Inhibition Effect And Mechanism Of Non-thermal Plasma On Cyanobacteria

Frequent outbreaks of cyanobacteria blooms could cause ecological disasters such as fish deaths,decline in biodiversity,and degradation of lake ecological structure and functions.In addition,cyanobacteria blooms outbreaks could cause environmental safety issues such as human health damage.At present,the effective control of cyanobacteria blooms has become a global issue.Non-thermal plasma integrates light,electricity and chemical oxidation.Non-thermal plasma had the functions of electric field force,charged particles,shock wave,ultraviolet radiation,and oxidation of free radicals and active substances.Therefore,non-thermal plasma had an efficient algae removal effect and was expected to overcome the limitations of traditional algae removal technology.Acoaxial three electrode DBD reactor was designed by selecting various parameters.non-thermal plasma was generated by discharge in liquid to carry out research on the inhibitory effect and mechanism of the dominant algae Microcystis aeruginosa.The main research contents are as follows:Study the changes of various physical and chemical indicators in the reaction system,and explore the influence of inactivation conditions on the inhibitory effect of Microcystis aeruginosa.The changes of physicochemical properties and the degradation of MCs and AOM were determined.Combined with observing the morphology of algae cells,the inhibitory effect of non-thermal plasma on Microcystis aeruginosa was determined.The mechanism of algae removal by non-thermal plasma was preliminarily explored.New opinion and theoretical guidance were provided for the popularization and application of non-thermal plasma technology.The following conclusions were drawn through experimental research:（1）The treatment time was positively correlated with the inactivation rate of Microcystis aeruginosa.When treatment time is longer,inactivation rate is higher.When the initial concentration was too high,the inactivation rate slightly decreased,but the overall inactivation effect was good.Low p H（p H=3）and short time heating（35℃within 30 min）could promote the inactivation,but they were not the main factors that cause the inactivation of algae cells.（2）In the process of non-thermal plasma produced by liquid discharge,numerous strong oxidation active substances such as H₂O₂ and O₃ were produced.After three times treatment,the concentrations of H₂O₂and O₃ were 270.71μmol·L^-1 and 5.57μmol·L^-1.The inactivation of different initial algae concentrations reached 98%,92%,87%,84%.The results showed that the non-thermal plasma could effectively control algae cells.（3）Algal cells were destroyed by non-thermal plasma,and the concentration of microcystins was 0;AOM were released.When the initial OD was 0.1,the total fluorescence intensity of each component decreased from 1257 to 173.When the initial OD was 0.2,the total fluorescence intensity of each component decreased from 3100 to 209.When the initial OD was 0.3,the total fluorescence intensity of each component decreased from4472 to 478.When the initial OD was 0.4,the total fluorescence intensity of each component decreased from 6206 to 434.MCs and AOM released from cells could be degraded by non-thermal plasma without significant toxic effects.（4）After the non-thermal plasma inactivated Microcystis aeruginosa,the degradation rate of chlorophyll reacheed more than 90%.Observed by SEM,numerous algal cells atrophied and ruptured,and the structure of algal cells was significantly damaged;MCs concentration was lower than the detection line,and the AOM in algae cells was decomposed thoroughly.It showed that the inactivation mechanism of non-thermal plasma discharge in liquid on algae cells is the result of the combined effects of strong plasma oxidation,mechanical fragmentation,ultraviolet radiation and low pH.