The presence of wastewater effluents in source waters can increase the formation of haloacetonitriles (HANs), a group of nitrogenous disinfection byproducts exhibiting 10–100 times higher cytotoxicity and genotoxicity than the trihalomethanes and haloacetic acids regulated by the U.S. Environmental Protection Agency. Sunlight plays an important role in transforming effluent organic matter as it travels downstream, but its effect on the HAN formation potential of wastewater effluents has not been thoroughly investigated. In this study, 16 secondary effluent samples were collected from 4 wastewater treatment plants over 29 months, disinfected in the laboratory by chlorine or UV to simulate wastewater disinfection, and then irradiated under simulated sunlight. Among four evaluated HANs, dichloroacetonitrile (DCAN) and bromochloroacetonitrile (BCAN) were detected in all samples. Sunlight preferentially attenuated BCAN formation potential (BCAN-FP) over DCAN-FP. For chlorine disinfected samples, 8 h irradiation (equivalent to 2–3 d of natural sunlight) did not decrease the DCAN-FP for most samples, but removed BCAN-FP from two thirds of the samples. The calculated cytotoxicity contributed by all dihaloacetonitriles was also reduced in most samples after 8 h irradiation. Similar behavior was observed for a mixture of wastewater and surface water (volume ratio 1:1). Experiments using model precursors tryptophan, tyrosine, and fulvic acid showed that BCAN-FP was more likely to exhibit a decrease than DCAN-FP upon irradiation. Fulvic acid best approximated the behavior of the authentic effluent, likely serving as a photosensitizer to degrade other HAN precursors. Lastly, we observed that, for wastewater samples disinfected by UV, the higher the UV dose, the more likely the reductions in DCAN-FP and BCAN-FP by sunlight, a phenomenon also observed for Tryptophan. Experiments suggested that the UV photoproducts of tryptophan have high yields of excited triplet state, which can promote the attenuation of HAN precursors.

Effects of sunlight on haloacetonitrile formation potential from wastewater effluents

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.