vvEPA
United States
Environmental Protection
Agency
EPA/540/MR-97/507
September 1997
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Molecular Bonding System® for Heavy Metals Stabilization
SolucorpP Industries Ltd.
Technology Description: The patent-pending Solucorp® Mo-
lecular Bonding System (MBS®) utilizes a solid-phase chemical
stabilization process to reduce the teachability of heavy metals in
soils, slags, and other solid wastes. Arsenic (As), cadmium (Cd),
chromium, copper, lead (Pb), mercury, and zinc are rapidly con-
verted to less-soluble metallic sulfides. The technology was ap-
plied ex situ during the demonstration but may be utilized with
standard in situ mixing equipment; this bulletin discusses only ex
situ applications.
Soil is excavated, then pretreated by screening to remove debris
larger than two inches in diameter. As with other ex situ technolo-
gies, wet or clayey soils may need to be dried to improve material
handling characteristics. The MBS agent, a proprietary chemical
mixture, is added to the pugmill where it is blended with the soil
(Figure 1). Moisture also may be added at the pugmill, to increase
the moisture content of the soil to 15 to 25 percent to promote
uniform mixing. Treated soil exits on a conveyor and is stockpiled.
Leachability of target metals in the treated soil is determined using
the Toxicity Characteristic Leaching Procedure (TCLP) or other
appropriate test, such as the Synthetic Precipitation Leaching
Procedure (SPLP). Depending on chemical feed and water re-
quirements, the volume expansion of the treated soil may range
from 3 to 16 percent. The total metal concentrations in and the
physical characteristics 'of the soil are not significantly changed by
treatment. Hydrogen sulfide gas formed during the process is
collected and vented through drums of specially coated carbon; a
packed tower scrubber, which is more efficient, may replace the
carbon if air emission standards are more stringent.
Waste Applicability: The MBS process is designed to reduce
teachable heavy metals concentrations from soils or solid wastes.
Certain metals present in reduced forms (e.g., As) may require
treatment with an oxidizing agent to improve treatment effective-
ness. As with other ex situ processes, this technology is most
cost-effective for treatment of contaminants in shallow soils be-
cause the soils are readily accessible. However, excavation to
greater depths, or use of in situ mixing may provide cost-effective
applications of the MBS technology at certain sites. Soils or
wastes with high chloride content (in excess of 15 to 20 percent)
cannot be effectively treated with this technology.
Demonstration Results: The U.S. EPA National Risk Manage-
ment Research Laboratory (NRMRL) Superfund Innovative Tech-
nology Evaluation (SITE) Program conducted a demonstration of
the Solucorp MBS process at the Midvale Slag Superfund Site in
Midvale, Utah, during the Spring of 1997. Three waste streams,
contaminated with As, Cd, and Pb, were treated: Soil/Fill (SF),
Slag Pile B (SB), and Miscellaneous Smelter Waste Without Brick
(SW). Approximately 500 tons of each waste/soil was treated. A
second test of 500 tons of SW was performed independently by
Solucorp using a higher purity sulfide component in the MBS
formula; after the initial demonstration of SW resulted in TCLP
teachable Cd concentrations exceeding the regulatory limit of 1
mg/L. For the SW retest^ Science Applications International Cor-
poration (SAIC) performed sampling and provided oversight and
analytical support under contract to Solucorp. All procedures were
identical to those used by SAIC during the initial demonstration
that was performed for EPA-NRMRL. EPA-NRMRL provided in-
dependent oversight and review of the SW retest results.
Offgas collection points
Figure 1. MBS® soil remediation process.
Printed on Recycled Paper
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Because EPA-NRMRL's Quality Assurance Program has not yet
reviewed t|je demonstration [§§u|ts, this bulletin presents prelimi-
nary results only. The key finding from the Solucorp MBS demon-
stration is"that the meap TQLP Jeacha.bjePb concentratipnin
..each of the three wastes/soils was Deduced to Jess than, the TCLP
regulatory limit of 5 mg/L. fable"" 1 presents the mean f6LP'
leachable Pb concentrations in the untreated and treated wastes/
soils. ' ' , ' , . '
Tibia 1. M«an TCLP Leachable Pb Concentrations, mg/L
Wasta/Sotl Untreated Treated
SF
SB
SW
SW {Retest)
28
17
36
15
0.18
0.70
"2.68
0.33
Other demonstration results include:
• The mean TCLP teachable As concentrations increased slighiiy
with treatment, but were below the TCLP regulatory limit of 5 mg/
L In eac|i of the untreated ipd treated wastes/soils.
• The mean TCLP leachable Cd concentrations were below the
TCLP regulatory limits of 1 mg/L in both the untreated and treated
SF and SB; the mean TCLP Cd concentrations in the untreated
and treated SW were 2.1 arid 1.1 mg/L, respectively. In the SW
relest, mean TCLP Cd values decreased from 0.5 to 0.01 mg/L.
• SPLPAs,Cd,andPbconcentrationswerebelowtheirrespective
regulatory limits in the treated and untreated SF, SB, SW, and
SW retest.
• Other than dilution effects, total metals concentrations were not
affected by the treatment process.
• Process throughput of untreated waste/soil averaged 52,59,56,
and 61 tons/hour for the SF, SB, SW, and SW retest, respec-
tively.
• Treated wastes/soils passed EPA's Multiple Extraction Proce-
dure (As, Cd, and Pb); however, no conclusion could be drawn
regarding the effect of treatment on long-term stability because
there was no change in the measured leachable metal concen-
trations from the treated to the untreated wastes/soils.
Total costs for treatment of approximately 2 million tons of SF,
SB, and SW were estimated assuming a system capacity of
10,000 tons per day. Based on scale-up from the demonstration
and information from Solucorp and other sources, costs were
estimatedI .at approximately $16/ton of waste/soil at the Midvale
Slag Site.
Thf EPA willpublish an Innovative Technology Evaluation Report
(ITER) and a Technology Evaluation Report (TER) in the fall of
1997. These reports will address final test results in detail, includ-
ing a complete analysis of analytical and geophysical results,
estimated processing costs, and observations on process reliabil-
ity and operating conditions made during the demonstration.
For Further Information Contact:
Thomas J. Holdsworth, SITE Project Manager
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
(513)569-7675
The mean volume increases in the treated SF, SB, SW, and SW
retest were 16,4,13, and 14 percent, respectively, as compared
to the excavated, untreated waste/soil.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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