Sanitary landfill leachate resulting from the rainwater percolation through the landfill layers and waste material decomposition is a complex mixture of high-strength organic and inorganic compounds which constitutes serious environmental problems. In this study, different heterogeneous (TiO(2)/UV, TiO(2)/H(2)O(2)/UV) and homogenous (H(2)O(2)/UV, Fe(2+)/H(2)O(2)/UV) photocatalytic processes were investigated as an alternative for the treatment of a mature landfill leachate. The addition of H(2)O(2) to TiO(2)/UV system increased the reduction of the aromatic compounds from 15% to 61%, although mineralization was almost the same. The DOC and aromatic content abatement is similar for the H(2)O(2)/UV and TiO(2)/H(2)O(2)/UV processes, although the H(2)O(2) consumption is three times higher in the H(2)O(2)/UV system. The low efficiency of TiO(2)/H(2)O(2)/UV system is presumably due to the alkaline leachate solution, for which the H(2)O(2) becomes highly unstable and self-decomposition of H(2)O(2) occurs. The efficiency of the TiO(2)/H(2)O(2)/UV system increased 10 times after a preliminary pH correction to 4. The photo-Fenton process is much more efficient than heterogeneous (TiO(2), TiO(2)/H(2)O(2)/UV) or homogeneous (H(2)O(2)/UV) photocatalysis, showing an initial reaction rate more than 20 times higher, and leading to almost complete mineralization of the wastewater. However, when compared with TiO(2)/H(2)O(2)/UV with acidification, the photo-Fenton reaction is only two times faster. The optimal initial iron dose for the photo-Fenton treatment of the leachate is 60 mg Fe(2+) L(-1), which is in agreement with path length of 5 cm in the photoreactor. The kinetic behaviour of the process (60 mg Fe(2+) L(-1)) comprises a slow initial reaction, followed by a first-order kinetics (k = 0.020 L kJ(UV)(-1), r(0) = 12.5 mg kJ(UV)(-1)), with H(2)O(2) consumption rate of k(H2O2) = 3.0 mmol H(2)O(2) kJ(UV)(-1), and finally, the third reaction period, characterized by a lower DOC degradation and H(2)O(2) consumption until the end of the experiment, presumably due to the formation of low-molecular-weight carboxylic groups. A total of 306 mM of H(2)O(2) was consumed for achieving 86% mineralization (DOC(final) = 134 mg L(-1)) and 94% aromatic content reduction after 110 kJ(UV) L(-1), using an initial iron concentration of 60 mg Fe(2+) L(-1). (C) 2010 Elsevier Ltd. All rights reserved.