Optimization of electrocoagulation–flotation treatment with an aluminum anode to enhance Microcystis aeruginosa cell removal efficiency

Abstract

Cyanobacteria adversely affect drinking water treatment and the quality of the drinking water supply. Microcystis spp. are the most abundant cyanobacteria in many surface water bodies throughout the world. Electrocoagulation–flotation (ECF) treatment has attracted considerable attention as a means of cyanobacteria removal. In this study, ECF treatment was optimized by adjusting the initial pH, electrode distance, stirring speed, and electrical conductivity (k) to maximize Microcystis aeruginosa cell removal efficiency while meeting drinking water quality standards. The treatment was performed for 200 mL M. aeruginosa suspensions (~2 × 106 cells/mL) using an aluminum anode and a graphite cathode at a constant direct current of 100 mA. An initial pH of 6, a stirring speed of 200 rpm, an electrode distance of 1 cm, and k of 500 μS/cm were selected as optimum conditions for the ECF treatment. Under these conditions, M. aeruginosa at a cell density of ~2 × 106 cells/mL was completely removed at a current density of 4.0 mA/cm2 with an average energy consumption of 1.20 ± 0.03 Wh/L. The zeta potential varied from −18.49 ± 3 mV to 1.15 ± 0.38 mV, which confirmed the complete removal of cells. Most importantly, the pH, aluminum concentration, and total dissolved solids of the treated water met the drinking water quality standards of the World Health Organization. The optimized ECF treatment was thus shown to be promising for the removal of M. aeruginosa cells.