Environmental Engineering Reference
In-Depth Information
When setup costs and operation and maintenance (O&M) costs are cal-
culated, overall remediation expenditures could be significantly reduced if
a PAH land-farming site were treated quarterly instead of weekly (Rast,
2001). As an example, based on 1999 remedial action cost engineering and
requirements (RACER) cost estimates for the northeast United States, tradi-
tional land farming of this soil would require a minimum of $3.5 million for
a single year of treatment. One alternative, 6 months of intensive treatment
followed by 6 months of minimal treatment, would require approximately
$1.6 million. A second alternative, 12 months of minimal treatment, would
require less than a $0.5 million, primarily due to decreased expenditures for
tilling and watering. Therefore, choices in land-farming options could pro-
vide significant savings at sites where time is not a factor. In addition to
decreasing costs, by limiting the intervention at a site, the potential for
human exposure to the contaminant is decreased, the production of fugitive
dust (air particulates) is decreased, and the possibility of accidental ground-
water contamination is decreased.
The significance of these positive results is further enhanced in light of
the excessive PCP co-contamination, commonly found in PAH-contaminated
sites but rarely studied in conjunction with PAH degradation in the labora-
tory. Biological degradation of seemingly high concentrations of PAHs has
not been successfully demonstrated in previous efforts. As this study
showed, microbiological analysis coupled with contaminant degradation
analysis demonstrated biological degradation of the recalcitrant compounds.
Biological degradation of PAHs with previously reported inhibitory PCP
concentrations is possible and is appropriate for sites where time is available
for long-term active bioremediation.
7.6 Recommendations for transitional research
7.6.1 PAH availability in soil and regulatory cleanup levels
The natural recovery process could be enhanced through the use of GEMs,
as indicated in the accompanying SERDP report on PCB bioremediation. In
this report, the use of GEMs was successful in the biodegradation of chlori-
nated organics in the laboratory. Bioaugmentation in this study was accom-
plished with the use of vermiculite as a biocarrier, a technology developed
by the PAH thrust area. GEMs would be a logical next step in investigating
PAH biodegradation.
7.6.2 Phytoremediation of PAHs
Phytoremediation is defined as the use of green plants to remove, contain,
or decrease the toxicity from environmental contaminants. As a final polish-
ing step to land farming, phytoremediation should be further studied. It is
a cost-effective technology with many advantages over highly engineered
solutions, including public acceptance. Only in the last decade has research
