Handbook of Solvents - George Wypych - ChemTech - Ventech!

23.2 Remediation technologies 1623
Figure 23.2.5. Phytoremediation: transport modes for HC and CHC in plant systems. Transformation of HC and
CHC can be found in the root system with root-associated microbes and tissues of many plant species. HC and
CHC are transported by normal plant physiological processes, such as water uptake and evaporation and transpiration.
[Schematic courtesy M.A. Bucaro.]
23.2.3 IN SITU TREATMENT TECHNOLOGIES
23.2.3.1 Product recovery via GCW technology
Vertical groundwater circulation wells (GCW) create three-dimensional, in situ groundwater
circulation cells to mobilize and transport dissolved phase constituents of interest from
the aquifer to a central well for treatment via a number of biotic and/or abiotic processes.
GCW technology relies on a positive- or negative-pressure stripping reactor in a specially
adapted groundwater well. Often pressure is attained by an above-ground mounted blower
and off-air treatment system, such as activated carbon. A generic GCW is shown in Figure
23.2.6. The basic principle of operation of one GCW technology depends on moving water
within the well to a well screen area above the water table, where water cascades into the
vadose zone surrounding the well. Water is drawn in at a screened area in the aquifer usually
found below the contaminated zone creating vertical water circulation. Volatile organics are
stripped from the dissolved phase by air-stripping and biodegradation is enhanced. For