<i>N,N</i>-Dimethylsulfamide as Precursor for <i>N</i>-Nitrosodimethylamine (NDMA) Formation upon Ozonation and its Fate During Drinking Water Treatment

TLDR

Application and microbial degradation of the fungicide tolylfluanide produces a new decomposition product, N,N‑dimethylsulfamide (DMS). Laboratory and field studies show that DMS is resistant to removal by riverbank filtration, activated carbon, flocculation, and various oxidation or disinfection methods, but the NDMA formed during ozonation is biodegradable and can be partially removed by subsequent biologically active treatment steps such as sand or activated carbon filtration. DMS occurs in German surface and groundwater at 50–1000 ng/L, is not effectively removed by nanofiltration, and during ozonation 30–50 % converts to carcinogenic NDMA; hypochlorous acid disinfection produces unknown degradation products but does not form NDMA or UDMH.

Abstract

Application and microbial degradation of the fungicide tolylfluanide gives rise to a new decomposition product named N,N-dimethylsulfamide (DMS). In Germany, DMS was found in groundwaters and surface waters with typical concentrations in the range of 100−1000 ng/L and 50−90 ng/L, respectively. Laboratory-scale and field investigations concerning its fate during drinking water treatment showed that DMS cannot be removed via riverbank filtration, activated carbon filtration, flocculation, and oxidation or disinfection procedures based on hydrogen peroxide, potassium permanganate, chlorine dioxide, or UV irradiation. Even nanofiltration does not provide a sufficient removal efficiency. During ozonation about 30–50% of DMS are converted to the carcinogenic N-nitrosodimethylamine (NDMA). The NDMA being formed is biodegradable and can at least partially be removed by subsequent biologically active drinking water treatment steps including sand or activated carbon filtration. Disinfection with hypochlorous acid converts DMS to so far unknown degradation products but not to NDMA or 1,1-dimethylhydrazine (UDMH).