Question

A wastewater treatment plant has two primary clarifiers, each 20m in diameter with a 2-m side-water depth. the effluent weirs are inboard channels set on a diameter of 18m. for a flow of 12900m^3/d, calculate the overflow rate, detention time,and weir loading.

Answer 1

overflow rate 20.53 m^3/d/m^2

Detention time 2.34 hr

weir loading 114.06 m^3/d/m

Step-by-step explanation:

calculation for single clarifier

`sewag\  flow Q = (12900)/(2) = 6450 m^2/d`

`surface\  area =(pi)/(4)* diameter ^2 = (pi)/(4)* 20^2`

`surface area = 314.16 m^2`

volume of tank
`V  = A* side\ water\ depth`

`=314.16* 2 = 628.32m^3`

`Length\ of\  weir = \pi * diameter of weir`

`= \pi * 18 = 56.549 m`

overflow rate =
`v_o = (flow)/(surface\ area) = (6450)/(314.16) = 20.53 m^3/d/m^2`

Detention time
`t_d = (volume)/(flow) = (628.32)/(6450) * 24 = 2.34 hr`

weir loading
`= (flow)/(weir\ length) = (6450)/(56.549) = 114.06 m^3/d/m`