Study on immediate and long-term growth inhibition of Microcystis aeruginosa by non-thermal plasma

Abstract

There are still few studies on long-term growth inhibition of cyanobacteria though direct algae inactivation by discharge plasma has been widely invetigated. In the work, a home-made DBD system was applied to investigate the immediate and long-term inactivation effect of Microcystis aeruginosa (M. aeruginosa). Owing to discharge plasma in gas–liquid interface or liquid phase, RONS including H2O2, O3 and NO3- and OH radical are produced. The bactericidal effects are time-dependent and a 3.36log reduction (above 99.99%) is achieved after 10-min exposure followed by the loss of membrane integrity resulting in damaged metabolic capacity and partial RS transportation into cells. Plasma discharge also leads to increased intracellular ROS and NO aggravating inactivation efficacy in the interior structure. The concentration changes of MCs indicates a well degradation effect on MCs by DBD plasma. Moreover, growth arrest (10 day for 0.5-min and 15 day for 1-min treated samples) indicates continuous inactivation of short-period DBD. The decreased contents of photosynthetic pigments (phycobilins and Chl-a) and inhibited nutrient absorption efficiency could contribute to residual inactivation effect. The inhibited synthesis of MCs are induced by short-period plasma treatment. The comprehensive regulations of genes associated with physiological processes are potentially responsible for long-term inactivation of M. aeruginosa. This work therefore proposes a type of feasible advanced oxidation process (AOPs) to utilization of DBD plasma that achieves effective short-term and long-term inactivation efficacy of M. aeruginosa.