Study On Removal Performance And Mechanism Of Anaerobic Ammonia Oxidation System Using HCO₃^-/NH₄⁺-N As Substrate

As a new biological nitrogen removal method,anaerobic ammox technology has been widely studied and concerned in the field of water pollution control.The classical anaerobic ammox reaction uses nitrite nitrogen as electron acceptor and ammonia nitrogen as electron donor to complete the nitrogen removal process.Anaerobic ammox bacteria have a variety of electron acceptors,which can use sulfate,ferric salt,manganese salt as electron acceptors to complete the process of nitrogen removal.The research group established the HCO₃^-/NH₄⁺-N anaerobic ammoxidation system in the early stage,and the preliminary results showed that the system also had good ammonia conversion and total nitrogen removal performance without additional electron acceptor.However,the mechanism of ammonia conversion and total nitrogen removal in the system was not clear at present.In view of this,on the basis of the previous research group,this thesis built HCO₃^-/NH₄⁺-N anaerobic ammoxidation reactor,used simulated wastewater,investigated the denitrification performance of the reactor in long-term operation,combined with the identification of ammoxidation substances and ammonia oxidation rate test,microbial community structure analysis and quantitative analysis of ammoxidation microorganisms,etc.Explore the ammonia conversion and nitrogen removal mechanism of the system.The main research conclusions are as follows:（1）The long-term operation test of HCO₃^-/NH₄⁺-N anaerobic ammox reactor found that the HCO₃^-/NH₄⁺-N anaerobic ammox reaction system can be successfully started by gradient reduction of NO₂^-concentration.In the two stages of reactor operation,in stage I,the concentration of NH₄⁺-N was controlled at 200 mg/L and the concentration of NO₂^--N was 264 mg/L,200 mg/L,150 mg/L,100 mg/L and 0 mg/L respectively.The removal efficiency of NH₄⁺-N were 99.34%,67.33%,45.15%and34.27%,respectively.At this time,Rs and Rp were 1.36,1.63,1.69,1.80 and 0.15,0.31,0.42,0.55,respectively,which gradually deviated from the theoretical values,indicating that there was a non-traditional anaerobic ammox reaction in the system.When NO₂^-concentration was 0 mg/L and NH₄⁺-N concentration was 150 mg/L,100mg/L and 50 mg/L,the removal rate of NH₄⁺-N was 12.93%,23.96%and 41.33%,respectively.However,the average daily removal amounts of NH₄⁺-N were 413.76mg/d,548.64 mg/d and 516.24 mg/d,respectively.The decrease of NH₄⁺-N concentration was beneficial to improve the removal efficiency of NH₄⁺-N,but has no great influence on the daily removal amount.（2）High-throughput sequencing analysis test results show that the microbial diversity in phase I,anaerobic ammonia oxidation bacteria floating mold gate（Planctomycetes）and level of the uncertain status of anaerobic ammonia oxidation bacteria genera unclassified＿f＿Brocadiaceae abundance gradually decline,Gradually losing its dominant genus status.The increasing abundance of denitrifiers at Denitratisoma and Limnobacter led to the transition from the traditional anaerobic ammox reaction to the non-traditional one.（3）The results of fluorescence quantitative ammoxidation microbial quantity test showed that the number of ammoxidation archaea and ammoxidation bacteria fluctuated steadily in stage II after NO₂^-concentration gradient decreased in stage I,and the number range was 8.958×10⁶-1.767×10⁷ and 6.34×10⁷-9.996×10⁷,respectively.Compared with natural environment and artificial sewage treatment system,amo A gene quantity of ammonia-oxidizing archaea and ammonia-oxidizing bacteria in stage II reactor was relatively high.This provides a microbial basis for the conversion of ammonia in HCO₃^-/NH₄⁺-N anaerobic ammoxidation reaction system.（4）AOA and AOB general and specific inhibitor tests showed that after AOA activity was inhibited by 150 umol/L high concentration PTIO inhibitor,the conversion of ammonia nitrogen in the reaction system stopped,while after AOB activity was inhibited by 20 mg/L low concentration sulfate streptomycin,the conversion rate of ammonia nitrogen in the reaction system was still reduced,but compared with the control group.This proves that the key to ammonia conversion in HCO₃^-/NH₄⁺-N anaerobic ammox reactor without adding exogenous electron acceptors is the metabolic activity of AOA.The results of ammoxidation substance identification test showed that the concentration of dissolved oxygen in the reaction system increased after AOB activity was inhibited by 20 mg/L low concentration of streptomycin sulfate.While AOA activity was inhibited by 150 umol/L PTIO inhibitor,the concentration of dissolved oxygen in the reaction system did not increase.This proves that AOA metabolism produces oxygen as an electron acceptor for ammoxidation.（5）The analysis of denitrification mechanism in the HCO₃^-/NH₄⁺-N anaerobic ammox reaction system shows that AOA produces dissolved oxygen in the reactor,and the generated dissolved oxygen acts as an electron acceptor to oxidize NH4+to generate NO₂^-,and then the generated NO₂^-is used by anaerobic ammox bacteria and denitrification for anaerobic ammox reaction and denitrification reaction.