Research On The Performance Of Constructed Wetland-microbial Fuel Cell System For Wastewater Treatment And Power Generation

In this study,the vertical up-flow constructed wetland was used to construct the air cathode microbial fuel cell,forming a new sewage treatment and environmental productivity technology,namely the constructed wetland-microbial fuel cell coupled system（CW-MFC）.The main research contents and results were as follows:（1）The output voltage of CW-MFC system in the start-up process and the changes of various water quality indexes of CW-MFC system and CW system effluent were explored.CW-MFC system and CW system used manual water distribution as the substrate in the process of start-up and long-term operation.And the system used continuous flow to feed water.CW system was used as control group.It was found that the output voltage of CW-MFC system is about 300 m V at the start-up stage.The average removal rates of COD,NH₄⁺-N,TP in CW-MFC system were respectively 85.97±1.87%,76.47±2.73%and56.07±9.21%.The average removal rates of COD,NH₄⁺-N and TP in CW system were respectively 77.16±1.54%,71.77±4.37%and 50.73±8.42%.The DO along the path of the two system changed similarly,and the effluent from cathode is in aerobic state and has strong resilience.The p H of effluent is about 7.5,and the Canna indica grew well during the start-up process.（2）The effects of influent COD load,HRT and external resistance on pollutant removal and power generation performance of CW-MFC system were studied,and the optimal parameters of the system were determined.According to the comprehensive comparison of pollutant removal effect and power generation performance of the system,the research results showed that the optimal influent COD concentration of the CW-MFC system was 200 mg/L,the optimal HRT was 24 h,and the optimal external resistance was1000Ω.Under these conditions,the average removal rates of COD,NH₄⁺-N,NO₃^--N and TP were 85.09±0.75%,89.97±2.79%,90.91±2.32%and 60.11±1.11%,respectively.Meanwhile,the average output voltage,maximum power density,internal resistance and coulomb efficiency of CW-MFC system were 394 m V,107.54 m W/m³,436.79Ωand0.97%,respectively.（3）At the same time,the Excitation Emission Matrix Spectra and PARAFAC method were combined to characterize the change of DOM in the effluent during the stable operation of CW-MFC system,which provided help for the fluorescence spectrum monitoring of CW-MFC.The results showed that:it was found that the fluorescence of protein like peak gradually weakened and the fluorescence of fulvic acid like peak gradually strengthened from the cyclic fluorescence spectrum of circulating influent.The relative concentration of fluorescent substances in the start-up process was inversed by the fluorescence intensity score during the start-up process,and the fluorescent substances in the effluent from the start-up stage to the stable operation stage of CW-MFC reactor gradually decreased and tended to be stable.At the same time,it was found that protein like and humic acid were significantly positively correlated with COD,while fulvic acid had no correlation with COD.The EEMs of the effluent were analyzed by PARAFAC,it was found that the concentration of fulvic acid like substances in the effluent increased significantly with the increase of HRT.In contrast,the changes of tryptophan like and humic acid like substances were not significant,and showed a slight upward trend on the whole.（4）With the help of high-throughput sequencing technology,the dynamic changes of microbial community during the stable operation of CW-MFC system were revealed,and the characteristics and differences of microbial community structure under open-loop and closed-loop conditions were explored.The results showed that:the abundance and diversity of microbial community in CW-MFC system and CW system increased gradually,and the abundance and diversity of microbial species on the surface of anode layer in CW-MFC system were higher than those in CW system during the start-up process.In the process of stable operation,compared with the CW system,the optimization of parameters increased the abundance and diversity of microorganisms in the anode layer and cathode layer of CW-MFC system,but had little effect on the diversity of microorganisms in the bottom layer of CW-MFC system.At the phylum level,the dominant phylum of abundance in each layer of the system included Proteobacteria,Bacteroidetes,Chloroflexi,etc.The relative abundances of acidobacteria and Firmicutes in CW-MFC system were higher than those in CW system,and the relative abundances of Euryarchaeota in CW system were higher than those in CW-MFC system.In addition,the relative abundance of Chloroflex in the two systems was increased due to the influence of wetland plants.In CW-MFC system,the relative abundance of Firmicutes in cathode layer was higher than that in bottom layer.The increase of actinobacteria relative abundance in CW-MFC system could improve the removal efficiency and power generation capacity of the system.The distribution of microorganisms was related to the location of CW-MFC,and the difference between the microorganisms in the anode layer and cathode layer of CW-MFC system was obvious.Figure[59]table[13]reference[148]...