Characteristic of Protozoa in Activated Sludge Process

Group 1, 2 and 3 : Characterize of young sludge inside activated sludge process

The protozoa consist of  predominate Amoebae and flagellates with a few free swimming ciliates.

Group 4:  Characterize of mature sludge inside activated sludge process

For municipal wastewater treatment plants the most desirable stage of the ecological succession is the stage where both stalked ciliates and free swimming ciliates are observed with possibly a few rotifers. This stage is is correlated with rapid settling of solids and easy separation of solids from water. The resulting effluent is correspondingly low in turbidity, suspended solids and biochemical oxygen demand (BOD).

Group 5: Characterize of old sludge

Predominating of rotifers and nematodes with fewer stalked ciliates.

Examples of group 4 protozoa: Vorticella and Epistylis