Abstract: In a rotatable filter, such as a disk filter, for separating solid particles from a liquid mixture, in which a filter material (3) is partially immersed, a cake-removal member (11) is designed to take off a layer of the formed cake of solid particles from the filter material, so that a liquid-permeable coating, which itself acts as a filter medium, is left on the filter material which is moved down into the liquid mixture which is to be separated. According to the invention, for renewing the coating a spraying apparatus (13-17) is designed to spray jets of liquid in at least one spray zone (18), through which only a part of the filter material passes upwards during the rotating movement of the filter material, so that the whole cake of coarse particles, including the coating, is removed from the part of the filter material by the jets of liquid.