| Water-borne pathogens were posed a threat to human health and need to be eliminated in the water treatment process,especially in the disinfection process.At the same time,antibiotic resistance genes（ARGs）and viable but non-culturable（VBNC）bacteria,as the emergence of two emerging pollutants,have further increased the hidden dangers of public safety.Traditional water treatment and disinfection techniques,such as chlorination and ultraviolet radiation disinfection,have defected such as the generation of disinfection by-products（DBPs）,poor sterilization effect,and limited removal of ARGs.Therefore,it is necessary to develop a new disinfection technology.In recent years,low-temperature plasma water treatment technology has attracted more and more researchers’attention in the field of water disinfection due to its environmental friendliness,high efficiency and thoroughness.In this thesis,an atmospheric-pressure air-liquid discharge plasma（ALDP）device with uniform and stable discharge was built,where the active species formed in the gas phase were introduced into the liquid phase by high-speed airflow.By determining the culturability,VBNC bacteria,ARGs and other aspects,the inactivation efficiency of ALDP against Gram-negative（G-）and Gram-positive（G+）model strains and environmental samples from a surface water and waste water treatment plant（WWTP）effluent were tested with chlorination and Ultraviolet as the control.And the possible mechanisms of bactericidal and ARGs removal were explained.The main results achieved were as follows,（1）In this study,the inactivation effect of ALDP on Escherichia coli（E.coli）,Pseudomonas aeruginosa（P.aeruginosa）,Salmonella sp.and Staphylococcus aureus（S.aureus）was systematically evaluated.The results showed that the three G-bacteria were completely inactivated by 7.10 logs and the G+bacteria exceeded 4.61 logs by plasma treatment in 10 min.Compared with chlorination（1 mg/L,2 mg/L）and UV（24 m J/cm2,32 m J/cm2）,the disinfection effect of ALDP had obvious advantages.For the three Gram-negative bacteria,ALDP resulted in lower levels of VBNC cells（about 102–103times）than chlorination treatments.（2）ALDP could efficiently remove intracellular ARGs（i-ARGs）and extracellular ARGs（e-ARGs）.The results showed that two resistance genes carried by the plasmid in antibiotic-resistant bacteria E.coli HB101,i-bla TEM and i-tet C decreased by 4.49 logs and 4.32 logs,e-bla TEM and i-tet C decreased by 2.05 logs and 1.34 logs,respectively,and their levels reached the detection limit after removal.For the specific genes carried by the chromosomes of the four type strains,more than 96.41%of the i-DNA were removed after 10 min treatment of ALDP,while the chlorination was 56.35%.（3）The cell structure was destroyed during the ALDP treatment.The generation of·OH,·1O2and·O2-were detected by the electron paramagnetic resonance spectroscopy during the discharge process,and the membrane permeability and the intracellular reactive oxygen species were detected by flow cytometry.The results showed that membrane integrity was impaired after 1 min of the ALDP treatment.Combined with the detection results of intracellular reactive oxygen species,plasma treatment led to a rapid increase of intracellular reactive oxygen species within 30 s,but decreased after 1 min,indicating that the cell structure has been severely damaged.It proved that the contents of the cells were leaked, resulting in cell death,revealing the possible oxidative damage mechanism of bacteria by ALDP（4）For the actual environmental samples,the bacterial inactivation rate in Furong Lake reached 99.82%after ALDP treatment for 10 min,and the bacterial inactivation rate of the WWTP effluent was 97.77%.Regardless of the residual chlorine concentration of 1 mg/L or 2 mg/L,the bacterial inactivation rate was lower than 97.41%.The effect of UV treatment on actual samples also has obvious disadvantages compared with ALDP.When the doses of UV254were 24 m J/cm2and 36 m J/cm2respectively,the bacterial inactivation rate in Furong Lake water and effluent of domestic sewage treatment plant was lower than 99.62%.Further analysis of the microbial community structure showed that ALDP could remove chlorine-resistant bacteria.In addition,through energy consumption analysis,ALDP had higher energy yield than other advanced oxidation processes through energy consumption analysis.To sum up,ALDP had obvious advantages in disinfection ability,especially the inactivation of pathogenic microorganisms.It can be used as a supplement or replacement for traditional disinfection method,and provides an important reference for the development and application of new microorganism removal technologies. |
