In this study, the ozonation of raw hospital wastewater was conducted in the batch reactor and the efficiency of this pretreatment was evaluated based on both chemical oxygen demand (COD)-in H2O2 and absorbance-non-H2O2. Process variables as initial pH, reaction time, ozone concentration and H2O2 were investigated as major factors. Response surface methodology (RSM) was applied to evaluate the major factors influencing organic matter and color removal rates, and the interactions between these factors, and optimized the operating parameters as well. Quadratic models were developed with 60% absorbance and 46% COD as the responses, and the model predictions were confirmed to be appropriate to the experimental data with a deviation less than 3.5%. (C) 2014 Elsevier B.V. All rights reserved.