UFC 3-280-04
17 DEC 2003
C-2.3
Establish Effluent Requirements and Confirm Need For Filtration. When-
ever the effluent suspended solids requirement is 30 mg/L or above, consider use of
sedimentation in lieu of filtration; this gives the same effect with less maintenance. Con-
sider what the effect on the suspended solids may be. From experience at other sites
and discussions with filter suppliers, install a downflow continuous backwashing filter to
prevent exceeding the suspended solids limit.
Table C-2. Suspended Solids Removal Requirements
at 12 L/s (190 gpm) = 1,036,800 L/day (273,900 gpd)
Effluent Standard
Influent
Removal Requirement
mg/L
10
100
90
90%
kg/day
10.368
103.680
93.312
90%
lb/gal.
0.000083
0.000834
0.00075
90%
lb/day
22.86
228.56
205.7
90%
C-2.4
Develop the Design Basis. Conversion units for filter loading
1 L/m2s = 1.473 gpm/ft2
1 gpm/ ft2= 0.679 L/m2s
Table C-3. Performance Capabilities
Particle
Application
Loading Rates
TSS [mg/L]
Sizes
[L/m2 s]
[gpm/ft2]
[microns]
Influent
Filtrate
Algae removal
912
22.7
34
20150
120
Metal
912
24
36
20100
25
hydroxides
Mill scale
912
27.5
311
20250
510
Phosphorus
912
23.4
35
20100
510
removal
10100
0.10.5
Surface water
912
24
36
[NTU]
[NTU]
direct filtration
Tertiary filtration
912
23.4
35
20150
110
Reference: Vendor B internet catalog
Determine filter size based on flow rate and hydraulic loading. Select a load-
ing rate for preliminary design. Table C-3 gives generally acceptable loading rates listed
by Vendor B for selected water treatment applications. For the applications given, the
maximum hydraulic loading varies from 2.7 to 7.5 L/m2s (4 to 11 gpm/ft2); the minimum
hydraulic loading is 2 L/m2 s (3 gpm/ft2) for all, with a typical rate of 4.1 L/m2s (6
gpm/ft2). Relatively little flexibility is available in sizing the unit because continuous
C-8
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