A microwave (MW)-assisted catalytic wet air oxidation (CWAO) process under low temperature (150 degrees C) and low pressure (0.8 MPa) was investigated to treat heavily contaminated petroleum wastewater from oil refining industry. The MW-CWAO experiments were carried out in a reconstructive MW autoclave, using GAC (5 wt.%) as catalyst. The experimental temperature was kept at 150 degrees C and oxygen was supplied into reactive system with 0.8 MPa pressure. The results demonstrated that more than 90% of chemical oxygen demand (COD) removal was obtained and the biodegradability of BOD5/COD ratio was increased from 0.04 to 0.47 within 30 min, indicating a significant improvement of biodegradability for the solution, which is beneficial for the further biotreatment of petroleum wastewater. The reaction kinetics show that reactive activation energy for COD conversion was calculated to be 25.11 kJ/mol. This MW-assisted CWAO approach may have significant potential in application for treatment of industrial wastewater. (c) 2008 Elsevier B.V. All rights reserved.