Efficiency and mechanism of ozonated microbubbles for enhancing the removal of algae and algae-derived organic matter

The effective control of eutrophication caused by algae blooms is still the focus of global attention. The traditional dissolved air floatation process for algae removal has a low adhesion efficiency between bubbles and algal cells and a low removal efficiency of organic pollutants. Aiming to address these defects, this study set up an ozone microbubble-enhanced air flotation experiment to explore the removal trends of algal cells and algal organic matter (AOM) pollution. In contrast to traditional air flotation, this approach targets the removal of various forms of AOM after algal cell damage. The highest removal rates of algal cells, extracellular microcystin (Mc), intracellular Mc-lr and total Mc-lr were 96.6%, 60.1%, 95.2% and 93.7%, respectively. Compared with the traditional process, the absorption rate and utilization rate of ozone were increased by 41.9% and 46.2%, respectively. The removal effect of AOM was also greatly improved, and ozone microbubbles enhanced the removal of aromatic protein-like substances and high-molecular-weight fulvic acid, humic acid and humic substances. The advantageous synergistic effect of ozone and microbubbles on algae removal was analyzed by exploring the enhanced air flotation removal mechanism of ozone microbubbles' enhanced air floatation removal. Good vacuole adhesion and strong oxidation caused by ozone microbubbles jointly guaranteed a good removal rate of AOM. The enhanced air flotation process with ozone microbubbles has high feasibility and a good effect, can effectively remove algal cells and algal pollutants, and has great potential in algal removal and control of water eutrophication.