Environmental Engineering Reference
In-Depth Information
4.3 Thrust area project results
A brief summary describing a major project from each thrust area is given
below.
4.3.1 Chlorinated solvents
The chlorinated solvents project, Solvent Extraction Residual Biotreatment
(SERB), concentrated on the remediation of tetrachloroethylene. SERB tech-
nology was validated in a field-scale study at Sage's Dry Cleaner site, Jack-
sonville, FL (Mravik et al., 1999; Sewell et al., 2000). PCE concentration was
reduced by 70% in the aquifer using this technology. Significant levels (4
mg/l) of the dechlorination product, cis-1,2-dichloroethene (cis-DCE), were
detected in groundwater samples in the area exposed to residual ethanol
after 4 months and increased to 16 mg/l after 10 months. Maximum and
minimum observed rates of dechlorination (based on cis-DCE production)
were 43.6 and 4.2 μg/l/day, respectively. These results indicated that over
time, biotransformation had been enhanced.
Microbial ecology studies using site materials indicated that the site
remained biologically active. Microcosm studies indicated that anaerobic
microbial populations generated a reducing equivalent balance by oxidation
of the cosolvent (ethanol) that was linked to the reductive dechlorination of
PCE. Molecular methods indicated the presence of known groups of dechlo-
rinators. Overall, the project was successful. SERB research is still ongoing
at the Jacksonville site and represents an attractive alternative for chlorinated
solvents' remediation.
4.3.2 PAHs
Results from the PAH pilot-scale study implementing bioaugmentation tech-
nology indicated that bioaugmentation did enhance PAH degradation
(Hansen et al., 2000). Degradation of HMW PAHs into four-ring compounds
(including BaP toxic equivalent compounds) was achieved. Low-molecu-
lar-weight PAHs were extensively degraded in the first 2 to 3 months, and
degradation of the HMW PAHs commenced in the fourth month in micro-
cosms bioaugmented and treated with dried-blood fertilizer. A reduction of
total PAHs (86 to 87%) was realized after 16 months in the pans that had
been bulked, amended with dried-blood fertilizer, and bioaugmented. Com-
parison of the two methods indicated that the time required to achieve 50%
degradation of PAHs was decreased by half through bioaugmented land
farming over traditional land farming methods. The soil used for this
research was heavily contaminated with PAHs (7200 ppm) and would tra-
ditionally not be considered a candidate for bioremediation. This research
indicates that land farming that incorporates bioaugmentation
technology may be an alternative to incineration for remediation of heavily
PAH-contaminated sites. Bioaugmentation would be more cost effective than
