The invention relates to an electrode suitable for decreasing the chemical oxygen demand of waste-water comprising: a) a permanent component; and b) a sacrificial component arranged face-to-face and releasably attached to the permanent component and in electrical contact therewith, said permanent component consisting of a Substrate of a valve metal equipped with a catalytic coating containing noble metals or oxides thereof, said sacrificial component containing elemental iron. Further the invention relates to a method for abatement of the chemical oxygen demand in an aqueous waste containing oily compounds, glycols or waxes, optionally consisting of a foundry waste, by an electrolytic process involving anodic chlorine evolution in the presence of trivalent iron. Chlorine evolution may be carried out on the surface of an anode consisting of a catalytically activated-valve metal permanent component coupled to an iron-containing sacrificial component.
