A rotatable separator drum includes a vertical rotating axis of rotation and at least one flow channel having an inlet opening and an outlet opening. Also included is at least one retaining dam arranged in the at least one flow channel in a region between the inlet opening and the outlet opening. The at least one retaining dam is configured to allow an overflow of liquid over the at least one dam and to provide for an accumulation of solids in front of the at least one dam. The at least one dam includes at least one rib arranged in a transitional region between opposing wall sections and a distributor base cover and the at least one rib includes portions having differing heights.