Question

Chlorine usage in the treatment of $25000m^3/day$ is 9 kg/day. The residual chlorine after 10 minutes of contact is 0.2 mg/l. Calculate the dosage in milligram per liter and the chlorine demand of the water.

• A. 0.36 mg/L, 0.16 mg/L
• B. 0.36 mg/L, 0.36 mg/L
• C. 0.16 mg/L, 0.36 mg/L
• D. 0.16 mg/L, 0.16 mg/L

Answer 1

The correct option is A 0.36 mg/L, 0.16 mg/L

Water treated per day = $25000m^3$

= $25\times {10}^{6}liters/day$

Chlorine consumed per day = 9 kg $=9\times {10}^{6}mg/day$

$\therefore$ Chlorine used per litre of water $=\frac{9\times {10}^6}{25\times {10}^6}$

$=0.36mg/l$

Also, residual chlorine = 0.2 mg/l

Chlorine demand = 0.36 - 0.2 = 0.16 mg/l