KONATES: A Model Experiment on the Use of Contaminated Aquifers for Heat Management with ATES Plants - Microbiological and Isotopic Investigations

ATES (Aquifer Thermal Energy Storage) is a CO₂-free technology for seasonal heating or cooling of buildings based on the storage and recovery of thermal energy in the aquifer. Since aquifers in urban areas are often contaminated with organic pollutants, the application of ATES raises the research question whether this type of heat management can accelerate natural attenuation processes. In the KONATES project, we are investigating how the storage of warm water (70°C) in an aquifer contaminated with trichloroethene (TCE) impacts the aquifer’s microbiome structure and its potential for reductive dehalogenation of TCE. In laboratory experiments we could demonstrate that the native microbiome of the contaminated aquifer can reductively dehalogenate TCE within a temperature range typical for low-temperature ATES (12°C to 25°C). However, these processes are significantly inhibited or entirely absent at temperatures characteristic for intermediate- to high-temperature ATES (30°C to 70°C). The effect of hot water (70°C) injection into an TCE contaminated aquifer on the microbial community composition, with specific focus on thermophiles and organohalide respiring bacteria, was investigated. Additionally, the extent of TCE reductive dehalogenation in the contaminated aquifer and the impact of ATES on this process was assessed using dual-element compound-specific stable isotope analysis, allowing distinguishing from e.g. dilution effects due to mixing of water.