In this study, olive mill wastewater (OMW) treatment by membrane operations was conducted to achieve the quality to recirculate the final effluent to the manufacture process or at least to the olives washing machines to finally close the loop. An efficient and novel pretreatment method for the OMW was performed to preserve the membranes from the deleterious fouling phenomena commonly encountered in all membrane facilities. This pretreatment consisted of Fenton-like advanced oxidation, flocculation-sedimentation and filtration through olive stones subsequently. One nanofiltration (NF) and two rather different reverse osmosis (RO) polymeric membranes were tested for the ulterior OMW purification. Upon the adopted strategy, near-zero fouling occurred on the NF membrane. Also, the composite RO membrane suffered minimum flux decay which rapidly reached a plateau. This was not the case of the asymmetric RO membrane, which yielded higher initial but not sustainable productivity. Both RO membranes provided COD and conductivity values in the permeate stream below standards for reuse in the production process (COD <5 mg O-2/L and conductivity <2.5 mS/cm, respectively). Moreover, high and stable flow ensured by NF after the adopted pretreatment pin-point it as a suitable pre-step for improving the final purification of OMW by RO membranes. (C) 2012 Elsevier B.V. All rights reserved.