UFC 3-280-03
23 JULY 2003
5-3.1.3 A variable-volume recessed plate filter press will be used for this example.
Typical ranges of design criteria for this type of filter press are presented in Paragraphs
2-3 and 2-4.
5-3.1.4 This example will assume that treatability testing has been done and the
following design data were obtained:
5-3.1.4.1 Sludge Cake Characteristics.
Cake thickness = 32 mm (1.25 inch)
= 1120 kg/m3 (70 lb/ft3)
Wet cake density
5-3.1.4.2 Optimum Chemical Conditioning.
Lime dosage (CaO)
= 5 % of dried solids by weight
Organic polymer
= 2 % of dried solids by weight
5-3.1.4.3 Dewatering Equipment Requirements.
Operating time = 8 h/d, 5 d/wk
Cycle time
Feed
= 20 min (1200 s) at 345 kPa (50 psig)
Compression
= 15 min (900 s) at 1550 kPa (225 psig)
Cake discharge
= 25 min (1500 s)
Total
= 60 min (3600 s) or 8 cycles/d
5-3.1.5 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 removal and sludge cake management systems.
5-3.1.6 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.
5-3.2
Design Calculations.
5-3.2.1
Determine Required Filter Volume.
5-3.2.1.1 Compute Total Daily Sludge Solids Generation Rate.
5-11
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