DELINEATING MECHANISMS OF TRACE ELEMENT MOBILIZATION DURING MANAGED AQUIFER RECHARGE

Groundwater from the Potomac Aquifer in the Atlantic Coastal Plain Physiographic Province in eastern Virginia is a heavily used resource for homes and industry. The Hampton Roads Sanitation District developed the Sustainable Water Initiative For Tomorrow (SWIFT) program, a managed aquifer recharge (MAR) operation involving the injection and storage of secondary water (treated wastewater effluent) into the Potomac Aquifer. The goals of this MAR operation are to improve the declining groundwater levels and yields, saline intrusion, and land subsidence in the Hampton Roads area. However, one potential risk of MAR is that the injection of recharged water differing from the ambient groundwater can alter the native geochemistry, which can result in the mobilization of naturally occurring toxic trace elements, such as arsenic and manganese, into groundwater. Research to date has shown that there are several possible biogeochemical mechanisms that contribute to the release of trace elements to groundwater during MAR. The objective of our research is to elucidate the mechanisms that can mobilize trace elements to groundwater in the Potomac Aquifer during MAR. To achieve this, we will utilize batch experiments to test different hypotheses of trace element mobilization from aquifer sediments. In addition, we are planning large-scale column experiments to define an experimental approach for evaluating mobilization potential using aquifer sediment samples under different operational conditions. Results from our research can help evaluate the risks of trace element mobilization at MAR sites.