Mitigating nitrous oxide emissions in wastewater treatment with pure oxygen aeration: A full-scale study

Nitrous oxide (N₂O), a potent greenhouse gas, is a significant byproduct of conventional activated sludge wastewater treatment processes. This study investigates the effectiveness of pure oxygen-based aeration as a strategy to mitigate N₂O emissions from high-strength industrial wastewater. By comparing this approach to traditional air aeration, the research specifically addresses wastewater characterized by elevated COD and ammonia levels. A multi-faceted approach combining computational fluid dynamics (CFD) modeling, drone-based N₂O flux measurements, and in-situ N₂O sensor monitoring was employed to comprehensively assess emission reductions. CFD simulations projected substantial decreases in N₂O emissions, with pure oxygen achieving over a 98% reduction and hybrid systems demonstrating an average 84% reduction compared to conventional surface aerators. Field measurements largely corroborated these simulations, with drone-based quantification showing a 67% N₂O flux reduction under a hybrid aeration strategy, and in-situ sensors frequently detecting negligible N₂O concentrations during stable pure oxygen operation. Furthermore, a carbon footprint analysis revealed considerably lower greenhouse gas (GHG) emissions for pure oxygen systems compared to conventional aeration, positioning it as a sustainable and environmentally sound alternative. Collectively, the findings of this study consistently indicate that the strategic application of pure oxygen is a highly effective N₂O abatement technology for industrial wastewater treatment plants, offering a promising solution for facilities treating high-load process water to meet increasingly stringent GHG emission targets.