BACKGROUND: Furaltadone (FD), a nitrofuran derivative, is a highly effective chemotherapeutic drug. In China the FD wastewater discharged by the pharmaceutical industry is high in organics and biorefractory compounds. The objective of this study was to investigate the degradation mechanism of FD in aqueous solution by ozone oxidation. Preliminary results on the reaction mechanism were obtained using three different spectral analysis techniques. RESULTS: The ozonation mechanism was significantly affected by the pH value. At low pH values the primary reaction is direct oxidation of ozone, an incomplete oxidisation, which can only destroy the FD molecule's conjugated structure. At high pH values the major reaction changes to hydroxyl radical oxidation. FD can be rapidly oxidised into CO2, H2O, NH3, NO3-, HCHO, oxalic acid and other aliphatic acids of low molecular weight, which can be entirely mineralised by continued ozonation. CONCLUSION: The pH value significantly influences the mode of FD ozonation. The present experiment suggests a potentially useful pretreatment method for conventional biological treatment of wastewater containing FD. (c) 2008 Society of Chemical Industry.