AWWA WQTC56957

The future Stage 2 Disinfectants/Disinfection Byproducts (D/DBP) Rule will have a significant impact on potable water systems in Arizona, especially surface water systems. This future rule, which focuses on controlling the highest DBP levels in a system, will require many Phoenix-area utilities to carefully evaluate their water distribution infrastructure and operational strategies. A likely requirement of this rule is the implementation of an initial distribution system evaluation (IDSE) to identify DBP hot spots. The City of Phoenix (City) has already started to plan for the future Stage 2 D/DBP Rule and its IDSE requirements. Carollo Engineers, Malcolm Pirnie, Inc., and others are working to update the City's Water Quality Master Plan to help the City comply with this future rule and meet other water quality goals. As part of the planning, the project team is taking the City's existing steady-state hydraulic model to the next level which involves updating infrastructure data, developing extended period simulation (EPS) capabilities, and calibrating predictions of water age and source water contribution. Outputs of water age and source contribution were then used as inputs to water quality models to predict disinfection byproduct (DBP) formation in the distribution system. The resultant tool will be used for evaluating planning alternatives, identifying DBP hot spots for the IDSE and improving system operations. The project team performed a distribution system tracer test during January 2002 to generate data to further calibrate the City's hydraulic model. This paper summarizes the execution and results of the fluoride tracer testing program and the application of results to model calibration. Targeted sampling areas were identified, taking system flow paths and historical water quality data into consideration. The testing program required significant coordination between different divisions within the City's Water Services Department and with the Phoenix Fire Department to identify secure sampling locations where auto-samplers could be installed. City of Phoenix Fire Department facilities were chosen due to their security and locations throughout the City. In addition to samples collected by the auto-sampling units for fluoride tracer analysis, water quality samples were collected and analyzed during the study for free chlorine residual, pH, temperature, total trihalomethanes (TTHMs), and haloacetic acids (HAA5). These data were used in combination with water age and source contribution data from the fluoride testing to calibrate water quality models for chlorine decay and DBP formation. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2002

Number of Pages:

15

File Size:

1 file , 1.2 MB