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FW: metal finishing question

There are a number of ways to reduce rinse volumes, starting with dragout reduction and going to adding rinse cascades and flow control ( generally based on conductivity) and using high quality water like DI as feed.
This may allow them to closed-loop more economically or evaporated.

However, the state regulatory authority needs to be consulted.  In Minnesota, if a metal finishing operation is present (or any other categorical discharge source) and there is any other industrial discharge to the sewer (such as washing floors), the pretreatment standard applies even if the metal finishing operation itself does not discharge.  The presumption is catigorical wastes could make it to the sewer by accident, malfunction or malfeasance.  If this is the case with this facility, P2 efforts may be desirable and may pay back, but they would not have any regulatory relief benefit.

Karl DeWahl

-----Original Message-----
From:	Catherine Dickerson 
Sent:	Monday, January 31, 2000 2:01 PM
To:	'p2tech'
Subject:	metal finishing question

Hi folks,

I have a question about P2 options for a metal finishing process, and thought I might be able to get some help from other p2ers out there.  A small metal finishing business is process wastewater to the city's wastewater system.  The metal finisher is the only discharge the city gets that makes them subject to national pretreatment standards.  Both the city and the company would like to avoid being subject to those standards, and is looking for a (cost effective) P2 solution.  Some of the details:

The company discharges industrial process wastewater to the city as a way to dispose of rinsate from normal business operations.  The coating processes are small operations: a worker lowers a basket of parts into a coating tank using an overhead wench on a sliding track, then raises the basket, moves it to a rinse tank, lowers it into the rinse, raises it, then moves it to the final rinse tank.  For both lines (phosphorous and chromate conversion coating processes - no electroplating involved) there is a continuous rinse discharge from the rinse tanks.  There are four rinse tanks, two for each line.  If both lines and all rinse tanks are in operation at the same time, then the discharge to the city is about 10 gallons per minute; or about two-and-a-half gallons per minute per tank.  That is the maximum amount of flow from industrial processes that would be expected to be discharged to the city.

Has anyone else out there dealt with such a situation?  Is there a feasible cost-effective approach?  One gentleman we've spoken with has said the capital costs of implementing a closed-loop system make the payback period prohibitively long.  Any thoughts/leads (as always) are appreciated.


Catherine M. Dickerson
Technical Lead
Pacific Northwest Pollution Prevention Resource Center
1326 Fifth Avenue, Suite 650
Seattle, WA 98101
Phone:  206-223-1151
Fax:  206-223-1165
email:  cdickerson@pprc.org
Check out our website:  http://www.pprc.org