In this work, removal of naphthenic acid (NA) using micellar enhanced ultrafiltration has been reported using 10,000 cutoff polyethersulfone membrane. Sodium dodecyl sulfate (SDS) has been used as surfactant. Effects of various parameters like pH, surfactant concentration, transmembrane pressure drop, cross flow velocity and electrolyte concentration on the permeate flux and permeate quality have been investigated in detail. In order to increase the permeate flux, potential of external electric field has also been explored. The electric field has been applied in two modes. In mode 1, a step-wise electric field is applied, so that the operating field strength across the membrane increases stepwise. In mode 2, a fixed electric field is applied throughout the experiment. In second mode of operation, about 24% flux enhancement is achieved compared to 14% in mode 1. (c) 2012 Elsevier B.V. All rights reserved.