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topic 5138

Cyanide Treatment


Does anyone know about any case studies about the maximum concentration of cyanide in aqueous wastes for the waste water treatment process without running into health risk?

In your opinion which cyanide concentration is better to take into account, total or amenable.

A Arora
- Walnut Creek, California


I think that you need to provide some additional information as to the nature of your question. The health risk will depend on the exposure route and the type of cyanide that you have (e.g., iron complexed vs. free). OSHA has a respiratory standard if your concerned about someone breathing over the top of the tank. If skin contact is an issue, I would suspect that the caustic that allows the cyanide to stay in solution will be much more of a concern than the cyanide. In general, it's the respiratory and ingestion pathways that are the biggest concern.

Looking at total and/or amenable cyanides will depend on the what you've got in your stream. It has been my experience that the amenable test is subject to more positive interferences compared to the totals test (but that will all depend on your water). It is better to test it both ways and find out what works best for you.

I hope this helps.

Bob Holderman
- Tulsa, Oklahoma


I guess I did not clarify my question.

At this time, businesses in the State of California are not allowed to treat aqueous wastes containing any amount of cyanide without holding a "full" hazardous waste facility permit, standardized permit, or other form of authorization such as a variance, or consent order issued by Department of Toxic Substances Control (DTSC).

Proposed cyanide treatment regulations in California (draft stages):

DTSC attempt to promulgate regulations which will authorize the treatment of aqueous wastes containing cyanide at a maximum concentration of 1000 mg/l within the existing permit-by-rule program, including a five-year sunset date which should force facilities to evaluate alternatives to using cyanide in their processes?

The maximum concentration of cyanide which may be in waste to be treated is proposed to be set at 1000 mg/l (total cyanide and not amenable in the rinse water.

I would like to know if there are any standards in any other state for the treatment of aqueous waste containing cyanide or any studies done on this subject. Any feedback will be greatly appreciated. Thanks.. Asha

A Arora
- Walnut Creek, California


I know that treating greater than 1000 mg/l cyanide with typical alkaline chlorination is bad news; you are likely to get either CN gas or Cl gas or a radical cross breed. Total CN usually considers complexed metals as you probably know which slow down the process.

I know of no other regulation like this, but my knowledge in far from comprehensive. I have used high pressure thermal destruction for concentrated complexed CN, which worked well but generated much ammonia. I wonder if this method of treatment was considered by regulators?

mike wells
- jamestown, New York

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