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Chrome Treatment for disposal

I have 15 Gallons of chromic acid and want to know how to treat it for disposal. I work in a small silver plating shop and don't deal with any chrome, so this is a new one for me. I have a fairly modern water/waste treatment facility, but was worried the chrome would disturb it. Any suggestion appreciated.

Jon Diamond
silver plater - Berkeley, California
2003

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There are certified haulers/treatment facilities that can take this 15 gallons off your hands. That will be less expensive than running it through your system, and then having to have 15,000 gallons hauled and treated :-)

Chrome is not particularly difficult to treat, but it is different. In theory you reduce the hexavalent chrome to trivalent with a reducing agent like sodium metabisulphite, monitoring the process with an ORP meter and by eye (the solution will be blue-green rather than amber when the hex-chrome is gone). Then you precipitate it by raising the pH. But chrome is toxic and a powerful oxidizing agent, bisulphite is a strong reducing agent that gasses toxic sulfur dioxide when at low pH, and the chrome precipitate is slimy and difficult to filter. All in all, a somewhat dangerous thing to experiment with, with a lot of potential for messing up your system.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

I agree. Any hexavalent chrome solution of greater concentration than a dragout rinse is not practically treated at any but the largest facilities, although shops that produce a lot of chrome-bearing rinse water routinely treat it easily. If the chromic acid you have is still in it's container and commercially useful, consider finding a chemical trading post whereby companies make chemicals they no longer want available to others that can use them. Everybody's happy! Some states have them.

Pete Blunk
- Seattle, Washington
July 4, 2008

I have been treating chrome now for 10 years, IE, chromic acid, Alodines, and deox baths. I have made my own solution for treating chrome. It is composed of approx. 5 different chemicals and is based on the ORP concept, however the sludge will pass a TCLP.

Michael Shelton
aerospace - Sullivan, Missouri
January 7, 2010

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Thanks, Michael. I agree that it's doable, and not just by "the largest facilities". I've treated fairly large batches of chrome, too. I don't know whether the chrome batches alone would pass the TCLP test, but combined with the other shop waste they did.

But I still feel that for Jon's one-time problem it is more practical to send 15 gallons off site than to thrust the complications of chrome treatment onto his waste treatment system which wasn't designed for it. Thanks again.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January , 2010