Abstract
Experiments have been conducted to identify the fouling mechanism during the crossflow filtration of a model yeast fermentation broth of Vinyl Acetate particles suspended in a Bovine Serum Albumin (BSA) solution. These have been conducted with filter modules, to obtain quantitative data for the rate and the extent of flux decline due to membrane fouling, and with filter coupons, to obtain quantitative data for the build up of the fouling layer with each individual system and the mixed system. The data from the individual systems have been analysed and then used to determine their fouling mechanisms; this information has been used to predict the fouling mechanism for the mixed system. Finally, this prediction has been compared to the actual fouling mechanism determined by analysis of the mixed system data. For the model particulate suspension, the fouling was due to the build up of a cake layer, as with dead end filtration; however, fouling was limited by membrane scouring. For the model macromolecular solution, a four part fouling mechanism was identified: initially aggregates formed within the pores; the concentration at the membrane surface increased until protein came out of solution as strands; the strands disappeared causing increased aggregation in the pores; finally, a mesh formed on the membrane surface. For the mixed system, fouling was due to the formation of a particle cake on the membrane surface with protein aggregates forming in the pores. The fouling kinetics could be predicted by considering the results from the individual systems; however, the fouling mechanism could not be predicted without using visualisation experiments due to the interactions between the particles and the macromolecules.