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Chromium removal from Alodine wastewater runoff

2002

To Whom It May Concern;

It has been brought to my attention that the electrocoagulation system to could be a good, reliable, method for removal of chrome from the run-off produced by the Alodine. Could you send me some information, suggestions or comments that you may have concerning this process. Do studies support this process as a good method of removal of chrome from Alodine and is it cost effective? What is the cost of operation and maintenance for this process? It is a complicated process?

Thank you for your assistance,

Ruth Jett
- Robins AFB, GA, USA

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While electrocoagulation will reduce hexavalent chromium by direct electroreduction and possibly also by ferrous iron if it is using consumable iron anodes, electrocoagulation is not as reliable as a chemical reduction that is ORP controlled. The reason for this is that there may be inadequate current to reduce all of the hexavalent chromium present, or inadequate contact time and too high a pH for iron to be effective. Any hexavalent chromium that is not reduced will pass straight through the system.

Lyle Kirman
consultant - Cleveland Heights, Ohio
2002

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I think a few questions are in order. When you say "run-off", do you mean rinses? If so, what is the concentration of hexavalent chrome in the rinse? Have you fully exploited the use of sprays and counterflow rinses to minimize the concentration of Cr+6 to the stream?

If you have quantified the concentration of the Cr+6, what is the flow (gal./hour)? If the resultant amount of water is large and the concentration is significant, chemical reduction with precipitation of the resultant trivalent would be advised. If the volume is small (e.g. 50 - 100 gal. per day) and the concentration is low, an ion specific ion exchange resin (anionic) will remove Cr+6 very effectively.

Give us a little more information, and a more definitive conclusion will result.

Best regards,

Charles Reichert CEF-2
- Seattle, Washington
2002

I have been removing high levels, 80-100 PPM, of chromium 6 for years. The results are always below 1 PPM after treatment. This is achieved through good chemistry, utilizing coagulation, pH control, flocculation and sedimentation.

Joe Krieger
- Edmond, Oklahoma, USA
February 20, 2012