In sewage treatment,after the $BOD$ is reduced to the required level,the effluent is passed into which of the following?

What does $STPs$ stand for?

What is sewage? Through what is sewage water passed before being disposed of?

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.

Select the correct sequence with respect to sewage treatment.
$i$. Removal of suspended solid particles by primary treatment.
$ii$. Wastewater screening
$iii$. Anaerobic bacteria digest activated sludge.
$iv$. Treatment by flocs in aeration tank.
$v$. Grit settling

Why do we prefer to call secondary wastewater treatment as biological treatment?