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Where to find info on older technologies for Chromium removal from wastewater

May 10, 2012

Q. My company currently has a waste water system, but it seems to be managed by tribal knowledge and not science. I am having trouble getting an engineering evaluation paid for. We are attempting to lower the total Chromium levels to <5 ppm for permit purposes.

Our materials are: holding tanks, sodium bisulfite, clay, sulfuric acid, and sodium hydroxide. From what I can tell, the process involves dropping the pH in the presence of the bisulfite, taking the pH back up to about 8, and running the resultant water through clay socks. We test the water for total chromium after this, and if the wastewater is now at <5 ppm total Cr, we release it.

I imagine this is an older technology, for which I am having trouble getting information.

Can anyone point me to a resource for this?

Thanks very much,

Stephen T [last name deleted for privacy by Editor]
- Nashville, Tennessee

May 11, 2012

A. Hi, Stephen. A book which describes these older standard technologies in good depth is Clarence Roy's "Operation and Maintenance of Surface Finishing Wastewater Treatment Systems" [affil. link to book on Amazon]. But if I were you, I think I'd absolutely insist on that engineering evaluation. Please realize that some person is legally responsible for compliance with all federal and local laws for effluent, solid waste management, etc.

I know two men who served hard time (actual penitentiary time) for environmental issues in plating shops. Obviously, those are extreme examples, and I'm not suggesting that small accidental missteps will earn anyone a felony conviction -- rather, I'm just emphasizing that environmental compliance is not something where budgetary constraints will be accepted as an excuse.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

June 25, 2012

A. I second that about insisting on an engineering evaluation because I do not believe that Trivalent chrome will precipitate completely with that low of a pH

Scott Merritt
- Eastman, Georgia, USA

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