A Process and Criteria for Distribution System Optimization

Increasingly it is being recognized that maintaining the integrity of the distribution system is paramount to delivering safe drinking water. The National Research Council Committee Report entitled Drinking Water Distribution Systems: Assessing and Reducing Risks (NASTB 2006) identified distribution system integrity as encompassing physical, hydraulic, and water quality parameters. In the American Water Works Association G200 manual Distribution System Operation and Management (AWWA 2004) and its accompanying self Assessment Workbook, a total of 31 areas were identified that could impact drinking water quality. Optimizing distribution system operations is important to drinking water utilities for a variety of reasons, from system reliability, to maintenance and operations, asset management and capital planning, to water quality and disease prevention.The current research project, WRF 4109, “Criteria for Optimized Distribution Systems” has developed self assessment tools based on the input of nearly 20 workgroups formed in early 2008. Over 100 individual subject matter experts provided input in a series of conference calls and informational exchanges over a six-month period to develop key optimization criteria and metrics that will allow utilities to perform their own self evaluation of their distribution system operations. In early 2009, the draft self assessment checklists and optimization metrics were reviewed and tested by several utilities before finalizing the project. The final project report and software tool is expected to be available from the Water Research Foundation during 2010. Workgroup topics covered the range of distribution system operations, including cross connection control; maintenance: hydrants, valves, and blow offs; external corrosion control; storage facility maintenance; main breaks; disinfection of new mains or repairs; pipeline installations rehabilitation & replacement; water leakage/loss; distribution system flushing; energy management; hydraulic modeling and planning; pressure management; water age management; sample collection plans; bio-film management and control; microbiological monitoring and response; post precipitation control; disinfectant residual; disinfectant by-product monitoring & control; internal corrosion control and monitoring; nitrification control; customer complaint monitoring & tracking; and security and emergency preparedness/response.The outputs from the workgroup process emphasized specific metrics and a self-assessment process by which optimization of the distribution system can be evaluated. Specific rationale of why certain key activities were included in the evaluation criteria and their implications for the water industry will also be described. The goal of the project was to develop a manageable, relatively small, set of critical optimization criteria to support key self-assessment areas and potential performance limiting factors for distribution system operations.