The photocatalytic removal of colour of a synthetic textile effluent, using TiO2 suspensions under solar radiation, has been studied at pilot plant scale. A synthetic dye solution was prepared by a mix of six commercial textile dyes. A photochemical reactor of parallel CPC reflectors with UV-transparent tubular receivers was used. The study of photodegradation was carried out using the Taguchi's parameter design method. Following this methodology, the reaction was conducted under different flow conditions, pH and H2O2 concentrations. The results show that all dyes used in the experiences can be degraded successfully by photo-oxidation. The process shows a significant enhancement when it is carried out at high flows, alkaline media and high H2O2 Concentration. Colour removal from the effluent was reached at 55 min operating time. (c) 2005 Elsevier Ltd. All rights reserved.