Effect Of Iron-rich Media On Nitrogen Removal Performance Of Anaerobic Ammonia Oxidation And Denitrification Coupling Reactor

In order to improve the nitrogen removal efficiency,the traditional biological denitrification technology needs to add carbon source,which will produce a large amount of sludge and cause environmental pollution.Anaerobic ammonium oxidation technology has high nitrogen removal performance,and the anammox bacteria is autotrophic bacterium,its sludge yield is low and no additional carbon source is needed,However,the anammox bacteria are easily affected by the external environment.In view of the fact that metal ions can increase the number of microbial community and improve the denitrification efficiency of the reactor,a new comprehensive denitrification system of physicochemical and biochemical processes was formed by connecting the iron-rich packed column with the Anammox teactor in series to carry out the advanced wastewater treatment.In this experiment,the characteristics of iron-rich packed column were studied,and the effects of ammonia nitrogen and organic matter inhibition on the denitrification performance and microbial diversity of an Anammox biofilm reactor were studied respectively.Finally,the iron-rich packing column and the Anammox reactor were operated in series to achieve high efficiency and advanced nitrogen removal.The iron-rich filler has a certain removal effect on the dissolved oxygen in water.When the influent DO concentration is below 4.00 mg/L,the dissolved oxygen concentration is about 2.5 mg/L when the packing layer height is 90 cm.The concentration of dissolved oxygen is controlled at about 3～4 mg/L in subsequent tests.The TFe and Fe³⁺released by the iron-rich packing will increase with the increase of the packing height of the iron-rich packing column.The maximum concentration of Fe²⁺is reached at the height of 90 cm.The removal of organic matter in the reactor was promoted by the iron-rich packing column.When the concentration of organic matter was 90 mg/L,the removal rate was up to 6.31%.The biodegradability and p H value in the reactor were increased by iron-rich filler.The removal rates of NH₄⁺-N,NO₂^--N and TN in the Anammox biofilm reactor were99.11%,98.34%and 85.74%,respectively,when the polyurethane porous material was inoculated and enriched to 108d.The effects of different organic concentration and high ammonia concentration on the denitrification performance of the Anammox reactor were investigated.When the organic concentration was increased to 30 and 60 mg/L,the removal rates of NH₄⁺-N and NO₂^--N in the reactor were reduced but both were higher than 98%.When the organic concentration was continuously increased to 90 mg/L,the Anammox process was inhibited.When the ammonia nitrogen concentration increases from 40 mg/L to100 mg/L,the removal rate of NH₄⁺-N decreases from 99.36%to 61.15%,which inhibits the Anammox,and the TN removal rate in the reactor decreases 22.25%.The results show that ammonia nitrogen concentration and high organic matter will inhibit the denitrification performance of the Anammox reactor,which will significantly decrease the denitrification performance of the Anammox reactor.According to high-throughput sequencing analysis of different organic concentration on microbial diversity in Anammox reactor,the number of microbial categories at the concentration of 60mg/L organic matter was higher than other samples.When the concentration of organic matter was 90mg/L,The abundance of Proteobacteria and Bacteroidota was much higher than that of other samples.Analyzing the diversity of microbial communities at the genus level,The results show that:Compared with 6.56%in ANB0＿16,the abundance of Denitratisoma in ANB60＿16 and ANB90＿16 increased by 4.34%and0.07%,respectively.The abundance of Candidatus＿Brocadia at the bottom and 16cm of the reactor with 60mg/L organic matter increased by 8.50%and 5.91%,respectively,compared with that at the bottom and 16cm of the reactor without organic matter,indicating that appropriate organic matter can promote the abundance of Anammox bacteria,while excessive organic matter can reduce the abundance of Anammox bacteria.The number of OTU species in the reactor was reduced when ammonia nitrogen concentration was too high.The abundances of Chloroflexi and Firmicutes in the reactor in reactor changed significantly.In the reactor,the abundance of Planctomycetota was 7.42%at the bottom and increased by 4.21%in the middle due to the influence of ammonia nitrogen concentration.The abundance of SBR1031、Bacillus、OLB14 in the bottom of the reactor was higher than that in the middle.The abundance of Candidatus＿Brocadia and Candidatus＿Jettenia increased in the reactor.The higher ammonia nitrogen concentration at the bottom inhibited the Anammox bacteria.As a result,the abundance of Anammox bacteria in the bottom is low,while the inhibition of ammonia nitrogen on Anammox bacteria in the middle is weakened due to the decrease of ammonia nitrogen concentration,and the abundance of Anammox bacteria is enhanced.When the influent NH₄⁺-N concentration is 100 mg/L,the iron-rich packed column runs in series with the Anammox reactor,and the TN removal rate of the Anammox reactor increases to 80.79%,and the dominant species in the reactor changes from Chloroflexi to Planctomycetota.The abundance of pelagicum in the bottom and middle of the reactor was34.93%and 24.09%,respectively,which increased by 27.51%and 12.46%compared with A＿0 and A＿40,respectively.The results showed that the iron-rich packed column weakened the inhibition effect of ammonia nitrogen concentration on Anammox reactor.