Anaerobic Digestion of Thermo-Oxidized Excess Municipal Sludge

The effect of a thermo-oxidative co-treatment placed between the two reactors of two-stage anaerobic digestion of excess municipal sludge was studied. The oxidant used was hydrogen peroxide $({\rm H}_{2}{\rm O}_{2})$ , and moderate temperatures below the boiling point of water were considered. The first experiment was to elucidate the effect of two different temperatures (65 and 90°C) of oxidation using a constant oxidant dose of 1.0 g ${\rm H}_{2}{\rm O}_{2}/{\rm g}$ influent volatile suspended solids $({\rm VSS}_{\text{influent}})$ . The use of thermo-oxidative co-treatment increased overall solids destruction by 24.9 and 33.5%, respectively, when operating at 65 and 90°C, respectively. Because of this significant effect of temperature on the performance of the process, a second experiment was conducted using the higher temperature of 90°C while decreasing the hydrogen peroxide dosage to 0.5, 0.25, and 0.1 g ${\rm H}_{2}{\rm O}_{2}/{\rm g}\ {\rm VSS}_{\text{influent}}$ . An increase in solids destruction of 13.9, 18.9, and 25.6% was observed when the thermo-oxidative co-treatment was used using oxidant dosages of 0.1, 0.25, and 0.5 g ${\rm H}_{2}{\rm O}_{2}/{\rm g}\ {\rm VSS}_{\text{influent}}$ , respectively.