Groundwater sensors: Dhyana Bharath

Dhyna Bharath is currently doing her PhD here at Wetsus as part of the research theme Groundwater Technology. She shares her enthusiasm about water, and her project on groundwater sensors using optical fibre.

“Apart from the fact that the existence of water is what made the existence of life on earth possible. I am also fascinated by its physical and chemical properties and how much of interdisciplinary fields are dependent on it.”  


I was born and brought up in the southern part of India, Kerala. I graduated from the International School of Photonics, Cochin University of Science and Technology (CUSAT), Kerala, India, with an integrated master’s degree in Photonics. During my bachelor’s and master’s thesis projects, I focused on a specific field in photonics called fibre optics. By the end of my master’s thesis, I decided that I would like to continue learning more and specialize in fibre optic sensors. That’s when I came across the opening of PhD position at Wetsus, which was based on developing optical fibre-based sensors for groundwater quality monitoring. I wanted to improve my experimental research experience and work on a project with social relevance and this position seemed perfect for it. 

I have lived in India for the first 24 years of my life and one of the surprising or maybe I can say a cultural shock I experienced when I moved to The Netherlands is that people can drink tap water, which is impossible there. Lack of water treatment and water quality assessment is very common in many parts of the world, just as in India. I wish there were changes in this aspect. As previously stated, my goal was to acquire experience in areas with social significance. Given that water is a significant global issue, I was delighted to discover a project that combined all my main interests into one. 

Diving Into The Science

Compared to the existing methods of groundwater sensing, optical fiber sensors have the advantages of being immune to electromagnetic interference, and they are small in size and capable of long-distance data transfer and multiplexing. Besides, they have a potentially low cost of fabrication and development, and are safe and non-polluting to the environment. Recent research at Wetsus showed the potential of Fiber Bragg Grating (FBG) based fibre optics-based sensors. Fiber optical cables can be installed vertically into the subsurface with a direct push technique and provide continuous high resolution, real-time information about the aquifer below the surface. FBG sensors were used to monitor groundwater flow, temperature, and compacting effects on soils due to an applied weight or pressure (dynamic consolidation). However, the capabilities of FBG sensors for geohydrological and water quality measurements can be further expanded. Therefore, novel approaches are needed to develop distributed chemical sensing. Ideally, approaches that can be integrated with the distributed sensing of hydrogeological parameters that was done in the previous project. 

This is where my project comes in. We have two main approaches in mind. The first one is where we use a combination of three FBGs with identical central wavelengths together with a tapered/microfiber session in the sensing region to create an effect called the optical Vernier effect (OVE). This approach focuses on improving the sensitivity in comparison to those of the already available FBG-based chemical sensors. The second approach focuses more on improving the selectivity by functionalizing the FBG with a salt-sensitive polymer to detect the presence of specific salts of interest. Integrating the sensor structure developed with appropriate detection and analysis instrumentation, as well as designing the sensor package, are also tasks involved in the project. The final goal is to develop methods to perform in situ real-time monitoring of groundwater aquifer quality.  

A technology I think is the future is a non-invasive non-contact way of detection and analysis, which is being studied and applied a lot more these days. The use of light signal as in my work could be considered a part of it. 

Final Remarks

There’re a lot of things that I could say that I love about doing research. First, the learning and discovering part of it. We are exposed to multidisciplinary topics and difficult situations where we have opportunities for learning and personal growth. The second thing that came to mind is the sense of accomplishment that one can feel by successfully completing a research project, publishing a paper, or making a significant contribution to your field. I also like that it is more or less flexible when it comes to the pace of work or choosing the priority of tasks is in your own hands most of the time. 

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