. . . . . . is the first step of sewage treatment.

Sewage or municipal waste should not be directly passed into rivers,streams and other water bodies because
$I.$ it contains human excreta and other organic waste
$II.$ it contains a number of pathogenic microbes
Which of the statement given above is/are correct?

In a sewage treatment plant,primary treatment is

Identify the sequence of processes in sewage treatment:

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 is the full form of $STPs$?