Applying DBP models to full‐scale plants

Abstract

A case study suggests that the use of site‐specific reactivity coefficients and chlorine consumption results in more accurate models of trihalomethane formation. 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 (Cl 2 ) 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 Cl 2 residuals were accurately simulated with a simple first‐order Cl 2 consumption model. The most accurate THM simulations were obtained using a recently developed US Environmental Protection Agency model that incorporates species‐specific reactivity parameters.