Water Pollution and Its Control Questions and Answers

Answer: B

Itai-itai disease is due to Cadmium.

Itai-itai ('it hurts, it hurts') disease broke out in the Jinzu river basin of Japan, where mining waste polluted rice fields with cadmium. Long exposure softened the bones and damaged the kidneys, causing severe pain and fractures.

Lead poisoning causes plumbism and nerve damage, and mercury, not tin or strontium, caused Japan's other famous disease, Minamata disease.

Answer: C

Algal bloom is linked to Eutrophication.

When a lake or pond receives excess nutrients, mainly nitrates and phosphates from fertilisers and sewage, algae multiply rapidly into a bloom. When they die, bacteria decompose them and use up the dissolved oxygen, killing fish. This nutrient enrichment and oxygen depletion of a water body is eutrophication.

Global warming, salination and biomagnification are different environmental processes and are not the outcome of an algal bloom.

Answer: C

The maximum permissible level of chlorides in drinking water according to the WHO international standards is 600 mg/L, the figure in the 1971 standards, in which the highest desirable level was 200 mg/L. The values 100 mg/L and 200 mg/L are below the permissible limit and belong with the desirable range, and 800 mg/L exceeds the limit. Chloride mainly affects taste, making the water salty, so the limit is set by acceptability rather than by toxicity.