This work investigates the application of Fenton process to the treatment of a highly polluted industrial wastewater resulting from the pipeline cleaning in a power plant. This effluent is characterized by a high chemical oxygen demand (COD > 40 g/L), low biodegradability and quite a high iron concentration (around 3 g/L) this coming from pipeline corrosion. The effect of the initial reaction temperature (between 50 and 90 degrees C) and the way of feeding H2O2 on the mineralization percentage and the efficiency of H2O2 consumption has been analyzed. With the stoichiometric amount of H2O2 relative to initial COD, fed in continuous mode, more than 90% COD reduction was achieved at 90 degrees C. That was accompanied by a dramatic improvement of the biodegradability. Thus, a combined treatment based on semicontinuous high-temperature Fenton oxidation (SHTF) and conventional aerobic biological treatment would allow fulfilling the COD and ecotoxicity regional limits for industrial wastewaters into de municipal sewer system. For the sake of comparison, catalytic wet air oxidation was also tested with poor results (less than 30% COD removal at 140 degrees C and 8 atm oxygen pressure). (c) 2013 Elsevier B.V. All rights reserved.