Design of permeable reactive barriers and examples of full scale treatments

Permeable reactive barriers (PRBs) are innovative technologies for the in situ remediation of contaminated groundwater. The technology involves the emplacement, into an excavated zone of the aquifer across the flow path of the contaminated groundwater, of a "reactive" filling material permeable to groundwater to intercept and treat the contaminants as the plume flows through under the influence of the natural hydraulic gradient. A wide range of materials are currently available. Some of them remove contaminants through non-destructive mechanisms, such as precipitation, sorption or cation exchange (also promoted by geochemistry modifications in the treatment zone), other through destructive mechanisms, such as abiotic degradation or biological degradation (in biobarriers). The choice among these is primarily based on the contaminant to remove and the abatement required, but the hydrogeological and the biogeochemical conditions of the aquifer may have great influence as well. Sometimes, concurrently mechanisms acts in removing the pollutants. Multilayer barrier systems can be developed in order to treat groundwater affected by different kinds of pollutants.