Cost effective sludge management after industrial wastewater and hazardous waste treatment processes requires effective dewatering applications. Difficulty in dewatering of sludge arises from extracellular polymeric substances (EPS) which are known to hold large amounts of water. On the other hand, EPS quantity and quality are directly related to carbon composition of the waste. In this study we investigated the changes in dewatering properties of laboratory grown activated sludge samples fed with substrates having different biodegradability. To investigate the effect of change in carbon source and substrate composition on Specific Resistance to Filtration (SRF) two carbon sources, phenol and glucose were selected. Our results indicate that dewaterability of acclimated mixed cultures were different depending on the concentration of different carbon sources. As the content of easily degradable substrate in wastewater is decreased, the SRF values also decreased producing easier to dewater sludges.