Cyanobacterial/harmful algal blooms (HABs) are a serious and growing threat to water resources. This project evaluated cavitation fields generated from four different nozzle configurations to determine their efficacy in HAB treatment performance and correlate oxygen radical production with HAB treatment. Oxygen radicals, particularly superoxides, have demonstrated their ability to transform organic contaminants, including microcystin toxins released from some cyanobacteria species. In this study, pure cultures of Microcystis aeruginosa and Anabaena spp. were subjected to two hours of cavitation treatments with each nozzle. It was found that the nano-micro bubble treatment nozzle was the only configuration that significantly decreased turbidity and chlorophyll concentrations, in addition to notable reductions in microcystin toxin levels. Cavitation tests performed on environmental cyanobacteria samples using other treatment nozzles rendered no significant damage to algal cells. Results from electron paramagnetic resonance (EPR) spectra supports the treatment performance of the nano-micro bubble nozzle as hydroxyl (OH) and superoxide (O2-) radicals generated by the nozzle were detected in cavitated waters. Overall, the results from this study imply that hydrodynamic cavitation with the appropriate nozzle configuration can be used as an effective means of controlling certain species of cyanobacterial in HAB affected areas.
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