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Microcystin-LR (MC-LR) is the most widely distributed and harmful variant toxins released by cyanobacteria, which poses potential threaten to people and aquatic animals when entering natural water. In our research, solar/chlorine process was comprehensively investigated to degrade and detoxify MC-LR. Under the chlorine concentration of 1.0 mg L -1 , MC-LR (1.0 μM) was decreased by 96.7%, 26%, and 9% by solar/chlorine process, chlorination, and solar irradiation respectively. Quenching experiments confirmed that reactive chlorine species (RCS) and hydroxyl radical (HO) were the predominant reactive species in solar/chlorine process at neutral condition, and ozone was generated because of the participation of triplet-state oxygen (O( 3 P)). The respective contributions of each reactive species were calculated with the order as: RCS, HO, ozone, and solar irradiation. The presence of HCO 3 - and natural organic matter in water inhibited the degradation efficiency of MC-LR. Moreover, the transformation products of MC-LR generated during the solar/chlorine process were identified and a possible pathway was proposed. The hepatotoxicity of MC-LR and its transformation products was compared using protein phosphatase 2A. Our experimental results revealed that the concentration and hepatotoxicity of MC-LR both significantly decreased, and most products were not hepatoxic. Overall, the solar/chlorine process is a promising alternative technology to degrade MC-LR during eutrophication., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Inactivation of Microcystis aeruginosa by UV/chlorine process was investigated in this study. Chlorine decay with or without the presence of algal cells was modeled based on a kinetic model, and the second-order rate constant between chlorine and algal cells was determined to be 3.3 × 10 −4 (mgC/L) −1  s −1 . Flow cytometry as well as confocal laser scanning microscopy were used to characterize the cell integrity of M. aeruginosa . Results demonstrated that UV/chlorine pre-oxidation was responsible for the inactivation of M. aeruginosa , and the inactivation efficiency increased with the increasing dosage of chlorine. UV/chlorine process can significantly change the surface characteristics of M. aeruginosa and enhance the coagulation efficiency. Moreover, due to the destruction of algal cells, microcystin-LR would be released and then degraded during pre-oxidation, and the releasing endotoxin could be removed during subsequent coagulation-sedimentation process. This study suggests that UV/chlorine process might be a potential alternative for the pretreatment of cyanobacterial cells in treating cyanobacteria-laden water. [ABSTRACT FROM AUTHOR]

Oxidation of microcystin-LR (MCLR) by copper (II) coupled with ascorbic acid (H 2 A) in the presence of oxygen was investigated in this study. The combination of Cu(II) with H 2 A in situ generates H 2 O 2 by reducing dissolved oxygen and subsequently produces reactive species through the reaction of Cu(I) and H 2 O 2 . A kinetic model was established to successfully describe the kinetics and mechanism for generation of H 2 O 2 , and the second-order rate constant between Cu(II) and HA − at neutral pH was determined to be 3.0 × 10 3 M −1 s −1 . Furthermore, quenching tests and electron spin resonance (ESR) analysis were used to identify the primary reactive species, and results indicated that HO is the primary reactive species and responsible for MCLR degradation. Batch experiments were further conducted to evaluate the effect of Cu(II) and H 2 A dosage, solution pH and Cl − concentration on the degradation of MCLR during the Cu(II)/H 2 A system. The MCLR degradation increased with the increasing Cu(II) and H 2 A dosages, while decreased with the increasing solution pH. However, addition of Cl − could significantly inhibit the degradation of MCLR. Meanwhile, a possible degradation pathway of MCLR in the Cu(II)/H 2 A system was proposed. And the toxicity assessment by PP2A test showed that MCLR was readily degraded and the oxidation by-products are not hepatotoxins. Therefore, the Cu(II)/H 2 A process could be considered as a potential technology to remove MCLR in algae-laden water. [ABSTRACT FROM AUTHOR]