Permeable Reactive Barriers employ the established geotechnical engineering concepts of slurry wall technology to provide a means of containing and treating contaminated ground water plumes. It is a technology that has been developed relatively recently and which facilitates the remediation of contaminated groundwater and soil without mass excavation, disposal or conventional "pump and treat" methods. Usually, a reactive barrier is installed as a narrow trench beneath the ground surface so that contaminated groundwater passes through the barrier, and emerges 'clean' because contaminates are treated and/or removed by the reactive medium of the barrier.
Bellevue PRB, Perth, Western Australia
Typical treatment media used as a permeable reactive barrier wall include granular iron, activated carbon, engineered bacteria, chemicals, and special clays. Since any permeable reactive barrier extends to depth and in particular, below the groundwater table, the principals of slurry wall technology are useful in minimizing excavation volumes, eliminating dewatering, and reducing costs. Special construction considerations are needed for installing reactive barriers to satisfy the design life criteria of the reactive medium and its cost-effectiveness.
Often, "impermeable" slurry walls are used to direct the groundwater flow to a "gate" of permeable material containing the reactive medium; this type of installation is called a "funnel and gate".
Bellevue PRB, Perth, Western Australia
In most cases, the least expensive method for installing funnel and gate is a slurry trench method. An "impermeable" slurry wall is installed either side of the "gate" to direct groundwater toward the reactive barrier "gate".
A Bio-Polymer slurry trench drain can provide the "gate" of the permeable reactive barrier wall containing the reactive medium. The savings from this combination of methods are considerable and include savings in excavation volumes, disposals costs, mobilization, and construction time.
Bellevue PRB, Perth, Western Australia
Slurry trenching methods have been proven to facilitate the installation of reactive iron (ZVI), engineered bacteria, compost, carbon and other materials without significantly affecting the reactive potential of the reactive barrier walls.
In some cases, i.e. bio-treatment schemes, the Bio-Polymer slurry can actually promote the reactivity of the media. The installation of the reactive iron and other media using the bio-polymer slurry method requires, specialist equipment, materials and methods.
