Abstract: A filter arrangement for thickening suspensions of fibrous material is shown as having rotating filter elements encased in a filter trough with such filter elements being pairs of filter disks fixed at right angles to a rotary hollow shaft and further defining a chamber as between such filter disks; the chambers are connected through the hollow shaft to a suction head to which down-pipes are linked and in which material outlet shafts are disposed between the pairs of filter disks; turbulence generating means are provided in the filter trough and the filter disks are provided with at least one ejector vane.