Microcystis aeruginosa Removal and Simultaneous Control of Algal Organic Matter (AOM) Release Using an Electro-Flocculation–Electro-Fenton (EC-EF) System without Chemical Addition

Abstract

Harmful cyanobacterial blooms pose a serious environmental threat to global water ecology and drinking water safety. Microcystis aeruginosa, a dominant cyanobacterial species in cyanobacterial blooms, was removed using the electro-flocculation–electro-Fenton (EC-EF) technology. In the EC-EF system, the iron anode was used as a sacrificial anode to produce iron ions in situ. Combining the aeration device with the graphite felt cathode as one unit realizes a direct and effective air supply to the cathode, and improves the electrical Fenton efficiency for generating oxidizing groups such as hydroxyl radicals. The cyanobacteria removal efficiency was up to 94.6% under optimal process conditions with a current density of 1.08 mA/cm2, an electrolysis time of 5 min, and an aeration flow rate of 0.06 L·min−1. At the same time, the microcystins (MCs) and total organic carbon (TOC) content in the water were controlled. The mechanism of cyanobacterial cell removal using this EC-EF system was investigated via characterization of cyanobacterial cells and flocs and cell membrane permeability analysis. The moderate oxidation and iron hydroxide encapsulation of this system are both beneficial to maintaining the integrity of cyanobacterial cells. The results demonstrated that EC-EF is a chemical-free and eco-friendly cyanobacteria removal technology.