A device for the treatment of an influent with a nonbonded media, and when the media becomes spent, the media is fluidized with a backwash fluid. Concentric inner and outer perforated cylinders contain a column of media therebetween. The influent is passed radially inwardly through the column of media and into the lower portion of the inner perforated cylinder, where the effluent is removed from the device. During a backwash operation, a backwash fluid is forced into the lower portion of the inner perforated cylinder, radially outwardly into the column of media to provide an upwardly directed drag force. When the drag force exceeds the buoyant weight of the media, the media is fluidized so that the contaminants can be removed therefrom by the backwash fluid.