✓ Board-verified
Biology · 2025 · 3 marks
CBSE 2025 · Region 4 · Set 1 · Q25
Explain the biological treatment of primary effluent when passed into the large aeration tanks in a sewage treatment plant (STP).
Explain the biological treatment of primary effluent when passed into the large aeration tanks in a sewage treatment plant (STP).
Marking-scheme solution
− The sewage is constantly agitated mechanically and air is pumped into it
− This allows the vigorous growth of useful microbes into flocs
(masses of bacteria associated with fungal hyphae to form mesh like structures
− While growing these microbes consume the major part of the organic matter in the effluent
− This significantly reduces the Biochemical Oxygen Demand or
BOD
All Microbes in Human Welfare questions2025 question paperNCERT solutions: Microbes in Human WelfarePractice Microbes in Human Welfare →
More from Microbes in Human Welfare
- A list of organisms is given in column 'R', whereas in column 'S' a list of products produced by them: Select the option where the organisms are…2024
- Assertion: Activated sludge contains large population of bacteria. Reason (R): These bacteria help in anaerobic digestion of human waste in biogas…2026
- Microbes commonly used in kitchen are2026
- Explain the role of the following during the sewage treatment: flocs anaerobic sludge digester2024
- Assertion: Besides curdling of milk, LAB also improves its nutritional quality by increasing Vitamin B12. Reason (R): LAB, when present in the…2026
- Many members of genus Glomus form a mycorrhizial association with plants. Elaborate how is this association beneficial to the plants.2022
- Explain the role of microorganisms in the following: Reducing the sugar content in grape juice Production of a fuel2023
- The process of mineralization by microorganisms help in the release of:2025
CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.