Broadband Tunable QCL based Sensor for Online and Inline Detection of Contaminants in Water


AQUARIUS (Broadband Tunable QCL based Sensor for Online and Inline Detection of Contaminants in Water) aims to provide an on- and inline capable mid-IR sensing solution to meet legal provisions for industrial waste water and drinking water monitoring. Significant enhancement in sensitivity will be achieved by further advancement of the laser source and the detector as well as an innovative combination of sample extraction and preparation with polymer functionalized waveguides. The AQUARIUS sensing solution is planned to be developed along the entire value chain towards integration in industrially proven online devices for water control driven by strong industrial commitment in this consortium.

Fresh water is essential for human wellbeing and plays an important role in the world economy, its quality being regulated by national and international legislation. Whereas water is the most abundant substance on the Earth’s surface and essential for all forms of life and used in almost every industrial process, directly or indirectly, fresh water comprises only a small fraction of the total amount of water. Therefore, ensuring good quality of this resource is paramount. The quality of fresh water can differ significantly. The variety and concentration of chemical species in the aquatic systems can be quite diversified, presenting a challenge in terms of both water purification strategies and water quality control. These contaminants are a challenge to the water sector. Thousands of these compounds are used every day and new ones are continually put on the market. Increasingly effective laboratory detection techniques are revealing the presence, in surface water for instance, of low concentrations of contaminants, whose presence was previously unknown. To assure a safe environment, novel water monitoring technologies are needed for all types of water including process water, waste water, sewage as well as drinking water. These new technologies shall enable pervasive water monitoring which can replace and compliment currently employed laboratory based offline methods by online or inline monitoring strategies.

The AQUARIUS project addresses the development of a new generation of photonic sensing solution, in response to the need for pervasive sensing for a safer environment. In particular, components, modules, sub-systems and systems shall be developed for enhanced sensitivity and specificity measurements in water monitoring following the requirements of regulatory bodies, as well as the needs of selected end-users such as waterworks and the oil producing industry. Specifically addressed within the AQUARIUS project is the detection of hydrocarbon contaminations in water (Oil-in-Water contaminations). AQUARIUS aims to provide improved on- and inline sensors in terms of quality and effectiveness, allowing for a reliable and continuous real-time monitoring on site. The new sensors will become possible by the use of a new class of external cavity (EC) quantum cascade lasers (QCL) and detectors.

The following key objectives will be addressed by AQUARIUS:

  • Objective 1: Enhancement of broadband tunable quantum cascade lasers in terms of spectral coverage and noise (TRL increase: from 4 to 6)
  • Objective 2: Realisation of a fully functional spectrometer sub-system consisting of a μEC-QCL and a fast MCT detector including data acquisition (TRL increase: from 3 to 6)
  • Objective 3: Advance Oil-in-Water (OiW) monitoring capabilities from offline (state-of-the-art) to online (TRL increase: from 3 to 6)
  • Objective 4: Test of the online OiW system at industrial end users (TRL 7)
  • Objective 5: Realisation of integrated optical circuits (IOCs) for waveguide based sensing and inline capable sensing configuration (TRL increase: from 2 to 4)
  • Objective 6: Assembly and test of the inline OiW system in a laboratory environment (TRL increase: from 2 to 4)


Work Performed from the beginning of the project up to Month 18:

A first priority of the AQUARIUS project, was to set up a requirements analysis for online and inline oil in water monitoring, which was finalised by the submission of a deliverable. Based on the collected requirements specifications for online and inline oil in water analysis were defined and specifications for subsystem broadband MIR laser spectrometer were set. The specification work included the definition of modules and the description of interfaces. Furthermore, a feasibility assessment was performed and requirements for enhanced water analysis were defined.

Different options for the operational mode of the laser source were integrated. Quantum cascade laser structures were designed and grown and wafer processing was completed. First experiments with a cw MOEMS EC QCL with variable cavity lengths were performed. Strongly improved spectral resolution was demonstrated by transmission measurements on atmospheric water vapor. The most suitable was selected for integration in the preliminary spectrometer sub-systems. A preliminary spectrometer was assembled and developed towards fast recording of broadband spectra.

The different building blocks of the ATR sensing unit are designed and tested. Experiments with porous, 2d hexagonal ordered enrichment layers showed fast diffusion into the layer and fast regeneration. Work on designs for the photonic integrated circuits (PIC) was made and preliminary tests were performed. Interfacing microlenses for the optical coupling to the PICs were designed, realized and experimentally investigated. A first version of a flow cell for the test of the inline sensor was built. A list of samples of interest for the chemometric database was created and the measurement and analysis of those samples with different analytical technique was performed.

Different technical approaches for a potential use in an online extraction module for oil extraction from a water stream were examined and tested. The methods were compared with respect to analysis quality and commercial feasibility. Further, components for system integration are tested for robustness and end user tests are prepared. The results of an extensive inter-laboratory study - to demonstrate the robustness of the liquid-liquid extraction method - were used to update and improve an ASTM standard test method (ASTM D7678).

Meetings with advisory board members were held and numerous valuable details for further work were obtained.

Progress beyond the state of the art so far:

Thanks to results of the feasibility study, feedback from experts leads to promising conclusion regarding AQUARIUS system feasibility and future scaling actions for the technology. There is a high interest in the AQUARIUS technical solution, especially in the field of process control for production purposes, influent and effluent monitoring for the wastewater treatment plants in industrial facilities, and also for cooling water and functional fluids monitoring. Further, an interest in enhanced systems based on the generic AQUARIUS technology platform was identified. External cavity operation of an application-specific laser was demonstrated; subsequent processing of this laser will be done and is expected to deliver improved spectral performance. The spectrometer sub-system will be approved within the application and updated regarding the integrators need.


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