| 摘要 |
PURPOSE:To effectively utilize the BOD of feed water for denitrification to the max. extent by dividing the denitrification tank of a circulation system to at least to parts, making denitrification by using the BOD of the feed water on the upper stream side and making denitrification by injection of an org. carbon source on the down stream side. CONSTITUTION:A nitrification tank 3 which nitrifies the nitrogen compd. in sewage under aerobic conditions and the denitrification tank 1 which reduces the nitrate nitrogen or nitrite nitrogen in the nitrified liquid obtd. by the nitrificaion to gaseous nitrogen by utilizing the org. carbon source in the sewage flowing therein and the org. carbon source supplied from the outside are provided. The denitrification tank 1 is divided into at least two parts. The inflow sewage and the nitrate nitrogen and nitrite nitrogen in the nitrified liquid are mixed in the tank 1-1 on the upper stream side thereof. The org. carbon source (e.g., methanol) is supplied from the outside to the 2nd divided tank 1-2 and afterward. The concn. of the org. carbon source supplied from the outside is measured in the denitrified liquid flowing out of the denitrification tank and the supply rate of the org. carbon source to be supplied from the outside is so controlled that said value attains the prescribed concn.
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