Chlorine is used as the disinfectant in a municipal water treatment plant. It achieves 50 percent of disinfection efficiency measured in terms of killing the indicator microorganisms

Q. Chlorine is used as the disinfectant in a municipal water treatment plant. It achieves 50 percent of disinfection efficiency measured in terms of killing the indicator microorganisms (E-Coli) in 3 minutes. The minimum time required to achieve 99 percent disinfection efficiency would be

(A) 9.93 minutes

(B) 11.93 minutes

(C) 19.93 minutes

(D) 21.93 minutes

Ans: 19.93 minutes

Solution:

Disinfection efficiency