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

Abstract

Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H2O2 and O3/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 O3/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 O3 concentration on the removal performance were explored. The synergistic effects between UV and H2O2, O3 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 O3, or 0.125 mg·L–1 O3 with 1.7 mg·L–1 H2O2 was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H2O2, O3/H2O2 and O3-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 O3/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.