The decomposition of the organic substrate present in wastewaters from the washing stages in the black table olives industry is studied in batch reactors by means of several treatments: by ozonation processes, with ozone alone, and in combination with hydrogen peroxide and UV radiation; by aerobic biodegradation; and by the ozonation of the aerobically pretreated wastewaters. In the ozonation processes, the effect of the inlet ozone partial pressure on the substrate removal, biodegradability, and aromatic compounds content as well as the influence of the presence of H2O2 and UV radiation on the substrate removal is established. A kinetic study is conducted which leads to the evaluation of the kinetic constants for the substrate reduction and ozone disappearance. In the aerobic degradation treatment, the evolutions of the substrate and biomass are followed during the process, and a kinetic study is performed by using the Contois model, which applied to the experimental data provides the specific biokinetic constant K-C. Finally, in the ozonation process of the biologically pretreated wastewaters, the effect of the aerobic pretreatment on the substrate removal and the kinetic constant obtained is also discussed.