Apparatus comprising at least one rotatably driven drum having a circumferential filter medium adjacent which pressurized liquid suspension containing fibrous material is supplied in the rotary direction of the drum driven rotation. One or more baffles, having low friction material on their surfaces opposing the filter medium, are resiliently biased by pressurized liquid and/or mechanical biasing means to gradually converge towards the filter medium in the rotary direction of the drum driven rotation, and fibrous material collected on the filter medium may be washed by either the biasing liquid or separately supplied pressurized liquid. Also, a method for processing a suspension containing fibrous material through the employment of such an apparatus.