Method for filtering surface water with thin supernatant layer and implementing plant

A method for filtration of a liquid media, including the filtration of surface water, comprising the steps of:

• bringing a first stream of the liquid to be filtered into contact with a surface of a filter medium and passing the liquid to be filtered through the filter medium, wherein the first stream has a flow rate (Q);
• creating a supernatant liquid layer on the surface of the filter medium, and controlling the level of the supernatant liquid layer so that the supernatant liquid layer has a defined thickness (e);
• organizing a hydraulic path in the supernatant liquid layer, wherein the hydraulic path has a length (L), defined between an inlet and an outlet of the hydraulic path;
• introducing the first stream into the inlet of the hydraulic path;
• passing the first stream through the filter medium for a plurality of n cycles;
• recovering the liquid that has passed through the filter medium for the plurality of n cycles and reinjecting a second stream of the recovered liquid into the supernatant liquid layer at the outlet of the hydraulic path, wherein the second stream has a flow rate (nQ), so that the first stream and the second stream meet and oppose each other in a section of the hydraulic path;
• and
• drawing treated liquid off from the hydraulic path after the plurality of n cycles, wherein the treated liquid is drawn off at a flow rate (Q).