Lexikon

elemental iron or zero-valent iron has performed so successfully in PRB technology that it is now being applied directly for source zone treatment. Though this measure is not considered a PRB, examples of the technology will be included in the PRB pages because the reactive media and treatment mechanism are related. Pneumatic fracturing and injection, hydraulic fracturing, and injection via direct push rigs have been used successfully to introduce the reactive media to the ground-water or soil source area.

Source: US-EPA, Clu-In: http://www.clu-in.org/techfocus/default.focus/sec/Permeable_Reactive_Barriers%2C_Permeable_Treatment_Zones%2C_and_Application_of_Zero-Valent_Iron/cat/Overview/

permeable reactive barriers (PRBs) are applied for passive in situ groundwater remediation. PRBs enable physical, chemical or biological in situ treatment of contaminated groundwater by means of reactive materials, which are filled into the permeable barrier, which the groundwater flows through. The reactive materials are placed in underground trenches or reactors downstream of the contamination plume, forcing it to flow through them. The two main types of PRBs are continuous reactive barriers enabling a flow through its full cross-section, and "funnel-and-gate" systems in which only special "gates" are permeable for the contaminated groundwater. Generally, this cost-effective clean-up technology impairs the environment much less than other methods, being a so called passive technology, without using energy (no pumping, no injection, no heating, minimal care on technolgy maintenance.

see permeable reactive barriers

a permeable reactive barrier (PRB) is defined as an in situ method for remediating contaminated ground water that combines a passive chemical or biological treatment zone with subsurface fluid flow management. Treatment media may include zero-valent iron, chelators, sorbents, and microbes to address a wide variety of ground-water contaminants, such as chlorinated solvents, other organics, metals, inorganics, and radionuclides. The contaminants are concentrated and either degraded or retained in the barrier material, which may need to be replaced periodically. There are approximately 100 PRBs operating in the United States and at least 25 internationally.

PRBs can be installed as permanent or semi-permanent units. The most commonly used PRB configuration is that of a continuous trench in which the treatment material is backfilled. The trench is perpendicular to and intersects the ground-water plume. Another frequently used configuration is the funnel and gate, in which low-permeability walls (the funnel) direct the ground-water plume toward a permeable treatment zone (the gate). Some gates are in situ reactors that are readily accessible to facilitate the removal and replacement of reactive media. These PRBs use collection trenches, funnels, or complete containment to capture the plume and pass the ground water, by gravity or hydraulic head, through a vessel containing either a single treatment medium or sequential media. In circumstances where in situ treatment is found to be impracticable, reactive vessels have been located above ground.

Zero-valent iron has performed so successfully in PRB technology that it is now being applied directly for source zone treatment. Though this measure is not considered a PRB, examples of the technology will be included in the PRB pages because the reactive media and treatment mechanism are related. Pneumatic fracturing and injection, hydraulic fracturing, and injection via direct push rigs have been used successfully to introduce the reactive media to the ground-water or soil source area.

Source: US-EPA, Clu-In: http://www.clu-in.org/techfocus/default.focus/sec/Permeable_Reactive_Barriers%2C_Permeable_Treatment_Zones%2C_and_Application_of_Zero-Valent_Iron/cat/Overview/