Difference between revisions of "DCOM Volume I Appendix I"
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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> |
| − | '''<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 | ||
| + | |||
| + | {| class="wikitable" | ||
| + | |- | ||
| + | ! Cations !! Anions | ||
| + | |- | ||
| + | | Ca<sup>2+</sup> || HCO<sup>-</sup><sub>3</sub> | ||
| + | |- | ||
| + | | Example || 2-SO4 | ||
| + | |- | ||
| + | | Example || Example | ||
| + | |- | ||
| + | | Example || Example | ||
| + | |- | ||
| + | | Example || Example | ||
| + | |} | ||
Revision as of 11:08, 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
| Cations | Anions |
|---|---|
| Ca2+ | HCO-3 |
| Example | 2-SO4 |
| Example | Example |
| Example | Example |
| Example | Example |
