Abstract: A method for filtering and backwashing solid particles out of liquids is illustrated, with a filter drum (5) positioned completely below the liquid level (6) having a cylindrical surface (7) coated with a filter medium (8), the liquid flown through the outside of the filter drum to the inside. A backwashing device for removal of the filter cake from the filter medium is provided. At the beginning of each cycle of backwashing an air cushion (15) is introduced in the filter drum (5) and liquid in the filter drum (5) is displaced in such a manner so that liquid jets from an ejetion apparatus (19) containing a spraying head (17) and being arranged in the interior of the filter drum without being sealed on the filter drum penetrate through the air cushion (15) to the backside of the cylindrical surface (7) of the filter drum (5). The filter cake so removed from the filter drum is withrawn at the outside of filter drum (5) in a stream of liquid.