A facility for treating an aqueous effluent by hydrothermal oxidation, comprising: • a reactor comprising a tube in which the aqueous effluent to be treated circulates, the tube of the reactor having several bends formed by oxidant injection devices, each oxidant injection device comprising: - a reactor part forming an effluent circulation channel with a bent shape in which an aqueous effluent flow can circulate, the effluent circulation channel having a first channel portion through which the effluent flow enters into the reactor part and in which the effluent flow circulates in a first circulation direction and a second channel portion in which the effluent flow circulates in a second circulation direction forming a nonzero angle with the first circulation direction, and leaves the reactor part, and - an injector part comprising a first opening suitable for being connected to an oxidant source located outside the effluent circulation channel, a second opening located in the second channel portion and an oxidant injection channel extending from the first opening to the second opening in a direction parallel to the second circulation direction, so as to inject the oxidant in the effluent flow when the effluent is circulating in the second channel portion, and • an oxidant source connected to the injector part to inject the oxidant under pressure inside the aqueous effluent flow to be treated. • a reactor comprising a tube in which the aqueous effluent to be treated circulates, the tube of the reactor having several bends formed by oxidant injection devices, each oxidant injection device comprising: - a reactor part forming an effluent circulation channel with a bent shape in which an aqueous effluent flow can circulate, the effluent circulation channel having a first channel portion through which the effluent flow enters into the reactor part and in which the effluent flow circulates in a first circulation direction and a second channel portion in which the effluent flow circulates in a second circulation direction forming a nonzero angle with the first circulation direction, and leaves the reactor part, and - an injector part comprising a first opening suitable for being connected to an oxidant source located outside the effluent circulation channel, a second opening located in the second channel portion and an oxidant injection channel extending from the first opening to the second opening in a direction parallel to the second circulation direction, so as to inject the oxidant in the effluent flow when the effluent is circulating in the second channel portion, and - a reactor part forming an effluent circulation channel with a bent shape in which an aqueous effluent flow can circulate, the effluent circulation channel having a first channel portion through which the effluent flow enters into the reactor part and in which the effluent flow circulates in a first circulation direction and a second channel portion in which the effluent flow circulates in a second circulation direction forming a nonzero angle with the first circulation direction, and leaves the reactor part, and - an injector part comprising a first opening suitable for being connected to an oxidant source located outside the effluent circulation channel, a second opening located in the second channel portion and an oxidant injection channel extending from the first opening to the second opening in a direction parallel to the second circulation direction, so as to inject the oxidant in the effluent flow when the effluent is circulating in the second channel portion, and • an oxidant source connected to the injector part to inject the oxidant under pressure inside the aqueous effluent flow to be treated.