Wet oxidation technology: a potential biosolids management alternative

As New Zealand’s landfill space becomes increasingly limited, diverting waste from these landfills has become a focus via the Waste Minimisation Act 2008. This includes finding alternative management strategies for the large percentage of municipal biosolids currently being landfilled. A wet oxidation process for municipal biosolids was investigated as a potential technology to avoid these biosolids from going to landfill. In essence, this technology uses high pressure and temperature in the presence of an oxidising agent to deconstruct municipal biosolids. Simultaneously, this technology may be controlled in a manner that creates value-added by-products.By applying this technology to municipal biosolids, a substantive mass reduction of more than 90 per cent was achieved. In addition, process conditions were chosen such that readily degradable carbon compounds, such as acetic acid, were formed. These compounds were found to be excellent supplements for the enhancement of activated sludge treatment systems.Subsequently, Environmental Life Cycle Assessment (LCA) of the wet oxidation process was used to compare strengths and weaknesses of this technology with landfilling, particularly for energy consumption, global warming potential, eutrophication potential and photochemical ozone creation potential. The wet oxidation scenario displayed a significant positive impact on global warming and eutrophication compared to landfilling, but displayed a relatively high energy requirement.Overall, this technology has potential for significant improvements in biosolids management. Current investigations into this technology aim to optimise mass and energy flows. These will be key to the successful implementation of this technology within New Zealand.