The Fenton oxidation process was used to remove COD from landfill leachate and olive mill wastewater. The researchers found that the process effectively removed over 70% of COD from both types of high organic content wastewater. Optimal conditions for treatment included specific pH levels, concentrations of Fe (II) and H2O2, reaction times, and temperatures. For olive mill wastewater, the maximum COD removal was 72.17% in 60 minutes, while for landfill leachate, it was 80.37% in 30 minutes. This suggests that Fenton oxidation could be a useful preliminary treatment option for these types of wastewater.