Abstract: An apparatus for thickening liquids or thin sludges by water extraction, having a bottom, a tub having an underside, stands supporting the tub on the bottom, a ripening time chamber for receiving the liquids or thin sludges, first devices for admixing a polyelectrolyte for flocculation in the ripening time chamber, a conveyor belt for further dewatering the liquids or thin sludges, and second devices for delivering liquid extracted from the conveyor belt and thick sludge discharges. At least the conveyor belt, the ripening time chamber and the second devices are accommodated in the tub, which thus acts as a frame and a lateral boundary for the conveyor belt, the ripening time chamber and the second devices. All connections required for operation are disposed on the underside of the tub, and the underside of the tub is spaced above the bottom by the stands.