Modulation Of Drinking Water Microbial Community And Tap Water Risk Control Based On Surface Modification Of Biological Activated Carbon

Water is the source of life,as without water,there is no life.With the improvement of living standards,people's requirements of drinking water are increasingly strict,and the demand for safe drinking water cannot be ignored anymore.Although after a series of conventional treatment of drinking water treatment plants,the treated water has reached the national standard.However,when the treated water flows through the drinking water distribution systems(DWDSs),the water quality may deteriorate,causing secondary pollution of tap water,and the antibiotic resistant genes(ARGs)risk and disinfection by-products(DBPs)problems are typical secondary pollution of tap water.In this paper,based on the idea of microbial shaping to regulate the microbial community structure of biological activated carbon(BAC)filter and DWDSs,we further improve the water quality in DWDSs,reduce the ARGs risk and the DBPs problem in tap water through Fe modified granular activated carbon(Fe/GAC).The main contents and conclusions of this research are as follows.(1)The BAC filtration was established based on Fe/GAC to study the effect of Fe/GAC on drinking water quality during BAC filtration and DWDSs distribution.Compared to GAC,Fe/GAC bio-filtration had a sustained inhibition of ARGs in tap water.Fe/GAC provided a new extracellular electron transfer pathway of“organic matter-Fe₂O₃-biofilm”,which improved the extracellular electron transfer rate and weakened the pressure of organic pollutants to the Fe/GAC surface microorganisms,resulting in a significantly lower relative abundance of ARGs on the Fe/GAC surface microorganisms.Meanwhile,Fe/GAC bio-filtration inhibited the microbial aggregate growth which significantly correlated with ARGs by shaping the microbial community structure of the water.In addition,the attached biofilm on Fe/GAC was not easily dislodged,and the suspended biofilm in water was not easily aggregated,which inhibited the horizontal gene transfer of ARGs and metabolism of microorganisms,and successfully controlled the risk of ARGs from BAC filtration effluent to tap water.(2)In the BAC filtration,trace antibiotics(1?g/L each of ciprofloxacin,sulfadoxine and chloramphenicol)were added to study the impact of Fe/GAC bio-filtration on the water quality of composite micro-polluted drinking water.Fe/GAC bio-filtration process achieved synergistic control of ARGs and DBPs during BAC filtration and DWDSs distribution.Fe/GAC effectively reduced the direct interaction between trace antibiotics and microorganisms by enhancing the interaction between Fe/GAC and microorganisms,which based on the direct electron gain of cytochrome c from Fe₂O₃ and the diminished expression of the oxidative phosphorylation pathway.Meanwhile,by more sustainable shaping effect on the microbial community structure,Fe/GAC bio-filtration decreased the relative abundance of potential hosts of ARGs,and effectively inhibited the quorum sensing among microorganisms to achieve sustainable control of ARGs The extracellular polymers secreted by microorganisms on Fe/GAC surface were dominated by polysaccharides,and the adhesion of polysaccharides was the dominant mechanism of biofilm coalescence,inhibiting the detachment of biofilms.The formation of aggregates in DWDSs was still prevents due to electrostatic repulsion,which was conducive to reducing the generation of DBPs and inhibiting the horizontal gene transfer of ARGs.Thus,Fe/GAC bio-filtration achieved synergistic control of ARGs and DBPs in composite micro-polluted drinking water.