Various configurations of in-situ permeable reactive barriers (PRBs) systems have been constructed.

In a continuous permeable wall configuration the treatment material is distributed across the width of the contaminated groundwater plume.  Granular iron has a hydraulic conductivity greater than many aquifers and thus does not significantly alter the natural groundwater flow path.   Continuous PRBs do not necessarily need to be keyed into a low permeability zone as the PRB will not divert the groundwater downwards.   The continuous PRB has been the most common configuration used to date.

A funnel and gate configuration uses low permeability materials (funnel) to direct groundwater towards a permeable treatment zone (gate).  By directing or funneling the groundwater towards a treatment gate the natural groundwater flow velocity may be increased several times.  Funnel and gate designs need to extend beyond the extent of the plume to ensure that all of the contaminated groundwater is captured and treated.  The length of a funnel and gate system may be on the order of 1.2 to 2.5 times the plume width depending on the number of gates and the funnel to gate ratio.  To ensure that flow beneath the system does not occur, funnel and gate systems must be keyed into an underlying low permeable zone.

Closely related to the funnel and gate design are in-situ reactive vessels which use funnels, collection trenches, or complete containment to capture the plume and pass the groundwater, by gravity or hydraulic head, through a buried vessel containing granular iron for VOC removal or a series of treatment materials for the remediation of mixed plumes.

ETI is excited to be a licensee of the GeoSiphon ^TM technology developed and patented by Westinghouse Savannah River Company. The GeoSiphon^TM provides an alternative to a continuous wall or funnel and gate configurations. The GeoSiphon^TM induces the passive flow of contaminated groundwater through an in-situ treatment cell containing granular iron (or other materials) by use of a siphon from the cell to a discharge point. Once the siphon is established, passive flow is maintained by the natural hydraulic head difference between the GeoSiphon^TM and a downgradient stream or recharge well. This configuration was first installed as a pilot demonstration at a DOE site in Aiken, South Carolina in July 1997 and ETI has identified several potential applications for this configuration.

Successful above-ground applications using granular iron have been implemented in remedial applications where in-situ applications are not feasible. These systems can also replace existing air strippers or granular activated carbon canisters. With granular iron reactors, the contaminants are degraded to non-toxic end products and not simply transferred to another medium such as granular activated carbon which would require further treatment and handling. Several above-ground applications have been installed.