Environmental Engineering Reference
In-Depth Information
Water
treatment
system
Atmospheric
discharge
Appropriate
vapor treatment
Oil-water-gas separator
Oil storage unit
Water discharge
Blower
UST
Legend
Vapor phase
Extraction tube
Adsorbed phase
Air flow
Air flow
Dissolved phase
Free product
Free-phase
petroleum product
Extraction well
FIGURE 11.20
Example of a multiphase extraction well. (From United States Environmental Protection Agency (USEPA),
Cost
and Performance Report for LNAPL Recovery
, EPA 542-R-05-016, Office of Solid Waste and Emergency Response,
Washington, DC, 2005b.)
selecting more than one technology may be required to achieve the remedial objectives.
With specific contaminants, certain technologies provide more efficient remediation. For
most urban areas of the United States, Figure 11.21 shows the spectrum of geological con-
ditions and contaminant types where certain remedial technologies are effective (Rogers
et al. 2009). For instance, air sparging may be an appropriate technology for remediating
LNAPL VOCs in groundwater if the soil is permeable enough (e.g., sands and gravels);
however, even the presence of small lenses of fine sand or silt can severely limit the effec-
tiveness of this technique (Peterson et al. 2001; Peterson and Murray 2003). Additionally,
air sparging is not an appropriate technology for remediating chromium VI because chro-
mium and most other metals do not evaporate.
Multiple
contaminants
or
free product
Chromium
DNAPL
LNAPL
PNAs
Source control and
monitored natural attenuation (MNA)
In situ:
air sparging
PRB
chemical or
biologic treatment
Source control
MNA
Ex situ:
pump and treat
dual-phase
extraction
Note: Source control refers to hot spot vadose zone soil excavation.
Dashed line represents gradational boundary that is dependent upon cleanup criteria, cumulative
risk factors and specific local or regional factors.
FIGURE 11.21
Remedial matrix of geology, contaminant type, and remedial technology.
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