PURPOSE: To reduce a running cost and equipment cost of sewage treatment by filtering sewage with a filtering means formed with thin-film layers of a metal hydroxide on its surfaces by a water head pressure and peeling the thin-film layers together with contaminating materials when the water pass rate of the filtering means decreases, then forming the thin-film layers again on the surfaces of the filtering means.

CONSTITUTION: A slurry 21 previously suspended with the metal hydroxide and non- compressive material is admitted into a filter tank 7 and is filtered and separated on the surfaces of a water permeable sheet 11 by the water head pressure at the time of the sewage treatment. The treated water 13 in a reflux tank 15 is thereafter admitted into the filter tank 7 and the non-compressive material is filtered and separated on the surfaces of the water permeable sheet 11, by which the thin-film layers of the metal hydroxide are formed thereon. The sewage 2 is admitted in this state and the treated water 13 is discharged into the reflux tank 15 and is released from a releasing pipe. the treated water 13 in the reflux tank 15 is sent to a filter body 10, where the thin-film layers are peeled together with the captured contaminating materials and are discharged outside the tank. The thin-film layers of the metal oxide are thereafter formed again on the surfaces of the water permeable sheet 11.