7.9 Sensor for selective, continuous and in-line measurement of impurities in water

Water is a very effective solvent and easily takes up impurities. Compounds coming from urban, industrial and agricultural areas end up in groundwater and surface water, and eventually in drinking water as both water bodies are used for production of drinking water. Some of those compounds might reach levels above limits set by (health) regulations. For instance nitrate, phosphate, pesticides and herbicides from agricultural areas, pharmaceuticals from urban areas and from industrial areas chemicals such as perfluorinated compounds (PFCs) which are difficult to degrade.
Concentrations in surface and ground water are mainly monitored by sampling. This will give accurate results, but these data have very low temporal and spatial resolution. Peak events are easily missed and polluters are hard to identify. In-line monitoring improves the temporal resolution, and applying multiple sensors in a network improves the spatial resolution. Both help to enforce the water quality and identify possible polluters. This requires the development of in-line low-cost compound selective sensors. Additionally, this type of sensors find application in optimization of waste water treatment plants, individual waste water treatment installations and various industrial processes.

Research challenge
The approach in this project is to develop a low-cost in-line compound selective sensor. There are basically three options: 1) selectively capturing or isolating the compound of interest, or 2) identifying the chemical structure of the compound in solution, and 3) miniaturizing laboratory equipment. For option 1, ion selective electrodes (ISE) are the most suitable for low-cost applications. Unfortunately current anion selective electrodes are not very selective; other anions interfere with the measurements according to the so called Hofmeister series. Phosphate is on the wrong side of this series and has large interference from other ions. Beating the Hofmeister series is required to use this method. Option 2 can be done by using light. The molecular bonds interact (vibrate) with incident light. Resulting spectra might identify and quantify the concentration of the compound of interest. Optics are getting cheaper and better each year, but might still be too costly for this application. Miniaturisation and cheap solutions are the challenge here. The same challenge holds for option 3. Option 1 and 2 may require the integration of existing sensors on the market into the sensor concept (sensor fusion).
The project comprises a definition phase in which the most promising approach to realize an economically feasible in-line sensor is defined. After the definition phase, focus will be on the realization of a minimum viable sensor system, iteratively building a set-up, testing and improving the sensoring principle.

We are looking for a candidate with an MSc degree in the field of chemistry, physics or electrical engineering and interested in the combination of practical and theoretical work. A multidisciplinary background is required and experience with electronics, measurements and programming is helpful.

The research project is part of the Wetsus research theme Sensoring. The following companies are part of the theme: Grundfos (, Evoqua (, Easymeasure (

Promotor: tbd
Wetsus supervisors: dr. ir. Martijn Wagterveld, dr. ir. Mateo Mayer
For more information contact Martijn Wagterveld:

Please do NOT send your CV directly to this email address. Only complete applications sent via the website will be evaluated (How to Apply).

Wetsus, Leeuwarden, The Netherlands

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