The integrated disinfection design framework (IDDF) is a new approach to determine disinfection requirements for drinking water treatment facilities. The framework may be applied to enhance or improve disinfection performance in lieu of using the surface water treatment rule (SWTR) Guidance Manual. The overall IDDF approach consists of four modules: hydraulic characterization, disinfectant demand/decay, inactivation kinetics, and disinfection by-product (DBP) formation. In this study, a review of the hydraulic characterization module is presented. The module was applied to two full-scale water treatment plant processes (1: a group of six filter beds, 2: a disinfection contactor). The data from the hydraulic characterization module, which consists of three methods to generate the residence time distribution (RTD) curve, was then used to demonstrate the microbial inactivation and DBP formation level that might be produced at the process effluent. Results suggest that the predicted microbial inactivation level is sensitive to the hydraulic characterization method. However, all three methods predict very similar DBP formation despite differences in the RTD data. Results also showed that the disinfectant dose applied to the contactor could be reduced by 35% and still maintain the same credit for Giardia inactivation specified by the USEPA CT tables. This reduction in disinfectant dose could result in a reduction in the total trihalomethane (TTHM) level by 10% and haloacetic acids (HAAs) by 20%.

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