Abstract: An anaerobic apparatus for treating wastewater is disclosed. The treating apparatus comprises a reactor housing a media having a plurality of surfaces for receiving bacteria. The wastewater that is to be treated, is introduced into the bottom of the reactor and forced up over the surfaces of the media, whereby the bacteria on the surfaces of and in the voids of the media consume the organic materials in the wastewater by an anaerobic digestion process to produce methane and a biological sludge. The biological sludge is collected and stored in a bottom storage portion of the reactor, whereby further digestion occurs to condense the mass of such sludge. A first conduit array is disposed above the media for withdrawing the treated wastewater. A second conduit array is disposed in communication with the storage portion for withdrawing biological sludge from the reactor.