Permeable Reactive Barrier

Permeable Reactive Barrier

Introduction

A permeable reactive barrier (PRB) is a zone of reactive material placed underground to intercept and react with a contaminant plume in ground water. Typically, PRBs are emplaced by replacing soils with reactive material in a trench cut through a contaminated ground water aquifer. PRBs can also be installed above ground to provide access to the treatment media. Above ground systems are also referred to as ground water treatment cells (EnviroMetal Process , http://www.eti.ca/theprocess/html).

PRBs can be installed using several methods including trenching or through injection wells. Treatability studies are typically conducted to evaluate the performance of reactive materials to treat ground water under site-specific conditions. Selection of material for the barrier is based on results of these treatability studies. Computer modeling is used to simulate the complex chemical reactions that occur in a PRB.

The material in the barrier is permeable, which allows the ground water or contaminant plume to flow through the barrier. When the targeted contaminant encounters the reactive material in the barrier, a chemical reaction occurs with the barrier material that results in adsorption, mineral precipitation, or degradation to a harmless compound (Industrial Site, http://www.eti.ca/FieldReports/sunnyvale.html). Reactive barriers that do not incorporate motors or mechanical devices are considered passive treatment. PRBs are widely used to control organic contamination in ground water; however, less effort has been made to apply the technologyto metal and radionuclide contaminants. This technology may be more cost effective than pump-and-treat methods.

Discussion

Permeable reactive barriers are a practical, low cost alternative to traditional pump and treat methods. After very extensive site characterization, the location, design, thickness and length, and reactive media of the barrier can be determined. A common reactant is zero valent iron because of it's availability and effectiveness in removing many contaminants but specifically chlorinated solvents. Advantages of permeable reactive barriers are their cost effectiveness, ability to treat multiple contaminants, the limiting of cross contamination as well as many others. The disadvantages are that they are restricted to shallow plumes, loss of reactant potency and permeability, and possible aesthetic problems (Fry Canyon , http://www.rtdf.org/publisc/permbarr/PRBSUMMS/2Frycnyn.htm).

There is a lack of reliable field data and long term testing nevertheless, permeable reactive barriers are quickly proving to be a preferred choice in remediating contaminated groundwater. A permeable reactive barrier (PRB) is a zone of reactive material placed underground to intercept and react with a contaminant plume in ground water. Typically, PRBs are emplaced by replacing soils with reactive material in a trench cut through a contaminated ground water aquifer. PRBs can also be installed above ground to provide access to the treatment media. Above ground systems are also referred to as ground water treatment cells (Wilkin & Acree, 2009: 1). Permeable reactive barriers (PRBs) are receiving a great deal of attention as an innovative, cost-effective technology for in situ clean up of groundwater contamination. A wide variety of materials are being proposed for use in PRBs, including zero-valent metals (e.g., iron metal), humic materials, oxides, surfactant-modified zeolites (SMZs), and oxygen- and nitrate-releasing ...