Study On Performance Of Ion Exchange For Deep Denitrification Of Municipal Sewage

With the increasingly stringent discharge standards of pollutants in urban sewage treatment plants,sewage treatment plants are facing the challenge of upgrading and transformation.Due to the limitation of traditional biological denitrification efficiency,the total nitrogen emission of many sewage treatment plants is difficult to meet the standard,and the main reason is the high nitrate nitrogen concentration.Restricted by the occupancy of municipal wastewater treatment plants,how to achieve low-cost,fast and efficient removal of nitrate in water has become one of the main difficulties in upgrading municipal wastewater treatment plants.Ion exchange method has the advantages of high adsorption efficiency and land saving,and can be used for denitrification of municipal wastewater treatment plant tail water.In this paper,201×7 resin was selected to treat simulated NO₃^-wastewater.The adsorption effect of resin on NO₃^-in water under different conditions was investigated through static and dynamic experiments.The results show that:?1?In the static adsorption experiment,when the initial concentration of NO₃^-is100 mg/L,the optimum adsorption time is 30 minutes,and when the dosage of the resin is 8 g/L,the equilibrium adsorption capacity is 10.9 mg/g.At the same time,the influence of the main anions in water on the adsorption of NO₃^-is discussed,and the strength of inhibition effect is as follows:SO₄^2->PO₄^3-;the optimum concentration of analytical solution is 20%NaCl.The adsorption of NO₃^-by ion exchange resin conforms to Langmuir isothermal equation and quasi-second-order kinetic equation,and belongs to monolayer adsorption;the adsorption process is spontaneous endothermic reaction with increasing entropy.?2?In the dynamic adsorption experiment,when the initial concentration of NO₃^-is 50 mg/L,the optimal outlet flow rate is 4 mL/min,and when the ratio of height to diameter is 2.5,the ratio of solution volume to resin volume?BV?is 310;the time when the resin reaches the penetration point decreases with the increase of the initial concentration and flow rate of NO₃^-;the penetration volume of resin increases with the increase of the ratio of height to diameter,and with the resin penetration volume increases from 1 to 5,the BV increases from 80 to 674.?3?In the repeated experiments of adsorption and desorption,the lower the flow rate of the desorption liquid,the better the desorption effect.With the increase of the volume of the desorption liquid,the desorption rate increases continuously.When the dosage of the desorption liquid is 50 mL and the flow rate of the desorption liquid is 5mL/min,the desorption efficiency is 95.5%.After 10 times of reuse,the resolving power of the resin is still higher than 92%,which fully illustrates the feasibility of application in engineering.