AWWA ACE65180

Buying and selling of treated water, as a commodity, is commonplace in the waterindustry. This practice dynamic is characterized by a wholesaler (WS) of the treated water and apurchaser of the treated water, often referred to as a consecutive system (CS). This wholesalerpurchaser dynamic is responsible for serving approximately one-third of US water customers.The primary goal of this study was to develop disinfection byproduct (DBP) control strategies for CSs, which willfacilitate their compliance with the LRAAs in the Stage 2 DBPR. The objective was tocharacterize factors affecting DBP formation and control in CSs by developing a relationshipbetween the chlorine residuals and DBP concentrations in a distribution system (DS) and those ina bench-scale hold study (HS). This relationship may be used to aid the CS in evaluating DBPcontrol strategies. DS samples were taken at the WS plant effluent, the CS entry point and atthree points in the CS focusing on the maximum DBP formation. Relationships in both DS andHS were developed between the chlorine demand and DBPs (TTHM and HAA5). By comparingHS data to the DS data, relationships were then developed for chlorine residuals, chlorinedemands, TTHM and HAA5 formation. A strong relationship between the chlorine demand andTTHM formation was found in both the DS and HS samples. In some quarters, HAA5s werefound to degrade in the DS samples, but not in the HS samples. These relationships were thenused to assess two DBP control options: the impact of water age on distribution system DBPoccurrence; and, distribution system maintenance. Results of the eight utilities and over 500DBP analyses have shown the following: Water Age - about 50% and 60% of the TTHMs andHAA5s were formed in the WTP and about 65% and 75% were formed before the CS entrypoint, thus water age management in the CS was not a strong option; Distribution SystemMaintenance - comparison of the nine HS DS in this study has indicated thatthe uncertainty involved with estimating the water age makes the use of the HS approach toestimate excess chlorine demand difficult, at a minimum. However, changes in distributionsystem management that yield lower chlorine demand will likely yield lower DBPs, especially Total Trihalomethanes(TTHMs) as they form more slowly, relative to Haloacetic Acids (HAAs). Includes reference, tables, figures.



Keywords: Disinfection Byproducts; Distribution Systems; Chlorine; Chlorine Demand; Residual Chlorine; Trihalomethanes; Haloacetic Acids; Compliance