BACKGROUND: The presence of pharmaceutical residues in the aquatic environment is an emerging issue due to their uncontrolled release and accumulation in the environment that may affect living organisms, ecosystems and public health. As a result, efforts are being made to develop methods to inactivate or eliminate this class of substance in the environment. RESULTS: The homogeneous photocatalytic degradation of sulfamethazine (SMT), a sulfanilamide drug, has been investigated in aqueous solutions using artificial and solar illumination. The effects of initial concentration of H2O2 (10-400 mg L-1), Fe3+ (3.5-28 mg L-1), SMT (10-40 mg L-1), as well as temperature (280-323 K) on mineralization rates were evaluated in a bench-scale Pyrex reactor for the photo-Fenton/UV-A and photo-Fenton/Vis processes. SMT degradation was accompanied by the release of inorganic nitrogen and sulphate ions. Experiments under natural sunlight conditions were performed in a pilot-scale, fountain reactor at light intensities between 0.49 and 2.83 mW cm(-2). CONCLUSIONS: An increase in the level of the parameters had a positive effect, with photo-Fenton/UV-A (at 0.94 x 10(-4) einstein L-1 min(-1) light flux provided by a 9 W lamp at 366 nm maximum response) being more effective than photo-Fenton/Vis (at 0.88 x 10(-4) einstein L-1 min(-1) also provided by a 9 W lamp at 440 nm maximum response). Illumination for 120 min in the case of the pilot-scale reactor at 2 mW cm(-2) intensity led to more than 70% mineralization of 20 mg L-1 SMT, thus showing that process scale-up is feasible. (C) 2013 Society of Chemical Industry