UFC 3-280-04
17 DEC 2003
further guidance on acceptable hydraulic loading rates for an influent stream with a
given total suspended solids concentration and solids size and density. Using the plant
flow and the hydraulic loading, the designer can determine the filter area as:
Filter area [ft2 (m2)] = plant flow [L/s (gpm)] / hydraulic loading [L/s m2 (gpm/ft2)]
Once the required filter area is determined, the filter may be selected. Table 8-2 shows
typical sizes available and the requirements for tank size, reject percentage, air flow and
media for the appropriate filter.
Table 8-2. Continuous Backwash Filter Application Guideline
Water Treatment
Loading Rate
Maximum Inlet
Expected
Applica-
(gpm/ ft2)
Application
Solids
Effluent Solids
ble
(mg/L)
(mg/L)
Particle
Size
(microns)
Surface water
26
10100 NTU
0.10.5 NTU
912
Tertiary filtration
35
150
< 510
912
Phosphorous removal
35
10 (as P)`
< 0.3
912
Pulp and paper
35
100
5 10
912
effluent
Metal finishing
36
200
25
912
Mill scale
812
500
510
912
Oily wastewater
26
200 (free oil)
510 (free oil)
912
Algae removal
24
100
1020
912
8-3.5
Cartridge and Bag Filters. Summarized below is a general approach to de-
signing cartridge and bag filters. The design approach assumes that cartridge or bag
filtration has already been selected. Many of the steps necessary in selecting cartridge
or bag filters and the hardware for housing them are the same. Where there are differ-
ences, it will be noted in the text.
8-3.5.1 The first step in selecting a cartridge or bag filter is to identify the contami-
nants present in the waste stream and identify filter materials of construction that are
compatible. This is done by comparing the waste stream components to vendor sup-
plied compatibility charts. The filter components that need to be checked for compatibil-
ity are the filter media, support core or outer cage and o-rings, or all three. Several ma-
terials of construction may be suitable. Alternatively, some vendors suggest conducting
your own chemical resistance test. One procedure is outlined below.
8-3.5.1.1 Immerse a cartridge or bag filter of the desired micron rating in the fluid to be
treated and at the desired operating temperature for at least 48 hours.
8-3.5.1.2 Examine the cartridge for any change in color, structural integrity, swelling,
softening, deformation, or any other physical changes.
8-7
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