Batch experiments on catalytic ozonation in buffered and non-buffered solution of refractory organic compounds like oxalic, acetic, salicylic and succinic acids are presented. The concentration of dissolved organic carbon (DOC) in each test was 60 mg/l and the applied batch procedure allowed a clear distinction between adsorptive and reaction processes. Results have confirmed that Al2O3 can be an effective catalyst for the conversion of dissolved organic compounds into CO2, but strength and performance of the catalysis are directly depending on the applied model compound and the matrix of solution. Catalytic effects were mostly pronounced in non-buffered solution and succinic acid exhibited the highest affinity for the reaction with an applied gamma-Al2O3. Semi-continuous trails in buffered and non-buffered solution of succinic acid confirmed the catalytic activity of Al2O3 for oxidation and, moreover, showed increasing catalytic effectiveness of the alumina with rising ozone dosage. The performance was comparable or superior to classical perozone treatment depending on the applied dosage of ozone. Different reaction mechanisms of the heterogeneous system are discussed and a suggestion of possibly involved reaction paths is presented. Higher oxidation performance might be explained by an interaction between ozone and OH surface groups of the alumina. (C) 2003 Elsevier B.V. All rights reserved.