Review on groundwater circulation wells (GCWs) for aquifer remediation: State of the art, challenges, and future prospects

Groundwater circulation wells (GCWs) are emerging as an alternative technology for groundwater remediation. GCWs have also been used for the hydraulic characterization of aquifers, which is a necessary step toward remediation. However, the wide range of academic research on recirculating wells is quite fragmented and does not facilitate the consolidation of the findings gained in the past 30 years. Given the absence of a review on GCWs in the literature, this article aims to provide a critical overview of this topic. The analysis of pertinent literature identifies three main fields where recirculating wells are addressed: (1) mathematical models, (2) laboratory studies, and (3) field applications. The categorization of studies on GCWs within the aforementioned thematic areas highlights the main findings, contradictory results, technological limitations, implications, and opportunities for future research. The literature review introduces studies that debate the mathematical models governing the flow driven by GCWs and details the advantages and disadvantages of numerical simulations and laboratory testing. The discussion of field applications emphasizes the flexibility of recirculation systems, the possibility of coupling with other remediation technologies and numerous reagents, the targeted flushing of contaminated areas, the mobilization of pollutants from low-permeability areas triggered by hydraulic manipulation, and the reduction in remediation time and water consumption over traditional systems such as pumpand-treat (P&T). This review represents a summary in the current state of knowledge, challenges, and potential of GCWs for groundwater remediation. It guides future efforts and endeavors to fully harness the potential of GCWs, offering additional ideas and research insights.