Recovery of tungsten, vanadium and titanium oxide from spent DeNOx catalysts, used for stationary applications like power plants, in which the carrier is made up of TiO2, that represents the majority of the material, and thus has to be converted into valuable materials like photocatalysts or pigments for ceramics and paints. Processes for efficient treatment of produced water (PW), through: adsorption of metals by synthetic zeolites produced by spent FCCCs, characterized by a low concentration of the two rare earth elements (cerium and lanthanum); integrated biological processes to remove organic compounds, for example microalgae that represent the last frontier for the degradation of the organic matter contained in wastewater