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Bench-scale simulations of the coagulation/flocculation/sedimentation process were performed in this study to determine if amine-based polyelectrolytes were a source of amine precursor for the formation of N-nitrosodimethylamine (NDMA). Several polymers have been tested, and results for two cationic polymers [polydiallylmethylammonium chloride (polyDADMAC) and epichlorohydrin-dimethylamine (Epi-DMA)] and one nonionic polymer [polyacrylamide] are discussed in this paper. Test conditions were chosen in consideration of the classic formation pathway of nitrosation. The effect of nitrite and chlorine dose were also examined. The presence of amine in polymer structure does not guarantee NDMA formation; therefore, the polymer structure must be examined. The use of polyDADMAC and Epi-DMA in simulated coagulation/flocculation/sedimentation processes resulted in significant NDMA formation, while NDMA concentrations were below detection when polyacrylamide was used. NDMA concentrations increased when polyDADMAC and Epi-DMA doses were increased. The other factors studied did not have independent effects on the resulting NDMA concentrations, but there was evidence of an interaction between nitrite concentration, polymer dose, and chlorine concentration when polyDADMAC was used. Includes 26 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2002 Number of Pages: 14File Size: 1 file , 280 KB