United States
Environmental Protection
Agency
EPA/540/F-94/501
March 1994
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology Bulletin
Institute of Gas Technology
'
Fluid Extraction-Biological Degradation Process
Technology Description: The fluid extraction-biological
degradation (FEBD) process is a three-step process that
remediates organic contaminants in soil. The system is shown in
figure 1. It combines three distinct technologies: (1) fluid extrac-
tion, which removes the organics from contaminated solids; (2)
separation, which transfers the pollutants from the extract to a
biologically-compatible solvent; and (3) biological treatment, which
degrades the pollutants to innocuous end-products.
In the fluid extraction step, excavated soils are placed in a
pressure vessel and extracted with a recirculated stream of
supercritical or near-supercritical carbon dioxide. An extraction
cosolvent increases removal of many contaminants.
Following extraction, organic contaminants are transferred to a
biologically-compatible separation solvent such as water or a
water/methanol mixture. The separation solvent is sent to the
final stage of the process, where bacteria degrade the waste to
carbon dioxide and water. Clean extraction solvent is recycled to
the extraction stage.
Biodegradation occurs in aboveground aerobic bioreactors, using
mixtures of bacterial cultures capable of degrading the contami-
nants. Selection of cultures is based on site characteristics. For
example, if a site is contaminated mainly with polycyclic aromatic
hydrocarbons (PAH), cultures able to metabolize or co-metabo-
lize 1:hese hydrocarbons are used.
i
Project Description: The supercritical extraction stage of
the FEBD process was evaluated through a series of laboratory
scale tests with three PAH contaminated soils identified as soils
1, 2| and 3. The effectiveness of the extraction process was
determined by following the fate of sixteen compounds.
Soil 1 was collected from a wood treatment site in Texas and
soils 2 & 3 were from former town gas sites. Total contaminant
concentrations were similar for the soils at 1500 to 2000 mg/g,
but contaminant distributions are somewhat different.
Extraction tests were performed in a batch supercritical fluid
extraction (SCE) unit. Soil 1 tests varied temperature, pressure,
Pressure
reducing
valve. ]
Separation
solvent
Figure 1. Fluid extraction-biological degradation process.
Contaminated
sediments
I
Extraction solvent
with contaminants
Stage 1
EXTRACTION
I i
Decontaminated
sediments
' Recycled or
Extraction cleaned
solvent extraction
solvent
~~"" t
Compressor
Make-up
i
\
Stage 2
SEPARATION
i
Separation solve
with contaminan
Stage 3
BIOLOGICAL
DEGRADATION
Water, carbon
. dioxide, and
extraction
solvent
biomass
i '
Printed on Recycled Paper
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COt to contaminant ratio and tha addition of 5% methanol co-
sohttnL Temperatures ware not varied with soils 2 & 3 extraction
taste, "= .. .'.'."."''.'.'..'.'.
6) Microbial consortium effectively metabolized or transformed
reactors, : = = ==: = =
Th@ extraction tevete from the soils decreased from soil 3 to sol 1
to soil 2. Soils 2 and 3 ware alipost entirely sand white soil 1 was
sawetf wtth a 14% clay content Clay in soil 1 did not appear to
ktitgfera win the extraction of|he PAH contaminants.
Biological conversion of the measurable PAHs was obtataed In
both, batch-fed and continuously-fed constantly stirred tank reac-
tors (CSTR&J, The conversion rate and the removal efficiency was
signtfcaot Jn al systems examined. The PAHs were biologically
iitiMfateed or transformed undar short hydraulic retention times,
and all tha PAHs, including th© four to sfx ringed moieties were
suseeptfbla to the Wologfcat action.
Demonstration Results: The results of this study show that
Ih* FEBD process was able to:
t) Effectively extract 2-6 ring PAH contaminants at low
tepsratures and moderate pressures.
2$ Increase axtractfon levels wfth increasing pressure and in-
creasing CO2 to contaminant ratbs»
41fncr®a®@ PAH extraction with a 5% methanol co-solvent
:=7}Grj|Wfh q|,rnis|abpjte actiyfflesi of Jhe rriicrqMal consorjium
s wKe no! IHiiBd By methanol extract.
For Further Information:
EPA PROJECT MANAGER:
Annette Gatehett
US. EPA
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45288
513-589-7897
Fax: 513-569-7120
TECHNOLOGY DEVELOPER CONTACT:
J, Robert Paterek
Institute of Gas Technology
3424 South State Street
Chicago, fL 60618
312-949-3947 /:
Fax: 312-949-3700
SJEfectfvely extract PAHs contaminants from soils with 14%
1 content.
199*—
United States
Environmental Frotecifon= Agency
Center for Environmental Research Informaffon
CioclnnMi, OH 45268
Official Business
P&nafty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPAI54QIF-94SQ1
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