Screening is the first mechanical pretreatment process or preliminary treatment allowing the solid liquid separation of the waste contained in raw water. Two types of screen are distinguished, the coarse screen with an opening gap between 50 mm and 10 mm followed by smaller screen from 10 mm to 6 mm. Screening is often automated thanks to a motorization of the collection and ejection system. Manual solutions also exist requiring the action of an operator for a more affordable cost. The solid waste can then be discharged into a compaction system allowing a reduction in weight / volume and optimal dryness.