(3) Inlet Screens. Provide basket or bar type
screens on a pump inlet which can be removed and cleaned at the
surface without personnel entry.
b) Pump Selection. Determine pump capacity and
operating cycle as in paragraph 2.4. Use positive displacement
pumps with pressure relief valve, rather than centrifugal pumps,
to reduce mechanical formation of emulsion at oily waste
treatment plants. Pumps should pass solids having a diameter
0.125 inches (3 mm).
c) Pump Controls. Provide controls suitable for Class
I, Division 1, Group D safety classification. Use float or sonic
type mechanisms, not air bubblers, for pump control and alarm.
Provide discharge pump control valve to minimize surge effect on
equalization basins at oily waste treatment plants (not
applicable for positive displacement pumps). Provide an alarm
system for overflow or power failure. Provide manual override of
pump controls but not of low level alarms.
d) Metering. Specify the following to monitor station
activity: accumulating flow meter, elapsed time meter for pumps
and ventilator, and pump suction and discharge pressure gages
with oil-filled diaphragm and cutoff valves.
3.9
Oily Wastewater Treatment
3.9.1
General. No single treatment process or commercial
device will remove all forms of oil (emulsified, free or
dissolved) in oil-water mixtures. A series of treatment process
units may be utilized to achieve the desired effluent quality.
The degree of treatment required will be based on the most
applicable discharge limit for a POTW or navigable water. Select
oily wastewater treatment options from those presented in Table
13. In addition, sludge treatment and disposal must be
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