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RE: Water Pollution Reduced Metrics



Tara,

I'm curious as to how a facility can measure solvent discharge in gallons and
then have it show up in their wastewater discharge. Such volumetric
measurement implies that it is held in a tank that is dumped when dirty. If
so, they shouldn't be dumping this tank to sewer. 

If the solvent is held in a tank and the wastewater discharge is from rinsing
the cleaned parts, then the gallon estimate is only a guess. They could be
reporting clean solvent added to the tank minus the dirty solvent drummed for
disposal as the amount that is going to sewer. This will yield a very rough
estimate since it does not account for solvent evaporation from the tank or
the build-up of dirt in the bath.

Given the rough accuracy of the estimated gallon value, using an approximate
density value to convert to pounds is not going to make a big difference for
tracking long-term trends. You just need something in the ballpark and you
need to be consistent in the use of your conversion factors. For solvents,
the way in which you account for evaporative loss will most likely have a
much greater impact on overall accuracy than the value you use for density
(assuming you track the lighter than water hydrocarbon-based solvents
separately from the heavier than water halogenated solvents). Good luck.

Mike Callahan, PE
Jacobs Engineering
1111 S. Arroyo Parkway
Pasadena CA 91105
Business: (626) 568-7005
Fax: (626) 578-3550


-----Original Message-----
From: owner-p2tech@great-lakes.net
[mailto:owner-p2tech@great-lakes.net]On Behalf Of
Ohare.Tara@epamail.epa.gov
Sent: Wednesday, May 18, 2005 1:47 PM
To: P2tech@great-lakes.net
Subject: Water Pollution Reduced Metrics


I have a question about how to define metrics for water pollution
reduced.  We have been currently measuring water pollution reduced in
pounds, but we have a situation where a company has reduced the
discharge of a solvent which is measured in gallons.   We are struggling
to determine how to capture this and still be consistent with our
current metrics definitions.  We considered converting the gallons of
the solvent into pounds, but the type of solvent and concentration will
probably be different with each application making conversions
difficult.

What is the best way to capture the amount of reduction of these
solvents in water?

Tara O'Hare
U.S. EPA
1200 Pennsylvania Ave. NW
Room 5303MM, MC 7409-M
Washington, DC 20460
202-564-8836

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