Organic contaminants, such as pharmaceuticals and personal care products, are ubiquitous in drinking water sources, but are not removed by conventional water treatment processes. Chlorine photolysis, which relies on the photolytic cleavage of hypochlorous acid and hypochlorite, is an emerging water treatment method that degrades organic contaminants via a suite of reactive oxidants. Hydroxyl radical is the primary oxidant, while ozone, chlorine radical, dichloride radical anion, and other reactive chlorine species are also formed. In natural waters, these oxidants can react with dissolved organic matter, potentially forming halogenated disinfection by-products. Two major classes of known disinfection byproducts, namely trihalomethanes and haloacetic acids, are regulated in drinking water to protect human health. This study investigates the impact of dissolved organic matter on the formation of reactive oxidants and the production of regulated and novel disinfection by-products under multiple treatment conditions (i.e., pH 6.5 and 8.5, and photolysis at 254, 311, and 365 nm) using traditional analytical techniques and ultrahigh-resolution mass spectrometry. The presence of dissolved organic matter decreases the steady-state concentrations of both hydroxyl radical and chlorine radical due to quenching. Chlorine photolysis forms less trihalomethanes and haloacetonitriles than dark chlorination but increases the formation of haloacetic acids. The formation of halogenated dissolved organic matter is also enhanced during chlorine photolysis under all conditions. The role of halogen radicals in the formation of these novel DBPs is investigated using quencher studies. This study provides insight into the potential of DBP formation during chlorine photolysis.

Impact of halogen radicals on dissolved organic matter transformation during chlorine photolysis

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.