US Patent 7267767 Filtration apparatus

A cleansing tank 38 and a screw conveyor 32 are removably mounted to a mounting opening 22 of a filtration tank 2. When the cleansing tank 38 and the screw conveyor 32 are to be removed, they can be extracted to the exterior of the filtration tank 2, by detaching a base 28, which axially supports the screw conveyor 32, from a rim 24. Purified water is backwashed through a purified water discharge pipe 60 when the cleansing tank 38 and the screw conveyor 32 are extracted and inserted through the mounting opening 22. This causes filtration media 14 to float, thereby reducing the resistance thereof.