Page 478 - Water and wastewater engineering

GRANULAR FILTRATION 11-51

11-15. What effect does removing the 100–140 sieve fraction have on the depth of the ex-
panded bed in Example 11-3 ?
11-16. Determine the number of filter beds for Eau Gaullie ( Problem 11-10 ) if the maximum
3
day design flow rate is 3,800 m /d.
11-17. Determine the number of filter beds for Laramie ( Problem 11-12 ) if the maximum
3
day design flow rate is 55,000 m /d.
11-18. In the continuing design of Eau Gaullie’s rapid sand filter ( Problems 11-10 , 11-11 ,
and 11-16 ), determine the area of each filter cell and the plan dimensions of a filter
box. Assume a gullet width of 0.5 m.
11-19. In the continuing design of Laramie’s rapid sand filter ( Problems 11-12 , 11-13 and
11-17 ), determine the area of each filter cell and the plan dimensions of a filter box.
Assume a gullet width of 0.8 m.
11-20. Design the backwash system for Eau Gaullie’s rapid sand filter. Use the filter dimen-
sions from Problem 11-18 . The backwash system includes the layout of the back-
wash troughs, backwash velocity, flow rate of backwash water per trough, the trough
dimension (width and depth), trough elevation, volume of backwash tank, and eleva-
tion of the lowest water level in the backwash tank.
11-21. Design the backwash system for Laramie’s rapid sand filter. Use the filter dimen-
sions from Problem 11-19 . The backwash system includes the layout of the back-
wash troughs, backwash velocity, flow rate of backwash water per trough, the trough
dimension (width and depth), trough elevation, volume of backwash tank, and eleva-
tion of the lowest water level in the backwash tank.
11-22. Determine the gullet dimensions for Eau Gaullie’s rapid sand filter. Use the filter di-
mensions from Problem 11-18 and the backwash rate from Problem 11-20 . Assume a
250 mm diameter pipe from the gullet is to carry the wash water at a velocity of
0.9 m/s.
11-23. Determine the gullet dimensions for Laramie’s rapid sand filter. Use the filter di-
mensions from Problem 11-19 and the backwash rate from Problem 11-21 . Assume
a 700 mm diameter pipe from the gullet is to carry the wash water at a velocity of
1.2 m/s.
11-24. Determine the depth of the filter box for Eau Gaullie’s sand filter. Use the clean bed
headloss from Problem 11-10 and velocity headloss from Problem 11-22 . Assume
the minimum depth of water above the filter bed is 2.4 m, that the gravel is 0.25 m
deep, and that the depth of the underdrain is 0.25 m.
11-25. Determine the depth of the filter box for Laramie’s sand filter. Use the clean bed
headloss from Problem 11-12 and velocity headloss from Problem 11-23 . Assume
the minimum depth of water above the filter bed is 2.4 m and that an IMS drain that
is 30 cm deep is used.

11-26. Design the structural components * of a rapid sand filter for the village of Waffle. The
3
maximum day flow rate is 8,700 m /d. The design criteria and sand analysis are given
*These do not include the pipe gallery or control system.