A prototype electrical cross-flow filtration system (ECFF) was designed and used to improve the separation of nano-sized particles from water, Model colloids, e.g., gamma-Al2O3 and SiO2, and naturally occurring colloidal particles collected from well waters in the state of New Jersey were used to evaluate the performance of the ECFF module. Results indicated that the prototype ECFF unit functions properly without clogging and there is no need to backwash the membrane, under the experimental conditions of this Study. It is possible to effectively separate the nano-sized colloidal particles by adjusting the electrostatic field strength. The removal efficiency increased with the applied electrostatic field strength. A simplified transport model was utilized to assess the effect of pertinent parameters, such as surface charge, filtration rate, and applied electric field strength, on the performance of the filter. The model results agreed well with those obtained experimentally. (c) 2007 Elsevier B.V. All rights reserved.