To provide a filtration apparatus in which fluidity of the filter medium can be increased by cleaning a water collecting member, foreign matters depositing on the water collecting member can be easily removed during cleaning, and increase in the size of the apparatus can be avoided.

The filtration apparatus is equipped with a filtration tank (1) where raw water flows into, a water collecting member (8) inclined downward from the wall of the filtration tank to the bottom, a filtration layer (9) comprising a granular filter medium deposited on the water collecting member, a filtrate reserving part where the filtered water passing through the filtration layer and the water collecting member is reserved, and a cleaning means for the water collecting member. The water collecting member consists of a plurality of wedge wire type water collecting plates, with each back side of the water collecting plate provided with a water collecting box (22) as the filtrate water reserving part. The cleaning means for the water collecting member is composed of a cleaning pump (26), pipes connecting each water collecting box with the upstream side and the downstream side of the cleaning pump, and a valve to control the flow of the filtrated water from the upstream side pipe to the downstream side pipe. When the water collecting plste is cleaned, the filtrate water in the water collecting box collected by anather water collecting plate is used as cleaning water.

COPYRIGHT: (C)2004,JPO