UFC 3-280-03
23 JULY 2003
5-2.2.4.3 Dewatering Equipment Requirements.
Operating time = 8 hours/day, 5 days/week
Cycle time (variable flow/pressure system)
Feed
= 30 min (1800 sec) at 172 kPa (25 psig)
Feed
= 30 min (1800 sec) at 345 kPa (50 psig)
Feed
= 30 min (1800 sec) at 517 kPa (75 psig)
Feed
= 1 min (60 sec) at 690 kPa (100 psig)
Cake discharge = 29 min (1740 sec)
Total
= 120 min (7200 sec) or 4 cycles/day
5-2.2.5 The filter press system will be housed inside a building that shall include the
sludge storage tanks, sludge transport equipment (i.e., pumps), chemical conditioning
tanks, chemical feed equipment, chemical storage, plate and frame filter press assem-
bly, and filtrate and sludge cake management systems.
5-2.2.6 The number of filter press units will be selected such that 100% of the design
liquid sludge flow rate is filtered when the largest single unit is out of service as
described in Subparagraph 2-7.3.2.1. This example will also assume that the maximum
filtration capacity shall be 125% of the design capacity when all units are in operation.
Any additional specific optional features or supporting systems (i.e., precoating, air
blowing, and filter media wash systems) and associated sizing requirements will be
determined once the filter press has been selected.
5-2.3
Design Calculations.
5-2.3.1
Determine Required Filter Volume.
5-2.3.1.1 Compute total daily sludge solids generation rate.
Daily sludge solids generation rate = [(37,850 L/d) x (0.02) x (1.0) x (1 kg/L)] = 760 kg/d (1670
lb/d) dry solids
5-2.3.1.2 Compute total dry solids processed per day of filter operation.
Total dry solids dewatered = sludge + lime + ferric chloride
Sludge solids = [760 kg/d x 7 d/wk] / [5 d/wk (operation)] = 1064 kg/d
Lime (CaO) = 1064 kg/d x (0.10) = 106 kg/d
Ferric chloride = 1064 kg/d x (0.05) = 53 kg/d
Total dry solids per day = 1223 kg/d ~1230 kg/d (2700 lb/d)
5-2.3.1.3 Compute filter volume required per cycle.
5-3
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