Q. A sample of water analysis was found to contain temporary magnesium hardness 25 mg/L. Permanent magnesium chloride hardness 15 mg/L and permanent calcium sulphate hardness 20 mg/L, SiO2 = 30kg/L. Calculate the lime and soda required for softening 30,000 litters hard water.
Ans.
Conversion of CaCO3 equivalent
|
constituent
|
amount
|
Multiplication factor
|
CaCO3 equivalent
|
|
Mg(HCO3)2
|
25 mg/L
|
100/146
|
25*100/146=17.12 mg/L
|
|
MgCl2
|
15mg/L
|
100/95
|
15*100/95=15.72mg/L
|
|
CaSo4
|
20mg/L
|
100/136
|
20*100/136=14.7mg/L
|
|
|
|
|
|
SiO2 do not required Lime soda.
Lime required = 74/100(Temp. hardness + Perm. Hardness) = 74/100(17.12 + 15.12) = 24.30 mg/L
Lime required for 30000 Litre hard water = 24.30*30000 = 729 mg
Soda required = 106/100(perm. Ca hardness + perm. Mg hardness) = 106/100(15.72 + 14.70) = 32.24 mg/l
Soda required for 30000 litre hard water = 32.24 mg/λ*30000λ = 967.2 mg