| In the process for a number of ecological restoration,the research and application of artificial wetland attracted widespread attention,but its still not satisfied the technical requirements of advanced treatment of pollutants,the urgent need for artificial wetland technology in-depth knowledge and innovation.With the development of the theory of bioelectrochemical technology,configurations such as microbial fuel cells and microbial electrolytic cells have been derived.In this paper,constructed wetland coupled with bioelectrochemistry is the main method to study the removal and transformation process of water pollutants.This article research the power generation and decontamination effects of different substrates of constructed wetlands-microbial fuel cells on pollutants.Explores the performance and microbiology of different electrochemically enhanced constructed wetlands using pyrrhotite as the substrate including constructed wetland microbial fuel cells(CW-MFC),constructed wetland microbial electrolysis cell(CW-MEC)and the coupling of constructed wetland microbial electrolysis cell and fuel cell.The main research conclusions are as follows:1.Three different substrates(steel slag,sponge iron and pyrrhotite)were used to construct bio-electrochemically enhanced constructed wetlands.The maximum power density(11.025 m W/m2)obtained by sponge iron-MFC,better than pyrrhotite-MFC(2.048 m W/m2)and steel slag-MFC(0.091 m W/m2).There are obvious differences between the three substrates.These results are attributed to the difference in the electronic conductivity of the substrates.The internal resistance of sponge iron-MFC is lower than the other two substrates,and sponge iron has a better electron transfer channel.2.The CW-MFC system of the three substrates and the traditional constructed wetland system ran for 60 days to compare the removal effects of each substrate in the system.The removal rate of various pollutants showed that the removal of COD was not only the traditional wetland microbial metabolism utilization,but the electrochemical process strengthens the microbes to use the electrons generated by the carbon source to react.The removal of TP can be removed by the adsorption and precipitation of the substrate,the absorption and metabolism of microorganisms,and the release and re-precipitation of Fe in the electrochemical process.Sponge iron-MFC has excellent pollutant removal performance,but the sponge iron substrate promotes the process of heterotrophic denitrification.The current generated by the MFC in the coupled electrochemical system is supplied to the MEC for electrolysis,and does not directly mediate the heterotrophic reducing ammonia function microorganisms near the cathode.The advantage of the coupled system lies in the pollutant removal mode in the form of energy selfsustaining used in electricity production and MEC.3.The diversity of the microbial community structure between the MFC group and the CW group was quite different.The MFC group has a strong selective enrichment ability due to electroactive microorganisms,sulfur oxidizing bacteria,and sulfur reducing bacteria.The MFC has a strong ability to remove COD,which is positively related to the power generation performance of the MFC group.According to the LEFse analysis,there are fewer specific microorganisms in the MFC group than in the CW group,indicating that the microbial functions of the MFC group are more concentrated,which corresponds to the rich flora of characteristic microorganisms.The CW-MFC of the pyrrhotite substrate has higher species complexity than CW-MEC.The two groups of CW-MEC and CW-MFC overlap with CW,indicating that some of the microbial communities and functions of CW-MEC and CW-MFC are comparable to CW.There is a similarity of origin.The RDA analysis shows that the removal of TP has no significant correlation with nitrate nitrogen and ammonia nitrogen,and the removal of TP has a positive correlation with the concentration of COD and total iron.In summary,this thesis studies the effect of different substrates of MFC and different types of electrochemical enhancement devices on the removal of pollutants in water,and systematically reveals the conversion process and coupling mechanism of the bioelectrochemical configuration for pollutant removal.To provide key information for more efficient use of bioelectrochemical technology to strengthen ecological restoration of water,and provide important parameters and necessary scientific foundation for the application of large-scale integrated constructed wetland-bioelectrochemical systems in actual polluted waters. |
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