Screenings are separated and removed by the action of a rotating drum and an internal auger and are rejected trough the outlet shoot. Wastewater enters the drum internals via specially designed influent distributor that delivers the liquid tangentially to the screening surface. Filtered effluent flows via outlet port at the bottom of the lower case.

A washing header with spraying nozzles serves the cleaning of the external surface of the drum. Units are fabricated with different drum diameters and lengths as well as variable perforations covering in this way a wide capacity range.