Oxidative disintegration of municipal waste activated sludge (WAS) using conventional Fenton (Fe2+ + H2O2, CFP) and Fenton type (Fe-0 + H2O2, FTP) processes was investigated and compared in terms of the efficiency of sludge disintegration and enhancement of anaerobic biodegradability. The influences of different operational variables namely sludge pH, initial concentration of Fe2+ or Fe-0, and H2O2 were studied in detail. The optimum conditions have been found as catalyst iron dosage = 4 g/kg TS, H2O2 dosage = 40 g/kg TS and pH = 3 within 1 h oxidation period for both CFP and FTP. Kinetics studies were performed under optimal conditions. It was determined that the sludge disintegration was happened in two stages by both processes: rapid and subsequent slow disintegration stages and rapid sludge disintegration stage can be described by a zero-order kinetic model. The effects of oxidative sludge disintegration under the optimum conditions on anaerobic digestion were experienced with biochemical methane potential (BMP) assay in batch anaerobic reactors. Total methane production in the CFP and FTP pre-treated reactors increased by 26.9% and 38.0%, relative to the untreated reactor (digested the raw WAS). Furthermore, the total chemical oxygen demand reductions in the pre-treated reactors were improved as well. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.