JPS5573308A - Filterring method - Google Patents

Abstract

PURPOSE: To carry out the continuous operation of the filter device and also prevent the bad effect caused to the filter interruption by a mechanism wherein a part of or all of the filtrated water is returned to a raw water tank and recirculated even if the water level of a raw water tank is lowered.

CONSTITUTION: When the water level of a raw water tank 1 is lowered to the designated low water level, a filtered water is returned to a raw water tank 1 at a preliminarily set flow amount from a return arranged pipe 8 to a raw water tank 1 provided by branching from a filtered water exhaust pipe 7 through the operation of a liquid level regulating meter 11 provided to a raw water tank 1 to prevent the lowering of the water level of the raw water tank 1. When the designated high water level is recovered by the increase of a raw water inflow, the supply of the filtered water flowed to a return arranged pipe 8 is interrupted. That is, the return arranged pipe 8 with a automatic valve 9 connected to the raw water tank 1 is provided by branching from a filtered water exhaust pipe 7 connecting the filter device 6 and a treated water tank 10 and operated with the liquid level regulating meter 11. When the water level is lowered to the designated low water level L, the valve 9 is opened at the preliminarily set opening degree and when reached to the disignated high level H, the said valve 9 is closed.

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