Nitrogen Removal Performance And Microbiota Of Vertical Subsurface Flow Constructed Wetland Under Oxygen Control

According to the regional characteristics of rural areas in Anhui Province,the effects of three kinds of fillers,four kinds of wetland inlet saturation zone depth and different numbers of aeration pipes on the reoxygenation performance of vertical subsurface flow constructed wetland system were studied.At the same time,the effects on the purification performance,especially the nitrogen removal performance,and the microbial community structure characteristics were investigated,so as to explore the effective measures to effectively improve the reoxygenation performance and purification effect of vertical subsurface flow constructed wetland.The main research contents and results are as follows:（1）Among the three fillers of vertical subsurface flow constructed wetlands,wetland A with zeolite as substrate was superior to wetland B with volcanic rock as substrate and wetland C with ceramsite as substrate in nitrogen and phosphorus removal and organic matter decomposition.Zeolite is better than the other two fillers in improving the capacity of wetland reoxygenation.The main dominant phyla of microorganisms in the three wetlands were Proteobacteria,Actinobacteria,Patescibacteria,Firmicutes,Bacteroidota,Chloroflexi,Desulfobacterota,Acidobacteriota,Deinococcota.The measurement results of wetland A in different time periods were compared,Proteobacteria and Actinobacteria were dominant in wetland A,the relative abundance reached 53.14%and 29.56%;Comparison of three wetlands,the relative abundance of Proteobacteria in wetland A is the highest,which plays a major role in the removal of nitrogen and phosphorus pollutants.（2）In the unipolar vertical subsurface flow constructed wetland with different saturation zone depths,when the saturation zone depth is 45 cm,the completely autotrophic nitrogen-removal over nitrite is most effectively enhanced due to the significant enhancement of anammox.Therefore,the vertical subsurface flow constructed wetland with corresponding depth has the best removal effect on total nitrogen,and the N₂O emission is low at this time.It can be concluded that completely autotrophic nitrogen-removal over nitrite can be the main way of total nitrogen removal in vertical subsurface flow constructed wetland by nitrite autotrophic nitrogen removal process,and the suitable saturation zone depth（45cm）can improve the reoxygenation capacity of vertical subsurface flow constructed wetland and optimize the wetland microenvironment.（3）In the vertical subsurface flow constructed wetland system with different number of draught pipes,when the number of aeration pipes is 6(and the hydraulic load is about 0.13 m³·（m²·d）^-1,the nitrite activity and anammox specific activity of the system are high,so the completely autotrophic nitrogen-removal over nitrite in the wetland system can be greatly enhanced,and the wetland has strong reoxygenation performance,Therefore,the total nitrogen removal effect of wetland system is the best.