Abstract: Method of continuous treatment and purification of biologically decomposable waste and liquid in a rotatably elongated perforated cylinder longitudinally divided into a dewatering and wet composting unit, a central dewatering unit and a dry composting unit. The perforated cylinder is surrounded by an envelope for collecting liquid wastes which are treated by oxygenated filter units in communication with the envelope structure. The device also includes a hollow perforated shaft within the cylinder for supplying oxygen to the interior of the cylinder and for rotating the cylinder.