The Processes Of Nitrogen Removal By Aerobic Denitrifier

The water pollution caused by the accumulation of nitrogen compounds has seriously affected the ecological balance and human health.Therefore,the treatment of nitrogen pollution in water bodies has become an important research hotspot.The nitrogen cycle in water bodies is mainly driven by microorganisms,so biological denitrification is an important way to control nitrogen pollution in water bodies.Aerobic denitrifying bacteria,as a kind of microorganisms that widely exist in natural habitats,are of great significance to the treatment and restoration of polluted water bodies.On the other hand,due to the continuous and effective treatment of organic pollution in the environment,the concentration of organic pollution in polluted and micro-polluted waters has continued to decrease.Therefore,adding exogenous inorganic electron donors to replace organic nutrition is an environmentally friendly and economical way.This research is based on adding exogenous electron donors（synthetic microecosystems）to strengthen the native denitrifying flora in polluted waters to improve the denitrification performance of microorganisms in polluted waters,and to explore this through high-throughput sequencing and real-time quantitative PCR technology.The impact of a process on microorganisms in the ecosystem,with a view to providing practical support for the treatment of low C/N water bodies.An actinomycete with aerobic denitrification ability was selected from the water source reservoir samples,and its ability to remove nitrogen and carbon and nitrogen balance was investigated,and its carbon source metabolism ability was studied,with a view to probing aerobic denitrification.The metabolic capacity of actinomycetes provides a new source of strains for the treatment of micro-polluted water.The main results of this research are as follows:（1）The synthetic micro-ecosystem strengthens the denitrification process of activated sludge and the interaction mechanism of bacteria;The synthetic microecosystem（SM）synergistic activated sludge has a higher nitrate removal efficiency for low C/N wastewater than the control group lacking electron donors by at least 40%.The results of real-time quantitative PCR showed that adding a synthetic microecosystem,the abundance of denitrifying functional genes in the reaction system was significantly increased,and the abundance increased by nearly2.7 times.High-throughput sequencing results showed that the dominant bacteria in the activated sludge samples were all Proteobacteria,and the dominant bacteria were Actinomyces,Proteobacteria,and Chloroflexia;and the dominant bacteria were Rhodobacteraceae,Zoogloeaceae,and Phyllobaceae,Pseudomonas family.Network analysis shows that the denitrifying flora added with synthetic micro-ecosystems has more levels of symbiosis systems,and the interaction between the genus shows more positive effects,and some of the experimental groups added SM have both Functional bacteria for denitrification and inorganic electron transfer（Paracoccus,Thaurea,Achromobacter,Alicycliphilus,Nitrosospira,Ochrobactrum）are in a more advantageous module.（2）Synthetic micro-ecosystems strengthen the denitrification process of reservoir sediments and the interaction mechanism of bacterial communities;The synthetic microecosystem（SM）synergistic water source reservoir sediments have an approximately 60%increase in the denitrification efficiency of low-C/N wastewater compared with the control group lacking electron donors.The water source reservoir sediments added with synthetic micro-ecosystem have a good removal capacity for COD_Mnin low C/N water bodies,with a maximum removal efficiency of87.48%.After SM is added,the denitrifying bacteria in the sediments have a higher removal capacity for COD_Mn.It shows that the denitrifying flora is more active after adding SM.High-throughput sequencing showed that the dominant bacteria phyla in the sediment samples of water source reservoirs were all Proteobacteria.The dominant bacteria families areβ-Proteobacteriaceae,α-Proteobacteriaceae,and Proteobacteriaceae.Symbiosis network analysis shows that after SM is added,the bacteria Pseudomonas,Thiobacillus,Cupriavidus,Thaurea,and Azospirillum are transformed from non-dominant modules to dominant modules in the network.Their dominant growth illustrates the denitrifying flora in the sediments after SM is added.The ability to utilize inorganic electron donors has been significantly improved,which in turn provides electron donors for nitrification and denitrification.Through the second cycle of the instruction experiment,it can be seen that the synthetic microecosystem system cooperates with the water source reservoir sediments to remove nitrate and nitrogen in the low C/N water body to a certain degree compared with the first cycle,and the nitrogen removal efficiency is increased by approximately 40%.（3）Synthetic micro-ecosystem strengthens the denitrification process and bacterial community interaction mechanism of sediments in landscape water bodies;The denitrification efficiency of synthetic microecosystems and landscape water sediments on low C/N wastewater is increased by about 55%compared with the denitrification efficiency of the lack of electricity donors.High-throughput sequencing showed that the dominant phyla in sediments was Proteobacteria.The dominant bacteria families are Rhodobacteraceae,Zoogloeaceae,Phyllosomaceae,and Pseudomonas family.Network analysis shows that the dominant growth of the genus Rhodanobacter,Ochrobactrum,Halomonas,Thiobacillus and Rhodobacter reflects that the ability of denitrifying bacteria in the sediments to utilize inorganic electron donors and the adaptability of the environment has been significantly improved and improved after the addition of SM.Thereby improving the efficiency of nitrification and denitrification.The second cycle of the instruction experiment showed that the removal capacity of nitrate nitrogen in the raw water of the landscape water body with different initial nitrate-nitrogen concentrations by the SM coordinated landscape water body was48.36%higher than that of the control group without SM.It can be seen that the improvement of the nitrogen removal efficiency is higher than that of the first There are certain differences in one cycle,which may be related to the complex nutritional environment in the raw water.（4）Denitrification performance,metabolic activity and raw water treatment of aerobic denitrifying actinomycetesAt present,the research on the aerobic denitrification characteristics of actinomycetes is rarely reported.An actinomycete with highly efficient aerobic denitrification ability was screened out,and it was identified as Streptomyces sp.and named Streptomyces sp.XD-11-6-2.The removal rate of total nitrogen（TN）in the low-nutrient denitrification medium by this strain was 93.32%,and the removal rate of total organic carbon（TOC）was 90.41%.The results of nitrogen balance analysis showed that about 77.87%of the initial nitrate was transformed into gaseous nitrogen products,and 15.67%of the initial nitrate was transformed into biomass.The Biolog-ECO micro-ecological plate shows that the strain XD-11-6-2 has a strong ability to utilize carbon sources such as carboxylic acids,amines and polysaccharides.The highest actual TN removal rate of the raw water of the city lake is 74.86%.