Printech Archive, April, 1999: Re: sulfites

Re: sulfites
Thu, 18 Mar 1999 17:26:48 EST


Generally most POTWS will want to regulate sufides because of the dangers
posed by hydrogen sulfide gas build up in the sewer system. We have had
instances were printers have had problems with "hydrogen sulfide" being
present in the effluent. When the issue was investigated, it was determined
that the identification of hydrogen sulfide was the result of limitations
associated with the test method. The method used was EPA method 376.1 and it
will yield a false positive if the sample contains any substance which is
oxidized by iodine under acidic conditions. The common interferants listed in
the method are sulfite, thiosulfate, hydrosulfite, and any volatile iodine
reactive substance. Thiosulfate is present in discharges from photoprocessing
developer. The better method to use is EPA 376.2. When the same sample was
analyzed using EPA 376.2, no hydrogen sulfide was detected. So your problem
may simply be a test method problem.

Let me know which method is being used to analyze the effluent from the two
printing operations.

Gary Jones



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