Scale-up of microfiltration systems: Fouling phenomena and V_max analysis

Proper sizing and scale-up of normal flow filtration devices requires an understanding of the effects of membrane fouling on system capacity. The V_max test is often used to accelerate testing and reduce the required process volume, but the underlying assumption that fouling occurs by uniform constriction of cylindrical membrane pores is rarely met in practice. We have examined the validity of the V_max model and have compared the results with predictions of a new model that accounts for fouling due to both pore blockage and cake formation. The V_max analysis significantly overestimates the system capacity for proteins like bovine serum albumin that foul primarily by pore blockage, but it underestimates the capacity for lysozyme which fouls primarily by cake formation. In contrast, the pore blockage-cake filtration model provides a much better description of membrane fouling, leading to more accurate sizing and scale-up of normal flow filtration devices.