| The pollution of antibiotics in aqueous system induces the production and spread of antibiotic resistance bacteria and antibiotic resistance genes(ARGs),posing a serious risk to human health.Microbial fuel cell(MFC)is economic,environmental-friendly,effective and easily coupled with other processes,which make it a promising technology to treat antibiotic in wastewater.However,the effect of microbial electrochemical characteristics inside MFC on the degradation of antibiotics and the fate of ARGs remains unclear.In this study,plug-flow aerobic biocathode MFCs with external resistances of 1 Ω,10 Ω,100 Ω,1000 Ω and 5000 Ωrespectively were constructed,each exhibiting a different level of microbial electrochemical characteristics.Different concentrations of sulfamethoxazole(SMX)were dosed into the MFCs to explore the influence of microbial electrochemical characteristics on SMX degradation,ARGs fate and microbial community changes.Moreover,the effect of SMX on the microbial electrochemical characteristics of MFC was analyzed.The main conclusions are as follows:During the start-up period,steady-state the MFCs equipped with different external resistances reveal that the larger the external resistance,the greater the output voltage during the plateau period,the smaller the current intensity,and the more negative the anode potential.Besides,MFC with smaller external resistance can achieve higher maximum power density and lower internal resistance.After reaching steady-state performances,the MFCs dosed with SMX show that SMX removal efficiency with smaller external resistance(1 Ω,10 Ω and 100 Ω)significantly improved,followed by the MFC with larger external resistance(5000 Ω).However,the MFC with an external resistance of 1000 Ω has a lower removal efficiency.Correlation analysis shows that current intensity is a key factor to affect SMX degradation.In addition,the removal of SMX in MFC anode chamber follows the first-order reaction kinetics,and the reaction rate constant is linearly positively correlated with the SMX removal rate.Moreover,the microbial electrochemical characteristics in MFC do not affect the degradation pathway of SMX.SMX is degraded mainly by breaking the N-O bond on the isoxazole ring or breaking the bond between the benzene ring and the sulfonic acid group.The abundance of ARGs and microbial communities in MFCs with different external resistance were detected.It is found that the current in MFC increases the abundance of sul Ⅱgene,but decreases the abundance of int Ⅰ1,sul Ⅰ and sul Ⅲ.However,when the current intensity increases,the abundance of these three types of genes also tends to proliferate.Moreover,the current in MFC increases the richness,diversity and uniformity of microorganisms in the system,and selectively enriches Pseudomonas,Desulfovibrio,Rhodobacter and Simplicispira.The wastewater treatment test with different SMX concentration suggests that lowconcentration SMX(500 μg/L and 2 mg/L)may improve the output voltage,current intensity,and maximum output power density of MFC.Notably,smaller external resistance(1 Ω and 10Ω)enhances more significantly,while the effect of high concentration SMX(10 mg/L)weakens or even shows an inhibitory effect.The abundance of ARGs and microbial communities in the anode chamber were monitored when the MFC with an external resistance of 100 Ω treated different SMX concentrations.It was found that low concentration SMX(500 μg/L)showed a lower stress effect on ARGs.The relative abundance of ARGs hardly increased.While high concentration(2 mg/L,10 mg/L)SMX had a higher stress effect.The relative abundance of ARGs is increased significantly.In addition,as SMX concentration increases,the microbial richness,diversity and uniformity of microorganisms in MFC anode decrease.However,the potential SMX-degrading bacteria Desulfovibrio and Simplicispara were enriched. |
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