Anaerobic treatment method and anaerobic treatment apparatus for organic wastewater

摘要

PROBLEM TO BE SOLVED: To provide, by targeting an anaerobic treatment method of an organic effluent including C1 compounds, a novel anaerobic treatment method of an organic effluent capable of adjusting the pH inside a methane fermentation tank within a pH range suitable for methane fermentation without requiring the enlargement of the reaction tank volume.SOLUTION: The proposed anaerobic treatment method of an organic effluent comprises: an agitated methane fermentation step of executing the methane fermentation of an organic effluent within a mixing tank in an agitated state; a finish methane fermentation step of executing, within a fermentation tank of a plug flow method in an agitation-free state, the methane fermentation of a sludge-containing agitated methane-fermented treated water discharged from the agitated methane fermentation step; a sludge separation step of separating and recovering the sludge and methane-fermented treated water from the sludge-containing finish-methane-fermented treated water discharged from the finish methane fermentation step; and a sludge return step of returning, to the agitated methane fermentation step or finish methane fermentation step, some or all of the sludge separated and recovered at the sludge separation step.