Ali et al. (2026) Mitigating nitrous oxide emissions in wastewater treatment with pure oxygen aeration: A full-scale study

Identification

• Journal: The Science of The Total Environment
• Year: 2026
• Authors: Izba Ali, Rudy Lamond, Roel Boussemaere
• DOI: 10.1016/j.scitotenv.2026.181457

Research Groups

• Air Liquide Innovation Campus Paris, Les Loges-en-Josas, France
• Air Liquide, Brussels, Belgium
• AM-Team, Ghent, Belgium (CFD Modeling)
• Explicit, Copenhagen, Denmark (Drone-based measurements)
• Unisense, Aarhus, Denmark (Sensor technology)

Short Summary

This study demonstrates that utilizing pure oxygen aeration instead of conventional air-based systems in industrial wastewater treatment significantly mitigates nitrous oxide ($N2O$) emissions. Through full-scale field measurements and CFD modeling, the research found that pure oxygen systems can reduce $N2O$ flux by $67\%$ to over $98\%$ while simultaneously lowering the process energy footprint.

Objective

• To evaluate the effectiveness of pure oxygen-based aeration as a targeted strategy to mitigate $N_2O$ emissions in high-strength industrial wastewater treatment compared to traditional air aeration.

Study Configuration

• Spatial Scale: Full-scale industrial wastewater treatment plant at a composting facility in Hoek Van Holland, Netherlands (bioreactor volume: $5700\text{ m}^3$; diameter: $37\text{ m}$; height: $5.3\text{ m}$).
• Temporal Scale: Continuous one-year monitoring of influent characteristics; specific drone-based measurement campaigns and $22–24$ hour sequencing batch reactor (SBR) operational cycles.

Methodology and Data

• Models used: Computational Fluid Dynamics (CFD) using a multiphase Eulerian model integrated with a proprietary ASMG1-based biokinetic model to simulate four $N_2O$ production/consumption pathways.
• Data sources:
  • Drone-based Flux Measurement (DFM) for fugitive gas quantification.
  • In-situ electrochemical microsensors (Unisense) for real-time dissolved $N_2O$ monitoring.
  • Carbon footprint analysis using IPCC (2007/2024) global warming potential factors and IEA grid emission factors.

Main Results

• Emission Reduction: CFD simulations predicted a $>98\%$ reduction in $N_2O$ for pure oxygen systems and an $84\%$ reduction for hybrid systems compared to surface aerators.
• Field Validation: Drone measurements quantified a $67\%$ reduction in $N2O$ flux under hybrid aeration ($0.14\text{ kg }N2O/h$) compared to air-only aeration ($0.41\text{ kg }N_2O/h$).
• Hydrodynamics: Pure oxygen injection improved dissolved oxygen (DO) distribution and eliminated localized oxygen-limited "hotspots," which are primary drivers of $N_2O$ formation via nitrifier stress.
• Energy Efficiency: The pure oxygen system (Ventoxal) achieved a Standard Aeration Efficiency (SAE) of $3.25\text{ kg }O2/kWh$, significantly outperforming conventional surface aerators ($1.5\text{ kg }O2/kWh$).
• Carbon Footprint: Carbon footprint analysis revealed that pure oxygen systems generate substantially lower total $CO_2$-equivalent emissions due to reduced gas stripping and higher operational energy efficiency.

Contributions

• Provides the first full-scale, multi-methodological evidence (CFD, drone, and sensors) for pure oxygen as a viable $N_2O$ mitigation technology.
• Demonstrates that pure oxygen aeration offers a synergistic benefit: improving core treatment efficacy (nitrification) while simultaneously meeting stringent greenhouse gas reduction targets.
• Establishes a proof-of-concept for the transferability of high-strength industrial wastewater solutions to municipal sectors, particularly where on-site oxygen is available (e.g., for ozonation).

Funding

• Research and funding provided by the Air Liquide Paris-Saclay Research Centre.

Citation

@article{Ali2026Mitigating,
  author = {Ali, Izba and Lamond, Rudy and Boussemaere, Roel},
  title = {Mitigating nitrous oxide emissions in wastewater treatment with pure oxygen aeration: A full-scale study},
  journal = {The Science of The Total Environment},
  year = {2026},
  doi = {10.1016/j.scitotenv.2026.181457},
  url = {https://doi.org/10.1016/j.scitotenv.2026.181457}
}

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