Impact of elevated soil temperatures on disinfection byproduct dynamics and coagulation efficiency in soil runoff as a drinking water source

ABSTRACT Extreme heat events, such as heat waves, can alter soil properties and runoff water quality, impacting its suitability for drinking water. This study examines how short-term soil exposure to high temperatures (25, 45, and 65 °C) affects the formation of disinfection byproduct precursors in runoff and assesses the effectiveness of enhanced coagulation in reducing these precursors in chlorinated runoff. The findings reveal that extreme heat significantly increases soil respiration, dissolved organic carbon, and dissolved organic nitrogen levels in runoff. Additionally, concentrations of haloacetic acids (HAA), haloacetonitriles (HAN), and haloketones (HK) consistently rise with increasing temperatures, whereas trihalomethanes (THM) and trichloronitromethane (TCNM) levels show variable patterns. Notably, at 65 °C, the cytotoxicity potency of DBPs is 1.3 times greater than at 25 °C. Enhanced coagulation effectively reduces THM formation by 41–47%, HAA by 47–50%, HAN by 22–28%, and TCNM by 49–61% but it also increases HK formation by up to 54% at 65 °C. The results underscore the critical need to consider the impact of extreme soil surface temperature on DBP precursor formation in runoff, which has significant implications for human health and environmental safety.