Abstract: A vessel is described for facilitating the removal of difficultly oxidizable impurities such as phenol and/or polychlorinated biphenyl from dilute aqueous solutions or dispersions. The vessel contains stacked, packed beds having characteristics of alternating high and low electrical conductivity with separately controlled pairs of electrodes for the two alternate types of beds. An aqueous solution containing contaminants is admitted to the vessel and passed through the successive beds wherein the solution or dispersion is subjected to an alternating current field for decomposition of the contaminants in the high resistivity beds and oxidization thereof in the lower resistivity beds by hydrogen peroxide produced by alternating current electrolysis of water. The preferred electrodes are hollow and water cooled. In addition, the bed is jacketed and cooling water is circulated through the jacket to maintain a more efficient, lower process temperature.