MIL-HDBK-1005/16
Some factory manufactured OWSs are designed with
emulsion breaking chambers where chemicals are added and mixed.
Otherwise, emulsion breakers should generally be added to the
wastewater as far upstream of the OWS as practical. Further
guidance in the treatment of emulsions is given in API
Publication 421.
5.5.3.3
Mechanical Impingement and Filtration Processes. Other
methods for removing emulsified oil include mechanical
impingement devices and filtration. Representative of the former
are the so-called coalescing filters and the cartridge-type
emulsion breakers that are used as the final step in the Fram
oily water separation system (following solids filtration or
sedimentation and free oil removal). The Fram type cartridge
unit contains a medium containing numerous small (25 microns),
irregular, continuous passages through which the wastewater
flows. The emulsion is broken by impingement of the oil droplets
on the surface of the medium. The cartridge can be backwashed
and/or replaced. Coalescing-type separators are recommended only
for light oil loadings when a higher level of oil removal is
required, the wastewater stream contains minimal solids
concentrations, and the facility is committed to the additional
maintenance procedures required to keep the unit free of debris.
Pressure filters may also be used to remove dilute
concentrations of mechanically emulsified oil, usually as a
polishing step downstream of gravity or flotation units.
Activated carbon, other proprietary solid phase sorbents, or
bentonite clay/anthracite are typically used as the media.
Application of filters at military installations is expected to
be extremely rare, so the design of these units is not covered
herein.
5.5.4
Treatment of Dissolved Oil. Treatment of dissolved oil
is also not normally practiced at military bases. Dissolved oil
that might be present would be expected to be removed by the
biological treatment processes employed by the FOTW or POTW to
which the wastewater is discharged. Where pretreatment of
dissolved oil at an upstream location is required, adsorption
would be the probable method of choice. There are other
treatment technologies such as membrane filtration and advanced
oxidation techniques, but these technologies are rarely cost
effective compared to adsorption or biological treatment.
5.6
Design of OWSs. Design of conventional and parallel-
plate OWS systems requires proper characterization of the
wastewater, establishment of the design flow, sizing of the
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