Effect of Ozonation on Activated Sludge Solubilization and Mineralization

New strategies for sludge stabilization and mineralization need to be developed since the use of sludge in agriculture is debatable and sludge incineration cannot be a systematic solution. Minimization of sludge production should be preferred. In this work, the effect of ozone on activated sludge solubilization and mineralization during batch experiments is assessed by establishing carbon and ozone mass balances. After extended ozonation of the sludge, more than 90% of the particulate carbon is modified. Depending on the experimental conditions, from 15 to 50% is found in a soluble form and from 35% to 95% was mineralized. The VSS/SS ratio decreases from 86% to less than 50% illustrating the sludge mineralization. The initial rate of ozone consumption by the sludge is very high (estimated value: 30 mgO₃/g VSS.min) and corresponds to high rates of carbon solubilization and mineralization. More than 50% of the carbon obtained after ozonation is found to be readily biodegradable using a short-term BOD procedure.