UGC NET Questions (Paper – 1)

Domestic sewage contains organic substances that can be decomposed by microorganisms. Over time,microbes break down this material into simpler compounds,although the process can deplete dissolved oxygen in water bodies. Because it can be naturally degraded,domestic sewage is considered a biodegradable pollutant. Therefore biodegradable is the correct category in the question.

Option A:
Non biodegradable pollutants are materials such as heavy metals or plastics that do not break down easily in natural systems. They persist in the environment for long periods. Domestic sewage does not fit this description because its organic components are decomposed relatively quickly by microbes.

Option B:
Radioactive pollutants involve unstable isotopes that emit ionising radiation and are typically associated with nuclear activities. Domestic sewage generally does not contain such isotopes in significant amounts. Hence this option is not suitable for the waste described.

Option C:
Thermal pollution refers to changes in water temperature,often due to discharge of heated effluents from power plants. While it can harm aquatic life,it is a physical rather than organic pollutant. Domestic sewage primarily causes organic loading,so thermal is not accurate.

Option D:
Biodegradable pollutants undergo decomposition by bacteria and other organisms,returning many elements to natural cycles. Domestic sewage is a textbook example,so this category correctly captures its environmental behaviour.