In the present work, the hydrodynamic behaviour of a water-soluble polymer (ethoxylated polyethylenimine) ultrafiltration process has been studied at pilot scale using multichannel ceramic membranes. In a first step, the effects of tangential velocity, transmembrane pressure and temperature on both polymer rejection coefficients and permeate fluxes, have been studied fora given polymer concentration. Secondly, two discontinuous closed-loop experiments have been set up to study the influence of polymer concentration and operation time on design parameters. Next, the presence of concentration-polarization and fouling has been firstly studied and subsequently quantified by means of a resistance in series model. Moreover, a design equation that relates permeate flux to polymer feed concentration has been obtained. Finally, the concentration evolution in both feed tank and recirculation loop has been successfully modelled. (C) 2009 Elsevier B.V. All rights reserved.