TGPSC HMWSSB Manager 2015 Paper 2 · Question 79

Question 79 of the TSPSC Manager (Engineering), HMWSSB, 2015: Paper 2 (Civil Engineering) (1 November 2015). Try it first, then open the answer and explanation.

1. Manager 2015 Paper 2 (Civil) · Q79 · Environmental Engineering · Water Supply

   The disinfection efficiency of chlorine in water treatment

   1. Is not dependant on pH value
   2. Is increased by increase in pH value
   3. Remains constant at all pH values
   4. Is reduced by increase in pH value
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   Answer: (4) Is reduced by increase in pH value

   Chlorine forms hypochlorous acid (HOCl), which dissociates into the much weaker hypochlorite ion (OCl⁻) as pH rises; so disinfection is best at low pH (below about 7) and falls as pH increases.

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