Formatted Title
Innovative Underground Skimming Technology for Efficient LNAPL Recovery: A Case Study from Northern France
Background/Objectives
The efficient recovery of light non-aqueous phase liquids (LNAPL) from groundwater presents significant challenges due to diverse soil characteristics, groundwater conditions, and pollutant characteristics. Many conventional recovery methods struggle to address these complexities effectively. However, underground skimming technology has emerged as a promising solution, offering a unique approach to overcome these challenges.
Approach/Activities
This technology's key advantage is the use of skimmers, with a central float being a crucial component. The float, specifically designed for prolonged exposure to hydrocarbons, consistently keeps the skimmer positioned atop the LNAPL layer, even in varying conditions. Remarkably, the float can adapt to groundwater fluctuations of up to 2.5 meters. The skimming process, combined with vacuum pumping, prevents clogging and enables the recovery of LNAPL with differing viscosities. Vacuum pumping in wells creates an imbalance that induces the pollutant to migrate toward it under the influence of gravity, facilitating the comprehensive recovery of the floating layer.
A notable application of this technology is an ongoing project located in Northern France since 2012. This project operates within an industrially restricted site within an ATEX zone. The targeted pollution consists of a complex blend of heavy garage oils, exhibiting a honey-like texture that poses significant recovery challenges with a viscosity of 0.5 Pa.s at 288 K. The groundwater depth varies from 17 to 22 meters, experiencing fluctuations of up to 1.5 meters annually. The installation includes two containers and eight strategically positioned wells across the site. The pollutant is routed to the first container, housing the pumping unit, and subsequently stored in the second container with two 2500 L IBCs. Impressively, over the course of ten years, a total of 22,124 L of LNAPL have been successfully recovered using this technology.
Results/Lessons Learned
This abstract presents a compelling case study demonstrating the effectiveness of underground skimming technology in addressing the challenges associated with LNAPL recovery in complex groundwater environments.