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.

Options

A. (i) and (ii)
B. (ii) and (iv)
C. (i),(ii) and (iv)
D. (ii) and (iii)

Answer

B

Explanation

Activated sludge possesses flocs of decomposer microbes, whereas, primary sludge does not possess flocs. Unlike primary sludge a lot of decomposition occurs during formation of activated sludge.