Reactive barriers: hydraulic performance and design enhancements.

Area of Science:

• Environmental Engineering
• Hydrogeology
• Geochemistry

Background:

• Groundwater remediation is a significant global industry.
• Permeable reactive barriers (PRBs) are a key technology for in-situ groundwater treatment, offering an alternative to traditional pump-and-treat methods.
• Improving the hydraulic performance of PRBs is crucial for maximizing their effectiveness and economic viability.

Purpose of the Study:

• To optimize the hydraulic performance of permeable reactive barriers (PRBs).
• To balance capture, residence time, and PRB longevity for cost-effective design.
• To identify design enhancements that improve PRB hydraulic efficiency and reduce the need for oversizing.

Main Methods:

• Three-dimensional particle tracking was employed to estimate capture zone and residence time distributions.
• Volumetric flow analysis was utilized to assess flow distribution across PRBs and identify flow regimes impacting permeability or reactivity.
• Hydraulic performance of standard PRB designs was analyzed.

Main Results:

• Capture zone measurements extended below partially penetrating PRBs and upgradient from the influenced aquifer portion.
• Significant variations in residence time and capture zone were confirmed in standard PRB designs.
• PRB design enhancements, including customized downgradient gate faces, velocity equalization walls, deeper funnel emplacement, and hydraulic conductivity ratio manipulation, were identified as effective for controlling residence time and capture variation.

Conclusions:

• Standard PRB designs exhibit considerable hydraulic performance variability, potentially necessitating oversizing to meet contaminant concentration standards.
• Strategic design modifications, such as tailored gate faces and internal flow control structures, can significantly enhance PRB hydraulic performance.
• Optimized PRB designs offer a more efficient and cost-effective approach to groundwater remediation by minimizing variability and improving contaminant capture and treatment.