2.8 Design of Filter Feeding & Filter Distribution Channels

The Filter Feeding Channel shall collect the clarified water from the launders of the three Clarifiers and carry it to the Filter Distribution Channel. Dimensions of the Filter Feeding Channel shall remain the same as of the Clarifier Feeding Channel, both being designed for 35 cusecs capacity. The channel connecting the Clarifier Launder and the Filter Feeding Channel shall be 5’-0” long. The design of connecting channel is as follows:

Flow under extreme conditions = 23.33 Cusecs
Flow under normal operating conditions = 11.67 Cusecs

Design of Connecting Channel

Flow through the Channel = 23.33 Cusecs
Velocity through the Channel = 3 Ft / s
Crossectional Area = 7.78 Sft
Width of the Channel = 4 Ft
Depth of the Channel = 2 Ft
Provide Free Board = 1 Ft

Dimensions of the connecting channel are 4’-0” Wide and 2’-0” deep.

Since Connecting Channel will discharge in to the Filter Feeding Channel, it is necessary to determine the difference of levels of the water surfaces of the two channels. Difference of water levels of the two channels is worked out below:

∆H = (Q / Cd x A x (2xg)1/2) 2



Where :

∆H = Difference of water level between Connecting Channel & Filter Feed Channel
Q = Flow through the Connecting Channel
A = Crossectional Area of the Connecting Channel
g = Acceleration due to gravity
Cd = Coefficient of Discharge


∆H = (23.33 / 0.61 x 2 x 4 x (2 x 32.2) 1/2) 2

= 0.370 Ft
= 0.67 Ft (Say)

Connecting Channel and the Filter Feeding Channel are so adjusted that the vertical distance of their water surfaces should be 0.5 Ft.

Design of Filter Distribution Channel

The design basis of Filter Distribution Channel is that it should be able to uniformly distribute clarified water in the filters. Kawamura (2000), P - 229 has recommended a minimum velocity of 1.5 Ft / s to be maintained in the Filter Distribution Channel.

Flow through the Distribution Channel = 35.0 Cusecs
Velocity through the Channel = 1.5 Ft / s
Crossectional Area = 23.33 Sft
Width of the Channel = 4.5 Ft
Depth of the Channel = 5.20 Ft

Channel has been designed for an ultimate flow of 18 MGD. Under the present phase of facility development when the flow would be 12 MGD, the velocity in the channel will be around 1 Ft /s.