| Antibiotics abuse and their induced resistant bacteria and resistance genes(ARGs)spread persistently in the aquatic environment,posing a serious threat to global health.Integrate microbial fuel cells(MFC)with membrane bioreactor(MBR)has several advantages: mitigate membrane fouling,improve effluent quality,reduce sludge discharge,and utilize bioenergy.MFC-MBR integrated systems reduce the release of antibiotic and ARGs to the environment,but membrane fouling remains a bottleneck problem which restrict the widespread application.The membrane fouling layers may become potential ARGs reservoir when increase the removal rate of antibiotics and ARGs.The role and mechanism of membrane fouling layers remain unclear.In this study,continuous flow MFC-MBR integrated systems were constructed to evaluate the operation performances,analyze the optimal sulfamethoxazole(SMX)concentration and quantify possible factors affecting SMX removal in foulants by adjusting SMX concentration and controlling different levels of fouling.Meanwhile,the abundance and fate of ARGs were investigated to elucidate the key role of membrane fouling layers in MFCMBR integrated systems.The main conclusions are as follows:The integrated systems treatments of synthetic domestic wastewater containing different concentrations of SMX were investigated.Higher SMX concentrations leaded to faster membrane fouling rates,and MFC delayed the development of membrane foulants.The runtime of the integrated system with 0.5 mg/L SMX was 48.3% longer than that of the higher concentration system(5.0 mg/L SMX),and 59.3% longer than that of the open circuit system.Compared with high SMX concentration(5.0 mg/L),low SMX concentration(0.5 mg/L,1.0mg/L)promoted MFC power production more effectively with a voltage increase of 20-47%.The anode zone,cathode zone and membrane were all involved in SMX removal.MFC contributed to increase the SMX removal rate compared to the open-circuit system.With the accumulation of membrane fouling,the SMX removal rate in the fouling layers experienced an SMX enrichment process followed by a SMX retention process.Multiple regression analysis showed that the removal rate of SMX in the membrane foulants become better as the extracellular polymeric substances(EPS)content increased and the protein/polysaccharide(PN/PS)ratio decreased.1 mg/L SMX maximized the removal potential of SMX in the integrated MFC-MBR system.Based on the optimal SMX removal concentration,the effects of different levels of membrane fouling in the MFC-MBR systems were studied.Compared to the cathode/anode zone,the membrane foulants played major roles in SMX reduction(39-47%).the intervention of SMX at the early stage of membrane fouling contributed the integrated system to further improve SMX removal rate in the later runtime.Compared to the EPS content,Lower PN/PS ratio was more critical to increase the SMX removal potential.The distribution and fate of ARGs abundances were detected.It was found that the ARGs abundance in the anode sludge and membrane fouling layer was higher than that in the anode supernatant and effluent.With the progressive thickening of fouling layers,the abundance of both intracellular ARGs(i ARGs)and extracellular ARGs(e ARGs)in the membrane foulants increased continuously,and i ARGs were predominant in the total ARGs.The progressively dense membrane fouling layers enriched ARGs,but the removal performance of the integrated systems on the effluent ARGs abundance were stable and reliable.The removal rate of e ARGs increased when the membrane foulants accumulated.The membrane fouling layers controlled the abundance of antibiotic resistant bacteria and ARGs in effluent through two mechanisms: reduce the effective pore size of membrane and retain ARGs by EPS/SMP efficiently.In addition,Bioelectrochemistry characteristics were effective in e ARGs reduction.The log removal of total e ARGs by the integrated system and open-circuit system was 5.49 and 3.65 by the highly-fouling membrane. |
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