Quaternary ammonium compounds (QACs) are commonly used in industrial and consumer applications as cationic surfactants, disinfectants, and as active ingredients in pharmaceuticals and cosmetics amongst other applications. QACs are typically introduced into the aquatic environment through point source pollution such as discharge of wastewater effluent. There has been concern over detection of QACs in non-target systems, especially because they have been implicated in the promotion and co-selection of antibiotic resistance in bacteria and have been identified as precursors to the formation of carcinogenic disinfection byproducts during drinking water and wastewater disinfection. Limited research has been conducted on the direct and indirect photolysis of QACs in natural waters. The goals of this project are to assess: the transformation potential of benzalkonium chloride (BAC) -- C-12 and C-14 alkyl chain lengths -- and benzethonium (BZT) in river water due to photolysis, and the relative importance of indirect versus direct photochemical processes. Experiments were conducted in Mississippi River Water under natural and simulated sunlight. Additional experiments were conducted under simulated sunlight using model sensitizers such as hydrogen peroxide and Rose Bengal and radical-specific quenchers such as isopropanol and histidine to determine reactivity with hydroxyl radical and singlet oxygen, respectively. Probe compounds such as 4-chlorobenzoic acid and furfuryl alcohol are used to determine second-order reaction rate constants via competition kinetics. Results indicate that direct photolysis of the C-12 and C-14 BACs and BZT is limited. Loss of compounds in river water was enhanced due to reaction with hydroxyl radical generated from dissolved natural organic matter.

Photolysis of select QACs in sunlit surface water

2019 Spring National Meeting

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