Read the following passage and answer the questions that follow :
Sewage is generated in large quantities in the urban areas. It is treated in sewage treatment-plants (STPs) to make it less polluted before discharging into any natural water body. Observe the flow chart given below and answer the questions that follow :Primary effluent is passed into large aeration tank
↓
Effluent is passed into settling tank to form the sediment (activated sludge)
(c) (i) Name the two groups of microbes present in the primary effluent after it is passed into large aeration tanks.
Sewage is generated in large quantities in the urban areas. It is treated in sewage treatment-plants (STPs) to make it less polluted before discharging into any natural water body. Observe the flow chart given below and answer the questions that follow :
Primary effluent is passed into large aeration tank
↓
Effluent is passed into settling tank to form the sediment (activated sludge)
(c) (i) Name the two groups of microbes present in the primary effluent after it is passed into large aeration tanks.
Show Hint
Solution and Explanation
In the aeration tank air is pumped into the primary effluent.
This keeps it agitated and gives plenty of oxygen to aerobic microbes.
Step 2: The two groups of microbes:
Useful aerobic heterotrophic bacteria grow in this tank.
Fungi also grow along with them as filaments.
Together they form flocs, which are masses of bacteria held together by fungal filaments.
Final Answer:
Aerobic bacteria and fungi.
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Assertion (A) : Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage.
Reason (R) : Flocs help in digestion of solid waste by anaerobic respiration.
A laboratory assistant collected three water samples, namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant. But the laboratory attendant did not note which was which. The samples were labelled A, B and C and subjected to a BOD test. The BOD values of the three samples A, B and C were recorded as 30 mg/L, 8 mg/L and 400 mg/L respectively.
(a) Which sample of the water is most polluted ?
(b) Can you assign the correct label to each, assuming the river water is relatively clean ?
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