MIL-HDBK-1005/9A
Specify performance of DAF or IAF unit to include oil
removal efficiency and effluent oil concentration at expected
unit operating conditions (air, solids, hydraulic loading,
pressure, and detention period) with or without chemical
addition.
3.10.6.3 Chemical Conditioning. Chemical aids, or coagulants,
are used to allow individual droplets of emulsified oil to
agglomerate into a larger floc, which is more easily separated
from the water. Materials used as coagulants include alum,
ferric chloride, sulfuric acid, lime, organic polyelectrolytes,
and combinations of inorganic and organic polyelectrolytes.
Organic coagulants generally produce a better quality effluent,
often require lower dosages, and reduce the amount of sludge
generated by 50 to 75 percent. Bench scale studies should be
performed to identify the optimum coagulant or combination of
coagulants and determine dosage rate. (Refer to paragraph 3.10
for a detailed discussion of treatment chemicals.)
3.10.7
Polishing Treatment Alternatives. The purpose of the
polishing step is to reduce the oil content to less than 10 ppm
so that the effluent may be discharged to navigable waters.
Multimedia filtration followed by activated carbon adsorption
are the most practical processes. Coalescing filtration units
require less surface area per increment of flow capacity and may
be preferred for site-specific land constraints. This may be
especially true in colder climate areas where much of the
treatment system equipment will be installed indoors and
building size must be minimized. Since the polishing step is
critical to meeting effluent requirements, duplicate units for
100 percent redundancy must be provided.
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