Same chapter3 marksDifficulty: Medium
What is biochemical oxygen demand, and what does a high value indicate?
Microbes in Human Welfare
3 marksDifficulty: Medium
Describe the role of microbes in sewage treatment.
Original Khojo Papers practice question — not from a past board paper.
Answer
In the primary treatment the solids are removed physically. In the secondary or biological treatment the effluent is aerated so that aerobic microbes grow into flocs and consume the organic matter, which sharply reduces the biochemical oxygen demand. The settled sludge is then digested anaerobically by methanogens, which produce biogas.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
The biochemical oxygen demand of the effluent is the measure of how well the treatment has worked.
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