Effect Of Disinfectant And Hydrodynamics On Antibiotic Resistant Bacteria Distribution In Drinking Water Supply Network

The overuse of antibiotics has led to wide spread and diffusion of resistance genes(ARGs)and antibiotic resistant bacteria(ARBs)in aquatic environments,seriously threatening public health.Drinking water distribution system(DWDS)plays a vital role in ensuring water quality safety.Understanding how environmental conditions regulate bacteria resistance to antibiotics and the distribution of ARBs is essential to control ARBs and ARGs in DWDSs,which remains elusive yet.This study aimed at examing ARBs growth and biofilm formation under various disinfectants and hydrodynamics,and discovering the distribution patterns of ARBs and its impact mechanisms via con-structing static and dynamics simulation setups.Firstly,the effect of disinfectants on the distribution characteristics of ARBs under stagnant conditions was examined.The results showed that the addition of disinfectant(0.5-3.0 mg/L)posed an inhibitory effect on ARBs growth.Chlorine dosage of 3.0 mg/L decreased by 31.45?43.17%for four type of ARBs compared with none chlorine condi-tion.In contrast,1.0 mg/L chlorine promoted the ARBs proliferation in the biofilm phase compared to other chlorine dosages.Meanwhile,the attaching ratios of ARBs in-creased with chlorine dosages enlarging,with the highest ratios of 86.05?97.37%at 3.0mg/L chlorine.Positive correlation between biofilm,extracellular polymeric substances(EPS)and ARBs concentrations indicated that disinfectant shaped biofilm formation and EPS production,thus affectinng the growth,migration and transformation of ARBs and ARGs.Secondly,the effect of hydrodynamics on distribution characteristics of ARBs in the absence of disinfectants was investigated.The results show that the stagnant condi-tion promoted the ARB proliferation in the bulk water,while the transitional flow en-couraged the biolfilm ARBs,particularly for sulfamethoxazole and clindamycin re-sistant bacteria with the concentrations and ratios of 356.62 CFU/cm~2,8.37%,and319.30 CFU/cm~2,8.12%,respectively.Meanwhile,the ARB attaching ratio,biofilm biomass and EPS reached the maximum at the transition flow.Bacterial community analysis indicated the relative abundance of Proteobacteria of 79.34%when facing tran-sitional flow,among which?-proteobacteria and?-proteobacteria were predominant that are compotent to dominant biofilm formation and promote gene transfers between the same or different species.Finally,the effects of disinfectants on the ARB proliferation and distribution char-acteristics in response to various hydrodynamics were explored.The results showed that the attached ARBs under dynamic conditions exhibited the same pattern as those under the stagnant condition with chlorine dosage varying(0.0-1.0 mg/L),albiet displaying more significant impacts.The concentration of attached ARBs reached the maximum at the transitional flow in the absence of chlorine;while the transitional flow at 1.0 mg/L chlorine increased the proportion of attached ARBs,and promoted the ARB prolifera-tion in the bulk water.To summarize,the disinfectant and hydrodynamics collectively shaped in-situ hab-itat,development and detachment of biofilms and EPS secretion,thereby impacting the distribution of ARBs and ARGs in DWDSs.The study revealed that laminar flow and low chlorine level(0.5 mg/L)were the most favorable conditions to control the ARBs growth.This study provides a theoretical guidance and technical support for the control of transfers and dissemination of ARBs and ARGs in WDWSs..