| 摘要 |
Provided is a process by which recycled water of excellent quality can be produced from wastewater at low cost without using a large amount of ozone. The process for producing recycled water comprises: bringing ozone into contact with raw water, such as water resulting from a sewage treatment, using, e.g., an ozone contact column (2) to heighten the coagulability of a solid matter contained in the raw water; thereafter injecting a coagulant with a coagulant-injecting pump (6) to coagulate the solid matter; and filtering the resultant mixture through a separation membrane (8). The raw water before the separation membrane is examined for residual ozone concentration with a dissolved-ozone meter (5). When the quality of the raw water has deteriorated and this has resulted in an ozone demand exceeding the capacity of the ozone generator and hence in a residual ozone concentration lower than a given value, then the amount of the coagulant to be injected is increased. In a region where the ozone demand does not exceed the capacity of the ozone generator, the amount of the coagulant to be added is increased or reduced according to the amount of ozone introduced or the amount of ozone consumed. |
