| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the equipment cost of an oxidation ditch (OD). SOLUTION: One cycle nitrification and denitrification treatment is performed by constitution simple as compared with a case using an impeller by enabling a process capable of inducing air through an air introducing pipe 1 by driving an underwater circulating pump 6 so as to bring the same into contact with discharged sewage to allow sewage to flow as a water stream mixed with air bubbles, a process capable of setting a predetermined range of a region on the downstream side of the air introducing pipe 7 of a circulating water channel 4 to an aerobic area and a process capable of setting the region from the aerobic region to the downstream air introducing pipe 7 to an anaerobic region. In addition, a valve 8 is provided in the air introducing pipe 7 and the underwater circulating pump 6 is driven while the valve 8 is opened to set the whole in the circulating water channel 4 to an aerobic state, and the underwater circulating pump 6 is driven and the valve 8 is closed to cut off the contact of discharged sewage with the atmosphere to set the whole in the circulating water channel 4 to an anaerobic state and the whole in the circulating water channel 4 is alternately changed over to the aerobic and anaerobic states. In this oxidation ditch (OD), a blower, an air diffusing plate and connection piping are dispensed with.</p> |
