NDMA formation potentials (NDMA-FP) were evaluated with and without ClO2 pre-oxidation before chloramination and with ClO2 disinfection only. Twenty-three potential NDMA precursors were selected, including tertiary amines, typical pharmaceuticals and personal care products (PPCPs) and industrial contaminant with dimethylamine functional groups.  Pre-oxidation with ClO2 before chloramination greatly decreased NDMA formation in most of the samples (Figure 1). One exemption is dimethylformamide (DMFA), a broad solvent used in the production of synthetic leather. It was possible that after pre-oxidation with ClO2, DMFA would yield other compounds that would react with chloramine to produce NDMA. When comparing ClO2 and monochloramine as disinfectants, ClO2 yielded lower levels of NDMA than monochloramine except DMFA and daminozide. Daminozide is a plant growth regulator and it was an active substance yielding NDMA upon ozonation. The mechanisms of generating NDMA during ClO2 are under exploration. The ClO2 doses, reaction time and pH affected NDMA formation (data not shown). Clearly, NDMA formation from application of ClO2 follows a different pathway from that of monochloramine.

Oxidation of N-nitrosodimethylamine (NDMA) precursors with chlorine dioxide

248th National Meeting (2014)

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