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With the promulgation of the Stage 1 Disinfectant/Disinfection Byproduct (D/DBP) Rule andthe future promulgation of the Stage 2 D/DBP Rule, utilities are facing the challenge to selectdistribution system sites representative of worst-case conditions in terms of high trihalomethane(THM) and haloacetic acid (HAA) concentrations, high and low disinfectant residuals, and arange of hydraulic residence times. The US Environmental Protection Agency (USEPA) recently developed a Guidance Manual to helpthe utilities select their distribution system sites for the Initial Distribution System Evaluation(IDSE).Our team is currently working on an AwwaRF research project that studies factors affectingformation and decay of DBPs under actual distribution system conditions. While the goal of theUSEPA Guidance Manual for IDSE is to help utilities select DBP monitoring sites in a full-scaledistribution system, our study focuses on a relatively small area of the system to allow acomprehensive investigation of the factors affecting the formation and decay of several DBPs(THMs, HAAs, NDMA). Thus, the first step of our project consisted of selecting a generaldistribution system area for each utility. Once a distribution system area was identified, modelingwas conducted to calculate the hydraulic residence time (water age) associated with each node inthe distribution area. Monitoring sites were then selected based on water age and other hydraulicand water quality parameters. Five geographically-spread utilities are participating in our project.This paper provides an overview of the regulations affecting distribution systems, and describesin detail the methodology used and the factors affecting the selection of distribution system sitesused to monitor for THMs and HAAs under the Stage 2 D/DBP Rule. Includes figures.

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Edition: Vol. - No. Published: 10/01/2003 Number of Pages: 12File Size: 1 file , 190 KB