| Antibiotic resistance genes（ARGs）are defined as a new type of pollutants due to their potential harm,persistence and spread.The ARGs contained in natural water such as rivers or sewage will enter the drinking water distribution system with the water flow and continue to spread through a small number of microorganisms in drinking water.Therefore,exploring the distribution and removal mechanism of ARGs in the water supply network has important guiding significance for controlling ARGs pollution and ensuring residents’drinking water safety.In this study,the biofilm reactor was used to simulate the water supply network system,and about 0.5 mg/L of chlorine and chloramine were added to the reactor to maintain a stable concentration during operation.A water purifier containing common filtration process was connected in series after each reactor,and used normally every day.After the operation,the effluent and biofilm of the pipe network were taken for 60 m J/cm2 low-pressure ultraviolet disinfection.High-throughput quantitative PCR and metagenomic sequencing were used to analyze and compare the differences in the diffusion and control laws of ARGs in chlorine and chloramine pipe network water/terminal ultraviolet disinfection,chlorine and chloramine pipe network water/terminal water purifiers.The research results are as follows:（1）After 150 days,the total relative abundance of ARGs in the effluent of the pipe network after chlorine and chloramine disinfection were 1.30×10-1 and 1.37×10-1,and 2.45×100 and 2.77×10-1 in biofilms,respectively.It was showed that low-dose chlorine or chloramine in the pipe network can effectively reduce the relative abundance of ARGs in the water phase and biofilm phase,and chloramine disinfection has a more significant control effect on ARGs in biofilm.（2）After UV disinfection,the relative abundance of ARGs in chlorine and chloramine disinfected pipe network water were 6.82×10-2 and 5.37×10-2,respectively.The relative abundances of ARGs in biofilms were 2.01×100 and 1.94×10-1,respectively.It was showed that setting the ultraviolet disinfection process at the terminal can significantly reduce the abundance of ARGs in the chlorine and chloramine disinfected pipe network water,but it has less effect on the ARGs in the pipe network biofilm.（3）After filtering through the water purifier,the diversity of the bacterial community in the effluent of chlorine disinfection decreased,of which the proportion ofβ-proteobacteria was the largest,at 58.09%,while the diversity of the bacterial community in the effluent of chloramine disinfection increased,in which the abundance ofα-proteobacteria was the largest,at 48.77%.The results showed that the terminal water purifier with filtration process not only purifies the water but also provides an ideal growth environment for bacteria.The relative abundance of ARGs in the effluent of the two groups of water purifiers were 5.24×10-2 and 2.97×10-2,and the main resistance mechanisms were Antibiotic efflux.（4）Compared with the pipe network water/terminal ultraviolet disinfection,the pipe network water/terminal water purifier had a strong reduction effect on high-abundance ARGs,but it had poor removal effect on low-abundance ARGs.The network analysis showed that there was a positive correlation between a large number of ARGs,MGEs and low-abundance bacteria（P<0.05）,while high-abundance bacteria were only positively correlated with a small number of ARGs（P<0.05）,indicating that ARGs in drinking water after terminal water purifier can be spread under the joint action of MGEs and bacterial communities.In addition,91.76%of ARGs were positively correlated with virulence factor genes（VFGs）（P<0.05）,indicating that there are a variety of resistant and pathogenic bacteria in the filtered drinking water,which has a greater impact on disease infection and antibiotic treatment. |
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