Water Treatment MCQ with answer and solution

Concept

Swimming pool water must be clear, keep a small residual disinfectant, be skimmed at the surface, and use only the minimum chemicals needed so swimmers are not harmed.

Step-by-step solution

1. Recall the requirements for pool water: residual disinfectant, clarity up to the bottom, surface skimming, and minimum chemical dose. 2. A says there should be no disinfectant. This is wrong, because residual chlorine is needed. 3. C says the water need not be visible at maximum depth. This is wrong, because the bottom must be clearly visible for safety. 4. D says no surface water removal system is needed. This is wrong, because skimmers or overflow gutters are needed to remove oil and scum. 5. B (minimum chemical) is correct, because excess chemicals irritate the eyes and skin.

Explanation

Pool water must be safe for skin and eyes, so chemicals should be kept to the minimum needed. A small residual disinfectant must still be present. The water must also be clear to the bottom, and the surface must be skimmed regularly.

Why the other options are wrong

A: A residual disinfectant (chlorine) is required in pool water. C: Water must be clear enough to see the bottom at maximum depth, for lifeguard safety. D: An efficient surface removal (skimming) system is needed to remove oil, hair and scum.

Shortcut

Three options use negative words ('should not', 'need not'). These go against basic hygiene and safety, so the positive option B is the answer.

Common mistake

Thinking pool water needs no disinfectant because people do not drink it.