directed to make reference to chapter 10 of this book (Gutterer, 2009). <br><br />
'''Example: Domestic wastewater quantity and quality'''<br><br />
The spread sheet shown in Table 4:15 helps to define domestic wastewater production and quality in terms of the number of people and the wastewater they discharge. BOD and water-consumption figures vary widely from place to place and, therefore, should be obtained for each site. These figures have been matched with figures used in Tanzania.<br><br />
Formulas of spreadsheet “domestic wastewater production”:<br><br />
E<sub>n</sub> = A<sub>n</sub> x C<sub>n</sub> /1000<br><br />
F<sub>n</sub> = A<sub>n</sub> x B<sub>n</sub> /E<sub>n</sub><br><br />
G<sub>n</sub> = D<sub>n</sub> x F<sub>n</sub><br><br />
where n can be 1, 2, 4 etc<br><br />
Table 4.40: Spreadsheet for Calculation of Quantity and Quality of Domestic-Wastewater Production<br><br />
[[File:Table_4.40.PNG|600px|center|link=Chapter_Four:_Off-Site_Sanitation_Systems]]<br />
</div><br />
'''References'''<br><br />
A.T. Haule, H.B. Pratap, J.H.Y. Katima, T.S.A Mbwette, and K.N. Njau, “Removal From Domestic Wastewater in Subsurface Flow Constructed Wetland by Indigenous Macrophytes in the Tropics. A comparative study of Six Potential Macrophytes in Tanzania. Proc. of 8th IWA International Conference on Wetlland Systems for Water Pollution Control, Arusha Tanzania, September 2002, pp 938-951 <br><br />
<br />
APHA, A., Wpcf.(2012) Standard methods for the examination of water and wastewater. American Public Health Association, Washington.<br><br />
<br />
Ayres R.M., Alabaste, G.P. r, Mara D.D and Lee, D.L (1992): A design equation for human intestinal nematode egg removal in waste stabilization ponds, Water Research, Volume 26, Issue 6, June 1992, Pages 863-865<br><br />
Boot, N.L.D. and Scott, R.E., 2009. FS in Accra, Ghana: problems of urban provision. Water Science and Technology, 60(3), pp.623-631.<br><br />
<br />
Chai, Q., Bakke, R. and Lie, B., 2006. Object-oriented modelling and optimal control of a biological wastewater treatment process. In Proceedings of the Eighth IASTED International Conference on Control and Applications (pp. 218-223). <br><br />
Clay, S., Hodgkinson, A., Upton, J. and Green, M., 1996. Developing acceptable sewage screening practices. Water science and technology, 33(12), pp.229-234.<br><br />
<br />
Cooper,P.F., Job, G.D., Green, M.B.and Shuter, R.B.E.(1996). Reed beds and constructed Wetlands for wastewater treatment W.R.C Swedon, UK.<br><br />
<br />
Foxon, K. M., Pillay, S., Lalbahadur, T., Rodda, N., Holder, F. and Buckley, C. A. (2004). The Anaerobic Baffled Reactor(ABR): An Appropriate Technology for on-Site Sanitation. Water SA 30 (5) (Special Edition).<br><br />
<br />
Gutterer, B., Ulrich, A. and Reuter, S., 2009. Decentralised wastewater treatment systems (DEWATS) and sanitation in DC: a practical guide. BORDA. <br><br />
<br />
Heinss, U., Larmie, S.A. and Strauss, M., 1998. Solids Separation and Pond Systems for the Treatment of FSs in the Tropics. Lessons Learnt and Recommendations for Preliminary Design.<br />
http://www.efm.leeds.ac.uk/CIVE/Sewerage<br />
https://crackleaf.weebly.com/blog/simplified-sewerage-design-software<br />
https://www.bentley.com/en/products/product-line/hydraulics-and-hydrology-software/sewercad<br />
https://www.iseesystems.com/store/products/stella-architect.aspx<br><br />
<br />
Kadlec, R and Wallace, Scott D. (2009). Treatment Wetlands CRC press<br />
Kone, D. and Peter, S., 2014. FS Management, 35. Available at: https://doi. org/10.1017/CBO9781107415324, 4.<br><br />
M.E.Kaseva, T.S.A. Mbwette and J.H.Y. Katima 2002. Domestic Sewage Treatment in a Pilot Plant Composed of Septic Tank and Constructed Wetland System –A case study in Dar es Salaam. Proc/ 8th Proc. of 8th IWA International Conference on Wetland Systems for Water Pollution Control, Arusha, Tanzania, September 2002, <br><br />
<br />
Mara, D., 1996. Low-cost urban sanitation. John Wiley & Sons.<br />
Mara, D., Sleigh, A. and Tayler, K., 2001. DFID PC-based Simplified Sewer Design. <br><br />
<br />
Montangero, A. and Strauss, M., 2002. FS treatment. Eawag/Sandec.<br><br />
<br />
Njau, K.N. Katima, J.H.Y. and Minja, R. 2002. Pumice Soils: A Potential Substrate in Constructed Wetland Treatment Systems. Proc. of 8th IWA International Conference on Wetland Systems for Water Pollution Control, Arusha, Tanzania, September 2002, pp. 290-303.<br><br />
<br />
Schoebitz, L., Andriessen, N., Bollier, S., Bassan, M., & Strande, L. (2016). Market driven approach for selection of FS treatment products. Dübendorf: Eawag.<br><br />
<br />
Sonko, E.H.M., Mbéguéré, M., Diop, C., Niang, S. and Strande, L., 2014. Effect of hydraulic loading frequency on the performance of planted drying beds for the treatment of FS. Journal of water, sanitation and hygiene for development, 4(4), pp.633-641.<br><br />
<br />
Tayler, Kevin 2018. FS and Septage Treatment. A guide for low- and middle-income countries. Practical Action Publishing.<br />
Tchobanoglous, G. Burton, F. L. Stensel, H. D. Metcalf & Eddy Inc. (2003): Wastewater Engineering, Treatment and Reuse. (Fourth Edition). New York: McGraw-Hill Companies, Inc.<br><br />
<br />
Tilley, E., 2014. Compendium of sanitation systems and technologies. Eawag.<br><br />
<br />
Tilley, E., Ulrich, L., Christoph, L., Reymond, P., Schertenleib, R., & Zurbrügg, C. (2014). Compendium of Sanitation Systems and Technologies. IWA; EAWAG; WSSCC. (In particular pp. 78–79). Free PDF available at: www.sandec.ch/compendium<br><br />
<br />
URT (2014). Mwongozo wa Ujenzi wa Vyoo Bora na Usafi wa Mazingira. Ministry of Health and Social Welfare. http://www.moh.go.tz/en/enviromental-health<br><br />
<br />
URT (2018). Guidelines for the Application of Small-Scale, Decentralised Wastewater Treatment Systems: A Code of Practice for Decision Makers. MoW, The United Republic of Tanzania.<br><br />
<br />
Vinnerås, B., Björklund, A. and Jönsson, H., 2003. Thermal composting of faecal matter as treatment and possible disinfection method––laboratory-scale and pilot-scale studies. Bioresource Technology, 88(1), pp.47-54.<br><br />
<br />
W. Mwegoha, J.H.Y. Katima, TSA Mbwette, KN Njau, SE Jorgensen and SN Nielsen: Modelling the Effect of Suspended Solids Accumulation on Hydraulic Conductivity of Gravel Packed Horizontal Sub-Surface Flow Constructed Wetland. Proc. of 8th IWA International Conference on Wetland Systems for Water Pollution Control, Arusha, Tanzania, September 2002,<br />
<br />
<br />
<br />
Previous Page: [[Chapter_Three:_On-Site_Sanitation_Systems|Chapter_Three:_On-Site_Sanitation_Systems]] << >> Next Page: [[Chapter_Five:_Design_Standards_and_Specifications:Chapter_Five:_Design_Standards_and_Specifications]]</div>Jumahttp://design.maji.go.tz/index.php/Preface_VOL.1Preface VOL.12022-07-20T22:57:49Z<p>Juma: </p>
<hr />
<div>==Preface==<br />
<div style="text-align:justify"><br />
<div style="font-size:17px"><br />
The Government of the United Republic of Tanzania, through the Ministry <br />
of Water, oversees the implementation of the Water Supply and Sanitation <br />
projects in the country. The Ministry of Water has published several editions of <br />
the relevant Design Manuals. The First edition was the Water Supply and Waste <br />
Wastewater Disposal Manual of 1985/86. The Second edition was titled “Design <br />
Manual for Water Supply and Wastewater Disposal of 1997”. The Third edition <br />
was titled “Design Manual for Water Supply and Wastewater Disposal of 2009”. <br />
These manuals guided the Ministry and the general public in the planning and <br />
design of water supply and sanitation projects in the country. <br />
<br />
As it is now well over ten years since the Third Edition of the Design manual <br />
was adopted, and since many scientific and technological changes have taken <br />
place, including the conclusion of MDGs and adoption of the SDGs in 2015 as <br />
well as useful lessons learnt out of implementation of the WSDP I and WSDP <br />
II (which is still on-going), it has become necessary to revise the 2009 design <br />
manual. Notably, the 3rd Edition Design Manual has, among other things, limited <br />
coverage on the impact of climate change, application software and sanitation <br />
management issues.<br />
<br />
The Ministry is now at various stages of instituting policy and legal reforms that <br />
are deemed necessary for futuristic improvement in the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in Tanzania. Therefore, the 4th Edition of the Design, Construction Supervision, <br />
Operation and Maintenance (DCOM) Manual will make invaluable contribution <br />
in this regard. It is important to recall that the Government has established <br />
the Rural Water Supply and Sanitation Agency (RUWASA), which is responsible <br />
for the supervision, execution and management of rural water supply and <br />
sanitation projects. RUWASA is expected to improve the existing responsibility <br />
and accountability in the management of water and sanitation services in rural <br />
areas. The 4th Edition DCOM Manual will support the sector development and <br />
implementation institutions (including RUWASA, Water Supply and Sanitation <br />
Authorities, development partners, and civil society organisations), and will <br />
provide valuable information relating to implementation of water supply and <br />
sanitation projects in their various stages, from pre-feasibility and feasibility <br />
studies, to planning, designing, construction supervision and operation and <br />
maintenance. <br />
<br />
It is expected that the 4th Edition of the DCOM Manual will position the Ministry <br />
well to systematically and comprehensively implement the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in order to ensure the sustainability of water supply and sanitation projects in <br />
the country. This is also expected to contribute in realising the water sector’s <br />
contribution towards achieving the Tanzania Development Vision 2025, as well as <br />
the various national and international commitments and milestones in the water <br />
sector as also specified in the Agenda 2063 in the "Africa that we want" and the <br />
Sustainable Development Goals (SDGs) on water and sanitation (SDG No. 6). <br />
<br />
The preparation of this Water Supply and Sanitation Projects DCOM Manual <br />
required contributions in form of both human and financial resources. The <br />
Ministry of Water, therefore, takes this opportunity to thank the members of <br />
the Special Committee for Reviewing and Updating the 3rd Edition of the Design <br />
Manual for Water Supply and Wastewater Disposal of 2009, specifically for their <br />
efforts in preparation of this comprehensive 4th Edition of the DCOM Manual. <br />
Thanks are also due to the World Bank for financing the major part of the activities, <br />
and to all others who contributed in the preparation of this new DCOM Manual.<br />
<br />
In the future, the Ministry plans to periodically review and update the DCOM <br />
Manual in order to keep in pace and address emerging changes in policy and <br />
societal needs, emerging technologies, and sustainability concerns in the <br />
implementation of water supply and sanitation projects in the country. <br />
<br />
[[Image:MakameSignature.png|632px|link=DCOM_Volume_I]] <br><br />
<br />
<br />
Next Page: [[Acknowledgements_VOL.1]]<br />
</div><br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Subject_Index_:_Subject_IndexSubject Index : Subject Index2022-07-20T20:48:46Z<p>Juma: </p>
<hr />
<div>'''Subject Index'''<br />
<br />
[[File:I1.PNG|center|700px]]<br />
[[File:I2.PNG|center|700px]]<br />
[[File:I3_2.PNG|center|700px]]<br />
[[File:I4.PNG|center|700px]]<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 9|Appendix 9: Solar Arrays and Accessories Inspection Checklist]]</div>Jumahttp://design.maji.go.tz/index.php/Subject_Index:_Subject_IndexSubject Index: Subject Index2022-07-20T17:02:52Z<p>Juma: </p>
<hr />
<div>[[File:Subject_index.png|600px|link=Subject_Index:_Subject_Index]]<br><br />
<br />
<br />
Previous Page: [[Chapter_Six:_Stakeholder's_Participation_in_Design_of_Sanitation_Projects|Stakeholder's Participation in Design of Sanitation Projects]]</div>Jumahttp://design.maji.go.tz/index.php/References_IVReferences IV2022-07-20T14:03:55Z<p>Juma: /* REFERENCES */</p>
<hr />
<div>= References=<br />
<br />
Brikkè, F. (2000). Operation and Maintenance of rural water supply and sanitation systems. A training package for managers and planners. Malta: IRC International Water and Sanitation Centre and World Health Organisation.<br />
<br />
Brikke, F. and Bredero, M. (2003): Linking Technology Choice with Operation and Maintenance in the context of community water supply and sanitation. A reference Document for Planners and Project Staff. Geneva: World Health Organization and IRC Water and Sanitation Centre.<br />
<br />
Carter, R. C. (2009). Operation and Maintenance of Rural Water Supplies. In: Perspectives N° 2. St. Gallen: Rural Water Supply Network (RWSN).<br />
<br />
Castro, V. Msuya, N. and Makoye, C. (2009). Sustainable Community Management of Urban Water and Sanitation Schemes (A Training Manual). Nairobi: Water and Sanitation Program-Africa, World Ban.<br />
<br />
Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. New York: The McGraw-Hill Companies Inc.<br />
<br />
DfID (1998). Guidance Manual on Water Supply and Sanitation Programmes. London: Water, Engineering and Development Centre (WEDC) for the Department for International Development (DFID).<br />
<br />
EAWAG/SANDEC (2008). Faecal Sludge Management. Lecture Notes. (Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC).<br />
<br />
EWURA (2014). Water quality and wastewater quality monitoring guidelines.<br />
<br />
GoI (2013). Operation and maintenance manual for rural and water supplies. Government of India (GoI), Ministry of drinking water and sanitation.<br />
<br />
HELVETAS (n.y). Village Water Supply. Caretakers Manual. Bamenda: Helvetas Cameroon URL: https://sswm.info/sites/default/files/reference_attachments/HELVETAS%204000%20Village%20Water%20Supply.pdf [Accessed: 09.02.2020].<br />
https://mof.go.tz/mofdocs/msemaji/Five%202016_17_2020_21.pdf.<br />
<br />
Kresic, N. (1997). Hydrogeology and groundwater modeling. 2nd edition, CRC Press,828p.<br />
<br />
MALCOLM N. SHAW 2008, International Law, Sixth edition, Cambridge University Press, Cambridge Uk.<br />
<br />
Mang, H. P. (2005). Biogas Sanitation Systems. (Ecological sanitation course). Beijing: Chinese Academy of Agricultural Engineering.<br />
<br />
Mbwette, T.S.A, Jorgensen, S.E; Katima, J.H.Y, Njau, K. H, Kayombo, S. (Eds) 2002. Proc. 8th IWSA International conference on Westland system for water pollution control. Arusha, Tanzania, Vol.1&2.<br />
<br />
Meuli, C. and Wehrle, K. (2001). Spring Catchment. (Series of Manuals on Drinking Water Supply, 4). St. Gallen: Swiss Centre for Development Cooperation in Technology and Management (SKAT) URL: http://skat.ch/book/spring-catchment/ [Accessed: 08.02.2020] <br />
<br />
NETSSAF (2008). NETSSAF Participatory Planning-Approach. A tutorial for sustainable sanitation planning. Network for the Development of Sustainable Approaches for Large Scale Implementation of Sanitation in Africa (NETSSAF).<br />
NSGRP II & III<br />
<br />
Pradhikaran, M.J. (2012). Module 2 Operation and Maintenance of Water Supply System. Training Module for Local Water and Sanitation Management, CEPT University, India.<br />
<br />
Rocha Loures F & Rieu-Clarke A (eds) (2013). The UN Watercourese Convention in Force: Strengthening international law for transboundary water management. Earthscan, Routledge.<br />
<br />
Sasse, L. (1988). Biogas Plants. German Appropriate Technology Exchange (GATE) and German Agency for Technical Cooperation (GTZ) GmbH.<br />
<br />
SIWI (2015). International water law. Retrieved from: https://www.siwi.org/icwc-course-international-water-law<br />
<br />
UNEP (1998). Sourcebook of Alternative Technologies for Freshwater Augmentation in Some Countries in Asia (Technical Publication). Osaka/Shiga: United Nations Environmental Programme. International Environmental Technology Centre URL: http://www.unep.or.jp/ietc/publications/techpublications/techpub-8e/artificial.asp [Accessed: 07.02.2020]<br />
<br />
UNEP (2004). Chapter 4. Wastewater Technologies. In: UNEP (2004): A Directory of Environmentally Sound Technologies for the Integrated Management of Solid, Liquid and Hazardous Waste for SIDS in the Caribbean Region.<br />
<br />
UNFCC (2015). Paris Agreement on climate change 2015. Retrieved from: https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement<br />
<br />
UNFCCC (2015). Paris Agreement. United Nations Framework Convention on Climate Change (UNFCCC). <br />
<br />
United Nations (2015). Helping governments and stakeholders make the Sustainable Development Goals (SDGs) a reality. Retrieved from: https://sustainabledevelopment.un.org/<br />
URL: http://www.who.int/water_sanitation_health/publications/linking-technology-choice-with-o-m-in-ws/en/ [Accessed: 07.02.2020].<br />
<br />
URT (2000). The Tanzania Development Vision 2025. Ministry of Finance and Planning. https://www.mof.go.tz/mofdocs/overarch/vision2025.htm.<br />
<br />
URT (2002). The National Water Policy (NAWAPO). United Republic of Tanzania (URT).<br />
<br />
URT (2008). The National Water Sector Development Strategy (NWSDS). United Republic of Tanzania.<br />
<br />
URT (2014). Guidelines for Construction of Toilets and Sanitation. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br />
<br />
URT (2016). Five Year Development Plan (FYDP II), 2016/17 – 2020/21. Ministry of Finance and Planning. Retrieved from: https://mof.go.tz/mofdocs/msemaji/Five%202016_17_2020_21.pdf<br />
<br />
URT (2016). The National Guidelines for Water, Sanitation and Hygiene for Tanzania Schools. Ministry of Education, Science and Technology (MoEST).<br />
<br />
URT (2016). The Second Five Year Development Plan (FYDP II), 2016/17 – 2020/21. Ministry of Finance and Planning.<br />
<br />
URT (2017). National Guidelines for Water, Sanitation and Hygiene in Health Care Facilities. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br />
<br />
URT (2018b). Challenges of Implementation of Rural Water Supply Projects and Services in Tanzania: Findings of A Special Audit Committee. Final Report, Volume II: The Main Report. MoW.<br />
<br />
URT (January 2018). National (Tanzania) guideline on drinking water quality monitoring and reporting. Volume I. Ministry of Water. The United Republic of Tanzania (URT).<br />
<br />
URT (July, 2019). Water sector development programme; Guide line for good environmental and social practises (GGESP) revised version. Ministry of Water.<br />
<br />
URT (July, 2019). Water sector development programme; Guide line for good environmental and social management framework (ESMF) revised version. Ministry of Water.<br />
<br />
URT (October, 2015a). Guidelines for the preparation of water safety plans, resilient to climate change for rural water supply services. Ministry of Water.<br />
<br />
URT (October, 2015b). Guidelines for the preparation of water safety plans, resilient to climate change for urban water supply utilities. Ministry of Water.<br />
<br />
WHO (1996). Rapid Sand Filtration. (Fact Sheets on Environmental Sanitation, 2 / 14). Geneva: World Health Organization (WHO). <br />
Wolf 1999, cited in https://www.siwi.org/icwc-course-international-water-law/ visited on 08, March ,2020.<br />
<br />
World Bank (2010). Water and Sanitation Public- Private Partnership Legal Resource Centre. https://ppp.worldbank.org/public-private-partnership/sector/water-sanitation<br />
<br />
World Bank (2012). Rural water supply. Volume III: Operation and maintenance Manual. The World Bank Office, Manila, Philippines.<br />
<br />
'''Internet Links'''<BR><br />
'''1. Operation and Maintenance of Water Supply Projects'''<br><br />
a) https://www.ircwash.org/sites/default/files/202.6-93MA-11116.pdf<br><br />
b) http://documents.worldbank.org/curated/en/696331468144565653/Operation-and-maintenance-manual) accessed 03022020<br><br />
c) https://www.cmpethiopia.org/content/download/636/3335/file/Operation%20and%20Maintenance%20Manual%20for%20Urban%20Water%20Utilities.pdf <br><br />
d) http://skat.ch/wp-content/uploads/2018/12/Handbook_FINAL_APRIL_KDA.pdf<br><br />
e) IRC- https://www.ircwash.org/sites/default/files/202.6-89MA-12188.pdf<br><br />
f) http://www.gdrc.org/uem/water/wb-urbanwater.html <br><br />
g) https://www.jica.go.jp/english/our_work/thematic_issues/water/c8h0vm0000ammjc9-att/study_04.pdf , JICA;<br><br />
h) SSWM- https://www.sswm.info/planning-and-programming/ensuring-sustainability/ensure-sustainability/operation-and-maintenance<br><br />
i) https://www.slideshare.net/esmeraldoerandio/rural-water-supply-volume-iii-operation-and-maintenance-manual-PHILLIPINES<br><br />
j) https://www.mwe.go.ug/sites/default/files/library/WSDF%20Operations%20Manual.pdf<br><br />
k) https://www.unicef.org/publications/files/CFS_WASH_E_web.pdf<br><br />
l) http://cpheeo.gov.in/cms/manual-on-operation--and-maintenance-of-water-supply-system-2005.php<br><br />
m)https://phedharyana.gov.in/WriteReadData/WSSO/Manuals/Manual%20of%20Operation%20and%20Mtc%20CPHEEO%20Govt%20of%20India.pdf <br><br />
n) https://www.wateraid.org/mw/sites/g/files/jkxoof331/files/2019-10/Operation%20and%20Maintenance%20Manual%20for%20WaterAid%20Eswatini.docx <br />
<br />
'''2. O&M of Sanitation/Wastewater Projects'''<br><br />
a) https://akvopedia.org/wiki/O%26M_sanitation<br><br />
b) https://sswm.info/humanitarian-crises/urban-settings/hygiene-promotion-community-mobilisation/important/ensuring-appropriate-operations-and-maintenance-services<br><br />
c) https://sswm.info/planning-and-programming/ensuring-sustainability/ensure-sustainability/operation-and-maintenance<br><br />
d) https://www.wecf.eu/download/2011/October/2-939-susana-factsheet-wg10-version-5-july-2011.pdf?m=1319642173&<br><br />
e) https://www.cenntech.com/library/ultrafiltration.htm.vis.12.01.2020<br><br />
f) https://www.en.wikipedia.org/wiki/nanofiltartion.vis.12.01.2020<br><br />
g) https://www.cenntech.com/microfiltration-and-ultrafiltration.htm.vis.12.01.2020<br><br />
h) https://www.samtech.com/how-to-choose-the-best-microfiltration-and-ultrafiltration-system-for-your-facility,vis.12.01.2020<br><br />
i) https://www.crystalquest.com/pages/whats-is-ultrafiltration,vis.12.01.2020<br />
<br />
<br />
<br />
Previous Page: [[Chapter Nineteen: Community Participation and Compliant Redressal System in Operation and Maintenance of Water Supply and Sanitation Projects]] << >> Next Page: [[DCOM Volume IV Appendix 1|Appendix 1: Maintenance of Different Types of Boreholes ]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_9DCOM Volume IV Appendix 92022-07-20T13:47:34Z<p>Juma: </p>
<hr />
<div>'''Appendix 9: Solar Arrays and Accessories''' <br />
[[File:9.png|700px|center]]<br />
[[File:9i.png|700px|center]]<br />
<br />
<br />
'''Table A.9c: Array Installation and Wiring'''<br />
<br />
[[File:9ii.PNG|700px|center]]<br />
[[File:9iii.PNG|700px|center]]<br />
[[File:9iv.PNG|700px|center]]<br />
[[File:9v.PNG|700px|center]]<br />
[[File:9vi.PNG|700px|center]]<br />
[[File:9vii.PNG|700px|center]]<br />
[[File:9viii.PNG|700px|center]]<br />
[[File:9vix.PNG|700px|center]]<br />
[[File:9x.PNG|700px|center]]<br />
[[File:9xi.PNG|700px|center]]<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 8|Appendix 8: Troubleshooting for Hand Pumps]] << >> Next Page: [[Subject_Index_: Subject Index]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_10DCOM Volume IV Appendix 102022-07-20T12:43:30Z<p>Juma: </p>
<hr />
<div>'''Appendix 9: Solar Arrays and Accessories Inspection Checklist'''<br />
[[File:Appendex_9_volume_4.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.13.PNG|center|500px]]<br />
<br />
<div style="text-align:center"><br />
'''Table A.9b: Solar Modules'''</div><br />
[[File:Appendex_9_volume_4.3.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.4.PNG|center|500px]]<br />
<br />
[[File:Appendex_9_volume_4.5.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.6.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.7.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.8.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.9.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.10.PNG|center|500px]]<br />
[[File:Appendex_9_volume_4.11.PNG|center|500px]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_8DCOM Volume IV Appendix 82022-07-20T12:23:46Z<p>Juma: </p>
<hr />
<div>'''Appendix 8: Troubleshooting for Hand Pumps'''<br />
<br />
Following are major problems that may occur in use of hand pumps, possible causes and suggestive remedies:<br />
<br />
[[File:Appendix8.png|center|700px]]<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 7|Appendix 7: Jet Pumps and Their Troubleshooting]] << >> Next Page: [[DCOM Volume IV Appendix 9|Appendix 9: Solar Arrays and Accessories Inspection Checklist]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_7DCOM Volume IV Appendix 72022-07-20T12:18:33Z<p>Juma: </p>
<hr />
<div>'''Appendix 7: Jet Pumps and Their Troubleshooting'''<br />
<br />
The troubleshooting information for jet pump problems is presented in matrix below.<br />
<br />
[[File:Appendix7.png|center|700px]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 6|Appendix 6:Centrifugal Pumps and Their Troubleshooting]] << >> Next Page: [[DCOM Volume IV Appendix 8|Appendix 8: Troubleshooting for Hand Pumps]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_6DCOM Volume IV Appendix 62022-07-20T12:12:00Z<p>Juma: </p>
<hr />
<div>'''Appendix 6: Centrifugal Pumps and Their Troubleshooting'''<br />
<br />
A typical centrifugal pump and its component parts are shown below: <br />
[[File:Appendix6.png|center|500px]]<br />
(Source: World Bank, 2012)<br />
<br />
Other common problems and their remedies are summarized in the matrix below:<br />
[[File:Appendix6i.png|center|700px]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 5|Appendix 5: Details of a Submersible Pump and Their Troubleshooting]] << >> Next Page: [[DCOM Volume IV Appendix 7|Appendix 7: Jet Pumps and Their Troubleshooting]]</div>Jumahttp://design.maji.go.tz/index.php/ReferencesIII:_ReferencesReferencesIII: References2022-07-20T11:53:41Z<p>Juma: /* REFERENCES */</p>
<hr />
<div>= REFERENCES =<br />
Linh Tran (2015). The Importance of Time Management (Aspects of Project Management Part 1). Retrieved from:<br />
[https://www.inloox.com/company/blog/articles/the-importance-of-time%20management-aspects-of-project-management-part-1/ https://www.inloox.com/company/blog/articles/the-importance-of-time management-aspects-of-project-management-part-1/]. Retrieved Date:5<sup>th</sup> March 2020<br />
<br />
MALCOLM N. SHAW 2008, International Law, Sixth Editor, Cambridge University Press, Cambridge Uk.<br />
<br />
Rocha Loures F & Rieu-Clarke A (eds) (2013). ''The UN Watercourse Convention in Force: Strengthening international law for trans-boundary water management''. Earthscan, Routledge.<br />
<br />
SIWI (2015). International water law. Retrieved from: https://www.siwi.org/icwc-course-international-water-law<br />
<br />
UNFCC (2015). Paris Agreement on climate change 2015. Retrieved from: https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement<br />
<br />
UNFCCC (2015). Paris Agreement. United Nations Framework Convention on Climate Change (UNFCCC). <br />
<br />
United Nations (2015). Helping governments and stakeholders make the Sustainable Development Goals (SDGs) a reality. Retrieved from:https://sustainabledevelopment.un.org/<br />
<br />
URT (2000). The Tanzania Development Vision 2025. Ministry of Finance and Planning. https://www.mof.go.tz/mofdocs/overarch/vision2025.htm.<br />
<br />
URT (2002). The National Water Policy (NAWAPO). The United Republic of Tanzania (URT).<br />
<br />
URT (2008). The National Water Sector Development Strategy (NWSDS). United Republic of Tanzania.<br />
<br />
URT (2014). Guidelines for Construction of Toilets and Sanitation. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br />
<br />
URT (2016). Five Year Development Plan (FYDP II), 2016/17 – 2020/21. Ministry of Finance and Planning. Retrieved from: https://mof.go.tz/mofdocs/msemaji/Five%202016_17_2020_21.pdf<br />
<br />
URT (2016). The National Guidelines for Water, Sanitation and Hygiene for Tanzania Schools. Ministry of Education, Science and Technology (MoEST).<br />
<br />
URT (2016). The Second Five Year Development Plan (FYDP II), 2016/17 – 2020/21. Ministry of Finance and Planning. https://mof.go.tz/mofdocs/msemaji/Five%202016_17_2020_21.pdf.<br />
<br />
URT (2017). National Guidelines for Water, Sanitation and Hygiene in Health Care Facilities. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br><br />
NSGRP II & III<br />
<br />
Wolf 1999, cited in https://www.siwi.org/icwc-course-international-water-law/ visited on 08, March ,2020.<br />
<br />
WorldBank (2010). Water and Sanitation Public- Private Partnership Legal Resource Centre. https://ppp.worldbank.org/public-private-partnership/sector/water-sanitation<br />
<br />
Noel Mades (2019). Quality assurance & Quality control in construction. Retrieved from: [https://www.qualityengineersguide.com/about.%20Retrieved%20date:%205th%20March%202020 https://www.qualityengineersguide.com/about. Retrieved date: 5th March 2020]<br />
<br />
The World Bank (2018). Contract Management Practice, 1st Edition September 2018. Washington DC 20433, The Worldbank. Retrieved on 6<sup>th</sup> March 2020.<br />
<br />
UK Essays (2016). Importance of Cost Control in Construction Projects. Retrieved from: https://www.ukessays.com/essays/accounting/importance-of-cost-control-in-construction-projects.php. Retrieved date: 5<sup>th</sup> March 2020<br />
<br />
URT (2016) The Public Procurement Act No.7 of 2011 and Amendments of 2016, Dar es Salaam, United Republic of Tanzania<br />
<br />
URT (2016) The Public Procurement Regulations, 2013 and Amendments of 2016, Dar es Salaam, United Republic of Tanzania<br />
WorldBank (2019). Project Management Essentials. Retrieved from: https://olc.worldbank.org/sites/default/files/Project%20Management%20Essentials%20Materials_0.pdf. Retrieved date: 5<sup>th</sup> March 2020<br />
<br />
Wrike (2020). Project Management Guide. Retrieved from: https://www.wrike.com/project-management-guide/faq/what-is-time-management-in-project-management/. Retrieved Date: 5<sup>th</sup> March 2020<br />
<br />
<br />
Previous Page: [[Chapter Five: essential basic field construction skills|Chapter Five: essential basic field construction skills]] << >> Next Page: [[DCOM_Volume_III_Appendix_1]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_5DCOM Volume IV Appendix 52022-07-20T11:53:03Z<p>Juma: </p>
<hr />
<div>'''Appendix 5: Details of a Submersible Pump and Their Troubleshooting'''<br />
[[File:Appendix5.png|center|400px]]<br />
(Source: World Bank, 2012)<br />
<br />
[[File:Appendix5i.png|center|400px]]<br />
(Source: www.dabpumps.com)<br />
<br />
'''Common Troubles of Submersible Pumps and Their Remedies'''<br><br />
The matrix below summarizes the common problems of submersible pumps and their remedies <br />
<br />
[[File:Appendix5ii.png|center|700px]]<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 4|Appendix 4: Details of Infiltration Gallery ]] << >> Next Page: [[DCOM Volume IV Appendix 6|Appendix 6:Centrifugal Pumps and Their Troubleshooting]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_4DCOM Volume IV Appendix 42022-07-20T11:46:55Z<p>Juma: </p>
<hr />
<div>'''Appendix 4: Details of Infiltration Gallery''' <br />
[[File:Appendix4i.png|center|500px]]<br><br />
(Source: The World Bank, 2012)<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 3|Appendix 3: Pumping Tests Procedure]] << >> Next Page: [[DCOM Volume IV Appendix 5|Appendix 5: Details of a Submersible Pump and Their Troubleshooting]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_3DCOM Volume IV Appendix 32022-07-20T11:31:09Z<p>Juma: </p>
<hr />
<div>'''Appendix 3: Pumping Tests Procedure'''<br />
<br />
1. Prior to starting the pump, measure and record the static water level.<br />
<br />
2. After starting the pump, measure the corresponding water levels. Discharge should be greater than the required yield and should be maintained at a constant rate during the entire duration of the test for 24 hours. Measurement intervals should be as follows:<br />
<br />
[[File:Appendix3.png|center|700px]]<br />
<br />
3. Simultaneous with the water level measurements, take measurements of discharge.<br />
<br />
4. Monitor nearby wells to determine effects during pumping.<br />
<br />
5. Right after the end of the pumping test, measure the water level recovery.<br />
<br />
6. Plot data obtained from the test on a semi-logarithmic paper showing the time in the abscissa (x axis) and the drawdown in the ordinate axis (y axis).<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 2|Appendix 2: Troubleshooting for Borehole/Tube Wells]] << >> Next Page: [[DCOM Volume IV Appendix 4|Appendix 4: Details of Infiltration Gallery]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_2DCOM Volume IV Appendix 22022-07-20T11:28:49Z<p>Juma: </p>
<hr />
<div>=== Appendix 2: Troubleshooting for Borehole/Tube Wells ===<br />
<br />
[[File:Appendix2.png|center|700px]]<br />
<br />
<br />
<br />
<br />
Previous Page: [[DCOM Volume IV Appendix 1|Appendix 1: Maintenance of Different Types of Boreholes]] << >> Next Page: [[DCOM Volume IV Appendix 3|Appendix 3: Pumping Tests Procedure]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_IV_Appendix_1DCOM Volume IV Appendix 12022-07-20T11:06:56Z<p>Juma: </p>
<hr />
<div><br />
[[Appendix 1: Maintenance of Different Types of Boreholes]]<br />
[[File:Appendix1i.png|center|700px]]<br />
[[File:Appendix1ii.png|center|700px]]<br />
[[File:Appendix1iii.png|center|700px]]<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[References_IV|References]] << >> Next Page: [[DCOM Volume IV Appendix 2|Appendix 2: Troubleshooting for Borehole/Tube Wells]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_III_Appendix_6DCOM Volume III Appendix 62022-07-20T10:17:35Z<p>Juma: </p>
<hr />
<div><div style="text-aling:justify;"><br />
APPENDIX 6: QUARTERLY PROGRESS REPORTING FORM<br><br />
Quarterly Progress Report No….<br />
Reporting Period: From…''[insert date]''………….To:…''[insert date]''………..<br><br />
[[File:App_48.PNG|700px]]<br />
<br><br />
[[File:App_49.PNG|700px]]<br />
<br><br />
<br />
__________________________________________<br />
<sup>14</sup> <span style="font-size:11px;">Insert rows as appropriate where there are many entries.</span><br />
[[File:App_50.PNG|700px]]<br />
[[File:App_51.PNG|700px]]<br />
<br><br />
<br />
<span style="text-align:center;">Progress Photos<br><br />
(insert Progress Photos below)</span><br />
<br />
Previous Page: [[DCOM_Volume_III_Appendix_5]] <br />
</div></div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_III_Appendix_5DCOM Volume III Appendix 52022-07-20T10:15:34Z<p>Juma: /* REQUIREMENTS OF CQA VALIDATION REPORT */</p>
<hr />
<div><div style="font-size:16px"><br />
== INTRODUCTION ==<br />
The purpose of this Construction Quality Assurance (CQA) Plan is to detail the testing methods and quality assurance procedures for required Water supply and sanitation projects. The Project includes:<br><br />
• (Narrate the Summarized details of the Project)<br><br />
<br />
== DEFINITIONS ==<br />
For the purpose of the CQA Plan, the following terms are defined below:<br><br />
'''Construction Quality Assurance (CQA) –''' A planned system of activities that provide assurance that materials or construction activities are undertaken and installed as specified in the drawings and specifications<br />
'''Construction Quality Control (CQC) –''' The process of measuring and controlling the characteristics of the item/product in order to meet the manufacturers or project specifications.<br><br />
•(Give definition of other terms and materials used)<br><br />
<br />
== ROLES OF THE PARTICIPANTS ==<br />
The participants and/or parties that have been identified as key personnel in the delivery of this project include, but are not necessarily limited to (Give the Positions of all key personnel in the project). The roles and responsibilities of the participants and/or parties are detailed below.<br />
For example <br><br />
'''Project Manager'''<br><br />
During the Construction, the Project Manager acting on behalf of the Employer, will serve as a single point of contact for the Design Engineer, Contractor and CQA Consultant.<br />
<br />
'''Design Engineer'''<br><br />
The design engineering services for the XXXL will be provided by XXXL Consultants. The Design Engineer shall review and approve any proposed changes during construction. He shall also be responsible in specifying the materials to be incorporated in the works.<br />
<br />
'''CQA Consultant''' <br><br />
The CQA Consultant is an independent party not affiliated with the contractors, subcontractors, suppliers or manufacturers. The CQA Consultant may be the Design Engineer. The CQA Consultant has the overall responsibility for managing, coordinating and implementing the CQA activities and confirming that the contractor’s construction quality control activities are performed in accordance with the CQA Plan, construction drawings and technical specifications. The critical activities related to the construction, manufacture and installation water pipes, water pumps and <br />
<br />
The CQA Plan must have cover page and Table of Content.<br><br />
This role can be played by the Project Manager. However in large and complex projects another person may be appointed to take up this role.<br />
other project components will be monitored and documented by the CQA Consultant. The CQA Consultant will be responsible for issuing a Final Certification Report containing CQA documentation sufficient to satisfy regulatory requirements and the requirements of this CQA Plan.<br />
<br />
'''Contractor'''<br><br />
The Contractor is responsible for the timely construction of the project, as detailed in the drawings and technical specification and in accordance with this CQA Plan. The Contractor is also responsible for the CQA. In particular, the Contractor shall ensure that:<br><br />
•Only materials meeting the requirements set forth in the Technical Specifications and drawings are used; and<br><br />
•The materials are installed in full conformance with the Technical Specifications and Design Drawings.<br><br />
<br />
'''Soil Testing Laboratory'''<br><br />
In the performance of the CQA activities, the CQA Consultant may engage '''YYYY''' Accredited soils testing laboratory, independent from the contractor, subcontractors, or any material supplier or manufacturer. The testing laboratory will conduct tests on representative samples to evaluate their properties and compliance with the technical specifications.<br />
<br />
==DESCRIPTION OF THE WORKS==<br />
==BREAKDOWN OF WORKS==<br />
The works to be carried out under as given in the construction drawings, Bills of Quantities and Technical Specifications include, but are not limited to the following:<br><br />
•[Identify and give detail breakdown of project major work tasks e.g. concreting, formwork, reinforcement work, excavation, drilling and pipe laying e.tc.]<br><br />
<br />
==WORKS INSPECTION AND TESTING==<br />
Works shall be carried out as per prepared methods statements; works inspection at the site is to be conducted for each major work task using standard inspection checklist.<br><br />
•[Use project specification documents, agreed standards and guidelines to develop method statements and inspection checklist for each major work task.]<br><br />
For the purpose of enhancing monitoring of quality in daily activities, an '''Inspection Test Plan'''/schedule is prepared. The plan details the type of test/inspection for every activity in work schedule, test standard to be used, means of verification of the test, roles and responsibility of everyone involved.<br><br />
•[Use project work schedule, method statements and agreed standards and guidelines to develop Inspection Test Plan]<br><br />
<br />
All inspections and tests at the site shall be conducted through guidance as provided in the Inspection Testing Plan.<br />
<br />
==DAILY REPORTING AND DOCUMENTATION==<br />
==General==<br />
An effective CQA Plan recognizes all construction activities that should be monitored and assigns responsibility for monitoring each activity.. This is most accomplished and verified by the documentation of quality assurance activities. The CQA Consultant Manager will document that all quality assurance requirements have been satisfied. The CQA Manager Consultant will also maintain at the job site a complete file of construction drawings, technical specifications, CQA Plan, test procedures, daily logs and other pertinent documents.<br />
<br />
==Daily Record Keeping==<br />
Use the inspection and testing schedule/plan to <br />
Standard reporting procedures will include preparation of daily CQA documentation which, at a minimum, will consist of:<br><br />
• Field notes, including memoranda of meetings and/or discussions with the Design Engineer or Project Manager;<br><br />
• CQA consulting logs and testing data sheets; and<br><br />
• Construction problems and solution summary sheets<br>.<br />
This information will be reviewed by the CQA Consultant, signed and transmitted to the Project Manager on a daily basis.<br><br />
Monitoring logs and testing data sheets will be prepared daily. At a minimum, these logs and data sheets will include the following information:<br><br />
• Date, project name and other identification;<br><br />
• Data on weather conditions;<br><br />
• A site plan showing work areas and locations selected for random CQA testing;<br><br />
• Descriptions and locations of ongoing construction;<br><br />
• Records of deliveries, condition, material roll numbers, description and locations of materials stores;<br><br />
• Equipment and personnel in each work areas;<br><br />
• Locations where in-site CQA tests and samples were taken;<br><br />
• A summary of test results;<br><br />
• Calibration of test equipment;<br><br />
• An identifying sheet number for cross referencing and document control;<br><br />
• Decisions made regarding acceptance of units of work and/or corrective actions to be taken; and<br><br />
• Signature of CQA Consultant Representative.<br><br />
<br />
==Construction Issues==<br />
The contractor will be informed by the CQA Consultant about any significant recurring non-conformance with the construction drawings, technical specifications, or CQA Plan. The cause of the non-conformance will be determined and appropriate changes in procedures or specifications may be recommended. These changes will be submitted to the design engineer for approval. When changes are made and approved, they will become part of the construction documents.<br />
<br />
==Photographic Records==<br />
Photographs will be taken by the CQA Consultant and documented in order to serve as pictorial record of work progress, problems and mitigation activities. The basic file will contain colour prints and they will be identified with the date, time and location of the photograph.<br />
<br />
==Design and/or Specification Change==<br />
Design and/or specification changes may be required during construction. In such cases, the CQA Consultant will notify the Design Engineer, the Project Manager and the Contractor.<br />
<br />
==REQUIREMENTS OF CQA VALIDATION REPORT==<br />
At the completion of the work, the CQA Consultant will submit to the Project Manager a signed final certification report. This report will document that:<br><br />
• Work has been performed in compliance with the construction documents;<br><br />
• Physical sampling and testing has been conducted at the appropriate frequencies specified in the CQA Plan;<br><br />
• The required CQA documentation has been completed.<br><br />
As a minimum, this report will include<br><br />
• Materials and equipment manufacturers quality control documentation;<br><br />
• A summary describing CQA activities and indicating compliance with the drawings and Technical Specifications;<br><br />
• A summary of CQA testing, including failures, re-test results, non-conformances and corrective measures;<br><br />
• Records of sample and re-sample locations, the name of the individual conducting the tests, and the results of the tests;<br><br />
• Daily inspection reports;<br><br />
• Progress photographs;<br><br />
• Any other relevant information; and <br><br />
• As built drawings (See below)<br><br />
The as-built drawings must detail the following:<br><br />
• (Give details to be included in the as-built drawings)<br><br />
<br />
The validation report must contain a statement by the CQA Consultant that the works have been carried out in accordance with the CPA Plan (and specifications attached to it) and that the validation report (including the drawings and appendices) represents a fair and accurate record of the works.<br />
<br />
</div><br />
Previous Page: [[DCOM_Volume_III_Appendix_4]] << >> Next Page: [[DCOM_Volume_III_Appendix_6]]</div>Jumahttp://design.maji.go.tz/index.php/Appendices:_AppendicesAppendices: Appendices2022-07-20T09:58:55Z<p>Juma: Created page with " == APPENDICES == Appendix 1: Maintenance of Different Types of Boreholes"</p>
<hr />
<div><br />
== APPENDICES ==<br />
<br />
Appendix 1: Maintenance of Different Types of Boreholes</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_III_Appendix_4DCOM Volume III Appendix 42022-07-19T17:23:38Z<p>Juma: /* Appeal process */</p>
<hr />
<div><div style="font-size:18px;"><br />
<div style="text-align:justify;"><br />
== APPENDIX 4: Proposed Service Provider Performance Evaluation ==<br />
<br />
== Definition == <br />
“Contractor” means a contractor, supplier, consultant or service provider who has entered into a contract with the MINISTRY <br><br />
“Performance Evaluation Form” means a form provided herein which shall be used to evaluate a contractor’s performance. <br><br />
“Project Evaluator(s)” means one or more person(s) from the MINISTRY’s UD(s) and/or a consultant to MINISTRY, that will be evaluating the Contractor’s performance by completing Performance Evaluation Forms in accordance with this procedural document, as amended.<br> <br />
“Disqualification” means the action that results when a Contractor receives a rating of “UNACCEPTABLE” on a Final Performance Evaluation form, subject to the terms and conditions of this document. <br />
<br />
== Purpose == <br />
This procedure provides a framework for the MINISTRY to evaluate and improve the performance of all contractors that are sourced by the MINISTRY by; <br><br />
a)pro-actively managing the performance of Contractors during the term of awarded Contracts; and <br />
b)creating a record of past performance for use by the MINISTRY in determining the award for future solicitations and contracts.<br><br />
<br />
Project Evaluator(s) may utilize this Contractor Performance Procedure for all contracts including but not limited to; invitational bids, single or sole source purchases, emergency purchases and wherever it is in the best interest of the MINISTRY. <br />
<br />
== When to carry out performance evaluations == <br />
=== Final Performance Evaluation shall be carried out within two (2) weeks of the following occurrences, depending on the type of good, service or construction ===<br />
a)for Construction contracts; upon the issuance of a Certificate of Final Completion;<br> <br />
b)for Consulting contracts; upon completion of the Contract; <br><br />
c)for Goods; upon delivery and inspection of goods and/or after the expiry of any applicable deficiency;<br><br />
d)for Services, upon completion of services and/or after the completion of deficiencies;<br> <br />
e)for Vehicles and Equipment; upon delivery and inspection and/or after the expiration of the warranty period;<br> <br />
f)upon termination of a Contract for any reason prior to the Contract end date.<br />
<br />
== Interim == <br />
Performance Evaluation shall be carried out at least every twelve (12) months for all Contracts with a term longer than one (1) year. <br />
<br />
== Performance evaluation system == <br />
Contractors shall be assigned one of the following ratings to each category set out on the Performance Evaluation Form. A critical aspect of the assessment rating system described below is the second sentence of each rating that recognizes the Contractor's resourcefulness in overcoming challenges that arise in the context of Contract performance.<br />
<br />
[[File:App_47.PNG|700px]]<br />
<br />
</div><br />
</div><br />
<br />
Previous Page: [[DCOM_Volume_III_Appendix_3]] << >> Next Page: [[DCOM_Volume_III_Appendix_5]]<br />
<br />
==Impact of perfomance evaluation==<br />
'''1.''' A Contractor whose interim performance is rated CAUTIONARY OR BELOW, in any category, should be requested in writing, to provide, a written response and appropriate corrective action within an acceptable timeframe, in accordance with the Terms and Conditions of the contract documents. Failure of the Contractor do so or if no satisfactory explanation is obtained, the MINISTRY may terminate the Contract.<br><br />
'''2.''' Final Performance Evaluation shall be used by the MINISTRY for consideration of award of contracts. If a Final evaluation has not been completed at the time that a tender award is under review, an Interim evaluation, if available, may be used by the MINISTRY to: <br><br />
a) determine if a Bidder submitting a Bid is a Responsible Bidder, and/or <br><br />
b) to evaluate past performance in the submitted tender. <br><br />
'''3.''' A Contractor that has received a TOTAL rating of 90-100% on the Contract’s Final Performance Evaluation Form:<br><br />
a) Will be considered a Responsible Bidder for future similar Bid submissions to the MINISTRY. ,<br> <br />
b) For a multi-year term Contract, the Contract may be extended for up to additional two (2) one (1) year terms, at the discretion of both the MINISTRY and the Contractor. Price adjustments for the extension shall be based on one of the following: <br><br />
(i) any inflationary contract annual increase r stated in the original contract documents or <br><br />
(ii) the same costs as stated in a firm fixed price multi-year Contract. <br><br />
Where a contract document did not state or request any inflationary annual Contract increase or where the Contractor is not agreeable to continuing the contract at their prices within a firm fixed price multi-year Contract, the contract extension will not apply and the MINISTRY will move forward with a public invitation of new bids.<br><br />
'''4.''' A Contractor that has received a TOTAL rating of 80-89% on the Final Performance Evaluation Form; <br><br />
a) will be considered a Responsible Bidder for future similar Bid submissions to the MINISTRY; and <br><br />
b) for a multi-year term Contract, the Contract may be extended for an additional one (1) year term, at the discretion of both the MINISTRY and Contractor. Costs for the extension shall be based on either: <br><br />
(i) any inflationary contract annual increase r stated in the original contract documents or<br> <br />
(ii) the same costs as stated in a firm fixed price multi-year Contract.<br><br />
Where a contract document did not state or request any inflationary annual Contract increase or where the Contractor is not agreeable to continuing the contract at their prices within a firm fixed price multi-year Contract, the contract extension will not apply and the MINISTRY will move forward with a public invitation of new bids. <br><br />
'''5.''' A Contractor that has received a TOTAL rating of 65-79% on the FINAL Performance Evaluation Form<br><br />
a) may be considered a Responsible Bidder for future similar Bid submissions to the MINISTRY; and <br><br />
b) for multi-year Contracts, is not eligible for any additional extensions outside of the terms of the current Contract. <br><br />
'''6.''' A Contractor that has received a TOTAL rating of (50-64%) on the Final Performance Evaluation <br />
a) may or may not be considered a Responsible Bidder for future similar Bid submissions to the MINISTRY; and <br><br />
b) for multi-year Contracts, is not eligible for any extension terms within the current Contract. <br><br />
c) may be asked to demonstrate in writing or by other acceptable means that they have corrected all previously documented areas of “CAUTIONARY” OR LESS performance concerns to a standard satisfactory to the MINISTRY, prior to awarding any future Contracts. In addition, a list of new references may be requested by the MINISTRY for work completed by the Contractor since the date of the Performance Evaluation where a rating of CAUTIONARY” OR LESS was given in any category. The MINISTRY reserves the right, at its sole discretion not to award a Contract to any Contractor, for an indefinite period, that fails to provide satisfactory evidence of correcting any documented past performance concerns by the MINISTRY.<br> <br />
'''7.''' A Contractor that has received a TOTAL rating of less than 50%on the Final Performance Evaluation Form;<br> <br />
a) shall not be considered a Responsible Bidder and shall be recommended for blacklisting by the Authority; and<br> <br />
b) Shall not be considered for award of any contract by the MINISTRY.<br><br />
<br />
=Contractor response process=<br />
'''1.''' The Contractor shall have seven working days to: <br />
a. Submit a written response to an Interim or Final Performance Evaluation and /or <br />
b. Submit a written request to appeal a Final Performance Evaluation rating. <br />
If no response is received within the above noted timeframe the Evaluation rating shall be considered final.<br />
<br />
=Appeal process= <br />
'''1.''' Within ten (10) business days) of receiving an appeal response form in respect to a Final Performance Evaluation Form, the MINISTRY will conduct a full review of the appeal and render a final decision based on the appeal information.<br> <br />
'''2.''' The MINISTRY may request additional information from the Contractor in order to conduct a full review.<br><br />
<br />
'''PERFORMANCE EVALUATION FORM'''<br />
[[File:Contract.jpg|700px]]<br />
<br />
<br />
<br />
[[File:Perfomance.jpg|700px]]<br />
<br />
<br />
<br />
[[File:Evaluator's.PNG|700px]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_III_Appendix_3DCOM Volume III Appendix 32022-07-19T16:37:41Z<p>Juma: /* Appendix 3: PARTNERING A TEAMWORK APPROACH */</p>
<hr />
<div><div style="text-align:justify"><br />
== APPENDIX 3: PARTNERING A TEAMWORK APPROACH ==<br />
<div style="font-size:20px"><br />
Partnering is a project approach designed to allow the design and construction process to be performed within an environment of mutual trust, commitment to shared goals, and open communication among the client, architect/engineer, construction manager, general contractor (if applicable), and subcontractors. Partnering establishes a working relationship among all of the team members based on a mutually agreeable plan of cooperation and teamwork. Parties to the design and construction process, in agreeing to work under a partnering approach, work to create an atmosphere in which all parties are working in harmony towards mutual goals to avoid claims and litigation.<br />
<br />
Partnering as a concept has attracted a great deal of attention due to the tremendous amount of litigation which has occurred in recent years in the construction industry. Adversarial relationships and resulting claims and litigation have resulted in huge legal costs in many construction projects. Partnering has shown that it does not need to be that way. Through close communication and establishing mutually agreeable goals at the beginning of the project, outstanding results can be achieved with no necessity for outside lawyers. The objective is a “win-win” attitude between all parties due to the design and construction process. There are already numerous examples of completed projects which have proven that the partnering process works. <br />
<br />
The essential elements of a partnering agreement are as follows:<br><br />
Commitment to partnering by the top management of every organization involved in the project, Trust relationship between all parties through personal relationships and open communication with mutual sharing and understanding of each party's risks and goals.<br><br />
A partnering charter developed jointly by all parties to the project which identifies specific mutual goals and objectives of the partnering participants for continuous evaluation and review against the agreed upon mutual goals. Timely resolution of any disputes at the lowest level possible during the project.<br />
<br />
'''Partnering Advantages'''<br><br />
Partnering can result in a significantly higher level of quality on a project and can significantly increase the probability of timely and on-budget completion of the project and can reduce the risk of claims and litigation.<br />
<br />
'''Benefits to the employer'''<br><br />
1. Greater control of schedule and cost through close communication and regular evaluation of project progress.<br><br />
2. Higher quality through focusing on mutual goals by team members who are not side-tracked into adversarial relationships.<br />
<br />
_____________________________________<br><br />
<sup>11</sup> <span style="font-size:10px;">Downloaded from https://www.nap.edu/read/9227/chapter/4 on 20th January 2020.</span><br />
<br />
3. The potential for a totally claim free project which can be achieved through partnering. Lower administration costs can be achieved by the avoidance of case building and use of outside counsel.<br><br />
4. Greater innovation through open communication and trust particularly in the area of value engineering and constructability reviews.<br><br />
5. Higher profit potential for all participants resulting in a more efficient project delivery process.<br />
<br />
'''Benefits to the contractor'''<br><br />
1.Reduced risk of delays and cost overruns by early and active involvement in issues resolution.<br><br />
2. Increased productivity through elimination of adversarial relationships and case building. Reduced exposure to claims litigation through early low level project resolution of problem issues.<br><br />
3.Greater profit potential.<br />
<br />
'''Benefits to the architect/engineering consultants'''<br><br />
1. Greatly reduced exposure to liability for document deficiencies through early review.<br><br />
2. Co-operative effort to resolve problems early to reduce exposure to claims and litigation resulting in reduced administrative costs and increased profit potential.<br />
<br />
'''Benefits to subcontractors and suppliers'''<br><br />
1. Improved cash flow due to elimination of, or reduction in, disputes resulting in withheld payments. Greater involvement in the decision making process as an active team member in the project.<br><br />
2. Reduced exposure to, or elimination of, claims and litigation through early project dispute resolution. And finally, increased profit potential through a “win-win” attitude.<br><br />
There is considerable overlap in the benefits for all parties to the project. This highlights the similar interests that all parties have in agreeing to mutual goals and objectives in the partnering charter.<br />
<br />
'''IMPLEMENTATION OF PARTNERING'''<br><br />
Partnering requires considerable time, effort, and commitment at all stages of a project. The use of a partnering strategy is the voluntary decision to which all team members agreed at the beginning of the project. Implementation steps for partnering could proceed in the following manner:<br><br />
1.All parties should express their desire to perform the project under a partnering agreement at the beginning of the project. The owner’s intention of utilizing the concept should be mentioned in the bid solicitation and specifications. Any pre-bid conference should include a presentation on partnering.<br><br />
2.There should be a meeting of top management of all firms involved in the project in the early design stage. However, the executives at the CEO level should meet to discuss the partnering approach to managing the project. A commitment from the top of each organization is essential for partnering to work.<br><br />
3.A partnering workshop/team building session should be held in the very early stages of the project. Each member team should designate a partnering leader who would intend to participate in the workshop. All of the participants of the partnering workshop would develop and agree to a partnering charter which is a written list of the goals and objectives for the project. The charter is a physical symbol of the project team members' commitment to partnering. It is considered to be a road map for regular evaluation of the project process.<br><br />
<br />
Specific benchmarking measurement goals as well as general goals can be part of the partnering charter. The charter does not change the terms of the project participants' contracts and is not a contract in itself. The charter is a guide for co-operation. Each party to the project should sign the charter to show commitment to the partnering process. For periodic evaluation, a formal, regular evaluation of the progress of the project should occur normally as a formal monthly or bimonthly meeting. At this review meeting, there should be an open dialogue on any problem areas with the goal of maintaining all parties' commitment to the partnering process and to make sure that an adversarial relationship has not started to build.<br />
<br />
4.The partnering charter should commit all of the team members to dispute resolution without claims or litigation. The goal is that any disagreement is resolved at the project level and that if a dispute is unable to be resolved at the project level, it should quickly move up to the next level of management for resolution. Resolutions should be sought in a “win-win” atmosphere of open communication and trust. The goal is to avoid claims and any involvement by outside lawyers that could result in litigation. Alternate Dispute Resolution (ADR) techniques can be an important part of the partnering process. If any dispute is unable to be resolved at the lower level, the parties should agree to mediation or some similar low cost dispute resolution approach. The goal is to avoid the time and expense of claims and litigation. Alternate dispute resolution techniques can help maintain team spirit and friendly working relationships at the project.<br />
<br />
Construction projects where adversarial, confrontational attitudes have resulted in misdirected energies and high cost of claims and litigation. The partnering process changes mindsets. Partnering can help all the involved in the design and construction process to redirect their energies and focus on the real issues associated with achieving optimum project goals. Partnering is not a panacea. Partnering requires a major commitment to change by all project parties to work in a team environment that results in a “win-win” relationship. Partnering can and is changing the industry one project at a time. It is an approach which can produce outstanding results for the construction industry.<br />
</div><br />
</div><br />
<br />
Previous Page: [[DCOM_Volume_III_Appendix_2]] << >> Next Page: [[DCOM_Volume_III_Appendix_4]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_III_Appendix_2DCOM Volume III Appendix 22022-07-19T16:21:19Z<p>Juma: /* Appendix: 2 procurement records keeping */</p>
<hr />
<div>== Appendix: 2 procurement records keeping ==<br />
Details of Records to be Included in the Procurement and Contract File.<br />
[[File:App_44.PNG|700px]]<br><br />
[[File:App_46.PNG|700px]]<br />
<br />
Previous Page: [[DCOM_Volume_III_Appendix_1]] << >> Next Page: [[DCOM_Volume_III_Appendix_3]]</div>Jumahttp://design.maji.go.tz/index.php/DCOM_Volume_III_Appendix_1DCOM Volume III Appendix 12022-07-19T10:23:10Z<p>Juma: /* APPENDICES */</p>
<hr />
<div><div style="text-aling:justify;"><br />
== APPENDICES ==<br />
=== Appendix 1:Template for Contract Management Plan ===<br />
<br />
[[File:App_1.PNG|700px]]<br><br />
<br />
Contract Manager/Supervisor Sign-off <br><br />
I, as Contract Manager/Supervisor, will ensure that relevant legislation, policies and organizational requirements relating to contract management are adhered to.<br />
<br />
Signature:......................................................<br><br />
Name:...........................................................<br><br />
Position:.......................................................<br><br />
Address:........................................................<br><br />
Telephone:......................................................<br><br />
Email:..........................................................<br><br />
Date:...........................................................<br><br />
<br />
Plan Approval<br><br />
Signature:......................................................<br><br />
Name:...........................................................<br><br />
Position:.......................................................<br><br />
Date:...........................................................<br><br />
<br />
'''1. BACKGROUND'''<br><br />
The [Insert name of Client] has awarded a contract for [Insert contract description] to [Insert name of Contractor].<br><br />
<br />
Provide brief background on:<br><br />
• the branch/directorate<br><br />
• the tendering and contracting process<br><br />
• the selection of the successful Contractor<br><br />
<br />
The following documents are either referenced or relate to this contract management plan:<br><br />
• Signed Works Contract <br><br />
• [List Client contract management policies and other relevant documents ] <br><br />
<br />
'''2. PURPOSE AND OBJECTIVES'''<br><br />
The purpose of this contract management plan is to document the key activities and tasks required to manage this contract to ensure that the objectives of the contract are achieved.<BR><br />
The plan describes how the Client and the Contractor will work together over the life of the contract to ensure timely delivery of goods and services meeting the requirements specified in the contract.<br />
This plan will be used by the Client to review the performance of the contract and monitor the achievement of the contract outcomes.<br><br />
<br />
The objectives of this contract are to:<br><br />
• [Identify objectives – refer acquisition plan and/or tender documentation]<br><br />
• e.g. to ensure cost effective and efficient delivery of contracted goods/services;<br><br />
• e.g. to ensure the continuous and timely supply of quality goods<br><br />
• etc.<br><br />
<br />
'''3.PROCUREMENT KEY DELIVERABLES'''<BR><br />
The key deliverables of this contract are:<br><br />
• [identify key deliverables – refer contract documentation]<br><br />
• etc.<br />
<br />
Contractual Milestones and Deliverables<br><br />
[[File:App_6.PNG|700px]]<br><br />
<br />
'''4. CONTRACT SUMMARY'''<br><br />
<br />
[[File:App_8.PNG|700px]]<br><br />
<br />
The following bank guarantees and other securities apply to this contract:<br><br />
• specify securities<br><br />
The following statutory and regulatory requirements are relevant to this contract:<br><br />
• detail these requirements including work, health and safety, environmental, human resources etc.<br />
<br />
The following warranties apply to this contract:<br><br />
• document warranty provisions of contract<br><br />
• detail how warranty provisions are to be managed during the life of the contract<br />
<br />
Key contract conditions and clauses relevant to this contract include:<br><br />
• [Insert key details including intellectual property ownership etc.]<br><br />
• [Insert details of any other requirements (eg industry participation policy) that parties are required to comply with]<br />
<br />
'''5. ROLES, RESPONSIBILITIES AND GOVERNANCE'''<br><br />
<br />
=== Governance Structure ===<br />
[Describe the governance structure relevant to the contract. Where possible include a diagram showing the key parties, the hierarchy, lines of reporting etc.]<br />
<br />
=== Key Contacts, Roles and Responsibilities ===<br />
[Insert all key personnel for Contractor, Employer and the Consultant AND other important parties]<br><br />
<br />
[[File:App_10.PNG|700px]]<br><br />
<br />
=== Contract Manager ===<br />
<br />
The contract manager/supervisor is responsible for:<br><br />
• ensuring the contract outcomes are achieved;<br><br />
• managing and addressing contract risks;<br><br />
• identifying and addressing opportunities for improving the contract;<br><br />
• maintaining good relationships with the Contractor<br><br />
• scheduling regular contract management meetings; <br><br />
• communicating with users, stakeholders and clients;<br><br />
• ensuring that performance measures are met;<br><br />
• providing performance reports to senior managers or the governance committee;<br><br />
• addressing problems and conflicts that may arise; and<br><br />
• assessing and (where required) seeking approval for any variations to the contract.<br><br />
<br />
The contract manager/supervisor should regularly refer to the contract management plan and ensure it is amended or updated as required to reflect any changes in circumstances during the operation of the contract.<br />
<br />
The Contractor’s contract manager is<br><br />
Name:<br><br />
Position:<br><br />
Address:<br><br />
Telephone:<br><br />
Email: <br><br />
<br />
=== Oversight Committee ===<br />
If an oversight committee is required please complete the following; if not relevant, delete.<br />
<br><br />
A Contract Management Committee comprising the following members will provide oversight of the contract:<br><br />
• insert names of committee members<br><br />
• insert names of committee members <br><br />
• etc<br />
<br />
The role of this committee is to:<br><br />
• list the committee responsibilities <br><br />
• etc<br />
<br />
=== Communication ===<br />
The following communication strategies and protocols will be used to communicate with the Contractor, users and key stakeholders:<br><br />
<br />
[[File:App_11.PNG|700px]]<br><br />
<br />
The following documents relating to the contract will be stored and filed for reference and audit purposes:<br><br />
<br />
• [Insert the name of the document, the version number and where they are held, for example, transition plans, risk management plans. Include any relevant documents that have been referred to in this plan.]<br><br />
<br />
'''6. CONTRACT MANAGEMENT MEETINGS'''<br><br />
Contract management meetings will be held every one/three months (update as appropriate).<br><br />
Attendees at these meetings are:<br><br />
• Contract manager/Supervisor <br><br />
• Contractor contract manager <br><br />
• insert name of other attendees <br><br />
• etc<br />
<br />
A standard agenda (refer Attachment One) is to be used.<br><br />
The contract manager shall organise the meeting and prepare minutes after each meeting.<br><br />
The following meetings shall also be held:<br><br />
<br />
[[File:App_13.PNG|700px]]<br><br />
<br />
'''7.IMPLEMENTATION APPROACH'''<br><br />
Contract implementation is a critical period that can entail specific risks and challenges.<br> <br />
The following implementation approach will be adopted:<br><br />
• development of an implementation plan;<br><br />
• a contract start-up meeting with the Contractor and key stakeholders will be held to discuss implementation;<br><br />
• [Insert other details including, for example, establishment of governance committee, communication to users and stakeholders, briefings, timeframes, resources and strategies to address identified risks.]<br><br />
The following transition in tasks and responsibilities will be addressed for this contract:<br><br />
• [Where applicable, list details such as planning the kick-off Meeting, handover, etc.]<br><br />
<br />
'''8.RISK MANAGEMENT, INSURANCE, GUARANTEES AND SECURITIES'''<br><br />
<br />
=== Risk management ===<br />
The contract manager/supervisor is responsible for identifying and managing risks during the contract.<br><br />
The contract manager must ensure systems are in place to monitor emerging risks so that appropriate actions can be taken proactively.<br><br />
The following key contractual risks have been identified and will be monitored, treated and mitigated:<br><br />
• [Insert details including risks that were identified earlier in the procurement process]<br><br />
<br />
=== Insurance ===<br />
The following insurance certificates are current and will be monitored to ensure future currency through the life of the contract:<br><br />
<br />
[[File:App_16.PNG|700px]]<br />
<br />
=== Guarantees and Securities ===<br />
[[File:App_17.PNG|700px]]<br><br />
<br />
9.PERFORMANCE MANAGEMENT<br><br />
<br />
=== Reports ===<br />
The key milestones relating to the performance of this contract are:<br><br />
• [List details]<br><br />
<br />
The following key performance indicators will be used to measure the performance of the contract:<br><br />
• [List performance indicators]<br><br />
<br />
'''Key Performance Indicators (to measure performance and outcomes)'''<br><br />
<br />
[[File:App_19.PNG|700px]]<br><br />
<br />
'''Underperformance/ default contractual actions'''<br><br />
<br />
[[File:App_20.PNG|700px]]<br />
<br />
The following reports will be provided by the Contractor:<br><br />
• [List details - refer specification or statement of requirements in the contract]<br><br />
<br />
[[File:App_21.PNG|700px]]<br><br />
<br />
The following reports will be prepared by the Contract Manager/Supervisor<br><br />
<br />
[[File:App_22.PNG|700px]]<br><br />
<br />
=== Records Management ===<br />
[[File:App_23.PNG|700px]]<br><br />
<br />
===Issues===<br />
'''Issues Escalation Procedure'''<br><br />
<br />
[[File:App_24.PNG|700px]]<br><br />
<br />
===Issues===<br />
'''Issues Escalation Procedure'''<br><br />
<br />
[[File:App_24.PNG|700px]]<br><br />
<br />
=== Inspection Checklist ===<br />
<br />
==== Borehole Inspection Form Checklist ====<br />
<br />
[[File:App_25.PNG|700px]]<br><br />
[[File:App_26.PNG|700px]]<br><br />
[[File:App_27.PNG|700px]]<br><br />
[[File:App_28.PNG|700px]]<br><br />
[[File:App_29.PNG|700px]]<br><br />
<br />
==== Dam Inspection Form Checklist (OWRB, 2011) ====<br />
<br />
[[File:App_30.PNG|700px]]<br />
[[File:App_31.PNG|700px]]<br><br />
[[File:App_32.PNG|700px]]<br />
[[File:App_33.PNG|700px]]<br><br />
<br />
''Legend'':<br><br />
Please rate the condition of Sections 1 – 11 on inspection form either: Good, Acceptable, Deficient, or Poor.<br />
<br />
'''Good:''' No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading Conditions (static, hydrologic, seismic) in accordance with the applicable regulatory criteria or tolerable risk guidelines.<br />
<br />
'''Acceptable:''' No existing dam safety deficiencies are recognized for normal loading conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. <br />
<br />
'''Deficient:''' A dam safety deficiency is recognized for loading conditions which may realistically occur. Remedial action is necessary. Poor may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Further investigations and studies are necessary. <br />
<br />
'''Poor:''' A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.<br />
<br />
==== General Form Checklist ====<br />
<br />
[[File:App_34.PNG|700px]]<br><br />
[[File:App_35.PNG|700px]]<br><br />
[[File:App_36.PNG|700px]]<br><br />
[[File:App_37.PNG|700px]]<br><br />
[[File:App_37.PNG|700px]]<br><br />
<br />
'''10.DISPUTE RESOLUTION AND TERMINATION'''<br><br />
A formal contract must have dispute resolution clauses (refer clause – update clause no) which can be initiated by the contract manager when the informal process does not resolve a dispute.<br />
<br />
The following dispute resolution process will be used for managing disputes:<br><br />
• ''[List details including any escalation process. Reference the relevant contract clauses.]''<br><br />
If the Contractor breaches or repudiates the contract and fails to remedy the breach as required by the appropriate contractual clause (refer clause – update clause no), then the Client may initiate action to terminate the contract. Approval must be sought from appropriate senior management prior to actioning the termination process. <br />
<br />
=== Payment Plan/Procedures ===<br />
'''11. PAYMENT TERMS AND ARRANGEMENTS'''<br><br />
[[File:App_40.PNG|700px]<br><br />
<br />
The following contract variation method and procedures will be used to consider and approve contract variations:<br><br />
• [List details]<br />
<br />
'''12.CONTRACT VARIATIONS AND EXTENSIONS'''<br><br />
This contract has [List details where applicable] extension options. <br><br />
The following review will be undertaken to determine whether the contract should be extended:<br><br />
• [List details]<br><br />
<br />
'''13. CONTRACT FINALISATION'''<br><br />
<br />
The following contract finalization tasks and transition out requirements will be implemented at the conclusion of the contract to close the contract:<br><br />
• Completion of all outstanding contract actions;<br><br />
• finalisation of all deliveries required by the contract;<br><br />
• completion and reconciliation of all payments and financial obligations;<br><br />
• finalisation of all required reports; <br><br />
• [List other details including, for example, the Contractor may be required to handover government owned assets, materials, files.]<br><br />
<br />
A post contract review report will be undertaken at the conclusion of the contract period.<br />
The report is to be forwarded to the Client procurement unit.<br />
<br />
=== Contract Management Meeting Agenda ===<br />
[[File:App_43.PNG|700px]]<br><br />
<br />
Previous Page: [[ReferencesIII:_References]] << >> Next Page: [[DCOM_Volume_III_Appendix_2]]</div>Jumahttp://design.maji.go.tz/index.php/List_of_Special_Committee_Members_IVList of Special Committee Members IV2022-07-18T15:08:58Z<p>Juma: </p>
<hr />
<div>LIST OF SPECIAL COMMITTEE MEMBERS ON REVIEWING AND UPDATING THE 3RD EDITION,<br />
DESIGN MANUAL FOR WATER SUPPLY AND WASTEWATER DISPOSAL OF 2009<br />
<br><br />
[[File:Comiteemembers.PNG|710px]]<br><br />
<br />
[[Image:Dodoma.png|800px]] <br><br />
<br><br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Acknowledgements_|Acknowledgements]] << >> Next Page: [[List_of_Abbreviations_IV|List of Abbreviations]]</div>Jumahttp://design.maji.go.tz/index.php/Acknowledgements_IVAcknowledgements IV2022-07-18T15:06:29Z<p>Juma: Created page with "<div style="text-align: justify"> Changes of policy and technology have necessitated the preparation of this new edition of the DCOM Manual for the design, construction super..."</p>
<hr />
<div><div style="text-align: justify"><br />
Changes of policy and technology have necessitated the preparation of this new <br />
edition of the DCOM Manual for the design, construction supervision, operation <br />
and maintenance of water supply and sanitation projects in Tanzania. The <br />
4th Edition of the DCOM Manual is expected to guide engineers and technicians <br />
in their design work, construction supervision as well as in operation and <br />
maintenance of relevant projects. The manual is to be adopted for all water <br />
supply and sanitation projects in the country.<br />
The 4th Edition of the DCOM Manual has been developed using the following <br />
approaches:<br />
* Review of the 3rd Edition, including benchmarking with design manuals from other countries,<br />
* Website reviews and review of other manuals prepared by consultants who have had working experience in Tanzania,<br />
* Review of Literature data collection and design methods review,<br />
* Data collection from stakeholders, namely: Primary stakeholders-MoW technical and management staff; Private companies that deal with implementation of water supply and sanitation projects; Beneficiaries of water supply and sanitation projects,<br />
* Collection and digitization of existing standard drawings after conversion into metric units as felt necessary,<br />
* Review of the 4th Edition drafts by various stakeholders including MoW staff and other stakeholders outside the MoW,<br />
* Revision of the 4th Edition by incorporating comments and views from all the stakeholders,<br />
* Preparation and submission of the 4th Edition of the DCOM Manual.<br />
<br />
The review and updating of the 3rd Edition of the DCOM Manual is considered to <br />
be a continuous process involving regular updating to incorporate changes in <br />
policy and societal needs, emerging issues, technologies or methods. The MoW <br />
welcomes comments on this new edition of the DCOM Manual from users in <br />
order to facilitate further improvement of future editions.<br />
<br />
The new features in the 4th Edition of the DCOM Manual include mainstreaming <br />
of climate change impacts and use of various types of software in the design <br />
of water supply and sanitation projects. These features have facilitated the <br />
faster and more accurate analysis of pertinent data. The DCOM manual has also<br />
encouraged the use of Supervisory Control and Data Acquisition Systems (SCADA) <br />
for large urban and generally national projects where local capacity building can <br />
be guaranteed by the providers. It should be borne in mind that relevant software <br />
allows a wide variety of scenarios to be considered. However, it should also <br />
be noted that, despite the critical role of software/models in guiding decision-making, its limits should be realized so as to avoid its becoming a substitute for <br />
critical practical evaluation.<br />
<br />
I wish to thank the different stakeholders for their active participation and support <br />
in contributing towards the various inputs during the course of preparation of this <br />
DCOM Manual. They include those from within and outside the Ministry of Water <br />
as well as Development Partners, NGOs, Consultants, Suppliers and Contractors <br />
as well as other Ministries. The review team of engineers and technicians from <br />
MoW, RUWASA, WSSA who worked with the Special Committee for three days in <br />
March 2020 are hereby gratefully acknowledged.<br />
<br />
Finally, I take this opportunity to thank the members of the Special Committee on <br />
Reviewing and Updating the 3rd Design Manual of 2009 under the Chairmanship <br />
of Eng. Prof. Tolly S. A. Mbwette for diligently undertaking this assignment.<br />
<br />
[[Image:Mkumbo_Signature.png|800px|link=Acknowledgements]] <br><br />
<br />
<br />
Previous Page: [[Preface_IV|Preface]] << >> Next Page: [[List_of_Special_Committee_Members_IV]]<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Preface_IVPreface IV2022-07-18T15:05:42Z<p>Juma: Created page with "==Preface== <div style="text-align:justify"> The Government of the United Republic of Tanzania, through the Ministry of Water, oversees the implementation of the Water Supply..."</p>
<hr />
<div>==Preface==<br />
<div style="text-align:justify"><br />
The Government of the United Republic of Tanzania, through the Ministry <br />
of Water, oversees the implementation of the Water Supply and Sanitation <br />
projects in the country. The Ministry of Water has published several editions of <br />
the relevant Design Manuals. The First edition was the Water Supply and Waste <br />
Wastewater Disposal Manual of 1985/86. The Second edition was titled “Design <br />
Manual for Water Supply and Wastewater Disposal of 1997”. The Third edition <br />
was titled “Design Manual for Water Supply and Wastewater Disposal of 2009”. <br />
These manuals guided the Ministry and the general public in the planning and <br />
design of water supply and sanitation projects in the country. <br />
<br />
As it is now well over ten years since the Third Edition of the Design manual <br />
was adopted, and since many scientific and technological changes have taken <br />
place, including the conclusion of MDGs and adoption of the SDGs in 2015 as <br />
well as useful lessons learnt out of implementation of the WSDP I and WSDP <br />
II (which is still on-going), it has become necessary to revise the 2009 design <br />
manual. Notably, the 3rd Edition Design Manual has, among other things, limited <br />
coverage on the impact of climate change, application software and sanitation <br />
management issues.<br />
<br />
The Ministry is now at various stages of instituting policy and legal reforms that <br />
are deemed necessary for futuristic improvement in the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in Tanzania. Therefore, the 4th Edition of the Design, Construction Supervision, <br />
Operation and Maintenance (DCOM) Manual will make invaluable contribution <br />
in this regard. It is important to recall that the Government has established <br />
the Rural Water Supply and Sanitation Agency (RUWASA), which is responsible <br />
for the supervision, execution and management of rural water supply and <br />
sanitation projects. RUWASA is expected to improve the existing responsibility <br />
and accountability in the management of water and sanitation services in rural <br />
areas. The 4th Edition DCOM Manual will support the sector development and <br />
implementation institutions (including RUWASA, Water Supply and Sanitation <br />
Authorities, development partners, and civil society organisations), and will <br />
provide valuable information relating to implementation of water supply and <br />
sanitation projects in their various stages, from pre-feasibility and feasibility <br />
studies, to planning, designing, construction supervision and operation and <br />
maintenance. <br />
<br />
It is expected that the 4th Edition of the DCOM Manual will position the Ministry <br />
well to systematically and comprehensively implement the design, construction <br />
supervision, operation and maintenance of water supply and sanitation projects <br />
in order to ensure the sustainability of water supply and sanitation projects in <br />
the country. This is also expected to contribute in realising the water sector’s <br />
contribution towards achieving the Tanzania Development Vision 2025, as well as <br />
the various national and international commitments and milestones in the water <br />
sector as also specified in the Agenda 2063 in the "Africa that we want" and the <br />
Sustainable Development Goals (SDGs) on water and sanitation (SDG No. 6). <br />
<br />
The preparation of this Water Supply and Sanitation Projects DCOM Manual <br />
required contributions in form of both human and financial resources. The <br />
Ministry of Water, therefore, takes this opportunity to thank the members of <br />
the Special Committee for Reviewing and Updating the 3rd Edition of the Design <br />
Manual for Water Supply and Wastewater Disposal of 2009, specifically for their <br />
efforts in preparation of this comprehensive 4th Edition of the DCOM Manual. <br />
Thanks are also due to the World Bank for financing the major part of the activities, <br />
and to all others who contributed in the preparation of this new DCOM Manual.<br />
<br />
In the future, the Ministry plans to periodically review and update the DCOM <br />
Manual in order to keep in pace and address emerging changes in policy and <br />
societal needs, emerging technologies, and sustainability concerns in the <br />
implementation of water supply and sanitation projects in the country. <br />
<br />
[[Image:MakameSignature.png|632px|link=DCOM_Volume_I]] <br><br />
<br />
<br />
Next Page: [[Acknowledgements_IV|Acknowledgements]]<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_Four:_contract_supervision_and_administrationChapter Four: contract supervision and administration2022-07-18T12:25:19Z<p>Juma: /* Differentiating Quality Assurance from Quality Control */</p>
<hr />
<div><div style="text-align:justify"><br />
=CHAPTER FOUR CONTRACT SUPERVISION AND ADMINISTRATION=<br />
==General Requirements for Contract Supervision and Administration==<br />
Contract supervision and administration is undertaken by the PM in consultation with the UD. Supervision and administration of works contracts is often a complex task relying heavily on the experience and qualifications of the PM. The basic actions to be undertaken under Contract Administration and Supervision are listed below, namely to:<br />
<br />
(a) Maintain close supervision of the Contractor’s performance, work done, materials used, and labour force on the site to ensure that potential problems are identified and solved as early as possible.<br><br />
(b) Notify the Contractor, in writing, requesting rectification of any deficiencies in workmanship, materials used, safety or environmental standards, or other required performance standards<br><br />
(c) Hold regular site meetings with the Contractor to identify the causes of any slippage in the schedule of works.<br><br />
(d) Receive regular progress reports from the Contractor and ensure that written records of any disputes or contact variation orders issued are maintained.<br><br />
(e) Ensure that any significant problems, variation orders, day work claims, compensation events, cost overruns, or slippage in the timetable are brought to the attention of the PE.<br><br />
(f) Initiate and supervise any process for claims against insurance or the Contractor.<br><br />
(g) Conduct detailed checks on the Contractors claims for work performed, re-measure as appropriate, and prepare Interim Payment Certificates, deducting any retention percentage specified in the Contract.<br><br />
(h) Participate in inspections for Interim and Final Handover of the Works and prepare the Final Payment Certificate releasing retention money to the Contractor.<br><br />
Contract Administration and Supervision involves six (6) main activity levels and these include: Time Control; Quality Control; Cost Control; Managing Variations; Ensuring compliance with the laws of the country; and Managing project closure.<br />
==Time Control==<br />
===Importance of Time Control for the Construction Projects===<br />
Time control involves implementation and completion of a project within the agreed works programme. Effective time management is essential to successfully and efficiently meet budget and programme targets. Projects can risk incurring unnecessary costs and delays as a result of ineffective time management, either by failing to allow for the full complexity of a project, or by failing to effectively manage scheduled work or unexpected events.<br />
<br />
Effective project time management starts with the preparation of a realistic time for completion of the assignment by the PE. Unfortunately, in many situations this is not the case. Many projects are let out with unrealistic completion time thus making it nearly impossible to complete the project in time. Sometimes the so-called extensions of time actually reflect the realistic time that should have been allowed for the completion of a project.<br />
<br />
A realistic time for completion of a project needs to be supported by a well-prepared works programme showing the method(s), arrangements, order and timing for all the activities of the Works. It is a requirement that such a programme be prepared by the Contractor for the approval of the PM.<br />
<br />
However, experience shows that PMs do not take enough time and effort to scrutinize the so prepared programme to establish its realism. Most often than not Contractors prepare programmes to fit within the provided time for completion without critically considering a realistic time that they will require to carry out various activities and the entire project. '''As a starting point, the PM should request justification for the proposed programme by the Contractor''' having due regard to the projected productivity of people and equipment.<br />
<br />
From a well-prepared works programme, the PM is required to ensure that the contractor adheres to the programme, and raises queries any time there is slippage by the contractor to follow the approved programme of works. The PM should also check that the revised programme of works which is submitted by the contractor on a monthly basis has included how the contractor is going to recover any lost time.<br />
===Checklist of Actions by PM to Ensure that a Project is Completed on Time===<br />
The checklist below provides actions that need to be taken by the PM to ensure that the Project is completed in Time or well ahead of time:<br />
(a) Ensure that a realistic time for completion of the project is fixed – One should not take just for granted that the time provided in the tender/contract documents is sufficient. Once a PM is appointed for a project he/she first revisit the contract documents to establish their accuracy and realism. Once he/she discovers errors or mistakes he/she has to make request for amendments which have to be approved by TB or if the errors or mistakes are not so serious this will serve as an eye opener of the potential problems likely to occur and therefore the PM can advise ways of overcoming them.<br><br />
(b) Critically scrutinize the programme of works submitted by the contractor together with its subsequent revisions to ensure that it is realistic and presents a logical sequencing and timing for the execution of the activities.<br><br />
(c) Ensure that the amount stated in the SCC is deducted for failure of the Contractor to submit a revised programme of works within the time stated in the SCC. This assumes that PE is paying the contractor on time. This amount will be released once an acceptable revised programme of work is submitted by the contractor.<br><br />
(d) Ensure timely handing over of the site or parts of the site to the contractor. Remember if possession is not given by the date stated in the SCC, the Employer will be deemed to have delayed the start of the relevant activities, and this will be a Compensation Event.<br><br />
(e) Ensure timely issuance of Drawings, Specifications, or instructions required for execution of the Works.<br> <br />
(f) Ensure timely approval and inspection of works carried out by the contractor, particularly those that require inspection and approval before the IPC is released.<br><br />
(g) Ensure that any instruction to the Contractor to uncover or to carry out additional tests upon work is backed up with a proof of unsatisfactory work for if the work ordered to be tested is found to have no defects that may amount to a compensation event.<br><br />
(h) Ensure timely approval of subcontracts proposed by the contractor. If there are reasons for refusal these must be communicated in a timely manner to the contractor as well.<br><br />
(i) Ensure proper co-ordination of the works of other contractors, public authorities, and utilities companies on the site.<br><br />
(j) Ensure timely payment to the contractor, of the advance payment including applicable and all monthly or interim payments.<br><br />
(k) Handle all contractors’ applications for extension of time fairly and expeditiously.<br><br />
(l) Take time and effort to analyze all early warnings submitted by the contractor and establish their possible impact on completion time for the project and find ways in collaboration with the contractor that will mitigate their adverse effects.<br><br />
As a matter of fact, there are many causes of projects delay that are within the Client’s/ PM Control. It should be ensured that delays caused by Client’s action or inaction are kept to a minimum, and allow those that are the result of unforeseen conditions.<br />
==Quality Control==<br />
===The Need for Quality Control for the Construction Projects===<br />
In order to enhance Client satisfaction during a construction project, the project must meet the expected quality. This expected quality can be ensured through quality assurance and quality control activities. The quality control process confirms that the project outcome meets the client’s standards. The quality assurance process checks the quality plan (which includes method of construction and quality of materials) and quality control process to confirm that quality standards are implemented on the project site. <br />
<br />
To improve the quality of construction, understanding the project requirements and standards is essential. The project quality plan should be part of the project construction management plan. The quality control plan defines how quality should be handled throughout the duration of the project. <br />
<br />
The common way of controlling quality is the inspection of the finished parts of the work. The main purpose of quality control through inspections is to minimize the chance of defects before the project is delivered to the owner. Supervision of a construction project is not just as simple as coming up with a construction punch list. Controlling quality means monitoring if the work practice is going as planned or not, examining the quality of the current construction tasks, and providing reports daily for any unsatisfactory work output. <br />
In the water supply and sanitation sector quality assurance is to ensure value for money, reasonable time for project implementation, sustainability of water and sanitation services and reduction of O&M costs. <br />
===Differentiating Quality Assurance from Quality Control===<br />
[[File:Chapter_4_document_7.PNG|750px|link=Chapter_Four:_contract-supervision_and_administration&action#Equation9]]<br><br />
<br />
steps and ensuring safety with the required methods for each one of them.<br />
The main goal of quality control is to ensure that the construction meets standards they specified at the start of the project. <br />
<br />
Figure 4.1 shows the difference between quality control and quality assurance.<br />
The PM role of ensuring that quality requirements of the contract as specified in the drawings and specifications are met, but for better assurance he may request the Contractor to present to him his Quality Assurance Plan so as to give him confidence that indeed a contractor has clear intentions of making sure that quality requirements of the project are being met.<br />
<br />
[[File:Quality_assurance.PNG|600px|center|link=Chapter_Four:_contract-supervision_and_administration&action#Equation9]]<br><br />
<br />
===Checklist of Actions by PM to Ensure that the Project Meets Quality Requirements===<br />
As discussed, before it is the duty of the PM to ensure that the work produced by the contractor is in conformance with the drawings and the specifications provided for the project. The following is a checklist of actions to be taken by the PM in ensuring that the project is executed and completed to the required quality standards:<br />
<br />
(a) Before starting the work, critically scrutinize the drawings and specifications to confirm that they are correct and do not contain any omissions, errors or mistakes. If omissions, mistakes or errors are discovered make an urgent request for amendments which have to be approved by TB.<br> <br />
(b) Work together with the Contractor to prepare a Quality Assurance Plan which shall narrate the scope of the works and the expected quality requirements for the project, as well as the role of the participants in ensuring quality requirements, and daily reporting and documentation required to ensure that indeed the executed works conform to the standards and the specifications. A typical Quality Assurance Plan is attached as Appendix 5.<br><br />
(c) Regularly and on a daily basis, check the work of the contractor to ascertain that it meets the quality requirements as stipulated in the drawings and specifications.<br><br />
(d) Promptly issue a notice to the Contractor to correct any defects found in the works within a set time. If the contractor fails to correct the defect within the time specified in the Notice, the PM should arrange to have the defect corrected and charge the contractor for the same as provided for in the contract, or decide to treat the failure to correct the defect as a fundamental breach of contract as provided for in the contract, and institute measures required towards the termination of the contract.<br><br />
(e) Request the Contractor, on a monthly basis to provide a programme of the activities, which require his specific approval before the contractor is allowed to proceed to execute the ensuing activities. A good example is the prior inspections before casting of concrete. Most work specifications would require the PM to (i) inspect and approve the formwork as well as the reinforcement before casting, and (ii) the physical presence of the PM or his representative during the pouring of concrete. In order for the contractor to proceed with these works at a certain date, it is important that the PM is notified well in advance so that he can make necessary arrangements enabling him to be present at the time and date the activity is planned for execution by the contractor.<br><br />
(f) Where there is proof of or reasons to believe that part of the executed work falls short of the required quality, the PM should instruct the contractor to search for the defect and to uncover and test any works suspected to have a defect.<br> <br />
(g) Before the issuance of the Certificate of Practical Completion, the PM must inspect the works to ensure that they have been executed in conformity with the drawings and specifications. For such inspection a comprehensive check-list of items to be inspected should be prepared well in advance as part of the contract closeout checklist.<br><br />
The quality of projects is one of the traditional and global measures of project performance. For construction projects, the goal and desire of clients, contractors and consultants is to ensure that projects are delivered according to the acceptable and agreed standards. It is the role of the PM to ensure the project meets specified quality standards.<br />
==Cost Control==<br />
===Importance of Cost Control===<br />
[[File:Chapter_4_document_5.PNG|700px|link=Chapter_Four:_contract-supervision_and_administration&action#Equation9]]<br><br />
<br />
The underlying challenge in controlling costs stems from the fact that many clients have limited funds, and budgets are often set at the limit of what is affordable. Cost overruns during the construction phase may seriously over-extend the client financially, to the point where the project may not be finished to the expected standards, or may even have to be abandoned. Clients who have to pay more than they expected are likely to be (very) disappointed; this is a poor outcome. Cost control must be focused on preventing this from happening.<br />
<br />
Many projects in Tanzania and the world over have suffered from cost and time overruns due to factors stemming from poor cost control during the design and project implementation stages. Most PMs and contractors find difficulty in controlling project costs due to problems which include delays by clients to release money, delays to make decision, lack of materials and equipment, bad weather, overlapping of activities, unclear and incomplete drawings, making good defective works, and generally failure to control the productivity of resources. Others are due to theft and vandalism, interference by clients, high labour turnover, and insufficient knowledge on cost control techniques.<br />
<br />
===Project Manager’s Role in Controlling Costs of the Project===<br />
The PM is mandated to control costs for the project i.e., to ensure that the project costs do not exceed the approved budget which would normally be the contractor’s contract figure and a contingency amount provided to cover for unforeseen works or events that could not be reasonably foreseen at the time of award of the contract.<br />
<br />
[[File:Chapter_4_document_4.PNG|750px|link=Chapter_Four:_contract-supervision_and_administration&action#Equation9]]<br><br />
<br />
(c) Adjusting the rates as appropriate if the final quantity of work executed is different from the quantity in the BOQ by a percentage provided in the contract document. This will entail negotiations with the contractor. Where agreement on adjustment for rates cannot be reached, this matter can be referred to the dispute resolution mechanism applicable.<br><br />
(d) Ensuring that before ordering variations for items for which no contractor’s rate is included in the BOQ, he must obtain a quotation from the contractor, check its reasonableness, and fix a rate if it is determined to be unreasonable. The fixed rate by the PM may be a subject of a Claim if the contractor is not satisfied with the fixed rate.<br><br><br />
(e) Ordering the contractor to prepare a cash flow forecast for the project which shall be updated every time the contractor updates the programme of works. This cash flow forecast shall assist the Client to plan and set aside funds for payment to the contractor for the executed works based on PMs Certification.<br><br />
(f) Ensuring that Contractor’s submitted monthly statements of the work executed are properly scrutinized to establish the correctness of the executed works. He shall ensure that the certification process is completed within 28 days.<br><br />
(g) Keeping all documents and records that were used in the valuation of the works executed by the contractor in the process of certifying amounts to be paid to the contractor.<br><br />
<br />
===Checklist for PM to Ensure Proper Cost Control for the Project===<br />
(a) As discussed above, it is the PM’s responsibility to monitor and control costs of the project. The following is a checklist of actions to be taken by the PM to ensure that the project is executed and completed within the approved budget.<br><br />
(b) Before starting the work, critically review the allocated budget (estimate) for the works to determine its sufficiency to implement the contract. Cost control starts with a well-prepared estimate of the cost for the project.<br><br />
(c) Obtain a cash flow forecast from the contractor, and make the Client aware of his payment obligations based on the forecast. This will enable necessary arrangements to be put in place to enable timely payment to the contractor upon presentation of payment certificates.<br><br />
(d) Keep a close track of all contractors approved claims and adjust the contract prices to reflect increases or decreases in the contract price.<br><br />
(e) Ensure that the TB approval is obtained for any variations and amendments to the contract price.<br><br />
(f) Ensure deduction of retention money as provided for in the contract, and recovery of advance payments (if paid) in the approved payment certificates.<br><br />
(g) Ensure that liquidated damages are deducted from payments due to the contractor for any delay which could not be compensated by the Client.<br><br />
(h) Follow-up with the Client to ensure timely payment of all certified payments to the Contractor. This will prevent payment of interest which ends up increasing the project costs.<br><br />
(i) Cost control is at the heart of successful project implementation. It is therefore critical that the PM implements the action described above to ensure that cost objectives of the project are achieved.<br><br />
==Managing Variation Orders and Contract Amendments==<br />
===Variations Defined===<br />
[[File:Chapter_4document_3.PNG|750px|link=Chapter_Four:_contract-supervision_and_administration&action#Equation9]]<br><br />
<br />
projects, variations can be very significant, whereas on small building contracts they may be relatively minor. <br />
Standard forms of contract generally make express provisions for the PM to instruct variations. Such provisions enable the continued, smooth administration of the works without the need for another contract. Variation instructions must be clear as to know what is and is not included and at times may propose the method of valuation.<br />
<br />
===Valuation of variations===<br />
Variations may give rise to additions or deductions from the contract sum. The valuation of variations may include not just the work which the variation instruction describes, but other expenses that may result from the variation, such as the impact on other aspects of the works. Variations may also (but not necessarily) require adjustment of the completion date. <br />
<br />
Valuations of variations are often based on the rates and prices provided by the contractor in their tender, provided the work is of a similar nature and carried out in similar conditions. If similar types of works to those instructed by a variation cannot be found in the drawings, specifications or bills of quantities, then fair valuation of the contractor's direct costs, overheads and profit is necessary to be made by the PM. <br />
===Source of Conflict on Variations===<br />
<br />
Conflict can arise when work is not mentioned in the BOQ, drawings or specifications. In common law this silence does not mean the contractor has an automatic right to claim for extra payment. The client is not bound to pay for things that a reasonable contractor must have understood were to be done but which happen to be omitted from the BOQs. <br />
Where there are items that, whilst they are not expressly mentioned, are nonetheless required in order to complete the works, then the contractor should have included them in their price. For example a conflict can arise when a contractor qualifies that the, 'Supply & Fixing of Door is included' but 'Supply & Fixing of Ironmongery is excluded'. A reasonable contractor should foresee that a door cannot be fixed without hinges – which is a part of the ironmongery. So even if ironmongery is excluded, the contractor cannot expect a variation for any of the items required to fix the doors. <br />
<br />
Variations are often sources of dispute, either in valuing the variation, or agreeing whether part of the works constitute a variation at all, and can cost a lot of time and money during the course of a contract. Whilst some variations are unavoidable, it is wise to minimize potential variations and subsequent claims by ensuring that uncertainties are eliminated before awarding the contract. This can be done by: <br />
(a) Undertaking thorough site investigations and condition surveys,<br> <br />
(b) Ensuring that the project brief is comprehensive and is supported by stakeholders,<br><br />
(c) Ensuring that legislative requirements are properly integrated into the project,<br><br />
(d) Ensuring that risks are properly identified,<br> <br />
(e) Ensuring that designs are properly coordinated before tendering,<br> <br />
(f) Ensuring the contract is unambiguous and explicit,<br> <br />
(g) Ensuring the contractor's rates are clear,<br> <br />
(h) Preparing concise drawings, bills of quantities and specifications, providing for all situations which are reasonably foreseeable.<br><br />
==Monitoring Compliance with Country’s laws==<br />
Construction process in Tanzania is governed by many Laws. Some are expressly stated in the contract document and others are not. It is the duty of the PM to ensure that the execution of the contract is in accordance with Country’s Laws. The notable laws include:<br />
(a) The Contractors Registration Act of 1997 as amended in 2008 (The Contractors Registration Amendment Act, 2008), – with regard to Contractor’s registration, construction site boards and registration of projects. In particular the PM must ensure that the eligibility of the contractor is maintained throughout the period of execution of contract by making sure that the contractor is still registered by the CRB.<br><br />
(b) Relevant Labour Laws – with regard to workers’ employment and working conditions, social security, working hours, welfare and immigration.<br><br />
(c) Laws relating to taxes and duties.<br><br />
(d) The Environmental Management Act 2004, together with the Environmental Impact Assessment Audit Regulations, 2005 as amended in 2018. In particular the PM must ensure that contractor’s work methods and the handling of effluents from the construction sites do not have any negative impact on the environment.<br><br />
(e) To ensure the contractor has an insurance cover for Indemnity against Professional liability and the Occupational Health and Safety Act, 2003 together with the Occupational Safety and Health (Building and Construction Industry) Rules of 2015. The latter is a very important Law which must be observed to ensure health and safety of workers and public. The implementation of this piece of legislation goes with considerable costs on the part of the contract, and there is a tendency of contractors to try to save costs by skipping some of its requirements. It is critical that the PM ensures that the requirements of this law are properly observed and implemented at site.<br><br />
==Managing Project Closure (Finishing of the Project)==<br />
===Project Closure Defined===<br />
<br />
When it comes to project management, closing out a project is not just a matter of executing deliverables. Though the process may seem tedious or overly administrative, a formal closure phase ensures all loose ends are tied up, documentation is signed and approved, contractors are paid, and everyone is on the same page.<br />
<br />
The closing phase also gives you the opportunity to review and evaluate the project’s success (or failure), which is crucial for planning and more successfully executing projects in the future.<br />
<br />
The closing phase of project management is the final phase of the project lifecycle. This is the stage where all deliverables are finalized and formally transferred, and all documentation is signed off, approved, and archived. The project closure process ensures that: <br />
(a) All work has been completed according to the project plan and scope.<br><br />
(b) All project management processes have been executed.<br><br />
(c) One has received final sign-off and approval from all parties.<br><br />
The project management closure process also gives the team the opportunity to review and evaluate the project’s performance to ensure greater success in future projects. <br />
===Importance of Closing a Project===<br />
<br />
Without a formal project closing process, one risks letting crucial details fall through the cracks, which can result in confusion, a never-ending project, dissatisfied clients, and even liability issues. Project closure helps to avoid:<br />
(a) Repeating mistakes in future projects and pertinent objectives;<br><br />
(b) Having final products or deliverables without dedicated support and resources;<br><br />
(c) Failing to identify the team or individuals who will own and maintain the solution following final delivery; and<br> <br />
(d) Creating liability issues resulting from incomplete payments, contracts, or deliverables<br><br />
<br />
Following a clear project closure plan helps to properly transition the solution to the client or end-user. This process ensures that the final stakeholders have the information, resources, and training to successfully manage and use the end product. The project closure process also ensures that the project is formally completed and is no longer considered a project, allowing one to hand the reins over to the correct team in charge of managing and maintaining the project’s outputs.<br />
By officially closing a project, one minimizes risks, increases client satisfaction, and ensures all parties are on the same page. In other words, a project closure is a process one cannot afford to skip.<br />
===Steps to Closing a Project=== <br />
The closing phase of a project involves several steps. Work through the following checklist to ensure the project is successfully completed.<br />
<br />
(a) '''Formally transfer all deliverables''': The first step to” closing out’’ a project is to finalize and transfer the project deliverables to the client. The PM should together with the Contractor go through the project plan to identify all deliverables and make sure they have been fully completed and handed over.<br />
<br />
[[File:Chapter_4_document_2.PNG|750px|link=Chapter_Four:_contract-supervision_and_administration&action#Equation9]]<br><br />
<br />
(d) '''Release resources''': Formally release resources from the project, including contractors, team members, and any other partners. Notify them of the end of the project, confirm any final payments or obligations, and officially release them so they are free to work on other projects.<br />
(e) '''Conduct a post-mortem''': A post-mortem or project review is one of the most valuable steps of the project closure process. This is the time to review the successes, failures, and challenges of the project and to identify opportunities for improvement in going forward .<br />
<br />
As one begins the post-mortem, there is a need to conduct a performance review of the project. In other words, it is necessary to calculate the project’s performance in terms of cost, schedule, and quality.<br />
<br />
Next, conduct a survey or hold a meeting with the project management team to get feedback on how the project went. These individual answers will help paint a more comprehensive picture of the project’s performance. The team should consider the following questions: <br />
* What went well?<br />
* What were the challenges or failures?<br />
* How well did the team communicate?<br />
* Did the team follow the outlined processes and plan?<br />
* Was the client satisfied with the results?<br />
* What would one change or improve for future projects?<br />
With the project performance and feedback in mind, one can then identify lessons learned and opportunities for the future. One needs to keep in mind that the goal of a post-mortem is not to assign blame for any mistakes. Instead, it is a learning opportunity for everyone to improve in future projects. It is good to document the project review with the performance measurement, feedback, and improvement plan.<br />
* '''Archive documentation''': Once a project post-mortem is completed proceed to finalize all documentation (contracts, project plans, scope outline, costs, schedule, '''as built drawings''' etc.) and index them in the Organization archives for later reference. Keep clear notes on the project’s performance and improvement opportunities so that can be easily referenced and implemented in similar projects in the future.<br />
* '''Celebrate''': Finally, do not forget to celebrate! The end of a project is a big accomplishment and represents the culmination of many hours of hard work and dedication from a team of contributors. An end-of-project party is a great way to acknowledge your team’s hard work and increase morale to perform better in future projects<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter_Three: contract_management|Chapter Three: contract management]] << >> Next Page: [[Chapter Five: essential basic field construction skills|Chapter Five: essential basic field construction skills]]<br />
<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_Nineteen:_Community_Participation_and_Compliant_Redressal_System_in_Operation_and_Maintenance_of_Water_Supply_and_Sanitation_ProjectsChapter Nineteen: Community Participation and Compliant Redressal System in Operation and Maintenance of Water Supply and Sanitation Projects2022-07-16T15:39:42Z<p>Juma: /* Redressal System */</p>
<hr />
<div>= Chapter Nineteen: Community Participation and Compliant Redressal System in Operation and Maintenance of Water Supply and Sanitation Projects=<br />
<br />
== Institutional Roles and Responsibilities ==<br />
<br />
The Ministry, Water Utility/Agency, Local Governments and Communities cannot succeed on their own. They need to co-operate in the whole process of provision of water supply and sanitation services. In ensuring co-operation, each stakeholder should understand the roles and responsibilities they can play in the overall process. Other internal and external stakeholders may include line departments/sections responsible for O&M in the utility/agency, training institutions, and the local private sector and NGOs. In this context, community has a great role in operation and maintenance of the water supply and sanitation projects in ensuring sustenance of services. <br />
<br />
=== Roles of Ministries ===<br />
(a) Coordination of various ministerial departments, i.e. MoW, PO-RALG, MoEST, MoW<br><br />
(b) Provide managerial and technical backstopping on implementation of water and sanitation projects in the community,<br><br />
(c) Facilitate in establishing clear communication lines between water committees with service providers and any agency offering backstopping skills,<br><br />
(d) Provide frameworks to the water organizations on tariff setting in water and sanitation projects that is undertaken by EWURA and RUWASA,<br><br />
(e) Undertaking major repairs and augmentations,<br><br />
(f) Review of the operation and maintenance manual,<br><br />
(g) Review of aspects of sustainability of water supply and sanitation projects,<br><br />
(h) Allocating special funds to execute contingency plans so that the water supply schemes are not affected by inadequate power supply, adverse seasonal conditions like drought periods and natural calamities like earthquake, floods, etc.<br />
<br />
=== Roles of Urban and Local Government Authorities ===<br />
(a) Sensitize communities in contributing towards meeting O&M costs,<br><br />
(b) Facilitate in ensuring security and safety of water sources and supply systems,<br> <br />
(c) Support management of water and sanitation projects,<br><br />
(d) Preparation of by-laws,<br><br />
(e) Liaising with Ministry of Lands regarding water sources conservation.<br />
<br />
=== Roles of Basin Water Boards ===<br />
<br />
(a) Provision of technical backstopping on implementation of water supply and sanitation schemes, especially in the aspect of water sources and adaptation to climate change impacts,<br><br />
(b) Water sources protection and pollution control,<br><br />
(c) Provide guidelines and standards for construction and maintenance of water source structures,<br />
(d) Approve, issue and revoke water use and discharge permits (compliance);<br><br />
(e) Monitor and enforce water use and discharge permits and pollution prevention measures;<br><br />
(f) Monitor compliance to the water use and discharge permits granted,<br><br />
(g) Promote water use efficiency to all stakeholders,<br><br />
(h) Put a mechanism to ensure that, the infrastructure of water management are properly<br> maintained and a comprehensive preventive maintenance system is in place,<br><br />
(i) Develop its own water quality-monitoring programme, adhere to it and publish the results for the public,<br><br />
(j) Put in place and publish a workable water demand management system,<br><br />
(k) Put in place mechanisms for water sources protection and conservation of the environment/catchments.<br />
<br />
=== Roles of the Regulators (EWURA and RUWASA) ===<br />
<br />
In Tanzania, two regulators can be identified for urban and rural and suburban areas respectively and these are EWURA and RUWASA.<br />
<br />
==== Energy and Water Utilities Regulatory Authority (EWURA) ====<br />
The roles of EWURA for urban and National WSSA including the following in relation to water supply and sanitation services shall be to:<br><br />
(a) Exercise licensing and regulatory functions in respect of water supply and sanitation services;<br> <br />
(b) Establish standards relating to equipment attached to the water and sanitation system;<br> <br />
(c) Establish guidelines on tariffs chargeable for the provisions of water supply and sanitation services;<br> <br />
(d) Approve tariffs chargeable for the provision of water supply and sanitation services;<br> <br />
(e) Monitor water quality and standards of performance for the provision of water supply and sanitation services;<br> <br />
(f) Initiate and conduct investigations in relation to the quality of water and standards of service given to consumers;<br> <br />
(g) Conduct studies necessary for administrative or management purposes;<br> <br />
(h) Collect and compile data on licensees as it considers necessary for the performance of its functions;<br> <br />
(i) Issue orders or give directions to any person granted a license in respect of a regulated activity under this Act or other written law;<br><br />
(j) Charge levies, and fees applicable to Water Authority and other sector participants in respect of regulatory activities of the EWURA charged in accordance with section 41 of the Energy and Water Utilities Regulatory Authority Act;<br> <br />
(k) Establish or approve standards and codes of conduct in respect of: (i) licensees; (ii) consumers; and (iii) public safety;<br><br />
(l) Promote the development of water supply and sanitation services in accordance with recognized international standard practices and public demand;<br> <br />
(m) Prescribe rules and declaration and cause the same to be published in the Gazette and in at least one Kiswahili and one English newspaper circulating in a water authority’s area of jurisdiction; and <br><br />
(n) Perform other functions which are incidental or ancillary to the major functions. <br />
<br />
==== Roles of Rural Water and Sanitation Agency (RUWASA) ====<br />
The roles of RUWASA are as outlined in the water supply and sanitation Act No. 5 of 2019 follows:<br />
<br />
(a) Development and sustainable management of rural water supply and sanitation projects.<br> <br />
(b) Plan, design, construct and supervise rural water supply projects;<br> <br />
(c) Conduct ground water survey including prospecting and explorations, and undertake drilling operations including water well flushing and pumping test, and rehabilitation of water wells;<br> <br />
(d) Design and construct dams of different types and carry out geotechnical and soil investigation for dam construction and other civil engineering structures;<br> <br />
(e) Monitor and evaluate performance of community organizations in relation to rural water supply and sanitation services;<br><br />
(f) Promote and sensitize rural communities on sanitation, hygiene education and practice as well as protection and conservation of rural water sources;<br> <br />
(g) Provide financial and technical support to community organizations (CBWSOs) for major maintenance of rural water supply schemes;<br> <br />
(h) Provide support to community organizations in relation to management, operation and maintenance of rural water supply schemes;<br><br />
(i) Advise the Minister on issues related to rural water supply and sanitation;<br> <br />
(j) Facilitate participation of communities in the identification, planning, construction and<br><br />
(k) Management of rural water and sanitation projects;<br> <br />
(l) Facilitate private sector engagement in the provision of the rural water supply and sanitation services;<br> <br />
(m) Facilitate training and capacity building to community organizations in financial, technical and management of rural water supply schemes;<br><br />
(n) Register and regulate the performance of community based water supply organizations.<br />
<br />
=== Roles of Water Supply and Sanitation Authorities ===<br />
(a) Monitor operations and maintenance of the water and sanitations networks and respond immediately on any system default,<br><br />
(b) Implement the tariffs set by the regulator (EWURA/RUWASA) in accordance with the type of the water supply and sanitation projects,<br><br />
(c) Study community perception towards the services provided,<br><br />
(d) Redress/Mitigate community complaints on the services provided,<br> <br />
(e) Collaborate with LGAs and communities (CBWSOs) in running the water supply and sanitation projects,<br><br />
(f) Access managerial and technical backstopping on implementation of water supply and sanitation projects in the community from regulators (EWURA/RUWASA),<br><br />
(g) Establish clear communication lines between the CBWSOs and service providers and any agency offering backstopping skills,<br><br />
(h) Rehabilitate dilapidated infrastructure.<br />
<br />
<br />
== Community Participation and Motivation in Maintenance of Water Supply and Sanitation Projects ==<br />
<br />
The task is to build confidence and general awareness among the community for taking up the management of water facilities for their satisfaction water supply protection and sustainability of system. Community mobilization can be taken up through different activities and with different focus groups. Upon undertaking such activities, the community may contribute the following:<br><br />
(a) Participate in conservation of water sources, water supply and sanitation infrastructures,<br><br />
(b) Pay for water supply and sanitation services provided,<br><br />
(c) Provide feedbacks to the water supply utility/agency on the functionality or failure of the water supply and sanitation projects.<br />
<br />
=== Roles of Service Providers ===<br />
(a) Ensure availability of appropriate and quality system spare parts and tools,<br><br />
(b) Provide technical backstopping on operationalization and maintenance of water supply and sanitation schemes in the community.<br />
<br />
=== Roles of Academic and Research Institutions ===<br />
(a) Collaborate and coordinate researches on finding solutions pertaining to socio-economic and technological factors influencing or affecting the sustainability of water and sanitation projects,<br><br />
(b) Training operators in management of the projects,<br><br />
(c) Innovating new means of enhancements of water supply and sanitation projects.<br />
<br />
=== Roles of NGOs and CBOs ===<br />
(a) Sensitize community to trigger the sense of ownership and protection water and sanitation facilities,<br><br />
(b) Educate community on integration and good water and sanitation practices,<br> <br />
(c) Provide managerial and technical backstopping on implementation of water and sanitation schemes in the community as provided for in the Water Supply and Sanitation Act No. 5 of 2019.<br />
<br />
=== Roles of CBWSOs ===<br />
<br />
The CBWSOs are legal water organizations established for the purpose of operating and managing water supply projects. The recent water sector reform through Water Act No. 5 of 2019 has changed the organization structure and administrative systems. Technical teams comprising of a technician and an accountants at certificate levels who are employed rather than volunteers, now manage these organizations. The role of water committee comprising of representative from beneficiaries is to monitor the efficiency of the technical team.<br />
<br />
Roles of CBWSOs includes to:<br> <br />
(a) Own movable and immovable properties including public taps and waterworks; <br><br />
(b) Manage, operate and maintain public taps and waterworks and provide an adequate and safe supply of water to its consumers;<br> <br />
(c) Determine rules for the use of public taps and or waterworks by consumers;<br> <br />
(d) Install water meters for the purpose of measuring the amount of water supplied to a public tap or a consumer;<br><br />
(e) Charge consumers for the water supplied from public taps and or waterworks;<br> <br />
(f) Limit the access of any persons from the water source, public taps or from supplies from the waterworks who are not complying with the rules, regulations or the constitution of the community organization;<br> <br />
(g) Consult and cooperate with the village council or any other institution responsible for land to plan and control the use of land in the immediate vicinity of the water points and or waterworks; and <br><br />
(h) Do such other thing or enter into any transaction which, in the opinion of the Community Water Committee is necessary and proper in carrying out its obligations.<br />
<br />
== Complaint Communication and Redressal System ==<br />
<br />
Deficiency in maintenance and service delivery may occur in water supply and sanitation projects components maintained. In such a complex scenario, general public who intend to make a compliant on deficiency in maintenance of the project may not be aware who is the concerned authority to set right the deficiency and to whom to make the complaint. RUWASA will be the body which will review any appeals from the consumers.<br />
<br />
=== Complaint Communication ===<br />
<br />
The procedure for lodging complaints should be as follows:<br><br />
(a) A complaint cell may be created in the water supply utility and RUWASA office equipped with necessary soft & hard skills duly giving adequate publicity about the nature of the complaint can be made and also the details such as E-mail address/ fax number/ telephone number/ postal address, etc. of the complaint cell,<br><br />
(b) As being done in the case of emergency need of Police/ Fire service , a three digit toll free number may be assigned for lodging urgent complaint through Telephone/ mobile phone,<br><br />
(c) A member of general public who instantly comes across any leakage/ overflow or any deficiency in maintenance of the schemes may lodge a complaint to the three digit number,<br><br />
(d) Immediately after receipt of the complaint, a compliant number will be assigned and informed to the complainant, if the complaint is received by phone/E-mail.<br />
<br />
=== Redressal System ===<br />
<br />
Complaint received may be examined and determine which maintenance agency/unit is within an hour of receipt of the compliant. It may be informed either by phone/ e-mail to the department/utility/WSSA/RUWASA or to the local area (CBWSOs). If the complaint is received through post, also the above system may be adopted.<br><br />
(a) The respective maintenance agency should intimate the stage of action taken the next day to the complaint cell,<br><br />
(b) The cell will create necessary files/ documents in computer and register the name and address of complainant, mode of receipt of compliant, assigning of complaint number, agency who is attending the complaint, present stage of action taken, etc.,<br><br />
(c) The complaint cell may inform the facts such as who is the agency attending the complaints, their contact number and stage of action taken to the complainant, the next day after receipt of complaint (by phone/SMS/E-mail),<br><br />
(d) The respective maintenance agency should report final stage of action taken within two days to the complaint cell (by phone/SMS/E-mail),<br><br />
(e) The complaint cell may inform the final action taken, to the complainant immediately after receipt of details received from the concerned maintenance agency,<br><br />
(f) EWURA or RUWASA may review the status of complaints received every week.<br />
<br />
<br />
Previous Page: [[Chapter Eighteen: Revenue Including billing and Collection]] << >> Next Page: [[References:_References]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Eighteen:_Revenue_Including_billing_and_CollectionChapter Eighteen: Revenue Including billing and Collection2022-07-16T15:38:20Z<p>Juma: /* Delayed Payments */</p>
<hr />
<div>=Chapter Eighteen: Revenue Including billing and Collection=<br />
<br />
Revenue management system is an important aspect of any water supply system as it governs the financial and technical sustainability to the utility. Apart from fixing a tariff structure, billing and collection of revenue play an important part in the overall administration.<br />
<br />
== Tariff Fixation ==<br />
<br />
Tariffs are instruments for recovering the cost of providing adequate water supply service to customers and must reflect not only the fixed costs of the supply system but also its operating expense and long-term sustainability. Tariff rates must satisfy the following requirements:<br><br />
(a) '''Adequacy:''' The revenues generated from a water rate schedule must be sufficient to meet the revenue requirements of the Utility. The rates should be able to promote the Utility’s financial viability and growth,<br><br />
(b) '''Public Service:''' The tariffs must be set at a reasonable level that reflects the Utility’s role as a public utility providing a public service,<br><br />
(c) '''Equitable and Socialized Pricing:''' The tariffs must equitably distribute the cost of the service to all classifications and sizes of connections. Their structure should define a relatively low fixed rate for some minimum level of consumption to benefit the low income users, and higher rates for those who use greater quantities of water,<br><br />
(d) '''Affordability Level:''' The tariff rates must be kept affordable to the Low Income Group (LIG). For this reason, the minimum and maximum charges may be specified for the average income of the LIG within the service area,<br><br />
(e) '''Water Conservation:''' The tariff rates must encourage the wide water usage needed to attain economies of scale, but must also discourage unreasonable and wasteful usage of water,<br><br />
(f) '''Enforceability:''' The tariff rates must be fair, reasonable and transparent. They should be justifiable and acceptable to the consumers.<br />
<br />
For this reason, the practice is for the water tariff to be fixed by the Utility in consultation with the users, considering basically the capacity of the users to pay and costs of the O&M, as well as other relevant factors.<br />
(Source: https://www.slideshare.net/esmeraldoerandio/rural-water-supply-volume-iii-operation-and-maintenance-manual-PHILLIPINES).<br />
<br />
The water supply charges in urban utilities are proposed by the respective utility and approved by EWURA after completing its regulatory procedures. Tariffs in small towns and rural water supply schemes are approved by RUWASA. Tariff setting takes into account the ability of the system to meet the following expenditures:<br><br />
(a) O&M cost (Recurring and non- recurring establishment cost),<br><br />
(b) Depreciation,<br><br />
(c) Debt services and doubtful charges,<br><br />
(d) Asset replacement fund.<br />
<br />
It is recommended that the tariff structure should be reviewed periodically/ annually to cater for changes in the market.<br />
<br />
== Categories of Consumers ==<br />
<br />
Among the different categories, the domestic consumers are the privileged class of people in terms of supply of water and of consumer’s collection of taxes mainly because they use water for their healthy existence. The other categories include commercial complexes, Hotel/restaurants, Industries/ Bulk consumers/ offices/institutions; largely use water and are usually charged with a higher tariff. Therefore, the distribution of cost incurred on the maintenance of such a system for each class of consumers including un-privileged people should be logically and appropriately determined with reference to the level of service rendered. Finally, a projected income on account of water charges should take into account the various factors itemized in the previous section.<br />
<br />
== Methods of Levying Water Charges ==<br />
<br />
The methods of levying water charges can be any one or more of the following:<br><br />
(a) Metered consumption of water,<br><br />
<br />
(b) Non-Metered System:<br><br />
(i) Fixed charge per house per month (depending upon the size of the house) or per connection per month, or<br><br />
(ii) Fixed charge per family per month or per tap per month/per household, or<br><br />
(iii) Percentage of payable value of the property.<br />
<br />
== Distribution of Bills to the Consumer ==<br />
<br />
The distribution of bills to customers may be done either electronically through customer’s mobile phone (especially in urban areas) or can be done by operators specially authorized for this purpose or meter readers and bills can be distributed at the time of meter reading.<br />
<br />
=== Payment of Bills by Consumer ===<br />
<br />
The payments can be accepted at any one or more ways of the following:<br><br />
(a) Counters at water utility office,<br><br />
(b) At bank / banks authorized for accepting payments,<br><br />
(c) Via customer mobile number through authorized Commercial Banks,<br><br />
(d) Door to door/on the spot recovery by authorized person (in case of delayed/accumulated bills),<br><br />
(e) Payment via the mobile phones using MPesa, Tigo Pesa, T-Pesa, Halopesa or Airtel Money for Tanzania (2019).<br />
<br />
=== Delayed Payments ===<br />
<br />
Since water is being treated as a commodity consumed, the advance billing is generally not carried out. It is therefore ‘a must’ to levy penalty/interest on the delayed payments of the bills. Computerization overcomes many of the defects in the manual system, is fast and gives control on the system.<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Seventeen: Water Audit and Leakage Control]] << >> Next Page: [[Chapter Nineteen: Community Participation and Compliant Redressal System in Operation and Maintenance of Water Supply and Sanitation Projects]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Seventeen:_Water_Audit_and_Leakage_ControlChapter Seventeen: Water Audit and Leakage Control2022-07-16T15:37:12Z<p>Juma: /* Benefits of Water Audit and Leak Detection */</p>
<hr />
<div><div style="text-align:justify"><br />
=Chapter Seventeen: Water Audit and Leakage Control=<br />
<br />
==Definition of Water Audit==<br />
<br />
Water audit of a water supply scheme can be defined as the assessment of the capacity of total water produced by the Water Supply and Sanitation Authority (WSSA)/Community Based Water Supply Organization (CBWSO) and the actual quantity of water distributed throughout the area of service by the WSSAs/CBWSOs. Therefore, this leads to an estimation of the losses otherwise known as Non-Revenue Water (NRW) and the Un-accounted-For Water (UFW). NRW is the expression used for the difference between the quantity of water produced (or supplied) and the quantity of water billed or accounted for. The unaccounted-for water (UFW) is the part of the NRW that remains after deducting the unbilled but authorised consumption. Examples of such consumption are the water used for backwashing of filters, flushing of pipes, washing streets, firefighting, public taps and fountains, parks etc. The volume used for these purposes is usually marginal compared to the total water supplied, which makes the difference between UFW and NRW small in many systems.<br />
<br />
Water audit in a water supply system is broadly, similar in nature to the energy audit and determines the amount of water lost from source of water to the distribution system including losses at users’ taps due to leakages and other reasons such as theft, unauthorized or illegal withdrawals from the systems and thus, these losses costs the water utility. Complete water audit plan gives a detailed profile of a water supply system including its distribution system and water users, thereby facilitating easier and effective management of the resources with improved reliability. It helps in undertaking a correct diagnosis of the problems faced and suggests optimum solutions. It is also an effective tool for realistic understanding and assessment of the system’s performance level, efficiency of the service and the adaptability of the system for future expansion & rectification of faults during modernization. <br />
<br />
Elements of the water audit include a record of the amount of water produced, total water supplied, water delivered to metered users, water delivered to unmetered users, water losses and suggested measures to address water loss (through pinpointing & minimising leakages and other unaccounted for water losses). <br />
<br />
Generally, the following are the recommended steps of a water audit exercise:<br />
<br />
(a) To conduct a water audit of the water distribution system and water accounting practices etc. and validation,<br><br />
(b) Preparation of worksheets and sample calculations for each step of the water audit,<br><br />
(c) To identify, measure and verify all water consumption and losses,<br><br />
(d) To identify and control apparent losses in metering and billing operations, and recover missed revenues,<br><br />
(e) To implement a leakage and pressure management programme to control real losses, conserve water and contain costs,<br><br />
(f) Develop plans to assemble the proper resources, information and equipment to launch a sustained accountability and loss-control programme,<br><br />
(g) Prepare a game-plan for setting short, medium and long-term goals and estimate the returns on investment.<br><br />
<br />
Leak detection programme is a tool that helps in minimizing leakages and tackling small problems before they scale-up to major ones. These programmes lead to:<br />
<br />
(a) Reduced water losses,<br> <br />
(b) Improved reliability of the supply system,<br> <br />
(c) Enhanced knowledge of the distribution system,<br> <br />
(d) Efficient use of existing supplies,<br> <br />
(e) Better safeguards to public health and property,<br> <br />
(f) Improved public relations,<br> <br />
(g) Reduced legal liability,<br><br />
(h) Reduced disruption, thereby improving levels of service to customers, and<br><br />
(i) Improved financial performance.<br><br />
==Application of Water Audit==<br />
Application of water audit process in domestic/ municipal sector may consist of various steps including water audit, interventions for water conservation/leakages/ losses control, regulatory framework & community involvement and evaluation of effectiveness of the interventions undertaken.<br />
===Water Audit Methodology===<br />
A reliable water audit methodology was developed jointly by the American Water Works Association (AWWA) and International Water Association (IWA) in the year 2000. The water balance of this methodology is given in Table 17.1 and it shows schematically, the various components in which water volumes (typically one year) are tracked.<br />
<br />
[[File:Chapter_17_document_1.PNG|600px|center|link=Chapter_Seventeen:_Water-Audit_and_Leakage_Control&action]]<br><br />
<br />
The water balance tracks – from left to right – how a water supply agency/ utility supplies water volumes from source to customer and provides the format for the utility to quantify amounts of billed and lost water. Fundamental to the AWWA/IWA Water Audit methodology is the distinction that treated drinking water goes to two places: authorized consumption by consumers (its intended use) and a portion to losses (through inefficiencies). Within the component of losses, two broad types exist:<br />
<br />
''<br />
'''Apparent Losses''''' are the “paper” losses that occur in utility operations due to customer meter inaccuracies, billing system data errors and unauthorized consumption. In other words, this is the water that is consumed but is not properly measured, accounted or paid for. These losses cost utilities revenue and distort data on customer consumption patterns.<br />
<br />
''<br />
'''Real Losses''''' are the physical losses of water from the distribution system, including leakage and storage overflows. These losses inflate the water utility’s production costs and stress water resources since they represent water that is extracted and treated, yet never reaches beneficial use.<br />
===Planning and Preparation===<br />
Planning and preparation shall include the data collection element and the preparation of sketch plans for the distribution centres and other locations for the installation of the flow meters. Also included within this shall be the confirmation of flow rates for the bulk meter locations which has been carried out by the use of portable ultrasonic flow meters.<br />
<br />
'''(a) Preliminary Data Collection'''<br><br />
The water distribution drawings are to be studied and updated. The number of service connections is to be obtained and in the drawings of the roads, the exact locations of service connections marked. The district and sub-district boundaries are suitably fixed taking into consideration the number of service connections, length of the mains, and pressure points in the main. The exact locations of valves, hydrants with their sizes should be noted on the drawings.<br />
<br />
The above activities will help in planning the conduct of sounding of the system for leaks or for fixing locations for conduct of pressure testing in intermittent water supply system before commencement of leak detection work or for measuring pressure and leak flow in the continuous water supply system.<br />
<br />
'''(b) Pipe Location Survey'''<br><br />
Electronic pipe locators can be used during survey. These instruments work on the principle of Electromagnetic signal propagation. It consists of a battery operated transmitter and a cordless receiver unit to pick up the signals of pre-set frequency. There are various models to choose from. Valve locators are metal detectors that are available which can be used to locate buried valves.<br />
<br />
===Verification and Updating of Maps===<br />
<br />
''Mapping and inventory of pipes and fittings in the water supply system'': If the updated maps are available and bulk meters are in position, network survey can be taken up as a first step. Otherwise maps have to be prepared and bulk meters fixed. The agency should set up routine procedures for preparing and updating maps and inventory of pipes, valves and consumer connections. The maps shall be exchanged with other public utilities and also contain information on other utility services like electricity, communications etc.<br />
===Installation of Bulk Meters===<br />
The major activity during the overall water audit will be bulk meter installation at those points on the distribution network where water enters the system. It is expected that bulk meters will be required at the following locations:<br />
<br />
(a) All major system points (e.g. raw water inlet, clear water outlet, main distribution branch, SRs, etc.),<br><br />
(b) Major transfer mains which are expressly required for audit,<br><br />
(c) At distribution centres, the most appropriate meter position is on the outlet pipe from the service reservoir. Installation of a meter at this point will allow measurement of flows into the system not only if supplies are coming from the service reservoir but also if they are being pumped directly from the clear water reservoir (CWR),<br><br />
(d) The size of the meter can be determined by flow of water, size of pipeline and meter manufacturer’s specifications having consideration of the following:<br><br />
<br />
(i) Number of properties served,<br><br />
(ii) Per capita consumption (litres/person/day),<br><br />
(iii) Population density,<br><br />
(iv) Meter manufacturer’s specifications.<br><br />
<br />
Hours of supply-meter sizes must be decided according to current supply hours or size of the pipe. Future changes to the system operation may require the substitution of some bulk meters with those of a smaller size, due to reductions in flow over longer supply hours.<br />
<br />
It is expected that bulk meters installed in locations where supply is rationed will tend to over-read. This is because when supplies are turned on, the air present in the pipes can cause the meter to spin. This problem may be overcome through the use of combined pressure and flow loggers. Flow through the meter will be recorded in the normal way. However, analysis of the pressure and flow plots together will enable the identification of that period of time when a flow is recorded at zero pressure. This time should correspond to the period when the meter is spinning, and the true flow through the meter over a period of time can therefore be calculated.<br />
===Monitoring of the Production System===<br />
The assessment of the leakage rates through the various features of the water supply system should be undertaken. These will include raw water transmission system, reservoirs, treatment plant, clear-water transmission system, inter-zone transmission system, boreholes/ sources of water supply. Details are provided in Chapter Seven and Nine.<br />
===Transmission System===<br />
The methodology adopted to make an assessment of the level of losses in the transmission system is to install insertion probes/bulk meter at both ends of each section of the main being monitored, thus monitoring both the inflow and outflow of the section. This monitoring should be done for a minimum period of 7 days. The difference of inflow and outflow will indicate the losses in the transmission main. The advantage of this method is that the trunk main need not be taken out of service.<br />
<br />
Another way to measure leakage is to close two valves on the main. 25mm tapping are made on either side of the upstream valve and a small semi-positive displacement flow meter is connected between the two tapings. Flow through this meter will indicate the leakage in the main between the two closed valves. It must be ensured that the downstream valve is leak proof. The approximate position of any leakage measured can be determined by the successive closing of sluice valves along the main in the manner of a step test.<br />
===Reservoirs===<br />
<br />
To reduce or avoid any leakage or consequent contamination in reservoirs, the reservoirs should be periodically tested for water tightness, drained, cleaned, washed down and visually inspected. The losses in water storage structures can be monitored for a particular period noticing the change in the level gauges when the structure is out of use i.e. there is no inflow and outflow of water during this monitoring period.<br />
<br />
The most reliable method for measurement of leakage from a service reservoir is to fill it to full level and isolate it from supply and to measure change in level over suitable time period. Suitable equipment to measure reservoir levels could be chosen like:<br />
<br />
(a) Sight gauges,<br><br />
(b) Water level sensors (as per manufacturer’s instruction),<br><br />
(c) Float gauges,<br><br />
(d) Submersible pressure & level transducers (as per manufacturer’s instruction).<br><br />
===Treatment Plant and Performance Monitoring===<br />
Performance monitoring refers to the assessment of water quality delivered from a device/process, and it requires analysis of a number of different parameters that are often dependent on the final use of the water. Users are advised to consult the relevant water quality standards or requirement on the uses of the water. The losses in a treatment plant can be monitored by measuring the inflow into the plant and outflow from the plant with the help of mechanical electronic flow recorders. The difference of inflow and outflow for the monitoring period will indicate the water losses in the plant. In case the loss is more than the design limit, further investigation should be carried out for remedial measures.<br />
<br />
Performance monitoring refers to the assessment of water quality delivered from a device/process, and it requires analysis of a number of different parameters that are often dependent on the final use of the water. Users are advised to consultant the relevant water quality standards or requirement on the uses of the water.<br />
===Boreholes===<br />
In conjunction with the programme of bulk meter installation is the operation to monitor the approximate yield from the boreholes. This exercise can be carried out by the installation of semi-permanent meters to the boreholes on a bypass arrangement similar to that for the bulk meters. This can be effected by utilizing the smaller diameter bulk meters. Insertion probes or the portable ultrasonic flow meters will be used for measurement of flows on the common feeder mains.<br />
===Monitoring of the Distribution System===<br />
Distribution system comprises of service reservoirs, distribution mains & distribution lines. Metered, unmetered (flat rate), public stand posts, hydrants, illegal connections water audit of the distribution system consists of:<br />
<br />
(a) Monitoring of flow of water from the distribution point into the distribution system,<br />
(b) Consumer meter sampling i.e. District Metering Area (DMA) and estimating metered use by consumers, if any,<br />
(c) Estimating losses in the appurtenances and distribution pipeline network including consumer service lines.<br />
<br />
====Monitoring Flow into the Distribution System====<br />
A bulk meter of the appropriate type and size is installed at the outlet pipe of the service reservoir or at the point where the feeding line to the area branches off from the trunk main. If water from the DMA flows out into another zone a valve or meter is to be installed at this outlet point.<br />
<br />
Furthermore, DMAs (District Metered Areas) can be helpful in managing pressures well as NRW. At the inflow to the DMAs, pressure reducing valves can be installed, and the pressure in every DMA can be adjusted to the required level. There is no ideal size for a DMA. The size, whether it is 500 or 5,000 service connections, is always a trade-off. The decision has to be made on a case-by-case basis and depends on a number of factors (e.g., hydraulic, topographic, practical and economic).<br />
<br />
The size of DMAs has an impact on the cost of creating them. The smaller the DMA, the higher the cost. This is because more valves and flow meters will be required and maintenance is costlier. However, the benefits of smaller DMAs are that:<br />
<br />
* New leaks can be identified earlier, which will reduce awareness time;<br><br />
* Location time can be reduced because it will be faster and easier to pinpoint the leak; and<br><br />
* As a by-product, it is easier to identify illegal connections.<br><br />
<br />
Topography and network layout also play an important role in DMA design and size. Therefore, there will always be DMAs of different sizes in a distribution network. An important influencing factor is the condition of the infrastructure. If mains and service connections are fragile, then bursts will be more frequent and the optimal DMA will be relatively small. On the other hand, in areas with brand new infrastructure, DMAs can be larger and still manageable.<br />
<br />
According to the recommendations of the International Water Association’s (IWA) Water Loss Task Force, if a DMA is larger than 5,000 connections, it becomes difficult to discriminate small bursts (e.g. service connection bursts) from variations in customer night use. In networks with very poor infrastructure conditions, DMAs as small as 500 service connections might be warranted. A calibrated hydraulic model should always be used for DMA designs irrespective of the size of the DMAs.<br />
<br />
====Customer Meter Sampling====<br />
Water audit is a continuous process. However, consumers’ meter sampling can be done on a yearly basis by review of all existing bulk and major consumers for revenue. A correlation between the production/power consumed in the factory viz-a-viz water consumption can be evaluated by:<br />
<br />
(a) Sampling of 10% of all bulk and major consumers,<br><br />
(b) Sampling of 10% of small or domestic consumers,<br><br />
(c) Series meter testing of large meters suitably according to standards, calibrated meters.<br><br />
(d) Testing of 1% large and 1% domestic meters,<br><br />
(e) Estimating consumption at a representative 5% sample of Water Points (WPs) and unmetered connections by carrying out site measurements.<br><br />
<br />
All non-functioning and broken meters in the sample areas will be replaced and all meters may be read over a week. This information will be brought together with information derived from the workshop and series testing in order to estimate the average water delivered and correction factors for consumer meters. These factors can then be extrapolated to the rest of the customer meter database.<br />
<br />
====Losses in Customer Service Lines and Appurtenances====<br />
Losses can be calculated by deducting the following from the total quantity by the following:<br />
<br />
(a) Metered consumption,<br><br />
(b) Illegal connection consumption (assuming metered use),<br><br />
(c) PSP use,<br><br />
(d) Free supply, use in public toilets, parks etc.<br><br />
===Analysis===<br />
The information of the results of monitoring the distribution system together with the results of the bulk metering exercise will be consolidated and brought together to produce the water balance report and the overall water audit report. These results may be interpreted in financial terms. Further exercise will be done to classify the water consumed/wasted/lost in financial terms with relation to the current and future level of water charges. This exercise will be carried out as a result of the field tests and the review of existing records forming part of the overall water audit.<br />
<br />
This water audit will provide sufficiently, accurate area wise losses to priorities the area into three (3) categories viz.<br />
<br />
(a) Areas that need immediate leak detection and repair,<br><br />
(b) Areas that need levels of losses (NRW) to be closely monitored,<br><br />
(c) Areas that appear to need no further work at the current time.<br><br />
<br />
It is recommended that cursory investigation should be carried out in the areas that appear to have the least levels of losses (NRW), locating any major leaks, followed by the leak repairs would reduce the losses (NRW) levels further. After water audit of few cities/ villages, it has been reported that the components of NRW may generally be as follows (GoI, 2013):<br />
<br />
(a) Leakage (physical losses) 35 to 50%,<br><br />
(b) Meter under-registration 10 to 15%,<br><br />
(c) Illegal/unmetered connections 3.5 to 6%,<br><br />
(d) Public use 1.5 to 3.5%.<br><br />
==Leakage Control==<br />
The overall objective of leakage control is to diagnose how water loss is caused and to formulate and implement action to reduce it to technically and economically acceptable minimum. Specifically the objectives are:<br />
<br />
* To reduce losses to an acceptable minimum,<br><br />
* To meet additional demands with water made available from reduced losses thereby saving in cost of additional production and distribution,<br><br />
* To give consumer satisfaction,<br><br />
* To augment revenue from the sale of water saved.<br><br />
'''<br />
(a) Water Losses'''<br />
The water losses can be classified into two categories:<br />
<br />
* Physical losses (Technical losses),<br><br />
* Non-physical losses (Non-technical losses/Commercial losses).<br><br />
'''<br />
(i) Physical Losses (Technical Losses)'''<br />
This is mainly due to leakage of water in the network and comprises of physical losses from pipes, joints & fittings, reservoirs & overflows of reservoirs & sumps.<br />
<br />
'''(ii) Non-Physical Losses (Non-Technical Losses)'''<br />
Theft of water through illegal, already disconnected connections, under-billing either deliberately or through defective meters, water wasted by consumer through open or leaky taps, errors in estimating flat rate consumption, public stand posts and hydrants.<br />
'''<br />
(b) Leakage Detection and Monitoring'''<br />
The major activities in the leak detection work in the distribution system:<br />
<br />
* Preliminary data collection and planning,<br><br />
* Pipe location and survey,<br><br />
* Assessment of pressure and flows,<br><br />
* Locating the leaks,<br><br />
* Assessment of leakage.<br><br />
<br />
==Benefits of Water Audit and Leak Detection==<br />
Water audits and leak detection programmes can achieve substantial benefits, including the following:<br />
<br />
'''(a) Reduced Water Losses'''<br />
Water audit and leak detection are the necessary first steps in a leak repair programme. Repairing the leak will save money for the utility, including reduced power costs to deliver water and reduced chemical costs to treat water.<br />
'''<br />
(b) Financial Improvement'''<br />
A water audit and leak detection programme can increase revenues from customers who have been undercharged, lower the total cost of whole sale supplies and reduce treatment and pumping costs.<br />
'''<br />
(c) Increased Knowledge of the Distribution System'''<br />
During a water audit, distribution personnel become familiar with the distribution system, including the location of main and valves. This familiarity helps the utility to respond to emergencies such as main breaks.<br />
<br />
'''(d) More Efficient Use of Existing Supplies'''<br />
Reducing water losses helps in stretching existing supplies to meet increased needs. This could help defer the construction of new water facilities, such as new source, reservoir or treatment plants.<br />
<br />
'''(e) Safeguarding Public Health and Property'''<br />
Improved maintenance of a water distribution system helps to reduce the likelihood of property damage and safeguards public health and safety.<br />
<br />
'''(f) Improved Public Relations'''<br />
The public appreciates maintenance of the water supply system. Field teams doing the water audit and leak detection or repair and maintenance work provide visual assurance that the system is being maintained.<br />
'''<br />
(g) Reduced Legal Liability'''<br />
By protecting public property and health and providing detailed information about the distribution system, water audit and leaks detection help to protect the utility from expensive law suits.<br />
</div><br />
<br />
<br />
<br />
Previous Page: [[Chapter Sixteen: Water Meters, Instrumentation Telemetry and Scada]] << >> Next Page: [[Chapter Eighteen: Revenue Including billing and Collection]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Sixteen:_Water_Meters,_Instrumentation_Telemetry_and_ScadaChapter Sixteen: Water Meters, Instrumentation Telemetry and Scada2022-07-16T15:36:17Z<p>Juma: /* Operation and Maintenance of Flow Meters */</p>
<hr />
<div><div style="text-align:justify"><br />
= Chapter Sixteen: Water Meters, Instrumentation Telemetry and Scada=<br />
<br />
==Water Meters==<br />
<br />
A water meter is a scientific instrument for measurement of the quantity of water distributed to the consumers or sewage pumped. In Tanzania, water meters are used to measure the volume of water used by residential, institutional, industrial, as well as commercial buildings and public water points/kiosks that are supplied with water by a public water supply system. Water meters can also be used at the water source, and throughout a water system to determine flow through that portion of the system. Water meters can be used to measure wastewater quantities. Water meters measure flow in cubic metres (m<sup>3</sup>) on a mechanical or electronic register. Some electronic meter registers can display rate-of-flow in addition to total usage. A water meter also fulfils the need to know accurately the water produced and distributed. Water meter is always specified in two accuracies i.e. lower range and upper range accuracies. The upper range and lower range accuracies are 2% and 5% of the actual quantity respectively for the water meter. <br />
<br />
Water meters having sizes from 15 mm to 50 mm as per TBS standards are considered to be '''Domestic water meters''' and sizes from 50 mm and above as per TBS are considered to be '''Bulk water meters'''. There are different types of water meters such as mechanical water meter, electro-mechanical, ultra-sonic water meters. However, prepaid water meters are highly recommended nowadays for domestic as well as public water points that operate as kiosks. Public water points can have one or more taps.<br />
<br />
=== Sizing of Water Meters ===<br />
<br />
In general the sizing of water meters is done according to the guidelines given in TZS 782-5: 2015- ISO 4064-5: 2014, the main considerations on the characteristics of the water flow and quality have to be known, before a suitable meter type with the right specifications can be chosen to fulfil this task. These are as follows:<br><br />
(a) Water meter has to be selected according to the flow to be measured and not necessarily to suit a certain size of water supply mains,<br><br />
(b) The maximum flow shall not exceed the maximum flow rating,<br><br />
(c) The nominal flow shall not be greater than the nominal flow rating,<br><br />
(d) The minimum flow to be measured shall be within the minimum starting flow of the meter,<br><br />
(e) Low head loss, long operating flow range, less bulky and robust meter shall be preferred.<br />
<br />
=== Installation of Ordinary Water Meters ===<br />
<br />
In order to ensure proper working of the meters, TBS has given guidelines in TZS 782-5: ISO: 4064-5:2015 for their installation as per the drawing given in it. The following guidelines should be borne in mind while installing the meters:<br><br />
(a) Assure accuracy of water meter on a meter test bench at minimum and permanent flow rates before installation,<br><br />
(b) The water meter being a delicate instrument shall be handled with great care. Rough handling including jerks or fall is likely to damage it and affects its accuracy,<br><br />
(c) The meter shall be installed at a spot where it is readily accessible. To avoid damages and over run of the meter due to intermittent water supply system, it is always advisable to install the meter, so that the top of the meter is below the level of the communication pipes so that meters always contain water, when there is no supply in the line. Also, the minimum straight length condition as per the drawing shall be observed,<br><br />
(d) The meter shall preferably be housed in a chamber with a lid for protection; it should never be buried underground nor installed in the open nor under a water tap so that water may not directly fall on the meter. It should be installed inside inspection pits, built out of bricks or concrete and covered with lid. It should not be suspended,<br><br />
(e) The meter shall be so installed that the longitudinal axis is horizontal and the flow of water should be in the direction shown by the arrow cast on the body,<br><br />
(f) Before connecting the meter to the water pipe, it should be thoroughly cleaned by installing in the place of the water meter a pipe of suitable length and diameter and letting the passage of a fair amount of water flow through the pipe work to avoid formation of air pockets. It is advisable that the level of the pipeline where the meter is proposed to be installed should be checked by a spirit level,<br><br />
(g) Before fitting the meter to the pipeline, check the union’s nuts in the tail pieces and then insert the washers. Thereafter, screw the tail pieces on the pipes and install the meter in between the nuts by screwing. In order to avoid its rotation during the operation, the meter should be kept fixed with suitable non-metallic clamps. Care should be taken that the washer does not obstruct the inlet and outlet flow of water,<br><br />
(h) The protective lid should normally be kept closed and should be opened only for reading the dial,<br />
(i) The meter shall not run with free discharge to atmosphere. Some resistance should be given in the down side of the meter if static pressure on the main exceeds 10 m head,<br><br />
(j) A meter shall be located where it is not liable to get severe shock of water hammer which might break the system of the meter,<br><br />
(k) Owing to the fine clearance in the working parts of the meters they are not suitable for measuring water containing sand or similar foreign matter and in such cases a filter or dirt box of adequate effective area shall be fitted on the upstream side of the meter. It should be noted that the normal strainer fitted inside a meter is not a filter and does not prevent the entry of small particles, such as sand,<br><br />
(l) In case of intermittent water supply to SR and schemes with storage at higher elevation, the bulk water meter may be provided with a suitable air valve before the meter in order to reduce inaccuracy and to protect it from being damaged.<br />
<br />
=== Installation of Prepaid Water Meter ===<br />
<br />
The following guidelines should be used while installing the prepaid water meters:<br><br />
(a) Before installing the prepaid meter first check its accuracy on a meter test bench at minimum and permanent flow rates. It will be costly to install a water meter that might underperform from the day of installation, <br><br />
(b) The installation has to strictly follow the manufacturer’s instructions,<br> <br />
(c) Unless the instructions allow for downpipes or an installation at an angle, most water meters require a horizontal installation. A water meter mounting position different to the instructions given by the manufacturer increases the friction of moving parts,<br><br />
(d) Install the meter at pipe level. The location of the meter should be such that it is not possible for air pockets to develop in the meter, for instance the meter should not be located at high points in the pipeline or operated under half full pipe conditions. The installation on top of a standpipe could lead to the meters reading air flow,<br><br />
(e) Fix the meter between two straight un-obstructed pipes: the upstream pipe’s length should equal to 10 times the pipe diameter and the downstream pipe’s length should be equal 5 times the pipe diameter,<br><br />
(f) The pipe diameter should not be reduced directly in front and behind the prepaid water meter,<br />
(g) All regulations of the flow (e.g. operation of gate valve) should be realized after the meter.<br />
<br />
=== Operation and Maintenance of Ordinary Water Meters ===<br />
<br />
Regular maintenance of water meters include cleaning of dirt box or strainer time to time, replacement of gaskets upon its wear and tear, cleaning of chamber where meter is installed and preventing water seepage in it, verifying whether it is indicating correct reading cleaning of spare parts when disassembled for any repairs or verification with detergents solution in warm water. Normally, general maintenance and repairs recommendations are given by the manufacturer.<br />
<br />
==== Functional Principles of Water Meters ====<br />
<br />
Water meters are divided into two classes:<br> <br />
* Volumetric water meters, when the volume is mechanically measured through a known volume of a measuring chamber, and<br><br />
* Inferential water meters, when the meter determines the velocity from variables such as pressure differences across a devices like and orifice plate, transit time of sound waves, changes in magnetic field.<br />
<br />
In general, domestic meters should be taken out of service every 5 to 7 years and completely overhauled. The systematic inspection and replacement of consumption meters is an important aspect of routine maintenance. Records should be kept on the condition of meters to guide future procurement and enable the Utility to take measures against water loss. Representative pothole checking of service connections within 5 years of service (avoid leaks due to deterioration) should also be done. Normally, general maintenance and repairs recommendations are given by the manufacturer. Table 16.1 illustrates the troubleshooting of water meters.<br />
<br />
'''Table 16. 1: Typical Troubleshooting of Water Meters'''<br><br />
[[File:16.png|700px|center]]<br />
<br />
==== Inspection of Water Meters ====<br />
(a) Clean all water meter parts thoroughly;<br><br />
(b) Make sure the gear train runs freely;<br><br />
(c) Check the action of the disc in the chamber;<br><br />
(d) Remember that friction is just as detrimental to correct registration (reading) as slippage;<br><br />
(e) Store meters away from heat;<br><br />
(f) Use a calibrated meter as a standard of comparison for tolerances and clearances;<br><br />
(g) After every repair, retest the meter for accuracy;<br><br />
(h) If necessary, call the manufacturer for advice<br />
<br />
==== Types of Water Meter Testing ====<br />
<br />
(a) ''Meter Shop Test'' – pull out meter and send it to testing laboratories/shops for testing /recalibration (equipment and service available usually at large utilities).<br><br />
(b) ''Volumetric Method (no dismantling)'' – using a container with known volume, a variance of +/- 4% should be pulled out for recalibration)<br><br />
(c) ''Using a Calibrated Test Meter'' – the meter should be put in series with a calibrated meter. In principle, readings should be the same. Record the difference; +/- 4% off should be re-calibrated.<br />
<br />
==== Water Meter Testing (If a Test Bench is Available) ====<br />
(a) Install/fix water meter on Test bench;<br><br />
(b) Open supply valve, close end valve and inspect for leaks;<br><br />
(c) Record the initial reading;<br><br />
(d) Open end valve, run the test and close end valve at desired volume.<br><br />
(e) Record the final reading;<br><br />
(f) Compute meter accuracy;<br><br />
(g) Identify Over/Under registering meters;<br><br />
(h) Calibrate by adjusting regulator or rheostat (+/-);<br><br />
(i) Re-test the water meter;<br><br />
(j) Seal the water meter cover and regulator plug.<br />
<br />
=== Metering Accuracy ===<br />
<br />
For accurate water flow measurements, various characteristics of the meter have to be known, before a suitable meter type with the right specifications can be chosen to fulfil this task. The characteristics are as follows:<br />
*Metering accuracy according to Water quality: Metering accuracy is significantly affected by suspended solids and depositions. Dirty water will cause under-registration e.g. with Positive Displacement Meters as well as with Velocity Meters. The Positive displacement meters may stop when a particle bigger than the spare space between the piston/disc and the chamber passes through the strainers of the meter. For Velocity meters, the depositions may cause over registration at medium-high flows and under registration at low flows. However, on the long term, deposits from suspended particle can grow so large that they can prevent the impeller from rotating, temporarily or permanently, causing a severe under registration of the meter<br><br />
*Metering accuracy according to Flow range/Rangeability (consumption pattern): Water meter measure accurately only flow rates that lie within its rangeability (Meter accuracy according to (TZS 782-5: 2015- ISO 4064-5: 2014). Flow rates beneath the specified minimal flow will be registered inaccurately or not at all. Operating a meter at either minimal or maximum flow rate, will reduce the life span of the meter and change its accuracy curve. While in the later case impact is seen sooner<br />
*Metering accuracy according to Oversized Meter– results in High non-revenue water. If the water meter is too large, the flow rates might be lower than the minimum flow rate and cause under-registration will be significant even from the first day of installation. Also oversized meters are more costly than rightly sized meter.<br />
*Metering accuracy according to Undersized Meter –results in accuracy and high pressure loss. If the meter is too small, the degradation of the accuracy will be accelerated. While the meter might be accurate at the beginning, in the short period of time, the pieces in contact with them, will break down leading to significant metering errors. Undersized water meters can cause excessive pressure loss.<br />
*Metering accuracy according to Metrological Class<br><br />
The Metrological class defines the accuracy of a water meter. There are old and new standard norms of the Metrological classes. Until 2003-2004, the metrological classes of meters were defined by the Standard (TZS 782-5: 2015- ISO 4064-5: 2014). This Standard, defines a meter by its Nominal Flow (Qn), called Qn, and Accuracy Class. There are 4 accuracy classes A, B, C, D. Each class sets a range of flow rates on which the meter must maintain its accuracy. A is the narrowest, D is the widest. Each meter operates accurately for its designed flow ranges, e.g. a Class A meter can be absolutely suitable if the consumptions are done according to a very narrow range of flow rates, which is often the case for irrigation.<br />
<br />
'''Requirement for accuracy:'''<br><br />
The Norm is demanding compliance of meters with the following accuracy limits for different flow rates:<br><br />
(a) +- 5% accuracy between Minimum and Transitional Flow<br><br />
(b) 2 % between Transitional and Maximum Flow<br />
<br />
'''Table 16.2: Definition of Flow Rates'''<br><br />
[[File:16i.png|700px|center]]<br />
Note: Qn is the nominal flow rate as half the maximum flow rate<br />
<br />
'''Pressure drops:''' The meters must not have a pressure drop higher than 1 bar at the maximum flow and 0.25 bar at the nominal flow.<br><br />
'''Please note:''' If the regular water flow rate is around or above the Maximum flow rate for which the meter has been designed, the measuring unit of the meter will be damaged progressively till it stops to work.<br />
<br />
=== Operation and Maintenance of Flow Meters ===<br />
<br />
Flow meters were described in Volume I. Regular monitoring of flow meters include periodic checking of range and zero setting, bearing wear out checking, deposits in flow meter, corrosion of attached pipes etc. Some of the general troubleshooting is listed in the Table.16.2.<br />
<br />
'''[[Table 16. 2: General Troubleshooting of Flow Meters]]'''<br />
[[File:16ii.png|700px|center]]<br />
(Source: Pradhikaran, 2012)<br />
<br />
=== Operation and Maintenance of Ordinary Bulk Water Meters ===<br />
<br />
Ordinary bulk flow meters are used at intakes, treatment works and in the distribution systems at reservoirs and bulk supply. They are installed for purposes of monitoring large flows of water for water system management and commercial billing purposes. They are normally equipped with helical vanes with pulse outputs for operation with various auxiliary equipment. Different body length sand material types are available to meet all requirements. <br />
<br />
Combination meters are manufactured for installations where wide variation in flow can be expected, such as in multi-story buildings, hospitals, schools, offices and other places where both low and high flows can occur due to several consumptions users. These wide flow ranges are measured by using a built-in changeover valve together with small residential meters and large bulk meter.<br />
<br />
Large commercial single jet meters are also available which have a low flow capability, which makes them ideal for revenue collection. Electromagnetic water meters are also available which are designed for measuring bulk flows in a wide range of applications including irrigation management of agricultural land. All bulk meters should be tested to ensure that they meet approved standards.<br />
<br />
=== Operation and Maintenance of Prepaid Water Meters ===<br />
<br />
Prepaid water systems are an effective and efficient way of collecting water tariffs and offer a high level of convenience to both the users and local water supply authorities. They save time and do not require unnecessary paperwork. Moreover, the systems minimize cash transactions and, therefore, contribute to the transparency of the tariff collection. In rural areas in Tanzania, the management of these prepaid systems has been strengthened with the formation of Community-Based Water Supply Organisations (CBWSOs). Prepaid meters have been operating successfully in the Districts of Kishapu, Karatu and Babati.<br />
<br />
Most prepaid water meters use a '''mechanical water meter''', coupled to an '''electronics module with a credit meter''' and a water control valve. When water flows, pulses are generated by a probe connected to the mechanical meter. The pulses are converted into credits that are subtracted from the total credits loaded by the customer. The valve closes when credit is exhausted or if there is tampering with the components. Prepaid systems use rotating piston and multijet water meters. The accuracy of these meters can be easily affected by grit, sand, and air; and frequent supply interruptions raise the risk of malfunction. This is a significant vulnerability for prepaid metering systems especially in urban areas, where there are ageing networks, discontinuous supply, and low pressure fluctuations. Electromagnetic and ultrasonic prepaid meters are technically better suited to networks with supply interruptions. These models are also highly accurate, resilient to pressure changes, air, and grit have no moving parts.<br />
<br />
'''(a) Prepaid Public Standpipes'''<br><br />
<br />
A customer using a standpipe, kiosk or water point loads credit bought from designated vendors using a programmed metal key, a smartcard, or a keypad. Dallas keys, or Buttons, are currently the most widely used, and consist of a computer chip mounted in a stainless steel container that looks like a large watch battery. Programmed keys and smartcards allow for a two-way exchange of data. A credit vendor loads credit onto the customer’s Dallas key using a point-of-sale device, and uploads consumption data from the customer’s prepaid meter for analysis later. This data can be used to track consumption trends and flag exceptions (unusually high or low consumption) or for follow-up. Numerical tokens and keypads are one-way only, and require separate data collection to track consumption.<br />
<br />
'''(b) Individual Domestic Connections''' <br><br />
<br />
The customers use their own prepaid meters, and load credit using a tag, smartcard, or keypad. The tag, card, or code can only be used on the specific meter for which it is programmed. Once the credit is loaded into the meter’s memory, customers do not have to use the key each time they draw water. A growing number of utilities acknowledge that regular monthly meter reading is essential to collect consumption data to calculate their water balance, reconcile sales, and monitor Non Revenue Water (NRW). Some utilities now insist that each prepaid device includes a conventional/post-paid mechanical meter, if necessary, in addition to an electronic meter. If the prepaid unit fails for any reason, the mechanical meter can still be read and supports conventional billing and payment.<br />
<br />
'''(c) Prepaid Bulk Meters for Commercial and Institutional Customers''' <br><br />
<br />
The Prepaid Bulk flow meters are used where wide variation in flows can be expected, such as in multi-story business buildings, hospitals, schools, offices and other places where both low and high flows can occur due to several consumptions users. These wide flow ranges are measured by using a built-in changeover valve together with small residential meters and large bulk meter. All bulk flow prepaid meters should be tested to ensure that they meet approved standards. A representative of the customer loads credit using a tag, smartcard, or keypad. The meter needs to be designed for far higher volumes than domestic meters and far greater accuracy, given the volumes. The large volumes of water sold to commercial and institutional customers comprise a significant source of income for water supply service providers in most urban towns.<br />
<br />
[[File:Table16.1_ewater_point.JPG|660px|link=Chapter_Sixteen:_Water_Meters,_Instrumentation_Telemetry_and_Scada]] <br><br />
'''Figure 16. 1 (a) & (b): E-Water Point in Sangara Village, Babati. A token used by E-Water Users to Get Water'''<br />
<br />
=== Testing and Calibration of Water Meters ===<br />
<br />
The testing & calibration of a water meter is essential before putting it into use as it is a statutory requirement and may be done periodically in order to ascertain its performance. It is likely that its accuracy of measurement may deteriorate beyond acceptable limits in the course of its use.<br />
<br />
A meter suspected to be malfunctioning is also tested for its accuracy of measurement. The testing is done as per TZS 782-2: ISO 4064-2:2014. A faulty meter if found to be repairable, is repaired and tested and calibrated for its accuracy before installation .The metering accuracy testing is carried out at Q<sub>min</sub>, Q<sub>t</sub> & Q<sub>max</sub>, separately where:<br><br />
(a) Q<sub>min</sub>: Lowest flow rate at which the meter is required to give indication within the maximum permissible error tolerance. It is determined in terms of numerical value of meter designation in case of ISO 4064.<br><br />
(b) Q<sub>t</sub>: The flow rate at which the maximum permissible error of the water meter changes in value.<br />
(c) Q<sub>n</sub>: Half the maximum flow rate Qmax.<br><br />
(d) Q<sub>max</sub>: The higher flow rate at which the meter is required to operate in a satisfactory manner for short periods of time without deterioration.<br><br />
(e) The accuracy of water meters is divided into two zones i.e.<br><br />
<br />
(i) Lower measurable limit in which ±5% accuracy from minimum flow to transitional flow (exclusive), and<br><br />
(ii) Upper measurable limit in which ±2% accuracy from transitional flow (inclusive) to maximum flow.<br />
<br />
The procedure for conducting the above test is as follows:<br><br />
Water meter is fixed on a test bench horizontally or vertically or in any other position for which it is designed and with the direction of flow as indicated by arrow on its body. By adjusting the position of regulating valve on the upstream side, the rate of flow is adjusted. At the desired rate of flow, the difference in pressure gauge readings fitted on upstream and downstream side of the water meter is noted. The flow is now stopped with regulating valve and measuring chamber is emptied and zero water levels on manometer attached to measuring chamber is correctly adjusted. Initial reading of the water meter from its recording dial is noted. Now the flow at the set rate is passed through the water meter and the discharge is collected in the measuring chamber. After passing the desired quantity of water through the meter, the flow is once again stopped. The discharge as recorded by measuring chamber is noted. The final reading of the water meter is noted. The difference between the initial and final readings of the water meter gives the discharge figure recorded by water meter. Now the discharge recorded by measuring tank is treated as ideal. The discharge recorded by water meter is compared with this ideal discharge. If the quantity recorded by water meter is more than the ideal, the meter is called running fast or vice versa.<br />
<br />
The difference in the quantity recorded by the meter from the ideal quantity is considered as the error. This error is expressed in percentage. If the limits of error for the meter exceed that specified in the TZS/ISO standards concerned the meter is readjusted by the regulator if it is available in the meter. A change in position of the regulating screw will displace the error curve (calibration curve) in parallel to former the position. With the closing of the regulating orifice the curve will shift upward while opening the same will lower the curve. If the curve does not get into acceptable limit the meter is not used. Some of the organizations are accepting accuracy limit for repaired water meter double the value of new water meters at respective zones i.e. for upper zone accuracy is ±4% & for lower zone accuracy is ±10%. In Tanzania, the Agency for Weights and Measures as per relevant Law.<br />
<br />
=== Repairs, Maintenance and Troubleshooting of Water Meters ===<br />
<br />
The water meters are mechanical devices, which normally deteriorate in performance over time. Water meters in good working conditions are the basis to determine the water network efficiency and for accurate billing. The fact that a meter does not show outward signs of any damage and has a register that appears to be turning, does not mean that the meter is performing in a satisfactory manner. It is necessary to ascertain the following preventive cares for water meters after proper installation:<br><br />
<br />
'''(a) Preventive maintenance:'''<br><br />
(i) Proper handling, storage and transportation of water meters,<br><br />
(ii) To clean the dirt box or strainer wherever installed,<br><br />
(iii) To replace the gaskets, if any;<br><br />
(iv) To clean the chamber in which the meter is installed and keep free from flooding, & seepage,<br><br />
(v) To remove the meter for further internal repair/replacement if it does not show correct reading pattern.<br />
<br />
'''(b) Breakdown maintenance:'''<br><br />
Replacement of broken glass, lid and fallen wiper wherever provided: These are the only basic breakdowns observed during periodical inspection. If a meter found not working, then it shall be removed immediately and sent to the meter service workshop. In meter workshops normally following steps are performed to carry out the repairs:<br><br />
(i) Disassembling of water meters including strainer, measuring unit, regulator, registering device,<br><br />
(ii) Clean all disassembled spare parts in detergent solution in warm water,<br><br />
(iii) Inspect the cleaned parts and replace worn parts and gaskets, if any,<br><br />
(iv) Inspect the meter body spur threads and cover threads,<br><br />
(v) Inspect the sealing surface on meter body and paint the meter body, if necessary,<br><br />
(vi) Inspect the vane wheel shaft pinion, bearing & pivot,<br><br />
(vii) Inspect the vane wheel chamber,<br><br />
(viii) Reassemble the water meter properly after reconditioning,<br><br />
(ix) Calibrate & test the repaired water meter for leakage & accuracy as per ISO:4064-2:2014,TZS 782-2:2018,<br><br />
(x) Make entry in the life register of that water meter for keeping history record.<br />
<br />
=== Prevention of Tampering of Water Meters ===<br />
<br />
In order to prevent tampering, following precautions should be taken:<br><br />
(a) The water meters, shall be installed properly in the chamber with lock and key or in the cast iron covers with lock and key in order to avoid tampering,<br><br />
(b) The water meters must be sealed properly,<br><br />
(c) The water meters shall not allow reversible flow; it should register flow in forward directions only,<br><br />
(d) The water meter dials should be easily readable without confusions,<br><br />
(e) The lid, glass of water meters must be made up of tough materials as per ISO: 4064-4:2014, TZS 782-4:2018 and shall be replaced timely,<br><br />
(f) The wiper or dial as far as possible is avoided,<br><br />
(g) In case of magnetically coupled meters, the proper material to shield magnets must be provided in order to avoid the tampering of such meter by outside magnets in the vicinity of the meter,<br><br />
(h) Periodic inspection/checking at site is essential to ensure the proper working of the meter,<br><br />
(i) Special sealing arrangements may be necessary and provided for bulk meters where by unauthorized removal of the meter from the connection can be detected.<br><br />
<br />
In addition to the above, to tackle the problems of tampering, suitable penalty provisions/clauses shall be there in the rules or the water supply agreement with the consumer. This will also discourage the consumer tendencies of neglecting water meter safety.<br />
<br />
=== Automatic Water Metering Systems ===<br />
<br />
Water meter is a cash register of a water supply agency/authority/utility. Consumption based water rates require periodic reading of meters except in remote or automated meter reading of meters. Except in remote or automated meter reading these readings are usually done by meter readers visiting consumers premises one by one and noting down the indicator reading by the meter. These readings are recorded manually in books or on cards and later keyed in manually to a customer accounting or billing system. In some cases, meter readers use Hand held Data Entry Terminals to record meter readings. Data from these devices are transferred electronically to a billing system. In other cases, key entry has been replaced by mark-sense card readers or optical scanners.<br />
<br />
In case the environment of meter reading is not favourable to the meter reader as the water meters are at times installed in underground chambers; these chambers are filled in many cases with water, reptiles or insects. In some consumers connect their electrical earth terminal to water supply utility/authority/agency pipe which endangers the safety of the meter reader or premises are not accessible to the meter reader. The solution to the above difficulties is to install automatic system to read meters and process the results by computer.<br />
<br />
The data can be captured by the meter readers from the meter in one of the following ways:<br><br />
(a) Manual entry into meter books,<br><br />
(b) Manual entry into portable hand held entry terminals or recorders,<br><br />
(c) Direct electronic entry from meter registers either into portable data terminals or display units from which readings are transcribed in the field,<br><br />
(d) Telemetry link through radio, telephone.<br />
<br />
== Instrumentation ==<br />
<br />
Some instrumentation is expected to be applied in the following areas:<br />
<br />
=== Level Measurement ===<br />
<br />
Instrumentation facilitates coordination of various water parameters, which are essential for optimization of water supply & treatment plant. One of the important parameters amongst them is water level measurement, which is carried out at various locations viz. water reservoir, inlet chamber, open channel, alum feeding tank, lime tank, filter beds, air vessel, sump well, etc. This measurement is accomplished in water works by two following ways:<br><br />
(a) Direct Method,<br><br />
(b) Inferential Method.<br />
<br />
=== Pressure Measurement ===<br />
<br />
In water supply networks, pressure parameter plays a very important role in order to get sufficient water to the consumers. Similarly in flow measurement by differential pressure type flow meter, differential pressure measurement across the primary element is the main physical parameter to inter-link with the flowing fluid. This pressure or differential pressure measurement is accomplished with the help of the following methods in water works:<br><br />
(a) Manometers,<br><br />
(b) Elastic Pressure Transducers,<br><br />
(c) Electrical Pressure Transducer.<br />
<br />
=== Capacitors ===<br />
<br />
Capacitors are needed to be provided invariably in all the pumping stations for maintaining required power factor thereby saving of energy. Pre-requisites for satisfactory functioning of capacitors ensure the following points:<br />
(a) A capacitor should be firmly fixed to a base,<br />
(b) Cable lugs of appropriate size should be used,<br />
(c) Two spanners should be used to tighten or loosen capacitor terminals. The lower nut should be held by one spanner and the upper nut should be held by the spanner to avoid damage to or breakage of terminal bushings and leakage of oil,<br />
(d) To avoid damage to the bushing, a cable gland should always be used and it should be firmly fixed to the cable-entry hole,<br />
(e) There should be a clearance of at least 75 mm on all sides for every capacitor unit to enable cooler running and maximum thermal stability. Ensure good ventilation and avoid proximity to any heat source,<br />
(f) While making a bank, the bus bar connecting the capacitors should never be mounted directly on the capacitor terminals. It should be indirectly connected through flexible leads so that the capacitor bushings do not get unduly stressed,<br />
(g) Ensure that the cables, fuses and switchgear are of adequate ratings.<br />
<br />
====Operation and Maintenance of Capacitors====<br />
<br />
(a) The supply voltage at the capacitor bus should always be near about the rated voltage. The fluctuations should not exceed ±10% of the rated voltage of the capacitor,<br><br />
(b) Frequent switching of the capacitor should be avoided. There should always be an interval of about 60 seconds between any two switching operations,<br><br />
(c) The discharge resistance efficiency should be assessed periodically by sensing, if shorting is required to discharge the capacitor even after one minute of switching off. If the discharge resistance fails to bring down the voltage to 50 V in one minute, it needs to be replaced,<br><br />
(d) Leakage or breakage should be rectified immediately. Care should be taken that no appreciable quantity of imp- regnant has leaked out,<br><br />
(e) Before physically handling the capacitor, the capacitor terminals shall be shorted one minute after disconnection from the supply to ensure total discharging of the capacitor,<br><br />
(f) Replace capacitor if bulging is observed.<br />
<br />
=== Water Hammer Control Devices ===<br />
<br />
Maintenance requirements of water hammer devices depend on type of water hammer control device, nature of its functioning, water quality, etc. Type of water hammer control devices used in water pumping installations is as follows:<br />
* Surge tank and/One-way surge tank,<br />
* Air vessels (air chamber),<br />
* Zero velocity valve and air cushion valve,<br />
* Surge anticipation valve (surge suppressor),<br />
* Pressure relief valve.<br />
<br />
General guidelines for maintenance of different types of water hammer control devices as follows:<br><br />
<br />
'''(a) Surge Tank and One-Way Surge Tank'''<br><br />
Quarterly:<br><br />
(i) Water level gauge or sight tube provided shall be inspected, any jam rectified,<br><br />
(ii) All cocks and sight tube flushed and cleaned.<br><br />
<br />
'''Yearly:'''<br><br />
The tank shall be drained and cleaned once in a year or earlier if frequency of ingress of foreign matter is high.<br />
<br />
'''(b) Valve maintenance:'''<br><br />
(i) Maintenance of butterfly valve, sluice valve and reflux valve shall be attended,<br><br />
(ii) Painting: Painting of surge tanks shall be carried out once in 2 years.<br><br />
<br />
'''Air-Vessel'''<br><br />
'''Daily:'''<br><br />
(i) Check air-water interface level in sight glass tube,<br><br />
(ii) The air water level should be within range marked by upper and lower levels and shall be preferably at middle,<br><br />
(iii) Check pressure in air receiver at interval of every 2 hours.<br />
<br />
'''Quarterly:'''<br><br />
(i) Sight glass tube and cock shall be flushed,<br><br />
(ii) All wiring connections shall be checked and properly reconnected,<br><br />
(iii) Contacts of level control system and pressure switches in air supply system shall be cleaned.<br />
<br />
'''Yearly:'''<br><br />
(i) The air vessel and air receiver shall be drained, cleaned and dried,<br><br />
(ii) Internal surface shall be examined for any corrosion etc. and any such spot cleaned by rough polish paper and spot-painted,<br><br />
(iii) Probe heads of level control system shall be thoroughly checked and cleaned accessories: Maintenance of panel, valves and air compressor etc. shall be carried out as specified for respective appurtenances.<br />
<br />
'''Zero-Velocity Valves and Air Cushion Valve'''<br><br />
Foreign matters entangled in valve shall be removed by opening all hand holes and internal components of the valves including ports, disk, stem, springs, passages, seat faces etc. should be thoroughly cleaned and checked once in 6 months for raw water and once in a year for clear water application.<br />
<br />
== Telemetry and SCADA Systems ==<br />
<br />
=== Manual Monitoring ===<br />
<br />
Normally the managers of O&M of water supply scheme monitor levels in service reservoirs, pressures and flows in a distribution system, and on operation of pumps such as hours of pumping and failure of pumps and monitor water quality by measuring residual chlorine. The line department/unit usually uses the telephone line or wireless system to gather the data, uses his discretion gained with experience and takes decisions to ensure that the system is operating with required efficiency. Manual collection of data and analysis may not be helpful in large undertakings if water supply utilities have to aim at enhanced customer service by improving water quality and service level with reduced costs. This is possible if the management acquires operational data at a very high cost.<br />
<br />
=== Telemetry ===<br />
<br />
The inspection, monitoring and control of O&M of a water supply utility/authority/agency can be automated partially through telemetry. Telemetry enables regular monitoring of the above data on real time basis and the data is provided to anyone in the organization who can review the data and take decision. In Telemetry system, probes/sensors are used and sense, generate signals for the level, pressure and flow in a given unit and transmits the signals by radio/by Telephone. Normally radio link is used and telephone line with a modem is used as spare communication. Microwave satellite or fiber-optic transmission systems are also used for data transmission. The water pumping stations may communicate via a cable buried with the pipe. However there may be locations where the main power may not be available and hence solar panels with a battery charger are used to power the remote terminal unit (RTU) and the radio. In urban areas RTU s can communicate on cell phones and or packed radio networks. For remote locations satellite technology is also available.<br />
<br />
'''(a) Data for Collection by Telemetry'''<br><br />
The data includes levels in service reservoirs, pressures and flows in a distribution system, flows/quantity of delivered into a SR and data on operation of pumps such as voltage, amperes, energy consumed, operating times and down times of pumps and chlorine residuals. In a telemetry system up-to the minute real time information is gathered from remote terminal unit located at the water treatment plant, reservoir, flow meter, pumping station etc. and transmitted to a central control station where the information is updated, displayed and stored manually or automatically.<br />
<br />
'''(b) Processing Data from Telemetry'''<br><br />
The meter readings from reservoirs are useful information for managing the distribution system and helps in preventing overflow from reservoirs. However, the effectiveness of telemetry in pumping operations is dependent on reliability of instrumentation for measuring flows, pressures, KWh meters. Standard practice is to calculate pump efficiency and water audit calculations on a monthly basis. Telemetry can also be used to supervise water hammer protection system wherein the pump failures are linked to initiate measures to prevent occurrence of water hammer.<br />
<br />
'''(c) SCADA Systems (Supervisory Control and Data Acquisition)'''<br><br />
Supervisory Control and Data Acquisition (SCADA) systems provide control functionality and alarms at water supply scheme sites which in many cases are very remote. These systems were often used to solve single problems such as reducing power cost, or improving control of a particularly complex operation. The installation of SCADA has subsequently been seen as a means to satisfy a variety of increasing pressures such as consumer demands, regulatory requirements, and to also satisfy the need to reduce operational costs. The deployment of SCADA systems has been extended to cover large water supply schemes and has been found very effective.<br />
<br />
An important challenge to the commercial success of the organization is to harness the data collection power of the SCADA systems to provide a wealth of operational information to all levels of the organization. Past systems that have been installed in some of the water treatment plants have failed to meet expectations regarding data availability. This has primarily been attributed to difficulties associated with merging traditional engineering and new IT methodology, and a lack of system openness in data interconnectivity and communications.<br />
<br />
'''(d) Remote Terminal Units (RTU)'''<br><br />
A Remote Terminal Unit (RTU) is a microprocessor-controlled electronic device that interfaces objects in the physical world to a SCADA by transmitting telemetry data to the system and/or altering the state of connected objects based on control messages received from the system. Modern RTUs are usually capable of executing simple programmes autonomously without involving the host computers of SCADA system to simplify deployment, and to provide redundancy for safety reasons. An RTU in a modern water management system will typically have code to modify its behaviour when physical override switches on the RTU are toggled during maintenance by maintenance personnel. This is done for safety reasons; a miscommunication between the system operators and the maintenance personnel could cause system operators to mistakenly enable power to a water pump when it is being replaced, for example.<br />
<br />
<br />
Previous Page: [[Chapter_Fifteen:_Operation_and_Maintenance_of_Sanitation_Projects]] << >> Next Page: [[Chapter_Seventeen:_Water_Audit_and_Leakage_Control]]<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Part_EPart E2022-07-16T15:35:02Z<p>Juma: </p>
<hr />
<div>PART E: WATER AUDIT, REVENUE AND COMMUNITY PARTICIPATION MANAGEMENT<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Fifteen: Operation and Maintenance of Sanitation Projects]] << >> Next Page: [[Chapter Sixteen: Water Meters, Instrumentation Telemetry and Scada]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Fifteen:_Operation_and_Maintenance_of_Sanitation_ProjectsChapter Fifteen: Operation and Maintenance of Sanitation Projects2022-07-16T15:34:35Z<p>Juma: /* Organizing and Planning Operation and Maintenance */</p>
<hr />
<div><br />
=Chapter Fifteen Operation and Maintenance of Sanitation Projects=<br />
==Operation and Maintenance Requirements for Sanitation System==<br />
<div style="text-align:justify"><br />
Operation and maintenance (O&M) activities, encompass not only technical issues, but also managerial, social, financial and institutional issues, must be directed towards the elimination or reduction of the major constraints which prevent the achievement of sustainability (Brikke, 2000). Operation and maintenance is a crucial element of sustainability and a frequent cause of failure of sanitation service facilities in the past. Many failures are not caused by technical reasons only, they may also result from poor planning, inadequate cost recovery, or the outreach inadequacies of centralised agencies (DfID, 1998).<br />
<br />
Operation and maintenance has been neglected in the past, it has been discussed and introduced after a project completion. This neglect or delay in applying proper operation and maintenance has adversely affected the credibility of the investments made, the functioning of the services, the well-being of rural populations, and the development of further projects. However, the importance of O&M has gained considerable visibility over the past few years, and it appears that policy-makers and project designers are now more conscious of the direct links between improved O&M practices and the sustainability of sanitation services. There is also greater recognition of the need to approach these projects in a comprehensive way, emphasizing not only the design and construction but also post-construction activities (Brikke, 2000).<br />
<br />
===Design for Operation and Maintenance===<br />
The ease of operation and maintenance of a facility is central to its sustainability and must be given careful consideration in design. Some operation and maintenance issues are location-specific, but urban and rural projects differ fundamentally in the complexity of the technologies involved. In rural areas, the concept of Village Level Operation and Maintenance Management (VLOM) is a philosophy which has been gaining favour over the years. The VLOM approach restricts technology choices to those that can be operated and maintained within the community for which the intervention is intended. In urban situations, where supply systems will generally be more complex, the design and technology chosen will shape the long-term operation and maintenance requirements. When designing a sewerage system, the engineer must, for instance, take into account operation and maintenance factors such as the availability of chemicals for treatment, spare parts, and equipment, the reliability of power supplies, and the availability of local skills and capacity to undertake O&M.<br />
<br />
The standardization of equipment, parts, designs, construction methods, etc., has many benefits. It makes design simpler as choices are made from a limited range of options. In the short term, this may marginally increase construction costs as the standard designs may not be perfectly suited to the situation. But it requires lower skill levels in the design process, and repetitive construction of the same item improves quality. Operation and maintenance benefits too: Limiting the range of spare parts increases the quantity of each item that is required (i.e. more of a few items rather than less of many). This encourages local manufacture because the limited range reduces start-up costs and the increased quantity improves profitability. Standardization also reduces the number of skills required to install and maintain the piece of equipment, thus increasing the probability of local craftsmen being able to carry out the work.<br />
<br />
==Community Management for Operation and Maintenance==<br />
In order to ensure the sustainability of the sanitation and improved sanitation solution, it is necessary to have a community ownership and management approach, making the end-users directly responsible for the operation and maintenance of the installed facilities. Successful operation and maintenance requires following an “owner’s manual” prepared by the contractor and engineer at the onset of the planning process. This should spell out a schedule and procedures for maintenance and should also include methods to carry out tasks, such as book-keeping, paying employees, collecting bills (utility management), inspection, replacement of parts, etc., giving an integral framework for operation and maintenance (NETSSAF, 2008).<br />
<br />
==Capacity Building to Ensure Proper Operation and Maintenance==<br />
Households and members of the community need to be informed about the system that has been put in place for a proper operation. When new user-interfaces or management approaches have been introduced, such as Urine Diversion Dehydration Toilets (UDDT) or a new system for composting of kitchen waste, which heavily relies on the correct operation from the user’s side, the end-users have to be properly trained to ensure that they will operate the systems correctly.<br />
<br />
At district level, communities and their organizations (Community-Based Water Supply Organizations - CBWSOs) that will undertake O&M and/or management of local infrastructure need training on technical matters, accounting and simple financial management, basic contract procedures, and monitoring and reporting. NGOs that will become involved in the programme need similar training, but at a more advanced level, as they are probably going to have to train the participating communities (EAWAG 2005).<br />
<br />
Local operators and caretakers need to be trained for the proper operation of the new infrastructure. In this case, hands-on training is desired in order to ensure the full understanding and the awareness of the implications of the new system. Private operators or local engineering companies that will take care of the maintenance of the sanitation systems should be also trained in the type of maintenance activities that have to be carried out periodically.<br />
==Organizing and Planning Operation and Maintenance==<br />
Organizing for O&M does not represent a huge task, but it does require a certain level of planning, commitment and monitoring. The aspects to be organized are:<br />
* What: the activity which is to be carried out<br><br />
* When: the frequency of this activity<br><br />
* Who: the human resources required for the task<br><br />
* With what: what are the materials, spare parts, tools and equipment needed<br><br />
<br />
Table 15.1 gives an idea of the type of tools which have to be developed to support the operation and maintenance of the envisaged new sanitation infrastructure. The example relates to the O&M of a septic tank (adapted from Castro, 2009):<br />
<br />
Table 15. 1: The Operation and Maintenance Requirements of a Septic Tank<br />
<br />
[[File:Capture.png|700px|center]]<br><br />
(Source: Castro, 2009)<br />
<br />
Applicability<br />
Operation and maintenance is required to ensure the sustainability of any project in which a new infrastructure has been put into place.<br />
<br />
==Operation and Maintenance requirements for Sanitation Units==<br />
Different sanitation units have different operation and maintenance requirements. This section presents O and M requirements for different sanitation units.<br />
===Septic Tank===<br />
'''Operation'''<br><br />
The daily discharges made from a property into a septic tank or treatment plant will affect the efficiency of the system. Discharges of disinfectants and strong chemicals will kill bacteria in the tank and hence prevent the decomposition of the solids. It is therefore very important to consider the effects of cleansing products on the bacteria. A simple list is given below to highlight measures that will improve the efficiency of a septic tank: <br><br />
(a) Discharges of rainwater to the septic tank are not recommended. The turbulence caused by the high flows will disturb solids in the vessel and allow them to be carried out into the ground (causing the soak away to block). Rainwater also causes considerable dilution of the bacterial matter thereby reducing the efficiency of the tank. If possible rainwater should be drained to a surface water drain, stream or separate soak away,<br> <br />
(b) Prevent the discharge of non-degradable matter into the tank, such as nappies, condoms, sanitary towels, etc. that will not decompose. Avoid all discharges of oils and cooking fats, which will congeal inside the tank and will not be digested by the bacteria. Oils entering the tank from washing up can largely be ignored,<br><br />
(c) Volatile liquids such as petrol, acetone, methylated spirits, paraffin, etc. must never be discharged into the drainage system mainly due to their high flammability,<br> <br />
(d) Chemical discharges including cleaning agents have considerable effects on the bacterial treatment of sewage dependent upon their concentration, quantity and frequency of use. With mild detergents such as washing powders, etc. a minimum dilution factor of 50 parts water to 1 part detergent is recommended. Whilst good personal hygiene should always be maintained, disinfectants, acids, bleaches, chlorine and strong detergents must only be used where absolutely necessary.<br><br />
<br />
'''Maintenance'''<br><br />
Periodically the sludge and scum will build-up to such an extent that it needs removing. The frequency of these sludge removal visits is dependent on the use, size and type of the septic tank. As a general guide older brick or concrete structures (often fitted with rectangular metal covers) will require emptying approximately once every 2 years, whilst fiberglass tanks (often fitted with diamond shaped access covers) or pre-cast concrete cylindrical tanks will need emptying at least every 12 months. A traditional septic tank contains no mechanical parts and should not require any other regular maintenance unless problems occur. It is a good idea when emptying brick / concrete tanks to leave the top layer of sludge within the vessel and to remove the solids from the base of the tank. This allows the bacteria to quickly re-establish when the tank fills again. Modern packaged sewage treatment plants are likely to require more frequent emptying (at least once every 6 months). These systems will also require the servicing of any mechanical parts within the vessel. It is recommended that the manufacturers’ advice be sought on the maintenance of these plants. Most large drainage contractors offer a septic tank emptying service and there is a wide range of companies advertising in the classified directories that may also be able to carry out appropriate servicing on packaged sewage treatment plants. In Tanzania, the emptying services are offered by both the municipal or town councils or private providers.<br />
<br />
===Sewers===<br />
Consistent and thorough maintenance of the collection system will enable the system to serve its stated life. Preventive maintenance is talked about, but seldom practiced by some agencies. Decades of neglect, or grossly inadequate maintenance of some systems, are two reasons why wastewater collection systems now require billions of dollars worth of rehabilitation and upgrading over the next 20 years.<br />
<br />
'''Cause of sewer dysfunctions:'''<br><br />
(a) Collection systems and service connections were not installed as designed. Problems are caused by faulty construction, poor inspection and low-bid shortcuts,<br><br />
(b) The pipe joints were made rigid. Earth movement, vibration from traffic, settling of structures and construction disturbance (all occur from time to time) require a flexible pipe material or joint that can maintain tightness. Joints had opened, cracked and/or sheared thus allowing debris and infiltration into the sewer,<br><br />
(c) Corrosion of sewer pipes and manholes from either the trench bedding and backfill or the wastewater being transported by the collection system was a factor neglected during design. A major cause of corrosion in wastewater collection systems and treatment plants is hydrogen sulphide gas,<br><br />
(d) Potential damage to pipe joints by plant roots was not known or was neglected during design. Although root intrusion into sewers is age-old, it was assumed that if the joint was watertight, it would be root tight. People did not realize that roots would be attracted by moisture and nutrient vapour unless the joints were vapour tight (which means airtight). Roots can enter a pipe joint or walls microscopically (through extremely small holes or cracks); thus, open or leaking joints are not necessary for root intrusion in collection systems,<br><br />
(e) Collection system environments are ideal for root growth. In this environment, roots enter, expand and open joints and cracks. Root growth is a principal cause of pipe damage that allows infiltration and exfiltration. This creates a major concern for health and pollution control authorities because of wastewater treatment plant overload and groundwater pollution,<br><br />
(f) The out of sight, out of mind nature of wastewater collection system. Local taxpayers have invested more money in underground sewers why has this great taxpayer investment been so grossly neglected? Because it is out of sight, and so, out of mind,<br><br />
(g) Poor records regarding complaints from the public or the date and location of stoppages that had to be cleared can result in an ineffective maintenance programme. Good records, regular analysis of the records, and use of this information can produce a cost-effective preventive maintenance programme.<br><br />
<br />
Operation and maintenance of wastewater collection systems in an emergency basis has been the usual procedure and policy in many communities and districts. Planned operation and preventive maintenance of the collection system has been delayed or omitted, in spite of desires by collection system operators. Municipal officials tend to neglect collection systems as long as complaints are not excessive. To please constituents, officials often demand street and sidewalk repairs to be done by collection system crews, but seldom have they ever demanded preventive work on the collection systems.<br />
<br />
Inspection and testing are the techniques used to gather information to develop operation and maintenance programmes to ensure that new and existing wastewater collection systems serve their intended purposes on a continuing basis. Inspection and testing are necessary to do the following:<br><br />
(a) Identify existing or potential problem areas in the collection system,<br><br />
(b) Evaluate the seriousness of the detected problems,<br><br />
(c) Locate the position of problems, and<br><br />
(d) Provide clear, concise and meaningful reports regarding the observed problems.<br><br />
<br />
'''Sewer Leakage Control''' <br><br />
Leaky sewers have to be considered as potential sources for groundwater contamination in urban areas. Two major purposes of inspecting and testing are to prevent leaks from developing in the wastewater collection system and to identify existing leaks so they can be corrected. The existence of leaks in a wastewater collection system is a serious and often expensive problem. When a sewer is located below under a water table, infiltration can take place and occupy valuable capacity in the sewer and the downstream treatment plant. Sewers located above a water table can ex-filtrate, allowing raw wastewater to pollute the soil and groundwater.<br />
<br />
Guidance for manhole inspections and sewer inspections are presented herein. The information provided if employed is a good starting point for an inspection. Manhole inspections should yield a report with the following information at the minimum:<br><br />
(a) Exact location of the manhole;<br><br />
(b) Diameter of the clear opening of the manhole;<br><br />
(c) Condition of the cover and frame, including defects that would allow inflow to enter the system;<br><br />
(d) Whether cover is subject to ponding or surface runoff;<br><br />
(e) The potential drainage area tributary to the defects;<br><br />
(f) Type of material and condition of the chimney corbel cone and walls;<br><br />
(g) Condition of steps and chimney and frame-chimney joint;<br><br />
(h) Configuration of the incoming and outgoing lines (including drops); and<br><br />
(i) Signs of frame-chimney leakage or damage to the frame’s seal.<br><br />
<br />
Additionally, the following data can be obtained by entering the manhole and using equipment such as CCTV, portable lamps, mirrors, rulers, and probe rods:<br><br />
(a) Type of material and condition of apron and trough;<br><br />
(b) Any observed infiltration sources and the rate of infiltration;<br><br />
(c) Indications of height of surcharge;<br><br />
(d) Size and type of all incoming and outgoing lines; and<br><br />
(e) Depth of flow indications of deposition and the characteristics of flow within all pipes.<br><br />
(f) The condition of the manhole shaft;<br><br />
(g) Any leakage in the channel;<br><br />
(h) Any leakage between the manhole wall and the channel;<br><br />
(i) Any damage or leakage where pipeline connects to the manhole; and<br><br />
(j) Any flow obstructions.<br><br />
<br />
Planning is required to define the inspections goals. Inspections are performed to:<br><br />
(a) Identify maintenance problems,<br><br />
(b) Determine general sewer conditions,<br><br />
(c) Identify extraneous flows.<br><br />
<br />
'''Methods for Controlling Sewer Leaks''' <br><br />
Methods for controlling leaks in the sewer collection system can be summarized as follows:<br />
<br />
(a) Chemical grouting: A soil sealing process which employs a two-part liquid chemical grout that solidifies after curing. The grout is remotely applied under pressure to leaking joints or laterals and small cracks in sewers and manholes to seal the voids within the soil surrounding the exterior of the pipe at the point of leakage,<br> <br />
(b) CIPP (cured-in-place) lining: An internal liner is formed by inserting a resin-impregnated felt tube through the manhole into the sewer. The liner is then expanded against the inner wall of the existing pipe and allowed to cure,<br><br />
(c) Fold and form liner: A folded thermoplastic pipe is pulled into place through a manhole and then rounded, using heat, steam and air pressure to conform to the internal diameter of the existing pipe,<br><br />
(d) Slip lining: An access pit is excavated adjacent to an existing sewer and a liner pipe of slightly smaller diameter is slid into the existing pipe to create a continuous, watertight liner between the two manholes,<br> <br />
(e) Pipe bursting: An access pit is excavated adjacent to an existing sewer and the pipe is broken outward by means of an expansion tool. A flexible liner pipe of equal or larger diameter is pulled behind the bursting device as a replacement sewer.<br><br />
<br />
It is important to take note that, with exception of the chemical grouting, the other methods are more expensive. <br />
'''<br />
Sewer Cleaning'''<br />
The purpose of sewer cleaning is to remove foreign material from the sewer and generally is undertaken to alleviate one of the following conditions:<br />
<br />
(a) Blockages (semisolid obstructions resulting in a virtual cessation of flow). These generally are dealt with on an emergency basis, although the underlying cause can be treated pre-emptively;<br><br />
(b) Hydraulic capacity. In some cases, sediment, roots, intrusions (connections or other foreign bodies), grease, encrustation and other foreign material restrict the capacity of a sewer, causing surcharge or flooding. Cleaning the sewer may alleviate these problems permanently, or at least temporarily;<br><br />
(c) Pollution caused by either the premature operation of combined wastewater overflows because of downstream restrictions to hydraulic capacity or pollution caused by the washing through and discharge of debris from overflows during storms;<br><br />
(d) Odour caused by the retention of solids in the system for long periods resulting in, among other things, wastewater turning septic and producing hydrogen sulphide;<br><br />
(e) Sewer inspections, where the sewer needs to be cleaned before inspection. This requirement most often occurs when using in-sewer CCTV inspection techniques;<br><br />
(f) Sewer rehabilitation where it is necessary to clean the sewers immediately before the sewer being rehabilitated.<br><br />
<br />
Common sewer cleaning methods include:<br><br />
(a) Jet rodding,<br> <br />
(b) Manual rodding,<br> <br />
(c) Winching or dragging,<br> <br />
(d) Cutting, and<br><br />
(e) Manual or mechanical digging.<br><br />
<br />
The method usually is determined in advance and is normally contingent on the pipe type and size and on the conditions expected in the pipe.<br />
<br />
'''Record Keeping'''<br><br />
Record keeping of sewer maintenance, inspections and repairs meets several needs of the sewer system. Records help simplify and improve work planning and scheduling, including integrating recurring and on-demand work. Measuring and tracking of workforce productivity and developing unit costs for various activities are a few of the record keeping benefits. Records of sewer maintenance, service line maintenance, and sewer main and service line repairs should be kept and maintained.<br />
<br />
===Grease Trap===<br />
Greasy waste that accumulates in the grease trap must be removed regularly. The frequency of cleaning will vary depending on the type of food served and how active one's residence or business is. Regular cleaning keeps a grease trap working properly and will prevent clogging in kitchen drains and pipes. The procedures for grease removal are:<br />
<br />
(a) Inspect the grease trap at least every three days and clean it promptly if the contents show the top 30% of the liquid depth is occupied by greasy waste;<br><br />
(b) Every grease trap is different and must be inspected regularly to determine if cleaning is required. If very little waste builds up in one week or if the surface layer is liquid oil only, the grease trap may not be functioning effectively;<br><br />
(c) Check for proper design as outlined in this DCOM Manual and modify or replace the trap if necessary. Small grease traps may be cleaned by hand by scooping the top waste layer into a watertight bag or container or applying hot water;<br><br />
(d) It is not necessary to empty the grease trap completely; remove only semi-solid layer of greasy waste on the top of the liquid surface;<br><br />
(e) Clean the trap at a time when wastewater will not be passing through it. Take care not to leave lumps of grease in the trap as this may lead to clogging;<br> <br />
(f) Handle the greasy waste carefully to avoid contamination of food preparation or storage areas. Warning signs and safety barriers should be erected around the floor and large grease traps during cleaning;<br> <br />
(g) Replace grease trap cover promptly and clean the surrounding area with a disinfectant;<br><br />
(h) The grease trap waste container should be tightly sealed and disposed of with other kitchen refuse. DO NOT dispose of the grease trap waste in the toilet, gulleys, surface channels or manholes;<br><br />
(i) Record maintenance activities in a log book. Clogging of the inlet or the pipes connecting the two chambers of the grease trap is not a common occurrence but if this happens, any obstruction can be pushed out from the open top of the pipe extending above the liquid surface. Kitchen wastewater also carries pieces of solid waste that are heavier than water. In a grease trap, these solids fall to the bottom and form a layer of settled material. It is necessary to remove this bottom layer of settled waste occasionally; otherwise the grease trap capacity will be reduced.<br> <br />
(j) Carefully remove and dispose of this bottom material in the same manner as for the top layer of greasy waste;<br><br />
(k) Cleaning a grease trap is not a very pleasant job and staff members responsible for this task should be encouraged to carry it out promptly as required and thoroughly.<br><br />
===Screening and Grit Removal===<br />
'''Screen'''<br><br />
Manually cleaned screens require frequent raking to prevent clogging. Cleaning frequency depends on the characteristics of the wastewater entering a plant. Some plants have incorporated screening devices, such as basket-type trash racks, that are manually hoisted and cleaned. Mechanically cleaned screens usually require less labour for operation than manually cleaned screens because screenings are raked with a mechanical device rather than by facility personnel. However, the rake teeth on mechanically cleaned screens must be routinely inspected because of their susceptibility to breakage and bending. Drive mechanisms must also be frequently inspected to prevent fouling due to grit and rags. Grit removed from the screens must be disposed of regularly.<br />
<br />
'''Grit Removal'''<br><br />
Collected grit must be removed from the chamber, dewatered, washed, and conveyed to a disposal or re-use site. Some smaller plants use manual methods to remove grit, but grit removal is usually accomplished by an automatic method. The four methods of automatic grit removal include inclined screw or tubular conveyors, chain and bucket elevators, clamshell buckets, and pumping. <br />
<br />
A two-step grit removal method is sometimes used, where grit is conveyed horizontally in a trough or channel to a hopper, where it is then elevated from the hopper to another location. Aerated grit chambers use a sloped tank bottom in which the air roll pattern sweeps grit along the bottom to the low side of the chamber. A horizontal screw conveyor is typically used to convey settled grit to a hopper at the head of the tank. Another method to remove grit from the chamber floor is a chain and flight mechanism. Once removed from the chamber, grit is usually washed with a hydro cyclone or grit classifier to ease handling and remove organic material. The grit is then conveyed directly to a truck, dumpster, or storage hopper. From there, the grit is taken to a landfill or other disposal or re-use facility.<br />
<br />
===Biogas Settlers===<br />
In settlers that are not designed for anaerobic processes, regular sludge removal is necessary to prevent septic conditions and the build-up and release of gas which can hamper the sedimentation process by re-suspending part of the settled solids. Sludge transported to the surface by gas bubbles is difficult to remove and may pass to the next treatment stage.<br />
<br />
Frequent scum removal and adequate treatment/disposal, either with the sludge or separately, is also important. Anaerobic settlers do have to be emptied less frequently as the organic material is partly transformed into gas. Accumulated slurry in the bottom of the reactor needs to be desludged every two to five years, depending on the type of the reactor (UNEP 2002, MANG 2005). For the operation and maintenance of anaerobic biogas settlers, operational requirements are very low and no professional operator is required as long as the plant is well maintained by skilled users. Starting with the seeding of some sludge from a septic tank or another anaerobic digester speeds up the digestion and prevents the digester from running acid (SASSE, 1998).<br />
===Anaerobic Baffled Reactor===<br />
An Anaerobic Baffled Reactor (ABR) requires a start-up period of several months to reach full treatment capacity since the slow growing anaerobic biomass first needs to be established in the reactor. To reduce start-up time, the ABR can be inoculated with anaerobic bacteria, e.g., by adding fresh cow dung or septic tank sludge. The added stock of active bacteria can then multiply and adapt to the incoming wastewater. Because of the delicate ecology, care should be taken not to discharge harsh chemicals into the ABR.<br />
<br />
Scum and sludge levels need to be monitored to ensure that the tank is functioning well. Process operation in general is not required, and maintenance is limited to the removal of accumulated sludge and scum every 1 to 3 years. This is best done using a motorized emptying and transport technology. The desludging frequency depends on the chosen pre-treatment steps, as well as on the design of the ABR. ABR tanks should be checked from time to time to ensure that they are watertight.<br />
===Anaerobic Filter===<br />
An anaerobic filter (AF) requires a start-up period of 6 to 9 months to reach full treatment capacity since the slow growing anaerobic biomass first needs to be established on the filter media. To reduce start-up time, the filter can be inoculated with anaerobic bacteria, e.g., by spraying Septic Tank sludge onto the filter material. The flow should be gradually increased over time. Because of the delicate ecology, care should be taken not to discharge harsh chemicals into the anaerobic filter. Scum and sludge levels need to be monitored to ensure that the tank is functioning well. Over time, solids will clog the pores of the filter. As well, the growing bacterial mass will become too thick, break off and eventually clog pores. When the efficiency decreases, the filter must be cleaned. This is done by running the system in reverse mode (backwashing) or by removing and cleaning the filter material. Anaerobic filter tanks should be checked from time to time to ensure that they are watertight.<br />
===Up-flow Anaerobic Sludge Blanket Reactor===<br />
The Up-flow Anaerobic Sludge Blanket (UASB) is a Centralized Treatment technology that must be operated and maintained by professionals. A skilled operator is required to monitor the reactor and repair parts, e.g., pumps, in case of problems. Desludging is infrequent and only excess sludge is removed every 2 to 3 years.<br />
===Settling-thickening tanks===<br />
Constant monitoring and adaption accordingly are always required. In the design phase a series of assumptions are made in order to design the operation. The operation cycle consists of 1) faecal sludge loading, 2) thickened faecal sludge compaction, and 3) bottom sludge and scum removal. Pump failure is a common issue so it is important that it is installed in such a way that it can be accessed without pumping out the tank contents. Pumps should be selected based on the solids concentration of the thickened layer and available energy source. To alleviate frequent problems with pumping, solids are frequently removed by front loaders. Designing for manual removal using shovels is not recommended due to the difficult nature of removal.<br />
<br />
The Total Suspended Solids (TSS) concentration of the supernatant will guide one in the treatment performance of the settling-thickening tank. If the TSS concentration is not suitable for the subsequent effluent treatment technology, a change in design, incoming faecal sludge, inlet/outlet design and/or more frequent desludging might be required.<br />
===Unplanted Sludge drying beds===<br />
Operation and maintenance to consider for unplanted sludge drying beds include:<br><br />
(a) Sand and gravel must be washed prior to placing it in the filter to remove dust particles which could cause clogging of the beds,<br><br />
(b) When loading it is very important not to exceed the recommended loading rates (hydraulic or solids),<br><br />
(c) Faecal sludge can only be loaded onto the sludge drying beds once during each drying cycle. Partially dewatered faecal sludge forms a crust on the surface that prevents liquid from passing down to the sand layer and percolating through the drying bed,<br><br />
(d) Incorrect loading can lead to ponding or clogging of beds. If clogging occurs, the entire sand and gravel layer needs to be washed or replaced,<br><br />
(e) Solids removal is labour intensive, so adequate time needs to be estimated to ensure that loading cycles can be maintained,<br><br />
(f) During solids removal, measures need to be taken to minimize the sand loss, as the sand layer is slowly removed, it needs to be replaced,<br><br />
(g) Electrical operation and maintenance must be included if pumps are used for loading of the drying beds. Examples are spare parts and fuel,<br><br />
(h) It is important to monitor the leachate as an indicator of the sludge drying bed performance (e.g. total volumes, TS concentration).<br><br />
<br />
===Planted Sludge Drying Beds===<br />
The following list presents key considerations for operation and maintenance of planted sludge drying beds:<br><br />
(a) It is important to have trained operators who operate and maintain the sludge drying beds, especially during the acclimation period;<br><br />
(b) During loading, make sure the faecal sludge is well distributed, especially during the start-up to ensure the filter media is not disturbed;<br><br />
(c) Plant survival is crucial for treatment performance;<br><br />
(d) During the start-up, the solids loading rates and feeding intervals need to be further evaluated to ensure adequate frequencies and loadings for plant health;<br><br />
(e) Optimal plant densities and harvesting frequencies should be evaluated;<br><br />
(f) Harvest plants by cutting them at the surface; avoid pulling them out because this will damage the root system and drying bed filter material;<br><br />
(g) Monitor the drainage system and effluent for treatment performance and any possible changes;<br><br />
(h) Remember that wildlife might be attracted to the plants, so fencing and measures to decrease possible vector-borne diseases might be required.<br><br />
<br />
===Co-composting===<br />
Co-composting needs to be monitored continuously in order to ensure adequate temperature and moisture content to achieve the treatment objectives. In addition, specific operational and maintenance concerns include:<br><br />
(a) When turning the pile, all parts must be exposed to a high temperature in order to kill off the pathogens,<br><br />
(b) The temperature is regulated by turning the pile more often if the temperature is too high. If too low, more water potentially needs to be added and/or the mass of moist input material needs to be increased,<br><br />
(c) The aerobic condition in the pile is facilitated by the heap-turning frequency, which is context-dependent and needs to be determined by trial and error,<br><br />
(d) Mycelium (clumps of white threads) and small insects are present to break down complex organic material and particles,<br><br />
(e) Odour problems can be a sign of too high a moisture content and can be reduced by increased turning and the addition of coarse material,<br><br />
(f) It may be necessary to cover co-compost piles to either protect from, or to maintain, humidity,<br><br />
(g) Large amounts of flies, insects and rodents must be avoided. Covering the pile could reduce the number of flies, insects and rodents gathering,<br><br />
(h) Compost as a product is sieved to separate coarse and fine compost. The coarse compost is re-used in the next round of co-composting while the fine compost is ready to be used as a soil amendment.<br><br />
<br />
===Co-treatment of Faecal Sludge with Wastewater===<br />
Implementation of co-treatment needs to be carefully monitored. Re-evaluate the treatment capacity and performance frequently to monitor for any unforeseen change in influent values. The risk of failure cannot be stressed enough, as co-treatment has been the cause of many treatment plant failures.<br />
===Effluent Treatment Technologies===<br />
The operation and maintenance of the effluent treatment has to be carried out by qualified staff according to the selected treatment options, for example, if the biological nature of the treatment is complex and sensitive to inflow fluctuation. If transferring or innovative technologies are selected, they need to be closely monitored so that the operation can be adapted as needed.<br />
===Waste Stabilization Ponds===<br />
'''Operation and maintenance of waste stabilization ponds'''<br><br />
The operation of the waste stabilization ponds (WSPs) includes the commissioning (starting up), maintaining and monitoring its performance.<br />
<br />
'''Starting up of waste stabilization ponds'''<br><br />
Anaerobic ponds have to be filled with raw sewage and seeded with sludge from conventional sewage treatment plant or septic tank. After filling and seeding then the pond should be gradually loaded up to the design-loading rate. The pond contents should have a pH above 7 to allow the development of methanogenic bacteria. Add lime or soda ash to rise the pH in the pond if necessary. If the sewerage system is new and the flow rate as well as the loading rate to the anaerobic pond is low, then the sewage may be by-passed till the flow rate and the loading rate from the sewerage systems satisfies the condition to be discharged in the WSP. It is important to have by-pass from the anaerobic pond that will be used during desludging. It is also recommended to commission the WSPs during the beginning of the hot season so as to allow quick establishment of microorganisms of importance for the waste stabilization ponds. <br />
<br />
The facultative WSP should be commissioned before the anaerobic WSP in order to avoid odour during the release of anaerobic pond effluent to an empty facultative WSP. During the start-up of the facultative and maturation WSPs, they should be filled with freshwater (from tap, river or wells). This will allow gradual development of algae and heterotrophic bacteria population. However, primary facultative ponds must be seeded as the anaerobic WSP. If fresh water is not available, the secondary facultative and maturation WSPs should be filled with raw sewage and leave them for three to four weeks to allow development of the microbial population. <br />
<br />
'''Maintenance'''<br><br />
Maintenance for the WSPs should be carried regularly to avoid odour, flies and mosquitoes nuisance. The routine maintenance involves:<br><br />
(a) Removal of screenings and grit from the inlets and outlets works,<br><br />
(b) Cutting grass on the embankment and removing it so that it should not fall in the WSPs,<br><br />
(c) Removing floating scum and floating macrophytes from the surface of the maturation and facultative WSPs,<br><br />
(d) Spraying scum on the surface of anaerobic WSPs and should not be removed as it helps the treatment processes,<br><br />
(e) Removal of any accumulated solids in the inlets and outlet works,<br><br />
(f) Repair any damaged embankment as soon as possible,<br><br />
(g) Repair any damage on fence and gate.<br><br />
<br />
The operator must be given precise information on what to do at the WSP site. A clear form should be prepared showing the tasks to be performed by the operator that should be counter-checked by the foreman/supervisor weekly. Mara (1987) recommends that, for proper operation of the WSPs there should be a manager, assistant manager, engineers, works foreman, laboratory chemist, assistant laboratory chemist, technicians, artisan and the clerk. The number of staff depends on how extensive the project is and also on the population served as well as the degree of mechanisation aspired for.<br />
<br />
Anaerobic WSPs requires desludging when they are one third full of the sludge by volume. <br />
<br />
n=V/3Ps (15.1)<br />
<br />
Where, V is the volume of the anaerobic pond (m3), P is the population served, s is the sludge accumulation rate (m3/person year) and n is the interval in years (every few years).<br />
<br />
The value of “s” is usually 0.04 m3/person year. Sometimes the precise time to desludge the anaerobic WSP is determined by the use of the “white towel”. Mara (1987) recommends the desludging frequency to be annually. The sludge from the pond may be disposed into sludge lagoon or tankers that transport to the landfill site, agricultural land or other suitable disposal area. The disposal of sludge should be undertaken in accordance with the local regulations. <br />
'''<br />
Monitoring and evaluation of the performance'''<br><br />
Frequent monitoring of the final effluent quality of a WSP system has the following importance:<br><br />
(a) Regular assessment as to whether the effluent is complying with the local discharge or re-use standards,<br><br />
(b) To detect any sudden failure or if the WSP effluent has started to deteriorate and may help to give the causes and the remedial actions to be taken.<br><br />
<br />
Two levels of monitoring are recommended, Level 1 representative samples of the final effluent should be taken at least monthly or weekly and should be analysed for those parameters for which effluent discharge or re-use requirements exists. Level 2 when level 1 show that the effluent is failing to meet the standards, a more detailed study is necessary. 24-hour flow weighted composite samples are preferable for most of the parameters to be analysed, although grab samples are necessary for some (pH, temperature and faecal coliforms). The methods for collecting composite samples are as follows:<br><br />
(a) Automatic sampler, which takes samples every after one to two hours with subsequent manual flow weighting if this is not done automatically,<br><br />
(b) Taking grab samples every one to three hours with subsequent manual flow weighting,<br><br />
(c) Taking column sample near the outlet of the final WSP.<br><br />
<br />
A full evaluation of the performance of the WSP systems can be is a time consuming and an expensive process and requires experienced personnel to interpret the results. Details on how to collect samples for evaluation of the performance of the WSP is given by Mara (1987). The evaluation of the WSP performance has the following significance:<br><br />
(a) Provides information on how the WSP is under loaded or overloaded,<br><br />
(b) Indicate how much further loading may safely be added to the system as the community increases,<br><br />
(c) Indicate how the future design be improved in the region.<br><br />
<br />
===Constructed Wetlands===<br />
'''Commissioning''' <br><br />
The commissioning of the constructed wetland involved putting substrate, filling the wetland to the level required, and planting macrophytes. Sometimes commissioning of the wetland is referred to as the time from planting to the date where the wetland is considered operational. Operation during this period should ensure an adequate cover of the wetland vegetation. Water level within the wetland during this time needs to be controlled carefully to prevent seedlings from being desiccated or drowned. Once the plants have been established, the water level may then have to be raised to operational level. Plant loss may occur during the commissioning and hence must be transplanted. <br />
<br />
'''Operation'''<br><br />
The operation of the constructed wetland depends on the type of wetland and the number of preliminary treatment units used for wastewater treatment. Constructed wetlands are designed to be passive and low maintenance, not requiring continual upkeep. Constructed wetlands are however dynamic ecosystems with many variables that require managing and problem may occur when; the operator does not understand operation and maintenance, the wetland is overloaded either hydraulically or organically, unavoidable disasters such as flooding and drought, the wetland is plagued by weed problems and if excessive amount of sediments, litter and pollutants accumulate and are not removed from the wetland. <br />
<br />
The management of the constructed wetlands consists of four tasks as shown in Table 15.2.<br />
[[File:Chapter_15_document_3.PNG|600px|center|link=Chapter_Fifteen:_Operation_and_Maintenance_of_Sanitation_Project&action9]]<br><br />
<br />
Not all constructed wetlands are similar as they can be designed for a range of objectives. These objectives will determine the kind of the operation and maintenance activities to be undertaken. Operation and maintenance of the constructed wetland therefore need to be tailored to a particular constructed wetland, reflecting desired objectives and site specific constraints such as local hydrology, salinity, climate and relevant aspects of public safety. The essential elements of the operation and maintenance of the constructed wetland include:<br />
<br />
* Description of the wetland and its objectives,<br><br />
* List of tasks or management,<br><br />
* Monitoring activities which include inspection checklist.<br><br />
<br />
The operation of the constructed wetland after commissioning must include:<br><br />
(a) Maintenance of the embankments,<br><br />
(b) Removal of litter and debris,<br><br />
(c) Check the flow rate to the constructed wetland if it is in accordance with the design,<br><br />
(d) Remove any blockages in the inlet and outlet works,<br><br />
(e) Replace plants as required,<br><br />
(f) Remove any unwanted weed species from the constructed wetland,<br><br />
(g) Plants should be checked for any sign of diseases,v<br />
(h) Protect deep open water,<br><br />
(i) Correct erosion and slumping,<br><br />
(j) Check any signs of over flooding for subsurface flow constructed wetlands.<br><br />
<br />
These may be prepared in form of a checklist that will direct what maintenance is required and should be contacted immediately.<br />
<br />
'''Monitoring'''<br><br />
Monitoring selected performance parameters should provide enough information to measure performance in meeting wetland objectives. If water quality improvement is the primary objective, then the performance indicator should be either presented as concentration or loads at the outlet or a comparison of inflow and outflow also in terms of concentration or loads. If motoring indicates that the system is not working according to the design objectives, then corrective measures must be applied. Improvement of water quality may be assessed by monitoring a range of inflow and outflow water quality parameters. The useful parameters for monitoring the wetland performance are: DO, BOD, COD, total phosphorous, orthophosphorous, total nitrogen, total kjeldhal nitrogen, ammonia nitrogen, oxidized nitrogen, faecal coliforms, pH, suspended solids, electoral conductivity and heavy metals. Flow rate to and from the constructed wetland must be measured. Sampling may be done using automatic samplers or manual sampling. Sometimes samples within the wetland must be taken for the purposes of comparison. <br />
'''<br />
Decommissioning and refitting'''<br><br />
Decommissioning and refitting of the constructed wetland may take place if its design lifetime is over. At the end of the design life, a wetland will be either refitted or decommissioned if no longer required. Refitting may be required when accumulation of wetland sediments is adversely affecting the wetland performance or changing the catchments conditions require modifications of the wetland. Major refits may include the removal of accumulated peat, including aquatic plants and the replacements of substrates. Decommissioning of the wetlands may be required if the land which supports it is resumed for other purposes, or if the wetland is unable to function to satisfy its original design objectives.<br />
<br />
===Trickling Filter===<br />
A skilled operator is required to monitor the filter and repair the pump in case of problems. The sludge that accumulates on the filter must be periodically washed down to prevent clogging and keep the biofilm thin and aerobic. High hydraulic loading rates (flushing doses) can be used to flush the filter. Optimum dosing rates and flushing frequency should be determined from the field operation.<br />
<br />
The packing must be kept moist. This may be problematic at night when the water flow is reduced or when there are power failures. Snails grazing on the biofilm and filter flies are well known problems associated with trickling filters and must be handled by backwashing and periodic flooding.<br />
===Activated Sludge (AS)===<br />
Highly trained staff is required for maintenance and trouble-shooting as plants. The mechanical equipment (mixers, aerators and pumps) must be constantly maintained. A continuous supply of oxygen and ''sludge'' is essential (WSP, 2008). Control of concentrations of ''sludge'' and oxygen levels in the aeration tanks is required and technical appliances (e.g. ''pH-meter'', '''temperature''', oxygen content, etc.) need to be maintained carefully. As well, ''the influent and effluent'' must be constantly monitored and the control parameters adjusted, if necessary, to avoid abnormalities that could kill the active ''biomass'' and the development of detrimental organisms which could impair the process (e.g. filamentous ''bacteria'').<br />
<br />
Two of the most serious problems with the activated-''sludge'' process are: (1) a phenomenon known as bulking, in which the ''sludge'' from the aeration tank will not settle, and (2) the development of biological surface foam (Crites & Tchobanoglous, 1998). Bulking can be caused either by organisms that grow in filamentous form instead of flocs and will not settle, or the growth of ''micro-organisms'' that incorporate large volumes of water into their cell structure, making their density near that of water. Foaming is caused most often by the excessive growth of an organism called Nocardia (Crites & Tchobanoglous, 1998). Filamentous organisms can be controlled by the addition of chemicals (e.g. chlorine or ''hydrogen peroxide'') to the recycled ''activated sludge''; the alteration of the dissolved-oxygen concentration in the aeration tank; the addition of ''nutrients'' and growth factors to favour other ''micro-organisms'' etc. Nocardia can be controlled by avoiding the recycling of the skimmed foam or the addition of a chemical agent (e.g. polymers or chlorine) on the surface (Crites & Tchobanoglous, 1998).<br />
==Resource Re-use and Recovery==<br />
The essential features of resource re-use and recovery have been covered in detail in Section 3.7 of Volume II and hence this is not further discussed in this volume.<br />
==Performance Monitoring==<br />
There are two types of performance monitoring to be considered. The first type is '''“compliance monitoring”'''. This type of monitoring is meant to determine whether sanitation projects comply with the standards and indicator parameter values in the Regulations. The compliance monitoring samples should be analysed in accredited laboratories. The second type is '''“operational monitoring''' Error! Bookmark not defined.” to check that treatment works and distribution networks are operating effectively to deliver sanitation services that meet the standards as specified by TBS (TZS 860) and to provide early warning that a treatment process is failing or there is a problem in the system. The operational monitoring samples need not be analysed in accredited laboratories. They may be analysed in small laboratories/benches at treatment works provided the methods are properly calibrated and subject to analytical quality control. Regulated Water Utility (RWU) should have separate pre-determined compliance and operational monitoring programmes prescribed by either EWURA or RUWASA.<br />
===Compliance monitoring===<br />
<br />
(a) '''Monitoring categories'''<br><br />
There are two categories of compliance monitoring – '''check monitoring''' and '''audit monitoring''' – to determine compliance with the standards and indicator parameter values in the standards. Check monitoring should be carried out relatively frequently for a limited range of parameters. Audit monitoring has to be carried out less frequently for all the parameters, including those parameters subject to check monitoring. This means that for some parameters the monitoring frequency is the sum of the check and audit monitoring frequencies.<br />
<br />
(b) '''Criteria for check monitoring parameters'''<br><br />
The purpose of check monitoring is regularly to provide information on some selected wastewater quality parameters, in order to determine whether or not sanitation system complies with the relevant parametric values laid down in TZS 800. The parameters for check monitoring are as specified by TBS.<br />
<br />
(c) '''Criteria Audit monitoring parameters'''<br><br />
The purpose of audit monitoring is to provide the information necessary to determine whether or not all the parametric values specified in TZS 860 are complied. All such parameters must be subject to audit monitoring unless specified otherwise, for a period of time to be determined by it, that a parameter is not likely to be present in a given supply in concentrations which could lead to the risk of a breach of the relevant parametric value.<br />
<br />
===Operational monitoring===<br />
Each entity must have an operational monitoring programme for each of its sanitation system. This programme is entirely separate from the compliance sampling programme. Operational monitoring is sampling and analysis carried out to check that sanitation infrastructure are operating effectively to comply with the standards and to provide early warning that the sanitation system is deteriorating, or failing or there is a problem in the system. In general operational monitoring programme should consist of the following elements:<br />
<br />
(a) Monitoring of the source water for parameters that provide a general indication of water quality, which if their concentration or value changed significantly would indicate that there could be deterioration in source water quality. It should also include any parameters that the treatment works is specifically designed to remove;<br><br />
(b) Monitoring of the coagulation, settlement and filtration processes for those parameters that provide evidence of the effectiveness of treatment such as jar tests for optimum coagulation conditions, coagulant residual, pH value and turbidity;<br> <br />
(c) Monitoring of the disinfection process for those parameters that provide evidence of the effectiveness of disinfection such as chlorine residual, pH value and microbiological parameters;<br><br />
(d) Monitoring of the water leaving the treatment works for parameters that the works is designed to remove that are not adequately monitored by the compliance monitoring such as nitrate if nitrate removal id practiced; and<br><br />
(e) Monitoring within the distribution network for parameters that provide evidence that there is no deterioration or contamination within distribution that are not adequately monitored by the compliance monitoring such as chlorine residual.<br><br />
</div><br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Fourteen: Drinking Water and Wastewater Quality Monitoring, Surveillance and Compliance]] << >> Next Page: [[Part_E|Part E: Water Audit, Revenue and Community Participation Management]]</div>Jumahttp://design.maji.go.tz/index.php/Part_DPart D2022-07-16T15:33:23Z<p>Juma: </p>
<hr />
<div>PART D: OPERATION AND MAINTENANCE OF SANITATION PROJECTS<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Fourteen: Drinking Water and Wastewater Quality Monitoring, Surveillance and Compliance]] << >> Next Page: [[Chapter Fifteen: Operation and Maintenance of Sanitation Projects|Chapter Fifteen: Operation and Maintenance of Sanitation Projects]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Fourteen:_Drinking_Water_and_Wastewater_Quality_Monitoring,_Surveillance_and_ComplianceChapter Fourteen: Drinking Water and Wastewater Quality Monitoring, Surveillance and Compliance2022-07-16T15:32:55Z<p>Juma: </p>
<hr />
<div><div style="text-align:justify"><br />
<br />
= Chapter Fourteen: Drinking Water and Wastewater Quality Monitoring, Surveillance and Compliance =<br />
<br />
Drinking water quality monitoring and surveillance of a water supply schemes entails the continuous monitoring of public health along with vigilant assessment and control of safe potable water supply. The Ministry of Water has developed a National Guidelines on Drinking Water Quality Monitoring and Reporting of 2018 which will be reviewed from time to time. The guideline which may be downloaded from the Ministerial website (https://www.maji.go.tz/pages/guidelines) provides systematic steps to be considered during undertaking of water quality monitoring from the catchment/source throughout the water supply system up to the consumer. Also, the quality of portable water has to meet the latest edition of TBS Standards. <br />
<br />
==Importance of Good Water Quality==<br />
<br />
Safe potable water is the first step to promote good health of the community. Experience has shown that community health and water quality are directly related to each other and an improvement of drinking water quality is followed by an improvement in the community’s health. Human activities; rapid industrialization and agrochemical contamination increasingly affect the quality of water resources. Moreover, infant mortality, mostly from diarrheal and other water borne and water related diseases are of great concern. In spite of the significant achievements in improvement of water supply and sanitation services, many factors render good quality water unsafe by the time it reaches the consumers. Poor operation management and unsatisfactory sanitary practices are the major key areas responsible for water contamination. Water quality management and surveillance practices ensure safe water supply to the consumers.<br />
<br />
==Definitions==<br />
<br />
While describing water quality, certain terms are frequently used, which are to be clearly understood and correctly used. Some of the definitions are given below:<br><br />
<br />
(a) Pollution - is the introduction into water of substances in sufficient quantity to affect the original quality of water, make it objectionable to sight, taste, smell or make it less useful,<br><br />
<br />
(b) Contamination- is the introduction into water of toxic materials, bacteria or other deleterious agents that make the water hazardous and therefore unfit for human use (degradation of water quality),<br><br />
<br />
(c) Potable Water - that is satisfactory for drinking purposes from the standpoint of its chemical, physical and biological characteristics. Palatable Water that is appealing to the sense of taste, sight and smell. Palatable water need not always be potable,<br><br />
<br />
(d) Parts per million (ppm) or milligrams per litre (mg/l) - these terms are used to express the concentrations of dissolved or suspended matter in water. The parts per million (ppm) is a weight to weight or volume to volume relationship. Except in highly mineralized water, this quantity would be same as milligram per litre. This is preferable, since it indicates how it is determined in the laboratory,<br><br />
<br />
(e) pH of water - is an expression of the Hydrogen ion concentration. Alkaline water has with pH of above 7 and acidic water has pH of below 7 whereas water with pH 7 is neutral. Physiological effect - having effect on the normal functions of the body. Pathogens disease - producing organisms,<br><br />
(f) Bacteria - a group of universally distributed, essentially unicellular micro-organisms lacking chlorophyll,<br><br />
(g) Virus - the smallest form capable of producing infection and diseases in human beings,<br><br />
(h) Coliform Bacteria - group of bacteria predominantly inhabiting the intestine of human beings and animals, but also occasionally found elsewhere. Used to indicate presence of faecal-pollution,<br><br />
<br />
(i) Enteric - having its normal habitat in the intestinal tract of human beings or animals,<br><br />
<br />
(j) Chlorine Residual - chlorine remaining in the water at the end of a specified period that is not combined with other chemicals and is available to disinfect any additional contaminants introduced to the water,<br> <br />
<br />
(k) Chlorine Demand - the difference between the amounts of chlorine added to water and amount of residual chlorine remaining in the water at the end of a specified period.<br />
<br />
==Water Supply and Surveillance Agencies==<br />
<br />
A water utility is responsible for maintaining the safety of water supplied to the community from the source to the point of consumption. The main objectives of water quality monitoring are:<br><br />
(a) To determine the quality of water in its natural state in view of its present and future needs,<br><br />
(b) To assess the suitability of water for the required use,<br><br />
(c) To find out the pathways for pollution, if any.<br><br />
<br />
Operational and Regulatory Monitoring of water quality involves field and laboratory testing of water samples collected from various points in the water supply system, including the source, water purification plants, service reservoirs distribution systems and consumer end. Continuous water quality monitoring involves good operating practices and preventive maintenance, as well as the regular routine testing and monitoring of water quality to ensure compliance with standards.<br />
<br />
Surveillance is an investigative activity undertaken by a separate agency, to identify and evaluate factors posing a health risk to drinking water. Surveillance requires a systematic programme of surveys that combine water analysis and sanitary inspection of institutional and community aspects, and reporting system. Sanitary inspection of water supply system should cover the whole system including water sources, rising mains, treatment plants, storage reservoirs, and distribution systems; to identify the most common risks and shortcomings in the water supply. Moreover, surveillance is concerned with all sources of water used for domestic purpose by the population, whether supplied by a water supply utility/agency or collected from other individual sources. So it is important to inspect and analyse all sources of water used and intended to be used for human consumption. Surveillance agency should communicate to the water supply utility/agency and pinpoint the risk areas and give advice for remedial action. It should also maintain good communication and co-operation with water supply utility/agency for detection of risk areas and remedial action for betterment of the water supply.<br />
<br />
=== Planning and Implementation ===<br />
<br />
Systematic planning, keeping in view the fundamental objectives, is necessary for successful implementation of drinking water quality control programme.<br />
<br />
=== General Consideration and Strategies ===<br />
<br />
Quality control activities should be initiated as per the norms of national and international guidelines for laboratory analysis. Surveillance agency should carry out periodic surveillance of all aspects of water quality safety including sanitary inspection and spot checks and result should be reported to the concerned water supply organization to implement remedial action when and where necessary.<br />
<br />
Water supply surveillance can be planned in a progressive manner considering the availability of resources. It should start with a basic programme, which could generate useful data to plan advanced surveillance as resources, and conditions permit. The initial pilot scale programme should cover minimum basic strategies including fewer water quality parameters that provide a reasonable degree of public health protection and should be widely applicable. Careful planning of training and resource provision is very essential right from the beginning.<br />
<br />
=== Surveillance Programme ===<br />
<br />
Principally, surveillance activities are similar but the actual extent may differ between urban and rural communities; and according to the types of water supply. They should be adapted to local conditions; availability of local finances, infrastructure and knowledge. Water supply provider and surveillance agencies, depending on resources available with them, will develop the programme for monitoring and surveillance of drinking water quality. Following factors should be taken into consideration while implementing of surveillance activities:<br><br />
(a) The type and size of the water supply systems,<br><br />
(b) The existing and available equipment,<br><br />
(c) Local employment practices and the level of training,<br><br />
(d) Opportunities for community participation,<br><br />
(e) Accessibility of systems keeping in view of geographical and climatic conditions,<br><br />
(f) Communication and transport facilities available.<br />
<br />
=== Information Management ===<br />
<br />
The flow of information between and within the water supply and surveillance agencies is necessary to maximize the quality of service to the consumer and protection of public health. The report provided by the surveillance agency to water supply providers may include but not be limited to:<br><br />
(a) The summary reports of condition of water supply and water quality analysis,<br><br />
(b) Highlight those aspects, which are considered inadequate to sustain the safety of water and needs urgent action,<br><br />
(c) Recommendation of remedial action in case of emergency.<br />
<br />
=== Community Based Monitoring and Surveillance ===<br />
<br />
Community participation is an essential component of the monitoring and surveillance framework. As the primary beneficiaries, community can play an important role in surveillance activity. They are the people who may first notice the problems in water supply system and report it to the concerned water supply utility/agency or take remedial action if possible. Establishing a genuine partnership with the community creates a climate of trust and understanding, which generates interest and enthusiasm. It also provides a good foundation for other educational activities such as promotion of good hygiene practices. <br />
<br />
Health department or water supply utility/agency should help in providing necessary training while community water committee or health committee can supervise the work. The community participation includes:<br><br />
<br />
(a) Assisting field workers in water sample collection, including sample location points, existing damaged networks, causing/likely to cause contamination of drinking water,<br><br />
(b) Assisting in data collection,<br><br />
(c) Monitoring water quantity, quality, and reporting findings to surveillance staff regularly,<br><br />
(d) Ensuring proper use of water supply,<br><br />
(e) Setting priorities for sanitation and hygiene and educate community members,<br><br />
(f) Undertake simple maintenance and repair work. Refer problems which require special attention to the water utility,<br><br />
(g) Disseminate results and explain the implications with respect to health with the objective to stimulate involvement in actions to keep water clean, safe and wholesome.<br />
<br />
=== Surveillance Action ===<br />
<br />
Surveillance action comprises of:<br />
(a) Investigative action to identify and evaluate all possible factors associated with drinking water, which could pose a risk to human health,<br />
(b) Ensure preventive action to be taken to prevent public health problem,<br />
(c) Data analysis and evaluation of the surveys,<br />
(d) Reporting to the concerned authorities the outcome.<br />
<br />
=== Sanitary Survey ===<br />
<br />
Sanitary survey is a periodic audit of all aspects of all the water supply system. Systematic programme of sanitary surveys includes sanitary inspection, water quality analysis, and evaluation of data and reporting.<br />
<br />
Sanitary Inspection Report<br />
The sanitary inspection report shall cover the following:<br />
<br />
(d) Identify potential sources and points of contamination of the water supply,<br />
<br />
(e) Quantify the hazards attributed to the source and supply,<br />
<br />
(f) Provide a clear, graphical means of explaining the hazards to the operator/user,<br />
<br />
(g) Provide clear recommendations for taking remedial actions, to protect and improve the supply,<br />
<br />
(h) Provide basic data for use in systematic, strategic planning for improvement <br />
<br />
<br />
Moreover, inspection reports should not be restricted to water quality but should take in to account other service condition such as coverage, cost, condition and quantity.<br />
<br />
Such surveys are important from the point of view of operation and maintenance.<br />
<br />
== Wastewater Quality Monitoring ==<br />
<br />
Systematic planning as well as keeping in view the fundamental objectives is necessary for successful implementation of wastewater effluent discharges quality control programme. <br />
<br />
=== General Consideration and Strategies ===<br />
<br />
Quality control activities should be initiated as per the norms of national standards and international guidelines for laboratory analysis. Surveillance agency should carry out periodic surveillance of all aspects of wastewater effluent quality discharges including sanitary inspection and spot checks and results should be reported to the concerned utility as well as the regulator to implement remedial action when and where necessary.<br />
<br />
Wastewater effluent surveillance can be planned in a progressive manner considering the availability of resources. It should start with a basic programme, which could generate useful data to plan advanced surveillance as resources, and conditions permit. The wastewater effluent quality discharges should comply with the latest edition of Tanzania Standards, TZS 860, Limits for Municipal and Industrial Wastewaters. The standards prescribe the permissible limits for municipal and industrial effluents discharged directly into water bodies (i.e. receiving water bodies) (EWURA, 2014).<br />
<br />
The initial pilot surveillance scale programme should cover minimum basic strategies including fewer wastewater effluent quality parameters that provide a reasonable degree of public health protection and should be widely applicable. Careful planning of training and resource provision is very essential right from the beginning.<br />
<br />
===Monitoring Programme ===<br />
<br />
Principally, monitoring activities should be adapted to local conditions; availability of local finances, infrastructure and knowledge. WSSA/Agency responsible for wastewater/sanitation management and Surveillance agencies (e.g. EWURA or RUWASA), depending on resources available with them, will develop the programme for monitoring and surveillance of wastewater effluent discharges quality. The following factors should be taken into consideration while implementing of wastewater quality surveillance activities:<br />
<br />
(a) The type and size of the wastewater /sanitation systems,<br />
<br />
(b) The existing and available equipment,<br />
<br />
(c) Local employment practices and the level of training,<br />
<br />
(d) Opportunities for community participation,<br />
<br />
(e) Accessibility of systems keeping in view the geographical and climatic conditions,<br />
<br />
(f) Communication and transport facilities availability.<br />
<br />
===== Wastewater Quality Monitoring Parameters =====<br />
<br />
The selection of parameters that constitute the wastewater quality monitoring programme is to be made on the basis of the latest edition of Tanzania Bureau of Standards: TZS 860. The parameters proposed for regular check monitoring by the Water Supply and Sanitation Authorities (WSSAs)/RUWASA/other agencies should be those required by the latest edition of EWURA water and wastewater quality monitoring guidelines:<br />
<br />
(a) Ammonium,<br />
<br />
(b) Biological Oxygen Demand (BOD),<br />
<br />
(c) Chemical Oxygen Demand (COD),<br />
<br />
(d) Colour,<br />
<br />
(e) Faecal Coliforms,<br />
<br />
(f) Nitrate,<br />
<br />
(g) pH,<br />
<br />
(h) Phosphorus,<br />
<br />
(i) Total Coliforms,<br />
<br />
(j) Total Suspended Solids (TSS).<br />
<br />
The above list of parameters subjected to regular monitoring could be expanded (to include some metals) to take into account the nature of the quality of wastewater collected from industrial, commercial or residential establishments by the sewerage network or brought to the wastewater treatment plants by vacuum trucks. Chemical parameters should be added to the list for monitoring in consultation with Energy and Water Utilities Regulatory Authority (EWURA) or RUWASA or Basin Water Boards and the National Environment Management Council (NEMC).<br />
<br />
===== Audit Monitoring =====<br />
<br />
The Audit Monitoring is to provide information necessary to determine whether or not all the parametric values specified in the latest edition of TZS 860. Limits for Municipal and Industrial Wastewaters are being complied with.<br />
<br />
The selection of parameters that constitute the Audit Monitoring is to be made on the basis of the latest edition of TBS Standards TZS 860. All such parameters must be subjected to audit monitoring, unless it can be established that the nature of the wastewater coming from the sewered area are not expected to contain some of the parameters to be excluded.<br />
<br />
EWURA or RUWASA or any outsourced Agency will carry out monitoring as an external auditor and WSSAs/UWSSAs will conduct monitoring as an internal auditor.<br />
<br />
===== Sampling Locations and Sampling Frequency =====<br />
<br />
Since the effluent standards apply to Municipal, WSSAs, Utility and Industrial effluents discharged directly into water bodies, it implies that sampling locations should be points at which the effluent leaves the wastewater treatment plants just before it enters the receiving water bodies. Sampling locations and sampling frequency should be those required by the latest edition of EWURA water and wastewater quality monitoring guidelines.<br />
<br />
=== Information Management ===<br />
<br />
The flow of information between and within the WSSA/Agency responsible for sanitation management and surveillance agencies (i.e. EWURA or RUWASA & NEMC) is necessary to maximize the quality of service to the consumer and protection of public health. The report provided by the surveillance agency to wastewater management may include but not be limited to:<br />
<br />
(a) The summary reports of condition of wastewater and effluent or faecal sludge quality analysis,<br />
<br />
(b) Highlight those aspects, which are considered inadequate to sustain the quality of wastewater/sludge and needs urgent action,<br />
<br />
(c) Recommendation of remedial action in case of emergency.<br />
<br />
===Community Based Wastewater Quality Monitoring and Surveillance ===<br />
<br />
Community participation is an essential component of the Wastewater quality monitoring and surveillance framework. As the primary beneficiaries, community can play an important role in wastewater surveillance activity. They are the people who may first notice the problems in wastewater / sanitation projects and report it to the concerned WSSA/Utility/agency or take remedial action if possible. Establishing a genuine partnership with the community creates a climate of trust and understanding, which generates interest and enthusiasm. It also provides a good foundation for other community educational activities such as promotion of good hygiene practices. <br />
<br />
The health department or WSSA/Utility responsible for wastewater/ sanitation should help in providing necessary training while CBWSO or the community health committee can supervise the work. The community participation includes:<br />
<br />
(a) Assisting field workers in effluent/discharges sample collection, including sample location points, existing damaged sewers or treatment plants, causing/likely to cause contamination of the environment,<br />
<br />
(b) Assisting in data collection,<br />
<br />
(c) Monitoring wastewater effluent/discharges quantity, quality, and reporting findings to surveillance staff regularly,<br />
<br />
(d) Ensuring proper disposal of effluent /discharges and sludge,<br />
<br />
(e) Setting priorities for sanitation and hygiene and educate community members,<br />
<br />
(f) Undertake simple maintenance and repair work. Refer problems which require special attention to the WSSA/Utility or regulatory agency,<br />
<br />
(g) Disseminate results and explain the implications with respect to health with the objective to stimulate involvement in actions to keep environment clean, safe and wholesome.<br />
<br />
=== Wastewater Quality Monitoring Surveillance Action ===<br />
<br />
Surveillance action comprises of:<br><br />
(a) Investigative action to identify and evaluate all possible factors associated with wastewater effluent discharges and sludge disposal, which could pose a risk to human health and environment in general,<br><br />
(b) Ensure preventive action to be taken to prevent public health problem,<br><br />
(c) Data analysis and evaluation of the surveys,<br><br />
(d) Reporting to the concerned authorities or the regulator the outcome.<br />
<br />
=== Wastewater Effluent Quality Survey ===<br />
<br />
Wastewater effluent quality survey is a periodic audit of all aspects of all the wastewater and sanitation systems. Systematic programme of surveys includes sanitary inspection, wastewater effluent discharges and faecal sludge quality analysis, and evaluation of data and reporting.<br />
<br />
=== Wastewater Quality Inspection Report ===<br />
<br />
The wastewater quality inspection report should cover the following:<br><br />
(a) Identify potential sources and points of contamination due to wastewater effluent discharges and sludge,<br><br />
(b) Quantify the hazards attributed to the ground water sources, water supply network, and storm water,<br><br />
(c) Provide a clear, graphical means of explaining the hazards to the operator/user,<br><br />
(d) Provide clear recommendations for taking remedial actions, to protect and improve the effluent discharges and sludge handling /disposal,<br><br />
(e) Provide basic data for use in systematic, strategic planning for improvement. Moreover, inspection reports should not be restricted to wastewater effluent/ discharges quality but should take into account other service condition such as coverage, cost, condition and quantity. The wastewater quality surveys are important from the point of view of operation and maintenance.<br />
<br />
<br />
Previous Page: [[Chapter_Thirteen:_Treatment_for_Special_Water_Sources]] << >> Next Page: [[Part_D|Part D: Operation and Maintenance of Sanitation Projects]]<br />
<br />
<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_Thirteen:_Treatment_for_Special_Water_SourcesChapter Thirteen: Treatment for Special Water Sources2022-07-16T15:31:56Z<p>Juma: /* CHAPTER THIRTEEN:TREATMENT FOR SPECIAL WATER SOURCES */</p>
<hr />
<div>=Treatment for Special Water Sources=<br />
<br />
Algae, arsenic, cyanobacteria, fluoride and natural organic matters are among water quality parameters that require special treatment to ensure the water produced meet the recommended conditions. Also, because iron as Fe2+ is found in some groundwater, its Operational and Maintenance for iron removal plants (IRPs) is presented in this chapter.<br />
<br />
==Algal Control==<br />
<br />
Algae are unicellular or multi-cellular chlorophyll bearing plants without any true root, stem or leaves. They may be microscopic unicellular colonial or dense mat-forming filamentous forms commonly inhabiting surface waters. Their growth is influenced by a number of factors, such as mineral nutrients, availability of sunlight, temperature and type of reservoir. During certain climatic conditions, there is an algal bloom which creates acute problems in treatment processes and production of potable water. The algae commonly encountered in water purification plants are diatoms, green algae, and blue green algae and algal flagellates. Algae may be seen floating (plankton) in the form of blooms. The problems caused by algae are as follows:<br><br />
(a) Many species of algae produce objectionable taste and odour due to characteristic coil secretions. These also impart colour ranging from yellow-green to green, blue-green, red or brown;<br><br />
(b) Profuse growth of algae interferes with chemical treatment of raw water by changing water PH and its hardness;<br><br />
(c) Some algae act as inhibitors in process of coagulation carried out for water purification;<br><br />
(d) Some algae clog filters and reduce filter run;<br><br />
(e) Some algae produce toxin sand their growth in drinking water reservoirs is harmful for humans and livestock;<br><br />
(f) Some algae provide shelter to a large number of bacteria, some of which may be pathogenic;<br><br />
(g) Some algae corrode metal tanks, forming pits in their walls;<br><br />
(h) Algae may also cause complete disintegration of concrete in contact with them;<br><br />
(i) Prolific growth of algae increases organic content of water, which is an important factor for the development of other organisms.<br />
<br />
===Remedial Measures===<br />
<br />
'''(a) Preventive Measures'''<br><br />
<br />
Preventive measures should, therefore, be based on control of those factors such as:<br><br />
(i) Reduction of food supply,<br><br />
(ii) Change of the environment or exclusion of sunlight though they are not always practicable,<br><br />
(iii) Clear water reservoir, service reservoir s and wells may be covered to exclude sunlight, but such a remedy is obviously inapplicable in the case of large reservoir of raw water,<br><br />
(iv) Turbid water prevents large penetration and thereby reduces algal population,<br><br />
(v) Activated carbon reduces algal population by excluding sunlight but disappearance of activated carbon in the raw water may support algal growth again.<br />
<br />
'''(b) Control Measures'''<br><br />
Adequate records of number, kind and location of algae becomes handy for algal growth control. Algaecide dose used should be harmless to humans, have no effect on water quality, should be inexpensive and readily available and easy to apply. The most commonly used algaecides are copper, sulphate and chlorine/ bleaching powder.<br />
<br />
'''Pre-Chlorination'''<br><br />
Chlorine treatment is relatively cheap, readily available and provides prolonged disinfecting action. Though chlorine is generally used for disinfecting potable water it can also be used as an algaecide. Pre-chlorination has specific toxic effect and it causes death and disintegration of some of the algae. It also assists in removal of algae by coagulation and sedimentation. It prevents growth of algae on basin walls and destroys slime organisms on filter sand thus prolonging filter and facilitating filter washing.<br />
<br />
Dosage: Effective chlorine dose should be such that sufficient chlorine is there to react with organic matter, ammonia, iron, manganese and other reducing substances in water and at the same time leave sufficient chlorine to act as algaecide. Dose required for this purpose may be over 5 mg/L. With chlorine treatment essential oils present in algae as well as organic matter of dead algae are liberated this may lead to development of odour and colour and taste. In such cases break point - chlorination is required. Post chlorination dose can be adjusted to obtain minimum 0.2 mg/ L residual chlorine in potable water at consumer end.<br />
<br />
'''Method of Application''': Chlorine is preferably applied as a strong solution of chlorine from chlorinator. Slurry of bleaching powder can also be used. For algal growth control, generally, chlorine is administered at the entry of raw water before coagulant feeder.<br />
<br />
==Iron Removal Plants (IRPs)==<br />
<br />
Two types of such plants are described below:<br><br />
<br />
===Compact Plant===<br />
<br />
The process involves spray aeration through a grid of pipes to flush out CO2, H2S and to improve pH level. Trickling of aerated water through a contact catalytic media viz., limestone of 20 mm size or a combination of MnO2 (Manganese dioxide) and lime; or hard coke, MnO2 and limestone. The relevant processes are:<br><br />
(a) Sedimentation,<br><br />
(b) Filtration through rapid gravity filter,<br><br />
(c) Disinfection.<br />
<br />
The structure consists of ordinary masonry or concrete. The aerator with contact media may be placed at the top of the sedimentation tank. Sedimentation tank may be rectangular with a length to breadth ratio of 3:1. The detention time may be around 3-5 hours. The surface loading may be around 25 m3/day/m². Filter media shall consist of sand with effective size 0.5-0.7 mm and a depth of 750-1,000 mm over a 450-600 mm deep gravel 3 to 50 mm size.<br />
<br />
====Operation and Maintenance====<br />
<br />
The nozzles/orifices attached to the aeration pipe grid shall have their angles so adjusted as to ensure maximum aeration and to prevent loss of water. These nozzles/orifices shall require regular manual cleaning to remove incrusted iron.<br />
(a) The residual iron deposits from inside the pipe grid shall be flushed out by opening end plugs or flanges. These operations should be repeated at least once in 2 months,<br><br />
(b) The limestone and other contact media require manual cleaning and washing at least once in 45-60 days,<br><br />
(c) The contact media bed should not remain exposed to sun for a long time to prevent hardening of bed by iron incrustation,<br><br />
(d) The sedimentation tank inlet baffle wall opening shall be cleaned of iron slime at least once in 45-60 days,<br><br />
(e) Sedimentation tank bed should be regularly scoured for removal of sludge,<br><br />
(f) Floc forming aid (coagulant aid) may be used for better coalescing and agglomeration,<br><br />
(g) The rapid gravity filter should have a water depth of about 1.2-1.5 m,<br><br />
(h) Since iron deposits create incrustation of filtering media, at least 100-150 mm of tops and layer of sand shall be scrapped and replenished with fresh sand at least once on 60 days. The whole bed may require replacement once in 2 years or so,<br><br />
(i) The characteristics of iron flocs are different from those of surface (river) water flocs. Due to the aeration process and contact of water with air, there may be incrustation of filter bed by residual oxidized deposits. To avoid this, common salt may be mixed with standing water and after 1-2 hours, the filter may be backwashed for better results and longevity of sand bed.<br />
<br />
==Package Type Iron Removal Plant (IRP)==<br />
<br />
The process incorporates the following steps:<br />
<br />
(a) Dosing of sodium aluminates solution to the raw water pumping line, to raise pH up to the optimum level and to ensure subsequent coagulation, as it is an alkaline salt,<br><br />
(b) Injection of compressed air for oxidation of dissolved iron,<br><br />
(c) Thorough mixing of raw water, sodium aluminates and compressed air for proper dispersion in a mixing chamber of mild steel (MS) welded cylindrical shell equipped with one MS perforated plate fitted inside through which the mixture flows upward,<br><br />
(d) Passing the mixture through an oxidation chamber of MS shell, in which a catalytically media of MnO<sub>2</sub> (Manganese dioxide) is sandwiched between two MS perforated circular plates. (Through which the mixture flows),<br><br />
(e) Passing the above mixture in to a MS welded cylindrical shell type of filter in which dual media comprising of Anthracite Coal or high graded bituminous coal, 3-6 mm size, is placed at the top and finer sand of 0.5-1.00 mm size with 98% silica content is placed at the bottom, over a gravel supported bed. At the bottom is the under drainage system. Backwashing is done by air agitation followed by backwash with water,<br><br />
(f) Disinfection.<br />
<br />
'''Operation and Maintenance'''<br><br />
(a) Sodium aluminate should be so mixed as to raise the pH up to 8.5-9.5,<br><br />
(b) The quantity of compressed air should be so regulated as to achieve the optimum oxygen level,<br><br />
(c) The MnO<sub>2</sub> (Manganese dioxide) may need replacement every 6-9 months,<br><br />
(d) The inside of both the mixing chamber and oxidizing chamber should be coated with epoxy resin to avoid corrosion and incursion,<br><br />
(e) The filtration rate should be controlled within a range of 100-125 lpm /m2,<br> <br />
(f) The inlet pipe at the top should be fitted with a cylindrical strainer to obviate the possibility of loss of anthracite coal during washing,<br> <br />
(g) After backwashing, rinsing of filtering media for at least 5 minutes has to be done to resettle the filtering media before normal functioning.<br />
<br />
Where the iron content is very high the whole media like MnO<sub>2</sub> (Manganese dioxide), anthracite coal, sand, gravel, strainers etc. require replacement and replenishment at least once a year for effective functioning and performance. The interior epoxy painting should also be done simultaneously.<br />
<br />
'''Resources for O and M of Iron Removal Plant'''<br><br />
(a) Unskilled labour required for re-sanding. Semi-skilled labour (caretakers) is required for plant operation. Skilled labour (supervising manger) is required for supervision,<br><br />
(b) Materials and equipment include sand, basic tools, valve replacement and spares, flow indicator, turbidity apparatus, bacteriological testing equipment,<br><br />
(c) Finances would typically be from the water organization revenue,<br><br />
(d) The most widely used IRP in the rural area for removing excess iron from drinking water source is based on oxidation, sedimentation and filtration,<br><br />
(e) Specific Treatment Technologies.<br />
<br />
==Brackishness Removal Plant==<br />
<br />
Membrane based desalination plants are mostly known as Reverse Osmosis (RO) plants. The RO design plant technology is dependent on parameters the manufacturer wants to address in a given area.<br />
<br />
Based on the above process each of the manufacturers has designed the treatment units with variable components and design parameters. It is important that O&M manual is obtained from the manufacturer and a guide booklet for field level operators prepared with simple language for their easy understanding. In all such treatment plants the telephone number of the operator should be painted on the building/machinery for contacting them during breakdowns.<br />
<br />
Common operational problems of reverse osmosis include fouling of the membrane if they are not sufficiently protected by the unit operations that are located upstream. It is not uncommon to have either ultrafiltration or microfiltration units upstream of reverse osmosis.<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Twelve: Water Treatment]] << >> Next Page: [[Chapter Fourteen: Drinking Water and Wastewater Quality Monitoring, Surveillance and Compliance]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Twelve:_Water_TreatmentChapter Twelve: Water Treatment2022-07-16T15:31:01Z<p>Juma: /* Operation and Maintenance of Rapid Sand Filters */</p>
<hr />
<div><div style="text-align:justify"><br />
<br />
<br />
= Chapter Twelve: Water Treatment =<br />
<br />
The principal objective of water treatment in water supply industry is to produce water that is fit for domestic use from a raw water source throughout the water supply system to the consumers. The raw water available from sources particularly surface water sources is normally not suitable for drinking purposes. Thus, raw water needs treatment to produce safe and potable drinking water. Some of the common treatment processes of the conventional treatment facilities include the following:<br><br />
(a) Pre-treatment – Scum and floating matters removal, Screening (fine and coarse), Sand trap, Grit removal, Pre-chlorination, <br><br />
(b) Primary treatment – Sedimentation, Primary filtration, Floatation, Aeration.<br><br />
(c) Secondary treatment – Coagulation, Flocculation, Clarification, Filtration, Softening, Reverse Osmosis, Capacitive De-Ionisation (CDI), Ion Exchanger, De-fluoridation, Adsorption, Constructed wetlands.<br><br />
(d) Tertiary treatment – Disinfection, Softening, Utra-filtration, Microfiltration, Nano-filtration, Water conditioning, Water polishing.<br />
<br />
== Pre-treatment ==<br />
<br />
=== Scum and Floating Materials Skimmer ===<br />
<br />
This is the unit operation that enables the manual or automated removal of the scum and floating matter ahead of the screening units. These are designed to skim the entire width of the approach area ahead of the screens. It is one of the most popular styles of scum skimmers used is the scum pipe. It is used in 90%-95% of applications. The other 5% of the time when a skimmer is needed, a helical or paddle wheel skimmer is used. The removal of scum during clarification is an essential step to decrease organic loadings and scum build up in subsequent treatment processes. <br />
<br />
The rotating scum troughs and skimmers efficiently remove all grease, scum and floating material from the water surface in rectangular clarifiers and settling basins. Engineered for both corrosion-resistance and strength, the Scum removal systems are available in non-metallic or metallic designs. The scum skimming blade directs the scum through the opening and into contact with the helical blade, and the helical blade is rotated by the drive unit in a manner tending to keep the scum in the trough while moving the scum lengthwise along the trough to a discharge point outside the tank. In a further embodiment, the trough contains a sloped portion rising above the liquid level to allow the liquids to drain from the scum being transported (Tank Enviro Systems website: https://www.tankenviro.com.au/products/scum-removal).<br />
<br />
=== Screening/Straining ===<br />
<br />
This unit operation consists of fine screens and coarse screens which perform the task of removal of all fine and coarse materials that may block the screen or damage downstream appurtenances or machines. This is a physical, pre-treatment process used to remove weeds, grass, twigs, bilharzial snails and other freshwater crustacean as well as coarser particles including plastics, tins and others so that they do not enter the pumping, treatment, or supply system. Screens are placed at the entrance to the intake of a water supply project<br />
<br />
=== Grit Removal Channels ===<br />
<br />
The purposes of grit channels in the water and wastewater treatment plants are as follows:<br />
* To protect pumps and other mechanical parts from excessive wear and tear,<br><br />
* To avoid undue clogging/filling up of subsequent unit operations,<br><br />
* To differentially remove grit but not the organic particulates in water.<br><br />
<br />
Grit channels are used for peak flow. They should be used either one at a time, or every day. Grit channels should be cleaned every day. Proper and efficient removal of silt in grit channels will improve the functioning of treatment.<br />
<br />
=== Sand Traps ===<br />
<br />
This pre-treatment unit is designed to trap sand after water has been guided into the intake chamber in order to reduce the potential for wear and tear as well as silting up the unit operations that are located downstream of the intake structure. The minimum diameter of such sand traps is 75 mm and the bigger the main intake pipe, the bigger is the flushing pipe for sand.<br />
<br />
=== Pre-chlorination ===<br />
<br />
This is a unit operation that is used for purposes of controlling algae growth in raw water and the process of preparation of the chemical to facilitate dosing should include the standard preparation of the aqueous solution as done during disinfection. This is often added upon establishment of occurrence of algal blooms during certain periods of the year as confirmed by laboratory tests undertaken daily. The amount of the dose should be established daily in order to pre-determine the pre-chlorination dose that has to ensure no interference with downstream unit operations in case the flow sheet involves biological treatment processes like slow sand filter or others.<br />
<br />
=== Pre-Sedimentation Unit ===<br />
<br />
Pre-sedimentation is the removal of coarse suspended matter (such as grit) depending merely on gravity. This type of sedimentation typically takes place in a reservoir, grit basin, debris dam, or sand trap at the beginning of the treatment process. The pre-sedimentation removes most of the sediment from the water at the pre-treatment stage and it reduces the load on the coagulation/flocculation basin and on the sedimentation chamber, as well as reducing the volume of coagulant chemicals required to treat the water.<br />
<br />
For the treatment of highly turbid raw water during the rainy season, solids loadings including larger particles decreased substantially with the application of Pre-sedimentation in the water treatment plant during the rainy season (Kwak et al., 2010). Contaminants from raw water could be removed step-by-step following sequential treatment processes. The selection and arrangement of different treatment processes are of great importance for achieving high contaminant removal efficiency. Pre-sedimentation has various effects on water treatment plant operation, and the produced water depends on raw water quality. <br />
(Source:https://www.researchgate.net/publication/323643034_Pre-sedimentation_tank_effects_on_water_treatment_unit_operation)<br />
<br />
=== Tube Settlers ===<br />
<br />
A set of small diameter tubes (inclined about 60°) having a large wetted perimeter relatively to wetted area when introduced in conventional sedimentation tank, provide laminar flow condition and with low surface loading rate yield good settlement of solids. The tubes which are inclined at about 60 degree found to yield good results. The tubes may be square, circular, hexagonal, diamond shaped, triangular, rectangular shaped. In most of the sedimentation tank the shape will be of thin sheets. There is also another type of settlers widely known as Lamella settlers.<br />
<br />
=== Water Pre-conditioning ===<br />
<br />
Water pre-conditioning can entail a number of pre-treatments undertaken prior to pre-chlorination which is often the final step in pre-treatment. This unit operation involves adjustment of the pH upstream in order to ensure the chemicals used during further treatment processes are dosed to water that has the correct pH range for maximum efficiency.<br />
<br />
== Primary Treatment ==<br />
<br />
=== Sedimentation === <br />
<br />
Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans. Settling basins are ponds constructed for the purpose of removing entrained solids by sedimentation. Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation.<br />
<br />
Sedimentation tank is used as a component of a modern system of water supply or wastewater treatment. It allows suspended particles to settle out of water or wastewater as it flows slowly through the tank by gravity, thereby providing some degree of purification. Suspended materials may be particles, such as clay or silts, originally present in the source water.<br />
<br />
===Lamella Plate Settlers (Inclined Plate Settlers)===<br />
<br />
A lamella clarifier or inclined plate settler (IPS) is a type of settler designed to remove particulates from liquids. They are often employed in primary water treatment in place of conventional settling tanks. They are commonly used in industrial water treatment. Unlike conventional clarifiers they use a series of inclined plates. These inclined plates provide a large effective settling area for a small footprint. The inlet stream is stilled upon entry into the clarifier. Solid particles begin to settle on the plates and begin to accumulate in collection hoppers at the bottom of the clarifier unit. The sludge is drawn off at the bottom of the hoppers and the clarified liquid exits the unit at the top over a weir.<br />
<br />
Lamella clarifiers can be used in a range of industries including mining and metal finishing, as well as used to treat groundwater, industrial process water and backwash from sand filters. Lamella clarifiers are ideal for applications where the solids loading are variable and solids sizing is fine and are more common than conventional clarifiers at many industrial sites due to their smaller footprint. Lamella clarifiers are also used in the municipal wastewater treatment processes (https://en.wikipedia.org/wiki/Lamella_clarifier).<br />
<br />
====Operation and Maintenance of Lamella Settlers====<br />
Properly designed and constructed Lamella plate settlers require minimal operator attention. However, provisions for access and the maintenance should be considered. Access Lamella plate settlers basically require little maintenance. Access walk ways over the basin area if not provided already needs to be provided during maintenance depending upon the requirement of the maintaining agency.<br />
<br />
====Maintenance====<br />
Lamella plate equipment sedimentation basin does not require any adjustment by the operating staff. Normal maintenance is dependent on the materials selected for construction. Periodic disassembly of the plate pack system is recommended if painted carbon steel equipment is used. Stainless steel construction however minimizes routine maintenance. If process upset such as coagulant over dose or biological growth occurs, the basin may have to be drained and or plate cleaned with high pressure hose.<br />
<br />
====Record Keeping====<br />
Daily operations log of process performance and water quality characteristics should:<br><br />
<br />
(a) Record inflow and outflow turbidity and inflow temperature,<br><br />
(b) Process production inventory (amount of water processed and volume of sludge produced),<br><br />
(c) Process equipment performance (type of equipment in operation, maintenance procedures performed and equipment calibration).<br><br />
<br />
==== Cleaning and Maintenance of Lamella Clarifiers ====<br />
It is important to carry out cleaning the Lamella Plate Settlers in order to improve the performance of the lamellar modules and ensure a greater longevity of the installation.<br><br />
<br />
'''(a) Emptying procedure before cleaning'''<br><br />
<br />
(i) While the decanter is still filled with water, start spraying the surface of the lamellar module with pressurized water: pressure should not exceed 6 to 8 bar. Modules should be washed on an ongoing basis. Therefore, it is recommended to have more than 1 worker carrying out the cleaning. In order to water down the lamellas correctly, it is recommended that the maintenance workers walk on the surface of the lamellar modules using wood. In this way, modules are prevented from breaking. These ruptures do not influence performance but they affect the visual aspect of the installation. As the surface of the lamellar module is being sprayed, the water level in the clarifier must descend progressively, especially while the descent affects the length/height of the modules. Close the valves (for short intervals of time) to ensure homogeneous washing. This will dilute any organic matter deposited/adhered on the walls of the pipes and avoid its drying that could reduce the particle slippage, thus impairing the effectiveness of the process;<br />
<br />
(ii) During the emptying of the clarifier, don’t stop spraying the water from the surface downwards, and keep the scraper in operation and the sludge purge pumping because the process tends to produce a lot of solid sedimentation. Perfect sludge collection will ensure greater lamellar performance;<br />
<br />
(iii) Once the clarifier has been emptied, proceed to internal inspection of the equipment. To enter inside the clarifier, you can remove one of the lamellar packs to place a staircase or any other appropriate element to help you go down. It is usually necessary to disarm part of the Ant-Flotation System (AFS) to be able to remove the module;<br />
<br />
(iv) It is important to clean rain gutter channels, especially if they are tubular and with holes.<br />
<br />
'''(b) Parts of the Lamella Settler/Clarifier that need reviewing'''<br><br />
(i) Supporting structure review: if the structure is iron-made, check for any sign of corrosion or degradation;<br><br />
(ii) Review the structure-supporting brackets to ensure that the profiles are correctly fastened to the walls of the clarifier;<br><br />
(iii) Make sure that the lamellas are properly leaning on the supporting structure;<br><br />
(iv) Find out if any of the areas in the lamellar module are still clogged with sludge. Should it be the case, make sure to clean them insistently as they will be the most prone to mud accumulation, which can affect the supporting structure;<br><br />
(v) Review the bottom scraper, its state, the wear of wheels or skates, the state of the concrete. Find out if any replacement is needed.<br><br />
<br />
'''(c) Recommendations'''<br><br />
(i) Before entering the clarifier for inspection purposes, we recommend to make sure that the supporting beams of the lamellar modules have not yielded: sometimes when designing the support structure, only the weight of the lamellar module is taken into account, leaving aside the weight of the sludge. But 1m3 of lamellas, when empty, may weigh 50 kg, however, with 100% sludge, it can weigh up to 1,300 kg. For safety reasons, it is recommended to check the supporting structure before entering the clarifier;<br><br />
(ii) The plant operators know their sludge production and will safely determine when the clarifiers need cleaning. However, it is recommended to carry out maintenance at least 1-2 times a year;<br><br />
(iii) Once the clarifier is clean, it is absolutely necessary to refill it with water. Otherwise, continuous and long-term exposure to the sun may alter the molecular chain of raw materials, causing damages or deformations on the medium term;<br><br />
(iv) Even if lamellas present a constant thickness of 1 mm, they are protected against UV and welded with our system of reinforcement by points, it is advisable to strictly respect the previous recommendation;<br><br />
(v) Should the modules need to be left outdoors without water for longer periods of time, it is recommended to cover them with a tarpaulin to avoid direct contact with the sun;<br><br />
(vi) Please consider that a lamella clarifier produces approximately 4 times more sludge than a clarifier without lamellar modules. Based on this, it is indispensable to equip the clarifier with a perfect lower sludge extraction system to prevent it from collapsing and avoid the sludge to invade clean water collection channels.<br />
<br />
=== Slow Sand Filtration Plant ===<br />
<br />
A Slow Sand Filter Plant consists of a box which is rectangular or circular in shape made either of concrete or masonry. This box is normally one component in a treatment process which may involve preliminary settlement of solids and / or roughing filters and post chlorination. Typically the slow sand filter plant consists of two rectangular operating in parallel, one filter unit is kept in operation and other for maintenance. The filter units also comprise pipe fittings, under drains and graded gravel to support the filter’s sand bed. A flow indicator is used for checking the flow rate. The turbidity of the inlet water is checked to ensure the water is of an acceptable turbidity to prevent rapid blocking of the filter. Turbidity is also measured at the outlet to check the filter is functioning properly. The supervising manager carries out daily bacteriological tests on the filtered water.<br />
<br />
==== Operation and Maintenance of Slow Sand Filter ====<br />
<br />
'''(a) Daily activities'''<br><br />
(i) Check the rate of filtration on the flow indicator – adjust the rate of filtration as needed by turning the filtered water valve;<br><br />
(ii) Check the water level in the filter – adjust the inlet vale as needed to maintain a constant water level;<br><br />
(iii) Remove scum and floating material by further opening the inlet valve for short time;<br><br />
(iv) Check the water level in the clear well;<br><br />
(v) Sample and check water turbidity – if the inflow turbidity is too high close the intake; if the outflow turbidity is too high report to the supervisor;<br><br />
(vi) Testing water quality;<br><br />
(vii) Complete the log book;<br><br />
(viii) Testing Water Quality: Daily monitoring of water quality may be done whether it is slow sand filter or rapid sand filter. If the water supply scheme is having laboratory at the water treatment plant site, water quality testing both the raw water and treated water may be carried out daily.<br />
<br />
'''(b) Weekly activities'''<br><br />
Clean the water treatment plant site.<br><br />
<br />
'''(c) Monthly activities'''<br><br />
(i) Shut down the filter unit – remove scum and floating material; <br><br />
(ii) Brush the filter walls; close the inlet, filtered water and distribution valves; <br><br />
(iii) Drain water to 20 cm below the sand level; <br><br />
(iv) Increase the filtration rate in the other filter to 0.2 m/h;<br><br />
(v) Clean the drained down filter bed – wash boots and equipment before use; scrape upper 2-3 cm in narrow strips and remove scrapings from filter; <br><br />
(vi) Check, and service, exposed inlet and drain valves; remove cleaning equipment and level sand surface; check and record depth of sand bed; <br><br />
(vii) Adjust inlet box to the new sand level;<br><br />
(viii) Re-start the filter – open the recharge valve; check sand surface and level as needed;<br><br />
(ix) When water is 20 cm above the sand, open the inlet valve; <br><br />
(x) Open the filtered water valve and stop when filtration rate reaches 0.02 m/h; <br><br />
(xi) Open waste valve for outflow water to flow to waste; <br><br />
(xii) Open filtered water valve to increase filtration rate every hour by 0.02 m/h until a rate of 0.1 m/h is reached; <br><br />
(xiii) Adjust and check flow daily until safe to drink;<br> <br />
(xiv) Close waste valve and open distribution valve to pass filtered water into the supply; <br><br />
(xv) Decrease filtration rate of other filter to 0.1 m/h;<br><br />
(xvi) Wash the filter scrapings and store the clean sand.<br><br />
<br />
'''(d) Quarterly activities - cleaning of filter''' <br><br />
(i) Close the water inlet and allow the filter to discharge clear water for at least 8-10 hours;<br><br />
(ii) Close the treated water outlet valve;<br><br />
(iii) Open the waste water outlet till the water in the filter bed reaches up to 0.1-0.2 mm from bottom;<br><br />
(iv) Remove wastage on top of the filter; <br><br />
(v) Remove the sand as little as possible, not more than 20-30 mm (the Schmutzdecke). Wastage can be removed manually or with mechanical equipment. Care should be taken to avoid any contamination while removal of waste in the filter tank by observing hygiene and cleaning it as quickly as possible;<br><br />
(vi) Level the sand in the filter;<br><br />
(vii) Re-start the filter by opening inlet valves and outlet valves.<br><br />
<br />
After sand cleaning is done for 20-30 times, the depth of sand layer will decrease and needs to replace.<br><br />
'''(e) Annual activities'''<br><br />
(i) Check if filter is water tight: close all valves and fill filter box from inlet valve until it overflows – close valve; <br><br />
(ii) leave for 24 hours and check if water level reduces; if filter box leaks, report for repair; <br><br />
(iii) open filtered water valve to fill outlet chamber and when full, close valve; leave for 24 hours and check if water level reduces; if chamber leaks, report for repair; <br><br />
(iv) open drain valve to empty filter; clean the clear well in the outlet chamber; <br><br />
(v) restart filter as per the monthly clean plan.<br><br />
<br />
'''(f) Every two – three years, activities'''<br><br />
(i) Re-sand the filter units – clean the filter as in a monthly filter clean; <br><br />
(ii) open drain valve to empty water from the sand bed; <br><br />
(iii) remove strip of old sand to one side; <br><br />
(iv) place new clean sand on top of exposed gravel, and level; <br><br />
(v) place old sand on top of the new sand to the correct depth of 0.8 m in total, and level the surface;<br> <br />
(vi) continue in strips until filter is re-sanded; adjust inlet box to new sand level;<br> <br />
(vii) Re-start the filter as per the monthly clean plan.<br />
<br />
'''(g) Random checks'''<br><br />
Checks on the functioning of the plant by supervising staff including turbidity tests through a turbidity meter, and bacteriological tests of the filtered water.<br />
<br />
'''(h) Record keeping'''<br><br />
Records have to be kept for the following activities:<br><br />
(i) Daily Source water quality,<br><br />
(ii) Daily Treated water quality,<br><br />
(iii) Names of chemicals used,<br><br />
(iv) Rates of feedings of chemicals,<br><br />
(v) Daily consumption of chemical and quality of water treated,<br><br />
(vi) Dates of cleaning of filter feds, sedimentation tank and clear water reservoir,<br><br />
(vii) The date and hour of return to full service (end of re-ripening period),<br><br />
(viii) Raw and filtered water levels (measured each day at the same hour) and daily loss of head, <br><br />
(ix) The filtration rate, the hourly variations, if any,<br><br />
(x) The quality of raw water in physical terms (turbidity, colour) and bacteriological terms (total bacterial count, E.Coli.) determined by samples taken each day at the same hour,<br><br />
(xi) The same quality factors of the filtered water,<br><br />
(xii) Any incidents occurring e.g. plankton development, rising Schmutzdecke, and unusual weather conditions,<br><br />
(xiii) Precautions must be taken to minimize the chances of pollution of the filter bed surface by the labourers themselves.<br><br />
<br />
==== Re-Sanding ====<br />
Re-sanding becomes necessary when the depth of the sand bed drops to its minimum designed level (usually about 0.5 – 0.8 m above the supporting gravel, depending on the grain size of the filter sand/medium). This depth is usually indicated by a marker (such as a concrete block or a step in the filter box wall) set in the structure during the original construction to serve as an indication that this level has been reached and that sanding has become due. After scraping, add new clean sand up to a level shown in Figure 12.1 and place back the old sand that was scraped off the top. The old sand will reduce the number of days needed for ripening the filter.<br />
<br />
[[File:Figure_12Details_of_Cleaning_and_Re-sanding_of_the_SSF.PNG|600px|center|Link=Chapter_Twelve:_Water_Treatment]] <br><br />
Figure 12. 1: Details of Cleaning and Re-sanding of the SSF <br />
(Source: World Bank, 2012)<br />
<br />
=== Roughing Filters === <br />
<br />
'''Operation of Roughing Filter Unit''' <br><br />
Roughing Filter (RF) can easily be operated and maintained by trained local operators/technician/artisans. It does not depend on external inputs provided the necessary materials and tools are available. The daily activities of the caretaker are preferably supported by occasional visits of a supervisor attached to the operation and maintenance section of the governmental institution responsible for the water supply system. Important maintenance work should be carried out at the time when village participation can be involved. This is of particular importance with regard to manual cleaning of the RF.<br />
<br />
Flow Pattern: For operational and economic reasons, it is recommended to continuously operate a RF-SSF plant at constant filtration rates for 24 hours/day. In case of a pumped Scheme, a raw water balancing tank is required. Removal of the coarse solids is a positive side effect of such a tank.<br />
<br />
==== Roughing Filter Cleaning ==== <br />
Filter efficiency is not constant but may increase at the start of filter operation and certainly decreases when solid matter accumulates excessively in the filter. Hence, periodic removal of this accumulated matter restores filter efficiency and keeps the filter in good running condition. Hence, periodic removal of this accumulated matter is required to restore efficiency and possibly hydraulic filter performance. Filters are cleaned either hydraulically or manually, and the cleaning methods are dependent on the way solids accumulate in the filter. Hence, the cleaning procedures will therefore have to be adapted to the different filters. <br />
<br />
==== Roughing Filter Maintenance ==== <br />
Major incidents are often the result of minor causes. This saying also applies to roughing filter maintenance. Filter maintenance is not very demanding as the pre-filters do not include any mechanical parts apart from the valves. Nevertheless, maintenance should aim at maintaining the plant in good condition right from the beginning. External assistance for maintenance work can usually be avoided if the following work is carried out properly by the local operator:<br><br />
(a) periodic upkeep of the treatment plant's premise (grass cutting; removal of small bushes and trees which could impair the structures by their roots; removal of refuse);<br><br />
(b) soil protection against erosion (especially surface water intake structures, the wash water drainage channels and surface runoff);<br><br />
(c) repairing fissures in the walls of the different structures and replacing the chipped plaster;<br><br />
(d) application of anti-corrosive agents to exposed metal parts (V-notch weirs, gauging rods, pipes);<br><br />
(e) checking the different valves and drainage systems, and occasionally lubricating their moving parts;<br><br />
(f) weeding the filter material;<br><br />
(g) skimming off floating material from the free water table;<br><br />
(h) washing out coarse settled material (distribution and inlet boxes);<br><br />
(i) controlling the ancillaries and replacing defective parts (tools and testing equipment).<br><br />
<br />
The term "periodic" does not only apply to the first point in this check list but to all of them. Proper maintenance of the treatment plant guarantees long-term use of the installations at low running costs.<br />
<br />
<br />
=== Bank Filtration === <br />
<br />
Bank filtration is a water treatment technology that consists of extracting water from rivers by pumping wells located in the adjacent alluvial aquifer. During the underground passage, a series of physical, chemical, and biological processes take place, improving the quality of the surface water, substituting or reducing conventional drinking water treatment. <br />
<br />
The efficiency of BF depends on local conditions including the hydrology and hydrogeology of the site, the geochemistry of water (from both the river and the aquifer), the geochemistry of microbial populations, and associated metabolic activity. This is the reason why it is difficult to define general procedures for identifying appropriate sites to implement the BF technique, as well as the expected efficiency of the process.<br />
<br />
'''Optimal BF cleaning frequency'''<br><br />
In general, the typical cleaning frequency is 7-8 years. Based on practical knowledge, the cycle cannot exceed ten years. As this deterioration of the filter layer is a function of the well operation (velocity of the bank filtrate, volume of produced water), a production load-based cleaning cycle.<br />
<br />
<br />
=== Floatation Plant === <br />
<br />
A Dissolved Air Flotation (DAF) system creates microscopic air bubbles that are attached to incoming raw water and wastewater particles in order to float them. Once floated, they are separated from the raw water wastewater and skimmed from the top and into the float scum chamber. The treated water and wastewater then exits from near the bottom of the DAF. The DAF creates air bubbles with a sub-system called a Recycle Air Dissolving (RAD) system. Proper operation of the RAD system is key to DAF performance. The standard configuration RAD system is designed to take treated effluent from the DAF effluent end, pump and pressurize it into the RAD pressure vessel where it is subject to compressed air pressure. The air pressure then dissolves air into the water to become “saturated recycle”. Once saturated the recycle is introduced into the DAF inlet reaction chamber where it co-mingles with raw incoming water and wastewater. When the recycle is co-mingled with water and wastewater the pressure of the saturated recycle is released and bubbles form and are enmeshed with the wastewater particles. <br />
<br />
'''Recycle Air Dissolving Operation''' <br><br />
The RAD creates bubbles by maintaining pressure and an air/water interface in the RAD pressure vessel (stainless steel vertical vessel pictured above right). The interface is maintained by a dual level sensor located in the RAD clear sight tube. When the dual float sensors are wet, the logic says the level is rising and the air pressure supply solenoid is energized and air pressure is added to the RAD vessel. When the dual sensor floats are dry, the logic says the air pressure is excessive and the air supply solenoid is de-energized allowing the level to rise. The level will constantly hunt between (slightly above and below) the two sensor floats. This is normal. <br />
<br />
'''Note:''' The level sensors MUST be maintained clean. If allowed to foul and malfunction the RAD pressure vessel will fill with water and bubbles will NOT be created. They are easy to remove and clean while the RAD is operating by closing the isolation valves and venting pressure with the sight tube drain valve. The supply air pressure regulator must be maintained at minimum 10 psi above the RAD pressure. If the RAD flow rate valves are adjusted the supply air pressure must be checked to ensure it’<br />
<br />
=== Aeration ===<br />
<br />
Aeration is a unit process in which air and water are brought into intimate contact. Turbulence increases the aeration of flowing streams. Aerators bring water and air in close contact in order to remove dissolved gases (such as carbon dioxide) and oxidizes dissolved metals such as iron, hydrogen sulphide, and volatile organic chemicals (VOCs). Aeration unit is often the first major process at the treatment plant. During aeration, constituents are removed or modified before they can interfere with the treatment processes.<br />
<br />
==== Operation and Maintenance of Aerators ====<br />
Two general methods may be used for the aeration of water. The most common in use is the water-fall aerators. Through the use of spray nozzles, the water is broken up into small droplets or a thin film to enhance counter current air contact. In the air diffusion method of aeration, air is diffused into a receiving vessel containing counter-current flowing water, creating very small air bubbles. This ensures good air-water contact for "scrubbing" of undesirable gases from the water.<br />
<br />
==== Operation of Cascade aerator equipment ====<br />
Cascade Aerators induct air into a water flow in order to oxidize iron and reduce dissolved gases. With Cascade Aerators, aeration is accomplished by natural draft units that mix cascading water with air that is naturally inducted into the water flow. Cascade water is pumped to the top of the aerator, and cascades over a series of trays. Air is naturally inducted into the water flow to accomplish iron oxidation and some reduction in dissolved gasses. Cascade Aerators are of non-corroding, all aluminium or stainless construction and have no moving parts, making them maintenance free and inexpensive to buy and operate.<br />
<br />
==== Maintenance of Aeration Equipment ====<br />
<br />
Proper maintenance of aerators is another important area in water treatment activities. Maintenance is on the following elements;<br><br />
<br />
'''1. Waterfall Aerators'''<br><br />
The recommended maintenance procedures for waterfall-type aerators (cascade or step, and tray or splash pan) is as follows:<br><br />
'''(a) Weekly''' <br><br />
(i) Inspect the aerator surfaces for algae or other growths, precipitated iron oxide, and for non-uniformity of water distribution and staining; <br><br />
(ii) Clean when necessary; <br><br />
(iii) Treat with copper sulphate or hypochlorite solution to destroy growths.<br />
<br />
'''(b) Every 6 months''' <br><br />
(i) clean and repair tray aerators, removing the trays as necessary;<br> <br />
(ii) Inspect the coke tray aerators for biological growths and coke deterioration; <br><br />
(iii) Replace the coke if the cleaning is not effective. Repair the screen and enclosures if necessary.<br />
<br />
'''(c) Annually'''<br><br />
(i) Repair or replace the surfaces on cascade or step aerators;<br><br />
(ii) Injection or Diffuser Aerators Injection or diffuser aerators may be either porous medium design or injection nozzles;<br><br />
(iii) Porous Ceramic Diffusers.<br />
<br />
'''2. Porous ceramic diffusers-plate or tube aerators'''<br><br />
The maintenance procedures for porous ceramic diffusers-plate or tube is as follows:<br><br />
<br />
'''(a) Upon evidence of the non-uniform distribution of air or clogging that impairs operation,''' <br><br />
(i) dewater the tank; <br><br />
(ii) inspect; and <br><br />
(iii) clean diffusers if necessary.<br><br />
<br />
'''(b) Every 6 months,''' <br><br />
(i) drain the aeration tank and inspect the diffusers for joint leaks, broken diffusers, and clogging;<br> <br />
(ii) Porous ceramic diffusers may suffer clogging of either the waterside or the air side (underside);<br><br />
(iii) for waterside (porous plate diffusers), use oxidizing acids to clean organic growths from the plate surface.<br />
<br />
'''Note:''' Chlorine gas introduced into the air line at intervals between inspections will help hold down organic growths. Removable plates should be soaked in 50 percent nitric acid. Plates grouted in place cannot be treated with nitric acid; use chromic acid (made by adding 1 gram of sodium dichromate to 50 ml of sulphuric acid). Pour approximately 2 fluid ounces on each plate 2 days in a row.<br><br />
'''Warning:''' Acids must be handled carefully. DO NOT pour water into sulphuric or chromic acid, as it will explode or splatter. Such acid will cause severe burns to the skin and clothes. ALWAYS pour acid SLOWLY into the water, while stirring continuously. Acid treatment should only be done only under supervision of a chemist or other qualified personnel. <br><br />
a) [http://Source:http://constructionmanuals.tpub.com/14265/css/Maintenance-of-Aeration-Equipment-294.htm Source:http://constructionmanuals.tpub.com/14265/css/Maintenance-of-Aeration-Equipment-294.htm] <br><br />
b) https://cdn2.hubspot.net/hubfs/541513/Brochures/Brochure-Aerators.pdf<br />
<br />
== Secondary Treatment ==<br />
<br />
=== Clarification ===<br />
<br />
Clarification is a process of removing all kind of particles, sediments, oil, natural organic matter and colour from the water to make it clear. A clarification step is the first part of conventional treatment for water and wastewater treatment. It usually consists of physical and/or chemical treatment. Coagulation is normally followed by flocculation in a clarifier, which could be circular or rectangular in shape. After clarification water is then ready for filtration.<br />
<br />
===Coagulation and Flocculation===<br />
<br />
The term coagulation and flocculation are often used to describe the process of removal of turbidity caused by fine suspension, colloids and organic colours, i.e. non-settle able particles from water.<br />
<br />
<br />
===== Coagulation =====<br />
<br />
(a) '''Chemical Coagulants Commonly Used in Treatment Process'''<br />
<br />
Coagulant chemicals are in two main types including primary coagulants and coagulant aids. Primary coagulants neutralize the electrical charges of particles in the water which causes the particles to clump together well as coagulant aids add density to slow-settling flocs and add toughness to the flocs so that they do not break up during the mixing and settling processes. Primary coagulants are always used in the coagulation/flocculation process while coagulant aids, in contrast, are not always required and are generally used to reduce flocculation time.<br />
<br />
Chemically, coagulant chemicals are either metallic salts (such as alum) or polymers. Polymers are man-made organic compounds made up of a long chain of smaller molecules. Polymers can be cationic (positively charged), anionic (negatively charged) or non-ionic (neutrally charged). Table 12.1 shows some of the common coagulant chemicals and lists whether they are used as primary coagulants or as coagulant aids. The various coagulants are used in treatment process. The common coagulants used in water works practices are salt of aluminium viz. filter alum and liquid alum, sodium aluminate, Poly Aluminium Chloride (PAC), Calcium Hydroxide Calcium Oxide and chlorinated copperas which are an equimolecular mixture of ferrous sulphate and ferric chloride being obtained by chlorinating ferrous sulphate.<br />
<br />
The commonly used coagulant is commercial grade ferric-alum (solid), However, recently, Poly-Aluminum Chloride is also inducted as a coagulant as it gets properly dispersed, does not have any insoluble residue and effect on the settling tanks, requires less space (<50%). However, it has disadvantage of less effective for colour removal.<br />
<br />
Table 12. 1: Types of Coagulants/Aids<br />
<br />
[[File:12.PNG|700px|center]]<br />
*Used as a primary coagulant only in water softening processes.<br />
(Source: Belmont Water Treatment Association as cited in the Water Supply Design Manual, Uganda, 2013).<br />
<br />
<br />
<br />
(b) '''Tips for Selection of Coagulant'''<br />
<br />
Coagulation is a physical and chemical reactions occurring between the alkalinity of the water and the coagulant added to the water, which results in the formation of insoluble flocs. The most important consideration is the selection of the proper type and amount of coagulant chemical to be added to raw water. Over-dosing as well as under-dosing of coagulants may lead to reduced solids removal efficiency. This condition may be corrected by carefully performed Jar tests and verifying process performance after making any change in the process of the coagulation process.<br />
<br />
(c) '''Aluminium Sulphate Coagulant'''<br />
<br />
Aluminium sulphate is a chemical compound with the formula Al2(SO4)3. Aluminium sulphate is mainly used as a flocculating agent in the purification of drinking water and wastewater treatment plants, and also in paper manufacturing. It is recommended to be used as the coagulant of choice in Tanzania<br />
<br />
(d) '''Use of Aluminium Sulphate'''<br />
<br />
Two solution tanks, one for mixing and the other for dosing, between them holding 48 hours of supply, should be provided. The solution strength should be in the range of 5-10%.The solution tanks could be equipped with hand agitators as shown in Figure 12.2.<br />
<br />
[[File:Figure12.PNG|500px|center]]<br />
<br />
Figure 12. 2: Dosing Arrangement for Alum<br />
<br />
<br />
If the alkalinity of the raw water is low, the pH can be appropriately adjusted by adding soda ash in the correct proportions, as determined after carrying out laboratory experiments called “jar tests”. The strength of the soda ash solution required is usually in the range of 1-10%.The solution tanks for soda ash should also hold a total of 48 hours of supply. The chemical solutions should be fed into the raw water by means of gravity dossers, floating balls or other similar simple devices. Dosing pumps should be used only in exceptional cases.<br />
<br />
(e) '''The Jar Test'''<br />
<br />
To determine the correct chemical dosage for aluminium sulphate solution and for water disinfection, jar testing is recommended (normally Jar test experiments are done in the Laboratory). Jar testing entails adjusting the amount of treatment chemicals and the sequence in which they are added to samples of raw water held in jars or beakers. The sample is then stirred so that the formation, development, and settlement of floc can be watched just as it would be in the full scale treatment plant. Jar testing should be done seasonally (temperature), monthly, weekly, daily, or whenever a chemical is being changed, or new pumps, rapid mix motors, new floc motors, or new chemical feeders are installed. There is no set requirement for how often jar testing should be conducted, but the more it is done the better the plant will operate. Optimization is the key to running he plant more efficiently.<br />
<br />
(f) '''Dosing of the coagulant at a spot of maximum turbulence'''<br />
Rapid mix of coagulant at a spot of maximum turbulence, followed by tapered flocculation in three compartmentalized units allows a maximum of mixing(reduced short circuiting), followed by a period of agglomeration intended to build larger fast settling flocs. <br />
<br />
<br />
<br />
(g) '''Mixing'''<br />
The mixing is the process to mix all the coagulant in water rapidly and instantaneously especially in waters with high alkalinity so as to achieve complete homogenization of a coagulant in the water to be treated. Mixing of the coagulant can be satisfactorily accomplished in a special coagulant tank with mixing devices or in the influent channel or a pipeline to the flocculation basin with high flow velocity which produces necessary turbulence.<br />
<br />
To accomplish the mixing, following methods can be used:<br />
<br />
(i) Hydraulic mixing,<br />
<br />
(ii) Mechanical mixing,<br />
<br />
(iii) Diffusers and grid system,<br />
<br />
(iv) Pump-blenders.<br />
<br />
<br />
(h) '''Storage of Aluminium Sulphate'''<br />
<br />
Aluminium sulphate should be stored in a secured, cool, dry, well-ventilated area, removed from oxidising agents, alkalis, most metals, heat or ignition sources and foodstuffs. Ensure containers are adequately labelled, protected from physical damage and sealed when not in use. Check regularly for leaks or spills (if in a solution form). Large storage areas should have appropriate fire protection and ventilation systems.<br />
<br />
(i) '''Health Hazards and Disposal of Waste Solution and Sludge'''<br />
<br />
Aluminium sulphate is categorised as a slightly corrosive, irritant and hazardous substance. This product has the potential to cause adverse health effects with over long exposure time. Use safe work practices to avoid eye or skin contact and inhalation. It may hydrolyse (with addition of water) to sulphuric acid, a strong tissue irritant. If released to water environment; aluminium salts will slowly be precipitated as aluminium hydroxide. This may lower the pH of receiving waters with toxic effects to aquatic organisms. It is not expected to bio- accumulate. Water plants may experience chronic toxicity at around 25 ppm. Before disposal, neutralise the solution with lime, weak alkali or similar. For small amounts, absorb with sand or similar and dispose of to an approved landfill site<br />
<br />
===== Flocculation =====<br />
<br />
(a) '''Flocculation Basin– Operation'''<br />
<br />
The objective of a flocculation basin is to produce a settled water of low turbidity which in turn leads to reasonably longer service period of filter plant.<br />
<br />
(b) '''Clari-flocculator'''<br />
<br />
The flocculators may be circular, square or rectangular. The best flocculation is usually achieved in a compartmentalized basin. The compartments (most often three) are separated by baffles to prevent short circuiting of the water being treated. The turbulence can be reduced gradually by reducing the speed of the mixers in each succeeding tank or by reducing the Surface area of the paddles. This is called tapered-energy mixing. The reason for reducing the speed of the stirrers is to prevent breaking apart the larger flocs, which have already formed. If the floc is broken up nothing is accomplished and the filter gets overloaded.<br />
<br />
(c) '''Coagulation – Flocculation Process Action'''<br />
<br />
Typical jobs performed by an operator in the normal operation of the coagulation-flocculation process include the following:<br />
<br />
(i) Monitor process performance,<br />
<br />
(ii) Evaluate water quality conditions (raw and treated water),<br />
<br />
(iii) Check and adjust process controls and equipment, and<br />
<br />
(iv) Visually inspect facilities.<br />
<br />
<br />
(d) '''Interaction with Sedimentation and Filtration'''<br />
<br />
The processes of coagulation-flocculation are required to precondition or prepare non settle able particles present in the raw water for removal by sedimentation and filtration. Small particles (particularly colloids), without proper coagulation-flocculation are too light to settle out and will not be large enough to be trapped during filtration process. Since the purpose of coagulation–flocculation is to accelerate particle removal, the effectiveness of the sedimentation and filtration processes, as well as overall performance depends upon successful coagulation - flocculation.<br />
<br />
(e) '''Examination of the Floc'''<br />
<br />
• Examine the water samples at several points, en-route the flow line of the water. Look at the clarity of the water between the flocs and study the shape and size of the flocs. Observe the floc as it enters the flocculation basins which should be small and well dispersed throughout the flow;<br />
<br />
• Tiny alum floc may be an indication that the chemical dose is too low. A ‘popcorn flake’ is a desirable floc. If the water has a milky appearance or a bluish tint, the alum dose is probably too high. As the floc moves through the flocculation basins, the size of the floc should be increasing. If the size of the floc increases and then later starts to break up, the mixing intensity of the downstream flocculator may be too high. Thus, the speed of these flocculators needs to be reduced or otherwise the coagulant dosage may be increased;<br />
<br />
• Examine the settlement of the floc in the sedimentation basin. If a lot of flocs are observed flowing over the laundering weirs the floc is too light for the detention time. By increasing the chemical dose or adding a coagulant aid such as a polymer to produce heavier and larger flocs. The appearance of the fine floc particles passing over the weir could be an indication of too much alum and the dose should be reduced. For precise evaluation only one change can be made at a time and evaluate the results.<br />
<br />
<br />
(f) '''Record keeping'''<br />
<br />
Records of the following items should be maintained:<br />
<br />
• Source water quality (pH, turbidity, temperature, alkalinity, chlorine demand and colour;<br />
<br />
• Process water quality (pH, turbidity, and alkalinity);<br />
<br />
• Process production inventories (chemicals used, chemical feed rates, amount of water processed, and amount of chemicals in storage);<br />
<br />
• Process equipment performance (types of equipment in operation, maintenance procedures performed, equipment calibration and adjustments);<br />
<br />
• A plot of key process variables should be maintained. A plot of source water turbidity vs. coagulant dosage should be maintained. If other process variables such as alkalinity or pH vary significantly, these should also be plotted.<br />
<br />
<br />
(g) '''Safety considerations'''<br />
<br />
In the coagulation-flocculation processes, the operator may be exposed to the associated hazards with following:<br />
<br />
• Electrical equipment,<br />
<br />
• Rotating mechanical equipment,<br />
<br />
• Water treatment chemicals,<br />
<br />
• Laboratory reagents (chemicals),<br />
<br />
• Slippery surfaces caused by certain chemicals,<br />
<br />
• Flooding,<br />
<br />
• Confined spaces and underground structures such as valve or pump vaults (toxic and explosives gases, insufficient oxygen). <br />
<br />
<br />
Strict and constant attention must be given to safety procedures. The operator must be trained with general first aid practices such as mouth-to-mouth resuscitation, treatment of common physical injuries, and first aid for chemical exposure (chlorine).<br />
<br />
(h) '''Laboratory Tests'''<br />
<br />
Water quality indicators for the operation of flocculation process include turbidity, alkalinity, chlorine demand, residual chlorine test, colour, pH, temperature, odour and appearance and need to be tested. In multi-habitation or big schemes, a provision of automatic water testing equipment or onsite laboratory at treatment plant may be established and maintained for the purpose.<br />
<br />
<br />
==== Rapid Sand Filtration Plant ====<br />
<br />
This is a process in which water flows onto the top of the filter media and is driven through it by gravity. In passing through the small spaces between the filter's sand grains, impurities are removed. The water continues its way through the support gravel, enters the under-drain system, and then flows to the reservoir. It is the filter media which actually removes the particles from the water. The filter media is routinely cleaned by means of a backwashing process.<br />
<br />
Rapid sand filtration (RSF) is a relatively sophisticated process usually requiring power-operated pumps for backwashing or cleaning the filter bed, and some designs require flow control of the filter outlet. A continuously operating filter will usually require backwashing about every two days or so when raw water is of relatively low turbidity and at least daily during periods of high turbidity. Because of the higher filtration rates, the area requirement for a rapid gravity filtration plant is about 20% of that required for Slow Sand Filters (SSF).<br />
<br />
Initial filtering performance can be re-achieved through a cleaning of the filter bed. This is usually conducted through backwashing: the flow of water is reversed, so that treated water flows backwards through the filter. The sand is re-suspended and the solid matter is separated in the surface water. Often, air is injected additionally to support the cleaning process (WHO 1996). As soon as most particles are washed out and the backward flowing water is clear, the filter is put back to operation. Clearly, relatively large quantities of sludge are generated through backwashing and require some form of treatment before discharge into the environment (UNEP 1998).<br />
<br />
Rapid sand filtration is a highly effective method to remove turbidity if it is correctly applied (Brikke & Bredero 2003). Equally, solids formed during pre-treatment, i.e. coagulation-flocculation, are filtered. A well-operated RSF reduces turbidity to less than 1 NTN and often less than 0.1 NTU (WHO 1996). Regarding the removal of most other contaminants, the RSFs are ineffective. If combined with adequate pre-treatment measures and final disinfection, rapid sand filtration usually produces safe drinking water.<br />
<br />
(a) '''Filter sand''' <br />
<br />
Filter sand is defined in terms of effective size and uniformity coefficient. Effective size is the sieve size in mm that permits 10% by weight to pass. Uniformity in size is specified by the uniformity coefficient which is the ratio between the sieve sizes that will pass 60% by weight and the effective size.<br />
<br />
<br />
Check shape size and quantity of filter sand to the followings:<br />
<br />
(i) Sand shall be of hard and resistant quartz or quartzite and free of clay, fine particles, soft grains and dirt of every description,<br />
<br />
(ii) Effective size shall be 0.4 to 0.7 mm,<br />
<br />
(iii) Uniformity coefficient shall not be more than 1.7 nor less than 1.3,<br />
<br />
(iv) Ignition loss should not exceed 0.7 per cent by weight,<br />
<br />
(v) Soluble fraction in hydrochloric acid shall not exceed 5.0% by weight,<br />
<br />
(vi) Silica content should be not less than 90%,<br />
<br />
(vii) Specific gravity shall be in the range between 2.55 to 2.65,<br />
<br />
(viii) Wearing loss shall not exceed 3%.<br />
<br />
<br />
===== Interaction with Other Treatment Processes =====<br />
<br />
The purpose of RSF is to remove particulate impurities and floc from the raw water. In this regard, the filtration process is the final step in the solids removal process which usually includes the pre-treatment processes of coagulation, flocculation and sedimentation. The degree of treatment applied prior to filtration depends on the quality of water.<br />
<br />
===== Operation and Backwashing =====<br />
<br />
Rapid Sand Filters should be washed before placing them into service.<br />
(a) A filter is usually operated until just before clogging or breakthrough occurs or a specified time period has passed (generally 24 hours). After a filter clogs/breakthrough occurs, the filtration process should be stopped and the filter be taken out of service for cleaning or backwashing;<br />
<br />
(b) The surface wash system should be activated just before the backwash cycle starts to aid in removing and breaking up solids on the filter media and to prevent the development of mud balls. The surface wash system should be stopped before completion of the back-wash cycle to permit proper settling of the filter media;<br />
<br />
(c) A filter wash should begin slowly for about one minute to permit removing of an entrapped air from the filter media, and also to provide uniform expansion of the filter bed. After this period, the full backwash rate can be applied. Sufficient time should be allowed for cleaning of the filter media. Usually when the backwash water coming up through the filter becomes clear, the media is washed. This generally takes from 3 to 8 minutes. If flooding of wash water troughs or carryover of filter media is a problem, the backwash rate must be reduced.<br />
<br />
<br />
A filter is usually operated until just before clogging or breakthrough occurs or a specified time period has passed (generally 24 hours). After a filter clogs/breakthrough occurs, the filtration process is stopped and the filter is taken out of service for cleaning or backwashing.<br />
<br />
<br />
Surface Wash: In order to produce optimum cleaning of the filter media during backwashing and to prevent mud balls, surface wash (supplemental scouring) is usually practiced. Surface wash systems provide additional scrubbing action to remove attached floc and other suspended solids from the filter media.<br />
<br />
===== Operation and Maintenance of Rapid Sand Filters =====<br />
<br />
Operation of a rapid sand filter consists of flow control, regular backwashing and cleaning. The period between backwashes depends on the quality of the influent water and normally lies between 24 – 72 hours (UNEP 1998).The cleaning process requires an interruption of the purification process of 5 - 10 minutes per filter bed. Several parallel filter units are required to guarantee constant water supply. The backwash process must be observed carefully; in particular the rate of flow must be controlled to avoid erosion of the filter medium. Periodic repacking of the filter bed may be required at infrequent intervals to ensure efficient operation (UNEP 1998). Operation and maintenance thus requires skilled and highly reliable workers. Table 12.2 illustrate the details of RSF operation and maintenance.<br />
<br />
<br />
Table 12. 2: Operation and Maintenance Details for RSF<br />
<br />
[[File:12.22.png|700px|center]]<br />
<br />
<br />
====== Operating Procedures ======<br />
<br />
From a water quality point of view, filter effluent turbidity is a good indication of overall process performance. However, monitoring the performance of each of the individual water treatment process including sedimentation is must in order to check water quality or performance changes. Operations are considered to be normal within the operating ranges of the plant, while unusual or difficult to handle condition is abnormal operating condition. In normal operation of the sedimentation process one must monitor the following;<br />
<br />
(a) ''Turbidity of inflow and out flow of Water in the Sedimentation Basin:'' Turbidity of inflow water indicates the floc or solids loading to the sedimentation basin while turbidity of outflow water of the basin indicates the effectiveness or efficiency of the sedimentation process. Low levels of outflow water turbidity to be achieved to minimize the floc loading on the filter.<br />
<br />
(b) ''Temperature of inflow water:'' is important as the water becomes colder, the settling of particles become slow. To compensate for this change, jar tests should be performed and accordingly, the coagulant dosage is to be adjusted to produce a heavier and thus a settle-able floc. Another possibility is to provide longer detention times when water demand decreases.<br />
<br />
(c) ''Visual checks of the sedimentation process:'' should include observation of floc settling characteristics, distribution of floc at the basin inlet and clarity of outflow settled water spilling over the weirs. An uneven distribution of floc or poorly settling floc is an indication of a raw water quality change or there is operational problem.<br />
<br />
(d) ''Process Actions/ steps are as indicated below:''<br />
<br />
(i) Monitor process performance.<br />
<br />
(ii) Evaluate turbidity and make appropriate process changes.<br />
<br />
(iii) Check and adjust processes equipment (change chemical feed rates).<br />
<br />
(iv) Backwash filters.<br />
<br />
(v) Evaluate filter media condition (media loss, mud balls, cracking),<br />
<br />
(vi) Visually inspect facilities.<br />
<br />
<br />
====== Important Process Activities and Precautions ======<br />
<br />
Process performance monitoring is an on-going activity. Check for any treatment process changes or other problems which might affect filtered water quality, such as a chemical feed system failure. Measurement of head-loss built up in the filter media may give a good indication of how well the solids removal process is performing. The total designed head loss from the filter influent to the effluent in a gravity filter is usually about 3 meters. At the beginning of the filtration cycle the actual measured head loss due to clean media and other hydraulic losses are about 0.9 m. This would permit an additional head-loss of about 2.1 m due to solid accumulation in the filter.<br />
<br />
The rate of head-loss build up is an important indication of process performance. Sudden increase in head loss might be an indication of surface sealing of the filter media (lack of depth penetration).Early detection of this condition may require appropriate process changes such as adjustment of chemical filter aid feed rate or adjustment of filtration rate. Monitoring of filter turbidity on a continuous basis with an online turbidity meter may be adopted for obtaining continuous feedback on the performance of the filtration process. In most instances it is desirable to cut off (terminate) filter at a predetermined effluent turbidity level. Preset the filter cut-off control at a point where breakthrough occurrence is noticed/ tested.<br />
<br />
In the filter process, time for completion of normal filter process may be calculated on the basis of the following parameters:<br />
<br />
(a) Head-loss;<br />
<br />
(b) Effluent turbidity level;<br />
<br />
(c) Elapsed run time;<br />
<br />
(d) A predetermined value established for each above parameter as a cut off point for filter operation may be checked and when any of the selves is reached, the filter should be removed from service and backwashed;<br />
<br />
(e) At least once a year, the filter media must be examined and evaluate its overall condition;<br />
<br />
(f) Measure the filter media thickness for an indication of media loss during the back-washing process;<br />
<br />
(g) Mud ball accumulation in the filter media to evaluate the effectiveness of the overall back-washing operation.<br />
<br />
<br />
====== Routine observations ======<br />
<br />
(a) The backwash process to qualitatively assess process performance, <br />
<br />
(b) For media boils (uneven flow distribution) during backwashing, media carry over in to the wash water trough, and <br />
<br />
(c) Clarity of the waste wash-water near the end of the backwash cycle,<br />
<br />
(d) Upon completion of the backwash cycle, observe the condition of the media surface, <br />
<br />
(e) Check for filter sidewall or media surface cracks, <br />
<br />
(f) Routinely inspect physical facilities, equipment as part of good house-keeping and maintenance practices, <br />
<br />
(g) Correct or report the abnormal equipment conditions to the water supply utility/agency for maintenance action.<br />
<br />
<br />
Never bump upon filter to avoid back-washing. Bumping is the act of opening the backwash valve during the course of a filter run to dislodge the trapped solids and increase the length of filter run. This is not a good practice. Shortened filter runs can occur because of air bound filters. Air binding will occur more frequently when large head losses are allowed to develop in the filter. Precautions should be taken to minimize air binding to avoid damage to the filter media.<br />
<br />
====== Record Keeping ======<br />
<br />
A daily operations log of process performance data and water quality characteristics shall be recorded and maintained accurately for the following items:<br />
<br />
(a) Process water quality (turbidity, colour, PH and alkalinity);<br />
<br />
(b) Process operation (filters in service, filtration rates, loss of head, length of filter runs, frequency of backwash, backwash rates, and UFRV unit filter run volume);<br />
<br />
(c) Process water production (water processed, amount of backwash water used, and chemicals used);<br />
<br />
(d) Percentage of water production used to backwash filters;<br />
<br />
(e) Process equipment performance (types of equipment in operation, equipment adjustments, maintenance procedures performed, and equipment calibration).<br />
<br />
<br />
====== Start-up and Shutdown Procedures ======<br />
<br />
'''(a) Routine Procedures'''<br />
Most plants keep all filters into service except unit under backwash operation and maintenance. Filter units are routinely taken off line for backwashing when the media becomes clogged with particulates, turbidity break through occurs or demands for water are reduced.<br />
<br />
'''(b) Implementation of Start-up and Shut-down Procedures'''<br />
<br />
Filter check-out procedures:<br />
<br />
(i) Check operational status of filter; <br />
<br />
(ii) Be sure that the filter media and wash water troughs are clean of all debris such as leaves, twigs, and tools;<br />
<br />
(iii) Check and be sure that all access covers and walk-way gratings are in place;<br />
<br />
(iv) Make sure that the process monitoring equipment such as head-loss and turbidity systems are operational;<br />
<br />
(v) Check the source of back-wash to ensure that it is ready to go.<br />
<br />
<br />
====== Preventive Maintenance Procedures ======<br />
<br />
Preventive maintenance programmes are to assure the continued satisfactory operation of treatment plant facilities by reducing the frequency of break-down failures. Routine maintenance functions of operator may include:<br />
<br />
(i) Keeping electric motors free of dirt, moisture and pests (rodent sand birds);<br />
<br />
(ii) Assuming good ventilation (air circulation) in equipment work areas;<br />
<br />
(iii) Checking pumps and motors for leaks, unusual noise and vibrations or overheating;<br />
<br />
(iv) Maintaining proper lubrication and oil levels;<br />
<br />
(v) Inspecting for alignment of shafts and couplings;<br />
<br />
(vi) Checking bearings for overheating and proper lubrication;<br />
<br />
(vii) Checking the proper valve operation (leakage or jamming);<br />
<br />
(viii) Checking automatic control systems for proper operation;<br />
<br />
(ix) Checking air/vacuum relief systems for proper functioning, dirt and moisture;<br />
<br />
(x) Verifying correct operation of filters and back-washing cycles by observation;<br />
<br />
(xi) Inspecting filter media conditions (look for algae and mud balls and examine gravel and media for proper gradation); <br />
<br />
(xii) Inspecting filter underdrain system (be sure that the under drain openings are not becoming clogged due to media, corrosion nor chemical deposits).<br />
<br />
<br />
====== Safety Considerations ======<br />
<br />
'''(a) Electrical Equipment'''<br />
<br />
(i) Avoid electric shock (use preventive gloves),<br />
<br />
(ii) Avoid grounding yourself in water or on pipes,<br />
<br />
(iii) Ground all electric tools,<br />
<br />
(iv) Lock-out and tag electrical switches and panels when servicing equipment.<br />
<br />
<br />
'''(b) Mechanical Equipment'''<br />
<br />
(i) Use protective guards on rotating equipment,<br />
<br />
(ii) Don’t wear loose clothing around rotating equipment,<br />
<br />
(iii) Keep hands out of energized valves, pumps and other pieces of equipment,<br />
<br />
(iv) Clean –up all lubricant and chemicals pills (slippery surfaces cause bad falls).<br />
<br />
<br />
'''(c) Open – Surface Filter'''<br />
<br />
(i) Use safety devices such as hand rails and ladders,<br />
<br />
(ii) Close all openings and replace safety gratings when finished working,<br />
<br />
(iii) Know the location of all life preservers and other safety devices.<br />
<br />
<br />
'''(d) Valve and Pump Vaults, Sumps, Filter galleries'''<br />
<br />
(i) Be sure that all underground or confined structures are free of hazardous atmospheres (toxic or explosive gases, lack of oxygen)by checking with gas detectors,<br />
<br />
(ii) Work in well ventilated structures (use air circulation fans).<br />
<br />
==== Sedimentation ====<br />
<br />
Sedimentation tank, also called settling tank or clarifier, component of a modern system of water supply or wastewater treatment. A sedimentation tank allows suspended particles to settle out of water or wastewater as it flows slowly through the tank, thereby providing some degree of purification. The purpose of sedimentation process is to remove suspended particles so as to reduce load on Filters. If adequate detention time and basin surface area are provided in the sedimentation basins, solids removal efficiencies can be achieved more than 95%. However, it may not always be the cost effective way to remove suspended solids.<br />
<br />
In low turbid water sources (less than about 10 NTU) effective coagulation, flocculation and filtration may produce satisfactory filtered water without sedimentation. In this case, coagulation-flocculation process is operated to produce a highly filterable tiny floc, which does not readily settle due to its small size; instead the tiny floc is removed by the filters. There is, however, a practical limitation in applying this concept to higher turbidity conditions. If the filters become overloaded with suspended solids, they will quickly clog and need frequent back washing. This can limit plant production and cause degradation in filtered water quality. Thus, the sedimentation process should be operated from the standpoint of overall plant efficiency. If the source water turbidity is only 3 mg/l, and the jar tests indicate that 0.5 mg/l of coagulant is the most effective dosage, then one cannot expect the sedimentation process to remove a significant fraction of the suspended solids. On the other hand, source water turbidity in excess of 50 mg/l will probably require a high coagulant dosage for efficient solids removal and the suspended particles and alum floc should be removed by sedimentation basin.<br />
<br />
<br />
===== Sedimentation Basins =====<br />
<br />
The Basin can be divided into four zones viz. Inlet; Settling; Sludge and Outlet zone. The basins may be of the following types:<br />
<br />
(a) Rectangular basins,<br />
<br />
(b) Circular and square basins,<br />
<br />
(c) High Rate Settlers (Tube Settlers),<br />
<br />
(d) Solid Contact Units (Up-flow solid-contact clarification and up-flow sludge blanket clarification).<br />
<br />
<br />
===== Process Actions =====<br />
<br />
In rectangular and circular sedimentation basins, it is generally possible to make a judgment about the performance of the sedimentation process by observing how far the flocs are visible beyond the basin inlet. When sedimentation is working well, the floc will only be visible for short distance. When the sedimentation is poor, the floc will be visible for a long distance beyond the inlet.<br />
<br />
In up-flow or solid-contact clarifiers, the depth of the sludge blanket and the density of the blanket are useful monitoring tools. If the sludge blanket is of normal density (measured as milligrams of solids per litre of water) but is very close to the surface, more sludge should be wasted. If the blanket is of unusually light density, the coagulation-flocculation process (chemical dosage) must be adjusted to improve performance. <br />
<br />
With any of the sedimentation processes, it is useful to observe the quality of the effluent as it passes over the weir. Flocs coming over at the ends of the basin are indicative of density currents, short circuiting, sludge blankets that are too deep or high flows. The clarity of the outflow is also a reliable indicator of coagulation-flocculation efficiency. Process equipment should be checked regularly to assure adequate performance. Proper operation of sludge removal equipment should be verified each time for its operation, since sludge removal piping systems are subject to clogging. Free flowing sludge can be readily observed if sight glasses are incorporated in the sludge discharge piping. Otherwise, the outlet of the sludge line should be observed during sludge pumping. Frequent clogging of sludge pipe requires increasing frequency of sludge removal equipment and this can be diagnosed by performing sludge solids volume analysis in the laboratory. <br />
<br />
===== Sludge Management =====<br />
<br />
====== Sludge characteristics ======<br />
<br />
Water treatment sludge is typically alum sludge, with solid concentrations varying from 0.25 to 10% when removed from a basin. In gravity flow sludge removal systems, the solid concentration should be limited to about 3%. If the sludge is to be pumped, solids concentrations should be high as 10% for readily transportation. In horizontal flow sedimentation basins preceded by coagulation and flocculation, over 50% of the floc will settle out in the first third of the basin length. Operationally, this must be considered when establishing the frequency of the operation of sludge removal equipment.<br />
<br />
====== Sludge Removal Systems ======<br />
<br />
Sludge which accumulates on the bottom of the sedimentation basins must be removed periodically for the following reasons:<br />
<br />
• To prevent interference with the settling process (such as re-suspension of solids due to scouring);<br />
<br />
• To prevent the sludge from becoming septic or providing an environment for the growth of microorganisms that create taste and odour problems;<br />
<br />
• To prevent excessive reduction in the cross sectional area of the basin (reduction of detention time).<br />
<br />
<br />
In large scale plants, sludge is normally removed on an intermittent basis with the aid of mechanical sludge removal equipment. However, in smaller plants with low solid loading, manual sludge removal may be more cost effective. In manually cleaned basins, the sludge is allowed to accumulate until it reduces settled water quality. High levels of sludge reduce the detention time and floc carries over to the filters. The basin is then dewatered (drained), most of the sludge is removed by stationary or portable pumps, and the remaining sludge is removed with squeegees and hoses. Basin floors are usually sloped towards a drain to help sludge removal. The frequency of shutdown for cleaning will vary from several months to a year or more, depending on source water quality (amount of suspended matter in the water).<br />
<br />
In larger plants, a variety of mechanical devices can be used to remove sludge including:<br />
<br />
• Mechanical rakes,<br />
<br />
• Drag-chain and flights,<br />
<br />
• Travelling bridge.<br />
<br />
<br />
Circular or square basins are usually equipped with rotating sludge rakes. Basin floors are sloped towards the centre and the sludge rakes progressively push the sludge toward a centre outlet. In rectangular basins, the simplest sludge removal mechanism is the chain and flight system.<br />
<br />
====== Sludge Disposal ======<br />
<br />
Disposal of waste from the water treatment plants has become increasingly important with the availability of technology and the need for protection of the environment. Treatment of waste solid adds to the cost of construction and operation of treatment plants.<br />
<br />
Waste from the Water treatment plants comprise of:<br />
<br />
• Sludge from sedimentation of particulate matter in raw water, flocculated and precipitated material resulting from chemical coagulation, or residuals of excess chemical dosages, plankton, etc.,<br />
<br />
• Waste from rinsing backwashing of filter media containing debris, chemical precipitates, straining of organic debris and plankton and residual of excess chemical dosages, etc.; and<br />
<br />
• Waster from regeneration processes of ion exchange softening treatment plant containing cation of calcium, magnesium and unused sodium and anion of chlorides and sulphates originally present in the regenerate.<br />
<br />
<br />
====== Disposal Method ======<br />
<br />
In continuous sludge removal, the feasibility of discharging of water treatment plant sludge to existing sewer nearby should be considered. For lime softening plant sludge, the reclamation by calcining and reuse can be explored. These sludge from clarification units using irons and aluminium coagulant can be dewatered by vacuum filtration. However the method of waste disposal shall conform to the pollution control norms.<br />
<br />
<br />
====== Reuse of Sludge ======<br />
<br />
A large quantity of sludge is generated each year from water treatment plants in Tanzania. Disposing the sludge to the nearest watercourse is the common practice, especially by many urban water utilities, which accumulatively rise the aluminum concentrations in water and consequently in human bodies. Landfill disposal of the sludge is impractical because of the high cost of transportation and depletes the capacity of the landfill. The use of sludge in construction industry is considered to be the most economic and environmentally sound option. Due to the similar mineralogical composition of clay and water treatment plant sludge, various researchers have studied on the reuse of sludge in clay-brick production as a partial substitute for clay in brick manufacturing. However, concluded that by operating at the temperature commonly practiced in the brick kiln, 50 percent was the optimum sludge addition to produce brick from sludge-clay mixture. The produced bricks properties have proved superior to those available in the market.<br />
(Source: https://www.researchgate.net/publication/295548404_Reuse_of_Water_Treatment_Plant_Sludge_in_Brick_Manufacturing)<br />
<br />
<br />
===== Start-up and Shutdown Procedures =====<br />
<br />
In the event of requirement for shut down or start-up of processes on account of maintenance or a major equipment failure, proper procedures must be followed as per recommendations of the manufacturer of the plant and equipment. The procedures, in general, are given below:<br />
<br />
(a) Start up Procedure<br />
<br />
(i) Check operational status, mode of operation of equipment and physical facilities:<br />
<br />
• Check that basin valves are closed,<br />
<br />
• Check that basin isolation gates are closed,<br />
<br />
• Check that launder weir plates are set at equal elevations,<br />
<br />
• Check to ensure that all trash, debris and tools have been removed from basin.<br />
<br />
(ii) Test sludge removal equipment:<br />
<br />
• Check that mechanical equipment is properly lubricated and ready for operation,<br />
<br />
• Observe operation of sludge removal equipment.<br />
<br />
(iii) Sedimentation basin filled with water:<br />
<br />
• Observe proper depth of water in basin,<br />
<br />
• Remove floating debris from basin water surface.<br />
<br />
(iv) Start sample pumps,<br />
<br />
(v) 5) Perform water quality analyses,<br />
<br />
(vi) Operate sludge removal equipment. Be sure that all valves are in the proper position & operational.<br />
<br />
<br />
(b) Shut down Procedures<br />
<br />
(i) Stop flow to sedimentation basin. Install basin isolation gates,<br />
<br />
(ii) Turn off sample pump,<br />
<br />
(iii) Turn off sludge removal equipment,<br />
<br />
(iv) Shut off mechanical equipment and disconnect where appropriate,<br />
<br />
(v) Check that valves are in proper position& operational,<br />
<br />
(vi) Lock out electrical switches and equipment,<br />
<br />
(vii) Dewater basin, if necessary;<br />
<br />
(viii) Be sure that the water table is not high enough to float the empty basin.<br />
<br />
(ix) Open basin drain valves,<br />
<br />
(x) Grease and lubricate all gears, sprockets and mechanical moving parts which have been submerged immediately following dewatering to avoid seize up.<br />
<br />
<br />
===== Equipment =====<br />
<br />
'''(a) Types of support equipment – Operation and Maintenance'''<br />
<br />
The operator should be thoroughly familiar with the operation and maintenance instructions issued by the manufacturer for each specific equipment viz. flow meters and gauges valves control systems; water quality monitors such as turbidity meters; sludge removal equipment; sludge and sump pumps.<br />
<br />
'''Equipment Operation'''<br />
<br />
(i) Check the following: Proper lubrication and operational status of each unit,<br />
<br />
(ii) Excessive noise and vibration, overheating and leakage,<br />
<br />
(iii) Pumps suction and discharge pressure.<br />
<br />
<br />
===== Safety Considerations =====<br />
<br />
(a) '''Electrical Equipment'''<br />
<br />
(i) Avoid electric shock,<br />
<br />
(ii) Avoid grounding yourself in water or on pipes,<br />
<br />
(iii) Ground all electric tools,<br />
<br />
(iv) Use a lock out and tag system for electric equipment or electrically driven mechanical equipment.<br />
<br />
<br />
(b) '''(ii) Mechanical Equipment'''<br />
<br />
(i) Keep protective guards on rotating equipment,<br />
<br />
(ii) Do not wear loose clothing around rotating equipment,<br />
<br />
(iii) Keep hands out of valves, pumps and other equipment,<br />
<br />
(iv) Clean up all lubricant and sludge spills.<br />
<br />
<br />
(c) '''(iii) Open Surface water – filled structures'''<br />
<br />
(i) Use safety devices such as hand rails and ladders,<br />
<br />
(ii) Close all openings,<br />
<br />
(iii) Know the location of all life preservers.<br />
<br />
<br />
(d) '''Valve and Pump Vaults, Sumps'''<br />
<br />
(i) Be sure all underground or confined structures are free of hazardous atmosphere (Toxic or explosive gases, lack of oxygen),<br />
<br />
(ii) Work only in well ventilated structures,<br />
<br />
(iii) Take proper steps against flooding.<br />
<br />
<br />
===== Corrosion Control =====<br />
<br />
All metallic parts which are prone to corrosion must be protected. Corrosion can be controlled to a large extent by applying anti corrosive paints on the steel pipes at the time of construction of the borehole. Non-corrosive casing pipe and strainers (Such as PVC pipes and strainers) can also be used at the time of construction of borehole to avoid corrosion. Some commonly used paints/coatings to control corrosion are of aluminium, asphalt, red lead and coal tar. <br />
<br />
<br />
<br />
===== Preventive Maintenance =====<br />
<br />
Such programmes are designed to assure the continued satisfactory operation of treatment plant by reducing the frequency of breakdown failures. Typical steps should include:<br />
<br />
(a) Keeping electric motors free of dirt and moisture;<br />
<br />
(b) Assuring good ventilation at valve and pump vaults, sumps;<br />
<br />
(c) Checking pumps and motors for leaks, unusual noise and vibrations, overheating or signs of wear;<br />
<br />
(d) Maintaining proper lubrication and oil levels;<br />
<br />
(e) Inspecting alignment of shafts and couplings;<br />
<br />
(f) Checking bearings for overheating and proper lubrication;<br />
<br />
(g) Checking for proper valve operation;<br />
<br />
(h) Checking for free flow of sludge in sludge removal collection and discharge systems;<br />
<br />
(i) Good housekeeping.<br />
<br />
<br />
<br />
<br />
==== Operation and Maintenance for Defluoridation ====<br />
<br />
Fluoride compounds, usually calcium fluoride, are naturally found, usually in low concentration in water. However, water from underground sources can have higher levels of fluoride to the level that it becomes a health hazard. Defluoridation process is both difficult and expensive, more details and standards can be found in Volume I. <br />
<br />
The decision on whether or not to include defluoridation in a water supply scheme considers both number of potential consumers, alternative sources, the financial consequences both in capital and running and whether or not there is a possibility to dilute the water containing the fluoride as a means of reducing the concentration. Defluoridation is necessary when the fluoride concentration is higher than acceptable limits. The methods presented in Volume I may be considered for attaining defluoridised water.<br />
<br />
For the absorption method, the following are the procedures:<br />
<br />
(a) Check filter against growth of algae (if exposed to sunlight),<br />
<br />
(b) Check blocked filter by sedimentation,<br />
<br />
(c) Check fluoride saturation,<br />
<br />
(d) Check treated water quality (fluoride concentration) once per quarter.<br />
<br />
<br />
<br />
=== Tertiary Treatment ===<br />
<br />
==== Disinfection ====<br />
<br />
Drinking water is disinfected to kill bacteria, viruses and parasites, which may exist in the water and may cause illness and disease like Campylobacter, Cholera, Amoebic Dysentery, Giardia (beaver fever) and Cryptosporidium. These organisms usually get into drinking water supplies when source of waters such as lakes or streams, community water transmission pipes or storage reservoirs are contaminated by animal waste or human sewage. Generally, deep wells are safer than shallow wells if chemical contamination is absent. In fact, shallow dug wells are often as contaminated as lakes or streams. The disinfection of potable water is almost universally accomplished by the use of gaseous chlorine or chlorine compounds. Chlorine is easy to apply, measure and control. It persists reasonably well and it is relatively inexpensive. Other methods of disinfection are also available viz. ozone, ultra-violet light, chlorine dioxide, silver ionization.<br />
<br />
<br />
==== Chlorination ====<br />
<br />
The primary objectives of the chlorination process are disinfection, taste and odour control in the system, preventing the growth of algae and other micro-organisms that might interfere with coagulation and flocculation, keeping filter media free of slime growths and mud balls and preventing possible built up of anaerobic bacteria in the filter media, destroying hydrogen sulphide and controlling sulphurous taste and odour in the finished water, removing iron and manganese, bleaching of organic colour.<br />
<br />
Dosage: Effective chlorine dose should be such that sufficient chlorine is there to react with organic matter, ammonia, iron, manganese and other reducing substances in water and at the same time leave sufficient chlorine to act as algaecide. Dose required for this purpose may be over 2mg/L Post chlorination dose can be adjusted to obtain minimum 0.2to 0.5 mg/l residual chlorine in potable water at consumer end.<br />
<br />
===== Effectiveness of Chlorination =====<br />
<br />
Generally, chlorination without filtration or other pre-treatment is effective and adequate only under the following conditions:<br />
<br />
(a) The degree of bacteriological pollution of the water is moderate, reasonably uniform, and not imbedded in suspended solids, for example, within the bodies of worms;<br />
<br />
(b) The turbidity and colour of the water do not exceed 5-10 units;<br />
<br />
(c) The content of iron or manganese or both do not exceed 0.3 mg/L; and<br />
<br />
(d) Taste- or odour-producing substances are absent or do not require chlorine doses that inevitably produce a chlorine taste in the treated water.<br />
<br />
<br />
There is a contact period of at least 20 minutes between the point of chlorination and the first service connection supplied with the water. In cases where water is pumped directly from the source (e.g. well) into the distribution system, chlorine may be applied.<br />
<br />
<br />
===== Chlorination Guideline =====<br />
<br />
(a) Chlorine solutions lose strength while standing or when exposed to air or sunlight. Make fresh solutions frequently to maintain the necessary residual.<br />
<br />
(b) Maintain a free chlorine residual of 0.3 mg/l after 30 minutes contact time. Residual chlorine should be measured every day.<br />
<br />
(c) Once the chlorine dosage is increased to meet greater demand, do not decrease it unless the raw water quality improves.<br />
<br />
(d) When there is a risk of cholera or an outbreak has already occurred, maintain the chlorine residuals as follows:<br />
<br />
(i) Distribution system: 0.5 mg/l<br />
<br />
(ii) Tanker trucks at filling point: 2 mg/l<br />
<br />
<br />
<br />
===== Chlorination Methods =====<br />
<br />
Disinfection is carried out by applying chlorine or chlorine compounds. The methods of application are as follows:<br />
<br />
(a) Preparing weak solution by bleaching powder,<br />
<br />
(b) Preparing weak solution by electrolysing brine solution,<br />
<br />
(c) By adding chlorine either in the form of gas or solution prepared from dissolving chlorine gas in small feed of water.<br />
<br />
<br />
<br />
==== Disinfection by Bleaching Powder ====<br />
<br />
Bleaching powder or calcium hypochlorite is a chlorinated lime, which contains about 25 to 34% of available chlorine by weight. Chlorine being a gas is unstable and as such it is mixed with lime to retain its strength for a longer period, as far as possible. The bleaching powder is hygroscopic in nature. It loses its chlorine strength rapidly due to poor storage and hence should not be stored for more than three months. The method of chlorination by bleaching powder is known as hypo-chlorination. The combined action of hypochlorous acid and hypochlorite ion brings about the disinfection of water.<br />
<br />
<br />
===== Preparation of Solution =====<br />
<br />
The concentrated solution of bleaching powder is prepared in one or two tanks of capacity suitable for 24 hours requirement. The tank inside should be of glazed tiles or stoneware and should be covered. The tank should be under shade and not direct to sunlight.<br />
<br />
(a) The powder is first put on a perforated slab placed longitudinally inside the tank at a higher level, with respect to bed level of tank;<br />
<br />
(b) Water is sprinkled on the powder through a perforated pipe above this perforated slab;<br />
<br />
(c) The solution of bleaching powder and water now enters the tank. The solution is rotated for thorough mixing of powder with water by a hand driven/motor reduction gear operated slow speed stirrer is now ready for use as disinfectant;<br />
<br />
(d) The precipitates of calcium hydroxide settle at the bottom of the tank. The supernatant water, which contains OCl, Cl- plays important role in disinfection;<br />
<br />
(e) For effectiveness of chlorination, contact period of at least 4 hours should be maintained.<br />
<br />
<br />
===== Dosing of Solution =====<br />
<br />
The solution is discharged to a small measuring tank at a lower level through PVC pipe or any other material resistant to chlorine. The level of water in this tank is maintained constant through a float valve. The solution is dosed to the clear water channel by gravity at the time of entry to clear water reservoir. The dose has to be monitored properly, depending on the desired residual chlorine required in clear water reservoir. The waste precipitates at the bottom of tanks are taken out occasionally by scour valve.<br />
<br />
<br />
===== Safety precautions =====<br />
<br />
(a) The operating personnel should use hand gloves, aprons and other protective apparel, while handling and mixing;<br />
<br />
(b) The valves, stirrer, tanks, plumbing arrangements require renovation at every 6 months or so.<br />
<br />
<br />
<br />
==== Chlorination by Gaseous Chlorine ====<br />
<br />
Elemental chlorine at a normal pressure is a toxic, yellow green gas, and is liquid at high pressure. Chlorine gas is released from a liquid chlorine cylinder by a pressure reducing and flow control valve operating at a pressure less than atmospheric pressure. The gas is injected in the water supply pipe where highly pressurized water is passed through a venture creating a vacuum that draws the chlorine in to the water stream. Adequate mixing and contact time must be provided after injection to ensure complete disinfection of pathogens. It may be necessary to control the water pH. A basic system consists of chlorine cylinder mounted with vacuum regulator, chlorine gas injectors, and a contact tank or pipe. Prudence or state regulation would require that a second cylinder and gas regulator be provided with a changeover valve to ensure continuity of disinfection. Additional safety and control system may be required.<br />
<br />
Chlorine is very effective for removing almost all pathogen and is appropriate for both a primary and secondary disinfectant. The limitation with this is it is dangerous gas that is lethal at concentrations as low as 0.1 per cent air by volume.<br />
<br />
<br />
===== Working Safely around Chlorine Gas =====<br />
<br />
Any water utility that uses chlorine should have written procedures for its chlorine system operation. Even the use of powdered chlorine should have written procedures.<br />
Before starting any chlorination process, the following precautions should be taken:<br />
<br />
(a) If a faucet with good flowing water is not available close by, make ready a 5- gallon container of fresh water, but make sure it is away from the chlorine cylinder or storage area. This is to ensure that if the chlorine accidentally comes in contact with your eyes or skin, you can flush the affected areas with copious amounts of fresh water for at least 10-15 minutes,<br />
<br />
(b) Flush the chlorine out. Do not just soak the affected surface. If you get some of the chlorine solution in your eyes, flush it out and immediately see your doctor,<br />
<br />
(c) Wear the prescribed safety clothing and equipment, specifically:<br />
<br />
(i) Goggles to protect your eyes from contact with the chlorine in any form,<br />
<br />
(ii) Rubber gloves and rubber boots certified for use around the chemical to protect your hands and feet,<br />
<br />
(iii) Waterproof suit, coveralls or a full-length apron.<br />
<br />
<br />
===== Housekeeping/Chlorine Storage =====<br />
<br />
(a) Use signs to clearly identify all areas where chlorine is used or stored. Only qualified personnel should be permitted to enter these areas,<br />
<br />
(b) Do not store materials that may react violently with chlorine in the same room as chlorine. Put up visible warning signs prohibiting persons from taking these materials where the chlorine is stored,<br />
<br />
(c) Do not store chlorine near busy roadways or where vehicles operate. Chlorine reacts with carbon monoxide to produce phosgene, an extremely poisonous gas,<br />
<br />
(d) Store chlorine cylinders and containers in a cool, dry, and relatively isolated area, protected from weather and extreme temperatures:<br />
<br />
<br />
(i) When storing cylinders and containers outside, shield them from direct sunlight,<br />
<br />
(ii) When storing chlorine containers inside, store the containers in a well- ventilated building, away from any heat sources.<br />
<br />
(e) Use cylinders and containers on a “First-In, First-Out” basis,<br />
<br />
(f) Clearly tag or mark empty cylinders and separate them from full cylinders,<br />
<br />
(g) Determine the most appropriate location for emergency equipment. Emergency equipment and a faucet should be available in a readily accessible location, but not inside the chlorine room because a worker (and emergency response staff) trying to use the emergency equipment or faucet during a chlorine leak risks further exposure,<br />
<br />
(h) Store cylinders upright and secure them against tipping over and rough handling. Cylinders will discharge vapour when upright and discharge liquid when upside-down. Since chlorine gas tends to sink, provision should be made for low-placed ventilation near the floor that allows it to dissipate outward, as well as high-placed ventilation that allows the chlorine mist (the gas mixed with air) which tends to go upward, also to dissipate.<br />
<br />
<br />
===== Handling Chlorine Cylinders =====<br />
<br />
(a) Handle containers with care while moving or storing them. Do not drop or allow containers to strike objects,<br />
<br />
(b) Use new gaskets as recommended by the chlorine supplier each time a cylinder or container is connected,<br />
<br />
(c) Follow the chlorine supplier’s recommended disposal procedures for leaking containers. Do not modify, alter, or repair containers and valves. Only the supplier should carry out these tasks,<br />
<br />
(d) Ensure that cylinders have valve protection hoods in place when not connected to a system,<br />
<br />
(e) Do not lift a cylinder by its valve protection hood. The hood is not designed to carry the weight of a cylinder,<br />
<br />
(f) If possible, open valves by applying a steady force to a 200 mm (8 in) wrench, without applying an impact force and without using an extension on the wrench. If this does not work, apply a light impact force by smacking the wrench with the heel of your hand,<br />
<br />
(g) Do not use a wrench longer than 200 mm (8 in) to open or close valves. To prevent valve damage that could cause leaks do not use tools such as pipe wrenches or hammers. Valves on cylinders are designed to deliver full volume after one complete counter clockwise turn. Valves may be damaged if turned beyond this point. Immediately return containers with damaged or inoperable (but not leaking) valves to the supplier,<br />
<br />
(h) If the valve is very difficult to open, loosen the packing nut slightly. Tighten the packing nut after the valve is opened or closed.<br />
<br />
(Source: https://www.slideshare.net/esmeraldoerandio/rural-water-supply-volume-iii-operation-and-maintenance-manual-PHILLIPINES)<br />
<br />
<br />
==== Electro-chlorinator ====<br />
<br />
Chlorine is instantly produced by electrolyzing brine solution. Common salt is mixed with water to prepare brine solution. This solution is passed through an Electrolyser of electrodes comprising of anodes and cathodes, which are energised by D.C. current to produce NaOCl. This solution of sodium hypo chlorite is used as disinfectant. Basically, the electro chlorinator set comprises of two compartments; one comprising of brine solution tank, electrolyser, cooler, etc. and the other comprising of compact panel board (rectifier). Normal life of electro chlorinator is 12 years provided reconditioning of the electrodes at regular interval of four years is carried out. <br />
<br />
<br />
==== Other Disinfectants ====<br />
<br />
The other chemical based disinfectants generally in use are ionized silver coating, gaseous chlorine, ozone, chloramine, potassium permanganate and hydrogen peroxide. Alternatives to chemical disinfection, such as UV irradiation, are also being used for disinfection of drinking water.<br />
<br />
<br />
==== Ozonation ====<br />
<br />
Ozone is very strong oxidiser and powerful disinfecting property. Avery small concentration of ozone in water makes it free from bacteria, virus and pathogen much faster and with lesser concentration in a most effective manner. Ozone, an allotrope of oxygen having three atoms to each molecule, is a powerful oxidizing and disinfecting agent. It is formed by passing dry air through a system of high voltage electrodes. The major elements of an ozonation system are:<br />
<br />
(a) Air preparation of oxygen feed,<br />
<br />
(b) Electrical power supply,<br />
<br />
(c) Ozone generation usually using a corona discharge cell consisting of two electrodes,<br />
<br />
(d) Ozone context chamber, and<br />
<br />
(e) Ozone exhausts gas destruction.<br />
<br />
<br />
Advantages of ozonation system is that it requires shorter contact time and doses than chlorine, ozone does not directly produce halogenated organic materials unless a bromide ion is present. Limitations of ozonation system, ozone gas is unstable and must be generated onsite. A secondary disinfectant, usually chlorine, is required because ozone does not maintain an adequate residual in water.<br />
<br />
<br />
==== Operation and Maintenance for Ultra-filtration, Micro filtration and Nano filtration ====<br />
<br />
Basically, ultrafiltration and microfiltration are the protection mechanism of nanofiltration and these should precede Nano filtration, for more details refer Volume I. Because application of membrane filtration technology is still rare in Tanzania at the moment, the current edition of the manual refers designers to the manufacturers of membrane filters for all design specifications sample websites of the manufacturers are provided at the end of this DCOM Manual .<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Part_C|Part C: Operation and Maintenance of Water Treatment]] << >> Next Page: [[Chapter Thirteen: Treatment for Special Water Sources]]<br />
<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Part_CPart C2022-07-16T15:28:37Z<p>Juma: </p>
<hr />
<div>PART C: OPERATION AND MAINTENANCE OF WATER TREATMENT, WATER AND WASTEWATER QUALITY COMPLIANCE<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Eleven: Audit and Conservation of Energy]] << >> Next Page: [[Chapter Twelve: Water Treatment]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Eleven:_Audit_and_Conservation_of_EnergyChapter Eleven: Audit and Conservation of Energy2022-07-16T15:28:07Z<p>Juma: /* CHAPTER ELEVEN: AUDIT AND CONSERVATION OF ENERGY */</p>
<hr />
<div>= Chapter Eleven: Audit and Conservation of Energy =<br />
<br />
== Introduction ==<br />
<div style='text-align: justify;'><br />
Energy is very scarce and short supply commodity particularly in many of the areas in Tanzania and its cost is spirally increasing day-by-day. Generally, pumping installations consume a huge amount of energy wherein proportion of the energy cost can be as high as 40 to 70% and even more of the overall cost of operation and maintenance of water works. The need for conservation of energy, therefore cannot be ignored. All possible steps should be identified and adopted to conserve energy and reduce energy consumption and loss, and cost so that water tariffs can be kept as low as possible and gaps between high cost of production of water and prices affordable by consumers can be reduced. Some adverse scenarios in energy aspects as follows are quite common in pumping installations:<br><br />
<br />
(a) Energy consumption is higher than the optimum value due to reduction in efficiency of the pumps,<br><br />
<br />
(b) Operating point of the pumps is not in-line with the best efficiency point (b.e.p.),<br><br />
<br />
(c) Energy is wasted due to increase in head loss in pumping systems, (e.g. clogging of strainers, encrustation in column pipes, encrustation in pumping mains),<br><br />
<br />
(d) Selection of uneconomical diameter of sluice valves, butterfly valves, reflux valves, column pipe, drop pipe in pumping installations,<br><br />
<br />
(e) Energy wastage due to operation of electrical equipment at low voltage and/or low power factors.<br />
<br />
Such inefficient operation and wastage of energy should be avoided to cut down energy costs. It is therefore, necessary to identify all such shortcomings and causes. The following measures should be adopted in management of energy:<br><br />
(a) Conduct thorough and in-depth energy audit covering analysis and evaluation of all equipment, operations and system components which have bearings on energy consumption, and identifying scope for reduction in energy costs,<br><br />
<br />
(b) Implement measures for conservation of energy,<br><br />
<br />
(c) Energy audit as implied is auditing of billed energy consumption and how the energy is consumed by various units, and sub-units in the installation and whether there is any wastage due to poor efficiency, higher hydraulic or power losses, etc. and identification of actions for remedy and correction,<br><br />
<br />
(d) In respect of the sources like infiltration wells, open wells, collector wells, the working head can be decided based upon the suction head, delivery head, frictional loss with reference to the pipe materials used and other losses,<br><br />
<br />
(e) In respect of borehole sources, while submersible pump sets are used, the pump suction depth may be fixed with reference to the final spring achieved during drilling,<br><br />
<br />
(f) Working of head of pumps should be made in a conservative way,<br><br />
<br />
(g) If the head of the pump is excess of the actual requirement, then pump impeller shall be trimmed as recommended in section 6.2.2.3 of this DCOM Manual,<br><br />
<br />
(h) In large pumping stations, pumps with variable frequency should be used,<br><br />
<br />
(i) With low power factor loads, the current flowing through electrical system components is higher than necessary to do the required work. In order to achieve power factors greater than 0.9 power capacitors of required capacity should be installed on all the installation of pumping machinery,<br><br />
<br />
(j) Electric motors usually run at a constant speed, but a Variable Frequency (speed) Drive (VFD) allows the motor’s energy output to match the required load. This achieves energy savings depending on how the motor is used. When one uses a control valve or regulator, one lose energy because the pumps are always operated at high speed.<br />
<br />
== Scope of the Energy Audit ==<br />
<br />
Energy audit includes the following actions, steps and processes:<br><br />
(a) Conducting in depth energy audit by systematic process of accounting and reconciliation between the following:<br><br />
(i) Actual energy consumption,<br><br />
(ii) Calculated energy consumption taking into account rated efficiency and power losses in all energy utilizing equipment and power transmission system as explained below.<br><br />
<br />
(b) Conducting performance test of pumps and electrical equipment if the difference between actual energy consumption and calculated energy consumption is significant and taking follow up action on conclusions drawn from the tests,<br><br />
(c) Taking up discharge test at rated head if test in (b) above is not being taken,<br><br />
(d) Identifying the equipment, operational aspects and characteristic of power supply causing<br> inefficient functioning, wastage of energy, increase in hydraulic or power losses etc. and evaluating increase in energy cost or wastage of energy,<br><br />
(e) Identifying solutions and actions necessary to correct the shortcomings and lacunas in (d) and evaluating cost of the solutions,<br><br />
(f) Carrying out economic analysis of costs involved in (d) and (e) above and drawing conclusions whether rectification is economical or otherwise,<br><br />
(g) Checking whether pump operating point is near best efficiency point and whether any improvement is possible,<br><br />
(h) Verification of penalties if any, levied by power supply authorities e.g. penalty for poor power factor, penalty for exceeding contract demand. Broad review of following points for future guidance or long term measure:<br><br />
(i) C-value or f-value of transmission main,<br><br />
(ii) Diameter of transmission main provided,<br><br />
(iii) Specified duty point for pump and operating range,<br><br />
(iv) Suitability of pumps for the duty conditions and situation in general and specifically from efficiency aspects,<br><br />
(v) Suitability of ratings and sizes of motor, cable, transformer and other electrical appliances for the load.<br><br />
<br />
=== Study and Verification of Energy Consumption ===<br />
<br />
'''(a)All Pumps Similar (Identical)'''<br><br />
(i) Examine few electric bills in immediate past and calculate total number of days, total kWh consumed and average daily kWh (e.g. in an installation with 3 numbers working and 2 numbers standby if bill period is 61 days, total consumption 549,000 kWh, then average daily consumption shall be 9000 kWh),<br><br />
<br />
(ii) Examine log books of pumping operation for the subject period, calculate total pump - hours of individual pump sets, total pump hours over the period and average daily pump hours (Thus in the above example, pump hours of individual pump sets are: 1(839), 2(800), 3(700), 4(350) and 5(300) then as total hours are 2989 pump-hours, daily pump hours shall be 2989 ÷ 61 = 49 pump hours. Average daily operations are: 2 numbers of pumps working for 11 hours and 3 numbers of pumps working for 9 hours),<br><br />
<br />
(iii) From (i) and (ii) above, calculate mean system kW drawn per pump set (In the example, mean system power drawn per pump set = 9000 / 49 i.e. 183.67 kW),<br><br />
<br />
(iv) From (i), (ii) and (iii) above, calculate cumulative system kW for minimum and maximum number of pumps simultaneously operated. (In the example, cumulative system kW drawn for 2 numbers of pumps and 3 numbers of pumps operating shall be 183.67 x 2 = 367.34 kW and 183.67 x 3 = 551.01 kW, respectively),<br><br />
<br />
(v) Depending on efficiency of transformer at load factors corresponding to different cumulative kW, calculate output of transformer for loads of different combinations of pumps. (In the example, if transformer efficiencies are 0.97 and 0.975 for load factor corresponding to 367.34 kW and 551.01 kW, respectively, then outputs of transformer for the loads shall be 367.34 x 0.97 i.e. 356.32 kW and 551.01 x 0.975 i.e. 537.23 kW, respectively),<br><br />
<br />
(vi) The outputs of transformer, for all practical purpose can be considered as cumulative inputs to motors for the combinations of different numbers of pumps working simultaneously. Cable losses, being negligible, can be ignored,<br><br />
<br />
(vii) Cumulative input to motors divided by number of pump sets operating in the combination shall give average input to motor (In the example, average input to motor shall be 356.32 ÷ 2 i.e. 178.16 kW each for 2 pumps working and 537.23÷ 3 i.e. 179.09 kW each for 3 pumps working simultaneously),<br />
<br />
(viii) Depending on efficiency of motor at the load factor, calculate average input to the pump. (In the example, if motor efficiency is 0.86, average input to pump should be 178.16 x 0.86 i.e. 153.22 kW and 179.07 x 0.86 i.e. 154.0 kW),<br><br />
<br />
(ix) Simulate hydraulic conditions for combination of two numbers of pumps and three numbers of pumps operating simultaneously and take separate observations of suction head and delivery head by means of calibrated vacuum and pressure gauges and/or water level in sump/well by operating normal number of pumps i.e. 2 number and 3 numbers of pumps in this case and calculate total head on the pumps for each operating condition. The WL in the sump or well shall be maintained at normal mean water level calculated from observations recorded in log book during the chosen bill period,<br><br />
<br />
(x) Next operate each pump at the total head for each operating condition by throttling delivery valve and generating required head. Calculate average input to the pump for each operating condition by taking appropriate pump efficiency as per characteristic curves,<br />
<br />
(xi) If difference between average inputs to pumps as per (viii) and (x) for different working combinations are within 5% - 7%, the performance can be concluded as satisfactory and energy efficient,<br><br />
<br />
(xii) If the difference is beyond limit, detailed investigation for reduction in efficiency of the pump is necessary,<br><br />
<br />
(xiii) Full performance test for each pump shall be conducted as per procedure,<br><br />
<br />
(xiv) If for some reasons, the performance test is not undertaken, discharge test of each single pump at rated head generated by throttling delivery valve needs to be carried out,<br><br />
<br />
(xv) If actual discharge is within 4% - 6% of rated discharge, the results are deemed as satisfactory,<br><br />
<br />
(xvi) Test for efficiency of pumping machinery after each repairing shall be taken. If necessary inefficient machinery should be replaced by energy efficient / star rated machinery.<br><br />
<br />
'''(b)Dissimilar Pumps'''<br><br />
Procedures for energy audit for dissimilar pumps can be similar to that specified for identical pumps except for adjustment for different discharges as follows:<br><br />
(i) Maximum discharge pump may be considered as 1(one) pump-unit,<br><br />
(ii) Pump with lesser discharge can be considered as fraction pump-unit as ratio of its discharge to maximum discharge pump. (In the above example, if discharges of 3 pumps are 150, 150 and 100 litres per second, respectively, then number of pump-units shall be respectively 1, 1 and 0.667). Accordingly the number of pumps and pump-hours in various steps shall be considered as discussed for the case of all similar pumps.<br />
<br />
== Measures for Conservation of Energy ==<br />
<br />
Measures for conservation of energy in water pumping installation can be broadly classified as follows:<br />
<br />
'''(a) Routine Measures'''<br><br />
The measures can be routinely adopted in day to day operation and maintenance.<br />
<br />
'''(b) Periodical Measures'''<br><br />
Due to wear and encrustation during prolonged operation, volumetric efficiency and hydraulic efficiency of pumps reduce. By adopting these measures, efficiency can be nearly restored. These measures can be taken up during overhaul of pumps or planned special repairs.<br />
<br />
'''(c) Selection Aspects'''<br><br />
If during selection phase, the equipment i.e. pumps, piping, valves etc. are selected for optimum efficiency and diameter, considerable reduction in energy cost can be achieved.<br />
<br />
'''(d) Measures for System Improvement'''<br><br />
By improving system so as to reduce hydraulic losses or utilized available head hydraulic potentials, energy conservation can be achieved. Example is the use of rainwater harvesting through storages as supplementary to the main water supply system, saves lot of energy.<br />
<br />
=== Routine Measures ===<br />
<br />
'''(a) Improving Power Factor'''<br><br />
Generally as per guidelines of power supply authority, average power factor (PF) of more than 0.9 is to be maintained in electrical installations. The power factor can be improved to level of 0.97 or 0.98 without adverse effect on motors. Further discussion shows that considerable saving in power cost can be achieved if PF is improved. The low power factor may attract penalty by respective power supply authorities.<br />
<br />
'''(b) Operation of Working and Standby Transformers'''<br><br />
As regards operation of working and standby transformers, either of two practices as below is followed:<br />
(i) One transformer on full load and second transformer on no-load but, charged,<br />
(ii) Both transformers on part load.<br />
<br />
'''(c) Voltage Improvement by Voltage Stabilizer'''<br><br />
If motor is operated at low voltage, the current drawn increases, resulting in increased copper losses and consequent energy losses.<br />
<br />
'''(d) Reducing Static Head (Suction Side)'''<br><br />
A study shows that energy can be saved if operating head on any pump is reduced. This can be achieved by reducing static head on pumps at suction end or discharging end or both. One methodology to reduce static head on pumps installed on sump (not on well on river/ canal/lake source) is by maintaining WL at or marginally below FSL, say, between FSL to (FSL - 0.5 m) by operational control as discussed below.<br><br />
(i) Installation where inflow is directly by conduit from dam,<br><br />
(ii) In such installations, the WL in sump can be easily maintained at FSL or slightly below, say, FSL to (FSL - 0.5 m) by regulating valve on inlet to sump,<br><br />
(iii) Other installations.<br><br />
<br />
'''(e) Keeping Strainer or Foot Valve Clean and Silt Free'''<br><br />
Floating matters, debris, vegetation, plastics, gunny bags etc. in raw water clog the strainer or foot valve creating high head loss due to which the pump operates at much higher head and consequently discharge of the pump reduces. Such operation results in:<br><br />
(i) Operation at lower efficiency as operating point is changed. Thus, operation is energy wise inefficient,<br><br />
(ii) Discharge of the pump reduces. If the strainer/foot valve is considerably clogged, discharge can reduce to the extent of 50% or so,<br><br />
(iii) Due to very high head loss in strainer/foot valve which is on suction side of the pump.<br><br />
<br />
'''(f) Replacement of existing Mercury Vapour Lamps & Sodium Vapour Lamps by LED or solar lamps'''<br />
<br />
=== Periodic Measures ===<br />
<br />
'''(a) Restoring Wearing Ring Clearance'''<br><br />
Due to wear of wearing rings, the clearance between wearing ring increases causing considerable reduction in discharge and efficiency. Reduction in discharge up to 15-20% are observed in some cases. If wearing rings are replaced, the discharge improves to almost original value. Initial leakage through wearing rings is of the order of 1 to 2% of discharge of the pump. Due to operation, wearing rings wear out causing increase in clearance which increases leakage loss and results in consequent reduction in effective discharge of the pump. A study shows that even though discharge is reduced, power reduction is very marginal and as such the pump operates at lower efficiency. Reduction in discharge up to 15% to 20% is not uncommon. Thus the pumps have to be operated for more number of hours causing increase in energy cost.<br />
<br />
'''(b) Reducing Disk Friction Losses''' <br><br />
Disk friction losses in pump accounts for about 5% of power consumed by the pump. A study shows that if surfaces of the impeller and casing are rough, the disk friction losses increase. If casing is painted and impeller is polished, disk friction losses can be reduced by 20% to 40% of normal loss. Thus as disk friction loss is about 5% of power required by the pump, overall saving in power consumption will be 1% to 2%. For large pump the saving can be very high.<br />
<br />
'''(c) Scrapping down Encrustation inside Column Pipes'''<br><br />
Due to operation over prolonged period, encrustation or scaling inside the column pipe develops causing reduction in inside diameter and making surface rough. Both phenomenon cause increase in friction losses. If scrapping of encrustation is carried out whenever column pipes are dismantled energy losses can be minimized.<br />
<br />
=== Election Aspects ===<br />
'''(a) Selection of star rating motor pump'''<br><br />
Nowadays, three star/five star rating pump sets are available in the market, which can save 10-15% of power, can be used in place of normal pumping machinery.<br />
<br />
'''(b) Optimum Pump Efficiency'''<br><br />
Optimum efficiency of pump can be ensured by appropriate selection such that specific speed is optimum.<br />
<br />
'''(c) Optimisation of Pipe appurtenance'''<br><br />
Sluice Valve/Butterfly Valve and Non-Return Valve on Pump Delivery ‘K’ values of sluice valve and non-return valve are 0.35 and 2.50 respectively which amount to combined ‘K’ valve of 2.85. Due to very high ‘K’ value, head loss through these valves is significant and therefore, it is necessary to have optimum size of valves.<br />
<br />
'''(d) Delivery Pipe for Submersible Pump'''<br><br />
As delivery pipe for submersible pump is comparatively long and therefore, head loss in delivery pipe is considerable, it is of importance to select proper diameter. Optimum design velocity is around 1.1 - 1.5 m/s. However, pipe diameter should not be less than 50 mm.<br />
<br />
=== Concept for Energy Audit ===<br />
Energy Audit is a vital link in the entire management chain. The energy man¬ager, while proposing various courses of action and evaluating their conse¬quences, requires a detailed information base to work from energy audit at¬tempts to balance the total energy inputs with its use and serves to identify all the energy streams in the system and quantifies energy usages according to its discrete function.<br />
<br />
Energy audit is an effective tool in defining and pursuing comprehensive energy management programmes. It has positive approach aiming at continuous improvement in energy utilization in contrast to financial audit which stresses to maintain regularity. Energy audit provides answer to the question – what to do, where to start, at what cost and for what benefits? <br />
<br />
Energy audit helps in energy cost optimization, pollution control, safety aspects and suggests the methods to improve the operating and maintenance practices of the system. It is instrumental in coping with the situation of variation in energy cost availability, reliability of energy supply, decision on appropriate energy mix, decision on using improved energy conservation equipment, in¬strumentations and technology. It has been established that energy saving of the order of 15 to 30% is possible by optimizing use of energy by better housekeeping, low cost retrofitting measures and use of energy efficient equipment at the time of replacements. The developed countries' industry consumes more energy as com¬pared to the developing countries. The energy audit provides the vital information base for overall energy conser¬vation programme covering essentially energy utilization analysis and evalua¬tion of energy conservation measures.<br />
<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter_Ten:_Pumping_Machinery|Chapter Ten: Pumping Machinery]] << >> Next Page: [[Part_C|Part C: Operation and Maintenance of Water Treatment, Water and Wastewater Quality Compliance]]<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/Chapter_Ten:_Pumping_MachineryChapter Ten: Pumping Machinery2022-07-16T15:26:32Z<p>Juma: /* Maintenance */</p>
<hr />
<div><div style="text-align:justify"><br />
== Chapter Ten: Pumping Machinery ==<br />
=== General ===<br />
Pumping machinery and pumping stations are very important components in water supply and sanitation projects. Pumping machinery is subject to wear, tear, erosion and corrosion due to the nature of their functioning and therefore is vulnerable to failure. Generally, more numbers of failures or interruptions in water supply and sanitation projects are attributed to pumping machinery than any other component. Therefore, correct operation and timely maintenance and upkeep of pumping stations and pumping machinery are both of vital importance to ensure continued existence of uninterrupted water supply and sanitation services. Sudden failures can be avoided by timely inspection, follow up actions during observations of inspection and planned periodic maintenance. Downtime can be reduced by maintaining an inventory of the fast moving spare parts. Efficiency of pumping machinery decreases due to normal wear and tear. Timely action for restoration of efficiency can keep energy bills within a reasonable optimum limit. In case there is no standby pump provision, suitable water pumps with identical duty shall be provided as 100% standby in case of a single pump set and two or more pumps with a minimum of 50% standby along with all necessary accessories like cables, control panels, safety equipment, valves and fittings. Providing a minimum of 50% standby pump set will help in operating the schemes in initial stages until stabilization is achieved.<br />
<br />
In case of depletion of sources during dry season or rains failure, the design engineer should ensure that schemes can be operated partially without throttling of pumps. While replacement of motors/ pumps is done, it must be insisted to provide star rated motors to have energy savings. Generally, as the pumps are scheme specific, (i.e. discharge & head fixed depending upon the requirements), the question of standardization with regard to minimizing the inventory does not arise. To ensure better performance/effective cost savings, energy audit and water and sanitation audit needs to be done for every project.<br />
<br />
Annual monitoring of handed over projects must be done by the department that implemented the projects. Proper record keeping is also very important. A log book should be maintained covering the following items:<br />
<br />
(a) Timings when the pumps are started, operated and stopped during 24 hours,<br />
<br />
(b) Voltage in all three phases,<br />
<br />
(c) Current drawn by each pump-motor set and total current drawn at the installation,<br />
<br />
(d) Frequency,<br />
<br />
(e) Readings of vacuum and pressure gauges,<br />
<br />
(f) Motor winding temperature,<br />
<br />
(g) Bearing temperature for pump and motor,<br />
<br />
(h) Water level in intake/sump,<br />
<br />
(i) Flow meter reading,<br />
<br />
(j) Daily Power factor over 24 hours duration, and<br />
<br />
(k) Any specific problem or event in the pumping installation or pumping system (e.g. burst in pipeline, tripping or fault, power failure).<br />
<br />
=== Components of a Pumping Station ===<br />
The components of a pumping station can be grouped into three groups as follows:<br />
<br />
(a) '''Pumping machinery'''<br />
<br />
Pumps and other mechanical equipment, i.e. valves, pipe works, vacuum pumps, motors, switchgears, cables, transformers and other electrical accessories.<br />
<br />
(b) '''Ancillary Equipment'''<br />
<br />
(i) Lifting equipment,<br />
<br />
(ii) Water hammer control device,<br />
<br />
(iii) Flow meters,<br />
<br />
(iv) Diesel generating set.<br />
<br />
(c) '''Pumping stations'''<br />
<br />
(i) Sump/intake/well/tube well/borehole,<br />
<br />
(ii) Pump house,<br />
<br />
(iii) Screens,<br />
<br />
(iv) Penstock/gate.<br />
<br />
==== Type of Pumps ====<br />
The following types of pumps are used in water supply and sanitation systems:<br />
<br />
(a) Centrifugal pumps,<br />
<br />
(b) Vertical turbine pumps,<br />
<br />
(c) Oil lubricated,<br />
<br />
(d) Self-water (pumped water) lubricated,<br />
<br />
(e) Clear water lubricated,<br />
<br />
(f) Submersible pumps,<br />
<br />
(g) Vertical bore well type pump-motor set,<br />
<br />
(h) Mono bloc open well type pump-motor set,<br />
<br />
(i) Jet pumps,<br />
<br />
(j) Reciprocating pumps.<br />
<br />
==== Important Points for Operation of the Pumps ====<br />
Various types of pumps are in use and the specification of O&M schedule provided by the manufacturers shall be followed. However, the following points shall be observed while operating the pumps:<br />
<br />
(a) Dry running of the pumps should be avoided,<br />
<br />
(b) Centrifugal pumps have to be primed before starting,<br />
<br />
(c) Pumps should be operated only within the recommended range of the head-discharge (duty) characteristics of the pump,<br />
<br />
(d) If a pump is operated at a point away from the designated duty point, the pump efficiency normally reduces,<br />
<br />
(e) Operation near the shut off point should be avoided, as the operation near the shut off causes substantial recirculation within the pump, resulting in overheating of water in the casing and consequently, overheating of the pump,<br />
<br />
(f) Voltage during operation of pump-motor set should be within ± 10% of the rated voltage. Similarly, current should be below the rated current as per specification of the name plate on the motor,<br />
<br />
(g) Whether the delivery valve should be opened or closed at the time of starting should be decided by examining the shape of the power-discharge characteristics of the pump. Pumps of low and medium specific speeds draw lesser power at shut off head and power required increases from shut off to a normal operating point. Hence in order to reduce the starting load on the motor, a pump of low or medium specific speed is started against closed delivery valve. Normally the pumps used in water supply schemes are of low or medium specific speeds. Hence, such pumps need to be started against closed delivery valves. The pumps of high specific speed draw more power at shut off. Such pumps should be started with the delivery valves open,<br />
<br />
(h) The delivery valve should be operated gradually to avoid sudden change in flow velocity which can cause water hammer pressures. It is also necessary to control the opening of the delivery valves during pipeline - filling period so that the head on the pump is within its operating range to avoid operation on low head and consequent overloading. This is particularly important during charging of the pumping mains initially or after shutdown. As the head increases, the valve shall be gradually opened,<br />
<br />
(i) When the pumps are to be operated in parallel, the pumps should be started and stopped with a time lag between the two pumps to restrict change of flow velocity to a minimum and to restrict the dip in voltage in the incoming feeder. The time lag should be adequate to allow stabilizing the head on the pump, as indicated by a pressure gauge,<br />
<br />
(j) When the pumps are to be operated in series, they should be started and stopped sequentially, but with minimum time lag. Any pump, next in sequence should be started immediately after the delivery valve of the previous pump is even partly opened. Due care should be taken to keep the air vent of the pump next in sequence open, before starting that pump,<br />
<br />
(k) The stuffing box should let a drip of leakage to ensure that no air is passing into the pump and that the packing is getting adequate water for cooling and lubrication. When the stuffing box is grease sealed, adequate refill of the grease should be maintained,<br />
<br />
(l) The running of the duty pumps and the standby one should be scheduled carefully so that no pump remains idle for a long period and all pumps are in ready-to run condition. Similarly, unequal running should be ensured so that all pumps do not wear equally and become due for overhaul simultaneously. If any undue vibration or noise is noticed, the pump should be stopped immediately and causes of the vibration or noise be checked and rectified,<br />
<br />
(m) By-pass valves of all reflux valves, sluice valves and butterfly valves shall be kept in the closed position during normal operation of the pumps,<br />
<br />
(n) Frequent starting and stopping should be avoided because, each start causes overloading of the motor, starter and contactors. Though overloading lasts for a few seconds, it reduces the lifetime of the equipment.<br />
<br />
===== Undesirable Operations =====<br />
The following undesirable operations should be avoided:<br />
<br />
(a) Operation at Higher Head-The pump should never be operated at a head higher than the maximum recommended. Such operation results in excessive recirculation in the pump, overheating of the water and the pump. Another problem, which arises if a pump is operated at a head higher than the recommended maximum head, is that the radial reaction on the pump shaft than the recommended maximum head, is that the radial reaction on the pump shaft increases causing excessive unbalanced forces on the shaft which may cause failure of the pump shaft. As a useful guide, appropriate marking on pressure gauge be made. Such operation is also inefficient as pump efficiency at higher head is normally low,<br />
<br />
(b) Operation at Lower Head-If pump is operated at lower head than recommended minimum head, radial reaction on the pump shaft increases causing excessive unbalanced forces on the shaft which may cause failure of the pump shaft. As a useful guide, appropriate markings on both the pressure gauge and the ammeter should be made. Such operation is also inefficient as efficiency at lower heads is normally low,<br />
<br />
(c) Operation on higher suction lift. If a pump is operated on a higher suction lift than the permissible value, pressure at the eye of the impeller and the suction side falls below the vapour pressure. This results in convention of water into vapour. These vapour bubbles during passage collapse resulting in cavitation if the pump, pitting on the suction side of the impeller and casing as well as excessive vibrations. In addition to mechanical damage due to pitting, discharge of the pump also reduces drastically,<br />
<br />
(d) Throttled operation-At times if the motor is continuously overloaded, the delivery valve is throttled to increase the head on the pump and to reduce power drawn from the motor. Such operation results in inefficient running as energy is wasted in throttling. In such cases, it is preferable to reduce the diameter of the impeller which will reduce the power drawn from the motor. Installation of variable voltage & variable frequency (VVVF) drive as a remedial measure is recommended,<br />
<br />
(e) Operation with strainer/foot valve clogged-If the strainer or foot valve is clogged, the friction loss in the strainer increases to high magnitudes which may result in pressure at the eye of the impeller falling below water vapour pressure, causing cavitation and pitting similar to operation at a higher suction lift. The strainers and foot valves should be periodically cleaned, particularly during the rainy season,<br />
<br />
(f) Operation with occurrence of Vortices-If vibration continues even after taking all precautions, vortex may be the cause. All parameters necessary for ensuring vortex-free operation should be checked.<br />
<br />
===== Starting the Pumps =====<br />
The following points should be checked before starting the pump:<br />
<br />
(a) Power is available in all 3 phases,<br />
<br />
(b) All connections are properly thimbled,<br />
<br />
(c) Trip circuit for relays is in a healthy state, <br />
<br />
(d) Check voltage in all 3 phases,<br />
<br />
(e) The voltage in all phases should be almost the same and within ± 10% of the rated voltage, as per permissible voltage variation,<br />
<br />
(f) Check functioning of the lubrication system specifically for oil lubricated and clear water lubricated vertical turbine pumps and oil lubricated bearings,<br />
<br />
(g) Check stuffing box to ensure that it is packed properly,<br />
<br />
(h) Check and ensure that the pump is free to rotate,<br />
<br />
(i) Check over current setting if the pump is not operated for a week or longer periods,<br />
<br />
(j) Before starting, it shall be ensured that the water level in the sump/intake is above the low water level and inflow from the source or preceding pumping station is adequate.<br />
<br />
===== Stopping the Pump =====<br />
'''(a) Stopping the Pump under Normal Condition'''<br />
<br />
Steps to be followed for stopping a pump of low or medium specific speed are as follows:<br />
<br />
(i) Close the delivery valve gradually (sudden or fast closing should not be resorted to which can give rise to water hammer pressures),<br />
<br />
(ii) Switch off the motor,<br />
<br />
(iii) Open the air vent in case of Vertical Turbine (VT) and submersible pump,<br />
<br />
(iv) Stop lubricating oil or clear water supply in case of oil lubricated or clear water lubricated VT pump as applicable.<br />
<br />
'''(b) Stopping after Power Failure/Tripping'''<br />
<br />
If power supply to the pumping station fails or trips, actions stated below should be immediately taken to ensure that the pumps do not restart automatically on resumption of power supply. Though no-volt release or under volt relay is provided in the starter and the circuit breaker, possibility of its malfunctioning and failure to open the circuit cannot be ruled out. In such eventuality, if the pumps starts automatically on resumption of power supply, there will be sudden increase in flow velocity in the pumping main causing sudden rise in pressure due to the water hammer which may prove disastrous to the pumping main. Secondly, due to sudden acceleration of flow in the pumping main from no-flow situation, acceleration head will be very high and the pumps shall operate near the shut off region during the acceleration period which may last for a few minutes for long pumping mains and cause overheating of the pump. Restarting of all pumps simultaneously shall also cause overloading of the electrical system. Hence, precautions are necessary to prevent auto-restarting on resumption of power.<br />
<br />
Following procedure should be followed:<br />
<br />
(i) Close all delivery valves on delivery piping of the pumps if necessary, manually as actuators cannot be operated due to non-availability of power,<br />
<br />
(ii) Check and ensure that all circuit breakers and starters are in the open condition i.e. off-position,<br />
<br />
(iii) All switches and circuit breakers shall be operated to open i.e. off-position,<br />
<br />
(iv) Open the air vent in case of a vertical turbine or submersible pump and close the lubricating oil or clear water supply in case of oil lubricated or clear water lubricated vertical turbine pump. Information about power failure should be given to all concerned, particularly to the upstream pumping stations to stop pumping so as to prevent overflow.<br />
<br />
=== Pumping Machinery Maintenance ===<br />
'''(a) Daily'''<br />
<br />
• Clean the pump, motor and other accessories,<br />
<br />
• Check coupling bushes/rubber spider,<br />
<br />
• Check stuffing box, gland, etc.<br />
<br />
<br />
'''(i) Routine observations of irregularities'''<br />
<br />
The pump operator should be watchful and should take appropriate action on any irregularity noticed in the operation of the pumps. Particular attention should be paid to following irregularities:<br />
<br />
• Changes in the sound of a running pump and motor,<br />
<br />
• Abrupt changes in bearing temperature,<br />
<br />
• Oil leakage from the bearings,<br />
<br />
• Leakage from the stuffing box or mechanical seal,<br />
<br />
• Changes in voltage,<br />
<br />
• Changes in current,<br />
<br />
• Changes in vacuum gauge and pressure gauge readings,<br />
<br />
• Sparks or leakage current in motor, starter, switch-gears, cable, etc.,<br />
<br />
• Overheating of the motor, starter, switch gear, cable, etc.<br />
<br />
<br />
'''(ii) Record of operations and observations'''<br />
<br />
A log book should be maintained to record the observations, which should cover the following items:<br />
<br />
• Timings when the pumps are started, operated and stopped during 24 hours,<br />
<br />
• Voltage in all three phases,<br />
<br />
• Current drawn by each pump-motor set and total current drawn at the installation,<br />
<br />
• Frequency,<br />
<br />
• Readings of vacuum and pressure gauges,<br />
<br />
• Motor winding temperature,<br />
<br />
• Bearing temperature for the pump(s) and motors,<br />
<br />
• Water level in the intake/sump,<br />
<br />
• Flow meter reading,<br />
<br />
• Daily Power Factor (PF) over 24 hour’s duration,<br />
<br />
• Any specific problem or event in the pumping installation or pumping system (e.g. burst in pipeline, tripping or fault, power failure),<br />
<br />
<br />
'''(b) Monthly Maintenance'''<br />
<br />
(i) Check free movement of the gland of the stuffing box; check gland packing and replace if necessary. Clean and apply oil to the gland bolts.<br />
<br />
(ii) Inspect the mechanical seal for wear and replacement if necessary. Check condition of bearing oil and replace or top up if necessary.<br />
<br />
<br />
'''(c) Quarterly Maintenance'''<br />
<br />
(i) Check alignment of the pump and the drive. The pump and motor shall be decoupled while correcting alignment, and both the pump and motor shafts shall be pushed to either side to eliminate effect of end play in bearings.<br />
<br />
(ii) Clean oil lubricated bearings and replenish with fresh oil. If bearings are grease lubricated, the condition of the grease should be checked and replaced/replenished to the correct quantity. An anti-friction bearing should have its housing so packed with grease that the void space in the bearing housing should be between one third to half. A fully packed housing will overheat the bearings and will result in reduction of life of the bearings.<br />
<br />
(iii) Tighten the foundation bolts and holding down bolts of the pump and motor mounting on the base plate or frame.<br />
<br />
(iv) Check vibration level with instruments if available; otherwise by observation.<br />
<br />
(v) Clean flow indicator, other instruments and appurtenances in the pump house.<br />
<br />
<br />
'''(d) Annual Inspections and Maintenance'''<br />
<br />
A very thorough, critical inspection and maintenance should be performed by trained operators/engineers once in a year. Following items should be specifically attended:<br />
<br />
(i) Clean and flush bearings with kerosene and examine for flaws that may have developed if any, e.g. corrosion, wear and scratches. Check end play. Immediately after cleaning, the bearings should be coated with oil or grease to prevent ingress of dirt or moisture,<br />
<br />
(ii) Clean bearing housing and examine for flaws, e.g. wear, grooving etc. Change oil or grease in the bearing housing,<br />
<br />
(iii) Examine shaft sleeves for wear or scour and necessary rectifications. If shaft sleeves are not used, shaft at gland packing’s should be examined for wear,<br />
<br />
(iv) Check stuffing box, glands, lantern ring, and mechanical seal and rectify if necessary,<br />
<br />
(v) Check clearances in the wearing ring,<br />
<br />
(vi) Check impeller hubs and vane tips for any pitting or erosion,<br />
<br />
(vii) Check interior of volute, casing and diffuser for pitting, erosion, and rough surface,<br />
<br />
(viii) All vital instruments i.e. pressure gauge, vacuum gauge, ammeter, voltmeter,<br />
<br />
(ix) Undertake performance test of the pump for discharge, head efficiency.<br />
<br />
==== Maintenance Schedule for Motors ====<br />
'''(a) Daily'''<br />
<br />
(i) Clean the external surface of the motor,<br />
<br />
(ii) Examine earth connections and motor leads,<br />
<br />
(iii) Check temperature of the motor and check whether overheated. The permissible maximum temperature is above the level which can be comfortably felt by hand. Hence, temperature observation should be taken with a Resistance Temperature Detector (RTD) or a thermometer. (Note: In order to avoid opening up motors, a good practice is to observe the stator temperature under normal working conditions. Any increase not accounted for, by seasonal increase in ambient temperature, should be suspected),<br />
<br />
(iv) In case of oil ring lubricated bearings,<br />
<br />
(v) Examine bearings to check whether oil rings are working,<br />
<br />
(vi) Note bearing temperature,<br />
<br />
(vii) Add oil if necessary,<br />
<br />
(viii) Check for any abnormal bearing noise,<br />
<br />
(ix) Note pump vibration if any.<br />
<br />
<br />
'''(b) Monthly'''<br />
<br />
(i) Check belt tension. In case where this is excessive it should immediately be reduced,<br />
<br />
(ii) Blow dust from the motor,<br />
<br />
(iii) Examine oil in oil lubricated bearings for contamination by dust, grit. (This can be judged from the colour of the oil),<br />
<br />
(iv) Check functioning and connections of anti-condensation heater (space heater),<br />
<br />
(v) Check insulation resistance.<br />
<br />
<br />
'''(c) Quarterly'''<br />
<br />
(i) Clean oil lubricated bearings and replenishes fresh oil. If bearings are grease lubricated, the condition of the grease should be checked and replaced/replenished to correct quantity,<br />
<br />
(ii) Anti-friction bearings should have its housing so packed with grease that the void space in the bearing housing should be between one third to half. A fully packed housing will overheat the bearing and will result in reduction of life of the bearing,<br />
<br />
(iii) Wipe brush holders and check contact faces of brushes of slip-ring motors. If contact face is not smooth or is irregular, file it for proper and full contact over slip rings,<br />
<br />
(iv) Check the insulation resistance of the motor,<br />
<br />
(v) Check tightness of the cable gland, lug and connecting bolts,<br />
<br />
(vi) Check and tighten foundation bolts and holding down bolts between motor and the frame,<br />
<br />
(vii) Check vibration level with instrument if available; otherwise by observation.<br />
<br />
<br />
'''(d) Half Yearly'''<br />
<br />
(i) Clean winding of the motor, bake and varnish if necessary,<br />
<br />
(ii) In case of slip ring motors, check slip-rings for grooving or unusual wear, and polish with smooth polish paper if necessary.<br />
<br />
<br />
'''(e) Annual Inspections and Maintenance'''<br />
<br />
(i) Clean and flush bearings with kerosene and examine for flaws that may have developed, if any, e.g. wear and scratches. Check end-play. Immediately after cleaning, the bearings should be coated with oil or grease to prevent ingress of dirt or moisture,<br />
<br />
(ii) Clean bearing housing and examine for flaws, e.g. wear, grooving etc. Change oil or grease in bearing housing,<br />
<br />
(iii) Blow out dust from the windings of motors thoroughly with clean dry air. Make sure that the pressure is not so high as to damage the insulation,<br />
<br />
(iv) Clean and varnish dirty and oily windings. Re-varnish motors subjected to severe operating and environmental conditions e.g., operation in dust-laden environment, polluted atmosphere, etc.,<br />
<br />
(v) Check condition of the stator, stamping, insulation, terminal box, fan, etc.,<br />
<br />
(vi) Check insulation resistance to earth and between phases of motor windings, control gear and wiring,<br />
<br />
(vii) Check air gaps,<br />
<br />
(viii) Check resistance of earth connections.<br />
<br />
==== History Sheet ====<br />
Similar to the history sheet of the pump, history sheet of the motor should be maintained. The history sheet should contain all important particulars, records of periodic maintenance, repairs, inspections and tests. It shall generally include the following:<br />
<br />
(a) Details of motor, rating, model, class of duty, class of insulation, efficiency curve, type test result and type test certificate, etc.,<br />
<br />
(b) Date of installation and commissioning,<br />
<br />
(c) Addresses of manufacturer & dealer with phone & fax number and e-mail addresses,<br />
<br />
(d) Brief details of monthly, quarterly, half yearly and annual maintenance and observations of inspections about insulation level, air gap, etc.,<br />
<br />
(e) Details of breakdown, repairs with fault diagnosis,<br />
<br />
(f) Running hours at the time of any major repairs.<br />
<br />
==== Low Voltage Starters, Circuit Breakers and Panel ====<br />
Note: Circuit diagram of the starter/breaker should be pasted on the door of the switch gear and additional copy should be kept on record.<br />
<br />
'''(a) Daily'''<br />
<br />
(i) Clean the external surface,<br />
<br />
(ii) Check for any spark or leakage current,<br />
<br />
(iii) Check for overheating.<br />
<br />
<br />
'''(b) Monthly'''<br />
<br />
(i) Blow the dust and clean internal components in the panel, and breaker,<br />
<br />
(ii) Check and tighten all connections of cables, wires, jumpers and bus-bars. All carbon deposits shall be cleaned,<br />
<br />
(iii) Check relay setting.<br />
<br />
<br />
'''(c) Quarterly'''<br />
<br />
(i) Check all connections as per circuit diagram,<br />
<br />
(ii) Check fixed and moving contacts and clean with smooth polish paper, if necessary,<br />
<br />
(iii) Check oil level and condition of oil in the oil tank. Replace the oil if carbon deposit in suspension is observed or the colour is black,<br />
<br />
(iv) Check insulation resistances,<br />
<br />
(v) Check conditions of insulators.<br />
<br />
<br />
'''(d) Yearly'''<br />
<br />
(i) Check and carry out servicing of all components, thoroughly clean and reassemble,<br />
(ii) Calibrate voltmeter, ammeter, frequency meter, etc.<br />
<br />
==== High voltage Breakers Contactors and Protection relays ====<br />
<br />
Note: Circuit diagram of the breaker/relay circuit should be pasted on the door of switch gear and additional copy should be kept on record. Maintenance schedule specified for Low voltage breakers are also applicable to High voltage breakers and contactors. In addition, the following important points shall be attended for High voltage breakers and contactors.<br />
<br />
'''(a) Monthly<br>'''<br />
(i) Check spring charging mechanism and manual cranking arrangement for operation,<br><br />
(ii) Clean all exposed insulators,<br><br />
(iii) Check trip circuit and alarm circuit,<br><br />
(iv) Check opening & closing timing of the breaker.<br />
<br />
'''(b) Quarterly<br>'''<br />
(i) Check control circuits including connections in marshalling boxes of breakers and the transformer,<br><br />
(ii) Check oil level in Minimum/Low Oil Circuit Breaker (M/LOCB)/High Voltage Oil Circuit Breaker (HV.OCB) and top up with tested oil,<br><br />
(iii) Yearly / Two yearly testing of protection relay with Direct Current (D.C) injection shall be carried out once in year,<br><br />
(iv) Servicing of High voltage breaker and contactor shall be carried out once in 2-3 years,<br><br />
(v) Check dielectric strength of oil in the breaker and replace if necessary,<br><br />
(vi) Check male & female contacts for any pitting and measure contact resistance.<br />
<br />
<br />
==== Transformer and Transformer Substation ====<br />
<br />
Maintenance schedule as follows shall be applicable for transformer and sub-station equipment e.g. lightning arrestor, Air Break (AB) switch, Drop Off (DO) or horn gap fuse, sub-station earthing system. This section is particularly useful for the large schemes. Instructions of district/region/zone electricity department and chief electrical inspector shall be followed.<br />
<br />
(a) '''Daily Observations and Maintenance<br>'''<br />
(i) Check winding temperature and oil temperature in the transformer and record. (For large transformers above 1000 kV, the temperature should be recorded hourly),<br><br />
(ii) Check leakages through current/potential transformer unit, transformer tank and High/Low voltage bushings,<br><br />
(iii) Check colour of silica gel. If silica gel is of pink colour, change the same by spare charge and reactivate old charge for re-use.<br />
<br />
(b) '''Monthly<br>'''<br />
(i) Check oil level in the transformer tank and top up if required,<br><br />
(ii) Check relay contacts, cable termination, connections in marshalling box,<br><br />
(iii) Check operation of AB switch and DO fuse assembly,<br><br />
(iv) Clean radiators free from dust and scales,<br><br />
(v) Pour 3-4 buckets (6 to 8 buckets in hot season) of water in earth pit. Watering shall be increased to once in a week in hot seasons. Watering shall be increased to once in a week in hot seasons. Shall preferably contain small amounts of salt in solution,<br><br />
(vi) Inspect lightning arrestor and High/Low voltage bushing for cracks and dirt.<br />
<br />
(c) '''Quarterly<br>'''<br />
(i) Check dielectric strength of transformer oil and change or filter if necessary.<br><br />
(ii) Check insulation resistance of all equipment in the sub-station, continuity of earthings and earth leads,<br><br />
(iii) Check operation of tap changing switches.<br />
<br />
<br />
==== Pre-rain and Post-rain Checks and Maintenance ====<br />
<br />
* Check insulation resistance of the transformer,<br><br />
* Test transformer oil for dielectric strength, sludge etc. If necessary, filtration of oil shall be carried out before the rainy season,<br><br />
* Oil shall be tested for dielectric strength after rainy season.<br />
<br />
(a) '''Half-Yearly<br>'''<br />
(i) Check dielectric strength of transformer oil in current/potential transformer and filter or change oil if necessary,<br><br />
(ii) Check contact faces of Air Break (AB) switch and Drop Out/Horn Gap fuse; apply petroleum jelly or grease to moving components of AB switch.<br />
<br />
(b) '''Annual<br>'''<br />
(i) Measure resistance of earth pit. Resistance shall not exceed 1 ohm,<br><br />
(ii) Check bus bar connections, clean contact faces, change rusted nut bolts,<br><br />
(iii) Calibrate the protection relay for functioning. Check relay setting and correct if necessary,<br><br />
(iv) Ensure that the sub-station area is not water-logged. If required, necessary earth fillings with metal spreading at the top shall be carried out once in a year. Check drainage arrangement to prevent water logging in sub-station area and cable trenches,<br><br />
(v) Test transformer oil for acidity test.<br />
<br />
(c) '''Special Maintenance<br>'''<br />
(i) Painting of transformer tank and steel structure of the sub-station equipment shall be carried out after every two years,<br><br />
(ii) The core of the transformer and winding shall be checked after 5 years for the transformer up to 3,000 kVA and after 7–10 years for transformers of higher capacity.<br />
<br />
<br />
=== Operation and Maintenance Activities of Selected Pumps === <br />
<br />
==== Submersible Pumps ==== <br />
<br />
The operation and maintenance of submersible pumps are given below in Appendix 5 illustrates the details of troubleshooting for these pumps.<br />
<br />
===== Operations =====<br />
<br />
===== Inspection procedure for key Components =====<br />
<br />
* Submersible pumps may be operated manually with a switch located above ground level or automatically with a pressure switch, electrodes or float control devices, <br><br />
* Submersible pumps should always be operated below the water level, <br><br />
* The pump should be installed higher than the well screen to prevent pump break suction which my lead to a burned pump motor.<br />
<br />
'''Inspection procedure for key Components'''<br />
<br />
The installation of a new pump brings with it the expectation that it will operate consistently. Most operators are content with starting a pump and observing it run, like that is enough to see that the pump is operational. It is very vital to inspect the pump immediately on start-up, and also to do frequent inspections on it. Inspections assist in picking up faults early, when they occur before they become catastrophic. Routine preventive maintenance inspections can help address possible issues before they become major (or even catastrophic) events.<br />
<br />
In most cases, four major components should be inspected in submersible pumps:<br><br />
• Alarm monitoring,<br><br />
• Pressure flow checks,<br><br />
• Visual Inspection:<br><br />
o Inspect for clogging debris on suction inlet,<br><br />
o Check pump exterior for dents, corrosion and abrasion,<br><br />
o Clean off.<br><br />
• Corrosion:<br><br />
Inspect valve threads. <br />
<br />
<br />
Below is an inspection checklist for submersible borehole pumps:<br><br />
• Check electrical condition of insulation on power cable(s) and on all phases of the motor,<br><br />
• Check for any loose or faulty electrical connections within the control panel,<br><br />
• Measure resistance between stator windings (in ohms),<br><br />
• Check voltage supply between all phases of the electrical control panel,<br><br />
• Check voltage balance (Vac) between all phases on the load side of the pump / mixer control panel with pump / mixer running,<br><br />
• Check amperage draw on all phases of the motor (in amps),<br><br />
• Check condition and operation of the motor thermal protection control system (if equipped),<br><br />
• Remove pump / mixer from the lift station for physical inspection,<br><br />
• Check condition of upper and lower shaft seals (inspect condition of motor / stator housing, if applicable),<br><br />
• Check condition and operation of leakage and bearing sensors (if equipped),<br><br />
• Check for worn out or loose impeller or propeller,<br><br />
• Check impeller wear rings (rotating & stationary),<br><br />
• Check for any unusual noise in the upper and lower bearings,<br><br />
• Clean, reset and check operation of the level control system (if equipped),<br><br />
• Check for physical damage of power and control cables,<br><br />
• Check for correct shaft rotation,<br><br />
• Check operation of valves and the associated equipment.<br />
<br />
<br />
Table 10.1 summarizes the common problems of submersible pumps and their remedies.<br />
<br />
'''Table 10. 1: Common Troubleshooting for Submersible Pumps'''<br />
<br><br />
[[File:Table_new1.PNG|700px|center]]<br />
<br><br />
<br />
===== Maintenance and Repair =====<br />
<br />
To begin a maintenance job analysis, the assigned person needs the following information:<br />
<br />
(a) Pump motor unit size and type;<br><br />
(b) Static and pumping water level of the well;<br><br />
(c) Size of drop pipe and/or drop cable;<br><br />
(d) Pump setting;<br><br />
(e) Discharge pressure required;<br><br />
(f) Capacity pumped;<br><br />
(g) Line voltage; and<br><br />
(h) Operating Manual.<br />
<br />
==== Centrifugal Pumps ====<br />
<br />
===== Operations =====<br />
To operate a centrifugal pump, certain procedures need to be followed, which are found in the manual supplied by the manufacturer. They generally involve the steps outlined below:<br />
<br />
===== Steps in Operating the Centrifugal Pumps =====<br />
<br />
(a) Before starting the motor, make sure that the discharge gate valve is closed;<br><br />
(b) If the pump is not self-priming or has defective suction line or foot valve, add priming water. Priming displaces the air in the suction line or drop pipe of the pump with water;<br><br />
(c) Allow the pressure to build up, and then slowly open the discharge valve. Doing this slowly avoids water hammer, which could destroy the pipes and valves;<br><br />
(d) Start the pump motor;<br><br />
(e) After the pressure has built up, slowly open the discharge gate valve. In case the pump has been primed with water, waste the water pumped during the first 1-2 minutes by opening the drain valve;<br><br />
(f) Make a routine check for faults in the operation of the system (abnormal noise, vibration, heat, and odour).<br />
<br />
===== Maintenance and Repair =====<br />
Bearings, gears and other pump moving parts should be lubricated on a regular schedule, using the lubricants recommended by the supplier. The following are specific actions to remedy centrifugal pump problems:<br />
<br />
(a) '''Low Pump Efficiency'''<br><br />
If the pump performance tests reveal that the pump is operating at significantly lowered efficiencies, the pump should be pulled out, inspected and repaired or reconditioned. This work is best referred for servicing to the manufacturer or a pump repair specialist.<br />
<br />
(b) '''Packing Adjustment'''<br><br />
The water flowing through the stuffing box should be maintained at a level just enough to prevent overheating. The gland nuts should be loosened or tightened one-quarter turn only to allow the packing to equalize against the pressure.<br />
<br />
(c) '''Checking and Adjusting Misaligned Head Shaft'''<br><br />
Pump vibrations could indicate a misalignment of the head shaft. This can be checked by the following procedure:<br><br />
(i) Remove the motor dust cover, motor head nut and key, and take out the motor drive flange.<br><br />
(ii) Check if the head shaft is concentric with the motor hollow shaft bore.<br><br />
(iii) If needed, adjust by using shims.<br />
<br />
Other common problems and their remedies are summarized in Appendix 6.<br />
<br />
==== Jet pumps ====<br />
<br />
===== Operations =====<br />
<br />
Jet pumps can be operated manually or automatically with a pressure switch, electrodes or a float control switch.<br />
<br />
===== Operating the Non-Self-Priming Jet Pump =====<br />
(a) Initially inspect the assembly. Make sure that the power supply to the motor is off;<br><br />
(b) Check lubrication. Make sure that the pump rotates fully by manually turning the shaft. (For more details, refer to the pump manual);<br><br />
(c) Remove pressure gauge bushing and prime pump with clean water. Never start the motor until the pump has been filled with water;<br><br />
(d) Replace pressure gauge bushing and close the discharge gate valve;<br><br />
(e) Start the pump motor. Note build-up of pressure in the pressure gauge. Open the discharge valve slowly;<br><br />
(f) If discharge pressure is lost and fails to build up again after a short time, the system still contains air. Stop the pump motor and repeat operating procedures starting from item #3. It may be necessary to repeat the procedure several times until the system is completely filled with water.<br />
<br />
===== Operating the Self-Priming Pump =====<br />
Routinely inspect the assembly. Make sure power supply to motor is off.<br />
<br />
===== Maintenance of Jet Pumps =====<br />
The manufacturer or equipment supplier always provides the client with the Operation and Maintenance manual upon purchase of their product. Refer to this manual for the proper operation and maintenance of the pump. The matrix for centrifugal pumps may be also used as a guide for troubleshooting operational problems of jet pumps. Additional troubleshooting information for jet pump problems is presented in Appendix 7.<br />
<br />
==== Vertical Turbine Pumps ====<br />
<br />
(a) Pumps should be properly primed before starting,<br><br />
(b) Air vent to be fully opened before starting,<br><br />
(c) Correct rotation of the pump,<br><br />
(d) Pump should not be operated, if ratchet pins are missing,<br><br />
(e) Bowl assembly is completely submerged.<br />
<br />
===== Inventory of Materials for Submersible, Centrifugal and Vertical Turbine Pumps =====<br />
<br />
The following is the list of fast moving materials for Submersible, Centrifugal, and Vertical Turbine Pumps:<br><br />
(a) Submersible pumps: Impellers<br><br />
(b) Centrifugal pumps: Impellers, diffusers, bearings, gland packing’s<br><br />
(c) Vertical turbine pumps: thrust bearings, gland packing, head shaft, intermediate shaft, bearing spider, bowl assemble, impeller.<br><br />
(d) Motors: Bearings<br><br />
(e) Moulded Case Circuit Breaker (MCCB), Relay, tripping circuit, fuses.<br><br />
(f) Transformer: Oil<br />
<br />
==== Hand Pumps ====<br />
Figures 10.1 illustrate the typical types of hand pumps. The maintenance of a hand pump is identified in two categories.<br />
<br />
<br />
===== Minor Repairs =====<br />
The repairing of hand pump which does not require lifting of hand pump assembly is treated as minor repair. The minor repairs of a hand pump may be made by a semi-skilled care taker/CBWSOs). This type of repairing involves replacement of handle nut & bolts, repairing of chain, bearing. Appendix 8 illustrates the troubleshooting of Hand pumps.<br />
<br />
<br />
===== Major Repair =====<br />
The repairing of a hand pump which involves pulling out and cleaning of the hand pump assembly is treated as a major repair; this type of repairing can be carried out by hand pump specialist from RUWASA or the water supply and sanitation utility.<br />
<br />
The daily, monthly and annual activities should include the following O&M activities:<br />
<br />
(a) '''Weekly'''<br><br />
(i) Check the fittings such as nuts, bolts and handle assembly and tighten them,<br><br />
(ii) Check the axle bolt and tighten as needed,<br><br />
(iii) Make sure the lock nut is tight,<br><br />
(iv) Make sure the hand pump is firm on its base,<br><br />
(v) Check the flange bolts fastening the water chamber to the pedestal are tight,<br><br />
(vi) Testing water quality using a Field Test Kit.<br />
<br />
<br />
[[File:Figure 10.png|650px|center]]<br />
<br />
<br />
Figure 10. 1: India Mark II (left) and Cylinder Assembly of India Mark III Hand Pump (Right) <br />
(Source: India Operational and Maintenance Manual 2013).<br />
<br />
(b) '''Monthly Activities'''<br><br />
(i) Tighten the handle axle nut and lock nut,<br><br />
(ii) Check for loose or missing flange bolts and nuts and tighten as needed,<br><br />
(iii) Open the cover and clean inside the pump,<br><br />
(iv) Check the chain anchor bolt for proper position and tighten if needed,<br><br />
(v) Verify whether hand pump is firm on its base and fix it if needed,<br><br />
(vi) Open the cover and clean inside the pump,<br><br />
(vii) Verify rusty patches, clean with a wire brush and apply anticorrosive paint,<br><br />
(viii) Check for loose or missing flange bolts and nuts and tighten as needed,<br><br />
(ix) Check the chain anchor bolt for proper position and tighten if needed,<br><br />
(x) Look for rusty patches, clean with a wire brush and apply anticorrosive paint,<br><br />
(xi) Find out whether the hand pump base is loose and arrange for repair of the foundation as needed,<br><br />
(xii) Measure the static water level,<br><br />
(xiii) Grease all components.<br />
<br />
(c) '''Annual Activities'''<br><br />
(i) Verify the discharge of water,<br><br />
(ii) Verify the handle position and repair if needed,<br><br />
(iii) Verify whether guide bush, roller chain is not excessively worn out and replace if needed,<br><br />
(iv) Verify whether Discharge is satisfactory,<br><br />
(v) Verify whether Handle is shaky,<br><br />
(vi) Verify whether Guide bush is excessively worn out,<br><br />
(vii) Verify whether Chain is worn out,<br><br />
(viii) Verify whether Roller chain guide is excessively worn out,<br><br />
(ix) Discharge is satisfactory,<br><br />
(x) Check all parts of the hand pump for wear and tear / damages, replace damaged parts and reassemble the hand pump,<br />
(xi) Measure the well depth,<br><br />
(xii) All the components of the hand pump to be checked for wear and tear/damages and damaged parts replaced and hand pump re-assembled,<br><br />
(xiii) Washing and cleaning of the components of the hand pumps should be done with water and bleaching powder, if required instead of mixture of water and kerosene,<br><br />
(xiv) The repairs to the hand pump platforms to be done as and when needed and need not be on daily basis.<br />
<br />
===== Disassembly, Inspection and Reassembly of Hand Pump =====<br />
<br />
====== Disassembly ======<br />
<br />
Disassembly of the hand pump may be required from time to time if major problems are faced as follows:<br><br />
(a) Loose pump head cover bolt,<br><br />
(b) Remove inspection cover from head assembly,<br><br />
(c) Insert chain coupling supporting tool,<br><br />
(d) Lift the handle to the top position and disconnect chain from handle by removing the “nylon” nut and bolt (i.e., nylon insert lock nut),<br><br />
(e) Take out handle axle; while removing use the handle axle punch to protect the axle thread and remove the handle from the head assembly,<br><br />
(f) Remove flange bolts from the head assembly,<br><br />
(g) Remove head assembly from the water tank,<br><br />
(h) Place the connecting rod vice on to the water chamber top flange and tighten vice against connecting rod and allow the head assembly to sit on the connecting rod vice,<br><br />
(i) Disconnect the chain assembly from connecting rod,<br><br />
(j) Support connecting rod with connecting rod lifter, loosen connecting rod vice and remove; gently lower connecting rod to sit on check valve; remove connecting rod lifter,<br><br />
(k) Loose water tank nuts and bolts and remove water tank bottom flange bolts,<br><br />
(l) Lift water tank by using tank pipe lifter and lifting spanners,<br><br />
(m) Fit self-locking clamp and remove water tank,<br><br />
(n) Join plunger assembly to check valve by turning the rod lifter in clock wise direction,<br><br />
(o) To take out water from the pipe, remove the rod lifter; join the rod lifting adaptor to the connecting rod; place head assembly over water tank and fix handle to the lifter<br><br />
(p) Remove water from riser pipe by pushing down handle suddenly,<br><br />
(q) Lift handle upwards slowly and disconnect connecting rod lifting adapter and take out head assembly,<br><br />
(r) Tighten the connecting rod lifter to the connecting rod and lift the connecting rod and fix the connecting rod vice,<br><br />
(s) Hold the connecting rod, slowly loosen the rod vice and lift the connecting rod; tighten the vice and repeat the process until it is possible to remove the connecting rod; repeat the process until the last connecting rod with plunger and check valve is pulled out,<br><br />
(t) Separate the check valve from the plunger,<br><br />
(u) Unscrew the plunger from the check valve,<br><br />
(v) Remove all the parts of the check valves and clean them.<br />
<br />
====== Inspection ======<br />
Inspection for reassembly covers the following:<br><br />
(a) Check the water tank for leakage or damage,<br><br />
(b) Wash and clean all parts with a mixture of water and bleaching powder,<br><br />
(c) The stand assembly should be on a perfect level – check with a spirit level,<br><br />
(d) Check the coupler for broken threads,<br><br />
(e) Check flanges and spout pipe for cracks and leakage,<br><br />
(f) Check the handle axle, bearings and chain; apply grease to the bearings and chain.<br />
<br />
<br />
====== Reassembling ======<br />
Reassembling involves the following:<br><br />
(a) Ensure parts are clean and dry, and moving parts are lubricated with oil and grease,<br><br />
(b) Check ‘O’ ring and cup seal and replace as needed,<br><br />
(c) Remove cover of casing pipe for fixing stand assembly,<br><br />
(d) Place stand assembly over casing pipe and make sure that it is vertical and check level of flange by spirit level,<br><br />
(e) Fix water tank assembly on the stand flange by tightening the nuts and bolts,<br><br />
(f) Join the check valve and plunger,<br><br />
(g) Connect the plunger to the connecting rod,<br><br />
(h) Insert the plunger assembly connected with the check valve in the riser pipe and connect the riser coupler to the water tank,<br><br />
(i) Insert the lower end of the connecting rod in the riser pipe, and place the connecting rod over the water tank and fix it to the vice,<br><br />
(j) Join the connecting rod pieces as per the requirement and insert in the riser pipe,<br><br />
(k) Remove the connecting rod vice from the water tank by holding the top end of the connecting rod,<br><br />
(l) Fix the connecting rod lifter to the top end of the connecting rod and rotate in the direction of the arrow so as to separate the check valve from the plunger and ensure that it reaches the bottom plate,<br><br />
(m) Make a mark by hack saw on the connecting rod at the level of the water tank,<br><br />
(n) Lift the connecting rod assembly, fix the connecting rod vice and tighten the connecting rod,<br><br />
(o) Cut the connecting rod as per the marking after removing the connecting rod lifter,<br><br />
(p) Smoothen with the help of a file the cut surface of the connecting rod,<br><br />
(q) Make necessary threads on the top most end of the connecting rod,<br><br />
(r) Fix the middle flange on the top of the water tank and ensure that all four corners coincide,<br><br />
(s) Tighten the check nut at the top of the connecting rod,<br><br />
(t) Screw the chain on to the connecting rod,<br><br />
(u) Place the chain coupling supporting tool on the middle flange and remove the rod vice,<br><br />
(v) Place the middle flange and set flanges with water tank,<br><br />
(w) Place head assembly over the middle flange and tighten by spanner,<br><br />
(x) Place handle assembly and insert the handle axle by handle axle punch,<br><br />
(y) Lift the handle for fixing chain and tighten chain anchor bolt and nylon nut fully (i.e., nylon insert lock nut); remove chain coupler supporting tool by lowering the handle,<br><br />
(z) Lift handle up and apply grease on the chain,<br><br />
(aa) Lower down the handle and fix inspection cover and tighten the cover bolt fully by the crank spanner.<br />
<br />
=== Operation and Maintenance of Solar Systems ===<br />
<br />
==== Solar system ====<br />
<br />
'''General''' <br><br />
After the system has been installed and commissioned, focus shifts to O&M throughout its lifetime. System operation can be optimized by closely monitoring and recording key system parameters (data logging), enabling operators to assess system performance or demand changes.<br />
<br />
One crucial aspect of maintenance is warranties, usually against defective components or poor workman-ship. Under the defects liability period of 1 to 2 years, any items that fail, are not installed to standard, or are damaged by natural calamities must be corrected on site at cost to the contractor/supplier/ installer.<br />
<br />
'''Component usual warranty period'''<br><br />
Solar panels 25 years,<br><br />
Pump/motor 2-5 years,<br><br />
Inverter 5-10 years,<br><br />
Remaining components 1-2 years.<br />
<br />
During the warranty period, the supplier is also expected to check system components and perform preventive maintenance at least quarterly (in any case, neither pumps nor panels require heavy maintenance, with panels only needing periodic cleaning) to attend to user complaints within a reasonable period of time, and to resolve any system breakdowns within 3 days. In addition to component warranties, the supplier may also provide a performance warranty on the system as a whole, ensuring that it will meet or exceed the design performance for a number of years.<br />
<br />
Sustainability of Solar Water Pumping (SWP) has been a challenge in many countries and especially in rural areas, with systems failing often within a short time after commissioning due to lack of proper O&M. It is therefore increasingly common for communities to establish comprehensive maintenance contracts with suppliers during warranty periods, and it is a good practice to extend such contracts beyond the warranty period. Suppliers should further secure system sustainability by training system operators, namely on basic plumbing skills useful for repairing leakages in the pipe network and in handling the advanced inverters and sensors common in modern solar pumping systems. The rural water supplies audit (URT, 2018b) recommended introduction of such capacity building programme in identified zonal centres of RUWASA.<br />
<br />
Since solar panels have no moving parts that could be affected by rust or break down, solar power requires very limited maintenance, other than regular dusting. Cleaning the solar panels with water is recommended to remove any dirt or dust.<br />
<br />
'''Operation and Maintenance Guidelines'''<br />
<br />
Solar PV pumping systems are characterized by their simplicity, unattended operation, and low maintenance requirements compared to conventional systems. Except for the pump itself, there are no moving parts that would require periodic maintenance and incur additional costs every time maintenance is performed.<br />
<br />
In the case of battery usage for energy storage, which is not recommended, maintenance and battery replacement would be required every three to four years on average. There are some modern batteries that can live up to 8 years but are still considered expensive and would require very delicate preventive maintenance that might not be present in typical solar PV pumping applications (mainly in rural and remote regions).<br />
<br />
For the other components, the PV modules are considered sturdy and strong enough to withstand harsh environmental conditions coming with a warranty of 10 years, an expected lifetime of more than 25 years, and normally an efficiency maintenance guarantee that ensures efficiency drop doesn’t exceed 20% over the period of 25 years. The pump normally lives for more than 8 years and can reach 14 years if well maintained.<br />
Usually it is sold with a 2 year-warranty and spare part availability. Other than that, only occasional inspection and regular maintenance is required, at no cost, to make sure the system is doing fine and avoid losses due to dust or other residues sticking to the panel. It is essential to properly operate and maintain the pumping system to achieve high efficiency and reliable operations.<br />
<br />
'''Operation Guidelines'''<br><br />
(a) The pump should be switched off when not in operation;<br><br />
(b) The pump should never run dry. It is critical to make sure the suction is primed before turning on the surface pump;<br><br />
(c) The pump should be properly mounted and fixed on the base-plate to withstand vibrations and avoid unwanted noise that could also reduce the lifetime of the pump;<br><br />
(d) The pump should be used daily for at least 15 minutes to avoid problems;<br><br />
(e) Pump should be covered adequately for weather protection. In a pump pit adequate air venting system (passive or active) should be in place;<br><br />
(f) The surface pump should be kept away from water at all times;<br><br />
(g) The pump should not be switched on and off too often. There should be at least 15 seconds between a switch off and a switch on;<br><br />
(h) Foot-valve should be of minimum 2” (50 mm) size so as to minimize suction losses;<br><br />
(i) Sharp bends should be avoided in the pipelines to avoid unnecessary pressure drops;<br><br />
(j) Delivery and suction pipelines should be air-tight;<br><br />
(k) In case of thunders and strong wind, panels should be kept in the zero-tilt position (applicable only for tracking systems);<br><br />
(l) The cover of the main junction box should not be left open;<br><br />
(m) No loose wires should be un-insulated.<br />
<br />
'''Regular Maintenance'''<br><br />
'''Monthly'''<br><br />
• Panel Cleaning: Clean the panels regularly to avoid particles, leaves, and other residues from blocking the sun. Panels can be cleaned with a plain piece of cloth with some water when available;<br><br />
• Panel Inspection: Inspect the PV panels to make sure there are no cracks or damages.<br />
<br />
'''Biannual'''<br><br />
• Shadow Prevention: Check the panels for any shadow and perform necessary trimming of trees if necessary;<br><br />
• Wiring inspection: Check wires regularly for fraying, splitting, or damage.<br />
<br />
'''Annual'''<br><br />
• Valves Inspection: Check and clean the foot-valve,<br><br />
• Electrical Components Check: Check switches, fuse, wiring, junction box and connections.<br><br />
Biennial<br><br />
• Pump Inspection: For surface pumps, carbon brushes need to be checked and replaced every two years.<br />
<br />
<br />
[[File:Table10.2.png|550px|center]]<br />
<br />
Figure 10. 2: Operation and Maintenance Cycle for Solar Water Pumping<br />
<br />
==== Inspection ====<br />
<br />
Every system regardless of the type, must be inspected periodically. It is an important aspect for good operation of the system. System inspection should be conducted at least once a year depending on the size and intricacies of the system. Planned inspection, prompt timely maintenance and in some cases inspection and maintenance can be carried simultaneously especially when the inspectors also double up as maintainers. It is also highly recommended that the inspectors also triple as repair experts of the system. <br />
<br />
'''Inspection procedure for key Components:'''<br><br />
'''Solar panels'''<br><br />
(a) '''Check the solar panels for dirt and cracks,''' <br><br />
(i) Dirt accumulates on the solar panels over time, as they are exposed to the environment. Cracks may be due to vandalism or heavy hailstorms.<br><br />
(ii) If there are cracks on the panels, one should consider replacing those panels<br><br />
(iii) Dirt can be cleaned off the surface using clean water and a cloth. Soap should not be applied.<br><br />
(b) '''Electrical cables''' <br><br />
(i) Check to see if all electrical cables are still intact, loose cables should be tightened up.<br />
<br />
(c) '''Tilt Angle'''<br><br />
(i) In fixed solar arrays this may not be necessary, unless there is suspicion of tilt on angle if inclined. This should be corrected, to avoid dust accumulation on flatter inclines, and reduced solar absorption on steeper inclines.<br />
<br />
<br />
==== Inspection Checklist ====<br />
<br />
Inspection checklist gives guidance and easiness to the operator to do inspection. It saves times and increases accuracy as it includes all important elements to be checked. Appendix 9 presents the solar arrays and accessories inspection checklist.<br />
<br />
<br />
==== Paperwork ====<br />
<br />
In all inspections the importance of paperwork and record keeping cannot be over emphasized. It is prudent upon every inspector to keep and maintain a good record of the system, as this will form a major part of maintenance decision making.<br />
<br />
<br />
<br />
Table 10. 2: A Sample Record Status of the System<br />
{| class="wikitable"<br />
|-<br />
! Item Description !! Available !! Not Available !! Comments<br />
|-<br />
| Operation and maintenance manual for system on site or available || || || <br />
|-<br />
| Service record for system on site or available || || || <br />
|-<br />
| Flow diagram and sequence of operation on site or available || || || <br />
|-<br />
| Photographs taken and placed in service record || || || <br />
|-<br />
| This inspection record filed in service record || || || <br />
|}<br />
<br />
<br />
==== Troubleshooting a Solar Powered Water Supply System ====<br />
<br />
This section of the manual contains information that may be used to determine what is wrong with a solar powered water supply system. Troubleshooting techniques have also been explored. Troubleshooting a Solar Powered Water Supply System should involve more than looking for an obvious problem, or replacing components at random in an attempt to get the system working again. This is particularly true of Solar Powered Water Supply Systems. What is required is a systematic procedure that carefully “troubleshoots” the system until the problem is located and remedied.<br />
<br />
'''Cause or Symptom''' <br />
What may appear to be the cause of a problem may actually be a symptom of another problem. For example, if a pump is not pumping water, you can replace a pump while the problem is the electric cable that supplies current and voltage to the pump. Replacing the pump, will not solve the problem but result in wasting money and time for a simple problem. Never assume that a system is completely without faults after correcting a problem. Spend a few more minutes observing and inspecting the system. This will save time doing a return job. Or even a bigger job caused by an escalated problem which could have been spotted during the first visit.<br />
<br />
'''Recommended troubleshooting'''<br />
<br />
Good troubleshooters follow the below listed steps or a variation of them. The steps include:<br />
<br />
(a) Planning:<br><br />
(i) Planning takes off with brainstorming the possible causes of the problem,<br><br />
(ii) This includes the tools and materials used to diagnose the fault,<br><br />
(iii) It also includes the resources to be allocated for finding and fixing the fault, such as money, time and labour.<br />
<br />
(b) Cause /Source finding:<br><br />
(i) This is the investigation /diagnosis phase, <br><br />
(ii) Start with checks that will have low impact on the system,<br><br />
(iii) Proceed in a systematic, organized and logical manner,<br><br />
(iv) Isolate the results of testing to the component being tested,<br><br />
(v) Sometimes the only way to determine if a component is working properly or not is to replace it and see what happens. Remember that this may fix the symptom but it can fail to turn up the real cause of a problem. <br><br />
(c) Repairing: <br><br />
(i) Repairs can be made on a “quick fix/temporary repair” basis, doing as little as possible to get the system running again, <br><br />
(ii) Another approach is to replace major portions of the system to be absolutely certain the problem is gone, <br><br />
(iii) The correct approach is to determine what is the real cause of the problem is, and make repairs that solve that problem so that it does not happen again. Whether to repair or replace defective components depends on the cost and availability of the component,<br><br />
(iv) Generally, the more expensive and difficult it is to obtain something, the more appropriate the repair of the component, <br><br />
(v) If the part is cheap and readily available, it generally will be replaced, <br><br />
(vi) If repairs can be made to the defective component, it can become the new replacement the next time this same component fails in this or other systems. <br><br />
(d) Testing:<br><br />
(i) After the cause of the problem has been identified and corrected, inspect and test the entire system,<br> <br />
(ii) This confirms that the new components are working, and that no other problems exist,<br><br />
(iii) The defective components should be tested as well. The best time is usually before rebuilding. As an example, if a control works fine on a test bench, but not at all at the site, a problem exists at the site that will not let the new control work there either, <br><br />
(iv) If the part is truly defective, look for the reason it failed. For example, did the pump control unit get wet? Will the new control unit also get wet and fail? <br />
<br />
(e) Recording:<br><br />
(i) The last part of troubleshooting is record-keeping, <br><br />
(ii) Maintenance and repair records are kept to maintain a history of each system. <br><br />
<br />
Troubleshooting records should be part of that written history. In addition, writing down the troubleshooting process preserves that information for the person who found the problem.<br />
<br />
Table 10. 3: Troubleshooting Chart<br />
<br />
[[File:Table10.3.png|700px|center]]<br />
<br />
==== Repair Works ====<br />
<br />
This section includes information on the repair or replacement of solar powered potable water supply system components. The first section lists common components and whether to repair or replace them. Then, specific procedures for particular components are described. The section ends with a sample repair record sheet. During repair works, one normally asks questions of whether to repair or replace. Some components, such as Solar Panels, can never be repaired, and must be replaced. Others, such as mounting racks and supporting steels, are usually repaired rather than replaced. However, most components can be repaired/replaced. In general, the decision to repair or replace is based on:<br />
<br />
• Availability of replacement parts, <br />
<br />
• Lead time for replacement parts, <br />
<br />
• Cost of replacement parts,<br />
<br />
• difficulty of repair. <br />
<br />
<br />
Table 10. 4: Repair or Replace Choice Table<br />
<br />
[[File:Table10.4.png|700px|center]]<br />
<br />
<br />
Table 10.5 presents a typical repair worksheet.<br />
<br />
<br />
Table 10. 5: Repair Worksheet<br />
<br />
[[File:10.5i (2).PNG|700px|center]]<br />
[[File:10.5ii.PNG|700px|center]]<br />
[[File:10.5iii.PNG|700px|center]]<br />
<br />
==== Maintenance ====<br />
<br />
This is the most important section; it answers the question of how can the system be kept working. To the layman, it is perceived as the only section that ought to be given attention and disregard all the other sections. It cannot be over-emphasized how important preventive maintenance can be. It involves a great deal of pro-activeness. Every system ought to have a regular maintenance schedule that is appraisable. Some information on minor repairs is given; however, if major repairs are necessary, use repair information in Section 10.5.6. If a system has not been maintained, or has not been operational for some time, it is suggested to perform a system inspection, using Section 10.5.2, and to make necessary repairs before starting a regular schedule of maintenance.<br />
<br />
<br />
'''Maintenance procedures'''<br />
<br />
Preventive Maintenance activities are the core element of the maintenance services to a reticulated solar powered potable water supply system. It comprises regular visual and physical inspections, as well as verification activities with a specific task periodicity of all key components which are necessary to comply with the operating manuals and recommendations issued by the Original Equipment Manufacturers (OEMs). It must also maintain the equipment and component warranties in place and reduce the probability of failure or degradation. This maintenance will be carried out at predetermined intervals or according to the prescribed OEM manuals. These are included in a detailed Annual Maintenance Plan (AMP) which provides an established time schedule with a specific number of iterations for carrying out the maintenance. Tables 10.6 - 10.10 gives some of the tools that can be used.<br />
<br />
Table 10. 6: Example of Maintenance Contact List<br />
<br />
[[File:10.6.png|700px|center]]<br />
<br />
<br />
The maintenance contact list (Table 10.6) is easy to use at local level as it only outlines contacts of responsible maintenance team. As such it can be used by the water system users committee for further details of maintenance.<br />
<br />
'''Equipment manufacturer's manuals'''<br />
<br />
The equipment manufacturer’s manuals shall and will be attached in this section. The manuals should be used by the operations/maintenance team as reference. Preventive maintenance can be scheduled periodically from weekly to monthly and annually. Tables 10.7 - 10.10 outline the steps to be taken and tools used in performing preventive maintenance exercises.<br />
<br />
'''Wire control kit<br />
<br />
Recommended daily operational duties/preventive maintenance'''<br />
Based on the layout and operation of the system, several parameters for inspection and action were developed and set to respond to routine challenges of the system. Some of these actions to be performed can be categorized as daily, weekly, monthly and annually:<br />
<br />
The weekly preventive maintenance has been skipped because it is similar to the daily tasks.<br />
<br />
'''Preventive maintenance logbook'''<br />
<br />
All maintenance activities should be written down on a maintenance log book or log sheet. The logbook as Table 10.7 should be used to keep records of the maintenance on the system.<br />
<br />
<br />
Table 10. 7: Preventive Maintenance Logbook<br />
<br />
[[File:10.7.png|700px|center]]<br />
<br />
<br />
Ensuring security of the system may require conducting an assessment of the security within the system. Table 10.8 can be used to do such an assessment check.<br />
<br />
Table 10. 8: Security Assessment<br />
<br />
[[File:10.8.png|700px|center]]<br />
<br />
<br />
'''Spare Parts Management''' <br />
<br />
Spare Parts Management is an inherent and substantial part of O&M. it shall be used throughout the lifespan of the system. Table 10.9 is the tool that will be used to record available spares for the system by the maintenance team. From the water sales, 10 percent of the revenue generated from the system shall be kept as a reserve to purchase the spare parts. The major components like pumps, solar panel array, solar controller, water meter can be insured for damage and vandalism and this is elaborated in the risk management section of volume III of the DCOM Manual.<br />
<br />
<br />
Table 10. 9: Spare Material Management List<br />
<br />
[[File:10.9.png|700px|center]]<br />
<br />
<br />
<br />
'''Operators notes'''<br />
<br />
This section of the manual is intended for the use of the project (Water System Operator) who is in charge of operating the potable water supply project to guide them through the tasks of the Operator. It gives explanations of the facility structure and then explains the tasks of the operators, and things to bear in mind when operating facilities. It also provides in part, troubleshooting information.<br />
<br />
'''Operator’s duties'''<br />
<br />
The operator is the key person in the operation of the system. He has important roles that he/she has to execute on a daily basis. The roles encompass the following:<br />
<br />
• Operate the system properly or as designed,<br />
<br />
• Patrol and inspect the system daily and weekly,<br />
<br />
• To write the operation records, this consists of operational data, <br />
<br />
• To correspond with the Maintenance In-charge/Project Coordinator,<br />
<br />
• Be a link between the customers and the Maintenance In-charge/Project Coordinator,<br />
<br />
• Collect and collate issues from the customers.<br />
<br />
<br />
The sustainability of the system hinges mainly on the management aptitude of the operator. The operator is expected to safeguard the system and keep all records of the system operation.<br />
<br />
'''Detailed regular operational duties for the water operator:<br />
<br />
Solar Panel Array'''<br />
<br />
• Inspect cable wiring interconnecting solar panels,<br />
<br />
• Inspect inverter,<br />
<br />
• Inspect dirt /dust accumulation on solar panels,<br />
<br />
• Inspect structural integrity of solar panels tower.<br />
<br />
<br />
'''Water Control Unit and pump'''<br />
<br />
• Check control unit for fault reporting,<br />
<br />
• Observe sound and performance of submersible pump,<br />
<br />
• Inspect pump for leaks, <br />
<br />
• Observe water meter and record readings off it.<br />
<br />
<br />
'''Maintenance tools'''<br />
<br />
Maintenance tools should be kept inside the kiosk house and locked. A tool inventory should be conducted every month to establish the condition of the tools and also establish any lost tools. The plumbers should pay for lost tools. The tools should be used in maintaining the water project and should not be used for any other work outside the project. This practice prolongs the tool lifespan. Generally, tools should be used for the job they were designed for, wrong tools should not be used for any job.<br />
<br />
'''Reporting and communication'''<br />
<br />
Reports are major sources of the information. In implementing the projects, reports are a pre-requisite in order to know the implementation status and make a rational decision timely if the need arises. Operator needs to record the operational status of the system daily. The data will form a part of the project O&M monthly report. When faults are detected, it should be communicated to the Maintenance In-charge immediately. The Maintenance In-charge then coordinates repair work, depending on the type of repair required.<br />
<br />
The steps below outline the communication chronology in the project:<br />
<br />
• The water customers or water operator discover or notice a breakdown in the water supply system,<br />
<br />
• They notify the Maintenance In-charge/Project Coordinator swiftly,<br />
<br />
• The water operator requests for repair of the system,<br />
<br />
• The water operator notifies the Maintenance In-charge/Project Coordinator of the parts that are required to repair the breakdown,<br />
<br />
• The Maintenance In-charge/Project Coordinator avails funds for fixing the breakdown,<br />
<br />
• The Maintenance In-charge/Project Coordinator procures the materials needed to attend to the breakdown,<br />
<br />
• The Maintenance In-charge/Project Coordinator provides spare parts to the plumber to expedite repairs,<br />
<br />
• The plumber then expedites works on the repairs,<br />
<br />
• The plumber then prepares and submits a repair report to the Maintenance In-charge/Project Coordinator,<br />
<br />
• The Maintenance In-charge/Project Coordinator avails money and pays the plumber for the repairs,<br />
<br />
• The system is back to operation again.<br />
<br />
<br />
'''Repair manual'''<br />
<br />
In this section of the O&M manual, discussion will be based on repair procedures for certain components of the water system.<br />
<br />
<br />
'''Sample repair works record or report sheet'''<br />
<br />
Table 10.10 is a sample of a record sheet on any repair works that ought to be done on the system. It is very important to know the name of the technical person who attended to the fault. Date on which the fault was attended. The location of the repair is also important in order for the operators to pick up trends if any, on fault re occurrences.<br />
<br />
<br />
Table 10. 10: A Sample Repair Works Report Sheet<br />
<br />
[[File:10.10i.png|700px|center]]<br />
<br />
==== Variables Influencing Performance of Solar Water Pumping (SWP) ====<br />
<br />
The simplified SWP algorithm presented for understanding the sizing dynamics is good for static design conditions. In reality, there are several input variables that are not constant and thus affect SWP performance over the number of the years. To be rigorous, sizing algorithms must evaluate the conditions over the course of a whole year to determine when the limiting design conditions occur. Below are some of the key variables:<br />
<br />
(a) Seasonal changes in solar radiation. Essentially, SWP water output is more or less proportional to the irradiation. First-pass sizing is usually based on average insolation for the year, or perhaps the worst month of the year. It is necessary to assess the output for days when radiation will be less than the annual average, and less than the monthly average. Tilt angle optimization is required;<br />
<br />
(b) Seasonal changes in pumping head. Similarly, drops in water levels will affect pump output. Water output is more or less indirectly proportionate to the pumping head. Too conservative an estimation of water level will result in system over-sizing;<br />
<br />
(c) Sunny versus cloudy days. Average insolation is insufficient. A key variable is the amount of cloud cover and intermittency of the sunshine. Especially, variable speed drives coupled with AC pumps tend to suffer degraded performance under stop-start solar conditions, since they require minimum power conditions start-up, and take considerable time to spool up once threshold levels are reached. So while 2 days might have the same amount of cumulative insolation, a clear morning with zero sun in the afternoon is likely to yield far higher water output than an intermittently cloudy day. Derating for this kind of local variability is important for certain motor pump types in particular;<br />
<br />
(d) Seasonal changes in water demand. Experience shows that demand is not constant throughout the year. For human consumption, the variations are low (25%), but for livestock and irrigation the variations can be significant, up to 80%, with zero demand in very wet seasons. The analysis of these variables can be cumbersome.<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Nine: Distribution System]] << >> Next Page: [[Chapter Eleven: Audit and Conservation of Energy]]<br />
<br />
</div></div>Jumahttp://design.maji.go.tz/index.php/References:_ReferencesReferences: References2022-07-16T13:41:28Z<p>Juma: References</p>
<hr />
<div>= REFERENCES =<br />
<br />
Brikkè, F. (2000). Operation and Maintenance of rural water supply and sanitation systems. A training package for managers and planners. Malta: IRC International Water and Sanitation Centre and World Health Organisation.<br />
<br />
Brikke, F. and Bredero, M. (2003): Linking Technology Choice with Operation and Maintenance in the context of community water supply and sanitation. A reference Document for Planners and Project Staff. Geneva: World Health Organization and IRC Water and Sanitation Centre.<br />
<br />
Carter, R. C. (2009). Operation and Maintenance of Rural Water Supplies. In: Perspectives N° 2. St. Gallen: Rural Water Supply Network (RWSN).<br />
<br />
Castro, V. Msuya, N. and Makoye, C. (2009). Sustainable Community Management of Urban Water and Sanitation Schemes (A Training Manual). Nairobi: Water and Sanitation Program-Africa, World Ban.<br />
<br />
Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. New York: The McGraw-Hill Companies Inc.<br />
<br />
DfID (1998). Guidance Manual on Water Supply and Sanitation Programmes. London: Water, Engineering and Development Centre (WEDC) for the Department for International Development (DFID).<br />
<br />
EAWAG/SANDEC (2008). Faecal Sludge Management. Lecture Notes. (Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC).<br />
<br />
EWURA (2014). Water quality and wastewater quality monitoring guidelines.<br />
<br />
GoI (2013). Operation and maintenance manual for rural and water supplies. Government of India (GoI), Ministry of drinking water and sanitation.<br />
<br />
HELVETAS (n.y). Village Water Supply. Caretakers Manual. Bamenda: Helvetas Cameroon URL: https://sswm.info/sites/default/files/reference_attachments/HELVETAS%204000%20Village%20Water%20Supply.pdf [Accessed: 09.02.2020].<br />
https://mof.go.tz/mofdocs/msemaji/Five%202016_17_2020_21.pdf.<br />
<br />
Kresic, N. (1997). Hydrogeology and groundwater modeling. 2nd edition, CRC Press,828p.<br />
<br />
MALCOLM N. SHAW 2008, International Law, Sixth edition, Cambridge University Press, Cambridge Uk.<br />
<br />
Mang, H. P. (2005). Biogas Sanitation Systems. (Ecological sanitation course). Beijing: Chinese Academy of Agricultural Engineering.<br />
<br />
Mbwette, T.S.A, Jorgensen, S.E; Katima, J.H.Y, Njau, K. H, Kayombo, S. (Eds) 2002. Proc. 8th IWSA International conference on Westland system for water pollution control. Arusha, Tanzania, Vol.1&2.<br />
<br />
Meuli, C. and Wehrle, K. (2001). Spring Catchment. (Series of Manuals on Drinking Water Supply, 4). St. Gallen: Swiss Centre for Development Cooperation in Technology and Management (SKAT) URL: http://skat.ch/book/spring-catchment/ [Accessed: 08.02.2020] <br />
<br />
NETSSAF (2008). NETSSAF Participatory Planning-Approach. A tutorial for sustainable sanitation planning. Network for the Development of Sustainable Approaches for Large Scale Implementation of Sanitation in Africa (NETSSAF).<br />
NSGRP II & III<br />
<br />
Pradhikaran, M.J. (2012). Module 2 Operation and Maintenance of Water Supply System. Training Module for Local Water and Sanitation Management, CEPT University, India.<br />
<br />
Rocha Loures F & Rieu-Clarke A (eds) (2013). The UN Watercourese Convention in Force: Strengthening international law for transboundary water management. Earthscan, Routledge.<br />
<br />
Sasse, L. (1988). Biogas Plants. German Appropriate Technology Exchange (GATE) and German Agency for Technical Cooperation (GTZ) GmbH.<br />
<br />
SIWI (2015). International water law. Retrieved from: https://www.siwi.org/icwc-course-international-water-law<br />
<br />
UNEP (1998). Sourcebook of Alternative Technologies for Freshwater Augmentation in Some Countries in Asia (Technical Publication). Osaka/Shiga: United Nations Environmental Programme. International Environmental Technology Centre URL: http://www.unep.or.jp/ietc/publications/techpublications/techpub-8e/artificial.asp [Accessed: 07.02.2020]<br />
<br />
UNEP (2004). Chapter 4. Wastewater Technologies. In: UNEP (2004): A Directory of Environmentally Sound Technologies for the Integrated Management of Solid, Liquid and Hazardous Waste for SIDS in the Caribbean Region.<br />
<br />
UNFCC (2015). Paris Agreement on climate change 2015. Retrieved from: https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement<br />
<br />
UNFCCC (2015). Paris Agreement. United Nations Framework Convention on Climate Change (UNFCCC). <br />
<br />
United Nations (2015). Helping governments and stakeholders make the Sustainable Development Goals (SDGs) a reality. Retrieved from: https://sustainabledevelopment.un.org/<br />
URL: http://www.who.int/water_sanitation_health/publications/linking-technology-choice-with-o-m-in-ws/en/ [Accessed: 07.02.2020].<br />
<br />
URT (2000). The Tanzania Development Vision 2025. Ministry of Finance and Planning. https://www.mof.go.tz/mofdocs/overarch/vision2025.htm.<br />
<br />
URT (2002). The National Water Policy (NAWAPO). United Republic of Tanzania (URT).<br />
<br />
URT (2008). The National Water Sector Development Strategy (NWSDS). United Republic of Tanzania.<br />
<br />
URT (2014). Guidelines for Construction of Toilets and Sanitation. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br />
<br />
URT (2016). Five Year Development Plan (FYDP II), 2016/17 – 2020/21. Ministry of Finance and Planning. Retrieved from: https://mof.go.tz/mofdocs/msemaji/Five%202016_17_2020_21.pdf<br />
<br />
URT (2016). The National Guidelines for Water, Sanitation and Hygiene for Tanzania Schools. Ministry of Education, Science and Technology (MoEST).<br />
<br />
URT (2016). The Second Five Year Development Plan (FYDP II), 2016/17 – 2020/21. Ministry of Finance and Planning.<br />
<br />
URT (2017). National Guidelines for Water, Sanitation and Hygiene in Health Care Facilities. Ministry of Health, Community Development, Gender, Elderly and Children (MoHCDGEC).<br />
<br />
URT (2018b). Challenges of Implementation of Rural Water Supply Projects and Services in Tanzania: Findings of A Special Audit Committee. Final Report, Volume II: The Main Report. MoW.<br />
<br />
URT (January 2018). National (Tanzania) guideline on drinking water quality monitoring and reporting. Volume I. Ministry of Water. The United Republic of Tanzania (URT).<br />
<br />
URT (July, 2019). Water sector development programme; Guide line for good environmental and social practises (GGESP) revised version. Ministry of Water.<br />
<br />
URT (July, 2019). Water sector development programme; Guide line for good environmental and social management framework (ESMF) revised version. Ministry of Water.<br />
<br />
URT (October, 2015a). Guidelines for the preparation of water safety plans, resilient to climate change for rural water supply services. Ministry of Water.<br />
<br />
URT (October, 2015b). Guidelines for the preparation of water safety plans, resilient to climate change for urban water supply utilities. Ministry of Water.<br />
<br />
WHO (1996). Rapid Sand Filtration. (Fact Sheets on Environmental Sanitation, 2 / 14). Geneva: World Health Organization (WHO). <br />
Wolf 1999, cited in https://www.siwi.org/icwc-course-international-water-law/ visited on 08, March ,2020.<br />
<br />
World Bank (2010). Water and Sanitation Public- Private Partnership Legal Resource Centre. https://ppp.worldbank.org/public-private-partnership/sector/water-sanitation<br />
<br />
World Bank (2012). Rural water supply. Volume III: Operation and maintenance Manual. The World Bank Office, Manila, Philippines.<br />
<br />
'''Internet Links'''<BR><br />
'''1. Operation and Maintenance of Water Supply Projects'''<br><br />
a) https://www.ircwash.org/sites/default/files/202.6-93MA-11116.pdf<br><br />
b) http://documents.worldbank.org/curated/en/696331468144565653/Operation-and-maintenance-manual) accessed 03022020<br><br />
c) https://www.cmpethiopia.org/content/download/636/3335/file/Operation%20and%20Maintenance%20Manual%20for%20Urban%20Water%20Utilities.pdf <br><br />
d) http://skat.ch/wp-content/uploads/2018/12/Handbook_FINAL_APRIL_KDA.pdf<br><br />
e) IRC- https://www.ircwash.org/sites/default/files/202.6-89MA-12188.pdf<br><br />
f) http://www.gdrc.org/uem/water/wb-urbanwater.html <br><br />
g) https://www.jica.go.jp/english/our_work/thematic_issues/water/c8h0vm0000ammjc9-att/study_04.pdf , JICA;<br><br />
h) SSWM- https://www.sswm.info/planning-and-programming/ensuring-sustainability/ensure-sustainability/operation-and-maintenance<br><br />
i) https://www.slideshare.net/esmeraldoerandio/rural-water-supply-volume-iii-operation-and-maintenance-manual-PHILLIPINES<br><br />
j) https://www.mwe.go.ug/sites/default/files/library/WSDF%20Operations%20Manual.pdf<br><br />
k) https://www.unicef.org/publications/files/CFS_WASH_E_web.pdf<br><br />
l) http://cpheeo.gov.in/cms/manual-on-operation--and-maintenance-of-water-supply-system-2005.php<br><br />
m)https://phedharyana.gov.in/WriteReadData/WSSO/Manuals/Manual%20of%20Operation%20and%20Mtc%20CPHEEO%20Govt%20of%20India.pdf <br><br />
n) https://www.wateraid.org/mw/sites/g/files/jkxoof331/files/2019-10/Operation%20and%20Maintenance%20Manual%20for%20WaterAid%20Eswatini.docx <br />
<br />
'''2. O&M of Sanitation/Wastewater Projects'''<br><br />
a) https://akvopedia.org/wiki/O%26M_sanitation<br><br />
b) https://sswm.info/humanitarian-crises/urban-settings/hygiene-promotion-community-mobilisation/important/ensuring-appropriate-operations-and-maintenance-services<br><br />
c) https://sswm.info/planning-and-programming/ensuring-sustainability/ensure-sustainability/operation-and-maintenance<br><br />
d) https://www.wecf.eu/download/2011/October/2-939-susana-factsheet-wg10-version-5-july-2011.pdf?m=1319642173&<br><br />
e) https://www.cenntech.com/library/ultrafiltration.htm.vis.12.01.2020<br><br />
f) https://www.en.wikipedia.org/wiki/nanofiltartion.vis.12.01.2020<br><br />
g) https://www.cenntech.com/microfiltration-and-ultrafiltration.htm.vis.12.01.2020<br><br />
h) https://www.samtech.com/how-to-choose-the-best-microfiltration-and-ultrafiltration-system-for-your-facility,vis.12.01.2020<br><br />
i) https://www.crystalquest.com/pages/whats-is-ultrafiltration,vis.12.01.2020<br />
<br />
<br />
Previous Page: [[Chapter_Nineteen:_Community_Participation_and_Compliant_Redressal_System_in_Operation_and_Maintenance_of_Water_Supply_and_Sanitation_Projects]] << >> Next Page: [[DCOM_Volume_IV_Appendix_1]]</div>Jumahttp://design.maji.go.tz/index.php/Chapter_Nine:_Distribution_SystemChapter Nine: Distribution System2022-07-16T13:32:30Z<p>Juma: </p>
<hr />
<div><div style="text-align:justify"><br />
== Chapter Nine: Distribution System ==<br />
The overall objective of a distribution system is to deliver safe drinking water to the consumer at adequate residual pressure in sufficient quantity at convenient points and to achieve continuity and maximum coverage at affordable cost. Normally, the operations are intended to maintain the required supply and pressure throughout the distribution system. Critical points are selected in a given distribution system for monitoring of pressures by installation of pressure recorders and gauges.<br />
<br />
==== Issues Causing Problems in the Distribution System ====<br />
(a) '''Intermittent System'''<br />
<br />
The distribution system is usually designed as a continuous system but it is often operated as an intermittent system in many supply areas. Intermittent supply creates doubts in the minds of the consumer’s about the reliability of water supply. During the supply period, the water is stored in all sorts of vessels for use in non-supply hours, which might contaminate the water. Often, when the supply is resumed, the stored water is wasted and fresh water again stored. During non-supply hours, polluted water may enter the supply mains through leaking joints and pollute the supplies. Further, this practice prompts the consumers to always keep open the taps of both public stand posts and house connections leading to wastage of water whenever the supply is resumed. Intermittent systems and systems which require frequent valve operations are likely to affect equitable distribution of water mostly due to operator negligence.<br />
<br />
(b) '''Non-Availability of Required Quantity of Water'''<br />
<br />
Failure of source or failure of power supply may cause reduced supplies. Normally, the distribution affected reservoirs are designed for filling in about 8 hours of pumping and whenever the power supply is the pumping hours are reduced and hence the distribution reservoirs are not filled up leading to reduced supply hours and hence reduced quantity of water.<br />
<br />
(c) '''Low Pressure at Supply Point'''<br />
<br />
Normally peak demand is considered ranging from 2 to 3, whereas the water supply is given only for a different duration, leading to large peak factors and hence affecting the pressures in the distribution system. This is common with most water supply systems.<br />
<br />
(d) '''Leakage of Water'''<br />
<br />
Large quantity of water is wasted through leaking pipes, joints, valves and fittings of the distribution systems either due to bad quality of materials used, poor workmanship, and corrosion, age of the installations or through vandalism. This leads to reduced supply, loss of pressure and deterioration in water quality.<br />
<br />
Maintenance of appropriate positive pressure at all times to all consumers is the main concern of O&M. Negative pressure can cause contamination of water and very high pressure damages the pipelines. Low pressure may be avoided by taking the following steps:<br />
<br />
(i) Purposefully or accidently, a line valve is left closed or partly closed or blockage due to any material causing loss of pressure,<br />
<br />
(ii) Too high velocities in small pipelines,<br />
<br />
(iii) Low water level in SR,<br />
<br />
(iv) Failure of pumps/Booster pumps (either due to power failure or mechanical failure) feeding the system directly.<br />
<br />
<br />
(e) '''Unauthorized Connections'''<br />
<br />
Illegally connected users will contribute to the reduction in service level to authorized users/ consumers and deterioration of quality of water. Sometimes, even legally connected users draw water by sucking through motors causing reduction in pressures.<br />
<br />
(f) '''Extension of Service Area'''<br />
<br />
Due to extension of service area without corresponding extension of distribution mains, the length of house connections will be too long leading to reduction in pressures.<br />
<br />
(g) '''Age of the System'''<br />
<br />
With age, there is considerable reduction in carrying capacity of the pipelines due to encrustation. In most of the places, the consumer pipes get corroded or precipitates and leaks occur resulting in loss of water and reduced pressure and pollution of supplies<br />
<br />
(h) '''Lack of Records'''<br />
<br />
Records of replacement of fittings/pipes/valves, scouring of entire distribution system, system maps, designs of the network and reservoirs and historic records of the equipment installed in the distribution system are often not available, whereas some minimum information is required to operate and maintain the system efficiently.<br />
<br />
=== Operational Schedule ===<br />
==== Mapping and Inventory of Pipes and Fittings in the Water Supply System ====<br />
Availability of updated distribution system maps with contours, location of valves, flow meters and pressure gauges or taping points is the first requirement for preparation of operation schedule. The agency should set up routine procedures for preparing and updating the maps and inventory of pipes, valves and consumer connections. The maps shall be exchanged with other public utilities to contain information on other utility services like electricity, communications etc.<br />
9.2.2 Field Survey and Distribution Network Simulation<br />
<br />
Existing maps are used or conventional survey is employed for preparation and up-dating of maps. As an alternative to traditional survey and map preparation, 'total station method is gaining popularity. Total station instruments can be used for survey and mapping of villages where data is not readily available.<br />
<br />
The use of modern databases such as Geographical Information Systems (GIS), more and more detailed information can be included in analyses, specifically for monitoring of the network operation and maintenance. This is particularly very useful in cases where there is a huge amount of data and scenarios where manual/hardcopy analyses are not easy to handle or to understand properly.<br />
<br />
The use of GIS coupled with Global Positioning System (GPS) in water distribution system management can also greatly enhance the amount and accuracy of data available. The GIS maps are becoming readily available and the GIS system can receive any additional information that becomes available after any replacement, connection or disconnection or expansion of the system has taken place. In this way, these maps enable multiple use: providing direct input for the computer model (hydraulic), accurate billing information and the location of system components that are malfunctioning and have to be repaired, etc.<br />
<br />
'''Evaluation of Hydraulic Conditions'''<br />
<br />
A continuous evaluation of the hydraulic conditions of the water supply system can be done by the O&M personnel after obtaining the data on water volumes in the reservoirs, flow meter readings from and into the reservoirs connected to a transmission system and compared with the expected performance. This evaluation shall lead to identification of operational problems and/or system faults. Depending on the type of problems actions have to be initiated to ensure that the system functions as per the requirement.<br />
<br />
'''Simulation of Distribution Network'''<br />
<br />
Operations have to be planned for specific circumstances such as failure at source, failure of pumps, leakages or bursts. Criteria have to be determined on the basis of analysis of the effects of particular operations on the hydraulic configuration of the water supply transmission system. These effects can be seen in simulated operating conditions. Mathematical simulation models can be developed from basic data on the network such as length, size, flow, characteristics of pumps, valves, reservoir levels etc. This approach can be very useful for analysing the effects of variables on large and complex water supply transmission and distribution systems.<br />
<br />
==== Routine Operations of the Water Supply Distribution System ====<br />
The efficiency and effectiveness of a water supply system depends on the operating personnel's knowledge of the variables that affect the continuity, reliability, and quantity of water supplied to the consumers. The operational staff should be able to introduce changes in the hydraulic status of the system as required depending on those variables promptly and effectively. Routine operations shall be specified which are activities for adjusting the valves and operation containing procedures for operating the distribution system. It should contain procedures to obtain, process, and analyze the variables related to water flows, pressures and levels as well as the consequences of manipulating control devices, such as operation of valves and/or pumps so that the hydraulic status of the system can match the demand for water. When operators change their shifts, information on valve closure and opening must be exchanged.<br />
<br />
==== Operations in Break Downs and Emergencies ====<br />
Operations other than routine i.e. during breakdowns and emergencies have to be specified and should be carried out in specific circumstances when normal conditions change i.e. when flows, pressures and levels and operation of pumps change.<br />
<br />
==== Measurement of Flows, Pressures and Levels ====<br />
It will be necessary to monitor regularly operational data concerning flows, pressures and SR levels to assess whether the system is functioning as per requirements. Analysis of data may reveal overdraw of water to some reservoirs and or bulk consumers. At such places, appropriate flow control devices may be introduced to limit the supplies to the required quantity. A list of priority points in water supply system have to be identified such as installation of meters to measure flows, pressures and levels. A detailed map showing location or each measuring point has also to be prepared. The degree of sophistication of the devices used at each measuring point with regard to indication, integration, recording, transmission and reception of data depends mainly on the skills of the O&M personnel available with the agency and affordability of the agency.<br />
<br />
==== Sampling for Quality of Water ====<br />
The agency operating the water supply system is charged with the primary responsibility of ensuring that the water supplied to the consumer is of an appropriate quality. To achieve this objective, it is necessary that the physical, chemical, bacteriological and microbiological tests are carried out at frequent intervals. Samples should be taken at different points on each occasion to enable one to make an overall assessment. In the event of epidemic or danger of pollution, more frequent sampling may be required, especially for bacteriological quality. For each distribution system, a monitoring programme has to be prepared showing the location of sampling points. Based on historic records of a system it will be possible for the manager of the system to decide locations for bacteriological sampling and residual chlorine testing. Reference can be made to Section 7.5.2.1 item (ii) and MoW guidelines URT (2018).<br />
<br />
=== Management of Events of Water Shortage ===<br />
The objective of developing a programme for managing in times of shortage of water is to reduce the excessive use of water particularly when the source is limited due to the adverse seasonal conditions. Basically, it involves ensuring that a water conservation policy is developed and implemented among water consumers. The following activities can be considered while formulating such a water management project:<br />
<br />
(a) Installation of accurate water meters and establishment of a realistic tariff structure to encourage water conservation and prevent wastage of water. Common customer meter chambers can be useful as they assist to minimize tempering of individual/house connection meters,<br />
<br />
(b) Introduction of restrictions on use of flushing, showers and other household fittings,<br />
<br />
(c) Introduction of devices to limit water consumption in flushing of toilets,<br />
<br />
(d) Enforcement of restrictions on use of treated water for watering lawns, cooling, construction, washing of vehicles, etc.,<br />
<br />
(e) Encouragement and/or enforcement of the reuse of treated industrial effluents and wastewater,<br />
<br />
(f) Development and implementation of public education programmes to encourage water conservation,<br />
<br />
(g) Limit of length of service lines (house connections) is usually made as short as practically possible depending on how far is the distribution main.<br />
<br />
=== System Surveillance ===<br />
Surveillance of distribution system is done to detect and correct the following:<br />
<br />
(a) Sanitary hazards,<br />
<br />
(b) Deterioration of distribution system facilities,<br />
<br />
(c) Encroachment of distribution system facilities by other utilities such as sewer and storm water lines, power cables, telecom cables etc. and<br />
<br />
(d) Detecting and correcting damages of the system facilities by vandalism.<br />
<br />
=== Maintenance Schedule ===<br />
(a) A maintenance schedule is required to be prepared to improve the level of maintenance of water distribution networks and house connections through improved co-ordination and planning of administrative and field work and through the use of adequate techniques, equipment and materials for field maintenance,<br />
<br />
(b) The schedule has to be flexible so that it can achieve team action with the available vehicles and tools,<br />
<br />
(c) Co-ordination of activities is required for spares and fittings, quality control of materials used and services rendered,<br />
<br />
(d) Training of maintenance staff shall include training to achieve better public relations with consumers apart from the technical skills.<br />
<br />
=== Activities in Maintenance Schedule ===<br />
Following activities are to be included in the schedule:<br />
<br />
(a) Establishment of procedures for setting up maintenance schedules and obtaining and processing the information provided by the public and the maintenance teams,<br />
<br />
(b) Formation of maintenance teams for each type of service with provision for continuous training,<br />
<br />
(c) Establishment of repair procedures for standard services,<br />
<br />
(d) Specification of appropriate tools,<br />
<br />
(e) Allocation of suitable transport, tools and equipment to each team,<br />
<br />
(f) Establishment of time, labour and material requirement and output expected; time required and other standards for each maintenance task, and<br />
<br />
(g) Monitoring the productivity of each team.<br />
<br />
=== Preventive Maintenance Schedule ===<br />
A preventive maintenance schedule for servicing of valves and maintenance of valve chambers, maintenance of the pipelines: may include the tasks, set priorities, issue of work orders for tasks to be performed, list of scheduled tasks not completed, record of when the tasks are completed and maintaining a record of tools, materials, labour and costs required to complete each task.<br />
<br />
=== Leakage Control ===<br />
Wastage of water in the system and distribution network occurs by way of leakage from pipes, joints & fittings, reservoirs and overflow from reservoirs & sumps. The objective of leakage control programme is to reduce the wastage to a minimum and minimize the time that elapses between the occurrence of a leak and its repair. The volume of water lost through each leak should be reduced by taking whatever action technically and economically feasible to ensure that the leak is repaired as quickly as possible. To achieve this, the organization shall prescribe procedures for identifying, reporting, repairing and accounting for all visible leaks. <br />
<br />
It will be beneficial for the water utilities or authority or RUWASA if the procedures involve the conscious and active participation of the population it serves apart from its own staff. The management has to process the data and evaluate the work on detection and location of leaks and for dissemination of the results and initiate actions to control the overall problem of water loss. Interim measures for reduction/control of leakage can be initiated by controlling pressures in the water distribution system where feasible.<br />
<br />
==== Leakage Through House Connections ====<br />
Leakage can be controlled at the point of house connection and in the consumer pipe by adopting correct plumbing practices and improving the methods used for tapping the main and giving house connection and strict quality control on the pipe material used for house connection. An analysis of leaks in house connections and investigation of reasons for leaks in the house connections shall be carried out to initiate action on reducing the leakage through house connections.<br />
<br />
==== Procedures for Detecting Visible Leaks ====<br />
The water supply utility or authority or RUWASA has to establish procedures whereby the population served by the agency notifies the visible leaks. The water supply staff can also report visible leaks found by them while carrying out other works on the water supply system. Water supply utility or authority or RUWASA has to establish procedures for prompt repair of leaks and for attending efficiently and accurately to the leaks. Critical areas where leaks often occur have to be identified and appropriate corrective measures have to be implemented. Effective use of SCADA should be investigated.<br />
<br />
==== Procedures for Detecting Invisible Leaks ====<br />
Establishment of procedures for detecting and locating non-visible leaks shall be compatible with the technological, operational and financial capability of the utility or authority or RUWASA. Selection and procurement of equipment for detection and location of leaks must take into account the cost-effectiveness and the financial capability of the organization.<br />
<br />
=== Cross Connections ===<br />
Contaminated water through cross connections of water supply lines with sewers and drains is a problem prevailing widely. Intermittent supply further aggravates the problem since, during non-supply hours polluted water may reach the supply mains through leaking joints, thus polluting the supplies. In certain instances, when there are extremely high water demands, the pressures in the supply mains are likely to fall below atmospheric pressure, particularly when consumers start use of pumps with direct suction from the supply mains, a process that is regarded to be illegal. <br />
<br />
Regular survey has to be undertaken to identify potential areas likely to be affected by cross connections and back-flow. All field personnel should be constantly alert for situations where cross connections are likely to exist. After identifying the cross connections, remedial measures taken up which can include: providing horizontal and vertical separation between the water main and the sewer/drain providing a sleeve pipe to the consumer pipes crossing a drain, modifying the piping including changing corroded piping with non-corrodible piping, providing double check/non-return valves at the consumer end. The various types of materials of pipe & specifications are being used in the distribution system and specific requirements of maintenance are to be followed as per water supply authority/utility/RUWASA/Manufacturer’s recommendations.<br />
<br />
=== Plumbing Practices for Drinking Water Supply ===<br />
The internal plumbing system of the consumer shall conform to the National recommendations and also particularly to the by-laws of concerned water supply authority/utility/RUWASA. The various types of plumbing materials are being used and require different maintenance practices. The utility can regulate up to the connection to supply mains. It is recommended to use licensed plumbers.<br />
<br />
Therefore, specific requirements of maintenance are to be followed as per the Manual/ Manufacturer’s recommendations or water supply authority/utility/RUWASA recommendations/specifications indicated in Volume I.<br />
<br />
==== Quality of Pipe Material for House Connection ====<br />
The water supply authority/utility/RUWASA shall ensure that the connection and communication pipe from the street main up to the consumer premises is laid as per correct plumbing practices and must adopt improved methods for tapping the main. Strict quality control is required on the pipe material used for house connection. The by-laws shall lay down rules for defining the ownership and responsibility for maintaining the point of connection and the communication pipe. In several utilities, the communication pipes are leaking since they are corroded; however these are not replaced by the consumer or by the utility particularly where the O&M responsibility for consumer pipe rests with the consumers.<br />
<br />
==== Contamination through House Connection ====<br />
While laying the consumer connection pipes there are is a need to avoid contamination of water supplies. This can be achieved by maintaining horizontal and vertical separation between the water supply communication pipe and the sewer/drain. In some instances, a sleeve pipe may be required to be provided to the consumer pipes crossing a drain. It is always recommended to provide a non-corrodible pipe material for the consumer connection. Contamination by possible back flow can also be prevented by ensuring provision of double check/non-return valves at the consumer end.<br />
<br />
==== Rules for Consumer Connections ====<br />
The water supply authority/utility/RUWASA shall formulate rules for sanctioning of consumer connection, tapping the mains and laying the connection piping. Water supply utility shall undertake inspection of the consumer premises before releasing the connection to ensure that the internal plumbing system of the consumer conforms to the requirements. Water supply authority/utility/RUWASA shall supervise the process of drilling/tapping of the mains for giving connection and laying of the consumer piping.<br />
<br />
The process of submission of applications for connections by consumers and carrying out the connection work through licensed plumbers is also prevalent in some utilities. In such cases, the water supply authority/utility/RUWASA shall formulate procedures for licensing the plumbers including the qualifications to be possessed by the plumber, facilities and tools to be available with the plumber for the work to be undertaken by the plumber. The water supply authority/utility/RUWASA shall closely observe the quality of materials used and works done by him and he should act as per procedures laid down in the bye laws/regulations for approval of the connection works, renewal or cancellation of the plumbers’ licenses or any other requirement depending on their performance or non-performance.<br />
<br />
=== Chlorine Residual Testing at Consumer End ===<br />
A minimum chlorine residual of about 0.2 - 0.5 mg/l at the selected monitoring point/ consumer’s end is often maintained to ensure that even a little contamination is destroyed by the chlorine. Hence, absence of residual chlorine could indicate potential presence of heavy contamination. If routine checks at a monitoring point are carried out, required chlorine residuals and any sudden absence of residual chlorine should alert the operating staff to take up prompt investigation. Immediate steps to be taken are:<br />
<br />
(a) Re-testing for residual chlorine,<br />
<br />
(b) Checking chlorination equipment,<br />
<br />
(c) Searching for the potential source of contamination, which has caused the increased chlorine demand, and<br />
<br />
(d) Immediate stoppage of supplies from the contaminated pipelines.<br />
<br />
=== Sample Records to be Maintained by the Water Supply Utility ===<br />
Sample records to be maintained by the water supply utility are given below for guidance:<br />
<br />
(a) Updated system map,<br />
<br />
(b) Pressure and flow readings at selected monitoring points,<br />
<br />
(c) Persistent low pressure or negative pressure areas,<br />
<br />
(d) Age of pipes/quality of pipes,<br />
<br />
(e) Pipelines to be replaced,<br />
<br />
(f) Presence of undesirable materials,<br />
<br />
(g) Water budget for each zone served by one SR,<br />
<br />
(h) Number of connections given,<br />
<br />
(i) Number of meters out of order<br />
<br />
(j) Quantity measured at outlet of reservoir,<br />
<br />
(k) Quantity distributed/measured or billed,<br />
<br />
(l) Water budget for each zone served by one SR<br />
<br />
(m) Source of leaks and persistent leak points,<br />
<br />
(n) Status of bulk meters - functioning or not,<br />
<br />
(o) Status of consumer meters,<br />
<br />
(p) Facilities for repairs of consumer meters,<br />
<br />
(q) Number of unauthorized connections,<br />
<br />
(r) Residual chlorine levels at the pre-selected monitoring points,<br />
<br />
(s) Bacteriological quality of the water sampling points, <br />
<br />
(t) Persistent areas where residual chlorine is absent/where water samples are found contaminated,<br />
<br />
(u) Record of carrying out repairs on the following:<br />
<br />
(i) The pipe line leaks or replacement of pipes,<br />
<br />
(ii) Change of gland ropes of the valves in distribution system,<br />
<br />
(iii) Record on man hours spent on routine operations in the distribution system in the previous year and the cost thereof.<br />
<br />
=== Record keeping ===<br />
(a) To maintain necessary inventory of the materials used and required. Record of total cost of repairs and replacements in previous years along with breakdown of material and labour costs with the amount spent on outside agencies for repairs and replacements,<br />
<br />
(b) Replacement of damaged manhole covers,<br />
<br />
(c) Record on when the exposed piping was last painted and the cost of materials and labour cost thereof, and<br />
<br />
(d) Record of the un-served areas - extension of pipelines- need for interconnection.<br />
<br />
<br />
<br />
<br />
Previous Page: [[Chapter Eight: Drinking Water Storage Tanks]] << >> Next Page: [[Chapter Ten: Pumping Machinery]]<br />
</div></div>Juma