Kinetic response of hydrogen peroxide conversion to oxygen and subsequent biological respiration during activated sludge treatment.

For decades, activated sludge has been utilized to remove organic components from wastewater. In this process, required oxygenation is typically energy-intensive. Hydrogen peroxide (H2O2) poses an energy-saving alternative to generate catalase-driven oxygen (O2). However, assessing its viability in activated sludge has been limited to stoichiometric respiration demands. In this study, specific H2O2 concentrations were tested on artificial wastewater to obtain predictable kinetic rates for peroxide addition, O2 production, and substrate removal by a native sludge community. Batch injections of 25-50 mg H2O2/L result in fast conversion to O2 whose response could be modeled through Michaelis-Menten kinetics. Calculated production rates are at least tenfold higher than oxygen uptake rates, with the latter comparable to typical AS systems. Based on consumption rates, continuous feeding (28 mg H2O2/g MLSS-h) achieved complete substrate conversion at 1.1 g COD/L-d. Higher feeding rates eventually resulted in minimal O2 uptake and incomplete substrate removal, which recovered after stopping H2O2 feeding. Comparatively, nitrification was not inhibited by increased peroxide feeding. Our results provide consistent O2 generation and direct responses to leverage direct H2O2 utilization in existing WWTPs, where the experimental framework determines relevant feeding rates to be met by in situ H2O2-producing technologies during activated sludge treatment.