Abstract: An apparatus and method of creating circulation of a mixture containing solid waste and water such as sludge and separating these components. The apparatus includes a tank housing, in inverted funnel-like element within the housing for constricting upward flow of a gasborne mixture, a trapped gas pocket for degassing the gasborne mixture, a containment element interposed between an effluent weir and the inverted funnel for directing downward and outward flow of the degassed mixture, and a deflecting surface in the path of the downward flow to promote settling of the solids from the degassed mixture and for allowing clarified water to rise within the containment element and the tank housing to reach the effluent weir. For aerobic treatment, a diffuser is arranged within the inverted funnel to supply air or gas to create upward flow of the gasborne mixture.