A system is provided with a solid-liquid separator which can transport sludge and other material for treatment without clogging and can efficiently separator liquid from such material for treatment. The system includes movable plates and fixed plates alternatingly disposed and two screws disposed in holes formed in the movable plates and fixed plates. The screws have blades that partially overlap. As the two screws rotate, the material for treatment is transported and the effluent is discharged through the gaps between the movable plates and fixed plates.