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Re: Flammable sand trap waste

Seems like I've heard of advanced oil/water separators being used for
this.  The simpler, smaller units aren't expensive.  Try asking a vendor
about it -- I recommend Richard Brinks of Great Lakes Environmental at
708/543-9444.  He'd be able to tell you if the water could meet discharge
or reuse requirements.  A lot would depend on how soluble in water the
organics are, but there are ways to get around that to a certain extent. 
The organic layer and settled solids would still need to be disposed of,
so methods of reducing their quantity should be pursued, like sweeping,
fleet maintenance, separating exterior wash streams from engine wash
streams...  Do these facilities already use countercurrent flows, so that
final rinse water is used as wash water, etc? 

Kirsten Sinclair Rosselot, P.E.
Process Profiles
P.O. Box 8264
Calabasas, CA 91372-8264


> A fellow MPCA staffer has asked me to post the following query.
> The most environmentally benign method of dealing with flammable sand
> trap wastes needs to be worked out.  Flammable sand trap waste are
> typically generated when the waste water from vehicle engine washing
> operations (ranging in size from mom and pop car washes to vehicle
> fleets) flows to a floor drain where it is collected in a holding tank.
> The material is then typically comprised of three-phases: a LNAPL phase,
> dirty water, and a sand layer.
> The LNAPL phase can be blotted off with absorbent pads and shipped off
> by a waste oil hauler.  The sand can be dewatered, and in many instances
> be taken to a permitted landfill (if no liquids).  It is however
> difficult to deal with the remaining dirty water (containing metals and
> NAPLs).  On-site pretreatment of the dirty water would appear to be
> pretty expensive.  
> Many smaller outstate (non-metro) waste water treatment facilities
> (WWTFs) are reticent to take it because it may upset their plant, they
> may be already close to their discharge limits, or they don't want to
> take such liquids if not in their billing area.
> Closed loop recirculation of the dirty water has been suggested as a
> means of P2.  If you know of any methods of P2 for the dirty water or
> dealing with flammable sand trap wastes as a whole please let me know.
> Thanks!
> Al Innes
> Minnesota Pollution Control Agency
> 520 Lafayette Road North
> St. Paul, MN  55155-4194
> 612-296-7330
> alister.innes@pca.state.mn.us