Modelling the combination of aquifer thermal energy storage with remediation of contaminated groundwater

In the scientific park of Leipzig an Aquifer Thermal Energy Storage (ATES) system is planned in combination with the remediation of groundwater contaminated with chlorinated volatile organic compounds.

During the operation of the ATES system a two-well system is used. The cold groundwater is extracted from one well, and reinjected after heating up through the other well into the aquifer as storage. Later this pumping mode will be reversed and the heated-up groundwater will be extracted as a heating source.

In the most of ATES system, hot water is injected into aquifers at temperature lower than 25°C, while the planned system will inject at temperature of up to 80°C. This leads to a more significant influence on the chemical composition of the groundwater than with lower temperature ATES systems. Additionally laboratory tests from a previous project also show a drastic change in the microbiological biome at 45 and 60°C.

To facilitate the understanding of such impacts, a simplified 2D numerical model has been constructed, simulating both hydraulic and heat transport process in the aquifer. The model is currently being used as a planning tool to predict the propagation of the thermal plume, as well as designing the pumping rate of the circulation system. The model results already show a larger thermal-affected zone due to the high-temperature injection compared to low temperature ATES system.

Future application of the model is to investigate the impact of thermal signal on the mobilization of the contaminants, and also its contribution to the natural attenuation through change in the microbiological biome and activity, which determines the degradation rate in most cases. The overall goal of the project is to develop a fully coupled THC model that will be used to simulate the thermal, hydraulic and chemical processes associated with the thermal usage of a contaminated aquifer in urban areas.