A kinetic model for the simultaneous degradation of dichloroacetic acid (DCAA) and formic acid (FA) has been developed. The oxidation is produced by the combination of hydrogen peroxide (HP) and UV (253.7 nm) radiation. A set of four equations, three differentials and one algebraic, represents the time evolution of the concentration of DCAA, FA, HP and hydrochloric acid (HCl), a measurable by-product. The model is based on a complete reaction mechanism, which comprises hydrogen peroxide photolysis and decomposition of dichloroacetic and formic acids. It takes into account the effect of non-uniform distribution of the local rate of absorbed photons. The mathematical model renders simulation results that agree with the experimental data. It was also shown that FA decays much faster than DCAA. (c) 2013 Elsevier B.V. All rights reserved.