In Situ Permeable Reactive Barriers for Groundwater Contamination

In situ permeable reactive barriers (PRBs) consist of zones of reactive material, such as granular iron or other typically reduced metal, lime, electron donor-releasing compounds, or electron acceptor-releasing compounds, installed in the path of a plume of contaminated groundwater. As the groundwater flows through this zone, contaminants are degraded to innocuous components through chemical and/or biological reactions, adsorbed, or chemically altered so that they form insoluble precipitates. This article represents a summary review of representative literature on permeable reactive barrier technology. It consists of a description of the technology, a list of treatable contaminants, the processes necessary for its implementation, considerations for conducting performance monitoring, a discussion of the positive and negative attributes and costs of the technology, and lessons learned during recent applications. Where conditions are favorable and time factors are appropriate, this technology appears promising. The main characteristic in its favor is the lack of the need to operate pumps or treatment vessels, thereby saving operation and maintenance costs and allowing the economic value of property to be restored during remediation. Its reliance on natural advec-tive processes to move contaminants through the treatment zone, resulting in long treatment time frames, can be a disadvantage under some circumstances. There are also uncertainties about the long-term effectiveness of the reactive media. Regulators need to continue the trend toward being more receptive of this technology, as well as other innovative technologies, so that it can be improved. This receptiveness will benefit all stakeholders involved.