Oxidation and biotoxicity assessment of microcystin-LR using different AOPs based on UV, O3 and H2O2

Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H2O2 and O-3/H2O2 advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H2O2 process and O-3/H2O2 were effective methods to remove MC-LR from water, and they two performed better than UV-, O3-, H2O2-alone processes under the same conditions. The effects of UV intensity, H2O2 concentration and O-3 concentration on the removal performance were explored. The synergistic effects between UV and H2O2, O-3 and H2O2 were observed. UV dosage of 1800 mJ.cm(-2) was required to remove 90% of 100 mg.L-1 MC-LR, which amount significantly decreased to 500 mJ.cm(-2) when 1.7 mg.L-1 H2O2 was added. 0.25 mg.L-1 O-3, or 0.125 mg.L-1 O-3 with 1.7 mg.L-1 H2O2 was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H2O2, O-3/H2O2 and O-3-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg.L-1 Zn2+, raised to 0.05 mg.L-1 Zn2+ after UV/H2O2 or O-3/H2O2 reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided. (C) Higher Education Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018.