Which microorganisms are responsible for the formation of flocs in sewage treatment?

Select the appropriate option regarding the aeration tank.

Select the appropriate option regarding secondary treatment.

In sewage treatment,where does the sedimentation of flocs occur?

Given below are two statements with reference to the secondary treatment of sewage.
Statement $I$: The $BOD$ of effluent increases.
Statement $II$: Flocs of bacteria consume the major part of the organic matter present in the effluent.
In the light of the above statements,choose the most appropriate answer from the options given below.

What gases are produced in anaerobic sludge digesters?