AWWA WQTC65775

This powerpoint presentation begins by providing background information on treating surface water supplies in Quebec, Canada. Project objectives were to: evaluate the impact of storage conditions (temperature and storage time); evaluate the relative importance of incubation parameters (pH, temperature, Cl₂ dose and contact time); and, compare Trihalomethane-simulated distribution system (THM-SDS) testing with site specific THM; and, identify alternate indicators (SUVA, ultraviolet [UV] absorbance, chemical oxygen demand [COD] and chlorine demand). Conclusions were that: storage up to 7 days had a limited impact on the THM precursors; for incubation time above 24 h, temperature was the most important parameter impacting THM formation, its effect was similar across source water; the effects of pH and chlorine dosage were source specific; increasing contact time from 24 h to 48 h had a moderate impact on THM (13-27% increase); THM precursors were fairly stable over the study period, a limited number of sampling campaigns would have been sufficient to adequately characterize these systems; THM-SDS predicted reasonably well historical THM concentrations; and, even though chlorine demand was highly correlated with THM formation, the prediction error was too high to justify abandoning THM-SDS assays to the profit of chlorine demand tests. Includes tables, figures.