The characteristics of calcium-aggregated humic acid assemblages that deposit on microfiltration membranes are determined in this study using a novel approach involving the analysis of filtration and deliquoring behaviour as a function of time over a range of constant applied pressures. The filtration-deliquoring approach initially provides the cake thickness and porosity at the conclusion of the filtration phase which, when combined with the steady state fluxes that result over a range of particular applied pressures, enables determination of the local permeability and porosity through the cake at any applied pressure. Within the range of the applied pressures examined (12.5-150 kPa), the humic acid layer has been shown to be very porous with a moisture content of more than 96%. However, despite this high porosity, the fouling layer has very low permeability with the permeability decreasing with increase in pressure. With knowledge of these material properties, the filtration behavior of the humic acid fouling layer under constant flux operating condition can be predicted. (C) 2010 Elsevier B.V. All rights reserved.