Differences between primary sludge and activated sludge.

Explanation

All the solids that settle, after filtration and sedimentation of the sewage form the primary sludge, while the supernatant forms the effluent. Activated sludge constitutes the bacterial flocs (masses of bacteria associated with fungal filaments to form mesh like structures), sedimented in the settling tank, when the effluents after secondary treatment is taken into it. A major part of activated sludge is pumped into large tanks called anaerobic sludge digesters for the production of biogas a mixture of `CH_4,H_2S` and `CO_2`.