Fluorescence excitation-emission matrix analysis of dissolved organic matter fractions and their disinfection by-product formation potential in the Chao Phraya River

This study characterizes DOM in the Chao Phraya River, Bangkok, Thailand, examining the chlorine reactivity and DBP formation potential in hydrophilic (DOM-HPI, 49.4%) and hydrophobic (DOM-HPO, 50.6%) fractions. Fluorescence excitation-emission matrix spectroscopy revealed that raw water DOM comprises fulvic-like (50%), humic-like (25%), and protein-like (25%) substances, with humic-like substances showing the highest reactivity to chlorination. After 7-day chlorination, trihalomethanes (THMs) and haloacetic acids (HAAs) reached 1041 and 577 μg/L, respectively, with chloroform dominating THMs (81-89%) and monobromoacetic acid dominating HAAs (70-73%). Specific THM formation potentials were 86, 86, and 104 μg/mg-C for raw water, DOM-HPI, and DOM-HPO, respectively, while specific HAA formation potentials were 45, 34, and 31 μg/mg-C. DOM-HPO exhibits higher specific THM formation potential, while DOM-HPI shows greater specific HAA formation potential, suggesting different DBP formation mechanisms between fractions. The findings highlight the significant role of hydrophobic DOM fractions in DBP formation and suggest that targeting DOM removal before chlorination could be an effective strategy for minimizing DBP formation in drinking water treatment plants.