Physicochemical pre-treatment for the destruction of two non-biodegradable herbicides (metobromuron and isoproturon) were conducted by different advanced oxidation processes, i.e. the systems UV/TiO2, UV/TiO2/H2O2, Fe3+/H2O2, and UV/Fe3+/H2O2. The degradation rates were always higher for the photo-Fenton reactions when compared with the heterogeneous photocatalytic systems. Optimal concentrations of Fe3+ and H2O2 for the abatement of both herbicides in the photo-Fenton system were found. During the phototreatment, experiments were made to obtain information concerning the evolution of: (a) organic carbon and initial compound concentration, (b) the oxidation state, (c) ions, (d) the toxicity, (e) the biodegradability, and (f) the chemical nature of the intermediates. These analysis show that the solution resulting from the photodegradation of metobromuron is not appropriate for a biological treatment, probably due to the formation and the accumulation in the bulk of bromide intermediates, which are highly bio-recalcitrant. In contrast, the solution resulting from the phototreatment of isoproturon is biologically compatible and its complete mineralization can be performed by biological means. A combined photo-Fenton and biological flow reactor for the degradation of isoproturon was operated in continuous mode at laboratory scale. In this coupled system, 100% of the initial concentration of isoproturon and 95% of TOC were removed. Some field experiments under direct sunlight were carried out at the Plataforma Solar de Almeria in Spain. The obtained results demonstrated that the solar catalytic treatment is effective for the purification of water contaminated by the herbicides under study.