| With the rapid growth of population and development of animal husbandry in recent years,the demand for antibiotics have reached a huge amount.Tetracycline hydrochloride(TCH)is a typical antibiotic pollutant with high toxicity and persistence,and it is widely found in natural rivers,groundwater,soil and sediments.Consequently,the treatment of TCH antibiotic contaminated wastewater is an urgent problem to be solved.Microbial fuel cell(MFC)is an emerging environmentally friendly treatment technology that integrates microbial and electrochemical processes.However,MFC is prone to pH differentiation in long-term operation,which reduces efficiency.Therefore,this study firstly started from dual-chamber MFC degradation TCH to study the synergistic effect of TCH degradation and MFC electricity generation as well as microbial community structure.Secondly,according to the pH problem of MFC,polarity reversal MFC was carried out to explore the feasibility of pH differentiation control and electron transfer mechanism,and identify the polarity reversal functional bacteria.Finally,the polarity reversal MFC was used to compare TCH degradation with non-reversal conditions to determine the possible pathway of TCH degradation and clarify its electron transfer mechanism and microbial mechanism.The main results are as follows:(1)The degradation of TCH and the generation of related electron mediators in dual-chamber microbial fuel cell(MFC)are studied.TCH could be effectively removed(>93%)in MFCs mode.The maximum COD removal was 88.14±1.47%in MFCs while it was 69.57±1.36%in open circuit MFCs.According to cyclic voltammetry,the presence of the relevant redox peaks clearly suggested that the intermediates from TCH degradation could act as endogenous electron mediator.The highest power density of 120.02±2.76 m W/m~2 and the lowest internal resistance of 18.68Ωwere achieved in MFC with 2 mg/L of TCH.Microbial community analysis illustrated that Bacteroides,Comamonas,Clostridium＿sensu＿stricto,Desulfovibrio and Geobacter were enriched and played a dominant role in TCH degradation and power generation.Electrochemical active bacteria had certain tolerance to TCH and the inhibiting threshold value of TCH was below 5 mg/L.(2)The pH,electron transfer mechanism and functional microorganisms of two-chamber MFC under periodic polarity reversal were investigated.Polarity reversal MFC can obtain a steady voltage output of 0.20-0.25V for a long-term operation simultaneously cathode and anode pH realize self-neutralizationand.Polarity reversal improves the performance of anode and cathode,the power density increased by48.38%,and the internal resistance decreased by 46.55%compared with non-polarity reversal MFC.After polarity reversal,the maximum power density increased to 105.53±4.22 m W/m~2 and the internal resistance decreased to 433.45Ω.According to cyclic voltammetry,the mechanism of extracellular electron transfer in polarity reversal biological electrode is a combination of indirect and direct electron transfer mechanism.Microbial community analysis indicated that Comamonas and Shinella with bidirectional electron transfer could be enriched as potential polarity reversal bacteria.(3)Combined with the above two experiments,the degradation of TCH with different concentrations by polarity reversal MFC was explored,and the degradation of TCH was characterized by electrochemical method and microbial method.It is found that polarity reversal MFC can also effectively degrade TCH(>97%).Electrochemically active bacteria(EAB)have a certain tolerance to TCH.Under the condition of non-polarity reversal,the electrochemical performance of EAB is the best at 2 mg/L TCH,while under the condition of polarity reversal,the electrochemical performance of EAB is the best at 1 mg/L TCH,with the highest power density of 98.07±3.28 m W/m~2.Compared with non-polarity reversal MFC,polarity reversal MFC had a higher proportion in Clostridium＿sensu＿stricto and Comamonas,which improved the degradation efficiency of TCH,and Comamonas and Shinella were enriched as polarity reversed bacteria.This study provides a basis for the application of polarity reversal MFC in antibiotic degradation. |
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