To sufficiently use trapping capability of a removed medium and also secure the amount of water supply with stable water quality.

A system includes: removal capacity recovery units 6, 15, 16; water quality measures 10 and 12; flow rate detector 13; time information measure 32; recovery time setting means 18; total removable amount setting device 19; removal performance quantity calculator 33 for calculating a substance to be removed (removed performance quantity) removed after a removal capacity recovery operation; recovery time determinator 34; residual removable amount calculator 35 for calculating the amount of the substance to be removed (residual removable amount) removable after a recovery time; residual removable time calculator 36 for calculating residual removable time capable of producing treated water without causing the substance to be removed to leak into the treated water after the recovery time; and recovery operation controller 38 that carries out the removal capacity recovery operation when the residual removable time is less than time until a next recovery time and does not carry out it when the residual removable time is not less than time until the next recovery time.