The combinations of the Fenton reaction, UV/H2O2 and the photo-Fenton process in the degradation of organophosphorus containing substrates such as fenitrothion, diazinon and profenofos were investigated. A laboratory set-up was designed to evaluate and select the optimal oxidation process. Several parameters were also studied: initial pH, COD/H2O2 ratios, Fe(II)/H2O2 ratios and the type of photocatalyst to define optimum operating conditions. The kinetic study indicated that the degradation rate of the used model substances was first order and the calculated reaction constants were affected by the parameters studied. The oxidation processes were repeated at the optimum operating conditions for the degradation of the mixture of the used model substances to represent the real wastewater effluent from a pesticide-producing company. A rough comparison of specific energy consumption was also evaluated to compare between the photochemical processes. The experimental results show that the light-enhanced Fenton reaction (photo-Fenton) proved to be a most effective and economic treatment process under acidic conditions and might be an alternative to other traditional processes.