Experiments on alachlor degradation by ozonation alone and combined with hydrogen peroxide using different surface waters have been conducted in a reactor bubble column and a kinetic model of the advanced oxidation process has been proposed. Variables studied were the nature of the surface water (four surface waters were treated), pH (3.5-9.7) and hydrogen peroxide to ozone mass ratio at the column inlet (0.1-1.85g g(-1)). Data on residence time distribution, rate constants and the absorption kinetic regime were considered to prepare the kinetic model, which was also based on the axial dispersion model of non-ideal flow. The model gives good predictions of alachlor and hydrogen peroxide conversions and the fraction of dissolved ozone (deviations were lower than +/-15%) although it fails, in some cases, to yield accurate estimates of the observed experimental trends of concentrations in water at the reactor column outlet. The calculated results were close to those obtained from the more classical N well-mixed tanks-in-series model (deviations with this model were lower than +/-20%). It is concluded that quantitative deviations from experimental observations were likely due to the lack of rate data on ozone reactions with organic matter present in the surface waters investigated.