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Chloroform from NaOCl

We have been using NaOCl to destruct by-product cyanides in waste water treatment. However, recently government regulation change results in occasional chloroform limit discharge problem. This problem is caused by occasional high concentration of chloroform in NaOCl (based on my understanding). Any suggestion to attack this problem? Are there any NaOCl suppliers who supply NaOCl with lower chloroform?

Thanks.

Jim Ji
- Rochester, New York

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I have never heard of CHCl3 being present in raw NaOCl from the supplier. Where would it come from? I think it is more likely that the halogenated organic stuff is coming from an interaction of the hypochlorite with organic substances, such as brighteners, in your rinse waters. The only things I could think of to prevent this are to 1) pass the rinse waters through carbon to remove the organics before chlorination or 2) change your cyanide destruction method, to ozone, hydrogen peroxide or something. Neither of these is terribly practical, I realize. I used to see CHCl3 in my effluent sometimes. Though I wasn't happy to see it, it was always in the 25 - 50 ppb range, way below any actionable limit. You must be dealing with some tough regulators, if your situation is similar. Dave Wichern Consultant - The Bronx, New York Jim, Chloroform is not a normal contaminant in the production of sodium hypochlorite, which is typically produced by either diffusing chlorine gas into caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] , or electrolyzing a sodium chloride unsaturated brine solution to produce NaOCl. If your supplier is telling you that it is normal, I would recommend that you ask for an MSDS sheet (it has to be listed due to its carcinogenic criteria) and get the information from the original producer. If its not a large well known chemical producer, I would say that your being sold some waste or by-product material. Tom Baker wastewater treatment specialist - Warminster, Pennsylvania

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NaOCl cannot create CHCl3 from nowhere. Reaction between NaOCl (Bleach) and acetone results in the formation of Chloroform (CHCl3). This is a famous reaction called Iodoform reaction in organic chemistry.

Basically, if your waste line contains any carbonyl products ( C=O ) with ( -CH3 ) group attached to it, you are at risk of forming CHCl3 (Chloroform). In fact if your waste contains acetic acid ⇦ this on eBay or Amazon [affil links] (CH3CO2H) you will also form CHCl3 (Chloroform).

Ron Najafi
- Novato, California

Chloroform is a common trace contaminant in public water supplies. It results from the combination of Cl. radical with traces of methane from bacterial reduction of CO2. The Cl. radical comes from Cl2 used in the treatment of the water. Cl2 is supplied directly in most water treatment plants but also is released from solutions of NaOCl, particularly if the pH is low. pH is typically manipulated to a set standard in treatment plants. Other organo halides are also found in trace amounts. Although the reactions are genrally shown as reactions between chemical species there are almost always biological mediators involved.

Nick Coffey
- Salem, Oregon
January 4, 2008