This works deals with the best practice to operate batch membrane processes in presence of fouling. The examined case is the purification of washing olive wastewater. Firstly, previous results obtained on the same reference pilot plant are reported. The critical fluxes for both the membrane operations, that is ultrafiltration and nanofiltration in series, were determined with reference to different pollutant concentrations. It is so possible to derive the prediction equations from the best fitting of the experimental results. Then, the best strategy to fix the operating permeate flux rate is briefly discussed. A permeate flux around the predicted value of the critical flux at the end of the specific membrane batch process should be adopted in order to assure the recovery target minimizing membrane fouling. Finally, test runs were performed in order to validate the proposed methodology. (C) 2007 Elsevier B.V. All rights reserved.