A mixt. of sewage sludge and water treatment sludge in the ratio 1:0.3 by mass was used as a substrate in mesophilic MeH fermentation carried out at 35 degrees C. Three series of tests were carried out, differing in the sludge disintegration process: (i) thermal at 55 degrees C and ultrasonic; (ii) thermal at 55 degrees C and thermal at 70 degrees C and (iii) thermal at 55 degrees C and mech. 16,000 rpm. The effectiveness of the fermentation process was detd. using the indicators of biochem. MeH potential (BMP) and activity (AMB). The highest rates of BMP and AMB were obtained for sludges mixed and thermal disintegrated at 55 degrees C.