One of the most practiced ways of handling sludge before dewatering in the Netherlands is anaerobic digestion (AD) since it reduces the offensive features of sludge such as odor and pathogens. AD provides a great opportunity to recover resources from the sludge such as biogas and it reduces the amount of sludge cake to be disposed of. The effect of AD on dewaterability was reviewed in the literature. However, in the literature, there are discrepancies in findings regarding the effect of AD on the dewaterability of sludge. Also, most of the studies evaluated dewaterability with capillary suction time (CST) and specific resistance to filtration (SRF) which, however, can not provide any information about the final results of full-scale dewatering in a quantitative way. This study aimed to examine the effect of VS removal by applying AD with different solid retention times (SRTs) in a cascade system configuration (the Ephyra® developed by Royal HaskoningDHV) on the dewaterability of the sludge (with thermal pre-treatment and without) in a quantitative way. To evaluate the dewaterability, two indexes were used which are the dry solid (DS) concentration of the dried cake (%) and the required polymer (PE) dosage (g active PE/kg total solids (TS)). Dewatering of the sludge was done by the Mareco mini filter press and a developed laboratory-scale centrifugation method which had comparable results to the full-scale situation. The sludge (undigested and digested) was characterized with different parameters such as total solids (TS), volatile solids (VS), extracellular polymeric substances (EPS), the net surface charge (zeta potential), and particle size distribution. The principal component analysis was used to evaluate the correlations between these parameters and the change in dewaterability and which one has more effect. The DS concentration of the sludge cake for digested thermally (THP) pre-treated sludge was 16% with Mareco mini filter press and 31% with the centrifugation method which showed the filter press method ...