The reaction kinetics of p-nitrophenol ozonation in a bubble column at pH 2 of water is studied. The reaction kinetic parameters, rate coefficients and stoichiometric coefficients, as well as the mass transfer coefficient are estimated by nonlinear estimation with the developed novel reaction kinetic model. The concentration of unknown intermediate compounds is presented as a residual chemical oxygen demand (COD) calculated from the measured COD and the theoretical COD for the known compounds. The decomposition rate of p-nitrophenol is almost the same on the pathway producing hydroquinone and on the pathway producing 4-nitrocathecol. Comparison of the rate coefficients with the case of initial pH 5 indicates that the p-nitrophenol degradation producing 4-nitrocathecol is more selective towards molecular ozone than the reaction producing hydroquinone. The identifiability and reliability of the estimated parameters, as well as the uncertainties involved in the model predictions are analyzed with the Markov chain Monte Carlo (MCMC) method. MCMC methods are Bayesian statistical methods that can be used for analyzing the distribution of parameters in nonlinear models in order to extend and support the information given by traditional regression analysis. (C) 2009 Elsevier Ltd. All rights reserved.