Risk assessment of groundwater contamination during managed aquifer recharge with urban waters in the Geer basin (Liège, Belgium)

Groundwater represents the major source of freshwater. However its availability and sustainability are threatened by several factors such as climate change and anthropogenic pressure. This situation is encouraging research to find alternative methods to store water for a subsequent use such as Managed Aquifer Recharge (MAR). To perform MAR, it is required to consider alternative sources of water. Inventories of MAR projects worldwide indicate that a major part of them use surface waters as infiltrating waters. However, it is not always possible to exploit surface water and some MAR projects require thus to harvest alternative sources of recharge water coming from a relatively urbanized environment such as urban stormwater, treated wastewater, among others. The difficulty with such waters is that there are of unknown composition and might contain potential pollutants, including contaminants of emerging concern (CECs) which pose problems for health and environment. Therefore, this research project aims to develop an innovative screening procedure to identify expected and/or unexpected chemical species present in the potential sources of recharge water intended for MAR. Furthermore, lab experiments will be set up to to evaluate the transport and attenuation parameters that pollutants undergo during their infiltration across geological layers, these latters being key variables and inputs for the following. Finally, recent advances in reactive transport models will be improved to calculate attenuation of pollutants from the recharge system to the aquifer in a risk assessment framework. These last results will be exploited to generate a map delineating the zones which are prone for artificial recharge for a given aquifer with a minimum risk of groundwater contamination. The new developments and findings will be applied to the Hesbaye chalk aquifer, located near the city of Liège in the Geer basin and which constitutes a suitable area to carry out this research project.