Applying DPB models to full-scale plants

Because of increasing concern about balancing health risks for microbiologi cal control and disinfection by-product formation, utilities are closely ex amining and optimizing disinfection practices. The authors present a method ology for developing site-specific, in-plant (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 P aris suburbs. A key obstacle was the limited historical record of bromide ( Br-) occurrence. However, lab chlorination experiments indicated that appro ximately 10 percent of Br- was typically incorporated into THMs. In-plant C l-2 residuals were accurately simulated with a simple first-order Cl-2 cons umption model. The most accurate THM simulations were obtained using a rece ntly developed US Environmental Protection Agency model that incorporates s pecies-specific reactivity parameters.