This study was designed to identify the effects of variable concentrations of chloride on microbial regrowth, disinfection efficacy, and metal release in drinking water distribution systems. Annular reactors (ARs) containing cast iron or polycarbonate coupons were operated in this study to simulate distribution systems. Experiments were conducted with test water containing chloride concentrations of 10, 75, and 250 mg/L. Chlorine disinfection was applied to achieve 0.2 and 1.0 mg/L free chlorine residuals. Results showed that the ARs operated with elevated chloride concentrations were not significantly different from the ARs operated with low chloride concentrations in terms of microbial regrowth. However, there was a significant increase in iron concentrations after chlorination in the high chloride ARs. Further, more iron release was observed in these ARs at 1.0 mg/L compared to 0.2 mg/L chlorine residual. Higher chlorine doses were required to achieve goal residuals for those ARs with highe...

The contamination of shellfish harvesting areas by fecal bacteria in the Annapolis Basin of Nova Scotia, Canada, is a recurring problem which has consequences for industry, government, and local communities. This study contributes to the development of an integrated water quality forecasting system to improve the efficiency and effectiveness of industry management. The proposed integrated forecasting framework is composed of a database containing contamination sources, hydrodynamics of the Annapolis Basin, Escherichia coli (E. coli) loadings and watershed hydrology scenarios, coupled with environmental conditions of the region (e.g., temperature, precipitation, evaporation, and ultraviolet light). For integration into this framework, this study presents a viable methodology for assessing the contribution of fecal bacteria originating from a watershed. The proposed methodology investigated the application of high resolution remote sensing, coupled with the commercially available product, MIKE 11, to monitor watershed land use and its impact on water quality. Remote sensing proved to be an extremely useful tool in the identification of sources of fecal bacteria contamination, as well as the detection of land use change over time. Validation of the MIKE 11 model produced very good agreement (R² = 0.88, E = 0.85) between predicted and observed river flows, while model calibration of E. coli concentrations showed fair agreement (R² = 0.51 and E = 0.38) between predicted and observed values. A proper evaluation of the MIKE 11 model was constrained due to limited water sampling. However, the model was very effective in predicting times of high contamination for use in the integrated forecasting framework, especially during substantial precipitation events.