Environmental Engineering Reference
In-Depth Information
The main objectives of this pilot-scale tests were to:
•
Validate the usefulness of the two-phase bioremediation scheme that
combines enhanced anaerobic dechlorination of Aroclor and geneti-
cally engineered aerobic PCB-growing microorganisms (GEMs) for
bioremediating PCB-contaminated soils
•
Evaluate the effects of different solids loading rates (or moisture
contents) on the bioremediation of PCBs and application of GEMs
•
Develop critical design information on the application of GEMs for
full-scale bioremediation of PCB-contaminated soils
A pilot-scale demonstration study consisting of side-by-side compari-
sons of three bioremediation processes was performed at the Environmental
Laboratory, U.S. Army ERDC, Vicksburg, MS. Three parallel bioremediation
processes with different solids loading rates were used to evaluate the effects
of solids loading on soil mixing, aeration, addition, and uniform distribution
of nutrient amendments/GEMs, and final disposal/use of treated material.
Each bioremediation process has three separate reactors (treatments) to eval-
uate the effects of ferrous sulfate and surfactants on PCB dechlorination
(Table 6.6).
6.5.2 Site description
PCB-contaminated soil was collected from the GE site in Rome, GA. The
PCB concentration in this soil ranges from 500 to 1000 ppm (Table 6.5). The
soil is clayey with little sand (87.4% fines, 11.6% sand, and 1% gravel). The
soil has a liquid limit (LL) of 57 and plastic limit (PL) of 23. Chemical
characteristics of the Rome, GA, soil are summarized in Table 6.7. Soil was
collected from 6 ft below the ground surface. After excavating, the soil was
cleaned of any pebbles/debris that was more than 1 in. in size. The collected
soil was sieved through 1 in. mesh screen, thoroughly mixed, and homoge-
nized at the site. About 2240 kg of homogenized soil was shipped to ERDC
in 10 55-gallon drums. The soil was used to load the triplicate treatment
reactors for each bioremediation process and for the initial physical and
chemical characterizations of the collected soil.
Table 6.6
Experimental Design
No. of
Treatments
Reactor
Treatments
Low solids
3
Surfactant + iron +
ethanol
Iron + ethanol
No amendments
Medium solids
3
Surfactant + iron +
ethanol
Iron + ethanol
No amendments
High solids
3
Surfactant + iron +
ethanol
Iron + ethanol
No amendments
