In an oxidation pond used for sewage treatment, dissolved oxygen required by the bacteria degrading organic matter is supplied chiefly by:

• A Mechanical aerators installed across the pond
• B Algae performing photosynthesis in the presence of sunlight ✓
• C Anaerobic digestion at the sludge layer
• D Diffusion of oxygen from the inlet sewage flow

Explanation

Oxidation ponds operate on an algae-bacteria symbiosis. Bacteria oxidize organic matter into carbon dioxide and nutrients; algae use these products plus sunlight to photosynthesize and liberate oxygen, which sustains bacterial aerobic degradation. The pond is shallow, usually 1 to 1.5 metres deep, precisely to let light penetrate. Mechanical aeration defines aerated lagoons instead, which kills distractor A.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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