| 摘要 |
PROBLEM TO BE SOLVED: To efficiently remove fluorine and nitrogen. SOLUTION: After fluorine is removed by utilizing calcium in a fluorine removing section 10, a drain containing nitrogen is introduced into a fore stage USB denitrification tank 12. In the fore stage USB denitrification tank 12, denitrification treatment is carried out by utilizing the nitric acid from a fixed bed nitrification tank 14 of a post stage and methanol to be added and nitrogen is removed and the calcium is removed as calcium carbonate. Thereupon, the calcium concentration in the biological denitrification treatment of the fixed bed nitrification tank 14 of the post stage or the like is lowered and the efficient treatment can be carried out by making the microorganism concentration therein sufficiently highly. More preferably, the occurrence of the clogging or the like in the fixed bed nitrification tank 14 can be effectively prevented. |
