Treatment of phenolic wastewater by ozonation in a new gas-induced reactor was investigated. The reactor was designed in such a fashion that gas induction was created on the liquid surface by the high-speed action of an impeller turbine inside a draft tube to maximize the ozone usage. Another important feature of the present reactor design was the granular activated carbon (GAC) bed packed in a circular compartment between the reactor wall and the shaft tube. Because of the adsorption and possible catalytic reaction by GAC, enhanced phenol decomposition and chemical oxygen demand (COD) were observed in the experimental tests, providing the evidences of the synergistic effects of adsorption, catalytic reaction, and ozonation. In addition to enhanced phenol and COD removal, ozonation was found to provide in situ GAC regeneration, which was considered highly beneficial in the industrial GAC adsorption process.