Study On The Mechanism Of Magnetic Air Stone Biofilm System Used To Treat Total Nitrogen In Domestic Sewage

The treatment of urban domestic sewage is a hot issue in today’s society.A large amount of domestic sewage containing nitrogen is directly discharged into natural water systems without effective treatment.Therefore,how to improve the removal efficiency of total nitrogen in water and reduce water pollution has become a worldwide issue.An important research direction is the application of magnetism in wastewater has always been a research hotspot in water treatment technology,and it plays an important role in enhancing microbial activity and improving wastewater treatment efficiency.The thesis used magnetic biofilm system to treat simulated domestic sewage,using total nitrogen in water and biofilm samples as the research object,using a variety of extracellular polymer（EPS）methods and high-throughput sequencing methods to explore magnetic pairs the influence of biofilm composition and bacterial richness and diversity,and the acceleration mechanism of magnetism on the electron transport chain of denitrification is discussed in depth.In order to accurately evaluate the root cause of the change in the total nitrogen removal efficiency affected by magnetism,and for the feasibility and safety of magnetic application of sewage treatment.It provides a theoretical basis to achieve the goal of economical and efficient removal of pollutants.The research results show that after the comparative experiments of air stone and magnetic air stone biofilm system to treat domestic sewage,the pollutant removal efficiency in the water has changed significantly.Among them,the average removal efficiency of COD,TN and NH4⁺-N increased by 17.15%,16.10%and 11.58%,respectively.The high-throughput sequencing results found that compared with air stone,the number of bacteria in magnetic air stone biofilm increased from 578 to 699,the Shannon index of community diversity increased from 5.97 to 6.49,and the richness of Proteobacteria increased from 37.91%to 41.91%,it became the main dominant species.The abundance of Bacteroides phylum decreased from 20.28%to 18.41%,and Firmicutes,Actinomycetes,and Nitrospira related to denitrification increased from 13.4%to 15.47%,11.76%to 12.21%,7.16%to 7.55%,respectively.And the magnetic biofilm system newly formed Bacilli.At the same time,the experiment determined the protein（PN）and polysaccharide（PS）content in extracellular polymer,and carried out FT-IR,EEM and XPS characterization on loose extracellular polymer（LB-EPS）and tight extracellular polymer（TB-EPS）,the results show that magnetism reduced the production of protein and polysaccharides.Then the dehydrogenase activity was measured,and the average dehydrogenase activity in the magnetic air stone biofilm reactor was 34.42 mg·（g·h）^-1,and the air stone system was 31.82 mg·（g·h）^-1.The results indicate that magnetism enhances dehydrogenase activity.Finally,by adding rotenone,mipalene dihydrochloride（QDH）and sodium azide respiration inhibitor,the effect of magnetism on the electron transfer of denitrification was studied.The results show that magnetism increased the nitrate conversion efficiency by accelerating the activity of nitrate reductase,and determined the acceleration site in the NO3^-to NO₂^-.The research results are of great significance for broadening the magnetic in the field of biological wastewater treatment,especially to supplement the lack of research on the mechanism of magnetic accelerated biofilm denitrification,laying a foundation for subsequent research on the effect of magnetic on microorganisms.At the same time,it also provides an important basis for evaluating the impact of magnetism on sewage treatment.