FILTER DEVICE AND FILTERING METHOD

PROBLEM TO BE SOLVED: To provide a filter device wherein a filter material can be washed and unclogged better then the conventional materials. SOLUTION: The filter device 1 having a filter vessel 2 accommodating a granular floating filter medium 10 to form a floating filter medium layer 11 in the upper zone of the interior filters a raw liquid fed into the filter vessel 2 by causing the raw liquid to flow through the floating filter layer 11 upward from the lower side. The filter device 1 further comprises a stirring device comprising a stirring blade 12 inserted into the filter vessel 2 through the upper zone of the filter vessel 2 rotatably in the floating filter medium layer 11 and a drive unit 13 for rotatively drive the stirring blade 12 from outside the filter vessel at variable rotational speed. COPYRIGHT: (C)2006,JPO&NCIPI