Question

A lake with an inflow of domestic sewage rich in organic waste may result in:

• A. Drying of the lake very soon due to algal bloom.
• B. An increased production of fish due to lot of nutrients.
• C. Death of fish due to lack of oxygen.
• D. Increased population of aquatic food web organisms.

Answer 1

Answer: (C)

Domestic sewage leads to organic loading or occurrence of excess organic matter inside water. Its putrefaction decreases dissolved oxygen. Blue green algae present in the bloom also release toxins. Both toxicity and decreased oxygen level kill aquatic animals. Anaerobic putrefaction produces pollutants like methane, hydrogen sulphide, and ammonia. They kill the bloom forming plants as well. The water body comes to have foul smell, brown colouration, bad taste and oil.