Process and system for anaerobic treatment of biochemical waste
AssigneeHitachi, Ltd.
InventorsMasahiko Ishida, Ryooichi Haga, Youji Odawara
Life of this patent
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Abstract
In a system for treatment of biochemical waste such as activated sludges, the waste is subjected to anaerobic stabilization processes, which include two phases of an acid fermentation and a methane fermentation effected in separate reactors. The waste after the acid fermentation is then separated into a liquid effluent for the methane fermentation and a waste sludge. The waste sludge which may cause secondary environmental pollution is re-treated within the anaerobic stabilization processes without withdrawing from the system.
Claims22
A process for anaerobic digestion of waste containing relatively high molecular weight organic materials comprising;
- a first step of anaerobically digesting the waste by bacterial acid formers in an acid fermentation reactor to convert the high molecular weight organic materials into low molecular weight organic materials and further to convert the low molecular weight organic materials into volatile organic acids,
- a second step of separating the waste in said first step into a first portion containing volatile organic acids and a second portion containing undigested residue and cells of the acid formers,
- a third step of anaerobically digesting the first portion by bacterial methane formers in a methane fermentation reactor separate from said acid fermentation reactor to generate methane and carbon dioxide gas,
- a fourth step of separating the waste in said third step into a third portion containing digested sludge and effluent and a fourth portion containing cells of methane formers, and
- a fifth step of partially recycling the second portion separated in said second step in order to digest within at least one of the reactors effecting the anaerobic digestion steps.
A system for anaerobic digestion of waste containing relatively high molecular weight organic materials comprising;
- an acid reactor in which the waste is anaerobically digested by bacterial acid formers to convert the high molecular weight organic materials and further to convert the low molecular weight organic materials into volatile organic acid,
- a first separator in which the waste in said acid reactor is separated into a first portion containing volatile organic acids and a second portion containing undigested residues and cells of the acid formers,
- a methane reactor separate from the acid reactor for anaerobically digesting the first portion by bacterial methane formers to generate methane and carbon dioxide gas,
- a second separator in which the waste in said methane reactor is separated into a third portion containing digested sludge and effluent and a fourth portion containing cells of the methane formers, and
- means for partially recycling the second portion separated in said first separator in order to digest the recycled second portion within the anaerobic digesting system.
Dependencies are inferred from the claim text.