Abstract: A rotary filter for filtering water out of water containing raw material such as fish guts and muds including a screw drum having a number of filtering holes formed therein and a screw having a shaft and a spiral vane secured to the outer surface of the shaft, in which the screen drum is arranged rotatably, the screw is arranged within the screen drum rotatably relative to the screen drum, and the screen drum and the screw are rotated by means of separate driving sources independently from each other. A period of time during which the water containing raw material is remained within the screen drum can be adjusted at will regardless of the rotation speed of the screen drum. Therefore, the screen drum can be rotated at a high speed while the raw material can remained within the screen drum for a long time period, so that the water filtering efficiency can be increased.

Abstract: In the Invention is directed to a method and apparatus for dewatering sludge wastes discharged from a factory such as pulp factory. Sludge wastes are first dewatered by a preliminary dewatering device such as a pre-thickener of a rotary screen type, sludge discharged from the preliminary dewatering device is then supplied to a main dewatering device such as a screw press. Waste liquid discharged from the preliminary and main dewatering devices are supplied to an agglutinating reaction tank together with a macromolecular agglutinating reagent and agglutinated substances in the agglutinating reaction tank are treated by the main dewatering device. The agglutinated substances formed on the bottom surface of the agglutinating reaction tank can be treated by a second main dewatering device other than the main dewatering device. A necessary amount of the macromolecular agglutinating reagent supplied to the agglutinating reaction tank can be reduced without deteriorating the dewatering efficiency.

Abstract: In a continuous press of a screw blade type, a driving shaft is rotatably secured to a frame by means of thrust bearings at both ends of the driving shaft, a screw drum having an increasing diameter towards center is disposed around the driving shaft to rotate therewith, a pair of screw blades are helically arranged around the screw drum symmetrically with respect to the center of screw drum, and an outer drum having a number of small filtering holes is arranged around the screw blades. A pair of inlets for introducing raw materials to be pressed are provided at both ends of the outer drum and an outlet from which the pressed raw materials are discharged is also provided in the outer drum at its center. At the outlet a pair of cone-shaped plates are arranged movably in an axial direction of the press and these plates are resiliently pressed towards each other. The pressure applied to the cake is automatically maintained constant due to the axial movement of the plates.