The paper discusses multireaction models in ozonation, in particular residual COD models and radical chain models. As a result of the large number of estimable parameters, multicomponent reaction models in ozonation may lead to overparametrization in nonlinear parameter estimation. The use of theoretical COD values of known components in the residual COD model and knowledge obtained from the stoichiometry of reaction equations enables a remarkable reduction in the number of parameters to be estimated. The reliability and identifiability of the estimated parameters is demonstrated using both classical statistical analysis and Markov chain Monte Carlo (MCMC) analysis. (C) 2010 Elsevier B.V. All rights reserved.