Filter apparatus with sand filter bed

Abstract

A filter apparatus removes foreign substances contained in raw water by passing the raw water through a filter layer ( ) made up of a particulate filter medium disposed in a filter tank ( ). The apparatus is made up of: a partition wall ( ) provided inside the filter tank ( ) so as to extend from an upper end of the filter tank ( ) downward while leaving a space to a bottom surface ( ) of the filter tank ( ) such that the filter tank ( ) is divided into a supply portion ( ) having a raw water supply port ( ) and a discharge portion ( ) having a backwashed water discharge port ( ); wherein the bottom surface ( ) of the filter tank ( ) is inclined from the discharge portion ( ) downward toward the supply portion ( ), the bottom surface ( ) having the filter medium spread thereon in a manner to cover both the supply portion ( ) and the discharge portion ( ), the filter medium being filled to such a depth that an upper end of the filter medium reaches at least a bottom end of the partition wall ( ); water collecting pipe ( ) embedded inside the filter medium for collecting filtered water; and backwashing device for backwashing the filter medium.