Study On The Nitrogen Removal Effects And Mechanism By Using Elodea Nuttallii-immobilized Nitrogen Cycling Bacteria Assemblage Technology In Qinshui River,Gonghu Bay

With the rapid development of the social economy,a large number of industrial,agricultural,and urban domestic wastewater which rich nitrogen poured into water environment,resulting in eutrophication of river,serious damage to the surface water environment.In order to solve the problems of river eutrophication,in this thesis,we selected a typical inflow lake river?Qinshui River?,through the establishment of ecological restoration in the laboratory to investigate the nitrogen transformation processes.To analysis the nitrogen assimilation of plants,sediment storage and microbial transformation mechanism,we used portable dissolved oxygen analyer,isotope ratio mass spectrometer and membrane inlet mass spectrometry to study the oxygen erosion depth,nitrogen removal rate with different ways.The microbial abundance of denitrification and anammox and the microbial community diversity of river sediment were analyzed by high throughput technique.The mechanism of nitrogen transformation in plant adsorption,sediment storage and microbial processes were stuided by isotope pairing technique.And we applied immobilized nitrogen cycling bacteria-biological carrier-submerged macrophyte integrated remediation technology in Qinshui River remediation project.The experiment results provided the scientific evidence of the control of river eutrophication,which could be the theoretical basis and technical support for river restoration.Through the study,the main conclusions are as follows:?1?The present of macrophytes enhanced the oxygen penetration depth,the erosion depth has been increased from 14mm to 30mm.Simultaneously,the technology changed the microenvironment in surface water-sediment,create an aerobic-anaerobic environment around the root zone,enhanced the process of microbial nitrification and denitrification,which promoted the removal of nitrogen.?2?According to the results of IPT experiment,by comparison the amount of 15N assimilated by Elodea nuttallii in different ecological restoration treatments,the treatment C?only Elodea nuttallii?had the higher nitrogen absorption rate than treatment D?Elodea nuttallii+INCB?.And much more 15N-NH₄⁺ was assimilated by E.nuttallii,about 2 times as much as 15N-NO₃^-.The enrichment of 15N abundance in E.nuttallii increased observably,indicating that both nitrate and ammonia nitrogen can be ingested remarkably.Aquatic plants play an important role in nitrogen removal from eutrophic river system.?3?Nitrogen released in form of gas?N₂ and N₂O?showed signification different among the four treatments?P<0.05?.The treatments with INCB added?treatments B and D?had higher gas emissions.Compared with the group after adding 15NO₃^-,there was lower accumulation of 15N-labled gas observed in the group with 15NH₄⁺added.The addition of INCB improved the abundance and activity of nitrogen removal microorganism,promote the nitrogen removal process in river system.?4?As the q-PCR analysis showed,add E.nuttallii and INCB had the impact on the denitrification and anammox microbial abundance in river sediment.In the treatment D,the copy numnber of functional genes?nosZ,nirK,nirS and Hzo?were higher than the other three treatments.The results showed that the number of denitrifying bacteria in the surface sediment increased,and nitrogen removal capacity of simulated ecosystem was improved.?5?The 16S rRNA gene high-throughput sequencing technology was used to investigate bacteria community structure.The treatments D had the most abundant microbial community structure,Proteobacteria?46.65%?is still the main category,followed by Bacteroidetes?18.72%?,Acidobacteria?7.03%?,and Nitrospira?5.88%?.The genera related to denitrification were Pseudomonas,Acinetobacter,Aeromonas,Comamonas and Stenotrophomonas.The genus related to anammox was Planctomyces.The diversity of denitrifying bacteria was increased after the addition of E.nuttallii and INCB,which could effectively alleviate the disadvantage of low diversities and activity in river.?6?Through the simulation experiment of ecological restoration,the transformation equilibrium of 15NO3-and 15NH4+ was quantitatively studied.In the four treatments,without considering the nitrogen accumulated in the overlying water,the treatment D had the highest nitrogen removal efficiency,the removal rate of 15NO₃^-was 65.46%,and the 15NH₄⁺ removal rate was 57.74%.The results indicated that E-INCB assemblage technology could significantly promote the nitrogen cycling and improve nitrogen removal efficiency?7?The immobilized nitrogen cycling bacteria-biological carrier-submerged macrophyte integrated remediation technology in Qinshui River remediation project was applied.The long-term monitoring results of water quality inside and outside the demonstration area showed that the purification effect inside of demonstration area was better than the outside.The TN removal rate was 35.37%,NH₄⁺ removal rate was 64.99%,NO₃^-removal rate was 51.55%,NO₂^-removal rate was 32.81%,TP removal rate was 40.72%,COD removal rate was 45.57%.?8?The high-throughput sequencing technology was used to study the bacteria community structure inside and outside of Qinshui River demonstration area.Denitrifying microorganism related were Pseudomonas,Acinetobacter,Comamonas,Azoarcus,Aeromonas and Planctomyces.The use of immobilized nitrogen cycling bacteria-biological carrier-submerged macrophyte integrated remediation technology,increased the microbial diversity in the sediment,and enhanced the abundance of denitrifying microorganisms in the in situ Qinshui River ecosystem.