To use active carbon powder effectively by a method in which raw water mixed with active carbon powder is passed through a filter for separating the active carbon powder mechanically to separate the active carbon powder from the water, and the separated active carbon powder is added again into raw water.

Raw water from a river 1 is introduced into a mixing basin 2, into which active carbon powder is supplied from a supply device 3. The water mixed with active carbon powder is passed through a filter 4 to recover the active carbon powder, which is fed again into raw water. In this way, the active carbon powder can be used repeatedly, and it is returned to the basin 2 through a pump P and a regenerator R. In the regenerator R, part of the used active carbon powder is removed. Since active carbon powder can be recovered from raw water without using a coagulant, a large amount of active carbon powder is used to enable efficient raw water treatment.