Inactivation effect and mechanism of Microcystis aeruginosa by in-liquid pulsed discharge plasma

The harmful algal bloom outbreaks damage river and lake ecosystems and impact the environments of water bodies. Microcystis aeruginosa ( M. aeruginosa ) is the predominant algal species in cyanobacteria blooms, releasing toxins into the water column during its growth and decay. The rapid degradation of toxins and efficient inactivation of M. aeruginosa is a technical challenge. This study explores the use of in-liquid pulsed discharge plasma (LPDP) for the inactivation of M. aeruginosa . The investigation includes changes in the inactivation ratio, Chlorophyll-a (Chl-a) concentration, and the underlying inactivation mechanisms under various discharge conditions. This study achieved 100 % inactivation by plasma treatment for 20 min at a peak voltage of 30 kV and an electrode spacing of 7 mm, and the concentration of Chl-a was reduced from 1.08 mg/L to 0.14 mg/L (on the fourth day of re-culturing). The collaboration of ultraviolet light, strong electric fields, and reactive species (·O, H 2 O 2 , and O 3 ) generated during the discharge process induces apoptosis, reduces enzyme activity, and facilitates the removal of microcystins to realize green and efficient algal removal. In this work, in-liquid pulsed discharge plasma is used to treat algal blooms caused by eutrophication. The technology can restore the ecosystem of rivers and lakes by treating algal blooms quickly and efficiently without causing secondary pollution to water bodies. • The 100 % inactivation ratio can be realized in 20 min without adding gas and agentia. • LPDP damages the cell membrane, Chlorophyll-a and enzyme activity. • LPDP can efficient degrade microcystin without the risk of secondary pollution. • LPDP inactivation mechanism is attributed to multiple physicochemical effects.