High amount of $E. coli$ in water indicates:

What is the free water above the primary sludge called?

$A$ sewage treatment process in which a part of decomposer bacteria present in the wastes is recycled into the starting of the process is called:

$(a)$ What would happen if a large volume of untreated sewage is discharged into a river?
$(b)$ In what way is anaerobic sludge digestion important in sewage treatment?

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

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.