Abstract: The device of the present invention removes liquid from sludges, such as water from an industrial pretreatment sludge. The device includes a chamber with an inlet for introducing the sludge to be dewatered into the chamber. The device includes a hydraulically driven reciprocating piston which functions as a containment wall at one end of the chamber and as a means to subject the sludge to mechanical pressure for dewatering, with seals sufficient to contain the sludge within the chamber during operation. The device includes a reciprocating end cap which functions as a containment wall at the end of the chamber opposite the reciprocating piston. The end cap includes a micro porous membrane filter assembly for retention of solids, support structure for the filter, a void area for vacuum pump evacuation to assist in dewatering, and an outlet for the liquid displaced from the sludge.