Effects Of Drinking Water Treatment Process On The Microbial Community Structures And Their Antibiotic Resistance Activities

Some water sources in China are polluted by many antibiotics and antibiotic resistance genes(ARGs)due to the excessive use of antibiotics,posing a serious threat to human health through drinking water.As the current water treatment process can not entirely eliminate bacteria from drinking water,the determination of various types and content of bacteria and ARGs in drinking water system is critical for ensuring the quality and safety of drinking water.In the present study,Nanshi and Minhang water treatment process were selected and focused on.1)The effects of drinking water treatment processes on microbial community structures were analyzed by using 16 S rRNA high-throughput sequencing technology.It showed the effects of drinking water treatment processes on microbial community structure were similar.Proteobacteria showed stronger resistance to ozone disinfectant and chloramine disinfectant stresses,while Actinomycetes showed weaker resistance to disinfectant stresses.The relative abundance of Proteobacteria in the water was increased after biological activated carbon(BAC)filter.Actinomycetes were not suitable for growth on the surface of BAC,while they were suitable for growth on the biofilm of pipe network.High abundance bacteria plays an important role in maintaining the stability of the microbial community structure in water purification process,and microbial community with strong environmental stress resistance may have adaptive changes in environmental changes.Microbial community such as Erythrobacillus,Flavobacterium and Xanthomonas were relative abundance in raw water in Minghang district,Shanghai,and aeromonas showed strong resistance to antioxidant stress in treated water.Microbial community such as Azospira,Synechococcus,Bacteroides,and Pseudomonas sp.were relative abundance in raw water in Nanshi district,Shanghai,and Streptomyces showed strong resistance to antioxidant stress in treated water.Furthermore,both of Sphingobacterium and Bacillus showed strong resistance to antioxidant stress in different water purification processes.2)The presence of 3 kinds of integrons,8 kinds of transposons and 233 kinds of ARGs in drinking water treatment processes were detected by using high-throughput fluorescence quantitative PCR technology.The results showed that the effects of processes of sedimentation tank,preozonation-sand filtration and BAC filter on ARGs treatment were similar in drinking water treatment processes in two different water works.Preozonation-sand filtration processes could decrease the diversity and absolute concentration of ARGs and increase the relative abundance of ARGs.BAC filter process could increase the diversity,absolute concentration and relative abundance of ARGs and horizontally transferred genetic elements,and promote the transfer and dissemination of ARGs of sulfonamides and other efflux antibiotics in different microorganisms.Chloramine disinfection process had a significant effect on the removal of ARGs in Minghang drinking water treatment process.However,chloramine disinfection process significantly promote the transfer and dissemination of ARGs in the microbial community structure in Nanshi drinking water treatment process.3)26 strains which belonged to 16 genera were isolated and identified in Minghang drinking water treatment process.Among them,microorganisms in the genera of Bacillus sp,Sphingomonas sp,and Arcic rellaosea sp.had been detected in all the samples.The multiple drug resistance of these three kinds of microorganisms were stronger than other microorganisms in the presence of the same concentration of antibiotics.They were enhanced after BAC filter and water distribution pipe network,indicating BAC filter and water distribution pipe network played important roles in multiple drug resistance of microorganisms.Furthermore,culturable microorganisms with stronger antioxidant activities were easier to survive in the environmental stress condition during water purification process,thereby being easier to enhance their drug resistance abilities and obtaining and disseminating ARGs.