Enhancement And Stability Of Electrode Dependent Anaerobic Ammonium Oxidation In Microbial Fuel Cells

The activity of anode electroactive biofilm is one of the important factors affecting the operation performance of MFC.According to the current research progress,MFC can cultivate electroactive anammox biofilms at the anode under specific conditions,and such electroactive biofilms have the ability to carry out anaerobic electrode ammonia oxidation（Electroammox）reaction.This study proposed by building a double chamber microbial fuel cell cultivation electroactive biofilm anaerobic ammonia oxidation,anode in microbial fuel cells in the occurrence of anaerobic ammonia oxidation electrode and strengthening research,again according to the actual characteristics of wastewater quality,to explore the influence of organic matter on anaerobic ammonia oxidation electrode,the electrochemical denitrification process completed based on the role of biological startup and optimization.This study is expected to provide theoretical basis and data support for the development and design of the new biological nitrogen removal process.The main research contents and results were as follows:（1）In the anaerobic condition,the two-compartment MFC with ammonia nitrogen as the only electron donor was used as the experimental device.By cultivating the electroactive anaerobic ammonium oxidation biofilm,the mechanism of Electroammox action was explored,and the ammonia-oxidation performance and microbial characteristics of Electroammox type MFC in the start-up stage were investigated.The experimental results showed that after 18 days of start-up,the electroactive anammox biofilm with nitrosomonas as the dominant strain could be formed on the surface of M1 and M2 anode,and the Electroammox action could occur in the system.During stable operation,nitrite nitrogen is the main product of ammonia nitrogen oxidation in MFC,the average conversion rate of ammonia nitrogen is 21.62%and 22.1%,respectively,and the average accumulation rate of nitrite nitrogen in effluent is 18.71%and 19.21%,respectively.M1and M2 can stabilize the output voltage,and the peak output voltage is 82.39m V and82.49m V,respectively.The peak power density is 282.84 m V/m²and 283.53 m V/m²,respectively,and the REDOX peak appears.According to the results of static tests,hydroxylamine should be the electron donor of the ammonia-oxidation capacity of electroactive microorganisms.（2）Based on the experimental results in（1）,the two-compartment MFC mentioned above was improved(labeled as M_E1and M_E2)by two enhancement measures（i.e.,potassium ferrocyanide was added into the cathode chamber and graphite particles were filled in the negative/anode chamber）,and then the enhancement study of Electroammox in the two-compartment MFC was carried out.The experimental results show that the performance of the two groups of systems gradually becomes stable after 22 days of operation in the strengthening stage.The average conversion rate of ammonia nitrogen is55.35%,and the average accumulation rate of nitrite nitrogen is 48.91%.The peak output voltage can reach 318.53 m V and the peak power density can reach 4227.56 m V/m².The average conversion rate of ammonia nitrogen is 40.99%,the average accumulation rate of nitrite nitrogen is 40.76%,the peak output voltage is 215.14m V,and the peak power density is 1928.55m V/m².The abundance of nitrosomonas on the surface of the biofilm with M_E1and M_E2electrodes was further increased,and the REDOX peak was more obvious.Compared with M_E2,M_E1has higher ammonia nitrogen conversion rate and nitrite nitrogen accumulation rate,so adding potassium ferrocyanide to cathode can better improve the intensity of Electroammox action in MFC.（3）Based on the test results in（2）,the influence of different concentrations of organic matter（0 mg/L,50 mg/L,150 mg/L,250 mg/L,350 mg/L,measured by COD）on Electroammox action in MFC was investigated.The experimental results show that when the concentration of organic matter in the influent is low（≤150 mg/L）,the Electroammox action intensity in MFC can be promoted,and denitrification occurs at the anode,which promotes the denitrification performance of Electroammox type MFC.Peak output voltage and peak output power density increase to 784.92 m V and 25670.68 m V/m²,respectively.When the influent concentration of organic matter increased to 250 mg/L,the TN removal rate of MFC and the conversion rate of NH4⁺-N began to decline,while the total NO_x^--N accumulation began to increase,Electroammox and denitrification began to be inhibited,and the peak output voltage and peak output power density also began to decline.Decreased to 669.02m V and 18649.75m V/m²;When the concentration of organic matter in the influent water was further increased to 350 mg/L,the activity of Aerobic ammonium oxidation bacteria（AOB）and denitrifying bacteria in the anodic electroactive biofilm of Electro Ammox type MFC continued to decline,which further inhibited the anaerobic electrode ammonia-nitrogen oxidation performance of MFC.However,due to the further increase in the abundance of Geobacter,The maximum output voltage and maximum output power density are increased to 749.24m V and 23389.75m V/m².During the test,nitrosomonas was always the main denitrification microorganism in the Electro Ammox type MFC system,and the improvement of the abundance of geobacteria promoted the power output of the battery.