Study On Removal Of Vanadium(v) In Groundwater By Microbial Fuel Cells And Analysis Microbial Communities

With the rapid development of vanadium industry, the vanadium pollution in groundwater environment is becoming more and more serious. The toxicity of vanadium increases with valence and the most toxic one is vanadium(V). Compared with the traditional physical and chemical treatment process, the biological methods have cost effectiveness and environmental friendliness. In this study, single chamber air cathode microbial fuel cell was used to removal vanadium(V) in artificial groundwater solution. Carbon source and other factors were evaluated, and optimize operating conditions was achieved. In addition, community analysis and mechanism study were conducted for the anode microorganisms of the microbial fuel cell. The results are as follows:Simultaneous removal of vanadium(V) and organic compound as well as the recovery of electricity could achieve in the microbial fuel cell. Meanwhile, the selected four organics(glucose, acetate, citric acid, sodium salt, soluble starch) could be used as carbon and energy sources of the microbial fuel cell so that various functional microorganisms could deoxidize vanadium(V) and generate electricity. Through the comparison of electricity production performance(589.1 mW/m2) and vanadium(V) removal efficiency(77.6%), sodium acetate was defined as the optimal carbon source. Among the four operating factors, the effect of initial vanadium(V) concentration on performance of the microbial fuel cell was the most obvious, followed by the COD and conductivity, and the effect of external resistance was less obvious.Based on the single factor experiment results, three factors influencing the performance as the initial vanadium(V) concentration, initial COD concentration and conductivity was optimized by response surface method. With the lowest concentration of vanadium(V) at the end of the operation as the goal, the optimal results of the initial vanadium(V) concentration of 75.44 mg/L, initial COD concentration of 1007.48 mg/L, and the electrical conductivity of 11.98 mS/cm were achieved. Here the output power of the microbial fuel cell is 605.3 mW/m2 and the removal rate of vanadium(V) was 80.69%.Through the analysis of anode microorganism by molecular biology, the specific functional bacteria played a major role in the process of vanadium removal and power production were discovered. Dissimilatory metal reducing bacteria such as Enterobacter and Pseudomonas of Gammaproteobacteria, and the largest proportion of Actinobacteria(63.66%) and larger Spirochaetes(7.48%) can restore vanadium(V); electro-microorganisms such as Dysgonomonas of Bacteroidia Enterobacter and Pseudomonas of Gammaproteobacteria played a role of electricity production in microbial fuel cell; microorganism with sodium acetate as carbon and energy sources, as well as some fermented microorganisms played an important role in oxidation process and the vanadium(V) reduction reaction on its product.In summary, using the microbial fuel cell to remove vanadium(V) in groundwater is feasible, and sodium acetate has the best performance as a carbon source. By studying the effect of functional microorganism on vanadium reduction and electricity production, the optimal operation results are obtained to improve the removal efficiency of vanadium(V)in groundwater, which provides a reference for groundwater vanadium(V) pollution remediation in the future.