Synergistic removal of Microcystis aeruginosa by a novel H2O2 pre-oxidation enhanced pressurization method: Performance and mechanism

Abstract

The increase of cyanobacterial blooms in eutrophic bodies of water has threatened drinking water quality, watershed landscapes, and public health, calling for effective suppression methods. Here, H2O2 pre-oxidation enhanced pressurization was first designed for synergistic removal of the most common cyanobacteria Microcystis aeruginosa in water. The concentration gradient of H2O2 and the process mode of pressurization were optimized for effective algal removal. Using 1.0 mg/L of H2O2 and the process of pressurization with a 30 s staying at 0.7 MPa (rate: within 5 s), then rapid depressurization (rate: within 5 s) could achieve 57.84% removal of M. aeruginosa within 24 h and complete suppression after 7 days. The neutral conditions, natural temperatures and relatively high levels of algae cell density were found to facilitate algal removal efficiency. The algal morphology observation and enzyme activity tests revealed moderate morphological damage and activated antioxidant enzymes during the coupling treatment, indicating the predominant role of intracellular reactive oxygen species in the algal suppression. The leakage of microcystin was detected to be limited at a concentration of 4.9 μg/L. Moreover, pressurization characterized by nonviolent impairment in the coupling process was proposed to dominate the synergistic algae removal (i.e., 72.95% contribution). This study provides a promising cost-effective and eco-friendly strategy for eliminating M. aeruginosa in water.