Study On The Removal Of High Concentration Nitrate In Wastewater By Electrocatalytic Synergistic Anaerobic Ammonium Oxidation Reactio

With the increasing attention to environmental pollution problems and the continuous improvement of wastewater discharge standards,the traditional biological nitrous removal processes are difficult to remove high concentrations of nitrate from the wastewater.Therefore,the transformation of the biological sewage treatment process has become a hotspot of current research.Anaerobic ammonia oxidation（Anammox）process has become recognized as the optimal biological nitrogen removal method due to the advantages of low energy consumption,low sludge yield,and without additional organic carbon source.At present,the biggest problem facing the anaerobic ammonia oxidation process in the removal process of high-concentration nitrate wastewater is how to efficiently convert the nitrate-nitrogen（NO₃^--N）in the wastewater into a specific concentration ratio of ammonia nitrogen（NH₄⁺-N）and nitrite-nitrogen（NO₂^--N）,which is also the main problem solved in this paper.Among them,the electrochemical method enters the field of vision of researchers as a green and efficient reduction method.Electrochemical methods mainly load materials with specific catalytic activity on the cathode and select appropriate experimental parameters to achieve the purpose of rapid nitrate conversion.Therefore,this paper proposes the use of electrocatalytic synergic anaerobic ammonia oxidation reaction to achieve low energy consumption,efficient nitrogen reduction,and ultra-depth treatment emissions.Using foam copper as the substrate,the surface is electrochemical and optimized to have the catalytic capability of controllable and efficient reduction of a specific proportion of NH₄⁺-N and NO₂^--N.Master the relationship between electrode material structure and catalytic properties,obtain low-cost and high-efficiency electrode materials,and master the electrode catalytic performance parameters.After that,electrocatalytic reduction using anaerobic ammonia oxidation technology to synthesize a specific proportion of NH₄⁺-N and NO₂^--N for deep nitrogen removal treatment.The initiation and reaction processes of anaerobic ammonia oxidation bacteria are mastered to achieve zero-carbon source self-trophic and nitrogen removal.The method has significant economic and environmental advantages over traditional denitrification techniques of additive organic carbon sources,short-range denitrification,and anaerobic ammonia oxidation techniques,providing a viable strategy for removing highly concentrated nitrate in wastewater.The main research contents of this paper are divided into the following three parts:1.Study of the CuAg alloy catalyst for electrocatalytic reduction of NO₃^--N to specific proportions of NH₄⁺-N and NO₂^--N.First,different proportions of CuAg alloy catalyst were prepared by electrodeposition method,and best reaction Cu:Ag ratio catalyst was Cu₁₁Ag₃.It was found that the concentration ratio of NH₄⁺-N and NO₂^--N was about 1:1 at 0.5 h at-0.33 V vs.RHE,1 M KOH,and 200 mg/L KNO₃,when the nitrate reduction rate reached 96.68%,meeting the requirements of the anaerobic ammonia oxidation reaction.Then,after multiple consecutive electrocatalytic nitrate reduction cycle tests,the Cu₁₁Ag₃ catalyst still maintained the high conversion rate and the Faradic efficiency, demonstrating the good stability of the Cu₁₁Ag₃ catalyst.Finally,combined with the data of characterization,kinetic test,and theoretical calculation,the reduction mechanism of the Cu₁₁Ag₃ catalyst for efficient catalysis of nitrate was explored.2.Study on the characteristics of beech charcoal mediated anaerobic ammonia oxidation bacteria.Adding beech charcoal can not only improve the activity of anaerobic ammonia oxidizing bacteria,make it grow faster and better,but also increase the secretion of Extracellular polymeric substances（EPS）and promote its aggregation to form flocculation or particles.So anaerobic ammonia oxidizing bacteria have better settlement performance and improve their retention capacity.Moreover,the start time of beech charcoal mediated anaerobic ammonia oxidation reaction（38 d）is 17 d shorter than the start time of no beech charcoal mediated anaerobic ammonia oxidation reaction（55 d）, greatly shortening the initiation process of anaerobic ammonia oxidation reaction,and making the anaerobic ammonia oxidation reaction more efficient.3.Electrocatalytic nitrate reduction technology and anaerobic ammonia oxidation technology cooperate to remove the high concentration of nitrate in the wastewater.The Cu₁₁Ag₃ catalyst reduced 200 mg/L NO₃^--N to specific proportions of NH₄⁺-N and NO₂^-- N（concentrations of 91.6 mg/L and 95.6 mg/L,respectively）,and then transferred to the anaerobic oxidation pool for anaerobic ammonia oxidation.The total nitrogen（TN） removal rate throughout the reaction was slightly（87.63%）than in the beech charcoal mediated anaerobic ammonia oxidation reaction（82.48%）.Meanwhile,the TN removal rate meets the national required emission standards.