Effects Of Different Powdered Activated Carbons (PAC) Properties On Hydraulically Irreversible Membrane Fouling

Different powdered activated carbons(PAC)were employed as adsorbents before ultrafiltration treatment.The efficiency of these PAC on irreversible membrane fouling control could be known by comparing the experimental data.The foulants that caused irreversible membrane fouling during UF of Dongjiang river could be identified by high performance size exclusion chromatography(HPSEC)and fluorescence excitation-emission matrix(EEM).There were four samples of PAC used in PAC-UF system.Relationship among the physical and chemical properties of PAC,PAC performance of removal natural organic matters(NOM)and ultrafiltration(UF)membrane irreversible fouling were investigated to understand the process of PAC adsorption to ultrafiltration fouling control by immersed hollow fiber ultrafiltration fouling test.The results showed that PAC pretreatment of all samples in this study can mitigate physically irreversible membrane fouling.Specifically,the order of the effect of PAC pre-adoption on irreversible fouling control was Hongsheng>Norit>A>N1,while the order of these PAC adsorption capacity on NOM was Norit>A>Hongsheng> N1.The results showed that the process of PAC adsorption controlling irreversible fouling was not decided by the adsorption capacity for total organic matter in water of PAC.Further study found that the physical(surface area)and chemical(alkali group)surface properties of PAC were critical factors for irreversible fouling control.Pilot-scale performances for ultrafiltration of Dongjiang river water without and with coagulation–adsorption-sedimentation pretreatments were conducted to investigate hydraulic irreversible fouling control of short ultrafiltration processes at low flux.Results showed that the frequency of backwashing was 1.8 days in the ultrafiltration unit without pretreatment at 10L/m2 h,while total fouling rate with coagulation-adsorption-sedimentation pretreatment was little without backwashing during 7days at the same flux.Furthermore,when flux increased to 17 L/m2 h,the irreversible fouling was not observable with coagulation-adsorption-sedimentationpretreatment.Coagulation-adsorption-sedimentation pretreatment decreased irreversible fouling by higher removal efficiency of protein-like and fulvic substances,which were the foulants responsible for irreversible fouling during ultrafiltration.