Sustainable Water Management - Sustainable Practices in Geoenvironmental Engineering - page 98

and properties, must be determined. Laboratory tests and treatability studies are essential
elements of the design procedure for the treatment walls (PRBs). When designed properly,
a PRB provides the capability for assimilation of the contaminants in the contaminant
plume as it migrates through the barrier. In that sense, PRBs function in much the same
manner as IRR—except that the region is a constructed barrier. Some of the assimilative
processes in the PRB include the following:

• Inorganic contaminants: sorption, precipitation, substitution, transformation, com-
plexation, oxidation, and reduction
• Organic contaminants: sorption, abiotic transformation, biotransformation, abi-
otic degradation, biodegradation

Use of natural attenuation for management of contaminant transport and transmission
in soil: We have at least three ways in which natural attenuation can be used to man-
age and/or control the transport of contaminants in soil. These include MNA, ENA, and
EngNA. These have various beneits and are used as effective tools in the control and
management of contaminant and contaminant leachate plumes, and especially in speciic
bioremediation schemes. More detailed discussions of these can be found in Chapter 10.
Other techniques such as air sparging are employed to volatilize the VOCs from the
groundwater. Biological techniques can also be combined with the extraction techniques
in biosparging (Figure 3.14) and bioslurping processes. Essentially, both techniques add
another component to the bioventing technique, for example, shown as the solvent extrac-
tion procedure in Figure 3.10. In the bioslurping technique, another dimension to the SVE
process is added using vacuum-enhanced pumping to recover free product (NAPLs).

Activated carbon cells or biofilters

Vacuum pump

Air-water separator

Contaminated vapor

Vapor
extraction
well

Compressed air

Vapor
phase

Groundwater level

Entry ports for
compressed air

Air flow from compressor

Dissolved phase

FIGURE 3.14
Schematic of a biosparging process in combination with SVE. Note that a series of compressed air wells and SVE
wells can be introduced into the ground, connected in series or in parallel. Obviously, the number of wells that
can be introduced will depend on the capacity of the compressor and vacuum pump systems.