AWWA WQTC59016

North Penn Water Authority (NPWA), located in Bucks and Montgomery Counties, Pennsylvania, serves roughly 27,000 customers. NPWA oversees a system with 435 miles of water mains. The distribution system includes five pressure zones that receive water from 23 production well sources and a surface water treatment plant to meet an average daily demand of about nine million gallons. Other facilities within the distribution system include seven water storage tanks and five booster pumping stations. NPWA and CH2M HILL conducted a master-planning project that included the development of hydraulic and water quality models and optimization using genetic algorithms (GAs) to support the development of a cost-efficient and defensible Capital Improvement Plan. An extended period simulation (EPS) model was developed and calibrated as the basis for the water quality model. Field sampling and bench-scale laboratory tests were conducted to determine bulk decay rates. The model was calibrated for warm and cold weather conditions by comparing model results to field data. The calibrated water quality model was used to identify areas of low chlorine residual and high water age under current conditions. Storage tank turnover and groundwater/surface water mixing variations throughout the distribution system were also evaluated. Additionally, the water quality model was used to evaluate chlorine residuals under projected future demands for full development build-out. The water quality model was used to verify that the GA-optimized solutions would support the delivery of high quality water to NPWA's customers for years to come. The use of the water quality model throughout this project demonstrates the benefits of such a model for improving operations and determining the effect of future demands on distribution system water quality. As more development and inclusion of these tools in master planning projects are realized, water purveyors will gain a more comprehensive understanding of water quality in their systems and the potential impacts of future change. Furthermore, water quality models will provide purveyors with powerful tools to conduct Initial Distribution System Evaluations (IDSEs) as required by the U.S. Environmental Protection Agency's (EPA's) Stage 2 Microbial/Disinfection Byproduct (M/DBP) Rule. Includes table, figures.