Suppose sewage water is disposed off in the river. What will be its effect on BOD and dissolved oxygen. OR Sewage discharge into clean water body leads to increased fish mortality. Explain.

Suppose sewage water is disposed off in the river. What will be its ef

1.	Suppose sewage water is disposed off in the river. What will be its effect on BOD and dissolved oxygen. OR Sewage discharge into clean water body leads to increased fish mortality. Explain.
Answer» Discharge of sewage water into a river will increase nutrients and thereby promotes algal growth. This will result in rise of BOD (Biochemical Oxygen Demand) as decomposers will consume more dissolved oxygen in river. If sewage quantity is large, the whole of the dissolved oxygen will be consumed leaving nothing for respiration of fishes and other aquatic organisms. This increases the mortality rate of aquatic creatures.