This paper describes the combination of a dialysis membrane and a photochemical reactor into a membrane photoreactor (MPR) to mineralise organic compounds. With this process, a pollutant model (2,4-dihydroxy benzoic acid) is mineralised from turbid waters in the photoreactor by using V-UV (vacuum ultra violet) irradiation (172 nm). This "advanced oxidation processes" produces high concentrations of hydroxyl radicals and is a good method to mineralise organic compounds. A model based on diffusion through the membrane and first order reaction in the reactor is in good agreement with the experimental data, in a wide range of operating conditions. (c) 2005 Elsevier B.V. All rights reserved.