Degradation of phenolic compounds in Kohtla-Järve oil shale ash dump wastewater (North-East Estonia) by O3, O3/UV, O3/H2O2, O3/H2O2/UV, O3/TiO2and O3/TiO2/UV treatment in a countercurrent film absorber was studied experimentally. The mathematical model and the simulation algorithm of the processes were developed. The random search optimizer was applied to evaluate the values of reaction rate constant, mass transfer enhancement factor, stoichiometric coefficient and volatilization coefficient for organics into the process models. The evaluated coefficients for individual phenolic compounds, total content of phenolic compounds and COD for different oxidation systems are presented and discussed. “Operation” of the simulated film absorber (based on the evaluated coefficients) and the experimental column are compared.