vvEPA
United States
Environmental Protection
Agency
EPA/540/MR-95/524
August 1995
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
New York State Multi-Vendor Bioremediation
ENSR Consulting and Engineering/Larsen Engineers
Ex-Situ Biovault
Technology Description: The ENSR Biovault Treatment Pro-
cess is an ex-situ bioremediation technology for the treatment of
organic contaminated soils. Contaminated soils placed in spe-
cially designed soil piles, referred to as biovaults, are remediated
by stimulating the indigenous soil microbes to proliferate and
metabolize the organic contaminants in the soil at an accelerated
rate. Depending on contaminant phase and volatility, a certain
portion of the contaminant mass is removed from the soil by
vapor extraction/air stripping. Optimizing the bioremediation com-
ponent of the ex-situ biovault technology involves a series of
controlling factors that directly influence microbial activity, includ-
ing soil pH, electron acceptor availability, moisture, and nutrients
such as nitrogen and phosphorus. According to the developer,
the principal products of the technology are water, carbon dioxide
and inorganic salts. Some intermediates may also be formed as
a consequence of metabolic activity, depending on the chemistry
of the parent contaminants and mode of operation (e.g., aerobic
or anaerobic). The developer claims that any intermediates that
are formed will be captured and degraded by other microbes,
sorbed on soil particles for later degradation, solubilized by water
in the soil, or volatilized and removed by the biovault's gas
management system (QMS).
The biovault is constructed of 30 mil HOPE liners placed over soil
berms which support and contain the soil pile (Figure 1). The
bottom of the vault consists of double lined HOPE with a leak
detection system between the two liners. The vault floor slopes
to one corner to a sump, which contains a pump to recover
leachate. Leachate collected in the sump is pumped to storage
and eventually recycled to the soil pile via a soaker hose system
as part of the technology's moisture control system. The soaker
hose system is also used for pH adjustment and nutrient delivery.
The vault uses a gas management system (QMS) to ventilate the
soil and thereby control the availability of the electron acceptor
(oxygen). Contaminated soil is sandwiched between a lower and
upper air distribution system. The QMS is designed and oper-
ated to provide uniform air flow through the soil. Vault off-gases
are treated by activated carbon before being released to the
atmosphere.
The biovaults can be operated on a strictly aerobic basis, where
the soils are periodically vented with air over the remediation
period, or on an alternating anaerobic/aerobic basis, which in-
volves extended periods when no air is delivered to the soil. The
latter method of air management is believed to be better suited
for biodegradation of highly halogenated contaminants.
Unarc
Figure 1. ENSR Biovault Section
Waste Applicability: According to the developer, the ex-situ
biovault remediation technology is applicable to soils contami-
nated with volatile and semivolatile compounds, including vari-
ous fuels, hydrocarbons, and solvents. The technology is believed
to degrade halogenated compounds when operated in the anaero-
bic mode or as a result of cometabolic reactions while operating
in the aerobic mode.
Demonstration Results: Pilot-scale testing of the Ex-Situ Biovault
bioremediation process was conducted at the Sweden-3 Chapman
Site in Sweden, NY as part of the Multi-Vendor Demonstration of
Bioremediation Technologies over a -5 month period between
July 1994 to December 1994. The presently inactive 2-acre
landfill was used to dispose of construction and demolition debris
between 1970 and 1975. A state sponsored investigation of the
site conducted between 1985 and 1987 revealed buried drums
throughout the landfill, h 1991, over 2,300 drums were removed
from the landfill under an interim remedial measure (IRM). A
remedial investigation conducted after the landfill was capped
identified three areas of heavily contaminated soil. The area
referred to as the "Northwestern source area", the focus of the
technology evaluation and the largest of the three areas, con-
tained soils contaminated with TCE, PCE, acetone, MEK, MIBK,
toluene, and xylenes.
Printed on Recycled Paper
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The demonstration involved the pilot-scale testing of two side-by-
side biovaults, each about 40 ft2. One 100 yd3 of soil from the
"Northwestern source area" was excavated and placed in each
vault. One biovault was operated in a strict aerobic mode while
the other alternated between the aerobic and anaerobic mode.
A primary objective of the demonstration was to determine the
effectiveness of the ex-situ Biovaults in reducing VOC contami-
nation in the soil. Based on this objective, the Developer set as a
remediation objective that 90% of the final samples collected
from each vault after 6 months of continuous operation would be
below NYS Cleanup objectives for six target VOCs (acetone, 2-
butanone [MEK], 4-methyl-2-pentanone [MIBK], trichloroethene
[TCE], tetrachloroethene [PCE] and cis-1,2-dichloroethene [DCE]).
In addition, the developer claimed that biodegradation would be
the dominant mechanism of contaminant removal. Additional
analytes from the soil, vault water, and extracted air streams
were collected to further assess performance and effectiveness
of the ex-situ Biovaults.
The first primary objective was evaluated by measuring the re-
sidual concentrations of the selected VOCs-in-nine subplots of
each vault at the completion of the test period. Soil sampling
was also conducted initially and at -3 months to assess the
overall efficiency of the process in reducing each contaminant.
The second primary objective, determination of biodegradation
contribution, was determined by estimating the difference be-
tween the initial mass of each VOC in each vault and the sum of
the VOC masses removed in the extracted air stream and vault
water and that remaining in the soil at 6 months. Coupled with
other observations and analyses, the difference between the total
contaminant mass reduction and mass reduction by abiotic mecha-
nisms was considered the maximum mass destroyed by biologi-
cal processes.
Preliminary results from the Ex-Situ Biovault technology demon-
stration follow:
• Significant reductions in soil VOCs occurred in both vaults over
the 6-month Demonstration period, although data exhibited
considerable variability.
• Preliminary data suggest that the performance of the vault
operating in the alternating mode may have been adversely
affected by the frequency of air venting, including that con-
ducted during off-gas sampling of this vault.
An Innovative Technology Evaluation Report (ITER) describing
the complete demonstration will be available by late 1995.
For Further Information:
EPA Project Manager
Annette Gatchett
U.S. EPA
National Risk Management Research Laboratory (NRMRL)
- 26-WrMartin-Luther King-dr. Dr.—^- ——-—---"-'---=—
Cincinnati, OH 45268
(513) 569-7697
NYSDEC Project Manager
Nick Kolak
New York State Dept. of
Environmental Conservation
Room 208
50 Wolf Rd.
Albany, NY 12233
(518) 485-8792
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penally for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/540/MR-95/524
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