Trihalomethane precursor reactivity changes in drinking water treatment unit processes during a storm event

Abstract

Source water quality can significantly impact the efficacy of water treatment unit processes and the formation of chlorinated and brominated trihalomethanes (THMs). Current water treatment plant performance models may not accurately capture how source water quality variations, such as organic matter variability, can impact treatment unit processes. To investigate these impacts, a field study was conducted wherein water samples were collected along the treatment train for 72 hours during a storm event. Systematic sampling and detailed analyses of water quality parameters, including non-purgeable organic carbon (NPOC), UV absorbance, and THM concentrations, as well as chlorine spiking experiments, reveal how the THM formation potential changes in response to treatment unit processes. Results show that the NPOC remaining after treatment has an increased reactivity towards forming THMs, and that brominated THMs form more readily than chlorinated counterparts in a competitive reaction. Thus both the reactivity and quantity of THM precursors must be considered to maintain compliance with drinking water standards, a finding that should be incorporated into the development of model-assisted treatment operation and optimization. Advanced granular activated carbon (GAC) treatment beyond conventional coagulation–flocculation– sedimentation processes may also be necessary to remove the surge loading of THM-formation precursors during a storm event. doi: 10.2166/ws.2019.089 om https://iwaponline.com/ws/article-pdf/19/7/2098/607422/ws019072098.pdf er 2019 Chelsea W. Neil (corresponding author) Yingying Zhao Amy Zhao Jill Neal Y. Jeffrey Yang Office of Research and Development, National Risk Management Research Laboratory, US Environmental Protection Agency, Cincinnati, OH 45268, USA E-mail: [email protected] Yingying Zhao College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310027, China Maria Meyer Greater Cincinnati Water Works, 5651 Kellogg Ave, Cincinnati, OH 45230, USA Current affiliation: Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA