Disinfection Byproducts in Drinking Water during Normal Conditions and 2023 Water Emergency: A Case Study in Uruguay, South America

Uruguay experienced an unprecedented drought, leading to a 2023 water emergency that affected the Aguas Corrientes drinking water treatment plant (ACDW), the main supplier for Montevideo and its metropolitan area. Reduced freshwater supply and saline intrusion elevated the conductivity and halide levels, impacting the water treatment and quality. In this study, we analyze disinfection byproducts (DBPs), focusing on changes in the patterns of total trihalomethanes (TTHMs) and total haloacetic acids (HAAs9) during the water emergency. DBPs and physicochemical parameters were evaluated before and during the water emergency. During normal conditions, TTHMs levels range between 35 and 55 μg/L and HAAs9 between 25 and 37 μg/L, with chlorinated compounds predominating. During the water emergency, DBP patterns and levels changed dramatically. TTHMs increased to the 54–135 μg/L range, while HAAs9 ranged between 65 and 71 μg/L, being brominated DBPs predominant, as indicated by bromine substitution factors (BSFs). The highest DBPs levels coincided with the low-temperature season, limiting their formation. Nevertheless, DBPs concentrations during the water emergency exceeded national, EU, and US regulatory limits. The potential toxicity (Ptox) assessment underscores the need to prioritize monitoring of brominated HAAs. This study highlights the urgent need to review national regulations and develop strategies to address extreme drought conditions.