Applying DBP models to full-stale plants

Because of increasing concern about balancing health risks for microbiological control and disinfection by-product formation, utilities are closely examining and optimizing disinfection practices. The authors present a methodology for developing site-specific, inplant (finished water) chlorine (C1₂) residual and trihalomethane (THM) formation models. In a case study, the methodology was applied at three operating water treatment plants in the Paris suburbs. A key obstacle was the limited historical record of bromide (Br^-) occurrence. However, lab chlorination experiments indicated that approximately 10 percent of Br^- was typically incorporated into THMs. In-plant C1₂ residuals were accurately simulated with a simple first-order Cl₂ consumption model. The most accurate THM simulations were obtained using a recently developed US Environmental Protection Agency model that incorporates species-specific reactivity parameters.