Effects of fulvic acid size on microcystin-LR photodegradation and detoxification in the chlorine/UV process.

Qiyuan Sun, Shanbin Wu, Ran Yin, Xingjian Bai, Arun K Bhunia, Changqing Liu, Yuyi Zheng, Feifeng Wang, Ernest R Blatchley

Water research 2021 Apr 01

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Microcystin-LR (MC-LR), a polypeptide toxin generated by cyanobacteria, threatens the safety of drinking water supplies. In this study, fulvic acid (FA) was separated into two molecular weight (MW) ranges to evaluate the effects of FA size on MC-LR degradation in the chlorine/UV process. The rates of MC-LR degradation were significantly reduced in FA-containing water (3.7 × 10-3 s-1 for small MW FA; 4.3 × 10-3 s-1 for large MW FA) as compared with FA free water (4.9 × 10-3 s-1). The contributions of ClO• to MC-LR degradation were dramatically lower in small MW FA water (0.4%) than large MW FA (13.9%) and FA free water (17.4%), suggesting inhibition by lignin-like substances in FA in the transformation of Cl• to ClO• and scavenging ClO•. Monochlorination and hydroxylation occurred in the first step of the MC-LR degradation process. The accumulation of intermediate products in the chlorine/UV process indicated that small MW FA inhibited further degradation of MC-LR. Small MW FA, rather than MC-LR degradation, was the dominant factor in minimizing MC-LR cytotoxicity toward a human intestinal epithelial cell line. Copyright © 2021 Elsevier Ltd. All rights reserved.

Citation

Qiyuan Sun, Shanbin Wu, Ran Yin, Xingjian Bai, Arun K Bhunia, Changqing Liu, Yuyi Zheng, Feifeng Wang, Ernest R Blatchley. Effects of fulvic acid size on microcystin-LR photodegradation and detoxification in the chlorine/UV process. Water research. 2021 Apr 01;193:116893