Advancing Chloramine Decomposition Chemistry to Delineate Nitrogenous Disinfection Byproduct Formation Pathways and Reveal Chloronitramide Anion

A Warren Distinguished Lecture with
Julian Fairey

ABSTRACT
Inorganic chloramines are used to treat the drinking water of more than 113 million people in the U.S. alone. Despite their disinfectant efficacy, inorganic chloramines decompose in drinking water systems to products that are poorly characterized. An unidentified product of chloramine decomposition was first reported in 1981, and in 2024, my lab group in collaboration with researchers at USEPA and ETH-Zurich, revealed it as chloronitramide anion. To facilitate widespread occurrence studies, we more recently developed an ion chromatography method for chloronitramide anion quantitation and showed it was present in tap waters treated with chloramines at 22–314 μg/L. This study also showed chloronitramide anion presence in tap waters treated with free chlorine, albeit at lower concentrations (< 10 μg/L), suggesting its occurrence is more widespread than we first reported. This talk focuses on chloramine decomposition chemistry and formation of reactive nitrogen species that serve as key intermediates in the formation pathways of chloronitramide anion and other nitrogenous disinfection byproducts such as N-nitrosodimethylamine (NDMA). The practical implications of these findings are discussed in terms of chloramine formation and stability in drinking water systems.