Department Water Resources and Drinking Water

Water Resources & Drinking Water

Our research concentrates on physical and chemical processes in groundwater, surface water and drinking water. We conduct basic and applied research on water resources, water contaminants, and water treatment to contribute to sustainable water management from local to nationwide scales.

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Publications

Nghiem, A. A., Prommer, H., Mozumder, M. R. H., Siade, A., Jamieson, J., Ahmed, K. M., … Bostick, B. C. (2023). Sulfate reduction accelerates groundwater arsenic contamination even in aquifers with abundant iron oxides. Nature Water, 1(2), 151-165. doi:10.1038/s44221-022-00022-z, Institutional Repository

Groundwater contamination by geogenic arsenic is a global problem affecting nearly 200 million people. In South and Southeast Asia, a cost-effective mitigation strategy is to use oxidized low-arsenic aquifers rather than reduced high-arsenic aquifers. Aquifers with abundant oxidized iron minerals are presumably safeguarded against immediate arsenic contamination, due to strong sorption of arsenic onto iron minerals. However, preferential pumping of low-arsenic aquifers can destabilize the boundaries between these aquifers, pulling high-arsenic water into low-arsenic aquifers. We investigate this scenario in a hybrid field-column experiment in Bangladesh where naturally high-arsenic groundwater is pumped through sediment cores from a low-arsenic aquifer, and detailed aqueous and solid-phase measurements are used to constrain reactive transport modelling. Here we show that elevated groundwater arsenic concentrations are induced by sulfate reduction and the predicted formation of highly mobile, poorly sorbing thioarsenic species. This process suggests that contamination of currently pristine aquifers with arsenic can occur up to over 1.5 times faster than previously thought, leading to a deterioration of urgently needed water resources.
Lightfoot, A., Brennwald, M. S., Stopelli, E., AdvectAs project members, & Kipfer, R. (2023). The role of (noble)gases in an As contaminated aquifer. In A. van der Wal, A. Ahmad, B. Petrusevski, J. Weijma, D. Savic, P. van der Wens, … R. Naidu (Eds.), Arsenic in the environment. Proceedings. Proceedings of the 8th international congress and exhibition on arsenic in the environment (As2021) (pp. 23-24). Boca Raton FL: Taylor & Francis. , Institutional Repository

Arsenic (As) contamination of groundwater remains a problem for many of the river deltaic areas
in South-East Asia; where concentrations regularly exceed the 10 mg/L currently recommended by the Word Health Organisation. The focus of this study is to determine inert and reactive gas concentrations in groundwaters at a location where As mobilization is active, to constrain the sites hydrogeology in a highly reducing environment. The small village of Van Phuc, Vietnam, presents an ideal opportunity for such research as is it well studied and accessible, however the As dynamics here are still not well understood. Gas concentrations in 21 wells at varying depths and locations were analysed in Van Phuc, Vietnam, with the miniRUEDI – a portable mass spectrometer (miniRUEDI, Gasometix GmbH, Switzerland) capable of measuring noble gases: He, Ar, Kr, and reactive gases:
CO2, CH4, N2 and O2 in water. First results show As concentrations are highest where CH4 production is observed. Furthermore, evidence of a gaseous CH4 phase being produced within the aquifer is shown through excessive depletion of N2, Ar and Kr elements. Such in-situ formation of gas bubbles can alter the permeability of the aquifer and modify groundwater flow. Simultaneous measurement of both inert and reactive gas species can therefore give an insight to groundwater dynamics of As contaminated aquifers
Wu, R., Podgorski, J., Berg, M., & Polya, D. A. (2023). Pseudo contour maps from logistic regression modelling: case study of groundwater arsenic distribution in Gujarat state, India. In A. van der Wal, A. Ahmad, B. Petrusevski, J. Weijma, D. Savic, P. van der Wens, … R. Naidu (Eds.), Arsenic in the environment. Proceedings. Proceedings of the 8th international congress and exhibition on arsenic in the environment (As2021) (pp. 95-96). doi:10.1201/9781003317395-40, Institutional Repository

Logistic regression modelling is a widely used prediction method to generate probability maps
of groundwater arsenic exceeding a selected threshold concentration. In this study, we converted logistic regression modelled probability maps to a pseudo contour map which comprehensively integrated important information of several probability maps of groundwater arsenic concentrations in Gujarat state, India. The pseudo contour map of groundwater arsenic concentrations clearly and intuitively indicates high groundwater arsenic concentrations (>10 mg/L) occurring in Kachchh District and Banas Kantha District and shows groundwater arsenic concentrations in northern and central Gujarat to be slightly higher than near the western
and eastern borders of the state. The cutoffs, where sensitivity equals specificity, is one of the most appropriate criteria of diagnosis of continuous probability results, better ensuring the accuracy of the generation of a pseudo contour map. However, the probability cutoff of each contour is likely different, so that the generated map is pseudo-contour rather than a contour map.
Stopelli, E., Duyen, V. T., Mai, T. T., Trang, P. T. K., Viet, P. H., Lightfoot, A., … Berg, M. (2023). Interplay of As (im)mobilisation processes in groundwater: learning from hydrochemical investigations. In A. van der Wal, A. Ahmad, B. Petrusevski, J. Weijma, D. Savic, P. van der Wens, … R. Naidu (Eds.), Arsenic in the environment. Proceedings. Proceedings of the 8th international congress and exhibition on arsenic in the environment (As2021) (pp. 21-22). doi:10.1201/9781003317395-9, Institutional Repository

Millions of people worldwide are exposed to arsenic (As) contaminated groundwater. Despite decades of research and evidence of As mobilisation in anoxic aquifers being caused by reductive dissolution of iron minerals, the mechanisms behind the local scale variability of dissolved As remains unclear. Therefore, the trans-disciplinary AdvectAs project investigates the environmental behaviour and spatial heterogeneity of dissolved As in groundwater in the Red River delta, Vietnam. Here we present the results from hydrochemical and water isotope investigations. In particular, we will show how the large As variability (0.1–510 mg/L) is related to consecutive As (im)mobilisation steps, depending on site hydrology, geology and the interplay of Fe, Mn, S and organic matter cycles. Such complexity of (im)mobilisation processes can be simplified in 5 major hydro(geo) chemical zones, providing a conceptual tool with potential for application at other sites in Asia affected by geogenic As contamination of groundwater.

News

Water chemist Urs von Gunten retires

May 8, 2025

Professor Urs von Gunten is one of the world's best-known scientists when it comes to the treatment of drinking water, in particular oxidation and disinfection processes. He has been conducting research at Eawag since 1989, with interruptions; from 2006 he was a titular professor at ETHZ, and from 2011 a full professor at EPFL. Now he is retiring. He retains a consultancy mandate... and the freedom to critically scrutinise the narrative of Switzerland's leading role in research.

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Research Projects

The project investigates what measures are most effective in influencing a river corridor so that river restoration and groundwater flow systems can help to mitigate the effects of floods and droughts.

Record Catchment
This project facilitates the exchange of data, maps and information on geogenic contaminants (focussing on arsenic and fluoride) via the web-based Groundwater Assessment Platform (GAP)

Groundwater Assessment Platform (GAP)
ReCLEAN examines the effects of energy decarbonization on the nitrogen balance within Swiss ecosystems. It will serve as a crucial foundation for developing sustainable policies in Switzerland.

ReCLEAN
By taking into account the interactions between surface waters and groundwater in real time, we improve operational groundwater modeling for drinking water, energy and agriculture.

BRIDGE

More research projects