Stability Of Anammox Microbial Fuel Celland Its Denitrification Produnction Mechanism

Anaerobic Ammonia Oxidation（Anammox）has become a research hotspot in the field of wastewater biological denitrification due to its low consumption and high efficiency.However,Anaerobic Ammonia Oxidation Bacteria（AnAOB）are autotrophic microorganisms,and their sensitivity to environmental conditions limits the application of Anammox technology in wastewater treatment processes.Coupling the Anammox denitrification process with microbial fuel cell（MFC）technology,MFC can be used to generate an electric field to enhance the activity of AnAOB,achieving energy saving and consumption reduction and sustainable development.The thesis mainly studies the effects of matrix concentration,addition of external carbon and temperature on the operating efficiency of the ANAMMOX-MFC coupling system,and discusses the mechanism of the coupling system for denitrification production.The specific research results are as follows:（1）The influence of substrate concentration on the performance of coupling system for nitrogen removal and electricity generation.As the influent matrix NH₄⁺-N and NO₂^--N concentrations gradually increase from 50 mg·L^-1and 66 mg·L^-1to 150mg·L^-1and 187.5 mg·L^-1,respectively,the total nitrogen removal load of the ANAMMOX-MFC coupling system increased from 229.68 mg N·L^-1·d^-1to 573.75mg N·L^-1·d^-1,and the nitrogen removal rate first increased and then decreased.The maximum output voltage and power density of the coupling system are 50 m V and7.5 m W·m^-3,the capacitance first increases and then decreases,and the internal resistance first decreases and then increases.With the increase of substrate concentration,the diversity of microorganisms decreased,and the microorganisms Candidatus Brocadia and Candidatus Jettenia with anammox function were further enriched.Among them,Candidatus Brocadia was the main functional microorganism.（2）The subsequent carbon source will improve the performance and stability of the ANAMMOX-MFC coupling system for nitrogen removal and electricity generation.The ANAMMOX-MFC coupling system adds sodium acetate(80 mg·L^-1)and can operate stably for about 60 days in a closed circuit.The subsequent increase in the concentration of NH₄⁺-N in the effluent from hydrolysis and acidification of sludge leads to poor total nitrogen removal.The nitrogen removal rate can still be maintained at about 90%,and the denitrification effect will quickly recover after the addition of sodium acetate is stopped.The NH₄⁺-N concentration in the effluent of the ANAMMOX-MFC coupling system can be used as a"signal"for system imbalance.Stop adding sodium acetate carbon source as a recovery measure,and the increase in effluent NO₃^--N concentration can be used as a"signal"to add carbon source again,which is beneficial to adjust ANAMMOX-MFC coupling system operates more well and stably.（3）The influence of temperature changes on the operating efficiency of the ANAMMOX-MFC coupling system.The operating temperature of the ANAMMOX-MFC coupling system is gradually reduced from 30°C to 15°C.The denitrification performance of the system is reduced,and the total nitrogen removal load is reduced from 0.441 kg N·m^-3·d^-1to 0.325 kg N·m^-3·d^-1,The nitrogen removal rate is reduced by 66.7%.Cooling has little effect on the electricity generation capacity of the ANAMMOX-MFC coupling system.At 15°C,the microbial activity decreases,the electron transfer rate decreases,and the internal resistance of the system decreases.The relative abundance of anammox bacteria Candidatus Brocadia and Candidatus Jettenia both decreased significantly,and the copy number of the functional gene hzsB increased.COG and KEGG analysis showed that the COG functional genes involved in transcription and translation at 15°C,inorganic ions,lipids,amino acid transport and catabolism,etc.were significantly higher than 30°C,and the nucleoside diphosphate reductase and acetyl transfer on the anode biofilm The relative abundance of KEGG functional enzymes such as enzymes,peroxidase and ATP hydrolase accounted for about 87%,which was significantly higher than30°C.（4）ANAMMOX-MFC coupling system denitrification production motor physical analysis.The anode biofilm in the ANAMMOX-MFC coupling system plays a major role in both denitrification and electricity generation.The denitrification effect of the ANAMMOX-MFC system in the electrically coupled state of the closed circuit is significantly higher than that of the open circuit,indicating that the closed circuit has an enhanced effect on the denitrification of the coupled system;however,the relative abundance of the anammox bacteria Candidatus Brocadia and Candidatus Jettenia in the open circuit and the copy number of the functional gene hzsB is greater than the closed-circuit state.The ¹⁵N isotope labeling experiment proved that about 70%of the NH₄⁺-N in the ANAMMOX-MFC coupling system is removed through the anaerobic ammonia oxidation process,and about 25%of the NH₄⁺-N is removed through the electrochemical conversion process.This paper is the simultaneous denitrification and electricity generation of the coupled system the practical application of the mechanism and long-term stable operation provides theoretical support.