Removal Efficiency Of Typical Antibiotics-containing Wastewater By Miniture CW-MFC System

Constructed wetlands(CWs)coupling microbial fuel cells(MFCs)own the characteristics of converting chemical energy from organic pollutants into electricity while degrading pollutants,so they have broad application prospects in sewage treatment.This experiment proposes to combine CW and MFC to construct miniturc CW-MFC.The device is not only tiny in size,but also can generate bioelectricity while effectively removing pollutants from water,thus further enhancing the removal of pollutants.In addition,for the removal of new pollutants,especially antibiotics,this miniture system makes full use of ecological,biological,electrochemical and other mechanisms to strengthen the removal of antibiotics and simultaneously control the risk of loss and spread of resistance genes to the water environment.In this study,miniture CW-MFCs were established with circuit connection mode,varied influent carbon source concentration,substrate type and other factors t,so as to figure out the optimal construction parameters required for removal of typical antibiotics.Then,two representative zoological antibiotics,sulfamethoxazole(SMX)and tetracycline(TC),were selected to explore the removal,mechanism,and the regression of resistance genes as well as the electricity generation performance in the miniturc CW-MFC.In addition,investigation was conducted to examine the changes of microbial community structure in the CW-MFC system along with its varied substrates.The main results obtained are as follows:(1)The removal efficiency of COD,TP,NH4+-N and NO3--N by miniture CW-MFC and CW is different under various COD concentrations and different circuit operating modes.When the influent COD concentration is 150,300,450 and 600 mg/L,respectively,the average removal rate of COD in CW-MFC is 68.3%±6.7%,79.0%±2.2%,81.84%±2.03%and 79.07%±1.14%,respectively,with the maximum removal rate of 86.0%at influent COD concctration of 450 mg/L.In CW under the same influent condition,the average COD removal rate of each influent COD concentration is lower than 0.45%,0.29%,2.24%and 1.82%of CW-MFC,respectively.Overall,the removal performance of CW-MFC is better than that of CW.(2)Under long-term operation,the removal efficiency of conventional pollutants in the biochar substrate system is higher than that in the quartz sand based system.Compared to traditional substrates such as quartz sand,biochar can be used as an electron donor,especially for wetlands with low influent C/N ratios.By comparing the addition of s-Fe0 to the anode,the addition of s-Fe0 can effectively improve the pollutant removal performance of the system.(3)Both CW-MFC and CW have good TC removal efficiency.Under the same influent condition,the effluent antibiotic concentration of the two antibiotics of CW-MFC was lower than that of CW.The univariate variance analysis of CW-MFC and CW system shows that the effluent fluctuation of CW-MFC system is less than that of CW system,which has better stability and anti-impact load ability.Therefore,the processing performance of CW-MFC is obviously better than that of CW.When the influent concentration of antibiotics is 40,80 and 120 μg/mL,respectively,the average removal rate of SMX in CW-MFC system is 94.5%,and the lowest removal rate can reach 91.9%,and TC removal rates can reach 98.1%,96.0%and 94.8%,respectively.Most of the TC can be removed by the system.(4)In CW-MFC,when the influent antibiotic concentration increased from 40 μg/mL to 80μg/mL,the power density increased,but when the influent antibiotic concentration increased to 120 μg/mL,the power density decreased.In CW-MFC-2,the internal resistance of the system is low(439.646Ω),the maximum power density is 52.52 mW/m2,while the maximum voltage is 561.1mV and the maximum coulomb efficiency is 0.135%.This study shows that the output voltage of the system increases first and then decreases with the increase of the influent antibiotic concentration.The electrochemical action of the anode in the CW-MFC can promote antibiotic degrading bacteria to degrade antibiotics into small molecules of organic matter.(5)The addition of sponge iron can improve the relative abundance of firmicutes and actinomyces in the anode region of CW-MFC,and finally promote the biodegradation of antibiotics and improve the electricity generation performance of CW-MFC.In addition,in CWMFC,the presence of Proteobacteria,Firmicutes,Bacteroidetes,green flexobacteria and actinomyces can lead to the removal of most SMX through mineralization,and the presence of Bacteroidetes can catalyze the REDOX reaction in the cathode region.