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

ABSTRACT

The graphical abstract shows a laboratory-sized bottle drawing with a stirrer and the legend "activated sludge" on it. A tubing line comes out of it from the top, where it is connected to a syringe with the label H2O2, or hydrogen peroxide. A close up schematic of the sludge-filled bottle is displayed, where a diagram of two microbial processes is shown: first, the production of oxygen (O2) from H2O2 by a bacterial cell, which becomes dissolved oxygen (DO), then another bacterial cell that performs O2 uptake and uses it to consume chemical oxygen demand (COD) into carbon dioxide (CO2). Next to these images are two simulation graphs: one representing DO over time where several peaks representing production and consumption of DO are shown, and the other representing a linear trend of substrate concentration decrease over time.

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.