Supercritical water oxidation of a heavily PCB-contaminated mineral transformer oil: Laboratory-scale data and economic assessment

Although a great deal of research has been devoted to PCBs destruction by supercritical water oxidation, PCB-contaminated oils, which represent a high percentage of existing PCB wastes in South American countries, have been barely studied. In this paper we present experimental results on the supercritical water oxidation of a real-world mineral transformer oil highly contaminated with PCBs. Process conditions of 539 °C, 350% oxygen excess and 241 bar allow one to obtain a 99.6% organic matter destruction of the complex mixture of hydrocarbons and PCBs. The PCB concentration in the aqueous effluent was below the detection limit of the chromatographic method used in the analysis, and a toxicity test for Daphnia pulex showed that the aqueous effluent of the process is not ecotoxic. Based on these results, a process flowsheet of a supercritical water oxidation mobile pilot plant was proposed as an alternative to incineration. A preliminary economic assessment of the proposed flowsheet shows that the process is feasible when compared to treatment by incineration.