Formation of N-Nitrosamines from Eleven Disinfection Treatments of Seven Different Surface Waters

Abstract

Formation of nine N-nitrosamines has been investigated when seven different source waters representing various qualities were each treated with eleven bench-scale disinfection processes, without addition of nitrosamine precursors. These disinfection treatments included chlorine (OCl-), chloramine (NH2Cl), chlorine dioxide (ClO2), ozone (O3), ultraviolet (UV), advanced oxidation processes (AOP), and combinations. The total organic carbon (TOC) of the seven source waters ranged from 2 to 24 mg x L(-1). The disinfected water samples and the untreated source waters were analyzed for nine nitrosamines using a solid phase extraction and liquid chromatography-tandem mass spectrometry method. Prior to any treatment, N-nitrosodimethylamine (NDMA) was detected ranging from 0 to 53 ng x L(-1) in six of the seven source waters, and its concentrations increased in the disinfected water samples (0-118 ng x L(-1)). N-nitrosodiethylamine (NDEA), N-nitrosomorpholine (NMor), and N-nitrosodiphenylamine (NDPhA) were also identified in some of the disinfected water samples. NDPhA (0.2-0.6 ng x L(-1)) was formed after disinfection with OCl-, NH2Cl, O3, and MPUV/OCl-. NMEA was produced with OCl- and MPUV/OCl-, and NMor formation was associated with O3. In addition, UVtreatment alone degraded NDMA; however, UV/ OCl- and AOP/OCl- treatments produced higher amounts of NDMA compared to UV and AOP alone, respectively. These results suggest that UV degradation or AOP oxidation treatment may provide a source of NDMA precursors. This study demonstrates that environmental concentrations and mixtures of unknown nitrosamine precursors in source waters can form NDMA and other nitrosamines.