[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: metal finishing question
While I was working for the city of Palo Alto's wastewater program we
did a lot of work with metal finishers. A couple of smaller shops
(perhaps a bit smaller than the shop you described) chose to go to zero
discharge because it was so much cheaper for them to get out of the
regulatory loop. Information on the projects they implemented is at
http://www.city.palo-alto.ca.us/cleanbay/publications.html (look under
industry). You may find the "reasonable control measures" information
prepared by consultant Tom Barron to be especially valuable.
Typically, we found that eliminating sewer discharge worked if a three
step process was implmented:
(1) reduce wastewater flows by using techniques like counter-current and
spray rinsing that reduce the need for fresh water. If they aren't
doing this now, they could easily see a 50% or greater flow reduction
without changing their existing tank configuration.
(2) reduce the facility's waste of plating chemicals (which keeps these
chemicals out of the wastewater, reduces need for fresh water for
rinsing, and reduces treatment costs) through techniques such as use of
drag-out tanks or drain boards
(3) treat remaining (much smaller) flow for re-use. In most cases, it
was significantly cheaper for the firm to remove some small amount of
residual for off-site metals recycling or disposal as hazardous waste
than it was to eliminate all releases.
In case you don't think this is possible, I should tell you that one
shop we were all sure was going to go out of business went to a local
hardware store and reconfigured its plating operation using off the
shelf items (e.g., garden hoses with spray nozzles for spray rinses) and
went to zero discharge. We were very impressed--and they are still in
business, several years later.
Catherine Dickerson wrote:
> 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: firstname.lastname@example.org
> Check out our website: http://www.pprc.org