Study On The Deep Removal Of Carbon Nitrogen Regulation And Microbial Characteristics Of Wastewater Based On Anaerobic Ammonia Oxidation Process

With the constant demand for“energy saving,standard upgrading and process optimization”of wastewater treatment,it is necessary to promote the new denitrification process in practical application.Among them,a series of combined denitrification processes with high efficiency and low energy consumption based on anaerobic ammonium oxidation?Anammox?have appeared.The process has attracted much attention,but the technology is not yet mature.Some major obstacles has restricted its development.Firstly,partial nitrosation reaction is difficult to maintain a certain effluent matrix ratio at ambient temperature for a long time,and the control means lack flexibility and simplicity.Secondly,Anammox reactions are susceptible to organic stress and the combined process was difficult to coordinate,and the total nitrogen was difficult to be deeply removed.In this study,the operation of the joint process was impletemented through the perspective of real-time control.Also,the best performance of the whole process for simultaneous deep denitrification and decarbonization was found and its microbial mechanism was studied.Based on the ectopic fate mechanism of denitrifying bacteria and Anammox bacteria in ABR,partial nitrosation was set in SBR to make the effluent meet the optimum matrix ratio required for the subsequent reaction and combined with the characteristics of differentiated biological facies in diverse compartments of ABR,a joint process of“partial nitrosation-Anammox-denitrification”was constructed to achieve the goal of simultaneous nitrogen and carbon removal.?1?The SBR reactor was used to establish a strategy of stabilizing partial nitrification by controlling the stopping point of aeration through a specific pH final value.The whole operation process was divided into 4 phases,which were phase I starting nitrosation,phase II exploring the setting rule of the pH final value while stabilizing the nitrosation and phase III,?adopting the setting rule of pH final value to achieve stable partial nitrification.Through 198 days of operation spanning summer,winter and summer?35?7?30??,the rule of organic matter and nitrogen transformation in the SBR system were investigated and the effects of different temperatures on partial nitrosation were also analyzed.The results showed that under low DO concentratin(0.2⁰.4 mg·L^-1)and MLSS of 4000 mg·L^-1,by controlling the pH final value from 7.71 to 7.99 ensuring the effluent FA reached 0.5².0 mg·L^-1,the NO₂^--N/NH₄⁺-N value of the effluent was achieved from 1 to 1.4 during stabilizing partial nitrification,also the accumulation rate of nitrosation?NAR?and the removal rate of organic matter were maintained above 80%and 60%,respectively.Meanwhile,the specific ammonia oxidation rate?SAOR?,nitrite oxidation rate?SNOR?and organic matter removal rate were stabilized at 0.074?0.005 mgN·?mgMLSS?·d^-11 and0.076 mgCOD·?mgMLSS·d?^-11 after achieving the partial nitrosation,respectively.Pre-stable partial nitrosation provided a good guarantee for subsequent matching of Anammox.?2?In order to achieve deep nitrogen and carbon removal in the"partial nitrosation-Anammox and denitrification"chain of SBR-ABR combination process,three different operating conditions were set.Under working condition I,the SBR effluent?NO₂^--N/NH₄⁺-N=1¹.32?was directly connected to the single compartment of ABR with Anammox system.Although the stabilization operation of Anammox reaction was achieved,TN removal rate of the combined process was less than 80%and the effluent TN was about 20 mg·L^-1.In order to increase the denitrification function in the ABR,denitrifying sludge was added to the third compartment of the reactor,and the SBR effluent was connected in the working condition II.It was found that the TN removal rate of the coupling reaction was still low.The realization of deep nitrogen removal needed to replenish the carbon source in the latter stage of Anammox.Therefore,the SBR effluent?NO₂^--N/NH₄⁺-N=5?was mixed with the total reflux water?NO₂^--N/NH₄⁺-N=1.4;C/N=2.5?and then was connected to the single compartment in working condition III.In this condition,not only a good matrix ratio could be achieved of Anammox stage,but also it provided denitrification with good carbon source.As a result,the effluent COD was about 50 mg·L^-1,the effluent TN was less than 6 mg·L^-1,and the TN removal rate was 95%.The stable operation of the combined reaction provided the basis for deep nitrogen and carbon removal in the SBR-ABR process.?3?High-throughput sequencing was used to analyze the dynamic changes of microbial community in SBR-ABR under different environmental and working conditions.The study found that the nitrosation system in SBR was dominated by Proteobacteria and Bacteroidetes,which were accounting for 21.43⁵4.66%and5.11⁵4.78%,respectively.It was worth mentioning that only one kind of Nitrosomonas was detected during the whole period of regulation.The relative abundance of Nitrosomonas at different temperature levels was 1.05⁴1.08%and was more volatile,indicating that the temperature had a great influence on Nitrosomonas.When the ambient temperature was reduced from 10¹5?to 7?,the abundance of the genus suddenly dropped to 4.46%,and the abundance was still at a low level?3.67⁶.36%?after the temperature rose.This phenomenon indicated that temperature had a great influence on functional microbial abundance.However,the average SAOR was maintained at 0.074 mgN·?mgMLSS·d?^-1,and the NAR was stable above80%,indicating that the bacteria was still very active.After the nitrosation was started,the genus Nitrifying bacteria didn't have been detected in the system,which was the main reason for achieving stable partial nitrosation for a long time.Anammox and denitrification coupling system in ABR was dominated by the Chloroflexi,Proteobacteria and Planctomycetes,which were 34.84%,12.67%and 8.77%,respectively.Among them,the Planctomycetes of the Anammox bacteria were focused on Candidatus Brocadia and Candidatus Kuenenia whose relative abundance were 4.91%and 2.64%,respectively.The denitrifying bacteria was focused on Limnobateria with the relative abundance of 4.78%.Anammox bacteria and denitrifying bacteria completed the nitrogen removal of the coupling system together.Also,the heterotrophic bacteria mainly belonging to the genus Anaerolineaceae with the relative abundance of 26.64%together with denitrifying bacteria completed organic matter removal of the coupling system.All of the microorganisms mentioned above cooperated with each other.