A sewage treatement process in which a part of decomposer bacteria present in the wasts is recycled into the starting of the process is called as

Options

A. primary treatment
B. activated sludge treatment
C. tetriary treatment
D. none of these

Answer

B

Explanation

The activated sludge system, a part of secondary treatment, is one of the widely used aerobic treatment systems for waste water in which very vigorous aeration of the sewage is done. The sewage is passed into an aeration tank from primary settling tank. The flocs are allowed to settle down in secondary settling tank. in settling tank, the bacterial focs are allowed to undergo sedimentation. the effluent or supernatant is generally passed into natural water bodies like rivers and streams. The sediment of settling tank is called activated sludge. A part of it is used a sincolum in aeration tanks. The remaining part is passed into a large tank called anaerobic sludge digesters.