PURPOSE: To improve the solid-liquid sepn. of digested sludge within the range of a digestion process by digesting the initial settling basin sludge produced in sewage treatment facilities anaerobically then mixing the sludge with excess activated sludge and subjecting the sludge to solid-liquid sepn.
CONSTITUTION: The initial settling basin sludge produced in sewage treatment facilites are digested anaerobically until 60W75% the org. materials thereof are decomposed. Thereafter, the sludge is mixed with excess sludge and the mixture is subjected to solid-liquid sepn. A dehydration treatment and a combination of a concn. treatment and the dehydration treatment are suitable as the operations for solid-liquid sepn. A settling method, a floating method, and centrifugal concn. can be utilized for the concn. treatment and mechanical dehydration, etc. for the dehydration treatment. This method may cause a decrease in the volume of gases generated as compared to the prior art by as much as the digestion of the excess activated sludge is omitted, but the flocculating properties that the excess activated sludge possesses are acted effectively in the stage of the solid- liquid sepn. by mixing the excess activated sludge as it is with the digested sludge of the initial settling basin sludge.
MATSUO YOSHITAKA
ENDOU KANEROU
