A pre-separator for a screw press separator wherein the pre-separator increases the concentration of solid material in a water solid material mixture. The pre-separator is configured to have a frustoconical screen surface where a plurality of wiper blades engage the interior portion of the surface to provide de-watering action, and the plurality of blades are configured to reposition with respect to the center axis of the frustoconical surface to allow for engagement between the interior surface of the frustoconical screen, and the wiper blades.