The use of liquid-solid fluidization as a means of membrane fouling mitigation has aroused increasing attention especially in membrane bioreactors. Past studies have affirmed a relationship between the fluidized GAC media and fouling trends, and also shed light on the effects of superficial liquid velocity, power requirement, GAC particle diameter and foulant type on the effectiveness of fouling mitigation during microfiltration. In particular, the ratios of the local critical flux to the overall critical flux (J(c,Local)/J(c,overall)) were shown to deviate from unity, owing to different expanded bed heights of the fluidized GAC and causes non-uniform fouling across the membrane. Accordingly, this study was aimed at understanding the impact of different overall GAC concentrations, which give different expanded bed heights, on the extent of fouling mitigation. Monodisperse millimeter-sized GAC were used as the fluidized media and the particulate foulants were micrometer-sized polystyrene and bentonite particles. The results indicate that the highest overall concentration was advantageous in terms of enabling (i) higher membrane fouling mitigation at a lower power required per unit permeate (P-p) for the polystyrene foulant but not bentonite foulant; and (ii) more similar J(c,overall) values over the three heights investigated, which implies more uniform fouling mitigation across the membrane. The relative benefits of adjusting overall GAC concentration versus the particle diameter of the GAC media were also critically assessed. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.