FILTRATION SYSTEM AND WASHING METHOD OF FILTRATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a filtration system and a method for washing the filtration system capable of backwashing a floating filter medium layer at an effective timing even when the inflow amount of raw water varies.SOLUTION: There is provided a filtration system which comprises: a first vertical hole 10 having a floating filter medium layer 12, a screen 11 for preventing the outflow of the floating filter medium layer 12, a raw water inflow port 13 and a backwash effluent discharge port 14 and a filtrate water storage part 15 provided on an upper side of the screen 11; a backwashing mechanism for backwashing the floating filter medium layer 12 in a downflow manner and a second vertical hole 20 into which raw water is flowed; a raw water supply passage 41 for supplying raw water; and a backwashing mechanism controller which does not allow the start of backwashing of the floating filter medium layer 12 using the backwashing mechanism when the inflow amount of raw water flowing into the vertical hole 20 per unit time exceeds a predetermined amount and allows the start of backwashing of the floating filter medium layer 12 using the backwashing mechanism when the inflow amount of raw water flowing into the vertical hole 20 per unit time is equal to or smaller than the predetermined amount.