UFC 3-280-03
23 JULY 2003
Volume of the sludge cake generated on a daily basis = [(5620 kg/d)] / [(1120 kg/m3) x (0.25)] =
20 m3 (710 ft3/d)
Volume of sludge cake storage required per press = [(20 m3/d) x (4 d)]/[4 filter press] = 20
m3/press
Therefore, the volume of the storage receptacle for each of the four operating
presses will be 20 m3 (710 ft3).
5-3.2.5 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
the filter dewatering process for sub-cycles, such as filter media precoating, or returned
to the headworks of the treatment process with the remaining filtrate.
5-3.2.5.1 Compute Volume of Filtrate.
Filtrate volume = 112,000 L/d [(20 m3/d) x (1000 L/m3)] = 92,000 L/d
Water in lime solution = 2800 L/d
Water in polymer solution = 2240 L/d
Total of return flow = 97,040 L/d (25,600 gpd) or 1.1 L/s (18 gpm)
(Note that in addition to the items listed above, additional process water used in the
dewatering system, such as water needed for filter media washing, cake extraction, and
diaphragm losses, will need to be considered. However, these quantities are specific to
the dewatering equipment selected and are not included for this example.)
5-3.2.5.2 Compute Total Solids in the Return Flow.
Total solids in conditioned sludge = 5990 kg/d
Total solids in sludge cake = 5620 kg/d
Difference total solids in return flow = 370 kg/d (815 lb/d)
Therefore, the sump for this example should be sized to store 97,100 L or 97
3
m (25,600 gallons) based on 1 day of storage.
5-3.2.6 Design Details. A diagram of the design of the filter press assembly is pre-
sented in Figure 5-2.
5-4
DESIGN EXAMPLE NUMBER 3. This paragraph provides a preliminary
design example assuming that both chemical (metal hydroxide) and biological sludge
are generated from a contaminated water source. This example is limited to the selec-
5-19
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