Device for the gasification in a supercritical medium of an aqueous effluent containing an organic matter and an inorganic matter, the device comprising: - a reactor comprising a main body designed to be filled with water, - pressure regulation means for pressurising the main body of the reactor to a pressure greater than or equal to 22.1 MPa, - heating means designed to heat an upper part of the reactor to a temperature ranging from 400°C to 800°C, so as to obtain water in the supercritical state, - an aqueous effluent inlet leading into the upper part of the reactor, so as to convert the organic matter of the aqueous effluent into gas, - cooling means, arranged around the main body of the reactor, designed to cool a lower part of the reactor, the lower part of the reactor being cooled according to a thermal gradient ranging from a first temperature lower than or equal to that of the upper part of the reactor and greater than or equal to 374°C in order to obtain water in the supercritical state to a second temperature lower than 374°C, so as to obtain water in the liquid state and solubilise the inorganic matter, - a water-gas mixture outlet, positioned at the lower part of the reactor at a temperature lower than or equal to that of the upper part of the reactor and greater than or equal to 374°C in order to obtain water in the supercritical state, - a liquid outlet, positioned at the lower part of the reactor, cooled to a temperature lower than 374°C so as to discharge from the reactor a brine containing the solubilised inorganic matter and water in the liquid state, the upper part and the lower part of the reactor being tubular and arranged coaxially. - a reactor comprising a main body designed to be filled with water, - pressure regulation means for pressurising the main body of the reactor to a pressure greater than or equal to 22.1 MPa, - heating means designed to heat an upper part of the reactor to a temperature ranging from 400°C to 800°C, so as to obtain water in the supercritical state, - an aqueous effluent inlet leading into the upper part of the reactor, so as to convert the organic matter of the aqueous effluent into gas, - cooling means, arranged around the main body of the reactor, designed to cool a lower part of the reactor, the lower part of the reactor being cooled according to a thermal gradient ranging from a first temperature lower than or equal to that of the upper part of the reactor and greater than or equal to 374°C in order to obtain water in the supercritical state to a second temperature lower than 374°C, so as to obtain water in the liquid state and solubilise the inorganic matter, - a water-gas mixture outlet, positioned at the lower part of the reactor at a temperature lower than or equal to that of the upper part of the reactor and greater than or equal to 374°C in order to obtain water in the supercritical state, - a liquid outlet, positioned at the lower part of the reactor, cooled to a temperature lower than 374°C so as to discharge from the reactor a brine containing the solubilised inorganic matter and water in the liquid state, the upper part and the lower part of the reactor being tubular and arranged coaxially.