| Human’s high consumption of antibiotics results in the wide distribution of antibiotics in various environments.Antibiotics not only promote the development of Antibiotic Resistant Bacteria(ARB),It caused problems with Antibiotic Resistance Genes(ARGs).In addition,ARGs spread among microbial species through Mobile genetic elements(MGEs)such as plasmids and integrons,further increasing the risk of microbial resistance,which may affect human and animal health.In order to further understand and solve the problem of bacterial drug resistance,this study established a new advanced oxidation system of UV light-emitting diode activated peracetic acid(UV/PAA)to control the pollution of ARBs and ARGs in water.In this study,Escherichia coli carrying sul 1 and ampicillin resistance gene(amp)was selected as the research object to investigate the removal efficiency of ARBs and ARGs by PAA oxidation alone,UV irradiation alone and UV/PAA system respectively.The removal efficiency of UV/PAA system on ARBs and ARGs was investigated by changing UV light source,water substrate conditions and process parameters.In this study,free radical capture experiments were used to determine the dominant free radicals of ARGs removed by UV/PAA,and combined with the damage of UV/PAA on ARB bacteria and ARGs,the potential mechanism of UV/PAA removal of ARBs and ARGs in water was further investigated.This study provides some theoretical support for controlling and solving the pollution problem of ARBs and ARGs,and provides a new research idea for removing ARBs and ARGs in water.The results showed that the inactivation efficiency of PAA oxidation system alone was much lower than that of UV light and UV/PAA system alone,and there was no significant difference between UV light and UV/PAA system in inactivation of ARB.When the UV dose is 4 m J/cm~2,the inactivation rate of ARB can reach nearly 6 log by UV irradiation alone and UV/PAA system.Compared with ARBs,ARGs are more difficult to remove.Studies show that UV/PAA system has a better removal effect on ARGs,and the removal rates of sul 1 and amp reach 2.09 log and 1.91 log respectively at the highest dose of 500m J/cm~2.By comparing the removal efficiency of ARBs and ARGs with UV/PAA systems(254 nm,265 nm,285 nm),it was found that 265nm had the best effect in inactivating ARB and removing ARGs.When the experimental conditions such as PAA concentration,solution pH and other water substrate conditions and process parameters were changed,it was found that the UV/PAA system showed stable and efficient removal of ARGs when the pH changed in the range of 4-10,but the common chloride ions and carbonate/bicarbonate ions in water had an inhibitory effect on the reaction system.This may be related to the reaction of inorganic ions in water with free radicals generated in the UV/PAA reaction system.By Electron paramagnetic response(EPR)study,it was determined that Hydroxyl radical(·OH)was the main active radical in UV/PAA system.In addition,the contribution of hydroxyl free radicals in the system was quantitatively analyzed by using free radical trapping agent experiments.It was found that direct ultraviolet light played a major role in inactivating resistant bacteria,while the removal of resistance genes was mainly caused by the combined action of hydroxyl free radicals and direct ultraviolet photolysis.Flow cytometry analysis showed that the addition of PAA in UV/PAA system aggravated the damage effect of PAA on ARB cell membrane and increased the level of intracellular reactive oxygen species. |
PDF Full Text Request