| 摘要 |
<p>PURPOSE: To efficiently clean the filter bed with a small amt. of waste cleaning water by forming a floating filter medium with a granular body consisting of a material having a large sp.gr. difference from water and having a specified grain diameter by discharging water in the amt. of specified times the amt. of the packed filter medium from the lower part of the filter bed within a specified time. CONSTITUTION: The raw water 11 is supplied into a treating tank 1 from a raw water feed pipe 7 and passed upward through the void between the filter mediums 4a, and the solid, org. matter, etc., are biologically filtered and removed. The treated water 12 is passed through a filter medium blocking plate 10, moved into the upper part of the tank 1 and discharged from a treated water discharge groove 1a. When the floating filter medium 4a is cleaned, the raw water feed valve 13 of the feed pipe 7 is closed, and then a cleaning water discharge valve 9 is opened. The water in the amt. of about 0.7 times the amt. of the packed filter medium is discharged from the tank in about 10sec by adjusting the opening degree. Consequently, the entire filter bed 4 is integrated and slightly lowered, a spirally agitated region is formed at the upper part in the tank, and the whole filter bed 4 is transiently disintegrated, developed and spread.</p> |
