Study On The Treatment And Regeneration Mechanism Of Zeolite-microfiltration Process For Ammonia Nitrogen In Wastewater

The urban river water gradually tends to be malodorous black because of the wastewater discharge from production,living and other scattered effluent along the river.This phenomenon was not only affected the image of city but also destroyed the ecological balance in water environment,even endangered to human health.The excess of ammonia nitrogen is one of the main causes for malodorous black river.Therefore,it is significant to develop an economical and efficient treatment technology of removing emergently ammonia nitrogen in river,for protecting the water ecology and promoting the economic development of riverside.Traditional biological denitrification technology was not suitable to treat the river body for the complex influencing factors.Furthermore,the air stripping,chemical precipitation method,electrodialysis and reverse osmosis were also not suitable for black smelly river because of those required process conditions and costs.However,the ammonia nitrogen could be removed rapidly and efficiently by the adsorbent with better cationic exchange capability considering the regeneration process.In this study,zeolite adsorbents were researched due to their cheap,stable and cation selective performance.And the mechanism of ammonia nitrogen rapidly removal and zeolite regeneration process were investigated by powdered zeolite-microfiltration process.The effects of different zeolites on ammonia nitrogen removal and desorption regeneration were compared through ammonia nitrogen adsorption experiment.The competition of cations in aqueous solution was investigated through orthogonal experiment and zeolite molecular sieve experiment,and the cationic exchange adsorption process of zeolite was analyzed.The ammonia nitrogen removal efficiency of natural zeolites was obviously below to the artificial zeolite because of the interference of competitive cations on the surface.The experimental results showed that the surface properties of zeolites,the concentration of coexisting cations and the affinity of cations were the main factors affecting the cationic exchange order of zeolite.The cations exchange order of artificial zeolite for urban river was Ca²⁺>Mg²⁺>NH₄⁺>K⁺>Na⁺,which was verified by cationic partition coefficient experiment.The NaClO was dosing for artificial zeolite regeneration,and the regeneration conditions were optimized in order to recycle zeolite and reduce operating cost.When the molar ratio of chlorine/ammonia?Cl₂/N?was 1.5:1,the oxidation breakpoint of ammonia nitrogen was reached.The zeolite was regenerated due to the ammonia nitrogen on the surface was completely oxidized after 10 minutes of reaction.Ammonia nitrogen removal process and the regeneration of zeolite were carried out separately,which effectively avoided the damage of oxidizer residues to the water ecological balance.A prediction model of ammonia nitrogen removal was established to accurately predict the denitrification efficiency of powdered zeolite-microfiltration process considering the competitive cations(Ca²⁺,Mg²⁺),ammonia nitrogen concentration,and zeolite dosage through response surface experiments.That model could predict the ammonia nitrogen removal rate accurately within the design range of parameters.The denitrification effect of powdered zeolite-microfiltration process was investigated through the immersed column experiment.The operation process was simple and the quality of effluent was stable.The ammonia nitrogen removal effect could be improved by increasing the amount of zeolite and the reaction time.The combined process of ultrafine zeolite-microfiltration-NaClO regeneration was investigated to rapidly remove ammonia nitrogen from urban rivers.The process of ammonia nitrogen exchange adsorption was completed in a short time,while improving the quality of river water,predicting the effluent concentration accurately.The zeolite was regenerated by NaClO breakpoint oxidation along with the washing of microfiltration membrane to avoid the oxidant residues in the water.The process is simple and efficient without secondary pollution,which provides technical support and guarantee for rapid treatment of the polluted urban river water bodies.