Electrospun nanofiber membranes (with varied fiber diameters and different membrane porosities and thicknesses) have been explored as innovative microfiltration media for the highly efficient and cost-effective removal of contaminations with particle sizes of 0.2 mm (even 0.1 mm) from water. For the first time, the membrane porosity has been judiciously adjusted/controlled by a facile hot-pressing method; and the relationships between membrane properties and microfiltration performances have been systematically investigated. Upon the hot-pressing process, the membrane porosity could be significantly decreased from similar to 86% to as low as similar to 34%, further leading to the substantial increase of rejection fraction from 0% to similar to 100% for 0.2 mm particles; moreover, some of these membranes (consisting of small diameter nanofibers) that were hot-pressed with relatively high pressure could even reject all of 0.1 mm particles. As compared to conventional microfiltration media, these membranes exhibited significantly higher flux values and substantially lower degrees of fouling without distinguishably sacrificing particle rejection fractions. For example, the rejection fraction and permeate flux value of one membrane (fiber diameters: similar to 150-250 nm, membrane porosity: similar to 40%) were similar to 99.3% and similar to 71.2.L.h(-1).m(-2).psi(-1) at 13 mL volume fed, respectively, indicating that electrospun nanofiber membranes might be highly promising for microfiltration applications (particularly water purification). (C) 2017 Elsevier Ltd. All rights reserved.