PITTSBURGH WATER AND SEWER AUTHORITY COMPREHENSIVE DISTRIBUTION SYSTEM FLUORIDE TRACER STUDY

The Stage 2 Disinfectants and Disinfection Byproduct Rule (Stage 2 DBPR) builds on the Stage 1 Disinfectant and Disinfection Byproduct Rule (Stage 1 DBPR) and strengthens public health protection for utility customers by tightening compliance monitoring requirements for disinfection byproduct (DBP) formation, including total trihalomethanes (TTHM) and haloacetic acids (HAA5), in finished drinking water. All community water systems and non-community water systems which add a disinfectant to their finished water, excluding ultraviolet light, are required to comply [EPA, 2006]. Many of these drinking water systems will not be able to comply with the Stage 2 DBPR unless changes are made to their treatment or distribution system to improve water quality. One way to asses the degradation of water in distribution systems and identify operational improvements is through a tracer study. Pittsburgh Water and Sewer Authority (PWSA) completed a fluoride tracer study from October to December, 2006. The tracer study data were used to assess the aging of water from the PWSA clearwell to selected sampling points in the distribution system. The results were also used to evaluate the mixing of the primary reservoirs, to calibrate the hydraulic model, and to identify potential operational improvements to increase water quality and balance of the distribution system prior to completing the Initial Distribution System Evaluation (IDSE) for the Stage 2 DBPR