Ask the Expert Question-and-Answer Archive (Wastewater Treatment)
by Mike McGinness, EcoShield Environmental Systems, Inc.
Best Practices for Cyanide Treatment
Where can I find the latest techinical information on current recommended best practices for cyanide treatment.
The EPA has only one recommended practice that I know of (the standard 2
stage pH adjustment and chlorination with sodium hypochlorite, which is
called alkaline chlorination) but it requires ventilation, and can be
dangerous (the second stage involves lowering the pH). I also have
concerns about alkaline chlorination producing toxic THM's
(TriHaloMethanes) that are carcinogenic or TTO's (regulated Metal
Finishing Total Toxic Organics). AESF (American Electroplaters and
Surface Finishers Society) has a Canadian Manufacturer member who makes
a proprietary closed treatment system that uses high pressure and
temperature (as I recall) to thermally convert CN into CO2 and N2
including iron cyanides that is specifically designed for Cyanides (I
believe it was the result of an AESF R & D grant years ago, but not
sure). Electrolysis (I think there is a company in Utah that advertises
theirs for Cyanide destruction), ozone (converts it to cyanate), and a
number of advanced oxidation processes will also destroy cyanide. (some
more completely than others). The WEF (Water Environment Federation) has
several member companies that market advance oxidation systems that can
handle cyanide. In small concentrations (say 1 to 5 ppm) sodium and
potassium cyanide reportedly is biodegradable. Silver and copper at even
1 ppm acts as a biocide however.
I have a fairly complete archive on this subject (and I have done some
specialized work in the area) but it would take some time to put into
more detail than the above (and pull the various parts out of my
reference library) and therefore would involve consulting time if you
need more than the above. The groups I listed above all have web sites,
publications and suppliers lists that you can check out directly. One of
the reference books I have is a 199x text on Cyanide treatment methods
published by Noye's.