| 摘要 |
PURPOSE:To obtain separated liquid having sufficiently low SS concn. by separating solids from liquid in org. filthy water which has been treated with activated sludge with ultrafiltration membrane, guiding obtd. liquid permeated through the membrane to a coagulating tank, forming a mixture contg. coagulated flocs by adding an inorganic coagulating agent and separating solids from liquid in the mixture with a centrifuge. CONSTITUTION:Crude org. filthy water 21 is treated with activated sludge in a treating tank 22, and obtd. mixture 23 is transported to the ultrafiltration membrane 25, where it is separated into solid concentrated sludge 26 and permeated liquid 27. The permeated liquid 27 is led to a coagulating tank 28. Here, the inorganic coagulating agent 29 and an adjusting agent 30 are added to the permeated liquid 27, adjusting thus the chromaticity and COD of the permeated liquid 27 and forming also coagulated flocs. The liquid mixture 31 contg. the coagulated flocs is then led to the centrifuge 32, where the mixture is separated into solid concentrated sludge 33 and separated liquid 34. The concentrated sludge is returned to the treating tank 22 and the separated liquid 34 is discharged out of the system. The obtd. separated liquid 34 has sufficiently low SS concn. Preferred centrifuge 32 to be used is one capable of concentrating the concentrated sludge 33 to concd. liquid having 2-3% concn. |
