The invention relates to a facility for treatment of an aqueous effluent by hydrothermal oxidation, which comprises: a reactor comprising a tube in which the aqueous effluent to be treated flows, the tube of the reactor having a plurality of bends formed by oxidant-injection devices, each oxidant-injection device comprising: a reactor part (32) forming an effluent-circulation channel (35) bent at an angle in which a flow of aqueous effluent can circulate, and an injector part (33) comprising a first opening (49) suitable for being connected to a source of oxidant located outside the effluent-circulation channel (35) and a second opening (50) located in the effluent-circulation channel (35), and a source of oxidant connected to the injector part so as to inject the pressurised oxidant into the flow of aqueous effluent to be treated.