Question

For surface water system, the required residual disinfectant concentration may not be less than _______ mg/L for more than ___________ hours before the first customer.

(a) 0.2, 6

(b) 2.0, 6

(c) 0.2, 4

(d) 2.0, 4

The question was posed to me in an interview for internship.

Asked question is from Membrane Filter in division Building Blocks of Dairy Processing of Dairy Engineering

Answer 1

Right option is (c) 0.2, 4

Best explanation: The residual disinfectant concentration required is equal to or more than 0.2mg/L. This should be applied 6 hrs before the 1st usage.