The aims of this work are to construct a pilot scale purification set-up using membrane process for Tehran Oil Refining Company desalter plant wastewater. The investigation was shown that the high amount of impurities in the feed was the main reason of low permeation flux. The nano-porous membrane-powdered activated carbon (NPM-PAC) was employed to settle this problem. Results demonstrated NPM alone was ineffective in removing TSS, COD, and TOC. In the NPM process the removal of COD and TOC are around 62.5 and 75.1%, respectively, and the steady permeation flux (SPF) is around 78.7 L/(m(2) h). Optimum PAC dosage, which leads to less deposit layer with high porosity on the membrane surface, could increase permeation flux up to 133.8 L/(m(2) h), the removal of COD and TOC, 78.1% and 90.4%, respectively, and also decreased steady fouling resistance (SFR) around 46.1%. Hermia's models were employed to investigate mechanism of preventing membrane fouling. After coagulation, the kinetic constants, K-b, K-i, K-s, and K-c, showed lower amounts when NPM filtration used alone. Thus, a NPM-PAC hybrid membrane system has the potential to be an effective method to improve NPM removal efficiency in high percentages as well as to improve membrane fouling and permeation flux in desalter plant. Crown Copyright (C) 2012 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved.