Wet Air Oxidation of Municipal Sludge: Return Experience of the North Brussels Waste Water Treatment Plant

For large cities which cannot afford to sustain land disposal of sludge, Wet Air Oxidation appears to be an interesting option, perceived as environmentally friendly to a public opinion some times reluctant toward conventional incineration. However, due to significant investment costs, it is relevant to reduce upstream the amount of sludge by anaerobic digestion. This paper presents the North Brussels WWTP (1.1 Million pe), which was started-up in 2006. The sludge treatment consists of thermal hydrolysis of dewatered sludge followed by high load mesophilic anaerobic digestion and Wet Air Oxidation. The Wet Air Oxidation final product is then dewatered and dried to over 90% solids content, prior to being disposed as a cover product for landfills.