Study On The Nitrogen Removal Performance Of The Coupled-system Of Anammox And Sulfur/pyrite Autotrophic Process

Anaerobic ammo nia oxidat io n（Anammo x）has significant advantages in treating wastewater with low C/N ratio,because of no aeration,no organic carbon source and low sludge yield.However,nitrogen remo val performance under high nitrogen lo ad is st ill the bottleneck of practical applica t ion of anammo x,which was due to the limitat ion of 11%nitrate（total nitrogen）.In this study,a two-stage（the TAS system）process and a one-stage（the OAS system）process were established via coupling anammo x and sulfur/pyrit e autotrophic denitrificat ion,to explore the differences on nitrogen remo val performance between the two systems under high nitrogen load,and further to clarify the internal response mechanism;Effluent reflux strategy was adopted to enhance the nitrogen removal performance of the two systems,and the promotion mechanism of Fe²⁺on anammox was revealed.The main result s are as follows:（1）To explore the differences on nitrogen remo val performance between two systems under high nitrogen load.The results showed that the total nitrogen removal efficiency（TNRE）of TAS system was stable at 93.63±1.87%,while that of OAS system was stable at 97.85±1.92%.The OAS system had lo nger adaptation period and more efficient nitrogen removal performance than TAS system under high nitrogen load.（2）The metabolite characterist ics,electrochemical act ivit y and bacterial communit y structure of the two systems was analyzed,and the potential funct ional response mec hanism under high nitrogen load was revealed.T he results showed that the OAS system could secrete more extracellular polymeric substance（EPS）and lo wer PN/PS ratio.T hus,the microbial aggregates of the OAS system had better aggregation act ivit y,strengt h and stabilit y to effect ively resist the environment of high nitrogen load.The contents of redox substances（such as FMN）and adenosine triphosphate（ATP）were increased,which were contributed to electron transfer and microbial metabolic act ivit y.The r elat ive abundances of funct ional bacteria（such as Candidatus＿Kuenenia,Thiobacillus）were increased,and established a more effect ive microbial structure for efficient nitrogen remo val.Based on the in-depth analysis of mult idimensio nal results,the potential response mechanism of OAS system under high nitrogen load was proposed.（3）The effluent reflux strategy was adopted to enhance the nitrogen removal performance of the two systems under high nitrogen lo ad,and to clarify the promotio n mechanism of Fe²⁺on anammo x process.The results showed that Fe²⁺could promote the PN and PS contents of EPS by 1.18 and1.34 times,respect ively,which could enhance the aggregat ion,stabilit y and sedimentatio n of anammo x granular sludge.Fe²⁺could increase the secret ion of riboflavin and reduce the electron transfer resistance,further to accelerate electron transfer.The Electron transport system act ivit y（ETSA）value and ATP content were also increased to enhance the respiratory metabolic intensit y and activit y of anammo x bacteria,thus realized the rapid degradat ion of nitrogen pollutants.The promotion mechanism of Fe²⁺on anammo x was proposed based on the mult i-dimensio nal response characteristics of microorganisms.To sum up,the OAS system could realize high eff icient nitrogen remo val performance under high nitrogen load.Besides,Fe²⁺could promote anammo x process.The study clarified the potent ial function response mechanism of the coupling system under high nitrogen load and the effect iveness promotion mechanism of Fe²⁺on anammo x process,which will provide a theoretical supporting for practical applicat ion of the coupled-system of anammo x and sulfur autotrophic denitrificat ion in the future.