Civil Engineering - Water Supply Engineering - Discussion

I) The detention time (t) of a settling tank may be defined as the average theoretical time required for the sewage to flow through the tank. It is thus the time that would be required for the flow of sewage to fill the tank if there was no outflow.

(ii) In other words, it is the average time for which the sewage is detained in the tank.
Hence it is the ratio of the volume of the basin to the rate of flow through the basin.

My opinion is option A is correct because Detention period is time required to empty the tank and detention time is time required to fill the tank.

The answer is D,

A" is flow through the period.

@Madhu.

How? please explain.

Only option C is right.