Reducing nitrate contamination in eleectron-donor limited groundwater

Sebastian Holzapfel1, Clara Duffner2, Anja Wunderlich1, Stefanie Schulz3, Lisa Wild1, Michael Schloter3, Florian Einsiedl1
1 Chair of Hydrogeology, Technical University Munich
2 Chair of Soil Science, Technical University Munich
3 Research Unit for Comparative Microbiome Analysis, Helmholtz Centre Munich

14.3 in Young Hydrogeologists Forum

Groundwater is the main source of drinking water in Germany [1]. As a result of intensive agricultural land use, 28% of regularly monitored groundwater wells (EU-Network) in Germany exceed the drinking water limit for nitrate (NO3-) of 50 mg/l [2]. In the investigated area it was shown, that no denitrification takes place due to a lack of electron donors in the aquifer [3]. For this hydrogeological setting a need exists for technologies to remove redox sensitive parameters such as nitrate from such highly polluted aquifers.

Therefore, our project aims to develop a new remediation technology that stimulates in situ hydrogenotrophic denitrification in groundwater. As the solubility of H2 in water is limited the reaction pathway from nitrite (NO2-) to nitrous oxide (N2O) is also supported by an abiotic reaction using a Fe(II)-mineral.

Here we present some results of our incubation and column experiments including the analysis of the microbial community distribution and isotopic compostion of nitrate and nitrite regarding their δ15N which show the potential of hydrogenotrophic denitrification in a nitrate polluted aquifer. Our data serve as the basis for small-scale remediation studies.

[1], 31.03.2018.

[2] Keppner, L.; Grimm, F.; Fischer, D. (2017): Nitratbericht 2016 - Gemeinsamer Bericht der Bundesministerien für Umwelt, Naturschutz, Bau und Reaktorsicherheit sowie für Ernährung und Landwirtschaft. – 138 S., Bonn.

[3] Wild, L., Mayer, B. & Einsiedl, F. (2018): Decadal Delays in Groundwater Recovery from Nitrate Contamination Caused by Low O2 Reduction Rates. Water Resources Research, 54, 12, 9996-10012.