Environmental Engineering FOURTH EDITION

Water Treatment 149

Suspended solids removal (rng/crn3)

figure 7-10. Increased head loss in a filter owing to materials deposits. (Adapted from
Metcalf and Eddy, Inc., Wastewater Engineering, McGraw-Hill, New York, 1979.)

The total water through the filter is

min

h

4- gal x(20ftx20ft)x4hx60-=384,000gal

min-ft2

L

384,000 gal x 3.785 - = 1.45 x 106L.

gal

Solids removal is 55 - 3 = 52 mg/L

52 mg/L x 1.45 x lo6 L = 75.4 x lo6 mg.

Effective filter volume = 20 ft x 20 ft x 0.5 ft = 200 ft3

200ft3 x 0.02832m3/ft3 x lo6 cm3/m3 = 5.65 x 106cm3.

Suspended solids removal per unit filter volume is

From Fig. 7-9, h~ 5 m = 16.45 ft, so the total head loss of the dirty filter is

5.78 ft + 16.45 ft = 22.2 ft.