Contaminants of emerging concern in urban Aquifers: are they a pRoblem for groundwater usE? (CARE)

This abstract aims to present the project CARE. Often, urban areas must pump water resources to cover various aspects of the growing urban water demand and as a strategic resource at specific times (e.g., droughts). These considerations lead one to wonder whether urban groundwater can be safely used, including its potential use as drinking water because urban aquifers usually contain a wide range of pollutants (e.g., heavy metals, nutrients, pathogens, and organic contaminants). Currently, there is a growing interest for the contaminants of emerging concern (CECs) (i.e., pharmaceuticals, personal care products, illicit drugs, etc.,) because most of them are not included in the watch lists of priority pollutants due to existing regulatory gap. Moreover, even detected at trace levels (ng/L-µg/L), they might pose ecological risk such as interference with the endocrine system of high organisms, microbiological resistance, accumulation in soil, plants and animals and, the effects of CEC mixtures are assumed to have unforeseen consequences on ecosystems.

Since CECs reach groundwater environment, their attenuation occurs mainly through microbial degradation because adsorption is reversible and only retards the contaminants’ transport. Moreover, although the long residence time of water in aquifers might result in strong attenuation of some CECs, others are persistent in urban groundwater. This requires appropriate understanding of all the processes that control the fate of CECs at field scale but, so far, most research is conducted at the laboratory scale, which misses potential synergetic effects associated with the heterogeneous and complex hydrochemical conditions that are inherent in urban aquifers. Considering the raising demand of secure freshwater and the concurrent increase of CECs use, understanding the factors that most influence their efficient removal in urban aquifers are of paramount importance to assure adequate protection of human health and the environment.

In this context, the main objectives of CARE are to: (1) identify the most suitable conditions that contribute to the natural bioremediation of selected CECs in urban groundwater at field scale and (2) propose and develop solutions for the sustainable management of urban groundwater resources by means of numerical modelling facilitating the decision making and improving its management. A suitable area for CARE is the pilot zone of Sant Adria del Besòs (Barcelona, Spain) because there is a huge amount of urban groundwater is routinely pumped (6 Hm³/y) and discharged into the sewage system. Moreover, our previous investigations have demonstrated the presence of a wide range of CECs in this aquifer reaching concentrations up to 2 µg/L. The main outcome of CARE  will be an integrated method for urban groundwater management using monitoring, measuring and modelling approaches that will support improved decision-making to ensure the long-term availability of water resources to the water authorities. This method can be applied in other urban aquifers.