The Principle Of Control Technology For Pathogenic Bacteria And Antibiotic Resistance Genes In Drinking Water By Quaternary Ammonium Salt Resin

The increasing findings of pathogenic bacteria and antibiotic resistance genes(ARGs)in drinking water has become one of the most challenging global health threats.However,conventional disinfection strategies in drinking water treatment plants(DWTPs)have some deficiencies in controlling antibiotic-resistant bacteria(ARB)and antibiotic resistance genes.Chlorination can effectively remove most bacteria,but only partially eliminates pathogens.Meanwhile,under the pressure of chlorine selection,the proportion of multidrug-resistant pathogenic bacteria and drug resistance genes that remained after disinfection increased remarkably.And ultraviolet radiation sterilization can induce the bacteria to a viable but nonculturable(VBNC)state.In this study,quaternary ammonium salt resin were employed as disinfection materials to control the pathogens and antibiotic resistance genes in drinking water.The impact of several operating parameters and environmental factors on the efficiency of removing bacteria by resin were systematically studied.The potential mechanism of antibacterial behavior of the resin was explored by investigating the bacteria numbers,the ratio of living bacteria to dead bacteria,the surface morphology and the intracellular dissolution.Combined with high throughput q-PCR technology and metagenomics bioinformatics methods to reveal the impact of the quaternary ammonium salt resin and conventional disinfection process on microbial community structure,the dynamic response mechanism of the absolute/relative abundance of pathogens and antibiotic resistance of residual bacteria in drinking water.The main conclusions of this study are following:(1)In the lab-scal experiment,the quaternary ammonium salt resin NDMP and MIEX can effectively remove gram-negative bacteria(Escherichia coli,Pseudomonas aeruginosa)and gram-positive bacteria(Bacillus subtilis,Staphylococcus aureus).The average removal efficiencies of quaternary ammonium salt resin for bacteria were 79.8～93.7%and 70.6～87.9%when the dosge was 100BV and reaction time was 1h;Compared with MIEX,the NDMP resin showed more efficient sterilization ability.With Bacillus subtilis as model bacteria,ionic strength(0.5～0.9 wt%),temperature(10～30℃)and natural organic matter concentration(2～10 mg/L)showed no significant influence on antibacterial behavior of quaternary ammonium salt resin.In addition,the quaternary ammonium resin maintained stable bactericidal ability during recycling,and its removal efficiencies were NDMP:90.1～94.1%,MIEX:81.2～93.8%,respectively.Using flow cytometry instrument combined with LIVE/DEAD staining agent,scanning electron microscopy(SEM)and the three-dimensional fluorescence spectrophotometer,reveals the change of the bacteria numbers,morphology and the intracellular dissolution before and after the quaternary ammonium salt resin treatment,the potential mechanism of antibacterial behavior of the quaternary ammonium salt resin was speculated.First,pathogens were separated from the water by bound to quaternary ammonium salt groups on the surface of resin through electrostatic interaction,then quaternary ammonium salt carbon chain group further destroy the cell membrane structure,triggering the dissolution of cytoplasm,and eventually leading to the death of bacteria.(2)The effects of quaternary ammonium salt resin coupled conventional disinfection technology on pathogens and antibiotic resistance genes in drinking water were evaluated by Heterotrophic plate counts(HPC)and high throughput q-PCR.The results showed that the quaternary ammonium salt resin can more effectively remove the total bacteria and pathogens in drinking water,especially for typical chloride/UV resistant bacteria in drinking water,such as Pseudomonas aeruginosa and Bacillus subtilis,the removal efficiency were 76.4～93.3%and 77.1～98.5%,respectively.At the same time,a total of 15 types of antibiotic resistance genes were detected in the actual water samples,mexB had the highest abundance in the effluent of sediment tank,with the concentration of 1.90×104 copies mL-1.All disinfection processes significantly reduced the absolute abundance of antibiotic resistant genes.However,the treatment of individual quaternary ammonium salt,chlorination and ultraviolet sterilization caused different degrees enrichment of some antibiotic resistance genes,only the combination of quaternary ammonium salt resin and low dosage of the chlorine(0.2 mg/L)reduced the absolute and relative abundance of all detected ARGs,provides a safe and effective auxiliary disinfection strategy to guarantee microbiological safety in drinking water.(3)Using high-throughput sequencing technology and metagenomics bioinformatics methods to explore the changes in abundance and species of antibiotic resistance genes,the co-occurrence mechanism of mobile genetic elements and the potential host of antibiotic resistance genes in drinking water under the different disinfection processes.The results showed that a total of 3022 antibiotic resistance genes were detected corresponds to different resistant mechanism,RND antibiotic efflux pump,ABC efflux pump and beta lactamase antibiotics accounted for 85.34～95.54%in all samples.The removal efficiencies of quaternary ammonium salt resin and quaternary ammonium salt resin-chloride coupling process for antibiotic resistance genes were 11.36%and 38.19%,respectively.While the relative abundance of ARGs in the water samples increased by 1.24 times after ozone disinfection.In addition,the disinfection process of different combinations changed the co-occurrence patterns of ARGs and MGEs in water bodies,about 23.35%of ARCs were found to carry multiple MGEs.Different disinfections had induced the alteration and the expansion of the bacterial hosts of antibiotic resistance genes in the water samples,and it is necessary to pay more attention to those bacteria in the disinfection processes.