Transport Characteristics in a 3D Groundwater Circulation Flow Field by Experimental and Numerical Investigations

Abstract

The groundwater circulation well (GCW) is one of the important in situ techniques used for the remediation of volatile organic contaminants (VOCs) in groundwater. The hydraulic flow field of the GCW permits physical and biological remediation of the saturated as well as the unsaturated subsurface region. The GCW is designed to remove VOCs from the groundwater by transferring the contaminants from the aqueous phase to the gaseous phase and subsequently treating the resulting air stream through carbon adsorption units. As the flow phenomena surrounding a GCW in a heterogeneous aquifer are very complex, the characterization of transport is very difficult. This paper presents the analysis of experimental tracer transport in a three-dimensional (3D) flow field induced by a GCW in an artificial aquifer at the research facility for groundwater and subsurface remediation, Versuchseinrichtung zur Grundwasser und Altlastensanierung (VEGAS), at University of Stuttgart, Germany. The circulation flow field within a heterogeneous aquifer was investigated by a partial tracer injection tracing a certain stream tube of the flow field. The controlled extraction of the tracer was rather difficult because of the aquifer heterogeneity. A numerical model has been built up and simulation has been carried out for flow and transport processes. Experimental and simulated breakthrough curves were compared and the influence of aquifer heterogeneity on the transport has been brought out. The present study reveals the various flow and transport characteristics in a circulation well field giving further insight into the remediation process by the GCW.