The Effect Of UV/NaClO Combined Disinfection On Bacterial Reactivation And ARGs Repair And Microbal Community

In recent years,the pollution of antibiotic resistant bacteria（ARB）and antibiotic resistance genes（ARGs）caused by overuse of antibiotics has attracted wide attention.Disinfection is one of the important measures to control the spread of ARB and ARGs to the environment in the process of wastewater discharge or reuse.UV/NaClO combined disinfection can effectively reduce the ARB and ARGs,showing good application potential in the disinfection process of wastewater discharge or reuse.However,few studies have focused on the rule of microbial reactivation after UV/NaClO combined disinfection and its effect on microbial community structure and it is not conducive to the promotion and application of this technology.In order to explore the repair regularity of ARB and ARGs after UV/NaClO disinfection,and the influence of microbial community structure of this technology,this study used bacterial plate counting method and membrane filtration method combined with 16S r DNA analysis to compare and analyze the effects of UV disinfection alone and UV/NaClO combined disinfection on ARB and ARGs under the condition that the microbial indexes reached different effluent standards;The abundance of ARB and ARGs over time under light and dark conditions after disinfection was investigated;Illumina high-throughput sequencing and real-time q PCR were used to compare and analyze the differences in microbial community composition before and after UV disinfection alone,Na Cl O disinfection alone,and UV/NaClO disinfection.The results of this study can provide a theoretical reference for ensuring the ecology and human health safety of sewage discharge and recycling.The findings of the study are:（1）Study on the reactivation ability of bacterial after UV/NaClO combined disinfectionWhen the same effluent standard was reached,the photoresurrection and dark repair ability of coliform bacteria and ARB after UV/NaClO combined disinfection were significantly lower than UV disinfection alone,especially when the dosage of Na Cl O was higher,the inhibitory effect on reactivation was more obvious.Bacteria revival takes less time and has a higher rate of revival in light conditions than in dark conditions.After UV/NaClO combined disinfection,the photoregeneration rates of the four ARB investigated in this study in descending order from fast to slow were:AMP≈SM>TET>CHL.The dark repair rate is from fast to slow were:AMP>SM>CHL>TET,and after 24 h dark repair,the revival of TET was still not detected.（2）Study on the reactivation ability of ARGs after UV disinfection and UV/NaClO combined disinfectionWhen the same effluent standards was reached,the reactivation ability of ARGs after UV/NaClO combined disinfection is lower than UV disinfection alone.When the Class I A emission standard,the abundance of 18 ARGs increased by 384.34%and22.64%,respectively,compared with the gene abundance after disinfection,after the water samples were individually disinfected and combined with UV/NaClO and placed under light for 24 h.Compared with light repair,ARGs have a weaker ability to dark repair.UV/NaClO(UV dosage of 9 m J·cm^-2and 10 mg·L^-1Na Cl O)combined with disinfection and placed under light conditions for 24 h,the absolute abundance of ARGs reached 1.70×10⁴copies·m L^-1and 2.44×10³copies·m L^-1.（3）Analysis of microbial community structure after disinfection by different disinfection methodsThe potential hosts of different species of ARGs of the same class may be different,and the potential hosts of different types of ARGs of different species may be the same.Different disinfection methods have different effects on bacterial abundance,and the change of bacterial abundance after disinfection may be one of the reasons for the change of ARGs abundance during disinfection.Compared with UV and Na Cl O alone,UV/NaClO combined disinfection can remove bacteria that are insensitive to a single disinfectant.For example,the relative abundance of Proteobacteria after UV disinfection,Na Cl O disinfection and UV/NaClO combined disinfection was 29.88%,23.39%and 6.59%.There are differences in the effect of UV and Na Cl O disinfection on microorganisms.For example,the relative abundance of Chloroflexi in raw water was6.38%,and after UV dosage of 20 m J·cm^-2disinfection,the relative abundance increased to 8.73%,and the relative abundance was increased to 5.62%after 4 mg·L^-1Na Cl O,compared with UV/NaClO(UV dosage of 12 m J·cm^-2and 2 mg·L^-1Na Cl O),the relative abundance decreased to 1.83%,and UV/NaClO combined disinfection had the most obvious removal effect on Chloroflexi.