| 摘要 |
PURPOSE:To discharge waste water to sewerage or a public water area by treating waste water low in BOD using an ultrafiltration membrane, a precise filter membrane or both of them and discharging filtrate set to a predetermined ratio or more in the amt. of waste water and subjecting conc. water set to the predetermined ratio or less in the amt. of waste water to biological treatment to discharge treated water. CONSTITUTION:Low conc. waste water 1 of which the biochemical oxygen command (BOD) is 5-40 mg/l is treated in a filter membrane device 12 using an ultrafiltration membrane, a precise filter membrane or both filter membranes, and the filtrate is set to 1/2 or more the amt. of waste water and conc. water 3 is set to 1/2 or less the amt. of waste water. The filtrate is discharged and the conc. water 3 is subjected to biological treatment by a biological treatment apparatus 15 to discharge biologically treated water. In this treatment of waste water, waste water 2 of which the concn. of BOD is higher than that of the low conc. waste water 1 and the conc. water 3 of the low conc. waste water 1 can be simultaneously treated. Since the high conc. waste water is high in BOD, it can be biologically treated as it is and can be directly mixed with the conc. water of the low conc. waste water 1 to be subjected to biological treatment. |
