AWWA DSS60349

The objective of this desk-top analysis was to identify water quality and treatment issues associated with blending the City of Issaquah's (in Washington State) undisinfected groundwater supplies with treated surface water via a new Regional Pipeline. The analysis included evaluation of various blends of groundwater (GW) with surface water (SW) at 25%, 50%, and 75%, and switching to 100% of either source. Corrosion potential, microbial conditions, disinfection byproducts, manganese oxidation and precipitation, and fluoride were assessed. The Rothberg, Tamburini, & Winsor Model for Corrosion Control and Process Chemistry (RTW Model) -Version 4.0 (AWWA, 1996) and simple laws of mixtures were used to predict water quality outcomes as a result of blending. Recommendations were developed to ensure compliance with existing and proposed regulations, and to maintain or improve the aesthetic characteristics of the blended waters. Includes tables, figures.