Water Treatment Processes - Mathematics and Statistics for the Environment - page 634

( )

4 gp pd

Cp

−

= ××−×
×

4981 . ( 2400 998 ) 0 001 . p

2

u =

3 30 .50 × 998

D

u = 0.192 m/s

Re-check Re:

= ×××

Φ pud
µ

= ×× ×

080 . 998 0 192 . 0 001 .

Re = 156

0 00098 .

Calculate u using the new Re value:

24
156

3
156

C D =+ += 034073 . .

= ×××
××

4981 . 1402 0 001 .

2

u

3073 . 998

u = 159 m/s

Re-check Re:

= ×× ×

080 . 998 0 159 . 0 001 .

Re = 130

0 00098 .

Calculate u using the new Re value:

24
130

3
130

C D =+ += 034079 . .

= ×××
××

4981 . 1402 0 001 .

2

u

3079 . 998

u = 0.152 m/s

Thus, the estimated velocity is approximately 0.15 m/s.

23.5.11 o verFloW r ate (s edimentation )
Overflow rate, detention time, horizontal velocity, and weir overflow rate are the parameters typi-
cally used for sizing sedimentation basin. The theoretical detention time (plug flow theory) is com-
puted from the volume of the basin divided by average daily flow:

= 24

V
Q

t (23.64)

where
t = Detention time (hr).
24 = 24 hr per day.
V = Volume of basin (m 3 , gal).
Q = Average daily flow (m 3 /d, MGD).