| Ultrafiltration(UF)is increasingly applied in the production of drinking water and the reclamation of wastewater However,the membrane fouling which might lead to more energy consumption becomes the biggest obstacle for its further application.In this paper,polyvinylidene fluoride(PVDF)hollow fiber membrane was used as the object of study to investigate the effect of UV-activated potassium peroxydisulfate(UV / PDS)on the fouling of UF membrane and its mechanism.The results would provide experimental datas of a reference value and theoretical basis for the applying of advanced oxidation processes(AOPs)to the field of pretreatment of drinking water UF technology.Herein we first explored the effect of UV / PDS on the removal of natural organic matter(NOM)by detecting the variation of UV254 and DOC.Three-dimensional fluorescence-parallel factor method(EEM-PARAFAC)was used to qualitative and semi-quantitative the type and the concentration of fluorescent substances in water.The UV / PDS oxidation reaction kinetics would be given.Then we investigated the effect of UV / PDS pretreatment on the UF filtration by transmembrane pressure(TMP)and membrane fouling resistance(R)and optimized the pretreatment parameters.FTIR and SEM were applied to characterize the functional group structure and morphology of contaminants on the membrane surface,respectively.Finally,the molecular weight characteristics,hydrophobic properties and fluorescence properties of organic matter were measured to reveal the mechanism of UV / PDS pretreatment on membrane fouling controlling.It was found that UV / PDS can remove NOM in water,and the removal effect was related to PDS dose and temperature.The higher the PDS dose,the higher the removal rate of organic matter,for instance,UV / 1.2 mM PDS reaches a mineralization of 80% of NOM.And the higher the temperature,the higher the removal rate of organic matter.The EEM-PARAFAC results show that The results show that there are four fluorescent components and their Ex/Em wavelength are C1:220~240(300~330)nm/390~430 nm?C2:235(290)nm/(330~350)nm?C3:250~280(370)nm/450~500 nm?C4:220~230(275)nm/290~330 nm.C1 and C3 are microbially and terrestrially derived humic-like matter,respectively.C2 and C4 are Tryptophan and Tyrosine protein-like substance,respectively.UV / PDS can remove the fluorescent components and its removal effect was positively related to PDS dose.At the same PDS dose,the removal efficiency of the four fluorescent components is tryptophan-based protein> microbial source humic acid> terrestrial humic acid> lysine protein.The process of oxidizing the organic matter in water by UV / PDS is in accordance with the quasi-first order reaction kinetics.UV / PDS pretreatment does not affect the effluent quality of the UF process and has a certain mitigation effect on the UF fouling.The degree of mitigation is related to PDS dose and UV dose.The relatively low PDS dose can control the fouling of UF.In a certain range,the greater PDS dose,the better the effect;the greater the UV dose,the better the effect.The optimization of the pretreatment parameters are 60 min UV/0.2mM PDS?10min UV/0.4 mM PDS.The FTIR results show that UV / PDS pretreatment can reduce the protein content in the contaminant layer,but the removal of polysaccharides is limited.The results of SEM show that UV / PDS pretreatment makes the dense and compacted cake layer become loose and flake,weakened the adhesion force between cake layer and ultrafiltration membrane surface.The main factor that UV / PDS pretreatment can control the fouling of UF membrane is the change of organic matter properties in water,rather than the reduction of organic matter content.UV / PDS pretreatment can increase the content of small molecules in water,increase the hydrophilicity and reduce the content of fluorescent substances,especially tryptophan-like protein.All these changes can reduce the pollution of ultrafiltration membrane. |
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