Large quantities of sewage is generated everyday in cities and towns, which is treated in Sewage Treatment Plants (STPs) to make it less polluted. Given below is the flow diagram of one of the stages of STP.
Observe the given flow diagram and answer the questions accordingly

(a) Why primary effluent is passed into large aeration tanks?
(b) Write the technical term used for the sediment formed? Mention its significance
(c) Explain the final step that results in the formation of biogas in the large tank before the treated effluent is released into water bodies.

Options

A. Flocs
B. Effluents
C. Activated sludge
D. Anerobic sludge

Answer

B

Explanation

The effluent after primary treatmentis passed into the settling tank where the bacterial flocs are allowed to settle down and this sediment is called Activated sludge. A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculium(starter)