Research On Removal Of Ammonia Nitrogen From Water By Phragmites Communis Biochar Substrate And Immobilized Microbial Technology

Ammonia nitrogen comes from a wide range of sources and can cause eutrophication when discharged randomly.It has important practical significance to reduce the concentration of ammonia nitrogen in water.In recent years,as a new type of biotechnology,immobilized microbial technology has been applied to the treatment of nitrogenous wastewater and has achieved certain effects,and has a good application prospect.The use of efficient and low-cost carrier materials is the focus of research.As an inorganic carrier for immobilized particles,the biochar matrix improves the immobilization technology and has great application prospects for the removal of ammonia nitrogen.In order to research the effect of biochar on ammonia removal by immobilization technology,this paper used phragmites cormmunis,a dominant species of emergent plants that widely distributed in China,as raw material to prepare biochar.And combined with the embedding material to prepare the immobilized particles of Immobilized Denitrifying bacteria.In order to determine a reasonable immobilization scheme,this research designed orthogonal experiments of immobilized composite materials and determined the optimum carrier ratio;Tested the immobilized particles,and researched the effects of the particle size of modified biochar and bio char on the degradation of ammonia nitrogen by the immobilized particles;Used high-throughput sequencing to analyze the denitrification bacteria in different immobilized particles,and discussed the effect of biochar on the microbial community of immobilized particles from the microbial point of view;Researched the effects of adsorption time,initial ammonia nitrogen concentration,biochar dosage,solution pH and temperature on the adsoxption of ammonia nitrogen by immobilized particles.The main work and conclusions of this paper are as follows:(1)Phragmites communis Biochar contains a large number of oxygen-containing functional groups.Scanning electron microscopy results show that biochar has rich pore structure,magnesium modified biochar has more uniform microporous structure,and magnesium modified biochar has increased specific surface area.122.406m2/g,pore volume and average pore diameter decreased by 0.132cm3/g and 2.472nm,respectively,and the average particle size also decreased.XRD confirmed the presence of modified biochar MgO,and the adsorption capacity of modified biochar increased from 0.149 mg/L increased to 0.1919 mg/L After 21 days of acclimation of activated sludge,the oxygen consumption rate OUR value and ammonia oxidation rate were 4.2 times and 5.5 times,respectively,compared with the pre-acclimation sludge,and the final ammonia nitrogen removal rate was 93%,indicating that the sludge has good nitrification performance and domestication.carry out.The optimal combination of immobilized particles was determined by orthogonal experimental analysis,namely,PVA content was 8%,SA content was 3%,mud content was 60%,and carbon content was 1%;(2)Scanning electron micrographs of the inner and outer surfaces of biochar-immobilized particles with particle diameters of 0.60mm,0.45mm,0.30mm,and 0.15mm,respectively,can be seen that the smaller the particle size,the coarser the surface of the particles,and the grain on the cut surface.The smaller the diameter,the more uniform the pore distribution;when the particle size is 0.15 mm,the adsorption effect is optimally 0.43 mg/g.The study on the properties of three kinds of immobilized particles without adding biochar,adding biochar and adding modified biochar A,B and C showed that the addition of biochar enhanced the buffering capacity of immobilized particles to acid and alkali,and significantly improved.The mass transfer performance of the particles,B and C were increased by 28%and 52%,respectively.There was no difference in the mechanical strength of the particles,and the removal rate of ammonia nitrogen was increased.The highest stability of the C group was 96.34%;(3)The high-throughput sequencing results of the immobilized particles of A,B and C showed that the carrier material had a significant effect on the succession of the immobilized microbial community.Adding immobilized particles of biochar at the level of the door,Proteobacteria,Firmicutes,Planctomycetes,etc.,increased the abundance of dominant bacteria in the denitrification;at the genus level The content of denitrifying bacteria in the immobilized particles of Groups B and C increased significantly,and aerobic denitrifying bacteria appeared,indicating that biochar and modified biochar improved the structure of immobilized particles and provided a microenvironment for the growth of denitrifying bacteria;(4)The adsorption of ammonia nitrogen by immobilized particles reached adsorption equilibrium after 48h.The quasi-secondary kinetic equation can better fit the kinetics of adsorption of ammonia nitrogen by immobilized particles,indicating that the adsorption process is controlled by the chemisorption process.Intraparticle diffusion control is not the only rate control step.The adsorption process may be controlled by both adsorbent surface adsorption and intraparticle diffusion;the adsorption amount is proportional to the initial concentration,and the maximum adsorption value is 1.61 mg/g.The Langmuir-Freundlich model can better describe isothermal adsorption,which is controlled by Langmuir adsorption and Freundlich adsorption;the adsorbent dosage is fixed proportional to the ammonia nitrogen removal rate,and the ammonia nitrogen adsorption amount is In inverse ratio,the ammonia nitrogen concentration is 50mg/L,the optimal dosage is 8g/100mL,the removal rate is 86%at 48h,and the adsorption amount is 0.43mg/g.The ammonia nitrogen degradation rate of water gradually increases with the increase of pH value.At 8 and below 6,the ammonia nitrogen removal rate is less than 60%,and the optimum pH should be around 7.5.At a solution temperature of 15?,the ammonia nitrogen removal rate is only 67%.When the temperature continues to rise to 40?,,the accumulation of nitrate nitrogen salt increased to 5.37 mg/L,and the temperature of the immobilized particles at 25? to 30? was the optimum temperature for the reaction to occur.