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Dual Water Systems: Characterization and Performance for Distribution of Reclaimed Water (WaterRF Report 4333)
Grigg, N., P. Rogers, AND S. Edmiston. Dual Water Systems: Characterization and Performance for Distribution of Reclaimed Water (WaterRF Report 4333). Water Research Foundation, Denver, CO, 2013.
This report is a retrospective assessment of dual water systems, which are two distribution systems operating jointly, one to supply potable and the other to supply non-potable water. The impetus for this retrospective study was the identification of dual water systems as a potential technology to improve water safety and reduce the cost of drinking water distribution infrastructure and a desire to evaluate that potential by identifying and assessing the cost and performance of existing systems. A retrospective characterization of dual water systems’ performance can set the stage for strategies to employ dual water systems in the future for appropriate purposes.
The research tasks included: an inventory of cases where dual systems have been implemented; formulation of a protocol to identify claimed benefits, costs, and risks; collection of data (quantitative and anecdotal) to assess performance; display of data in the form of performance results; and explanation of the results. Approximately 335 U.S. systems were identified. Thirty-seven case studies are included. Practically all U.S. dual water systems are being implemented to extend use of scarce supplies and/or offer new options for wastewater management. Improvement of water safety and lowering of water infrastructure costs were not found to be significant drivers for the use of dual systems. The case studies showed that the main uses of water reuse systems are for non-potable applications such as landscape and agricultural irrigation, toilet flushing, industrial process water, power plant cooling, wetland nourishment, and groundwater recharge. While fire-fighting uses seem appropriate, acceptance by fire departments is limited due to health and reliability concerns. Some cross-connections have occurred, but major health problems were not identified. Cost accounting and rate-setting systems for dual water systems need further development.