Patent ID: 7402247

Claim:
A method for treating and digesting organic wastes in a wastewater stream, comprising the steps of: dividing a wastewater stream containing organic wastes into a first wastewater influent stream and a second wastewater influent stream; mixing at least a portion of the first wastewater influent stream with an activated sludge biomass in a substantially aerobic digestion zone, wherein organic wastes in the first wastewater influent stream are digested by the activated sludge biomass; separating at least a portion of the first wastewater influent stream from activated sludge biomass in a first separation zone to recover activated sludge biomass therefrom and to provide a wastewater effluent stream; mixing at least a portion of the second wastewater influent stream with activated sludge biomass recovered from the aerobic digestion zone in a substantially anaerobic adsorption zone, wherein organic wastes in the second wastewater influent stream are adsorbed by the activated sludge biomass; separating at least a portion of the second wastewater influent stream from the activated sludge biomass therein in a second separation zone to recover activated sludge biomass therefrom and organic wastes adsorbed thereto from the anaerobic adsorption zone; recycling a substantially liquid wastewater stream from the second separation zone to the aerobic digestion zone; and digesting at least a portion of the activated sludge biomass and adsorbed organic wastes from the anaerobic adsorption zone under substantially anaerobic conditions in a plurality of successive substantially anaerobic digestion zones, wherein the organic wastes are progressively digested by a plurality of microbial species, so as to recover a combustible gas stream.