Hydrothermal degradation of organic matter in municipal sludge using non-catalytic wet oxidation

• Fermented municipal sludge was treated by non-catalytic wet oxidation.
• A significant degradation of solids occurred within 60 min.
• 98% reduction in the concentration of oxidisable organics was obtained.
• Reaction temperature and oxygen ratio had significant effect.

Of the treatment and conversion technologies used for municipal sludge, wet oxidation has become an important process owing to the characteristics of water as a reaction medium at elevated temperature and pressure. This study aimed to investigate the non-catalytic wet oxidation of municipal sludge and degradation of solids, organic matter and other compounds. A digested sludge consisting of primary and secondary sludges was subjected to 60 min wet oxidation at temperatures ranging between 220 and 240 °C and oxygen to biomass ratios of 1:1–2:1. Wet oxidation was effective at degrading the organic solids, with maximum degradation of 86% for total suspended solids and 96% for volatile suspended solids. The concentration of oxidisable organic matter was reduced by 98% of the untreated sludge. It was found that reaction temperature has the most significant impact on sludge oxidation.