Experimental Study Of Modified Zeolite On The Simultaneous Remove Of Nitrogen And Phosphorus In Municipal Sewage

Recently,the emission of municipal sewage has always been increasing in our country.Municipal sewage without treatment would contain relatively high concentrations of nitrogen and phosphorus mainly existing in the form of ammonium?NH₄⁺?,nitrate?NO₃^-?and inorganic phosphate?H₂PO₄^-?.Biological treatments are the conventional craft used to remove the nitrogen and phosphorus in many WWTPs.However,it has become much more difficult to satisfy the effluent after treated only by biological treatments with the increasingly strict sewage discharge standards since the quality of effluent was required to be further improved in our country.The adsorption method,clarified as one of the common chemical methods in wastewater treatments,has many advantages such as the high removal efficiency,the simple of device and the small cover area.In this paper,we obtained Na-pretreated zeolite modified by quaternary ammonium silicane coupling agent and sodium chloride.The quaternary ammonium groups would be connected stably through covalent bond to MZ,which can not only remove ammonium nitrogen and phosphorus but also nitrate nitrogen in water simultaneously.Firstly,we optimized the synthetic conditions of MZ.Secondly,the structure and morphology of MZ were characterized and analysed by different methods.The study of adsorption on MZ in simulate wastewater showed that the removal efficiency of nitrogen and phosphorus can be influenced by many factors.The sequences of these factors on the effect of the removal was obtained according to Response Surface Method?RSM?: dose>pH>time.Furthermore,the interaction between these factors and the optimistic adsorption conditions were also studied.This zeolite exhibited outstanding adsorption performance for NH₄⁺,NO₃^-and H₂PO₄^-with a short equilibration time of 30 minutes.And the removal efficiencies of NH₄⁺_N,NO₃^-_N and H₂PO₄^-_P were as high as 54%,97.46%,99.77%,respectively.Additionally,pH of the simulated sewage had little effect on the removal performance of MZ.Besides,the coexistence ions experiments showed that both the SO₄^2-and Clions had negative influence on the removal of NO₃^-with the order: SO₄^2-> Cl^-.The further study showed that the adsorptions of MZ were well fitted with Langumuir and Freundlich isotherm and pseudo-second-kinetics could better describe the adsorption kinetics on MZ.According to the thermodynamic study,the adsorptions were spontaneous and endothermic process.According to the study of adsorption and regeneration on MZ in actual sewage,MZ can be used to remove NH₄⁺,NO₃^-and H₂PO₄^-simultaneously with the best removal efficiency of 60.57%,91.11%,93.22%,which indicated that the concentration of SO₄^2-in sewage would not have significant negative effect on removal efficiency of NO₃^-.The saturated MZ could be regenerated easily by NaCl solution only and its adsorption capacity was recovered at the same time.