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Treatment of cyanide in wastewater

We are a plating company.We are facing the problem on how to treat cyanide in our waste water system. Currently we are using natrium hypochlorite for that purpose. But still we find that it is not very effective to control the cyanide when the concentration is too high. For your information, we are using overflow system in our wastewater plant.Usually, if the cyanide is not well treated, the bacteria will die and result in higher COD value.

Najiha
electroplating factory - Shah Alam, Selangor, Malaysia
2005

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Yes, sodium hypochlorite at high pH, about 11.0, is the correct treatment for cyanide wastes from electroplating, Najiha. You can do a very easy test that the process is proceeding properly by just dipping a small piece of potassium iodide starch paper [affil links] into the waste water and verifying that it turns dark blue (an excess of chlorine is available). I suspect that your continuous treatment tank is either not big enough or not mixing well enough. You should have a wastewater treatment consultant or a supplier of wastewater treatment systems visit to see what is wrong. Good luck.

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