Abstract
Evaluating drinking water treatment (DWT) performance requires understanding how dissolved organic matter (DOM) is transformed during treatment and how these transformations drive the formation of disinfection byproducts (DBPs), which remain major concerns in drinking water safety. While current regulations target a limited number of DBP classes, including trihalomethanes (THMs) and haloacetic acids (HAAs), chlorination of DOM produces a much broader pool of largely unregulated DBPs with poorly understood toxicological relevance. In this study, a full-scale conventional drinking water treatment plant was evaluated using an integrated analytical framework combining molecular-level DOM fingerprinting by high-resolution mass spectrometry, targeted DBP quantification by gas chromatography-mass spectrometry, and adsorbable organic halide measurements. This integrated approach enables the assessment of DOM transformation and DBP formation under realistic treatment conditions. Although approximately 60% of dissolved organic carbon (DOC) was removed, molecular fingerprinting revealed a highly selective DOM removal pattern. Aromatic and condensed aromatic compounds were preferentially eliminated, whereas aliphatic and unsaturated fractions persisted and showed a positive statistical association with DBP formation. These results indicate that bulk DOC removal alone is insufficient to mitigate DBP formation and highlight the need for treatment strategies targeting specific reactive DOM fractions to enhance drinking water safety.