Biochemical oxygen demand as indicator – UGC NET Question

Biochemical Oxygen Demand measures the amount of dissolved oxygen required by microorganisms to decompose organic matter in water. A high BOD value means that microbial activity will consume large amounts of oxygen, which can deplete DO levels and stress aquatic life. Such conditions are typical of water polluted with sewage or other organic wastes. Therefore, a high BOD value indicates high biodegradable organic load and probable pollution, making Option B correct.

Option A:
Option A is incorrect because very clean water with low organic pollution would show low BOD values. High BOD is a sign of high organic content, not cleanliness.

Option B:
Option B is correct as it links high BOD to high organic matter and likely pollution. This interpretation underlies regulatory standards for effluent discharge and river water quality classification.

Option C:
Option C is incorrect since the presence of organic matter and high BOD implies active microbial populations, not their absence. Microorganisms are responsible for consuming oxygen as they break down waste.

Option D:
Option D is incorrect because chemically pure drinking water should have low BOD, indicating minimal organic contamination. High BOD water generally requires treatment before it is safe to drink.