| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a nitrogen-containing drainage treating method capable of keeping denitrifying efficiency high and capable of keeping a nitrogen content in treated liquid low in the case where the modified sludge obtained by modifying sludge to an easily biodegradable substance is supplied to a denitrifying stage as a substrate in a biological nitrifying and denitrifying method. SOLUTION: In the method in which an organic substance is decomposed by aerating organic or ammonical nitrogen-containing drain 11 at an organic substance decomposition tank 1, nitrified biologically at a nitrifying tank 2, denitrified at a denitrifying tank 3, subjected to solid-liquid separation at a solid-liquid separation tank 5 after reaeration at a reaeration tank 4, a part of separated sludge is returned to the nitrifying tank 2 and the denitrifying tank 3 and the other part is modified to an easily biodegradable substance at an ozone treating tank 6 and supplied to the denitrifying tank 3 as a substrate to perform the denitrification, a return sludge quantity to the nitrifying tank 2 and/or volumes of the denitrifying tank 3 and the reaeration tank 4 is changed so that the nitrifying activity of the sludge in the nitrifying tank may be kept >=0.05 g-N/g-VSS/d and/or the dissolved oxygen concentration in the nitrifying tank may be kept >=2 mg/L.</p> |
