UFC 3-280-04
17 DEC 2003
(30 gpm + 5 gpm = 35 gpm)
C-1.5
Filter Diameter. Calculate the filter surface area:
A = total flow / flow per unit area
(2.22 L/s) / ([1.70 L/s]/ m2) = 1.30 m2
([35 gpm] / [2.5 gpm/ ft2] = 14 ft2)
1.90 m2 x 10,000 cm2 / m2 = 13,100 cm2
(14 ft2 x 144 in.2/ ft2 = 2016 in.2)
Calculate the filter diameter:
d = 2 x (A/π)1/2
(13,100 cm2 / π)1/2 x 2 = 129 cm
([2016 in.2] / π)1/2 x 2 = 50.6 in.)
Use 1.4-m (54-in.) diameter filter with the corresponding 1.5-m2 (15.9 ft2) sur-
face area.
C-1.6
Solids Loading to Upflow Continuous Backwash Filter. Calculate the sol-
ids loading to the continuous backwash filter: 50 mg/L (50 ppm).
solids loading = concentration x flow
50 mg/L x 106 kg/mg x 1.90 L/s x 86,400 s/day = 8.21 kg/day
(50 ppm x 8.34 x 106 [lb/gal.]/ppm x 30 gpm x 1440 min./ day = 18.06 lb/day)
C-1.7
Reject Flow and Sizing of Thickening Tank. Assume up to 0.32 L/s (5 gpm)
of reject flow rate. Reject flow can be split, with a portion returned to the equalization
tank and a portion flowing to the sludge thickening tank. To be conservative, size the
sludge thickening tank to accept the reject flow, 0.32 L/s (5 gpm). Assume that the op-
erator would split the flow to achieve optimal results. Pilot test data indicated up to 95%
filter removal efficiency (with polymer addition). From above, solids loading to the filter
will be.
8.21 kg/day x 95% efficiency = 7.80 kg/day
(18 lb/day x 95% efficiency = 17.1 lb/day)
Removal in the reject flow.
C-2
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