Tracing known and unknown contaminants
Non-target screening protects drinking water quality
Water companies, water laboratories, government representatives and KWR gather in 2014 to discuss the results of research into so-called “suspect screening” of chemical water quality. The suspect screening or non-target screening approach is a new technology, developed by Vitens and KWR. A combination of liquid chromatography, high-resolution mass spectrometry and software to interpret large volumes of measurement data is employed to register the presence in water of a broad palette of chemical substances in low concentrations. Suspect screening assists water companies monitor their water quality and respond to changes in a timely manner.
Beginning in the 1970s, an increasing number of substances started appearing in drinking water sources, including pesticides, PAHs, benzene and hormone disruptors. This is why the Dutch Decree on Water Quality includes regulations for the periodic monitoring and control of the presence of these so-called “target substances”. “One can presume that some other compounds used in industry, agriculture or households, get through to the water,” says KWR researcher Stefan Kools. “Moreover, substances that are unknown to us also certainly end up in surface water and groundwater; every day, tens of new substances are put onto the market and probably into the environment. Since water companies want to be able to intervene before problems with drinking water quality arise, we have over the past few years – together with Vitens, WLN and others – worked on the possibility of the suspect screening of chemical water quality, which would enable the registration of all the substances present.” As Bendert de Graaf of Vitens puts it: “By reacting to changes in the complete chemical composition picture, you can trace contaminations by both known and unknown substances. You can then work out what has changed in the chemical composition, where the changes originate and how serious they are for water quality.”
Thanks to liquid chromatography and high-resolution mass spectrometry, it is possible to extract far more information from water samples
Liquid chromatography combined with high-resolution mass spectrometry
Thanks to new developments in liquid chromatography and high-resolution mass spectrometry, it is now possible to extract far more information from water samples. KWR has applied these techniques for almost ten years, and has optimised them for use in the detection of very low concentrations of a wide variety of substances. In the meantime, the techniques have evolved so much that Vitens and the WLN laboratory want to apply suspect screening to water from vulnerable abstraction sites: usually groundwater abstraction sites where soil pollution is present in the vicinity. Vitens has also acquired high-quality mass spectrometers for the purpose. “We monitor the water quality from vulnerable abstraction using observation wells that surround the abstraction area,” explains Bendert de Graaf. “If the chemical water quality changes where the monitoring wells are located, we can check to see what the matter is before the changes appear in the abstraction wells located farther away.”
Suspect screening offers yet another important advantage: it allows you to look into the past. Huge databanks have been built with measurement data from water samples taken over the past few years. These data are in part raw data: in far from all the cases have the precise substances been determined that correspond to the “peaks” in the exact masses diagrams. The data volume is simply too big for this to be done. But whenever a problem substance does turn up today, a specific search for its presence in the earlier samples can be conducted. “Good software that enables the routine handling of such large data volumes is indeed needed for application in practice,” says Bendert de Graaf.
This research is concluded on 3 December 2014 with a workshop with the participation of project partners, Vitens and WLN, as well as representatives of other interested parties: water laboratories (HWL, Aqualab-Zuid), the Institute for Environmental Studies (IVM), the Dutch Directorate for Public Works and Water Management (Rijkswaterstaat), the Association of River Water Supply Companies (RIWA), and the National Institute for Public Health and the Environment (RIVM). They discuss their experience and the results with the analysis technique, quality assurance, the use of software to analyse big volumes of data, data storage and international developments. They also jointly look to the future, when the non-target screening approach could well become anchored in legislation as a means for water companies to satisfy the legal obligations of the Dutch Decree on Water Quality.
© 2017 KWR Watercycle Research Institute
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Senior scientific researcher
Manager Chemical Water Quality and Health and Project Manager