Question

A rectangular sedimentation basin receives water at 10 degrees Celsius with a flow rate of 0.5 m³/s. The sedimentation basin is 20m wide, 60m long, and 6m deep. The effective settling zone in the sedimentation basin is 45 m long. Determine the number of double sided weir troughs placed parallel to the length (L) of the basin.

Answer 1

Ans) Given ,

Flow rate (Q) = 0.50 m³/s or 43200 m³/day

Tank dimensions = 20 m x 60 m x 6 m

Length of settling zone = 45 m

Detention time (t) = LBH/Q

= 20 x 60 x 6 / 0.5

= 14400 sec or 240 min or 4 hr

  We know, Weir Overflow rate (WOR)= Flow/Length of weir

   Assume WOR = 10000 m³/m²/day

Length of weir = 43200/10000

= 4.32 m

Length of settling zone = 45 m

Number of weir = 45/4.32

= 10.41

or 11 (approx)