Researchers sound out the effects of geothermal heat pumps on groundwater

Dübendorf ZH – Empa and Eawag are researching the effects of borehole heat reservoirs on the chemical composition of groundwater and the microorganisms living in it. The geothermal probes used can heat the ground to up to 50 degrees Celsius.

Researchers at the Swiss Federal Laboratories for Materials Science and Technology (Empa) and the Swiss Federal Institute of Aquatic Science and Technology (Eawag) are investigating how the use of borehole heat exchangers affects the chemical composition of groundwater and the microorganisms living in it. The research should also shed light on whether the heat effect in the soil contributes to the formation of gases such as oxygen, methane or CO2.

As part of the Aquifer Reaction to Thermal Storage (ARTS) research project, three Eawag groundwater monitoring points have been set up on the Empa-Eawag campus in Dübendorf, Empa and Eawag announced in a press release. Over the next three years, samples of groundwater are to be taken continuously before, during and after it comes into contact with the geothermal probes. The borehole heat accumulators installed in Dübendorf can heat the ground locally to up to 50 degrees Celsius.

The samples are analyzed in a mass spectrometer developed at Eawag, the so-called Mini-RUEDI. "For the next three years, mini-RUEDI devices will measure the dissolved gases in the groundwater every hour, while 2.4 liters of water are pumped through the mass spectrometer every minute," explains Joaquin Jimenez-Martinez, head of the project and researcher in Eawag's Water and Drinking Water department, in the press release. The samples are also analyzed by researchers from Eawag's Environmental Microbiology and Aquatic Ecology departments. The aim here is to clarify how temperatures affect the type, number and distribution of organisms in groundwater. ce/hs

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