AWWA DSS63725

This slide presentation outlines a case study at the Dallas Water Utilities where a water quality event in the summer of 2004 occured. Complaints of colored water and low chlorine residual caused the utility to evaluate whether certain process changes were having an impact in mixing zones. EPS modeling was used for evaluating the water quality in the distribution system. Water age, source trace, mixing zones, and pipe materials are presented. Observations included: no clear relationship between mixing zones and unresolved colored water complaints; a prevalence of unlined pipe exists in the vicinity of the unresolved color complaint locations; it is likely that modified distribution system water chemistry between Bachman and Eastside WTPs precipitated iron out of unlined pipes; and, reversed flow direction when Bachman was placed back on line may have precipitated iron. Includes tables, figures.