Degradation of Microcystin and Possible Phosphorus Removal Mechanism by Electrochemical Treatment

Electrochemical oxidation is widely used to remove harmful organic and inorganic substances as well as pathogenic microorganisms. In this study, removal of Microcystis ichthyoblabe cells and the hepatotoxin it produces, microcystin-LR (MC-LR), was achieved by oxidation using Pt/Ti electrodes with constant voltage system. In addition, a possible mechanism for the removal of phosphorus is posited. Cyanobacteria cells were severely damaged and 96% were removed after 12 h of the electrochemical treatment. MC-LR decreased rapidly, and was undetectable after 24 h. Concentrations of Na+ and K+ ions gradually increased as treatment proceeded. Ca2+ ions decreased because of deposition of these ions on the cathode surface. Total phosphorus was decreased by 29% after 71 h because of the deposition of inorganic phosphorus on the cathode surface. Phosphorus was deposited on the cathode surface along with calcium ions as CaHPO4 (monetite) and/or CaHPO4·2H2O (brushite). This article is the first to report a possible phosphorus-removal mechanism by electrochemical treatment.