Non-Catalytic Subcritical Wet Oxidation of a Wastewater Treatment Sludge

Among the treatment and conversion technologies used for organic solid waste, wet oxidation has become an important process due to the fascinating characteristics of water as a reaction medium at elevated temperatures and pressure. Wet oxidation is able to degrade and remove organic compounds and thus reduce the mass and volume of solid wastes. Recovering valuable compounds and enhancement of anaerobic fermentation are the other advantages. Wet oxidation of soluble compounds such as phenol, aromatic alcohols and carboxylic acids has been well studied. However, behaviour of wet oxidation of wastewater treatment sludges has not been studied completely due to their complex structure. The current work was aimed at investigating non-catalytic wet oxidation of wastewater treatment sludge and studying degradation of solids, organic compounds and nutrients. A fermented mixed sludge which consisted of primary and secondary sludges was subjected to wet oxidation at temperature ranging 220-240 °C, oxygen to biomass ratio of 1:1-2:1 and stirring speed of 300-500 rpm. Wet oxidation was effective at degrading the organic solids, with approximately 90 % degradation within 60 minutes. It was found that reaction temperature has the most significant impact on sludge oxidation. The results also showed production of acetic acid under wet oxidation treatment. KeywordsSludge; wastewate treatmentr; wet oxidation; hydrothermal processing