The U.S. Environmental Protection Agency (EPA) is initiating a peer review of draft scientific modeling approaches to inform EPA’s evaluation of...
Traditionally, the separations process was one which involved frequent and often complicated maintenance. Wastewater Diversion Systems, Inc. of Mechanicsville, Va., has developed and patented the FOX VGS (Vertical Gravity Separator) to remove free oil, grease and suspended solids from wastewater, while significantly reducing the frequency and difficulty of maintenance.
This separator features high efficiency, low cost oil water
separator technology that continuously meets the performance standards, is able
to handle high concentrations of oil, effectively removes the suspended solids,
reduces vapor content to acceptable levels, and requires less floor space.
The FOX VGS operates by control of both fluid velocity and
pressure, which gently coaxes non-emulsified impurities from water —
allowing high density contaminants to fall into a sludge retaining area and oil
droplets/low density suspended solids to rise where they float off into a
This separator is effective because the FOX VGS Skimmer skims
only a few millimeters from the surface of the oily water, dealing with the
most relevant fraction of liquid.
Often with conventional oil/water separators, cleaning can
be a messy process. Someone first has to remove the plates or filters, then use
a high pressure hose to wash them —with grease and oil everywhere.
However, with the FOX VGS, there is no lifting plates or
filters out, no filter disposal, no reblocking the system, and no oil and
grease splatter. The user simply turns a valve and is back in operation within
This separator is designed to operate efficiently. A pump
delivers oily water into the top of the main body via the inlet leg, flowing
down this central column before being redirected upward through the chimney of
the truncated conical spiral pack (SPAK).The oily water supply to the pump is
from either a skimmer or a fixed suction in the pit, depending upon the
application. At the top of the main body, free oil and suspended solids are
built up, eventually flowing out for collection and suitable disposal.
The partially cleaned water is directed to the outside
(perimeter) of the conical SPAK and follows a tortuous path while cascading
down and around the SPAK. If this fluid while passing down the main body
encounters a set of conditions where the density of the fluid below is greater
than itself, then this lower density (oilier) fluid is drawn preferentially up
the inside of the inclined coalescing surface of the SPAK and into the lower
pressure center (chimney). Here it co-mingles with the incoming fluid and is
thus redirected again to the top of the main body and the process is repeated.
As a result of this process, the lightest fluid phase is
trapped within the hydraulics of the FOX VGS. This “convection
current” is created and maintained within the SPAK by the density
variations down the fluid column and the upward flow of the incoming oily water.
At the point that the fluid is most free of oil droplets, then this
“cleaned water” will enter the outlet leg — flowing up and
out of the system — while the heavy solids will drop to the base of the
The depth of the separated oil and surface sludge trapped in
the top of the main body of the FOX VGS is regulated by adjustment of the
height of the “cleaned water” outlet. This level is set by rotation
of a T-Bar assembly (adjuster) at the time of startup or at anytime that the
flow rate through the VGS is varied.
Construction of the unit is such that the SPAK is hung from
a support plate which bears onto the top edge of the main body and is free to
revolve. This support plate also has paddles on its underside that protrude
into the oil and sludge phase. Because the conical SPAK forms a continuous
spiral, its rotation produces a violent pumping action of the internal fluids
and causes the surfaces to be cleaned of any sludge build up. The paddles fluidize any encrustation of the surface sludge and makes it
suitable for discharge with the oil.
Maintenance and cleaning requires about one minute. A worker
closes off the water outlet and, with fluid flowing into the separator, rotates
the SPAK counter clockwise for three revolutions to flush it. Oil, water and
surface sludge buildup will flow out of the oil outlet for collection. This
usually is the only action required to maintain optimum performance of the FOX
VGS. The frequency of this cleaning action depends on each application. Once
per month is suggested until experience dictates otherwise.
The trash basket will indicate that emptying is required if
inlet fluid is seen to flow over the top of the main body. This fluid is
contained by the top berm initially, and will enter the main body via the
hollow paddles. Build-up of any heavier sludge in the base of the main body may
be drained off through the bottom valve.
For further information, phone Wastewater Diversion Systems,
Inc. at 804-730-1280.