| 摘要 |
PROBLEM TO BE SOLVED: To provide a nitrifying soln. circulating type waste water treatment apparatus and method capable of performing nitrification and denitrification reaction efficiently and capable of also preventing the contamination of a membrane surface. SOLUTION: A waste water treatment apparatus is equipped with a denitrification tank 1 receiving waste water containing org. nitrogen to decompose nitrate nitrogen in waste water by denitrifying bacteria, a nitrification tank 2 oxidizing ammonia nitrogen in waste water to nitrate nitrogen by nitrifying bacteria, a pump 6 for returning the treated soln. in the nitrification tank to the denitrification tank to circulate the same, an immersion flat membrane device 3 filtering a clarified component from the treated soln. in the nitrification tank to discharge the same out of the tank, an air diffusion pipe 4 supplying air to the immersion flat membrane device 3, an aeration system consisting of a blower 7 and an air venting valve 8, a dissolved oxygen meter 5 for measuring the amt. of dissolved oxygen in the nitrification tank 2 and a control device 10 adjusting aeration air quantity so as to hold the amt. of dissolved oxygen in the nitrication tank to a predetermined range while ensuring air quantity necessary for washing the membrane surface of the immersion flat membrane device 3.
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