BOOK OF ABSTRACTS 111 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Thursday, 27 August 2026 / Hall C NOM and Aquatic Systems SL52 Mitigating Mammalian Cell Cytotoxicity of Chlorinated Drinking Water by Conventional and Advanced Treatment Processes Chao Liu (presenting and corresponding), Hang Liu, Ziqi Li Key Laboratory of Environmental Aquatic Chemistry, State Key Laboratory of Regional Environment and Sustainability, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China E-mail: chaoliu@rcees.ac.cn Ozone (O3)-biological activated carbon (BAC) advanced treatment is increasingly applied after conventional coagulation-sedimentation for mitigating the natural organic matter (NOM), which serves as precursors of toxic disinfection byproducts (DBPs) in the subsequent chlorine disinfection. It is well recognized that conventional coagulation-sedimentation processes could partially remove the hydrophobic fraction of NOM, thereby decreasing the precursors of trihalomethanes (THMs) and haloacetic acids (HAAs). In addition, incorporating advanced water treatment processes (e.g., ozone (O3) treatment followed by biological activated carbon (BAC) filters) to the conventional water treatment trains can provide an additional 10%–50% removal of NOM serving as regulated DBP precursors. Recent toxicological studies using Chinese hamster ovary (CHO) cell cytotoxicity assay indicated that the one- and twocarbon-atom (C1 and C2) DBPs were minor contributors (3%–30%) to the total cytotoxicity. This begs the question of whether the effective reduction of precursors for C1 and C2 DBPs using coagulation-sedimentation and O3-BAC treatment can lead to a corresponding cytotoxicity mitigation. The potential reduction of Chinese hamster ovary cell cytotoxicity of chlorinated waters using such measures at full-scale drinking water treatment plants was investigated. Results showed that conventional coagulationsedimentation processes could achieve ~13% to 28% reduction in chlorinated water cytotoxicity. Ozonation did not provide significant reduction. Yet, BAC treatment could additionally mitigate the cytotoxicity by ~14% to 27%. The reduction of cytotoxicity was correlated well with decreased dissolved organic carbon concentrations of chlorinated water. The reduction of unknown nonvolatile fractions featured by high molecular-weight (MW) DBPs, accounting for ~58% to > 90% of total cytotoxicity, is a major cause. Using high-resolution mass spectrometry, O3-BAC treatment could substantially elevate the reduction in number of halogenated features (from <30% to up to 80%), especially for brominated features. 231 features were tentatively
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