✓ Board-verified
Biology · 2023 · 2 marks
CBSE 2023 · Region 3 · Set 1 · Q18
(a) Write the first step the primary effluent undergoes when it enters the secondary treatment plant and state the purpose. (b) What is the level of…
(a)
Write the first step the primary effluent undergoes when it enters the secondary treatment plant and state the purpose.
(b)
What is the level of B.O.D indicative of in the secondary treatment plant ? Mention its significance.
Marking-scheme solution
(a)
Primary effluent passes to aeration tank/ it is constantly agitated mechanically and air is pumped into it, this allows vigorous growth of flocs (masses of bacteria associated with fungal filaments to form mesh like structure)/ to consume organic matter/to reduce BOD level of primary effluents
(b)
It is a measure of organic matter /polluting potential in the water, greater BOD more is polluting potential.
All Microbes in Human Welfare questions2023 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 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.