Experimental Study On The Combined Treatment Of Ammonia Nitrogen And Nitrate In The Grade A Effluent Of Sewage Treatment Plant With Zeolite And Activated Carbon

Water is an important foundation that constitutes a living body and a basic resource on which mankind depends for survival.However,our country’s water pollution is increasing day by day,and the waste of fresh water is serious,making the problem of water resources a key factor restricting our economic development.In addition,there are many types of industrial wastewater,which directly or indirectly affect the lives and health of the people and restrict economic development.Therefore,it is particularly important to pay attention to the treatment of industrial wastewater.In order to explore and solve the technical problems caused by the continuous improvement of the effluent standards of sewage treatment plants,the simulated wastewater with the ammonia nitrogen concentration of 10mg/L and the nitrate concentration of 15mg/L was prepared,and the use of natural Zeolite and activated carbon are used as adsorbents to remove ammonia nitrogen and nitrate nitrogen,respectively.The effect of certain factors on the adsorption process is analyzed,and the removal mechanism is discussed.Determine the factors that affect the adsorption effect of the zeolite+activated carbon combined adsorption column and the best operating conditions to provide a theoretical basis for the treatment of first-level A effluent.The main conclusions of this paper are as follows:(1)The experiment of zeolite static adsorption of low-concentration ammonia nitrogen shows that the optimum p H for adsorption is 7.0,and the removal rate under over-acid or over-alkali conditions is unsatisfactory.The smaller the particle size of the zeolite,the more complex the surface pores and the larger the specific surface area,the better the adsorption effect.The adsorption effect increases with the increase of the dosage and adsorption time.At the inflection point where the dosage is 12g/L and the contact time is 90min,both the material cost and the removal effect can be considered.Orthogonal test results show that the influence of different factors is in the order of p H value>dosing amount>adsorption time>particle size>temperature.Kinetic studies show that the pseudo-second-order model can describe the adsorption process more accurately than the pseudo-first-order model,and the intramolecular diffusion model is not suitable for the entire ammonia nitrogen adsorption process.The fitting degrees of Freundlich and Langmuir curves in the adsorption isotherm simulation are both greater than 0.90,but the former has a better fitting degree,indicating that the adsorption process is a multi-molecular layer adsorption exchange dominated by physical adsorption.In the thermodynamic study,ΔG<0,ΔH>0,andΔS>0 indicate that the experiment can be carried out spontaneously,endothermic,and the degree of confusion increases.(2)The static adsorption experiment of activated carbon showed that the nitrate removal rate increased with the decrease of p H value.The removal rate is directly proportional to the dosage and the adsorption time.When the dosage is 24g/L and the contact time is 120min,the material cost and adsorption efficiency reach the best results.Orthogonal test results show that the influence of different factors is in the order of p H value>dosing amount>adsorption time>temperature.Kinetic studies show that the pseudo-second-order model can describe the adsorption process more accurately.The internal diffusion model divides the adsorption process into three stages,indicating that the intra-particle diffusion is not the only rate determining step.The Langmuir curve fit of the isotherm model is better than the Freundlich curve.At different temperatures,0<R_L<1,indicating that the adsorption process is powerful.In the thermodynamic study,ΔG<0,ΔH<0,andΔS>0 indicate that the experiment can be carried out spontaneously,exothermic,and a process of increasing chaos.(3)The zeolite layer in the adsorption column is on the bottom and the activated carbon layer is on the top.The two materials have a synergistic effect on the adsorption of the two pollutants.Appropriately increasing the volume ratio of zeolite in the column helps to increase the removal rate of total nitrogen.The effect is best when the volume ratio of zeolite to activated carbon is 6:4.The adsorption effect of the dynamic adsorption column is best when the adsorbent filling height in the adsorption column is 250mm,the influent p H is 6,and the influent flow rate is 2m/h,and the ammonia nitrogen and total nitrogen content of the effluent reaches the surface level V water standard.