Fatty acids can be extracted from an oil phase by forming a dispersed phase of saponified fatty acids/water/isopropanol in oil. This dispersion can be separated in the two phases by two membranes of opposite polarity in series. In this study the separation of the water phase from the dispersion by a hydrophilic membrane and the mechanisms underlying the flux characteristics are investigated. The permeation flux through a PAN ultrafiltration membrane is optimized with respect to the fatty acid/water/isopropanol ratio. It appears that a 1:6.5:3 (v/v) ratio gives the highest flux [95 L/(m2-h-bar)]. The dispersion at these conditions consists of a continuous oil phase as well as a continuous water phase between 20 and 65% water phase hold up. The flux/pressure curve shows a linear increase of the flux with pressure at low pressures (determined by the membrane resistance), followed by a maximum flux value for the case where the volume of the water phase present in the inflow is limiting. It is not possible to remove the water phase with membranes below a water phase hold up of 20%. At this hold up value the transition between a bicontinuous and a discrete dispersion also occurs.