| 摘要 |
<p>PROBLEM TO BE SOLVED: To make a device for the treatment of methanol as a hydrogen-donating material unnecessary and to decrease the running cost by separating raw water into treated water and concentrated water by membrane separation, introducing the concentrated water to a biological treating device for denitrification treatment, and injecting the required hydrogen-donating material while controlling the injection amt. SOLUTION: Raw water containing nitric acid is supplied to an electrodialysis device 2 to be separated into demineralized treated water and concentrated water. After pH of the concentrated water is controlled, the concentrated water is supplied to a biological treating device 3 and brought into contact with granules of denitrifying bacteria. In the biological treating device 3, methanol is injected as a hydrogen- donating material to convert nitric acid into nitrogen. Methanol by about 50 to 80% of the stoichiometric amt. of methanol required for denitrification is continuously injected through a first passage 12. The rest of methanol is injected through a second passage 13 while the oxidation-reduction potential of the concentrated water is controlled to about -100 to -200 mV. Thereby, as a whole, a proper amt. of methanol is injected to the biological treating device 3.</p> |
