The Variation And Combined Model For Complex Fouling Process With Combined Fouling Mechanisms

Membrane technology is used as a high-efficiency separation unit in many fields such as water treatment,but membrane fouling has restricted the wide application of membrane technology in industry.Research on the membrane fouling process can provide guidance for the actual industrial process and membrane cleaning process.In this paper,different feed suspensions/solutions were filtered by microfiltration or ultrafiltration membranes.The single or complex fouling mechanisms were determined.And corresponding mathematical models were established for different fouling mechanisms.First,the deposition factor?s?was introduced in the filtration process of cake filtration,taking into account the differences in the deposition properties of different solute particles on the resistance of the filter cake.The strong sedimentation capacity of activated sludge suspension and kaolin had a strong adsorption capacity,resulting in a higher deposition factor?s>1?.In contrast,for the yeast suspensions,sodium alginate?SA?,humic acid?HA?and bovine serum albumin?BSA?solutions,weaker adsorption capacities were observed,some solute particles remained in the layer adjacent to the cake layer,so the deposition factor was small?s<1?.The original cake filtration model parameter?was a function related to the feed liquid concentration,while the parameter??in the modified model was a constant,independent of the feed concentration and transmembrane pressure.The relationship between the two could be described as?=??C^s-1.And the modified cake filtration model had stronger applicability than traditional cake filtration model.After that,in the constant pressure operation mode,bovine serum albumin?BSA?was used as the feed solution and the PAN 0.1?m microfiltration membrane was used as the filter medium.A mathematical model for the complete blocking-cake filtration process was established.The combined model had a higher accuracy?relative error=1.83%?than cake filtration?relative error=7.29%?,complete blocking?relative error=15.90%?and other pore blockages model?relative error=5.54%?.This model could predict the transition point where the fouling mechanisms changing from complete blocking and cake filtration into single cake filtration.And this transition point occured earlier at higher pressures and higher concentrations.Complete blockage was less at higher pressures and lower concentrations,and the filtration process could achieve larger membrane frontal areas.Finally,the bovine serum albumin was used as the feeding liquid and the PAN 0.1?m microfiltration membrane was used as the filter medium in the constant flow mode of operation.A combined model was developed to determine that the flux variation in the complicated membrane fouling process caused by intermediate blocking and cake filtration.This model could predict the transition point of fouling mechanism in the constant flow operation process.And this transition point appeared earlier with larger flux,lower stirring speed and higher concentration.Meanwhile,lower fluxes,higher stirrer speeds,and less contaminants caused by intermediate blockages at lower concentrations resulted in larger membrane effective areas for the filtration process.Moreover,the model had a good application and could be accurately applied in the cake filtration process of yeast suspension,the combined intermediate blocking and cake filtration process of SA and BSA.