Removal Of Ammonia Nitrogen Simulated Wastewater By Macro-porous Sintered Zeolite Ball

With the acceleration of urbanization and the rapid development of industry and agriculture,a large amount of ammonia-nitrogen-containing sewage is discharged into the rivers and lakes.Ammonia nitrogen is one of the main substances that cause eutrophication of water.In recent years,domestic and foreign scholars have conducted extensive research on the removal of ammonia nitrogen in water.The physicochemical treatment combined with biological treatment of ammonia nitrogen has attracted extensive attention.Zeolite is a hydrous alumino-silicate natural ore with tetrahedral structure,which has strong adsorption ability to polar molecules such as NH_3.Zeolite is abundant and widely distributed and low price.It has been used as an economic substance to treat eutrophic sewage.The main purpose of this paper is to study an economical and effective method for zeolite modification,and the modified zeolite can be used as a potential filtration medium in the reactor.First of all,the adsorption characteristics of natural zeolite were studied,and the effect of HCl,NaOH,NaCl and thermally modified zeolite for ammonia nitrogen removal was compared.On the basis of traditional modified zeolite,a macro-porous sintered zeolite ball was studied,and the effect of different preparation conditions on the removal of ammonia nitrogen by zeolite ball were studies.Then,the study aimed to research the zeolite ball loaded with EM bacteria,and the effect of ammonia nitrogen removal by zeolite ball loaded with EM bacteria and original zeolite ball were compared.The factors influencing ammonia nitrogen removal by zeolite ball loaded with EM bacteria were investigated.Finally,a biological aerated filter was designed,and the dynamic adsorption experiment of loading zeolite ball is compared with natural zeolite,ceramsite,imported culture ball and domestic culture ball.It shows that the particle size of natural zeolite is 0.5-1mm,and the adsorption time is 5 minutes,for 100ml,10mg/L ammonia nitrogen reaches the highest removal rate and adsorption capacity,4.24%and 0.088mg/g,respectively.In addition,increase of zeolite dosage and decrease of initial concentration of ammonia nitrogen,the adsorption capacity of natural zeolite for ammonia nitrogen will be reduced.The removal effect of natural zeolite on ammonia nitrogen can be improved after HCl,NaOH,NaCl and thermo modification.Among them,NaOH modified zeolite has the best effect on the removal of ammonia nitrogen,the second is NaCl modified zeolite,HCl modified zeolite has the worst effect on the removal of ammonia nitrogen.The optimum calcined temperature of the zeolite ball is between 400-600?,the optimum calcined time is between 3-5 hours,the optimum size of the pore-forming agent is between 0.4-2.4mm,the optimum raw material proportion is 2-3:1:1,and the optimum size of zeolite ball is 1.2-1.5mm.The Langmuir equation can better fit the adsorption isothermal process of zeolite ball than the Freundlich equation.By the Langmuir adsorption isotherm equation fitting the maximum adsorption capacity of zeolite ball was 2.847 mg/g,actual experiment measured the maximum adsorption capacity can reach 3.527 mg/g.Zeolite ball for 100mL,10 mg/L of ammonia nitrogen,the maximum removal rate can reach 93.86%.The pseudo-second-order model adsorption kinetics equation can better describe the process of ammonia nitrogen adsorption by zeolite ball.According to the inter-particle diffusion model,the control step of ammonia nitrogen adsorption is mainly inter-particle diffusion.The optimum condition of zeolite ball loaded with EM bacteria was:the zeolite ball was contact to EM bacteria at a concentration of 2.4×10⁹cfu/ml for 6 hours.Under this condition,the highest removal rate and adsorption capacity of 100mL,10mg/L ammonia nitrogen were 98.17%,0.307mg/g,respectively.By Langmuir adsorption isotherm equation,the maximum adsorption capacity of zeolite ball loaded with EM bacteria was 5.587mg/g.Compared with the original zeolite ball,the maximum adsorption capacity is increased.The pseudo-second-order model adsorption kinetics equation can better describe the process of ammonia nitrogen adsorption by zeolite ball loaded with EM bacteria.According to inter-particle diffusion model,the control step of ammonia nitrogen adsorption by zeolite ball loaded with EM bacteria is controlled by several steps.Comparison of inter-particle diffusion model between zeolite ball loaded with EM bacteria and natural zeolite ball,it shows that the control steps of ammonia nitrogen adsorption by zeolite ball loaded with EM bacteria are may influenced by microorganisms.Compared with natural zeolite,ceramsite,imported culture ball and domestic culture ball,zeolite ball has the best dynamic adsorption effect on ammonia nitrogen simulated wastewater with 100L concentration of 10mg/L.The optimum operating conditions of the reactor are:The influent flow rate is 100L/h,increase the hydraulic retention time around 8 hours,adjustment of hydraulic retention time to initial operating state after 2 hours,the influent flow rate can be increased after the reactor is stable.Under this condition,the maximum removal rate of ammonia nitrogen is90.56%,and the adsorption amount is 0.547mg/g.