The Combined Unit model SET 2. make a first screening by a screw screen placed at the top of the machine; the particles with dimension major than the mesh of the screen are trapped. Thanks to a series of brush mounted on the screw are removed and lifted the solidi that are washed and compacted befor the discharge. Also thanks to high pressure nozzles the screeen remain clean and without solids costantly.

The water and the solids passed throght the screen are collected in a longitudinal tank, where a blower cause a whirling motion that separate the grit from the organic material; the last one remain on the surface of the water, while the grit decants on the bottom for major specific weight respect to the water, where a bottom screw conveys the material in a collection tank. Now a extracting screw lift up the grit and discharge it out of the machine. The water for overflow exits out of the machine throught an appropritate hopper.