MCQ
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-sew-age treatment | It is sludge formed during secondary sewage treatment |
| (ii) It possesses floes of decomposer microbes | It does not posses floes 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 |
- A(i) and (ii)
- ✓(ii) and (iv)
- C(i), (iii) and (iv)
- D(ii) and (iii)