Difference between revisions of "DCOM Volume I Appendix I"
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=Appendix I: Measurement of Water Hardness= | =Appendix I: Measurement of Water Hardness= | ||
| − | Hardness and its Measurement | + | '''Hardness and its Measurement'''<br> |
Hardness is expressed in terms of mg/l by weight in terms of calcium carbonate. Water having hardness not exceeding 70 mg/l is termed ‗soft‘ and above that 'hard'. In public water supplies, it used to be customary to reduce carbonate hardness to 35 - 40 mg/l and total hardness to between 50 and 100 mg/l. However as indicated above this is no longer recommended unless hardness exceeds about 130 mg/l, but should still be practised for strictly industrial supplies of hard water. | Hardness is expressed in terms of mg/l by weight in terms of calcium carbonate. Water having hardness not exceeding 70 mg/l is termed ‗soft‘ and above that 'hard'. In public water supplies, it used to be customary to reduce carbonate hardness to 35 - 40 mg/l and total hardness to between 50 and 100 mg/l. However as indicated above this is no longer recommended unless hardness exceeds about 130 mg/l, but should still be practised for strictly industrial supplies of hard water. | ||
| − | Hardness = ∑ divalent cations = Ca2+ + Mg 2+ + Fe 2+ + Mn 2+ + Sr 2+..... | + | '''Hardness = ∑ divalent cations = Ca2+ + Mg 2+ + Fe 2+ + Mn 2+ + Sr 2+..... |
| − | + | '''<br> | |
Principle cations causing hardness in water and major anions associated with them are as follows: | Principle cations causing hardness in water and major anions associated with them are as follows: | ||
Table I.1: Principle cations and anions associated with water Hardness | Table I.1: Principle cations and anions associated with water Hardness | ||
Revision as of 11:03, 5 June 2020
Appendix I: Measurement of Water Hardness
Hardness and its Measurement
Hardness is expressed in terms of mg/l by weight in terms of calcium carbonate. Water having hardness not exceeding 70 mg/l is termed ‗soft‘ and above that 'hard'. In public water supplies, it used to be customary to reduce carbonate hardness to 35 - 40 mg/l and total hardness to between 50 and 100 mg/l. However as indicated above this is no longer recommended unless hardness exceeds about 130 mg/l, but should still be practised for strictly industrial supplies of hard water.
Hardness = ∑ divalent cations = Ca2+ + Mg 2+ + Fe 2+ + Mn 2+ + Sr 2+.....
Principle cations causing hardness in water and major anions associated with them are as follows:
Table I.1: Principle cations and anions associated with water Hardness
