In an era marked by an urgent need to curb greenhouse gas emissions, the wastewater treatment sector stands as a critical battleground. Wastewater treatment plants (WWTPs) are known contributors of a variety of greenhouse gases (GHGs), including methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O). These emissions predominantly arise from the breakdown of organic matter during biological treatment processes within aeration tanks and sludge digesters. Despite the sector’s environmental significance, monitoring these emissions has long been challenged by technological and methodological limitations. Traditional point-sampling techniques often provide fragmented snapshots, insufficient to capture the complex, dynamic nature of gas releases from heterogeneous sources scattered throughout WWTPs.
Addressing these challenges, a pioneering team of researchers from Radboud University in the Netherlands has developed an ultra-broadband coherent open-path spectroscopy (COPS) system designed to revolutionize real-time gas monitoring in wastewater treatment environments. This innovative instrument utilizes a mid-infrared light source with an unparalleled spectral bandwidth ranging approximately from 2 to 11.5 micrometers. The broad spectral range enables simultaneous, high-resolution detection of multiple gases, including methane, carbon dioxide, nitrous oxide, ammonia (NH₃), carbon monoxide (CO), and water vapor (H₂O). Unlike traditional methods reliant on discrete point measurements, the COPS system captures the integrated concentration profiles of gases over extended atmospheric paths in real time, providing a highly sensitive and temporally resolved picture of emissions.
The deployment of the COPS system atop an aeration tank at a Dutch WWTP exemplifies its advanced capabilities. Methane and carbon dioxide, both key indicators of organic matter decomposition and process aeration efficiency, were continuously monitored. The system revealed clear correlations between aeration schedules and fluctuations in gas concentrations, underscoring its potential to directly inform operational adjustments to mitigate emissions. Notably, nitrous oxide and ammonia levels remained relatively stable during the observation period, providing further insight into emission dynamics that are typically difficult to capture with conventional methods.
Technically, the COPS system operates by transmitting a coherent mid-infrared laser beam across an open atmospheric path above the wastewater treatment tank. As the light traverses this path, it interacts with airborne gas molecules, which absorb specific wavelengths corresponding to their unique vibrational and rotational transitions. The system’s detectors analyze the absorption spectra with high precision, enabling quantitative determination of multiple gas concentrations simultaneously. This coherent spectroscopy approach maximizes signal-to-noise ratios and improves sensitivity well beyond classical optical absorption techniques, such as non-dispersive infrared sensors or tunable diode laser absorption spectroscopy.
Beyond improving sensitivity and temporal resolution, the open-path design of the COPS system addresses limitations inherent in traditional point samplers. Point sensors provide data representative of gas concentrations at a fixed location, often failing to capture emissions dispersed over large or spatially complex sites. The COPS system’s extended beam path effectively averages emissions over an area, resulting in a more cohesive and comprehensive understanding of gaseous outputs. This spatial integration is particularly advantageous in WWTPs where emission sources—including open tanks, sludge storage, and aeration basins—are distributed and dynamically changing.
The significance of this technology extends beyond academic interest into practical environmental management and regulatory compliance spheres. Real-time analytics afforded by the COPS system enable WWTP operators to identify emission spikes immediately and evaluate the effectiveness of operational changes or mitigation technologies. With enhanced emissions quantification, facilities can more accurately report environmental performance and meet increasingly stringent regulatory standards. This can further guide long-term strategies to reduce greenhouse gas footprints and promote sustainability within the wastewater sector.
Dr. Simona Cristescu, a leading analytical chemist and co-developer of the COPS system, highlights the transformative impact of this breakthrough: “By enabling simultaneous, precise detection of a multitude of greenhouse gases with negligible interferences, our system offers a leap forward in our ability to monitor and understand emissions from complex industrial sites. This capability empowers more informed decisions towards emission reduction and sustainability.”
The research exemplifies a successful collaboration between academia and industry stakeholders, leveraging state-of-the-art laser technology and environmental science. Funding support from the EU Horizon2020 TRIAGE Project and Dutch water authorities underlines the priority of developing robust solutions for environmental monitoring challenges. The study’s findings, published in the journal Environmental Science and Ecotechnology, showcase not only technological innovation but also the potential for scalable applications across other sectors burdened by complex emission profiles.
Industrial manufacturing, agricultural facilities, and even atmospheric science research stand to benefit from this spectral monitoring advancement. As the technology matures, adaptations could enable remote sensing of greenhouse gases at regional scales, offering policymakers and environmental agencies a powerful tool to verify emission inventories and support climate action plans. The ability to conduct continuous, non-invasive, and multi-gas monitoring with minimal maintenance and operational overhead makes the COPS approach particularly appealing for diverse deployment scenarios.
However, challenges remain to fully integrate this technology into routine operational frameworks. Calibration protocols, data interpretation algorithms, and cost scalability must be further refined to ensure widespread adoption. Additionally, integrating COPS measurements with digital twins and process control systems could unlock real-time feedback loops, optimizing emission management strategies dynamically. Such advancements would position WWTPs and related industries at the forefront of green technology adoption.
In conclusion, the ultra-broadband coherent open-path spectroscopy system represents a watershed moment in environmental gas monitoring, bridging the gap between laboratory-grade analytical precision and field applicability. This real-time multi-gas detection platform not only advances scientific understanding of emissions from wastewater treatment but also lays the groundwork for smarter, sustainable industrial practices worldwide. As environmental pressure intensifies and regulatory landscapes evolve, innovations like the COPS system will be indispensable in achieving meaningful greenhouse gas mitigation and environmental stewardship.
Subject of Research: Not applicable
Article Title: Ultra-broadband coherent open-path spectroscopy for multi-gas monitoring in wastewater treatment
News Publication Date: 17-Mar-2025
Web References: http://dx.doi.org/10.1016/j.ese.2025.100554
References: 10.1016/j.ese.2025.100554
Image Credits: Environmental Science and Ecotechnology
Keywords: Environmental monitoring
