| 摘要 |
PROBLEM TO BE SOLVED: To stably implement biological treatment without increasing the capacity of a biological treating vessel, to enhance the quality of treated water at a low rate of addition of an inorganic flocculating agent, to decrease the generating amt. of inorg. sludge and in addition, to allow the downsizing and cost reduction of, for example, a clean filter device, adsorption device, etc., in the post stage of a solid-liquid separator. SOLUTION: Part of the separating treated water of the solid-liquid separator 6 is returned between the biological treating vessel 3 and an intimate mixing vessel 5 or the intimate mixing vessel 5 through a separation treated water return line L20 and is mixed with a first liquid mixture, by which the MLSS concentration of the intimate mixing vessel 5 and the MLSS concentration flowing from the intimate mixing vessel 5 into the solid-liquid separator 6 are lowered without changing the MLSS concentration of the biological treating vessel 3 and the amount of the treated water (the amount of the discharge water) is made lower as compared to the case diluting water is added to the treated water. |
