Patent ID: 7691273

Claim:
A method for clarifying a sludge, comprising the steps of: recovering a discharged waste sludge; separating the discharged waste sludge into a solids fraction and a liquid fraction in a solid-liquid separation unit; recovering the liquid fraction from the solid-liquid separation unit; passing the recovered liquid fraction through a first filtration apparatus to obtain a first filtrate and a first solids residue; recovering the first filtrate from the first filtration apparatus; simultaneously ozonizing the first filtrate and irradiating the first filtrate directly with a specific ray to obtain a first treated liquid; recovering the first treated liquid; passing the first treated liquid through a second filtration apparatus to obtain a second filtrate and a second solids residue; recovering the second filtrate from the second filtration apparatus; simultaneously ozonizing the second filtrate and irradiating the second filtrate directly with the specific ray to obtain a second treated liquid; recovering the second treated liquid; and passing the second treated liquid through a third filtration apparatus to obtain a product liquid.