A novel nanofibrous microfiltration membrane system, fabricated from surface functionalized polyacrylonitrile (PAN) electrospun nanofibers, was demonstrated for the effective removal of bacteria and viruses from contaminated water. For membrane modification, dual-vinyl and tri-vinyl monomers were polymerized on the surface of the PAN electrospun nanofibers, which also improved the membrane mechanical properties due to the formation of a cross-linked. Meanwhile, the dual-vinyl monomer with an imidazolium cation resulted in positively charged electrospun PAN nanofibers, allowing the membrane to create not only 2-3 times higher permeation flux or lower pressure drop, but also 99.9999% retention of bacteria (e.g., Escherichia coli) and 99.99% retention of bacteriophage (e.g., MS2) during microfiltration when compared with commercial microfiltration membranes (e.g., 90% retention of MS2). (C) 2013 Elsevier B.V. All rights reserved.