BOOK OF ABSTRACTS 213 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / NOM and Aquatic Systems P3.4 Relationship Between Dissolved Organic Matter Composition and Disinfection By-Products Using Excitation–Emission Matrix Analysis Kazunori Ebata1, Yoshitaka Matsumoto1, Shozo Komiyama2, Takaaki Ito2 1 National Institute of Technology, Toyota College, Department of Civil Engineering, 2-1 Eisei Toyota Aichi Japan, 471-8525, ebata.kazunori@toyota.kosen-ac.jp 2 Toyota City, Waterworks and Sewerage Bureau, Center of Water Management Disinfection by-products (DBPs) are formed when chlorine reacts with humic substances in natural organic matter in drinking water treatment. The drinking water quality standards for dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), which are major DBPs, were strengthened in Japan in 2015, and reducing their formation has become a key challenge for water treatment plants nationwide. This issue is particularly critical in Japan‘s mountainous regions, where many small-scale water supply systems exist and the introduction of advanced treatment processes is often difficult, underscoring the importance of appropriately managing DBPs. DBPs is known to be governed by several factors, including humic substance concentration in raw water, chlorine concentration, water temperature, and reaction time [1,2]. Therefore, a detailed evaluation of changes in the quantity and composition of organic matter at each stage of the water treatment process is essential for effective control of DBPs. We conducted an investigation under both base-flow and high-flow (rainfall) conditions at two slow sand filtration water treatment plants located in Toyota City, Aichi Prefecture, Japan, which use the same river as their source water, from May 2022 to July 2024. Water samples were collected from raw water, post-coagulation (after PAC treatment), and filtered water. Dissolved organic carbon (DOC) concentrations, DCAA, and TCAA concentrations were analyzed. In addition, excitation–emission matrix (EEM) fluorescence spectroscopy was used to characterize dissolved organic matter, and the relationship between changes in organic matter during treatment and DBPs concentration was examined. DOC behavior during the treatment process indicated that, under base-flow conditions, DOC concentrations were similar between raw water and PACtreated water, whereas filtered water exhibited lower concentrations than raw water. In contrast, during rainfall events, mean DOC concentrations were higher overall, and raw water showed greater variability than under base-flow conditions. The results showed that both DCAA and TCAA concentrations in filtered water increased during rainfall events, with statistically significant differences observed particularly at the
RkJQdWJsaXNoZXIy NDA4Mjc=