This paper provides an analysis of different measurements and derived parameters that may be used to characterize drainability and filterability dynamics. To better simulate the phenomena of gravity drainage and expression dewatering, specific devices and procedures were used in bench-scale conditioning and dewatering experiments. The setup included a plow simulator kit for drainage simulation and a mechanical dewatering unit, namely, the Crown Press (TM), which simulates full-scale belt filter press dewatering. The effects of enzyme product additions prior to polymer conditioning of biosolids samples were investigated. The results showed that enzyme additions enhanced the drainability of the biosolids samples and this positively affected filterability of the samples in the press unit. According to these results, enzyme product addition for biosolids samples with polymer conditioning seems a promising new method of enhancing the performance of mechanical dewatering units in the future. (c) 2004 Elsevier Ltd. All rights reserved.