Study On The Microbial Characteristics And Performance Of Co-Existence Of Anammox And Denitrification For Simultaneous Nitrogen And Carbon Removal In ABR

Co-existence of Anammox and denitrification for simultaneous removal nitrogen and carbon not only improve Anammox process removal efficiency of total nitrogen but also remove organic matter.Therefore,it provides new idea for low C / N ratio wastewater treatment.However,the optimal environmental conditions exist differences between denitrifying bacteria with anammox organisms.Nevertheless,Anaerobic Baffled Reactor（ABR）has unique microorganisms distribution characteristic which is beneficial to construct suitable environmental conditions for denitrifying bacteria and anammox bacteria,respectively.Consequently,which could form the dominant areas what are beneficial to weak the inhibition on anammox bacteria by organic matter.Accordingly,the objectives of this study are: 1)the optimal conditions for co-existence of Anammox and denitrification system in ABR;2)the cooperative system recovery performance of simultaneous removal nitrogen and carbon under the suppression and microbial communities;3)the cooperative system tolerance to substrate.The investigated objectives are as follows: 1)the influence of influent COD concentration on the performance of co-existence of Anammox and denitrification for simultaneous nitrogen and carbon removal;2)the impact of substrate composition（nitrite and ammonium）on the recovery performance of cooperative system for simultaneous nitrogen and carbon removal.Moreover,the sludge of optimal operate condition and initial one was analyzed by high throughput sequencing;3)the effect of influent substrate on cooperative system and the tolerance to substrate of cooperative system by process kinetics.The main conclusions of the study are as follows:（1）In order to define the process of removal nitrogen and organic matters by coordinating Anammox and denitrification,study on the effect of COD concentrations on the performance of nitrogen and carbon removal in ABR by controlling the influent ammonia and nitrite concentration at 75 mg·L^-1,110 mg·L^-1,respectively.The results showed that the different areas of ABR formed functional areas dominated by nitrite-dependend denitrification,anaerobic ammonium oxidation,nitrate-dependend denitrification,respectively;The 98% and 79% removal efficiency of TN and COD was observed in the lower influent COD concentrations(<120 mg·L^-1).However,the 70% and 92% removal efficiency of TN and COD was obtained in the higher influent COD concentrations(>120 mg·L^-1)due to the enhancement of heterotrophic denitrification and the attenuation of Anammox;Meanwhile,with the increasing of influent COD concentration,the nitrogen removal contribution of Anammox was decreased gradually and that of denitrification increased gradually.（2）In order to solve the poor nitrogen removal efficiency of cooperative systems under the circumstance of influent COD was 180 mg·L^-1,it was adopted by controlled the effluent COD and the total nitrogen（NO₂^--N + NH₄⁺-N）as constant 180 mg·L^-1,respectively,and increased the concentration of NO₂^--N and correspondly decreased the concentration of NH₄⁺-N.The results indicated that the contribution to the TN removal of denitrification decreased at first and then increased,and the contribution of Anammox increased at first and then decreased.It was the optimal condition that the influent substrate concentration of NO₂^--N and NH₄⁺-N was 140 mg·L^-1,40 mg·L^-1,respectively,based on the contribution rate and removal amount of TN in the cooperative system.In optimal conditions,the removal efficiency of TN,NO₂^--N,COD,NH₄⁺-N was 99.7%,99.9%,99.2%,99.7%,respectively.The contribution to TN removal by denitrification was 63.1% and by Anammox was 36.1%.The influent COD was removed by denitrification.For clearer about the relationship between wastewater treatment efficiency with the microbial communities in ABR.High throughput sequencing was adopted to analyze the sludge samples of the optimal operating condition and the initial one.The results showed that nitrogen removal bacteria were co-existence in ABR each compartment,such as Proteobacteria which are mainly distributed in the chamber 1 and 5 of ABR and planctomycetes which are mainly distributed in the middle compartment（2,3,4）of the ABR;The optimal operating conditions（stage IV）than the initial one（phase I）was lower abundance of Proteobacteria（9.46% 22%,22.81% 59.76%,respectively）and higher abundance of planctomycetes（6.59% 14.86%,2.63 3.49%,respectively）;In addition,there were four dominant genus in the phylum Proteobacteria: Hyphomicrobium,Methyloversatilis,Denitratisoma and Limnobacter.Furthermore,Candidatus Brocadia and Candidatus Kuenenia were the main genus in the phylum Planctomycete.At the same time,all of biodiversity index（Chao,ACE,Shannon and Simpson）showed that the microbial species in the B area of ABR under the optimal conditions was lower in complexity and higher in enrichment degree,which indicated some species gradually enrichment.High throughput sequencing results was consisted with the effect of water quality treatment.（3）In order to identify the cooperative system tolerance on the substrate,the concentration of COD,NO₂^--N and NH₄⁺-N was controlled as a constant ratio to increase according to the previous researchs.The results showed that the removal efficiency of COD,NO₂^--N,NH₄⁺-N and TN was above 93%,94.4%,93.2% and 93%,respectively when the influent substrate concentration（COD,NO₂^--N,NH₄⁺-N）<（420,270,110）mg·L^-1.With the influent substrate concentration increased,the contribution to TN removal amount of Anammox was decreased（43.08%,39.02%）and of denitrification was increased（53.81%,57.14%）.While the contribution of Anammox or denitrification sharply decreased or increased to 16.49%,82.07%,respectively,when the influent substrate concentration up to（420,270 and110）mg·L^-1.Anammox bacteria in B area of ABR was inhibited by FA according to analyze the potential inhibition sources.Process kinetics indicated that the Stover-Kincannon model（R²=0.937,TN;R² = 0.975,COD）turned out to be appropriate to describe the tolerance to substrates of the cooperative system,rather than First-order substrate removal model（R²=0.314,TN;R²=0.016,COD）.The maximum substrate utilization rate obtained by Stover-Kincannon model of TN and COD was 1.43 g·L^-1·d^-1 and 3.33 g·L^-1·d^-1,respectively and the saturation constant was 1.2 and 3.79,respectively.Therefore,the cooperative system theoretically continues to enhance the influent substrate concentration relative to the current influent substrate.