Impact of Chlorination and Chloramination on Regulated Trihalomethane Formation: Exploring DOC Reactions with Disinfectants

Abstract Dissolved organic carbon (DOC) is a critical parameter in water quality management due to interaction with disinfectants, leading to the formation of potentially carcinogenic disinfection by-products (DBPs) during water treatment. Forest ecosystems are key contributors of DOC to surface waters, stemming from soil leachate. This study focuses on the formation of trihalomethanes (THMs), a common group of DBPs, following the chlorination and chloramination of soil-extracted DOC solutions under varying environmental conditions. For this purpose, soil samples from a densely forested upland watershed in Illinois, United States, were processed to extract DOC. The findings indicate notably higher production of THMs through chlorination compared to chloramination. It was observed that total trihalomethane (TTHM) levels significantly elevated with increases in DOC concentration, reaction time, and the dose of disinfectant in both treatment processes. The presence of bromide in the DOC influenced the concentration of brominated THMs (Br-THMs) during chlorination, whereas pH and temperature exhibited a moderate effect on TTHM formation. Furthermore, the study revealed that, except for pH and Specific Ultraviolet Absorbance (SUVA), all tested water quality indicators (DOC, total dissolved solids, turbidity, and UV254) exhibited a strong positive correlation with TTHM levels during chlorination. In contrast, these parameters displayed a moderate to weak correlation with TTHM levels in the chloramination process, suggesting their predictive value for TTHM formation is more pronounced in chlorination treatments.