Investigation Of Ultrafiltration Membrane Fouling Based On The Pre-treatment With Coagulation And Powder Activate Carbon Adsorption

As an effective way to water separation and purification, coagulation was gradually accepted by ourpeople since the end of last century and gain a great status own its numerous merits include simpleoperation, high separation efficiency together with its wide range of application. Along with the matureof membrane technology, the internal problem of it was emerging day by day, one of the most whichrestrict the large-scale application of this kind of technology is membrane fouling problem. How to solvethis matter on condition that the quality of effluent water is unaffected to maximize the life span ofmembrane is our urgent job. At present, the pre-treatment of membrane separation process is an effectiveto mitigate the membrane fouling problem, our research base on the coagulant of aluminum sulfate,compare the treatment effect of synthetic raw water between Pre-coagulation by alum ultrafiltrationwithout (CUF) and with (CAUF) powered activated carbon (PAC) addition, and distinguish themechanism of membrane fouling under separate pre-treatment process.Our results showed that with pretreatment of CUF under the neutral pH of synthetic raw water andthe optimal dosage of coagulant, the removal efficiencies in terms of UV absorbance at254nm (UV254)and dissolved organic carbon (DOC) were achieved77%and48%respectively compare to83%and57%with CAUF pretreatment. It indicates that the present of PAC strengthens the removal ability of organicmatter. As to turbidity, the addition of PAC conducive to the aggregation and sedimentation of the flocsresult in the lower turbidity in membrane tank of CAUF pretreatment, it doesn’t influence the turbidity ofeffluent water, however. According to the results of Three-dimensional excitation-emission matrix (EEM)fluorescence spectroscopy, the coagulation decreased the fluorescence intensities of CUF influent of peakA by35%and those of peaks T1and T2by30%and25%, respectively. In comparison, the fluorescenceintensities of peaks A, T1and T2in the EEM spectra of CAUF influent decrease by42%,44%and30%,respectively. we can know that the dosage of PAC promote the removal of protein-like substances.In terms of membrane fouling, it was found that the continuous addition of a low dosage of PACreduced membrane fouling for operational run periods <20days, both for reversible and for irreversiblecomponents of fouling. The presence of PAC increased the removal of dissolved organic matter (DOM), particularly proteinaceous substances, and some fractions of humic-type substances. For a longeroperation time (>20days) an increase in mainly reversible fouling was evident and was attributed tomicroorganism growth in the cake layer, as indicated by the enhanced concentrations of extracellularpolymeric substances, such as polysaccharides and proteins, however, this kind of effect can effectivelyavoid through high-pressure tap water periodically.We also find that there might a process of crystallization of the coagulant floc in the cake layer withincreasing operation time and it was believed to cause desorption of DOM from primary coagulationparticles and a decrease in their size, and consequently a higher density of cake layer. PAC absorption ofdesorbed DOM within the cake layer, and residual DOM after coagulation, reduced DOM reaching themembrane surface and the extent of subsequent internal membrane fouling, decrease the irreversiblemembrane on a large extend.