The material is fed into a pre-wash tank on the underside of the pre-wash screw and pressed under water by paddle rollers. The material is then conveyed to the top by 1-2 screw conveyors. The material moves a lot during transportation, so contaminants such as stones, sand, glass and metals can easily sink. In addition, the adhesions on the
plastic, so that they can be removed more easily.

Different discharge systems can be used depending on the type of contamination. Simple, small contaminants such as stones or glass are removed via a time-controlled pusher system. For larger or long contaminations, such as wire, or larger quantities of contamination
scraper chain conveyors or screw conveyors are used to discharge contamination.