| 摘要 |
<p>PROBLEM TO BE SOLVED: To efficiently and stably remove nitrogen in organic material-containing water when the water is biologically treated by a nitrification and endogenous denitrification method, by bringing a humic substance into contact with active sludge in an aerobic tank and in an oxygen-free tank. SOLUTION: A nitrified liquid generated in an aerobic tank 8 flows into an oxygen- free tank 8, wherein the oxygen-free tank 8 denitrifies the nitrified liquid by a biological treatment using a microorganism or the like. A denitrified sludge mixed liquor which has been denitrified in the oxygen-free tank 8 flows into a reaeration tank 12. In the reaeration tank 12, the denitrified sludge mixed liquor flown from the oxygen-free tank 8 is made to be an aerobic state to prevent the denitrified active sludge from rising to the surface of a sedimentation tank. Herein, a means for supplying a humic substance to the oxygen-free tank 6 and the aerobic tank is provided. As for the means for supplying the humic substance, when a powdery humic substance is used, a feeder or the like, which adds the humic substance as a powder or its suspension into the tanks, can be exemplified. When a pellet-like humic substance is used, a means which puts the pellets of the humic substance in a wire net basket or the like and immerses them into water in the tanks can be exemplified.</p> |
