Filter apparatus with sand filter bed

摘要

A filter apparatus removes foreign substances contained in raw water by passing the raw water through a filter layer (8) made up of a particulate filter medium disposed in a filter tank (1). The apparatus is made up of: a partition wall (2) provided inside the filter tank (1) so as to extend from an upper end of the filter tank (1) downward while leaving a space to a bottom surface (7) of the filter tank (1) such that the filter tank (1) is divided into a supply portion (4) having a raw water supply port (3) and a discharge portion (6) having a backwashed water discharge port (5); wherein the bottom surface (7) of the filter tank (1) is inclined from the discharge portion (6) downward toward the supply portion (4), the bottom surface (7) having the filter medium spread thereon in a manner to cover both the supply portion (4) and the discharge portion (6), 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 (2); water collecting pipe (10) embedded inside the filter medium for collecting filtered water; and backwashing device for backwashing the filter medium.