540MR95535
United States
Environmental Protection
Agency
EPA/540/MR-95/535
March 1997
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
COGNIS TERRAMET® Lead Extraction Process
Twin Cities Army Ammunition Plant
COGNIS, Inc
Technology Description: The COGNIS, Inc., TERRAMET* lead
extraction process uses chemical leaching to remove metals bound
to sands and fines in contaminated soil. COGNIS constructed a full-
scale TERRAMET* lead extraction unit and was awarded a contract
to remediate Site F at the Twin Cities Army Ammunition Plant
(TCAAP). Before processing, particulate metal is removed by size
and density separation, and sands and fines are separated from
each other. TERRAMET* processing of sands and fines is performed
separately. After leaching, dissolved and suspended lead present
in the liquid phase is recovered, and the leaching solution (leachant)
is recycled. Treated soil is transferred to the treated soil pile and is
tested to determine the level of contaminants.
The first full-scale application of the TERRAMET* process was
implemented at the TCAAP site. Brice Environmental Services
Corporation (BESCORP) conducted the pre-leach processing.
Combined processing begins when contaminated soil is introduced
into a feed hopper (see Figure 1). Up to 15 tons of soil per hour is
continuously fed from the feed hopper onto a conveyor belt, where
it is weighed by load cells and elevated into a revolving trommel.
In the trommel, the contaminated soil is sprayed with water, and
particles less than 0.25 in. in diameter, including sands, fines,
and some particulate lead, pass through holes near the trommel
exit. The resulting slurry flows to the wet classifier, where the fines
and sand streams separate. The sand is treated in a density
separation process (that is, with two jigs) to remove lead and other
dense material. The overflow solids from the density separation
process are combined and advanced with a sand screw to the
sand leaching unit. Fines are carried to a clarifier, where the
mixture is flocculated and allowed to settle. Clarifier underflow is
pumped to the fines leaching process. The washed, oversized
fraction resulting from the trommel bypass of the leaching process,
are subjected to inspection and removal of any remaining
ordnance items, and are combined with treated soil.
In the COGNIS TERRAMET* sand leaching process, sands are
advanced countercurrent to the leachant in a coarse material
washer. Leached sand is removed from the coarse material
r | (Four Mixer -
Leachant: Clarifiers)
Regenerated
Leachant ,.. _H
Figure 1. TERRAMET" lead extraction process
Printed on Recycled Paper
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washer by a sand screw; this sand is then neutralized by adding
lime. The neutralized sand is added to the washed, oversized
material on the conveyor belt and is conveyed to the treated soil
pile. Leachant containing lead extracted from the sand is advanced
to two cells of the lead recovery system.
In the TERRAMET* fines leaching process, the solids are mixed
with the leachant in four mixer-clarifiers. In the first clarifier, fines
are advanced with the leachant flow; in the remaining three
clarifiers, fines are advanced against the leachant flow. Underflow
from the fourth clarifier is composed of treated fines that are then
neutralized and dewatered in a continuously operating centrifuge.
Centrifuged solids are delivered to the treated soil pile.
Lead-bearing leachant from the fines is passed through a total of
four lead recovery cells on which elemental lead is deposited,
which regenerates the leachant for reuse. Lead is periodically
washed from the cells; the lead is then dewatered and drummed
as lead concentrate for transport to a lead smelting facility.
Waste Applicability: The TERRAMET* process is designed to
treat soils contaminated with lead. However, the process design
can be modified to treat soils contaminated with other metals.
Treatability studies on representative material are necessary to
determine the composition of the leachant and the amount of
residence time required in the clarifiers.
Demonstration Results: The SITE demonstration tookplace at
the TCAAP site from August 2 to 5,1994, during full-scale cleanup
activities. About 400 tons of soil were processed during the
demonstration. A primary goal of the TERRAMET* demonstration
was to determine process removal efficiencies for lead; however,
removal efficiencies for other metals were evaluated as well.
Samples of the following were collected: the feed soil, treated and
untreated oversized soil, several lead concentrate streams, several
sand and fine streams before and after leaching, and liquid
streams. The samples are currently being analyzed for lead and
other metals and for several soil characteristics such as particle
size distribution, load bearing capacity, cation exchange capacity,
alkalinity, and moisture content. Samples were also collected so
that bioassays could be conducted to determine if the treated soil
is toxic to earthworms and whether the treated soils can support
plant growth.
Based on preliminary analytical results from the demonstration,
lead levels in the feed soil ranged from 380 to 1,800 milligrams per
kilograms (mg/kg). Lead levels in untreated and treated fines
ranged from 210 to 780 mg/kg and from 50 to 190 mg/kg,
respectively. Removal efficiencies for lead in the fines fractions
ranged from 65% to 77%. Data for treated sands and oversized
soils are not yet available. The COGNIS TERRAMET® and
BESCORP processes operated smoothly at a feed rate of 10 to 20
tons per hour with no major problems. Size and density separation
using the BESCORP process reduced the lead load to the
TERRAMET* leaching process by 39% to 63%. Leaching solution
was recycled, and lead concentrates were delivered to a lead
smelting facility. The cost of treating contaminated soil at the
TCAAP site using the COGNIS and BESCORP processes is about
$210 per ton of treated soil ($219 including ordnance removal),
based on treatment of 10,000 tons of soil. This estimate includes
costs for mobilization/demobilization, site preparation, permitting,
treatment, residual waste handling, chemical analyses, and labor.
An innovative technology evaluation report describing the
demonstration and its results will be available in the fall of 1997.
For Further Information:
EPA Project Manager:
Mike Royer
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Building #10 (MS-104)
2890 Woodbridge Avenue
Edison, N.J. 08837-3679
Telephone: (908) 321-6633; Fax: (908) 321-6640
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
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POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
EPA/540/MR-95/535
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