The treatment of surface water was studied using different experimental ultrafiltration surface-modified polyethersulfone membranes. They were prepared adjusting three membrane-manufacturing variables: addition of three surface modifying macromolecules (SMMs), the solvent evaporation time and the polyethersulfone concentration in the casting solution. Membrane performance was evaluated in terms of total organic carbon removal, the amount of natural organic matter deposited on top of the membrane after filtration, the permeate flux and the flux reduction. In order to define the manufacturing conditions resulting in the "best membrane", in addition to the performance results, other considerations such as membrane strength and SMM compatibility were necessary. Membranes prepared with a novel polypropylene diol-based additive proved to have a positive effect on the treatment of this particular surface water. A trade-off between total organic carbon removal and permeate flux, and a logical connection between membrane characteristics and performance were observed. Membranes with small molecular weight cut-off (and pore size) had high total organic carbon removals and low-permeate fluxes, consequently, fouling was small. (C) 2003 Elsevier B.V. All rights reserved.