What is the composition of flocs?

Select the appropriate option regarding secondary treatment.

Removal of suspended,floating,coarse and solid particles in sewage treatment is called . . . . . . .

Which of the following statements is incorrect regarding sewage treatment?

Given below are two statements about sewage. Based on them,select the correct option given below.
Statement $I$: The sediment in the settling tank is called floc.
Statement $II$: Sewage is first passed in the grit chamber,then it is screened.

What is obtained as a byproduct in the process occurring in $STPs$?