A filter apparatus in a container ( 2 ) containing non-clarified contaminated liquid, especially wastewater ( 3 ), for clarifying the contaminated liquid, which comprises a plurality of spaced filter elements ( 4 ) arranged in a circle or a polygon on a rotatably supported hollow shaft ( 5 ), wherein the filter elements ( 4 ) are connected to the hollow shaft ( 5 ) in order to remove clarified liquid as permeating fluid ( 16 ) through the hollow shaft ( 5 ) out of the container ( 2 ) via a stationary pipeline ( 7 ). The rotating hollow shaft ( 5 ) separates the wastewater ( 3 ) from the permeating fluid ( 16 ) via at least two sealing elements ( 17, 18 ), and a blocking medium is arranged between the sealing elements ( 17, 18 ) for separating wastewater ( 3 ) and permeating fluid ( 16 ).