Process and installation for the treatment of effluents by oxidation in the presence of a heterogeneous catalyst

A process of aqueous phase oxidation of effluents comprising subjecting said effluents to oxidation in the presence of at least one oxidizing agent inside a reactor in which a gaseous phase is set up above the liquid phase including the effluents, and subjecting said gaseous phase to catalysis in the presence of at least one heterogeneous catalyst, positioned above the interface between the liquid phase and the gaseous phase and spaced inwardly of the walls of the reactor, said process being carried out at a temperature of between approximately 20.degree. C. and approximately 250.degree. C. under a total pressure of between approximately 1 and approximately 160 bars, in such manner as to mineralize at least part of the organic matter and total ammoniated nitrogen contained in said effluents and characterized in that it comprises increasing the contact time between the gaseous phase and the heterogeneous catalyst by recycling at least part of said gaseous phase present in said oxidation reactor after its passage through said heterogeneous catalyst by directing a portion of the gaseous phase from the oxidation reactor and then back into contact with said heterogeneous catalyst in order to obtain substantial removal of NH.sub.3, COR and volatile organic compounds.