AWWA ACE54305

This study presents the results of a modeling effort aimed at further understanding of the fate and kinetics of both monochloramine and free chlorine loss in the presence of NOM. Two mechanistic models are presented for both disinfectants: a single reactive site model and a dual reactive site model. For the two humic fractions used in this study, the dual site modelbetter predicted both fast and slow disinfectant demand for both disinfectants. Total reactive sites for both models were approximately equal for both humic materials and disinfectants. Therefore, the single site model may be used to approximate the slow reactive site fraction and rate constant minimizing the total number of fitting parameters. Comparison of the reactivefractions for a specific humic material appears to be comparable for either disinfectant although the rate constants differ by 2 to 3 orders of magnitude. Spectral changes attributable to reaction with NOM are very small and may be comparable to other factors that also affect ultraviolet absorbance over long time intervals. Includes 9 references, tables, figures.