Full Description

North Penn Water Authority (NPWA), located in Bucks and Montgomery Counties,Pennsylvania, serves roughly 27,000 customers. NPWA oversees a system with435 miles of water mains. The distribution system includes five pressure zones thatreceive water from 23 production well sources and a surface water treatment plant tomeet an average daily demand of about nine million gallons. Other facilities within thedistribution system include seven water storage tanks and five booster pumping stations.NPWA and CH2M HILL conducted a master-planning project that included thedevelopment of hydraulic and water quality models and optimization using geneticalgorithms (GAs) to support the development of a cost-efficient and defensible CapitalImprovement Plan. An extended period simulation (EPS) model was developed andcalibrated as the basis for the water quality model. Field sampling and bench-scalelaboratory tests were conducted to determine bulk decay rates. The model was calibratedfor 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 residualand high water age under current conditions. Storage tank turnover andgroundwater/surface water mixing variations throughout the distribution system werealso evaluated. Additionally, the water quality model was used to evaluate chlorineresiduals under projected future demands for full development build-out. The waterquality model was used to verify that the GA-optimized solutions would support thedelivery 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 ofsuch a model for improving operations and determining the effect of future demands ondistribution system water quality. As more development and inclusion of these tools inmaster planning projects are realized, water purveyors will gain a more comprehensiveunderstanding of water quality in their systems and the potential impacts of futurechange. Furthermore, water quality models will provide purveyors with powerful tools toconduct 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.

Product Details

Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 7File Size: 1 file , 660 KB