Temperature-induced impacts on groundwater quality and arsenic mobility in anoxic aquifer sediments used for both drinking water and shallow geothermal energy production

The element-release mechanisms of two pyrite-bearing siliciclastic rocks from the North German Basin at temperatures up to 90 °C under oxic and anoxic conditions

“…However, the workflow is capable of reliably excluding risk factors, such as contaminant release. For example, Bonte et al (2013a) and Javed and Siddique (2016) reported the release of As from rock samples in experiments with elevated temperatures, and showed that the mobilized As had been sorbed to the rock matrix. This could be ruled out for both rocks studied in the present work, since they contained only reducible and oxidizable As, which remained immobile during leaching tests.…”

“…Subsequently, physicochemical water properties like pH or redox potential may change, and mobilized elements may precipitate and clog the aquifer, block pipes, or form coatings that reduce the efficiency of the heat exchanger. If the ATES system is built in an aquifer that serves as drinking water supply as well, the release of toxic elements such as heavy metals need to be avoided (Bonte et al 2013a, Possemiers et al 2014. Altered water properties may promote corrosion or induce subsequent fluid-rock interactions (Allen et al 1984;Frick et al 2011;Palmer et al 1992).…”

“…Distinct cation release was only observed at 70 °C. Bonte et al (2013a) performed column experiments with anoxic unconsolidated aquifer sands between 5 and 60 °C and reported significant increases in element solute concentrations at 60 °C, while the sediment remained only slightly reactive at lower temperatures. Consistent elementrelease patterns were only partially observed, e.g., for silicium and potassium.…”

Preface: Hydrogeology of shallow thermal systems

“…Furthermore, other associated environmental risks due to the operation of such systems also have to be considered (Bonte et al 2011). For example, the use of higher injection temperatures could substantially impact and alter the groundwater ecosystem (Brielmann et al 2009) and the hydrogeochemistry of the aquifer (Bonte et al 2013). Hence, only a few moderateand high-temperature ATES are currently operational worldwide and few have been studied in detail like the system implemented for the German parliament building in Berlin (Kabus and Seibt 2000).…”

Consequences and mitigation of saltwater intrusion induced by short-circuiting during aquifer storage and recovery in a coastal subsurface

“…Additionally, they are perforated for exploitation of deep fossil and geothermal energy and traditionally used for abstraction of drinking and irrigation water. The increased use of the subsurface can lead to interference among aquifer storage systems (e.g., Bakr et al, 2013) or affect the groundwater quality (Bonte et al, 2011b(Bonte et al, , 2013Zuurbier et al, 2013b). These consequences form relevant fields of current and future research.…”