Question

A city supply of 15000 cubic meters of water per day is treated with a chlorine dosage of 0.5 ppm. For the purpose, the requirement of 25% bleaching powder per day would be .......

• A. 300 kg
• B. 75 kg
• C. 7.5 kg
• D. 30 kg

Hint:

Always convert ppm to mg/L and then use volume in liters to calculate the required chlorine. Adjust for bleaching powder strength using proportion.

Answer 1

The Correct Option is D

Given:
Water supply = 15000 m$^3$/day = 15,000,000 liters/day
Chlorine dosage = 0.5 ppm = 0.5 mg/L
Chlorine required per day = 15,000,000 L $\times$ 0.5 mg/L = 7,500,000 mg = 7.5 kg
Note: 1 ppm = 1 mg/L
Since bleaching powder contains 25% available chlorine,
Required bleaching powder = $\frac{7.5}{0.25}$ = 30 kg/day