Zero-Valent Iron Permeable Reactive Barriers for In Situ Treatment of Organics and Metals in Groundwater

Permeable reactive barriers (PRBs) are designed to be more permeable than the surrounding aquifer matrix, passively treating groundwater readily flowing through the material under the natural gradient, without significantly altering groundwater hydrogeology or plume morphology. A variety of materials can be utilized as a permeable barrier material, including zero-valent iron (ZVI), carbonaceous sources, alkaline materials, granular activated carbon, zeolites, and new materials. This chapter provides a concise and practical guide to the implementation of ZVI PRBs for the treatment of chlorinated aliphatic hydrocarbons and certain redox-reactive metals, such as chromium and arsenic. It details the application stages for this groundwater remediation method, including the initial feasibility assessment, site data collection, laboratory treatability studies, development of design parameters, PRB construction techniques, and long-term performance monitoring. The ZVI deactivation process is dependent on the type and mass flux of the passivating constituents. Sampling within and around a PRB requires special techniques to collect representative samples.