Enhanced wet air oxidation of sediment contaminated with PCBs

Wet air oxidation (WAO) is investigated as a method of treating river sediments contaminated with polychlorinated biphenyls (PCBs). Aqueous slurries containing 2.5% (w/w) sediment were oxidized with oxygen in a one liter, high-pressure, batch reactor at temperatures up to 250 degrees C. Concentrations of PCBs adsorbed on the sediment and reactor surfaces and dissolved in the water and gas phases after oxidation were determined by high-resolution gas chromatography. Results indicate that no significant wet oxidation of PCBs in sediment slurries occurs for temperatures at or below 250 degrees C. However, during reactor heat-up, significant degradation of PCBs occurred at high temperature regions near the reactor wall even when bulk fluid temperature was quite low. A variety of amendments were tested to determine their effect on PCB oxidation. These amendments included hydrogen peroxide, a readily degraded organic compound (phenol), and homogeneous copper catalyst. Only hydrogen peroxide addition resulted in a significant degradation of PCBs. The addition of phenol did not result in enhanced degradation of PCBs through kinetic coupling as has been observed for other recalcitrant organic compounds.