UFC 3-280-03
23 JULY 2003
Pumping rate for each pump when 3 filter units are operating = [54,600 L/s] / [(3 pumps) x (4
cycles/day) x (6000 s/cycle)] = 0.76 L/s (12 gpm)
Therefore, the total minimum pumping capacity for each operating and
standby pump is 0.76 L/s (12 gpm) at a filter press pressure of 690 kPa (100 psig)
(maximum pressure condition specified). However, prior to selecting the appropriate
pump, any additional system head losses, in addition to safety factors, should be
determined and combined with the required filter press pressure to determine the
overall head requirements. Once this is done, manufacturers' catalogs should be
obtained and an appropriate pump selected.
5-2.3.4
Sludge Cake.
5-2.3.3.1 Compute the Total Sludge Dry Cake Solids. The filter cake contains sludge
solid, lime, and ferric chloride. This example will assume that 100% of the condition
chemicals are incorporated into the sludge cake and that the dewatering facility
provides 98% solids capture.
Sludge solids in cake = 0.98 x 1060 kg/d = 1039 kg/d
Lime solids in cake = 1.00 x 106 kg/d = 106 kg/d
Ferric chloride in cake = 1.00 x 53 kg/d = 120 kg/d
Total dry solids in sludge cake = 1198 kg/d ~ 1200 kg/d (2640 lb/d)
5-2.3.3.2
Compute the Volume of Sludge Cake and Required Storage. The wet
sludge cake has a bulk density of 1,280 kg/m3 (80 lb/ft3). This example will assume that
the sludge will be discharged directly into a hopper for direct dumping into transport
trucks for offsite disposal and a 4-day volume of sludge cake storage will be provided
(GLUMRB 1900).
Volume of the sludge cake generated each day:
[(1200 kg/d)] / [(1280 kg/m3) x (0.30)] = 3.1 m3/d (110 ft3/d)
Volume of sludge cake storage required per press:
[(3.1 m3/d) x (4 d)] / [3 filter press] = 4.1 m3/press
Therefore, the volume of the storage receptacle for each of the three
operating presses will be 4.1 m3 (150 ft3).
5-2.3.5 Filtrate Quality. The filtrate generated in the sludge-dewatering process shall
be discharged into a sump with a 1-day capacity of filtrate or combined with other
treatment process overflow streams. A portion of this filtrate may then be either used in
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