Q. Ca+2 = 20 ppm, Mg+2 = 25 ppm, CO2 = 30 ppm, HCO-3 = 150, K+ = 10 ppm. Calculate the lime (87% pure) and soda (91% pure) required softening 1 million litters of water sample.
Ans.
Calculation of CaCO3 equivalent of given impurities:
|
S.NO
|
substances
|
Amount of substances in mg/L
|
Multiplication factor
|
CaCO3 equivalent mg/L
|
|
1.
|
Ca++
|
20 ppm
|
100/40
|
100/40*20 =50
|
|
2.
|
Mg++
|
25 ppm
|
100/24
|
100/24*25 = 104.16
|
|
3.
|
CO2
|
30 ppm
|
100/44
|
100/44*30 = 68.181
|
|
4.
|
HCO-3
|
150 ppm
|
100/122
|
100/122*150 = 122.95
|
|
5.
|
K+
|
10 ppm
|
Not produce hardness
|
|
Lime required:
74/100[Mg++ + CO2 + HCO-3 as CaCO3 equivalent] mg/L *Volume of water*100/%purity
74/100[104.16 + 68.181 + 122.95] mg/L*1000000l*100/86
74/100[295.29] mg/L * 100000*100/87
= 251.16*106 mg
= 251.16*106 mg*1Kg/106
= 251.16
Soda required = 106/100[50 + 104.16 – 122.95] mg/L *1000000*100/91
= 100/106[31.21] mg/L*106*100/91
= 36.35*106 mg
= 36.35*106 mg*1Kg/106
= 36.35Kg