The main purpose of a screening system is to remove larger particles and solids which could block or damage downstream processes. Furthermore non dissolved parts are preferably removed in early stage to prevent unnecessary amplification of more challenging dissolved pollutants removal. The screening systems are typically fed from an influent pump pit and pump capacity may subsequently determine the filter intake flow.
Screens may yield their specific pollutant in a very concentrated, pure form. This may lead to the benefit of recovering valuable solid matter before it enters the effluent treatment (e.g. vegetable peels which can be sold as animal food) Most solutions will create retention time for screenings to drain which results in dryer screenings leading to less and dryer sludge. Sludge may be discharged into a container via a chute.
The mesh, ranging from 0,5 up to 3mm, is typically made of a triangular shaped wire which is very difficult to block. The maximum capacity of the filter depends on the pollution load and the mesh width. Additional cleaning can be executed by (high pressured) spraying devices with hot or cold water, screen vibration, scrapers/brushes or a backwashing system. Screen solutions may be put into effect for factory effluent, truckwash installations, social water, CIP-installations or yard water treatment.