Sleuthing for precursors to drinking-water treatment byproducts
CARSTEN SCHMIDT
California. The researchers “put basis of their structures, give New research in ES&T (DOI together a very complete and rise to the unwanted byproduct. 10.1021/es7030467) shows that a provocative package.” They not The researchers found that only pesticide widely used in Geronly examined the source of one compound was transformed many degrades into a precursor NDMA precursors but also at a high enough rate to be a sole of a carcinogenic nitrosamine. looked at treatment issues, he source of the toxic drinking-water Several years of careful detective points out. They found that the byproduct: DMS. And only one work led to the discovery that a fungicide degradates were agricultural product on the marbreakdown product known as “poorly removed by traN,N-dimethylsulfamide ditional and advanced (DMS) becomes N-nitechnology.” trosodimethylamine Krasner adds that it (NDMA) during ozonawould be interesting to tion in water-treatment examine water-treatment processes. The finding facilities with different underscores a recurring conditions to see whether problem in drinking-waresults differ. For example, ter treatment: unexplants that process source pected precursors from waters with higher total seemingly innocuous organic carbon loads parent compounds may might use up more ozone, give rise to other chemiresulting in less reactivity cals of concern in the with DMS. environment. Krasner notes that the Carsten Schmidt and his The groundwater beneath this strawberry field in Germany actual mechanism of forco-workers at the DVGW contained DMS, the breakdown product of a fungicide ap- mation is missing from Water Technology Centre plied to the crop. When the water reached a drinkingthe current work. Neverin Karlsruhe (Germany) water treatment plant, ozonation processes turned the DMS theless, says David Sedlak had been detecting relainto carcinogenic NDMA. of the University of Calitively high levels of NDMA ket seemed to produce the levels fornia Berkeley, knowing the in drinking water produced from of DMS that would lead to NDMA mechanism may not be as imporgroundwater and from surface waconcentrations found posttreattant as finding the actual ter treated with ozonation to dement: the fungicide tolylfluanide, precursor. stroy bacteria and other organisms. hundreds of tons of which were Sedlak calls the researchers’ reAt very low levels, NDMA acts as a used in Germany in 2006. sults a surprise. “No previous rehuman carcinogen and as a genoBefore this study, no one knew search had shown NDMA toxic and carcinogenic compound that microbes eventually degrade formation during ozonation,” he in lab animals, according to the the fungicide to its metabolite says. Chloramination treatment World Health Organization and the DMS. The researchers found that generally has been assumed to be U.S. EPA. ozonation turned DMS into the main pathway to its formation. “It took us about 3 years to NDMA with a potential 52% con“I think the larger question the figure out” the source of NDMA version rate. One other product, article raises is whether the appliin Germany’s drinking water, daminozide, showed a 55% concation of an oxidant or disinfecsays Schmidt, who is now at version rate to NDMA, but it was tant can make an unwanted RheinEnergie, a water-treatment not found in the water sources byproduct, in this case, from a utility in Cologne (Germany). tapped by German drinking-water pesticide metabolite,” Sedlak conSchmidt’s team screened more treatment plants. Within months tinues. “We spend a lot of time than 100 water sources for poof the team’s discovery, Germany looking at the fate of parent comtential formation of NDMA duracted to remove tolylfluanide pounds. This research show[s] ing ozonation. After determining from store shelves. that sometimes it is necessary to that waters coming from agricul“In a sense, [the new work] was identify the metabolites and untural areas, such as strawberry really like forensic environmental derstand their fate in the waterfields or orchards, had the most research,” says Stuart Krasner, an treatment process.” potential to create NDMA, the analytical chemist at the Metroresearchers focused on about 30 —NAOMI LUBICK politan Water District of Southern compounds that might, on the 6310 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / September 1, 2008
10.1021/es801944f
2008 American Chemical Society
Published on Web 07/30/2008
