Evaluating dissolved organic matter and trihalomethanes removal in conventional urban water treatment plants in Indonesia: A performance monitoring approach.

The presence of natural organic matter (NOM) plays a critical role as disinfection by products (DBPs) precursor in Dago Pakar Unit water treatment plant (WTP). This study aims to assess the potential formation of regulated DBP, trihalomethanes (THMs) influenced by NOM characteristics at the Dago Pakar Unit WTP. The study involved the analysis of physicochemical parameters, spectral NOM characterization, and DBPs formation potential, particularly THMs. The results indicated that the physicochemical parameters of temperature and residual chlorine did not comply with quality standards, while pH, turbidity, and electrical conductivity (EC) remained within acceptable limits. The measurement of chromophoric dissolved organic matter (CDOM), including UV254, UV355, UV250/365 or E2/E3 ratio, and fluorescence dissolved organic matter (FDOM), indicated that the organic compounds were predominantly aromatic, such as humic and fulvic acids, originating from both autochthonous and terrestrial sources. The conventional treatment process successfully removes the humic acid-like by 93.24%, but has no significant effects on other fractions. The formation potential of trihalomethanes-4 (THM4) of raw water was 1457.76 μg/L, and only reduced by only 24% after the treatment process, exceeding the maximum contaminant levels set by USEPA and Indonesia's Ministry of Health Regulation. Rainfall events reduce the THM4 formation in both raw and treated water, but are still higher than USEPA regulations. Based on the findings, conventional treatment could not be used to alter the THM precursor in Dago Pakar WTP.