Inactivation Effect Of Microcystis Aeruginosa Based On Electrohydraulic Effect

To date,cyanobacteria have been intensively exploding throughout the world.The cyanobacterial outbreak not only causes deterioration of water quality,but also consumes a large amount of dissolved oxygen in water which harm the survival of other aquatic animals and plants.In addition,cyanobacterial toxins such as microcystins produced by cyanobacteria are also considered to be one of the major problems affecting water quality.Since the last century,humans have made many explorations and practices in algae removal,but there are certain shortcomings in algae removal methods.For example,biological algae removal methods often have long periods and high costs;chemical algae removal can cause secondary pollution;traditional physical removal methods has a high cost and a complicated process.In recent years,high-voltage pulse discharge technology has played a significant role in sand removal,gravel processing,food processing,water treatment applications,and inactivation of microorganisms.The series of physical and chemical effects that occur when high pressure discharges are carried out in liquids are called electrohydraulic effects,due to the high-efficiency and energy-saving of electro-hydraulic discharge,this paper(1)To explore the inactivation effect of discharge in liquid on Microcystis aeruginosa and the feasibility of its application in the treatment of Microcystis aeruginosa;(2)To investigate the effect of discharge in liquid on the inactivation of wild algae in Taihu Lake and its effect on the quality of algal water;(3)To discuss the preliminary mechanism of algae removal by liquid discharge technology.The results show that:(1)Compared with the control group,the OD value of the treatment group showed a decreasing trend after the discharge treatment of M.aeruginosa FACHB-905.However,the OD value of the control group showed an upward trend,indicating that the discharge in the liquid can inhibit the growth of Microcystis aeruginosa.The results show that the algae removal rate were55.50%,57.29%,57.29%,63.68%,61.64%,66.75%,84.91%,86.45%,91.05% respectively of 3kV and 100 discharges,3kV and 150 discharges,3kV and 200 discharges,4kV and 100 discharges,4kV and 150 discharges,4kV and 200 discharges,5kV and 100 discharges,5kV and 150 discharges,5kV and 200 discharges.The algal removal rate of 3kV,4kV,and 5kV were 56.56%,64.00%,and 87.56% respectively,and the difference was statistically significant(P<0.05).That is,as the voltage increased,the inactivation rate of algae increased.For the number of discharges,the inactivation rates of 100,150,and 200 discharges were 67.89%,68.44%,and 71.78% respectively.There were significant differences between 200 discharges and 150 discharges,100 discharges(P<0.05),but there was no statistical difference between 150 discharges and 100 discharges(P>0.05),that is,the effect of 200 times of discharge was better than that of 150 times discharge and 100 times discharge.The initial microcystins of Microcystis aeruginosa was 0.62 ?g/L,the control group increased to 1.0 ?g/L after 5 days culture,while the treated group was lower than the detection limit(0.1 ?g/L)after 5 days.This means that the electrohydraulic effect not only can inactivate Microcystis aeruginosa,but also have a significant degradation on microcystins.(2)The initial chlorophyll-a content of Taihu Lake wild algae is 217.50?g/L,after applying with 5kV voltage and 200 discharges treatment,the chlorophyll-a of the treated group is only 4.19?g/L at the ninth day,while the concentration of chlorophyll-a was 172.97?g/L in control group after 9 days of culture,the average removal rate was 98.07%,and some group can reach almost 100%.The initial algal toxin level in the wild algae in Taihu Lake was 4.06 ?g/L,after treatment with liquid discharge,the concentration of algae toxin in the treatment group decrease below the limit of detection(0.1 ?g/L)after 1 day of algae culture,meanwhile,the control group increased to 4.16 ?g/L.And similar to electro-hydraulic degradation effect of microcystins of Microcystis aeruginosa,electro-hydraulic effect can degrade microcystins of wild algae in Taihu Lake significantly.The content of TN,TP and COD in the algae water.Therefore,the electro-hydraulic discharge can not only inactivated the wild cyanobacteria,but also can improve water quality;(3)The morphological results of the cells before and after the discharge treatment showed that during the discharge process of the algal cells,the cell membrane ruptured and some of the cells were fragmented,and both the SOD and MDA of the cells immediately increased immediately after treatment and reached the highest level after one day of culture.The tendency to gradually decrease shows that the antioxidant defense system in the early algal cells is activated after the discharge of the algae in the liquid.However,due to excessive generation of free radicals,the cells lose their ability to resist oxidation and eventually cause cell death.The conclusion of this study:(1)The discharge in liquid has inactivation effect on Microcystis aeruginosa and can simultaneously degrade the MC-LR in water;(2)The electro-hydraulic discharge has a good effect on the inactivation of blue algae in Taihu Lake and can simultaneously degrade algal toxins in algae water,and reduce the TP,TN,and COD in water,this technology have a significant effect on improving water quality;(3)The principle mechanism of algae removal in liquid discharge may be that: a variety of physical and chemical reactions occur in the discharge process in the liquid,algae cells are physically and chemically damaged by discharge in the liquid,resulting in cell rupture,perforation,or breakdown of the antioxidant enzyme system.