NOVELTY - An apparatus comprises a membrane bioreactor with module having several porous membranes and configured such that, in operation, a substrate comprising an activated sludge is contacted with outer surface of the membranes, and a treated water is removed from lumens of the membranes; and a biological sludge treatment vessel, where the biological sludge vessel is configured to operate in an anaerobic environment where a process fluid is digested.    USE - For treating influent stream comprising a digestible waste for removing biological solids (claimed).    ADVANTAGE - The membrane bioreactor process combined with advanced biological sludge digestion process provides significant improvements in sludge digestion by reducing the costs and resources required for disposing of digested sludge. The offline treatment vessel is used to solubilize the organic material by operating in a very low oxygen environment. Digested process fluid is transferred back to the membrane bioreactor. The processes and apparatus substantially reduce the production of waste sludge. The wastewater or biological sludge can be treated in a biologically optimal manner that facilitates simultaneous use of multiple biological processes, permitting the coexistence, in a single vessel, of multiple biological processes having inconsistent environmental requirements. Controlled, multiple biological environments can be treated in a single vessel without mixing, and control and maintain the relative proportions of each separate biological environment by non-turbulent adjustment of conditions. Waste can be processed in a single vessel through simultaneous use of aerobic, anoxic and anaerobic microorganisms. Gas can be quiescently moved into a single vessel, multiple-process environment to supply and/or remove nutrients and biological byproducts. Waste can be processed in a single vessel with multiple biological environments whose relative ratios are controlled to meet target oxidation-reduction potentials at at least one effluent points. Inert substances can be removed from recycled waste streams, where the substances have sizes similar to those of waste-digestive microorganisms, without depleting the stream of such microorganisms.    DETAILED DESCRIPTION - At least a portion of the digested process fluid is transferred to the membrane bioreactor, and where at least a portion of the substrate in the membrane is transferred to the biological sludge treatment vessel. The apparatus further comprises a hydrocarbon, where the hydrocarbon is positioned between the membrane bioreactor and the biological sludge treatment vessel, where the hydrocarbon is configured to remove inert materials in an outflow from the membrane bioreactor.