In how many stages is the sewage treatment process carried out in $STPs$?

How is $BOD$ reduced in sewage treatment?

Biological process is carried out in which type of water treatment?

What happens to activated sludge?

Statement $S$: In the primary stage of sewage treatment,physical particle matter is removed from water through filtration and sedimentation.
Reason $R$: Through sedimentation,soil or small pebbles are removed.

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