| The Microbial Fuel Cell is an innovative and sustainable wastewater treatment technology for pollution control and energy production.In order to solve the problem of self-feedback inhibition for pH,difficulty in enrichment of cathodic denitrifying bacteria in the presence of aeration and secondary pollution caused by phosphate buffer system in traditional microbial fuel cell.In this paper,the start-up process and optimal working conditions of cathode nitrification coupled to anode denitrification of MFC were studied by constructing self-buffering system.Cathode nitrification coupled to anode denitrification of MFC took 45d to start,the stable voltage was 560 mV,and the maximum power density was 6.71 W·m-3.In the start-up stage,the total nitrogen removal rate of the system increased with the time,and finally the total nitrogen removal rate was close to 99%.COD removal rate of anode chamber was 92.7%.After the successful start of the reactor,the SEM on the graphite particles of anode chamber were mainly rod-shaped bacteria,which were densely distributed and closely connected with each other,and the SEM on the graphite particles of cathode chamber were sparse.The main bacteria in the anode chamber were Shewanella,Geobacter,Pseudomonaceae and Denitratisoma.The main bacteria in the cathode chamber were Nitrospira and Nitrobacter.The factors affecting the performance of cathode nitrification coupled to anode denitrification of MFC were explored.The operating conditions were optimized,and the following conclusions were obtained:?1?The smaller external resistance,the faster of degradation rate of organic matter,the higher of total nitrogen removal rate,the stronger of oxidation capacity on the anode chamber.?2?In the certain range,with the increase of COD concentration in the anode chamber,the better of power production performance in MFC,the higher of maximum power density,but the lower of coulombic efficiency in the anode chamber.The COD concentration in anode chamber had little effect on denitrification and carbon removal of MFC.?3?In the certain range,with the increase ammonia concentration?NH4+-N?in the cathode chamber,the better of power production performance in MFC,the higher of maximum power density,the decreased of total nitrogen removal.The concentration of ammonia concentration?NH4+-N?in cathode has little effect on the carbon removal effect of MFC.?4?The maximum power density increased then decreased with the increase of the hydraulic residence time,and the hydraulic residence time had little effect on denitrification and carbon removal of MFC.?5?The production performance of MFC increased then decreased with the increase of stirring strength.When recirculation was 20 mL·min-1,the maximum power density was 7.01 W·m-33 NC,the reactor was between the complete mixed flow and the push flow,the system of denitrification and carbon removal effect was the best.The optimal woriking conditions of cathode nitrification coupled to anode denitrification of MFC were external resistance of 100?,anode chamber COD concentration of 550mg·L-1,cathode chamber ammonia concentration?NH4+-N?of 25 mg·L-1,system hydraulic residence time of 8.2 h and recirulation of 20 mL·min-1.The maximum power density was7.05 W·m-3 NC in MFC under the optimal conditions,the average daily total nitrogen removal rate was 98.32%,and the average daily COD removal rate was 93.05%.Under the optimal conditions,the SEM on the graphite particles of anode chamber were mainly rod-shaped bacteria,which were close to the biological larvae and the SEM on the graphite particles in the cathode chamber were connected with each other.The main bacteria in the anode chamber were Geobacter,Shewanella,Denitratisoma,unclassifiedfRhodocyclaceae and Pseudomonaceae.The main bacteria in the cathode chamber were Nitrospira and Nitrobacter.The bacteria genera of the anode and cathode chambers were similar to those of the anode and cathode chambers at the start-up stage,but the proportions were different. |
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