UFC 3-280-04
17 DEC 2003
APPENDIX B
DESIGN EXAMPLE: PRESSURE FILTER
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INTRODUCTION. This example is a groundwater remediation system consist-
ing of five recovery wells, each well yielding up to 0.378 L/s (6 gpm). The groundwater
is contaminated with volatile organic compounds such as 1,1,1-trichloroethane, 1,1-di-
chloroethane, trichloroethylene, 1,2-dichloroethene, and low concentrations of aldrin.
The groundwater also contains iron at 1.10 mg/L (1.10 ppm) and manganese at 0.12
mg/L (0.12 ppm). The chlorinated organic compounds will be removed by air stripping
followed by activated carbon adsorption, which will also remove the aldrin. The pres-
ence of iron and manganese in the groundwater can cause iron and manganese oxide
scale to form in the air stripping unit. In this design example, it is also assumed that the
groundwater contains 50 mg/L (50 ppm) of suspended solids. To prevent scale forma-
tion in the air stripping system and potential plugging of the carbon adsorption system
with iron and manganese oxides and suspended solids, a pressure filter with perman-
ganate oxidation was selected to remove the iron and manganese and suspended sol-
ids prior to air stripping and carbon adsorption. Before the design process is begun, it is
assumed that the designer would discuss the application with several pressure filter
manufacturers to obtain filter efficiency, loading rates, filter size, filter media, and other
design and operational parameters. The design example is based on information sup-
plied by a particular pressure filter manufacturer.
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PRESSURE FILTER DESIGN PARAMETERS
Flow: 1.9 L/s (30 gpm) total average flow from five wells.
TSS: 50 mg/L (50 ppm).
Manganese: 0.12 mg/L (0.12 ppm) influent (no effluent limit).
Iron: 1.10 mg/L (1.10 ppm) influent (no effluent limit).
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TREATMENT SYSTEM
Flow equalization.
Pressure filter, dual media anthracite and silica sand with potassium
permanganate addition for iron and manganese removal and polymer for stabilization of
chemical floc.
Air stripping for VOC removal.
Activated carbon for additional VOC and aldrin removal.
B-4
PRESSURE FILTER DESIGN BASIS. Design the system using a single pres-
sure filter. It is assumed that the groundwater extraction pumps can be taken off-line so
that maintenance can be done on the pressure filter (estimated 2 to 4 hours per month).
After consultation with several manufacturers, this design example will use a
loading rate for anthracite and sand media of 1.4 to 2.0 L/m2s (2.0 to 3.0 gpm/ft2) with a
maximum rate of 3.40 L/m2s (5 gpm/ft2).
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