To improve filtration efficiency by detecting the clogging in a physical filtration stage from an increase in the pressure of the introduced basin water, operating a compressing and squeezing plate in a physical filtration tank in response to the increase to compress a group of mediums coated with sludge which are squeezed, separating and settling the sludge depositing on each medium.
The basin water is pressurized by a circulating pump 9, introduced into the physical filtration tank 2' of an inner cylinder 2 from the bottom of a filter 1 and passed upward between the filter mediums consisting of an elastic body 3, and the sludge in the basin water is deposited on the filter medium and aggregated. In this case, when the clogging in the physical filtration tank 2' is sensed by a pressure switch 12, a compressing and squeezing plate 4 is moved downward by the rotation of a screw rod 18 to compress a group of the elastic bodies 3 which are squeezed, and the sludge depositing on the respective elastic bodies 3 is separated. The circulating pump 9 is operated about the time when the settling is finished, the sludge is discharged outside the tank by the pressurized basin water through a solenoid valve 16, and the plate 4 is returned to the original position.
YAMAMOTO TOSHINORI
KUSADA SHOZO
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