A filter apparatus in a container containing non-clarified contaminated liquid, especially wastewater, for clarifying this liquid consists of several spaced filter elements arranged in a circle or a polygon on a rotatably supported hollow shaft. The filter elements are connected to the hollow shaft in order to remove clarified liquid as permeate through the hollow shaft out of the container via a stationary pipeline. The rotating hollow shaft separates the wastewater from the permeate via at least two sealing elements. A blocking medium is arranged between the sealing elements.