Microcystis aeruginosa removal by peroxides of hydrogen peroxide, peroxymonosulfate and peroxydisulfate without additional activators

Harmful algal bloom (HAB) is one of the most globally severe challenges in ecological system and water safety. Hydrogen peroxide has been commonly used in the management/treatment. Solid oxidants (e.g., peroxymonosulfate (PMS) and peroxydisulfate (PDS)) may outperform liquid H₂O₂ due to ease in transportation, handling, and applications. However, the information on applications of PMS and PDS in algae treatment is limited. In this study, the two solid peroxides and H₂O₂ were investigated for the removal of the blue-green algae of Microcystis aeruginosa. H₂O₂ and PMS effectively removed algae in 2 d at pH 5.0, 7.0 and 9.0, while PDS was only effective at pH 5.0. The change in pH and the release of dissolved organic carbon were insignificant at 0.2 mM H₂O₂ and PMS. The PMS could degrade microcystin-LR and phycobiliproteins. The studies of phycobiliproteins degradation and scanning electron microscopy indicated that PMS might cause the cell inactivation mainly by damaging the chemical components in algae cell wall and membrane while H₂O₂ might mainly enter the cell to form oxidation pressure to kill algae. The scavenger experiments showed that radicals were not crucial in H₂O₂ and PDS applications. Similarly, the algae removal by PMS was obtained mainly by non-radical pathways; about 77% was direct PMS oxidation and no more than 3% was singlet oxygen-mediated process, while radical pathways of sulfate radical and hydroxyl radical accounted for 18% and 2%, respectively. For the realistic algae-contaminated natural water, the PMS effectively lasted for 60 d, while the H₂O₂ lasted for 12 d. This research work demonstrates that the PMS is promising in control of HAB. The findings can provide some useful design and application parameters of PMS technology for better management/treatment of algae-contaminated water.