Membrane biofouling is a serious problem limiting widespread application of membrane technology. Modification of membranes using silver nanoparticles appears to be a promising option for mitigating biofouling. NADIR (R) UP150 ultrafiltration membranes made of polyethersulfone were modified with different forms of nanosilver through (i) diffusion of silver ions with subsequent reduction, (ii) addition of polyethyleneimine-capped silver nanoparticles, and (iii) thermal-pressure fixation of silver-modified nanofibres. The modified membranes for any changes in permeability, antimicrobial properties, silver leaching and contact angle were examined. All modified membranes displayed antimicrobial properties. Both membranes modified through diffusion of silver and polyethyleneimine-capped silver nanoparticles method mitigated biofouling. These membranes also showed slightly higher permeability than the unmodified control, while silver-modified nanofibre membranes had the lowest permeability of all the membranes tested. Filtration results corresponded well with contact angle measurements. All modified membranes exhibited low levels of silver leaching over time. (C) 2015 Elsevier B.V. All rights reserved.