Citation:

Duan, X., T. Sanan, A. Delacruz, X. He, M. Kong, AND D. Dionysiou. Susceptibility of the Algal Toxin Microcystin-LR to UV/Chlorine Process: Comparison with Chlorination. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 52(15):8252-8262, (2018). https://doi.org/10.1021/acs.est.8b00034

Impact/Purpose:

This is a product detailing methods to remove cyanotoxin contaminants using novel drinking water treatment methods. It supports efforts covered under EPA StRAP 4.01D related to treatment of cyanotoxins.

Description:

Microcystin-LR, a cyanobacterial toxin (cyanotoxin) common in sources of drinking water, poses a major human health hazard due to its high toxicity. A practical and effective drinking water treatment is needed to protect human health. In this study, UV/chlorine was evaluated for the ability to degrade MC-LR. Compared with UV254 nm irradiation or chlorination individually, the combined process significantly lowered the chemical and energy demand, probably due to the efficient generation of reactive radical species such as hydroxyl radicals, as demonstrated using both direct (terephthalic acid) and indirect (tert-butanol, nitrobenzene, bicarbonate) radical probes. Transformation byproducts generated by hydroxylation, chlorination, isomerization, hydration, as well as bond cleavage were identified by tandem mass spectrometry. Fewer chlorinated adducts of MC-LR were observed in UV/chlorine solution than with chlorine only, but chlorinated disinfection byproducts (DBPs) such as chloroform and dichloroacetic acid were generated as well with long duration UV irradiation. The UV/chlorine treated toxins also showed less cytotoxicity in vitro in HepaRG human liver cell line tests than dark chlorine treated toxins. Rapid degradation of MC-LR was observed with varying pH, oxidant dosage, and with various natural water sources. In filtered water with MC-LR, the formation of regulated DBPs was not increased by adding UV into chlorination because of the faster decay of residual chlorine. The use of low-energy ultraviolet-based light emitting diodes (UV-LEDs) in this study provided a cost-effective strategy for the destruction of microcystin-LR in contaminated source water.

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