Modeling Efficienza GCW |
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Ground Water Circulation Wells (GCWs) can be used in conjunction with other in situ remediation technologies to treat halogenated VOCs, semi-VOCs (SVOCs), pesticides, and petroleum products and their constituents such as benzene, toluene, ethyl benzene, and xylene (BTEX). They have been applied to a wide range of soil types, from fine silty clay to coarse sandy gravel. With at least two screen sections, GCWs are universally applicable remediation tools. They can be employed in several configurations, such as in well stripping (IWS), bioaugmentation, enhanced natural attenuation adding nutrients and/or electron acceptors for stimulating bioremediation processes, bioventing, soil vapour extraction, reactive nanoparticle dehalogenation, in situ denitrification and chemical oxidation (ISCO) or reduction (ISCR). They may also be combined with a LNAPL/DNAPL recovery system in the aquifer. Different well configuration and/or composition allows wide and versatile solutions, e.g. the vPRB (in situ Virtual Permeable Reactive Barrier) where several vertical circulation wells are arranged in one line perpendicular to the natural groundwater flow to obtain a curtain of overlapped circulation cells; such configuration could be promising to treat huge plumes generated by contaminated mega-sites. Groundwater Circulation Well systems are designed to create in situ vertical groundwater circulation cells by drawing groundwater from an aquifer through one screen section of a double-screened well, and discharging it through the second screen section. The pressure gradient between two hydraulically separated screen sections in the well induces a circulation flow in the aquifer. The groundwater moves through the treatment zone both horizontally and vertically before entering the influent screen.
In both the standard and reverse flow modes of operation, groundwater is circulated around the central GCW, but none is removed from the aquifer without any draw down. Induced differences in potentiometric head establish and maintain the 3-dimensional circulation cell in an ellipsoidal area around the circulation well. The majority of the groundwater captured by the circulation cell circulates a number of times through the GCW before being released down-gradient. As such, water serves as the in situ carrier bringing components of interest from throughout the capture zone to the GCW system where it is treated and then discharged back into the formation. The vertical and horizontal circulation flow patterns force water to move through the entire aquifer portion within the circulation cell by forcing flow through less permeable formation lenses. Remediation time is faster because the vertical flow forces the groundwater to flow perpenticular to low permeable zones, thereby enhancing the mobilization of contaminants These flow dynamics and dimensions of the capture zone, circulation cell, and release zone can be calculated for a specific site and used as design aids based on numerical simulations of the groundwater hydraulics . However, site-specific calibration of the modelled value should be conducted during a pilot test prior to the final design and engineering of a remedial system composed of multiple, overlapping GCW systems.
The treatment component of the GCW combines a series of biotic and abiotic processes to affect removal or destruction of site specific COI (Components of Interest):
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