Four fouling mechanisms based on Hermia model (complete pore blocking, intermediate pore blocking, cake filtration, and standard pore blocking) have long been used to describe membrane filtration and fouling in constant transmembrane pressure (TMP) operation of membranes. However, these models have not been reported for constant flux crossflow filtration, despite the frequent use of this mode of membrane operation in practical applications. We report derivation of these fouling mechanisms for constant flux crossflow filtration. Of the four mechanisms, complete pore blocking and standard pore blocking were inapplicable due to contradicting assumptions and relevance, respectively. Constant flux crossflow fouling experiments of dilute latex bead suspensions and soybean oil emulsions were conducted on commercial poly (ether sulfone) flat sheet ultrafiltration membranes to explore their abilities to describe such data. A model combining intermediate pore blocking and cake filtration models appeared to give the best agreement with the experimental data. Below the threshold flux, both the intermediate pore blocking model and the combined model fit the data well. As permeate flux approached and passed the threshold flux, the combined model was required for accurate fits. Based on this observation, a physical interpretation of the threshold flux is proposed: the threshold flux is the flux below which cake buildup is negligible and above which cake filtration becomes the dominant fouling mechanism.

Fouling mechanisms in constant flux crossflow ultrafiltration

2019 Spring National Meeting

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