Supercritical water oxidation (SCWO) is an environmentally friendly technology for the treatment of industrial waste-waters and sludges. However, the salt precipitation and corrosion presents in this process accelerate the deterioration of the reactor. To avoid reactor plugging and reactor wall corrosion transpiring wall reactors (TWR) have been developed to provide a technical alternative. A TWR has been developed at the University of Valladolid. Extensive experiments have been done in order to find out how the TOC removal and temperature profile are affected by the operational parameters. In addition, tests have been performed to identify the mildest operational conditions possible, keeping in mind the durability of the materials, energy savings, the reactor productivity and of course the TOC removal. The parameters studied were feed flow, feed temperature, transpiring flow, transpiring flow temperature, air inlet temperature and the combined influence of fuel concentration in the feed and feed temperature. It was determined that the optimum working feed flow for the reactor is between 16 and 20 kg/h. The feed inlet temperature was found to have a direct influence on TOC removal, for as when the inlet temperature decreased TOC removal decreased as well. The transpiring flow, transpiring flow temperature and air temperature had a negligible effect on TOC removal. Thus, a test was carried out working with 20 kg/h, without preheating air or transpiring flow in order to confirm that heat supplied by feed preheating could be replaced by higher fuel concentrations. (C) 2006 Elsevier B.V. All rights reserved.