Simultaneous electrochemical removal of Microcystis aeruginosa and sulfamethoxazole and its ecologic impacts on Vallisneria spiralis

Abstract

In this study, the simultaneous removal effects of electrochemical oxidation with boron-doped diamond anodes at different current densities were tested on Microcystis aeruginosa and sulfamethoxazole. Flow cytometry and non-invasive micro-test technology were applied to study the physiological states of M. aeruginosa and Vallisneria spiralis leaf cells. As the current density increased, the degradation effect of electrochemical oxidation on sulfamethoxazole and microcystin-LR increased and exceeded 60% within 6 h. In addition, population density of M. aeruginosa, fluorescence response of chlorophyll a, and cytoplasmic membrane integrity decreased, whereas the proportion of cells with excessive accumulation of intracellular reactive oxygen species (ROS) increased. The effect of electrochemical oxidation on the cell population of M. aeruginosa continued after the power was turned off. The physiological state of V. spiralis leaf cells was not severely affected at 10 mA/cm2 for 24 h. Higher current intensity and longer electrolysis time would induce apoptosis or necrosis. In order to achieve a higher target pollutant removal effect and simultaneously avoid damage to the lake ecosystem, the current intensity of the electrochemical oxidation device should not exceed 10 mA/cm2, and a single electrolysis treatment should range from 6 h to 24 h.