Screening Of Iron Reduction Mixed Flora And Its Drive For Aerobic Denitrification And Denitrification And Denitrification Study

As an important freshwater resource reservoir,flood control reservoir and species gene bank,water-source reservoirs play a pivotal role in maintaining the normal and orderly development of human society and the balance of natural ecology.In order to improve the pollution of the water environment,the use of biological nitrogen removal technology to carry out in-situ nitrogen removal of water body is one of the more economical and effective methods.In this paper,the iron reduction mixed flora screened in the sediment of the Taro Gou Reservoir was the research focus,and the aerobic denitrification and denitrification and denitrification removal were strengthened by microbial immobilization technology combined with inorganic electronic donor materials,and the following studies were focused on:（1）the population structure,denitrification characteristics and influencing factors of the iron reduction mixed flora;（2）Microbial immobilization technology combined with inorganic electron donor to drive aerobic denitrification characteristics of denitrification;（3）The nitrogen removal mechanism was preliminarily explored by combining organic matter components,iron-carbon materials,and changes in microbial population structure.The main conclusions are as follows:（1）The five groups of iron-reducing mixed flora derived from the sediment of the taro gou reservoir had extremely high community diversity,concentrated in the two major categories of Proteobacteria and Bacteroides,and subdivided into dominant bacteria such as Doauerella,Hydrobacter,Pseudomonas,Nitrogen-fixing Spirobacter,Kinetic Bacteria,Dechlorinomatons,Flavobacterium and Bacillus.The five groups of iron reduction mixed flora could achieve Fe³⁺reduction and denitrification and denitrification and denitrification.Among them,the total nitrogen removal rate of the nutrient-rich iron-reducing mixed flora was above 84.41%.The total nitrogen removal rate of the mixed flora of poor iron reduction was more than 53.01%.The results of single-factor experiments showed that the iron-reducing mixed flora had good nitrogen removal effect in neutral or acidic environment,C/N was 4.99～9,temperature was 25～30°C,and sodium acetate or sodium succinate was the carbon source.（2）The coupling of inorganic electronic donor materials with supported iron reduction mixed flora carrier pellets can significantly improve the efficiency of microbial aerobic denitrification and denitrification.The results showed that the total nitrogen removal rates of the experimental group（B～F）in the first cycle were 45.35%,59.27%,51.07%,68.57%and 73.47%,respectively,which showed higher denitrification efficiency than that of group A,and group B using only inorganic electron donor materials showed lower denitrification efficiency than group（C～F）loaded with iron reduction mixed flora vector pellets.In the second and third cycles,each group of reactors can still carry out continuous denitrification,and the continuous denitrification effect of group F is the best.It also has a good removal effect on permanganate index and total phosphorus.（3）The main CDOM components in different reactors（A～F）are C1,C2 and C3.Through XPS analysis,it was found that there was a formation of high-valent oxides on the surface of iron-carbon materials,mainly in the form of hematite.High-throughput sequencing showed that iron-carbon materials changed the water environment and changed the microbial population structure in different reactors.As the reaction progressed,Groups A increased its richness and diversity after operation compared with before operation.Groups E and F showed increased richness and decreased diversity after operation,indicating that the microorganisms in reactor groups E and F made natural selection to adapt to the new living environment.After the reactor is running,such as Cyanobium＿PCC-6307,CL500-29＿marine＿group and hgc I＿clade,disappeared and were replaced by polynucleobacteria,and water eutrophication was improved.