Three surface modification macromolecules (SMMs) with different chemical structures (DEG, DPS and SMM41) were used in the preparation of new polyethersulfone (PES) ultrafiltration membranes, in an attempt to improve their performance in water treatment. During the first stage of this study, the use of SMM41 to modify the surface of PES membranes maximized the permeate flux throughout the experiment, achieved high total organic carbon (TOC) removals and low natural organic matter (NOM) deposition. When polyvinylpyrrolidone (PVP), a pore forming additive, was also used in the casting solution, its effect was not statistically significant in the range studied. Surface modified membranes performed statistically the same as the unmodified membranes. However, the nature of the feed concentrated Ottawa River water (CORW) had an important impact on the performance of these new membranes. The low molecular weight fraction (LMW) of the river water caused less fouling of the membranes, had higher water productivity (permeate flux), although TOC removal was lower. Nevertheless, in general, TOC removals were high, compared with those of ultrafiltration (UF) membranes reported in the literature. Includes 17 references, tables, figures.