The polysulfone (PS) membranes were prepared by adding different amounts of silver nanoparticle-AgNP (0-1. wt%) into the dope solution. The bare PS and AgNP entrapped PS membranes (AgNP-PS composite membrane) were tested for physical properties with water permeability, MWCO (molecular weight cut-off), AFM, contact angle and SEM analyses, filtration performances by using the model protein (BSA) and carbohydrate (dextran) solutions and biofouling resistances by using a real activated sludge. AgNP addition improved the protein and carbohydrate filtration performances of bare PS membrane. The results of biofouling experiments showed the AgNP-PS composite membranes having lower absorptive and pore fouling values than bare PS membrane. The ionic silver loss from membrane during pure water filtration was measured using inductive-coupled plasma spectrometer (ICP) and the results showed the minimum silver loss from the composite membranes. The results of disk diffusion test showed that the composite AgNP-PS membranes decreased the growth of bacterial colonies. However PCR-DGEE technique showed that there were not significant differences in microbial community population density along the bare and composite membranes. © 2012 Elsevier B.V.