AWWA WQTC71642

The City of Phoenix, Arizona, has participated for several years in the Central Arizona Salinity Study (CASS), the Multi-State Salinity Coalition (MSSC), and numerous related initiatives and efforts to understand the sources, impacts, and implications of increasing levels of total dissolved solids (TDS) in reclaimed water. A number of possible TDS strategies are currently being developed and evaluated by the City to address TDS holistically. These include source control, treatment at potable water plants, sanitary sewer point and non-point sources, and treatment of reclaimed water to reduce TDS concentrations. The City conducted a study to gather information regarding the implementation of policies to control TDS discharges associated with residential point-of-use water softening and other treatment systems. As with many water quality problems, a multi-point approach is necessary to control TDS to maximize the value of developed water resources. This presentation will provide an overview of the City's concerns regarding TDS, the efforts involved at controlling it, reasons for why some control strategies do not have support, and a summary of the Citywide Point-of-Use Water Softener and Treatment Study results. The study estimated TDS contributions from various sources, identified TDS control programs, described alternatives to ion exchange water softening, evaluated potential TDS reduction program components, and identified TDS goals (concentration targets) for reclaimed water uses. Includes abstract only.