Research On Efficiency And Mechanism Of Advanced Treatment Of Municipal Wastewater By UF/MF+RO

As an effective way to relieve water shortage problems,advanced treatment and reuses of minicipal wastewater have been increasingly concerned.However,most of the existing conventional treatment technologies of minicipal wastewater are confined to the removal of COD,nitrogen,phosphorus and other conventional pollutants,but the removal of certain poisonous and harmful substances,such as dissolved organic matter are limited,the related mechanisms are unclear enough,which have become the bottleneck to restrict the advanced treatment and reuses of minicipal wastewaterMembrane separation technology is widely used in advanced treatment of minicipal wastewater in recent years.According to the quality characteristics of the secondary effluent,combined with the features of membrane separation technology,the main object of this study was chosen to be DOM in the secondary effluent on the basis of research and investigation of DOC,COD,NH4+-N,pH,ultraviolet-visible absorption spectrum and three dimensional fluorescence spectrum characterization of DOM in different function units of conventional processes in typical minicipal wastewater treatment plants,and the features of reverse osmosis water were studied by using ultrafiltration or microfiltration for the pretreatment technology of reverse osmosis respectively.The results showed that,as the pretreatment technology,compared with microfiltration technology,ultrafiltration was more conductive to DOM removal.In order to determine the optimal process parameters and investigate the influence of influent pH value,operating pressure and recovery rate on the reverse osmosis water quality,ultrafiltration and reverse osmosis integrated technology was used to conduct the orthogonal experiment and single factor experiment.The results showed that the order of those factors affecting the removal rate of COD was influent pH > recovery rate > operating pressure;Factors affecting the removal rate of NH4+-N order was influent pH > operating pressure > recovery rate;Factors affecting the removal rate of DOC order was influent pH > operating pressure > recovery rate;Factors affecting the decrease rate of conductivity order was influent pH > operating pressure > recovery rate;Factors affecting the decrease rate of TDS order was influent pH > operating pressure > recovery rate.Within the experiment range,the optimum influent pH was determined to be 6,operating pressure was determined to be 0.2 Mpa,and the recovery rate was determined to be 50%.By preliminarily investigating the pollutants removal mechanisms of ultrafiltration and reverse osmosis integrated technology,it was found that the removal of COD,NH4+-N,DOC(approximate contents of DOM),the decrease of conductivity and TDS,were mainly depended on physical screening actions,and some electrostatic interaction;macromolecules,such as DOM containing aromatic structure can be effectively removed by interception,humus organic matters won't promot the "concentration polarization" of membrane fouling.The results can provide technical bases to engineering applications of minicipal wastewater advanced treatment with membrane integrated technique.