Nitrogen Removal Characteristics And Microbial Diversity Analysis Of Denitrifying Microorganisms In High Nitrogen Wastewater

Solving nitrogen pollution in water has always been an important research topic in the environmental area.Biological nitrogen removal technology has the advantage of efficiently removing nitrogen from water while being low-cost and free of cross-contamination.Based on the consideration of biological nitrogen removal technology,This paper enriched microbiota capable of treating highly nitrogen-polluted wastewater,and isolated a strain,Pseudomonas sp.Y-5,which has heterotrophic nitrification and aerobic denitrification capabilities.The mixed heterotrophic nitrifying bacteria community obtained from a wastewater treatment plant in Hongan County was able to treat highly nitrogen-polluted wastewater with an initial NH₄⁺-N concentration of 106 mg/L and the NH₄⁺-N removal efficiency of97.56%.After optimizing the NH₄⁺-N concentration,p H,and C/N of the medium,we found that the NH₄⁺-N removal efficiency was obtained of 99.18%at an initial NH₄⁺-N concentration of 106 mg/L,p H value of 8,and C/N value of 10,using sodium acetate as the carbon source.The anaerobic denitrifying bacteria community obtained from a sewage treatment plant in Wuhan,that can treat nitrogen-containing wastewater with an initial NO₃^--N concentration of 278.23 mg/L,the NO₃^--N removal efficiency was as high as 99%,and the TN removed 282.65 mg/L.High-throughput sequencing showed that the species richness and diversity were significantly reduced.Proteobacteria phylum was the highest proportion（96.56%）.At the same time,aerobic denitrifying bacteria community was enriched from a sewage treatment plant in Wuhan,the removal efficiencies of NO₃^--N and TN were stable at 83.82%and 83.92%respectively,and there was no accumulation of nitrite.High-throughput sequencing revealed differences in Alpha diversity levels between the two samples.The abundance of Proteobacteria phylum increased from 40.9%to 76.24%,becoming an absolutely dominant species.Simultaneous nitrification and denitrification（SND）bacteria community was obtained from a sewage treatment plant in Wuhan,which can efficiently treat high-concentration nitrogen-containing wastewater.When（NH₄）₂SO₄was used as a single nitrogen source,NH₄⁺-N could be basically removed within 24 h,with an average removal rate of 3.75 mg/L/h.Nitrate and nitrite were not detected during the process,and the TN removal efficiency was 96.54%.High-throughput sequencing shows that Proteobacteria and Bacteroidota the major filers of the SND bacterial community.q PCR chip detection showed that the SND bacterial community expressed nitrogen cycle-related functional genes amo B,hao,nar G,nir S,nir K,and nos Z.Combined with the analysis of its ability to degrade different nitrogen sources,it was speculated that the path of SND bacteria community to remove NH₄⁺-N wastewater was to use hao gene to oxidize hydroxylamine to nitric oxide instead of nitrite.Subsequently,a strain was screened and isolated with heterotrophic nitrification-aerobic denitrification ability,which was named Pseudomonas sp.Y-5 after identification.Y-5 could quickly remove high concentration of inorganic nitrogen without accumulating nitrate or nitrite.When NH₄⁺-N was used as the sole nitrogen source,the average removal rate was 4.30 mg/L/h in 24 h;under aerobic conditions,when NO₃^--N or NO₂^--N was used as the sole nitrogen source,the removal efficiency was as high as 99.34%and 95.81%in 24 h,respectively.In addition,it has good adaptability and removal potential for high concentrations of ammonia nitrogen（～401.68 mg NH₄⁺-N/L）and organic nitrogen（～315.12 mg TN/L）.Experiments using mixed nitrogen sources confirmed that the coexistence of high concentrations of nitrate or nitrite with ammonia did not inhibit the nitrification ability of Y-5,allowing 97.80%and 96.29%removal of NH₄⁺-N respectively,and almost complete removal of nitrate and nitrite.