GCW as a means of efficiently remediating contaminated groundwater

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Courtesy of IEG Technologie GmbH

With the conventional 'Pump & Treat' method, groundwater is normally extracted from one or several wells, cleaned above ground and disposed off to the either groundwater or surface water. Even when extraction and injection wells are combined, predominantly higher perme-able areas are preferentially penetrated and more fine-grained structures are circumflowed. The bulk of contaminants are absorbed to the less permeable materials like fine- grained sands, silty or clayey layers. By diffusion, the contaminants are released out of these reser-voirs very slowly. After a short period of time they effect a stagnation of the contamination discharge ('Tailing Effect').

Depending on subsoil conditions (geology and hydrogeology) and contaminant type and concentration, remediation of sites can take several decades. Consequently, 'Pump&Treat' technique is considered as being suitable and effective only for containment to prevent further spreading of contaminants, but is no longer considered as a remediation method.

With the 'Pump & Treat' method groundwater is radially extracted out of the aquifer. Due to a change in the hydraulic gradient, both contaminated and clean groundwaterflows through the contaminated subsoil and is constantly treated above ground with considerable technical effort. GCW systems are designed to create in-situ vertical groundwater circulation cells by drawing groundwater from an aquifer through one screened section of a multi-screened well and dis-charging it through another screened section. If a circulation flow is generated in the aquifer, the treated groundwater is circulated several times in the aquifer before it flows downstream. This guarantees a considerably more efficient course of remediation compared with the 'Pump&Treat' method.

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