An oxidation pond treats sewage primarily through the synergistic action of:

• A Residual chlorine carried over from prior treatment
• B Chemical coagulation by sunlight-induced photolysis
• C Anaerobic sludge digestion occurring throughout the pond volume
• D Algae producing oxygen and bacteria oxidising organic matter ✓

Explanation

In an oxidation pond, shallow depths allow sunlight penetration; algae photosynthesise and release oxygen which aerobic bacteria use to oxidise organic waste, while bacteria release carbon dioxide for the algae. This symbiotic cycle achieves BOD reduction without mechanical aeration. Anaerobic digestion is limited to settled bottom sludge, and neither photolysis nor chlorine carryover drives the purification process.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.