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Modeling and Indexing Disinfection By-Product Formation in Competitive Reactions during Drinking Water Treatment
Citation:
Yang, J., C. Neil, D. Schupp, AND J. Neal. Modeling and Indexing Disinfection By-Product Formation in Competitive Reactions during Drinking Water Treatment. EWRI 2021, Milwakee, Wisconsin, June 07 - 11, 2021.
Impact/Purpose:
Communicate research results on DBP formation in drinking water treatment to the scientific and technical communities through the international conference
Description:
Drinking water disinfection by-products (DBPs), including four trihalomethanes (THM4), are carcinogenic and thus under extensive research and regulatory attention. Recent literature and engineering practice show competitive reactions of Cl-, Br-, and other reactants (e.g., I- and N+) with DBP precursors can form different DBPs of varying toxicity. To better quantify the competitive reactions for treatment optimization, this study examines the working hypothesis that preferential removal of natural organic compounds along a treatment train produces water of characteristic formation potentials and compositional preferences for Cl- and Br-THMs as governed by competitive reactions. The investigation consists of field studies in a treatment plant at the Greater Cincinnati Water Works, bench-scale kinetic testing of DBP formation, and the THM4 concentration and compositional modeling with index water parameters. The study results show that THM concentration and composition, formation potentials, and the bromide incorporation factor (BIF) varied significantly through conventional coagulation-flocculation-filtration treatment units, advanced GAC adsorption, and UV/Cl disinfection. These variations are mathematically modeled in three stages of competitive reactions: fast-oxidation, THM-formation, and exhaustion. Fast-oxidation stage is typical of rapid chlorine decay and slow THM formation, notably in raw water and conventional treatment units. THM-formation stage is prevalent in all treatment units following second-order reaction kinetics. In the third stage, the advanced GAC treatment and UV/Cl disinfection preferentially remove reactive organics of typical UV-254, while relatively enriching the strongly humified material of high UVA values, leading to the water of higher Br-THM formation potentials. These new kinetic understanding and mathematical models are valuable for drinking water treatment analysis and process optimization in adapting to the source water quality variations. Disclaimer: The views expressed in this abstract are those of the author(s) and do not necessarily represent the views or policies of the U.S. EPA and the Department of Energy.