CBSE 2023 · Region 3 · Set 1 · Q18 · 2 marks
(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.
(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.
Microbes in Human WelfareMicrobes in Sewage TreatmentUnderstandvery_short_answermedium
More from Microbes in Human Welfare
- Assertion: Activated sludge contains large population of bacteria. Reason (R): These bacteria help in…2026 · asked 3×
- Assertion: Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage.…2026 · asked 3×
- Study the figure given below and answer the questions that follow. Identify the figure and state its…2025 · asked 3×
- Study the given diagram of Sewage Treatment Plant (S.T.P.) and answer the questions that follow: S.T.P.…2022 · asked 3×
- Mention the common bacterium found in the anaerobic sludge during sewage treatment and also in the rumen of…2022 · asked 3×
- (i) Name the protozoan species that is responsible for causing the most serious and even fatal malarial…2026 · asked 3×
- A laboratory assistant collected three water samples, namely river water, untreated sewage water and…2026 · asked 3×
- What do you mean by activated sludge in an STP? Explain the biological treatment of the major part of the…2025 · asked 3×
CBSE Class 12 Biology past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.