MIL-HDBK-1005/16
c)
Effluent Chamber. The effluent chamber is also
separated from the main chamber by upper and lower baffles.
Wastewater flows under and over the baffles into the effluent
chamber. From the effluent chamber, the treated water can be
discharged to the sewerage system or to additional treatment if
necessary.
5.5.1.2
Parallel Plate Separators. A typical parallel plate
separator system is shown in Figure 12. Parallel plate
separators function on the same principles as conventional
gravity separators, but they require less space and are
theoretically capable of achieving lower concentrations of
effluent oil. The size of the unit is reduced by incorporating
an array of closely spaced parallel plates within the separator
chamber, thereby increasing the surface settling area. Flow
through a parallel-plate unit can be two to three times that of
an equivalently sized conventional separator. The oil is removed
by passing the wastewater at laminar velocity through the pack of
closely spaced plates, which are constructed at various inclines
ranging from 45 to 60 degrees. These oil droplets rise and are
trapped along the bottom of the plates. The oil droplets
coalesce and gradually move upward along the bottom of the
plates, eventually collecting at the surface of the tank. The
plates aid in separation in the following ways:
a)
Preventing short-circuiting of the oily waste
b)
Increasing effective settling area
c)
Enhancing contact/agglomeration of oil particles
Suspended solids settle to the bottom and are collected
in a sludge well. From the well, sludge is pumped or withdrawn
by gravity to waste. If sludge transfer is by gravity
displacement, an automatic valve is usually provided. The plates
in parallel-plate separators may be made of an oleophilic (oil
attracting) material, such as polypropylene, fiberglass, or
nylon, to promote coalescence of oil droplets. For this reason,
the units are sometimes referred to as coalescing plate
separators. Coalescing separators are usually 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 coalescing pack free
of debris. The plates may also be constructed in a corrugated
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