Characterization And Mechanism Of Goethite-Fulvic Acid In Enhancing The Anammox Process

The innovative nitrogen removal technology-Anammox,which can efficiently remove nitrogen from wastewater without organic carbon consumption and aeration,has attracted increasing attentions in recent years.However,the long generation cycle（about 11-14 d）and sensitivity to environmental conditions of anaerobic ammonium oxidation bacteria（AAOB）limit the efficient and stable operation of Anammox process.Therefore,how to improve the nitrogen removal performance and operation stability of anaerobic ammonium oxidation process has attracted wide attention.In this study,based on the increase of substrate concentration and the optimization of substrate ratio,the anaerobic ammonia oxidation reactor was started.By investigating the denitrification performance,sludge characteristics and microbial community structure of the reactor,the effect and mechanism of goethite-fulvic acid on anaerobic ammonia oxidation process were explored.The main results are as follows:1)Characteristics of Anammox reactor and optimal regulation of substrate ratio during start-up process was investigated.The results showed that by increasing substrate concentration three times and optimizing regulation of substrate ratio once,the NLR reached 2.16 kg-N·（m³·d）^-1,and the nitrogen removal efficiency（NRE）and nitrogen removal rate（NRR）reached 87.60%and 1.89 kg-N·（m³·d）^-1,respectively.The anammox reactor was successfully started up after 90 d.When the influent NO₂^--N concentrations were 330 mg·L^-1,the activity of An AOB was inhibited,which led to the deterioration of the reactor performance.By optimal regulation of Substrate Ratio,the denitrification performance of the calendar reactor is recovered in 5 days.2)Goethite-fulvic acid was prepared and characterized,and the effect of goethite-fulvic acid on the performance of Anammox reactor was investigated.The results showed that goethite-fulvic acid has typical infrared peak of goethite,Fe2p characteristic peak in XPS and XRD characteristic diffraction peak,and has excellent redox characteristics.When the NLR was 2.16 kg-N·（m³·d）^-1,the NRE and NRR of the R_Ge-FA were higher than those of the R_con and R_Ge.The addition of goethite-fulvic acid could enhance the denitrification performance of the anammox reactor.The addition of goethite-fulvic acid could make the particle size distribution of sludge more uniform,enhance the stability of sludge,and improve the activity of An AOB,thereby enhancing the denitrification performance of the reactor.An AOB adsorbed on the surface of goethite-fulvic acid could increase the abundance of Planctomycetes and Candidatus Kuenenia to enhance the denitrification performance of the reactor.3)The effect of goethite-fulvic acid on anaerobic ammonium oxidation denitrification performance was investigated by batch experiments,and the influence mechanism was further explored from the aspects of microbial metabolism and electron transfer.The results showed that 5 mmol·L^-1 goethite-fulvic acid had a enhancing effect on anammox denitrification performance.Goethite-fulvic acid could enhance the performance of anammox denitrification by promoting microbial metabolism and electron transfer.