| 摘要 |
PROBLEM TO BE SOLVED: To provide a biological purifying and circulating system tray capable of rapidly and inexpensively treating sewage and capable of keeping a discoloration effect even in the presence of nitrous acid. SOLUTION: In the biological purifying and circulating system tray 1, the nitrous acid type nitrification of ammonia is performed in a filter tank 7 and denitrification is performed in a biological treatment tank 6. Further, a pH sensor 30 is provided in the filter tank 7 and a pH control device 50 is controlled so that nitrous acid type nitrification is performed in the filter tank 7 on the basis of the detection value of the pH sensor 30 to adjust the pH of sludge in the filter tank 7. Accordingly, the nitrous acid type nitrification can be always kept in the filter tank 7. Further, since the amount of oxygen in the filter tank 7 is reduced as compared with a conventional nitric acid type nitrification and denitrification method in a nitrous acid type nitrification and denitrification method, the power cost of a blower 26 can be reduced. Further, since it is unnecessary to convert ammonia to nitric acid in the nitrous acid type nitrification and denitrification method, ammonia in sewage can be rapidly treated. COPYRIGHT: (C)2006,JPO&NCIPI
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