Alver, AlperBaştürk, EmineKılıç, Ahmet2025-07-102025-07-10202522147144https://dx.doi.org/10.1016/j.jwpe.2025.107977https://hdl.handle.net/20.500.12451/13231In this study, the seasonal variations of natural organic matter (NOM) and the effects of pre-chlorination and pre-ozonation on disinfection by-product (DBP) formation in Mamasın Dam were investigated. NOM was classified into hydrophilic acids (HIA), hydrophobic neutrals (HON), and other fractions to assess their contributions to trihalomethanes (THMs). Seasonal differences were significant, with total organic carbon (TOC) peaking at 6.564 mg/L in summer due to increased biological activity and dropping to 3.173 mg/L in winter. Pretreatment influenced NOM distribution, with pre-ozonation effectively reducing reactive HON and HIN fractions, leading to a decrease in THM formation potential (THMFP) from 292.5 μg/L in raw summer water to 247.9 μg/L. Regression models (R2 > 0.999) confirmed that HIA and HIN were the dominant THM precursors across all THM species. Model performance was further validated using 10-fold cross-validation, yielding high predictive accuracy across all THM species and confirming the absence of overfitting. Pre-ozonation was more effective than pre-chlorination in lowering THMFP, particularly chloroform, highlighting its superior potential for DBP control. These findings emphasize the critical role of seasonal changes and treatment strategies in NOM reactivity and DBP mitigation. This study provides a framework for fraction-specific and adaptive treatment approaches to improve drinking water safety.eninfo:eu-repo/semantics/closedAccessDisinfection by-productsFractionModelNatural organic matterPre-treatmentTrihalomethanesArticle7510.1016/j.jwpe.2025.107977105005503904WOS:001502004800006Q2