气态膜法回收垃圾渗滤液氨氮技术进展与机理探讨

Progress and mechanism of ammonia nitrogen recovery from landfill leachate by gas-permeable membrane process

目前传统生物脱氮工艺中需投加大量碳源用于提高垃圾渗滤液的C/N,且随着填埋龄增加,C/N严重失衡,将导致脱氮成本偏高。氨吹脱(汽提)法、鸟粪石法等脱氮技术已实际应用在垃圾渗滤液脱氮处理中,但总体应用效果均有待提高。气态膜法是一种新型低能耗、高效率的氨氮资源回收技术。综述了气态膜法在高氨氮垃圾渗滤液处理中的应用;并以双膜理论为基础,推导出适用于气态膜法的氨传质机理。气态膜法氨传质过程可归纳为串联阻力模型,即总传质阻力为料液侧传质阻力和气态膜内传质阻力之和,料液侧传质系数(Kf)与气态膜类型及其组件形式、Re和Sc等参数相关,气态膜膜内传质系数(Km)取决于气态膜的孔径、孔隙率、孔径曲折度以及厚度等参数;增大料液流速可促进NH3在料液侧至料液边界层以及料液边界层向膜表面的扩散与传质,从而大幅提高总传质系数(KOV)。简言之,气态膜法可用于垃圾渗滤液、沼液等高氨氮废水脱氮处理与资源化利用,气态膜回收产物可作为化工原料和农业氮肥。

At present,a large amount of carbon sources needs to be added in the traditional biological nitrogen removal process to improve the C/N of landfill leachate.With the increase of landfill age,the C/N imbalance will be serious,which will lead to a high cost of nitrogen removal.Physical nitrogen removal technologies such as ammonia stripping method and struvite method have been used in the nitrogen removal treatment of landfill leachate,but the overall application effect needs to be improved.Gas-permeable membrane process is a novel ammonia nitrogen resource recovery technology with low energy consumption and high efficiency.The application of gaseous membrane process in the treatment of landfill leachate with high ammonia nitrogen was reviewed.Based on two-film theory,the ammonia mass transfer mechanism applicable to the gas-permeable membrane process was derived.The ammonia mass transfer process can be summarized as a resistances-in-series model.The total mass transfer resistance is the sum of the mass transfer resistance on the liquid-metal side and the mass transfer resistance in the gas-permeable membrane.The material liquid side mass transfer coefficient(Kf)is related to the type of gas-permeable membrane and its form,the parameters of Re and Sc,etc.The mass transfer coefficient(Km)of the gas-permeable membrane depends on the pore size,porosity,pore tortuosity and thickness of the membrane.The diffusion and mass transfer of NH3 from the solid-liquid side to the solid-liquid boundary layer and from the solid-liquid boundary layer to the membrane surface can be promoted by increasing the flow rate of the solid-liquid,thus greatly increasing the total mass transfer coefficient(KOV). In brief,gas-permeable membrane process can be efficiently used for the NH3-N re moval and resource utilization of high ammonia nitrogen wastewater such as landfill leachate and biogas slurry,and the recovered products can be used as chemical raw materials and agricultural nitrogen fertilizer.