Ask the Expert Question-and-Answer Archive (Wastewater Treatment)

by Mike McGinness, EcoShield Environmental Systems, Inc.
February, 2002

Sodium Dimethyldithiocarbamate (DTC)

Q. I have a client in California who is currently using sodium dimethyldithiocarbamate to pretreat nickel in their wastewater. I have found a 1988 EPA method 630 for analysis of this chemical. My client is required to use an accredited lab for their wastewater analyses and there are no labs accredited for this method in California. Is there another quantitative method for analyzing for this reagent? We are currently performing a qualitative determination and need something more substantive. Any feedback will be greatly appreciated.

A. I have done some checking on this and so far I have not found any new EPA methods for DTC (DimethyldiThioCarbamate). Who is requiring your client to run the tests? What is their definition of accredited and how does it deal in the definition with new situations and new methods. I would suggest asking them this question as well (and document it even if they do not have an answer). I am under the impression that there is a general requirement (EPA) to use a better method (when and where available) if there are know problems and / or interferences in the approved method. When all else fails use standard additions with spikes of the known compound reporting % recovery (standard) and standard dilutions to confirm the data quality of any method (old or new) that you use.

Checking several resources earlier today I have found several news worthy items related to you question. One is copper dimethyldithiocarbamate, which has been studied for use as a wood preservative (so you may want to check the wood industry). But I could not find any analytical method details in the articles I found so far (other than EPA 630). I also found an article about a 140 TON fish kill late last year that is being blamed (currently) on a metal finisher. Since DTC is also used as some kind of biocide in other industries (possibly cooling towers) and other applications it could have been a source other than a metal finisher. However, that kind of news has sent the pretreatment authorities nation wide on a hunt for DTC and certain toxic DTC bioproducts in waste water discharges just late last year. For this reason there will probably be a lot more testing of waste water for DTC and DTC bioproducts in the near future that will eventually lead to new approved methods and accredited labs.

You might consider checking with your clients DTC manufacturer to find out what method they suggest. I would also check with Dioxex and see if they have an ion-chromatography method available. Sorry I could not be of any more help. If you find any interesting information, another method or accredited lab for DTC testing please let me know and I will the add the details to this answer on the web site for others.