Metal finishing Q&As since 1989
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Hydrogen Peroxide effect on Waste Water Treatment
Q. I am a environmental process engineer for a company that does nickel and decorative chrome electroplating on steel bumpers for trucks. One of our plating supervisors has been adding hydrogen peroxide to the acid pickling tank to breakdown organics. Will the hydrogen peroxide cause interference with sodium metabisulfite in the waste water treatment plant when it is used to reduce Cr(VI) to Cr(III)?
Holly Hirchert- Urbana, Illinois
2001
A. Holly, the hydrogen peroxide should have no effect on your waste treatment system. The peroxide in that environment will breakdown rapidly, a matter of hours. If the peroxide was added directly to the Chrome reduction tank, then you may have a situation to deal with.
Best of Luck.
Ira Donovan, M.S.F.Kansas City, Missouri
2001
A. Peroxide reacts with lots of things, so breaks down rapidly. It probably would not cause a problem other than using a little more reactant. That is assuming that he is not going crazy with the peroxide.
James Watts- Navarre, Florida
2001
A. Hydrogen peroxide will certainly consume some of your bisulfite, but will not prevent the reduction of hexavalent chromium to trivalent chromium. However, if you are precipitating the trivalent chromium at alkaline pH as a part of your treatment, you must make certain that all of the peroxide has been destroyed. Usually an excess of bisulfite, or rather sulfite at pH greater than 9, will accomplish this task. A laboratory scale treatment experiment should be performed using your normal routine and the experimental effluent tested for hexavalent chromium, before you can be sure there would be no problems.
Billie J. Page- Cleveland Heights, Ohio
2001
A. Hi Holly,
Why are you treating an acid pickling rinse or dump for hexavalent chromium? Only trivalent chromium should be there, and if any hex chromium was dragged in for some reason the iron and low pH would reduce it.
The only reason I can think of is that you are using waste acid to lower the pH for chromium treatment. If this is the case, and there is peroxide in the waste acid, then it will definitely consume it's equivalent amount of metabisulfite.
Lyle Kirmanconsultant - Cleveland Heights, Ohio
2001
A. Hydrogen peroxide HAS the ability to REDUCE Cr6 to Cr3 in fairly acid conditions (more acid than bisulphite) Where peroxide is in the waste stream with Cr6 then if it is acid enough then it can be used to advantage to reduce some of the Cr6 first and metabisulphite used for the balance. There must be an excess of sulphite in the end or any peroxide left will re-oxidize the Cr when the pH is raised. Re adding it to the HCl pickle -I would query if there is any benefit as it would react with the Fe2 before it would react with organics. I agree there would be no Cr6 in the pickle.
Geoffrey Whitelaw
- Port Melbourne, Australia
2001
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