The Fenton and photo‐Fenton detoxification of non‐biodegradable chemical pollution in water was investigated under simulated UV light in the laboratory and under direct sunlight in Ouagadougou, Burkina Faso. The laboratory experiments enable one to make a systematic diagnosis among three types of wastewaters, identifying a biorecalcitrant wastewater containing the Chloro‐hydroxy‐Pryridine (CHYPR). The application of the photo‐Fenton process on effluent containing the CHYPR showed not to stimulate the generation of biodegradable by‐products. Optimal conditions for detoxification of effluent containing the CHYPR were found at pH = 2.8, [Fe 2+ ] = 5.2 mM, initial [H 2 O 2 ] = 768 mM, for an effluent concentrated at 2.2 mM of CHYPR. The application of the photochemical process on a field pilot solar photoreactor for the detoxification of water polluted with a pesticide made with Endosulfan showed very promising results, with potential biodegradable effluents obtained at the end of the photochemical treatment. Optimal conditions of the applied study were found at pH = 3. [H 2 O 2 ] = 8 mM and [Fe 2+ ] = 0.18 mM for an initial concentration of 0.36 mM of Endosulfan.