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HIGH-RATE GRANULAR MEDIA FILTRATION 8.35

The required cross-sectional area of the trough for a given washwater flow can be es-
timated from Figure 8.20. A more rigorous analysis can be obtained by referring to de-
rivations provided by Fair, Geyer, and Okun (1968) and Brater and King (1976).
After troughs are installed in a filter, weir edges must be leveled to uniformly match
a still water surface at the desired overflow elevation. It is critical that troughs be prop-
erly supported both vertically and horizontally so that their weirs remain absolutely level

12.03
11.59

11.14
10.69
10.25
9.80
9.36
4000
8.91
3800 8.47
z
d
~ 3600 8.02 uJ
z
7.58 ,17:
3400
<
0
~ 3200 7.13 m
L9
3000
6,68
O
,-r
0
2800 6.24
w D.
2600
5.79
O 9
2400
6.35 u-
2200 4.90
2000
4.46
1800
4.01
1600 3.56
1400
3.12
1200
2.67
1000 2,23
800
1.78
600
1.34
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
"W" INCHES
* Free Discharge
FIGURE 8.20 Washwater trough-sizing diagram. (Source." F. B. Leopold Co., Inc.)