Fuente: WIPO "olive oil" The present invention discloses stable composite membranes comprising a porous support having one or more thin selective layers coated on a top surface thereof, whereas at least one of said thin selective layers comprises a crosslinked fluorinated silicone polymer, and further wherein the total thickness of said one or more thin selective layers ranges between 0.1 to 10 microns. The use of these membranes in the process of olive oil wastewater treatment and the valorization of polyphenol-rich by-products, are also disclosed.