UFC 3-280-03
23 JULY 2003
5-4.2
Design Calculations.
5-4.2.1
Determine Required Filter Volume.
5-4.2.1.1 Metal Hydroxide Sludge.
a. Compute total daily sludge solids generation rate. Determine the daily sol-
ids flow rate:
[(Influent flow rate) x (total solids to be removed)] = [(6.3 L/s) x (70 mg/L)] x [(106 kg/mg) x
(86,400 s/d)] = 38 kg/d (84 lb/d) dry solids
Total sludge flow rate is as follows:
[(Solids flow rate)/(Solids in Feed)] / [Density of Sludge] = [(38 kg/d)/(0.01)] / [1 kg/L] = 3800 L/d
(1000 gal/d)
b. Compute total dry solids processed per day of filter operation.
Sludge solids = [38 kg/d x 7 d/wk] / [5 d/wk (operation)] = 53 kg/d
Polymer = [168 kg/d x 0.02] = 1 kg/d
Total dry solids per day (sludge + polymer) = 54 kg/d (120 lb/day)
c. Compute filter volume required per cycle (assume a minimum of one cycle
each day).
Filter volume per cycle = [54 kg/d] / [(1 cycle/d) x (1200 kg/m3) x (0.30)] = 0.15 m3 (5.3 ft3) of
sludge/cycle
5-4.2.1.2 Biological Sludge.
a. Compute total daily sludge solids generation rate.
Total sludge flow rate = 10,900 L/d
b. Determine the daily solids flow rate.
[(Influent sludge flow rate) x (solids in feed)] = {(10,900 L/d) x [(0.02) x 1 kg/L]} = 220 kg/d (480
lb/d) dry solids
c. Compute total dry solids processed per day of filter operation.
Sludge solids = [220 kg/d x 7 d/wk] / [5 d/wk (operation period)] = 308 kg/d
Lime = [308 kg/d x 0.30] = 92 kg/d
Total dry solids per day = sludge + lime = 400 kg/d (880 lb/day)
5-22
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