JPH0232925B

PURPOSE:To effectively perform dehydration and to efficiently perform high pressurizing dehydration, by making the inner perforated pipe of a filter material apparatus freely accessible to the outer perforated pipe thereof by using a dehydrating plunger as a guide. CONSTITUTION:A dehydration pipe 7 consisting of an outer perforated pipe 3 and an inner perforated pipe 4 between which a filter material 5 is interposed in successively filled with a raw sludge liquid and press dehydration and the extrusion of dehydrated earth and sand are intermittently performed by the before-and-behind advance and retraction movement of a dehydrating plunger 13. Because of this, dehydration can be effectively performed and high pressure dehydration is efficiently performed. Because the inner perforated pipe 4 having the filter material 5 mounted to the outer periphery thereof in a freely detachable manner is made freely accessible to the outer perforated pipe 3 by guiding the dehydrating plunger 13, the replacement of the filter material 5 with a new one at the time of the generation of clogging and cleaning work by the injection of a fluid can be rationally, rapidly and easily performed by drawing the inner perforated pipe 4 to the outside from the outer perforated pipe 3.