Combined Effects Of In Situ Remediation Of Eutrophic Water Bodies And Sediments By Magnetite Strengthened Anodic Sediment Microbial Fuel Cells

With the accelerated urbanization,the discharge of sewage from agricultural fertilization,animal husbandry and industrial wastewater has led to more nutrients entering surface water and sediments,causing serious damage to the environment and ecosystem and affecting the ecological functions of rivers and lakes.In eutrophic water bodies,as algae die and decompose,some were broken down in the water column and nutrients were released from the algae into the water column again,increasing the internal load of algae-derived nutrients in the lake,while promoting the migration and transformation of endogenous nutrient sources in the lake sediment.In this study,Sediment Microbial Fuel Cell（SMFC）technology was used for integrated in situ remediation of eutrophic waters and sediments to address the pollution problem of nutrient in-load in eutrophic waters and sediments.The effect of bioelectrochemistry of Microbial Fuel Cell（MFC）on nitrogen,phosphorus and iron morphology in sediment was firstly investigated,and the mechanism of magnetite enhanced anode electron shuttle and enrichment of electricity producing bacteria improved the removal of organic carbon from sediment and enhanced the electricity producing performance of the system.Secondly,magnetite-modified anodes were used in a real sediment-based microbial fuel cell system to demonstrate the feasibility of Fe-SMFC power production and efficient removal of nitrate and nitrogen from the overlying water.Finally,Fe-SMFC was combined with submerged plants to study the comprehensive effect of Fe-SMFC in situ remediation in water bodies and sediments,and to investigated the relationship between anode microbial community structure,electricity production performance parameters and nutrient in-load removal,providing a new method and technical means for the comprehensive management of nutrient in-load in eutrophic water bodies and sediments.The main findings of the study were as follows（1）In the two-chamber MFC system,the magnetite attached to the anode can significantly improve the power production performance of the system.The MFC system had the maximum power density（1.133 W/m³）when the monolithic loading was about 0.068 g,and the internal resistance was reduced by 21.92%compared with the control group.The magnetite-enhanced anode was enriched with Geobacter and Tolumonas,which are related to electricity production and iron redox.（2）In the two-chamber MFC system,magnetite-reinforced anodes can promote the removal of organic carbon from sediments by MFC.the removal rate of organic carbon in the experimental MFC group reached 60.69%,which was 19.84%higher than that in the control group;the improvement of the electrical production performance of the MFC system promotes the conversion of total nitrogen to transformable nitrogen and the formation of SOEF-N,WAEF-N and SAEF-N,leading to the reduction of the anode SOEF-N and IEF-N content.The MFC leads to lower Na OH-P content in the sediment and inhibits the formation of Ca-P.The content of CARB-Fe is negatively correlated with the content of organic carbon,and MFC promotes the formation of CARB-Fe in the sediment,and the MFC electricity production promotes the transformation of nitrogen,phosphorus and iron forms in the sediment to a more active form.（3）In the SMFC system,the magnetite-reinforced anode compounded with the bio-cathode improved the power production capacity of the SMFC system;the maximum voltage of the Fe₃O₄-Bio-SMFC group reached 250 m V and the maximum power density was 1.06 W/m3.The internal resistance of the Fe₃O₄-Bio-SMFC group was reduced by 56%compared with that of the control group;the bio-cathode could make nitrate nitrogen become the electron acceptor in the cathode region.While increasing the electron utilization efficiency of the cathode,the removal of nitrate nitrogen from the overlying water was achieved by denitrification,and the degradation rate of nitrate nitrogen in the overlying water of Fe₃O₄-Bio-SMFC group was 68.9%.（4）In the P-SMFC in situ remediation of water and sediment system,the P-SMFC system with submerged plants coupled with magnetite modified anodes could significantly promote the removal of pollutants from the overlying water.the removal of nitrate nitrogen,ammonia nitrogen,phosphate and COD from the overlying water by Fe₃O₄-P-SMFC was classified as 70.4%,85.19%,88.05%and 86.48%.The removal rates of total nitrogen,total phosphorus and organic carbon from sediment were 25.8%,10.14%and 26.6%,respectively.The submerged plant-coupled SMFC system can not only inhibit the diffusion of pollutants in the overlying water into the sediment through SMFC,but also promote the utilization of pollutants in the sediment by the P-SMFC system through the synergistic effect of plant root secretions and microorganisms.