Abstract: The present invention relates to the treatment of sludge and, more particularly, to a method for recovering phosphate as a substantially solid component from a phosphate-containing sludge. Some embodiments of the invention relate to a method for recovering phosphate as a substantially solid component and aluminum as a liquid component from a phosphate-containing and aluminum-containing sludge. The method incorporates wet oxidation to decompose the organic components of the sludge to provide a residual sludge. The residual sludge comprises the insoluble components and, in some embodiments wherein the sludge comprises aluminum, the residual sludge further comprises suspended and/or soluble aluminum.