water_hardness.ppt Civil Engineering Notes

Water Civil Engineering Notes for Diploma students

1. Prepared by Anna Danczowska-Burdon

2. Water hardness is caused
by the presence of salts
dissolved in water,
primarily calcium and
magnesium.
It causes the formation of
boiler scale during water
boiling and bad soap
foaming.

3. carbonate hardness – also called temporary
water hardness is caused by the presence of
carbonates, hydrocarbonates and hydroxides of
calcium and magnesium.
Noncarbonate hardness – caused by the presence
of Ca
2+
, Mg
2+
of other cations and anions like:
Al
3+
, Fe
2+
, Fe
3+
, Cu
2+
, Cl
-
, SO
4
2-
, NO
3
-
, which do not
decompose and do not precipitate during boiling
water.
General water hardness – is the summary
content of calcium, magnesium and other ions

4. Caused by the presence of hydrocarbonates,
carbonates and hydroxides of calcium and
magnesium. It can be removed by water boiling.
Ca(HCO
3)
2 → CaCO
3 + H
2O + CO
2
Mg(HCO
3
)
2
→ MgCO
3
+ H
2
O + CO
2

5. Clark’s Method,
Blacher’s Method,
Warta-Pfeifer Method,
method using EDTA
(versenate)
separate determination
of calcium and
magnesium ions