17 DEC 2003
3-1.5.2 Adsorption can be particularly sensitive to solids in the waste stream. Adsorp-
tion works by allowing the waste stream to come in contact with an adsorption medium,
such as activated carbon, which adsorbs dissolved contaminants onto its surface. In this
case, some manner of filter before the adsorption unit is generally recommended when-
ever suspended solids exceed 50 mg/L (Process Design Manual for Suspended Solids,
Removal, U.S. EPA, 1975. See also EPA 832-F-00-017,
3-1.5.3 In other applications, a waste stream may require oxidation prior to ultimate
discharge. Because the oxidant works by reacting with organic matter, its ability to react
with harmful bacteria can be hampered by the presence of biological solids in the waste
stream. Filtration to remove larger solids prior to oxidation may improve the effective-
ness of the oxidation process, conserve the oxidant, and prevent excessive amounts of
byproducts from forming. Advanced oxidation requirements may also require solids re-
moval from the waste stream as an intermediate step.
3-1.5.4 In another scenario, solids in the waste stream may affect disposal options,
possibly causing the waste stream to be considered a hazardous waste or to contain
metals at levels higher than can be discharged to the sanitary sewer system. In this
case, filtration may be included as an intermediate step in the treatment process.
Post-Treatment Filtration. Some applications require filtration as a last step
prior to discharge. In this case filtration may be a polishing step needed to meet Na-
tional Pollutant Discharge Elimination System (NPDES) permit limits or permit equiva-
lence for discharge to a surface water or underground injection control (UIC) require-
WASTE STREAM PARAMETERS. When designing a filtration system, the
design professional should first understand the nature of the waste stream being treated
and the treatment needs. Specific factors that should be considered are:
Treatment flow rate.
Objective of solids separation.
Continuous or batch operation.
Recovery or disposal of captured solids.