Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures. These consume the major part of the organic matter in the effluent, significantly reducing the BOD. The effluent is then passed into a settling tank where the flocs sediment. A part of this sediment (activated sludge) is pumped into anaerobic sludge digestors where anaerobic digestion of sludge takes place, producing biogas in the process.
