Question

Why are flocs important in biological treatment of waste water?

Answer 1

Secondary/biological treatment

Secondary treatment or biological treatment is done to reduce the organic matter of the sewage. Reduction of organic matter is important before the sewage is discharged into the water bodies as this reduces the pollution potential of sewage. The BOD (Biochemical Oxygen Demand) of the water body has to be less for aquatic life to survive. The secondary sewage treatment ensures the reduction of BOD.

Significance of flocs

During the secondary treatment of sewage, the primary effluent is aerated allowing the growth of flocs. The flocs consist of mainly small masses of aerobic bacteria associated with filaments of aerobic fungi. The aerobic organisms in the floc oxidise the organic matter in the primary effluent, reducing the BOD.