| 摘要 |
<p>PURPOSE:To efficiently discharge and remove the scum floating on a water surface by lowering the number of revolutions of the screw of an aeration device which supplies the air into sewage by the rotation thereof for a prescribed period of time to generate gentle water flow so as to move the scum toward a skimmer. CONSTITUTION:The sewage is admitted into a treatment tank 1 up to a water level HWL and after the biological treatment by aeration is finished, the aeration device 5 is stopped to allow sludge to settle. The skimmer 3 for discharging the scum is rotated to adjust a scum discharge port 3a for a required period of time until said port is positioned below the water surface at the point of the time when the sludge boundary lowers to the part lower than the front end of a screw 53 of the aeration device and down to at least about 1m below the water level in this settling stage. The number of revolutions of the screw of the aeration device is simultaneously lowered and the aeration device 5 is run at this lowered speed to generate the water flow of a weak velocity of flow toward the skimmer 3. The scum floating on the water surface is moved by this water flow toward the discharge port 3a of the skimmer 3 and the scum 10 is discharged from this discharge port 3a to the outside of the treatment tank 1.</p> |
