Question

The efficiency of chlorine increase by ______________

(a) Presence of metallic compounds

(b) When  the pH of  the water increases

(c) When the pH of the water decreases

(d) Turbid water

This question was addressed to me in unit test.

Question is from Factors Affecting Chlorination topic in portion Properties of Disinfection of Environmental Engineering

Answer 1

Right option is (c) When the pH of the water decreases

To elaborate: The efficiency of chlorine is inversely proportional to the pH of water. When the pH of the water containing chlorine decreases, the efficiency of chlorine increases.