23 JULY 2003
Daily sludge solids generation rate = [(80,000 L/d) x (0.05) x (1.0) x (1 kg/L)] = 4000 kg/d (8800
lb/d) dry solids
5-18.104.22.168 Compute Total Dry Solids Processed per Day of Filter Operation.
Total dry solids dewatered = sludge + lime + polymer
Sludge solids = [4000 kg/d x 7 d/wk]/[5 d/wk (operation)]= 5600 kg/d
Lime (CaO) = 5600 kg/d x (0.05) = 280 kg/d
Polymer = 5600 kg/d x (0.02) = 112 kg/d
Total dry solids per day = 5992 kg/d ~6000 kg/d (13,200 lb/d)
5-22.214.171.124 Compute filter volume required per cycle.
Filter volume per cycle = [6000 kg/d] / [(8 cycle/d) x (1120 kg/m3) x (0.25)] = 2.7 m3 (95 ft3) of
Selection of Efficient Filter Press Unit.
5-126.96.36.199 Determine the Pressure Filter Sizes Available. Examine the manufacturers'
catalogs to determine the sizes of various filter units. Tabulate the filter area available
with and without the single largest unit. See Table 5-2.
5-188.8.131.52 Select Proper Filter Press Unit. The most efficient and manageable filter
unit assembly is the one that has the fewest operating units and provides nearly 100%
operating capacity when one unit is out of service, and about 25% extra capacity when
all units are in operation. Based on this method, the proper unit selected from Table 5-2
would be Item D. This selection has a total of five units, including four operating units
and one standby unit. This assembly will provide 104% of the design daily requirement
when one unit is not operating, and about 133% of the design daily dewatering capacity
when the standby unit is in operation. Although Item C has the same number of units
and has the same overall operating capacities, this selection is the maximum capacity
of this size unit and would not allow for additional future capacity, if necessary. A typical
schematic layout of the filter press units and supporting equipment is presented in
Although the method presented provides a direct approach for selecting the
optimal size and number of required presses, an economic and technical evaluation of
several alternatives that achieve the minimum requirements should be considered prior
to the final selection. For example, by comparing different alternatives in Table 5-2, Item
C and Item D are both similar for the number of units and operating capacities.
However, although Item C is at its maximum size, it has some additional capacity (i.e.,
105%) and would less expensive than Item D and may be suitable if no additional
capacity is required.