MIL-HDBK-1005/16
of the separator. Therefore, the design flow should be based on
the maximum flow rate to be treated, including the addition of
any future oily wastewaters and stormwater runoff. In
determining peak flow rates, variations between shifts and daily
and seasonal variations should be considered. Flow rates should
be measured where the wastewater generating process already
exists, or accurately estimated where it does not.
In some cases, establishing production-based wastewater
generation rates may be useful for projecting future flows. For
example, the maximum flow expected from an aircraft washing
facility may be estimated from the expected washwater per
aircraft multiplied by the maximum number of aircraft to be
washed in a given period. If unit wastewater generation rates
from another facility are used, differing conditions should be
accounted for, such as differences in the type and size of
aircraft and washing procedures.
Where high flows of short duration are to be handled,
an alternative to constructing a larger separator is to separate
or divert extraneous flows from the system. For example, an
outdoor washrack could be curbed and provided with a manually
controlled valve to allow storm runoff to be diverted to a
separate drain during rainfall periods. In general, flow
equalization upstream of an OWS is beneficial where the OWS would
otherwise experience slug loads.
5.6.4
Design Criteria for Conventional Separators. The
following parameters should be considered in the design of
conventional OWSs:
a)
Design flow
b)
Minimum wastewater temperature
c)
Wastewater specific gravity
d)
Wastewater absolute (dynamic) viscosity
e)
Wastewater oil-fraction specific gravity
f)
Minimum globule size to be removed, usually
150 microns
g)
Type and amount of detergents present in the
wastewater and potential changes in future detergent use
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