vvEPA
United States
Environmental Protection
Agency
EPA/540/F-95/509
August 1995
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology Bulletin
Process for the Treatment of Volatile Organic Carbon and
Heavy-Metal-Contaminated Soil
International Technology Corporation
Technological Description: The batch steam distillation and
metal extraction treatment process is a two-stage system that
treats soils contaminated with organics and inorganics. This sys-
tem uses conventional, readily available process equipment, and
does not produce hazardous combustion products. Hazardous
materials are separated from soils as concentrates, which can
then be disposed of or recycled. The treated soil can be returned
to the site.
During treatment, waste soil is slurried in water and heated to
100 degrees Celsius. This heat vaporizes volatile organic com-
pounds (VOC) and produces an amount of steam equal to 5 to
10 percent of the slurry volume. Resulting vapors are condensed
and decanted to separate organic contaminants from the aque-
ous phase. Condensed water from this step can be recycled
through the system after further treatment to remove soluble
Recycle water from
extraction step
organics. The soil is then transferred as a slurry to the metals
extraction step.
In the metals extraction step, the soil slurry is washed with
hydrochloric acid. Subsequent countercurrent batch washing with
water removes residual acid from the soil. The solids are then
separated from the final1 wash solution by gravimetric sedimen-
tation. Most heavy metals are converted to chloride salts in this
step. The acid extract stream is then routed to a batch distillation
system, where excess hydrochloric acid is recovered (see figure
below). Bottoms from the still, which contain heavy metals, are
precipitated as hydroxide salts and drawn off as a sludge for
offsite disposal or recovery.
As a batch process, this treatment technology is targeted at sites
with less than 5,000 tons of soil requiring treatment. Processing
Offsite disposal
Soil slurry to
metal extraction
or dewatering vessel
Batch distillation vessel
Figure 1. Batch steam distillation step.
Printed on Recycled Paper
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time depends on equipment size and batch cycle times; roughly
one batch of soil can be treated every four hours. Estimated
treatment costs per ton, including capital recovery, for the two
treatment steps are as follows:
Batch Steam Distillation
500-ton site
2,500-ton site
Metals Extraction
(including add recovery)
500-ton site
2,500-ton site
$299-393/ton
$266-350/ton
$447-619/ton
$396-545/ton
Waste Applicability: This process may be applied to soils and
sludges contaminated with organics, inorganics, and heavy met-
als,
Results: The batch steam distillation and metal extraction pro-
cess was accepted into the SITE-Emerging Technology-Program
In January 1988. Under the program, three pilot-scale tests have
been completed on three soils, for a total of nine tests. The
removal rates for benzene, toluene, ethylbenzene, and xylene
were greater than 99 percent. The removal rates for chlorinated
solvents ranged from 97 percent to 99 percent.
One acid extraction and two water washes resulted in a 95
percent removal rate for heavy metals. Toxicity characteristic
leaching procedure tests on the treated soils showed that soils
from eight of the nine tests met leachate criteria. Data were also
collected on the recovery rate for excess acid and the removal
rate for precipitation of heavy metals into a concentrate.
For Further Information:
EPA Project Manager:
Ronald Lewis
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7856
Rax: 513-569-7620 = - -
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/S40/F-95/S09
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