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Water Pollution and Sewage Treatment - Class X
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Multiple Choice
Study the given differences between primary sludge and activated sludge and select the incorrect ones.
| Primary Sludge | Activated sludge | |
|---|---|---|
| (i) | It is sludge formed during primary sewage treatment. | It is sludge formed during secondary sewage treatment. |
| (ii) | It possesses flocs of decomposer microbes. | It does not possess flocs of decomposer microbes. |
| (iii) | It does not require aeration. | Formation of activated sludge requires aeration. |
| (iv) | A lot of decomposition occurs during formation of primary sludge. | Very little decomposition occurs during formation of activated sludge. |
- (i) and (ii)
- (ii) and (iv)
- only (iv)
- (ii) and (iii)