[Federal Register: January 29, 2003 (Volume 68, Number 19)]
[Notices]
[Page 4481-4489]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr29ja03-64]
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ENVIRONMENTAL PROTECTION AGENCY
[FRL-7445-4; RCRA-2002-0029]
Land Disposal Restrictions: Treatment Standards for Mercury-
Bearing Hazardous Waste; Notice of Data Availability
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of data availability.
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SUMMARY: This notice of data availability (NODA) makes available to the
public two studies conducted on the treatment of mercury wastes. The
studies were initiated to help evaluate whether EPA could propose
treatment and disposal alternatives to the current land disposal
restriction (LDR) treatment standard of mercury retorting. The studies
were performed to assess conditions that affect the stability of waste
residues resulting from the treatment of high mercury (greater than 260
mg/kg total mercury) wastes. This NODA also makes available the results
of the peer review of these studies. As a result of our investigation,
we have concluded that changes to our national regulations are
impractical at this time. Additionally, this notice also provides
information on how to use the existing treatability variance procedures
to make site-specific choices on alternatives to mercury recovery. The
treatability studies and the results of the peer review are presented
here only to provide information--we are not
[[Page 4482]]
requesting comments on the mercury-related issues in this NODA.
ADDRESSES: You may view the supporting materials for this NODA in the
EPA Docket Center (EPA/DC), B102, EPA West, 1301 Constitution Ave. NW.,
Washington, DC 20460-0002. The docket number is RCRA-202-0029. To
review file materials, we recommend that you make an appointment by
calling (202) 566-0270. The EPA/DC is open from 9 am to 4 pm, Monday
through Friday, excluding Federal holidays. You may copy up to 100
pages from any regulatory document at no charge. Additional copies cost
$ 0.15 per page. For information on accessing an electronic copy of the
treatability study and peer review documents, see the SUPPLEMENTARY
INFORMATION section.
FOR FURTHER INFORMATION CONTACT: For general information, call the RCRA
Call Center at 1-800-424-9346 or TDD 1-800-553-7672 (hearing impaired).
Callers within the Washington Metropolitan Area must dial 703-412-9810
or TDD 703-412-3323 (hearing impaired). The RCRA Call Center is open
Monday-Friday, 9 a.m. to 4 p.m., Eastern Standard Time. For more
information on specific aspects of this NODA, contact Mary Cunningham
at 703-308-8453, cunningham.mary@epa.gov, or write her at the Office of
Solid Waste, 5302W, U.S. EPA, Ariel Rios Building, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. How Can I Get Copies of This Document and Other Related
Information?
A. Docket
B. Electronic Access
II. What Are the Treatability Studies and Peer Review Results?
A. Why Is Mercury a Concern?
B. What Is the Purpose of This NODA?
C. What Prompted the Treatability Studies?
D. What Are the Current Treatment Practices for Mercury Wastes?
E. What Earlier Studies Have Been Performed on Radioactive
Mercury Waste?
F. What Treatability Studies Are the Subject of Today's NODA?
G. What Were the Treatment Technologies Included in Our
Treatability Studies?
H. What Were the Study Results?
I. What Were the Peer Review Results?
J. What Conclusions Do We Reach From the Treatability Studies?
K. Why are Treatability Variances an Option for High Mercury
Wastes?
L. What Other Implications Arise From the Treatability Studies?
I. How Can I Get Copies of This Document and Other Related Information?
A. Docket
EPA has established an official public docket for this action under
Docket Number: RCRA-2002-0029. The official public docket consists of
the documents specifically referenced in this action and other
information related to this action. Although a part of the official
docket, the public docket does not include Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. The official public docket is the collection of materials
that is available for public viewing at the EPA Docket Center (EPA/DC),
B102, EPA West, 1301 Constitution Ave. NW., Washington, DC 20460-0002.
To review file materials, we recommend that you make an appointment by
calling (202) 566-0270. The EPA/DC is open from 9 a.m. to 4 p.m.,
Monday through Friday, excluding Federal holidays.
B. Electronic Access
You may access this Federal Register document electronically
through the EPA Internet under the ``Federal Register'' listings at
http://www.epa.gov/fedrgstr/.
An electronic version of the public docket is available through
EPA's electronic public docket and comment system, EPA Dockets. You may
use EPA Dockets at http://www.epa.gov/edocket/ to access the index
listing of the contents of the official public docket, and to access
those documents in the public docket that are available electronically.
Although not all docket materials may be available electronically, you
may still access any of the publicly available docket materials through
the EPA/DC facility identified above. Once in the system, select
``search,'' then key in the appropriate docket identification number.
II. What Are the Treatability Studies and Peer Review Results?
A. Why Is Mercury a Concern?
Mercury is an elemental metal, occurs in certain minerals and is a
naturally-occurring contaminant of some other natural resources, such
as certain types of coal. Once released into the environment, inorganic
forms of mercury may be converted to methylmercury, which is the main
form of organic mercury found in the environment. Methylmercury may
accumulate in fish tissue to levels that are unhealthful to humans and
which harm wildlife. Methylmercury has also been shown to be a
developmental toxicant, causing subtle to severe neurological effects
at very low levels of exposure, especially to fetuses and young
children.\1\ The developing fetus is exposed to mercury if the mother
eats mercury-contaminated fish during pregnancy. Recent
data,2 3 indicate that 8% of women of childbearing age in
the U.S. currently have blood mercury levels higher than EPA considers
to be a ``safe'' level of exposure.\4\ Children and adults can be
exposed to mercury if they routinely eat large quantities of
contaminated fish.
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\1\ http://www.epa.gov/waterscience/fish/.
\2\ http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5008a2.htm.
\3\ http://www.cdc.gov/nceh/dls/report/results/Mercury.htm.
\4\ http://www.epa.gov/triinter/tridata/tri00/qa.pdf.
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The problem of mercury-contaminated fish is wide-spread in the U.S.
As of December 2001, 44 states have issued fish advisories for mercury.
Twenty-four states have issued statewide advisories.\5\ These
advisories inform the public that concentrations of mercury have been
found in local fish at levels of public health concern. State
advisories recommend either limiting or avoiding consumption of certain
fish from specific water bodies or, in some cases, from specific water
body types (e.g., all freshwater lakes or rivers).
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\5\ http://www.epa.gov/waterscience/fish/.
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B. What Is The Purpose of This NODA?
Today's notice presents the results of two recent treatability
studies conducted to assess the feasibility of the treatment of high
mercury wastes (i.e., wastes containing greater than 260 mg/kg total
mercury) and elemental mercury destined for disposal. This notice also
presents the results of the independent peer review of these two
treatability studies.
The existing land disposal restrictions (LDR) treatment standards
require recovery by retorting of high mercury wastes. Based on the
results of the treatability studies published in today's NODA, we have
decided not to propose revisions to the existing treatment standards.
We are concerned that treatment (such as the treatment technologies
evaluated in our treatability studies) may not result in a waste that
is stable under some landfill conditions that are within the range of
normal operations.
Having said this, we believe there may be site-specific situations
where treatment and disposal of high mercury wastes or excess elemental
mercury may be warranted. In these instances, we could grant a petition
for a site-specific
[[Page 4483]]
variance from the applicable treatment standards under current
regulations. For a site-specific petition to be granted, it should
demonstrate that treatment of the waste significantly limits mobility
of mercury from the treated waste and that the treatment residues are
stable in the intended disposal environment.
C. What Prompted The Treatability Studies?
On May 28, 1999, EPA published an advance notice of proposed
rulemaking (ANPRM) requesting comment to help gain a better
understanding of the environmental impact of our waste treatment
standards for mercury-bearing hazardous wastes. In the ANPRM, we
requested data to support potential alternatives to current LDR
requirements to reclaim elemental mercury from high mercury subcategory
wastes (i.e., those wastes that contain greater than or equal to 260
mg/kg total mercury). However, we did not receive enough information to
propose changes to any of the mercury treatment standards. Therefore,
we initiated two research studies to identify the ``currently
available'' treatment processes and to gather information that could be
used to potentially change the current mercury treatment standards to
assure more effective treatment.
D. What Are the Current Treatment Practices for Mercury Wastes?
In this section, we describe the current regulatory categorization
for mercury wastes as low mercury subcategory wastes, high mercury
subcategory wastes, or elemental mercury wastes.
1. What Are the Current Treatment Practices for Low Mercury Subcategory
Wastes?
Low mercury wastes are those hazardous wastes containing less than
260 mg/kg of total mercury. Current regulations require that these
wastes be treated to achieve a certain numerical level, 0.20 mg/L,
measured using the Toxicity Characteristic Leaching Procedure (TCLP)
for mercury residues from retorting, and 0.025 mg/L TCLP for all other
low mercury wastes. These concentrations are generally met by
stabilization/solidification treatment. This subcategory of mercury
wastes was not included in any of the treatability studies described in
this notice.
2. What Are the Current Treatment Practices for High Mercury
Subcategory Wastes?
High mercury wastes are those hazardous wastes that contain greater
than 260 mg/kg total mercury. Because of this high concentration of
mercury, they are generally required to undergo roasting or retorting
(see ``RMERC,'' at 40 CFR 268.42, Table 1). RMERC is defined, in part,
as: ``Retorting or roasting in a thermal processing unit capable of
volatilizing mercury and subsequently condensing the volatilized
mercury for recovery.'' The residuals from the roasting or retorting
process are then subject to a numerical treatment standard as discussed
above (if the residues meet the definition of ``low mercury
subcategory'').
There may be cases where it is not desirable or practical to retort
high mercury subcategory wastes. One example of this would be mixed
radioactive high mercury wastes. See the discussion in Section II.K for
information on this category of mercury waste.
3. What Are the Current Treatment Practices for Elemental Mercury?
There are three elemental mercury waste streams that contain most
of the waste regulated under the LDR program:
(1) Discarded commercial elemental mercury, off-specification
elemental mercury, and container and spill residues (RCRA hazardous
waste code U151) that contain greater than or equal to 260 mg/kg total
mercury. These waste streams must be treated by roasting or retorting
(see ``RMERC'' at 40 CFR 268.42, Table 1).
Additionally, because the uses for elemental mercury in products is
declining, stockpiles of excess commodity (bulk) mercury currently
exist; if these stockpiles are deemed to be wastes, then they would
become subject to the ``RMERC'' standard.
(2) Elemental mercury contaminated with radioactive materials.
These waste streams are required to be treated by amalgamation (see
``AMLGM'' at 40 CFR 268.42 Table 1). AMLGM is defined as:
``Amalgamation of liquid, elemental mercury contaminated with
radioactive materials utilizing inorganic agents such as copper, zinc,
nickel, gold, and sulfur that results in a nonliquid, semi-solid
amalgam and thereby reducing potential emissions of elemental mercury
vapors to the air.''
(3) Characteristically hazardous elemental mercury wastes (RCRA
hazardous waste code D009) that also are required to be roasted or
retorted, if they contain greater than or equal to 260 mg/kg total
mercury.
E. What Earlier Studies Have Been Performed on Radioactive Mercury
Waste?
The Department of Energy's (DOE) Transuranic and Mixed Waste Focus
Area-Mercury Working Group, in conjunction with EPA, has initiated
studies of the treatability and disposal of mercury wastes resulting
from nuclear weapons production. These treatability studies have
evaluated current commercialized state-of-the-art technologies and
several emerging technologies. To date, DOE and EPA have conducted
several studies of the treatability of contaminated soils, surrogate
wastes, and bulk elemental mercury by commercial vendors. The goal of
the studies has been to identify the range of conditions suitable for
the disposal of these waste residuals, should direct treatment rather
than separation be performed. Sepradyne Corporation's vacuum retort
extraction, Nuclear Fuel Services, Inc. (NFS) DeHg[reg] stabilization
process, Brookhaven National Laboratory's sulfur polymer
solidification/stabilization, and ADA Technologies, Inc. (ADA) and
Allied Technology Group (ATG) sulfur-based solidification/stabilization
processes have been evaluated.
A 1999 DOE study \6\ examined the release of mercury from mercury
amalgams prepared by processes operated by ADA Technologies, Inc. (ADA)
and Nuclear Fuel Services, Inc. (NFS) as a function of temperature and
pH. Leachate exposure experiments indicate that amalgams prepared with
zinc released mercury at high rates into the leachate at acidic (low
pH) conditions and at lesser rates at neutral pH. These metal-based
amalgams tended to perform better in alkaline (high pH) solutions.
Sulfur-based treatment samples showed increased release of mercury
after two and three months at pH 12.5.\7\ Other studies of mercuric
sulfide solubility have detected increased solubility of mercury
sulfide complexes above pH 6 with excess sulfide present.\8\ Mercuric
sulfide is the product formed from treating elemental mercury with
sulfur or sulfide salts. The reports for these prior studies are
available on the internet.\9\
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\6\ C.H. Mattus, ``Measurements of Mercury Released from
Amalgams and Sulfide Compounds'', Oak Ridge National Laboratory,
ORNL/TM-13728, April 1999.
\7\ Ibid. Table 6, page 17.
\8\ Jenny Ayla Jay, Francois M. M. Morel, and Harold F. Hemond,
Mercury Speciation in the Presence of Polysulfides, Environmental
Science and Technology, 2000, Vol. 34, No. 11, pages 2196-2200.
\9\ See C.H. Mattus, ``Measurements of Mercury Released from
Solidified/Stabilized Waste Forms'', Oak Ridge National Laboratory,
ORNL/TM-2001/17, April 2001, available at http://osti.gov/bridge;
and F. Sanchez, D.S. Kosson, C.H. Mattus, and M.I Morris, ``Use of a
New Leaching Test Framework for Evaluating Alternative Treatment
Processes For Mercury Contaminated Mixed Waste (Hazardous and
Radioactive)'' http://www.cee.vanderbilt/cee/research_projects.html
.
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[[Page 4484]]
F. What Treatability Studies Are the Subject of Today's NODA?
The studies we just described did not focus on two types of mercury
waste that we thought were important to address: (1) High mercury
(containing greater than 260 mg/kg total mercury) waste sludges that
contain multiple forms of mercury; and (2) bulk elemental mercury.
We collaborated with DOE to evaluate the ability of commercially
available treatment processes to reduce the solubility of mercury in
these two types of waste and to identify stable disposal conditions as
a potential alternative to current regulations which require the
reclamation of mercury via roasting or retorting before treatment and
disposal of the residuals. Because this potential alternative (of
treatment/disposal as opposed to roasting/retorting) would result in
much higher concentrations of mercury potentially being land disposed,
and because of the toxic nature of mercury (see section II.A of this
notice) and the difficulty of treatment, we decided to evaluate treated
waste forms using the Toxicity Characteristic Leaching Procedure
(TCLP),\10\ as well as a constant pH leaching procedure that addresses
the range of pH conditions that could be expected in hazardous waste
landfill disposal environments. Because the TCLP only evaluates one pH
condition that results from the interaction of the waste and the fixed
acid content of the TCLP leaching solution, we thought it was important
to supplement the TCLP with the constant pH leaching procedure to
access the performance of the treatment residuals over the range of
normal landfill operating conditions. Using this procedure, we examined
waste solubility over a pH range from 2 to 12. Even though more extreme
conditions have been observed in landfills,\11\ a recent compilation of
landfill data finds that approximately 95 percent of all hazardous
waste landfills are in the 2 to 12 pH range, and more than 90 percent
are less than pH 10.\12\ By maintaining the pH constant at each level,
the test simulates the potential for metals to be extracted or
mobilized from the treated waste form by a large volume of landfill
leachate passing through and around the waste at the set pH level. This
also allows treatment performance to be compared at the set conditions.
An exposure period of 14 days, rather than the 18 hours of the TCLP,
was chosen to allow all samples time to reach near-equilibrium before
measurement of the release potential of mercury from the treatment
residuals. Other factors, such as leachate to solids ratio, oxidation/
reduction potential (eH), particle size, exposure period, and the major
ions present all affect metal solubility. However, the studies
presented here primarily focused on the effects of varying pH
conditions because the solubilities of metals and metal complexes are
highly pH dependent and the pH conditions of hazardous waste landfills
are known to vary widely.
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\10\ See 55 FR 11798, March 29, 1990 for more information on the
TCLP. The TCLP was originally developed to assess the plausible,
worst case mismanagement scenario for evaluating industrial waste
codisposed in a municipal solid waste landfill.
\11\ 65 FR 37945, June 19, 2000.
\12\ Characterization and Evaluation of Landfill Leachate
(Draft), SAIC, September 2000, page 3-33.
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The results of these two studies are provided in two reports:
``Technical Background Document: Mercury Wastes--Evaluation of
Treatment of Mercury Surrogate Waste'' and ``Technical Background
Document: Mercury Wastes--Evaluation of Treatment of Bulk Elemental
Mercury,'' available in the docket for today's notice. In this section,
we provide an overview of these studies.
The first study evaluated the effectiveness of four technologies to
stabilize a ``difficult-to-treat'' mercury waste, representing the wide
range of high mercury wastes that could require treatment. A surrogate
waste was designed for the study, which included an organic form of
mercury, elemental mercury, and several mercury salts in an inorganic
matrix. The surrogate waste was treated by each technology vendor. The
treated waste was then evaluated for mercury leachability, using both
the TCLP and an automated, constant-pH leaching protocol. Prior to
leach testing, waste form particles were reduced in size to 9.5 mm or
less. The waste forms were exposed to the leaching medium at a 20:1
liquid to solids ratio, and the pH was monitored and adjusted as
necessary by computer-controlled addition of acid or base. Constant pH
leaching was conducted at pH 2, 4, 6, 8, 10, and 12 for 14 days at each
pH. This leaching procedure and the waste surrogate are described in
detail in the Technical Background Documents, available in the docket
for today's notice.
The second study evaluated the ability of three technologies to
convert elemental mercury into a stable waste form. The study was
designed to assist in evaluation of options for disposition of the
inventory of mercury in the Defense Logistics Agency (DLA) stockpile.
Bulk elemental mercury was treated by each technology vendor, and the
treated waste residuals were evaluated for mercury leachability, using
the same protocols and conditions as those used in the first study.
In both studies, the total concentration of mercury was measured in
samples of the untreated starting material (either surrogate waste or
bulk elemental mercury), in the treated waste form, and in leachates
(both TCLP and constant pH leaching). In addition, samples of the
untreated and treated material were characterized, including
measurements of bulk density, moisture content, percent organic matter,
cation exchange capacity and particle size distribution.
Each of the technologies evaluated in these studies relies on
chemical reactions to minimize volatilization and solubility, rather
than on recovery or separation technologies which generate a near
mercury-free residual in addition to concentrated or purified mercury.
These treatment processes are summarized below.
G. What Were the Treatment Technologies Included in Our Treatability
Studies?
Four commercial treatment vendors participated in studies of the
treatability of the surrogate waste. Because the actual commercial
amalgamation processes are proprietary, we refer to the aforementioned
treatment technologies as ``vendors'' to mask their identity. Each of
the four vendors' processes utilized reagents to bind the mercury forms
present as various sulfides. The following table presents a comparison
of these technologies.
[[Page 4485]]
Table 1.--Technologies Used for Surrogate Sludge Treatment
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Vendor
Comparison factor -------------------------------------------------------------------------------
A B C D
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Process Overview................ Sulfur Formation of Sulfur Formation of
amalgamation mercuric sulfide amalgamation mercuric sulfide
followed by followed by micro- followed by followed by
thermoplastic and addition of solidification
encapsulation. macroencapsulatio proprietary with a
n with precipitation proprietary
proprietary reagent. cement-containing
binders and stabilization
coating agents. agent.
Reagents........................ Sulfur polymer, Sulfide and Sulfur and Sulfide and
organic modifier, proprietary proprietary proprietary
and proprietary binders and precipitation cement-containing
additives. coating agents. reagent. stabilization
agent.
Waste Loading\**\ (on dry basis) 30 wt%............ 72 wt%............ 44.9-47 wt%....... 25.4 wt%.
Final Form...................... Uniform solid mass Uniform solid mass Granular.......... Uniform solid
mass.
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** Waste loading is the percentage of waste in the treated residue.
Three of the vendors also participated in the treatment of
elemental mercury. Vendor D did not participate in this study. Vendors
A and B used the same general process for elemental mercury. However,
Vendor C used a process that differed from what was used in the
surrogate sludge treatment. The following table presents a comparison
of the technologies used in the treatment of elemental mercury.
Table 2.--Technologies Used for Elemental Mercury Treatment
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Vendor
Comparison factor --------------------------------------------------------------------------
A B C
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Process Overview..................... Sulfur amalgamation Formation of mercuric Amalgamation followed
followed by sulfide followed by by addition of
thermoplastic micro- and proprietary
encapsulation. macroencapsulation precipitation reagent.
with proprietary
binders and coating
agents.
Reagents............................. Sulfur polymer, organic Sulfide and proprietary Amalgamation agent and
modifier, and binders and coating proprietary
proprietary additives. agents. stabilization reagent.
Waste Loading\**\ (on dry basis)..... 33 wt%................. 44 wt%................. 20.1 wt%.
Final Form........................... Uniform solid mass..... Uniform solid mass..... Uniform solid mass.
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** Waste loading is the percentage of waste in the treated residue.
H. What Were the Study Results?
1. What Were the Study Results for the Surrogate Mercury Waste?
Presented in Table 3 and discussed below are the constant pH
leaching results for the surrogate mercury waste. Additional testing
results (raw data, tables, and graphs) are presented in the report
``Technical Background Document: Mercury Wastes--Evaluation of
Treatment of Surrogate Mercury Wastes,'' available in the docket for
today's notice.
Table 3.--Surrogate Mercury Waste Treatment Study--Constant Leaching Results (mg/L Mercury)
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Vendor A \**\ Vendor C Vendor D
pH ---------------------------------------------- Vendor B -----------------------------------------------------------------------------------------
Pellets Crushed Batch 1 Batch 2 Batch 1 Batch 2
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2\*\............................. 0.00251/ 0.00682/ 1.92/ 0.356/ 4.39/ 0.127/ 0.257/
0.00856 0.00294 0.617 13.9 1.11 0.0775 0.130
4................................ 0.00483 0.00555 0.137 0.0816 0.0340 2.63 4.35
6................................ 0.00425 0.0140 0.102 0.0441 0.118 0.240 0.289
8\*\............................. 0.0127/ 0.00180/ 0.0873/ 0.0391/ 0.0106/ 0.0603/ 0.0724/
0.00424 0.00139 0.0753 0.0206 0.00797 0.0594 0.0658
10............................... 0.00734 0.00378 0.0577 0.0108 0.00337 2.17 0.0204
12\*\............................ 0.111/ 0.781/ 0.00885/ 0.0353/ 0.00239/ 0.0156/ 0.0250/
0.157 0.136 0.00609 0.0336 0.00264 0.0109 0.0193
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\*\Duplicate analyses were performed at pH levels 2, 8 and 12.
\**\Vendor A provided cast <9mm pellets and a larger material that was crushed to yield a <9 mm form for analysis.
Each vendor's treatment of surrogate waste achieved a significant
reduction in mercury release in comparison to the untreated waste form.
However, there are significant differences in the effectiveness of the
various technologies. Vendor A's stabilized waste leached less than
0.025 mg/L \13\
[[Page 4486]]
over the range of pH 2 to 10. However, when exposed to very alkaline
conditions of pH 12, the waste leached 0.111 to 0.157 mg/L in the
pellet form and 0.136 to 0.781 mg/L in the crushed form. Vendor B's and
Vendor C's stabilized wastes leached increasingly higher levels of
mercury at the acidic conditions of pH 4 and lower. Vendor B's
stabilized waste achieved 0.025 mg/L only at pH greater than 10. Vendor
C's stabilized waste achieved 0.025 mg/L only at pH greater than 6 in
one of the two batches. Vendor D's stabilized waste achieved 0.025 mg/L
only at pH greater than 10.
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\13\ The current treatment standard for low-level mercury wastes
that have not undergone roasting or retorting is 0.025 mg/L mercury,
as measured by the TCLP. Treatment results are presented relative to
this numerical benchmark for comparison purposes.
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2. What Were the Study Results for Elemental Mercury?
Presented in Table 4 and discussed below are the constant pH
leaching results for the bulk elemental mercury study. Additional
testing results (raw data, tables and graphs) are presented in the
report ``Technical Background Document: Mercury Wastes--Evaluation of
Treatment of Bulk Elemental Mercury,'' available in the docket for
today's notice.
Table 4.--Bulk Elemental Mercury Treatment Study--Constant Leaching Results (mg/L Mercury)
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Vendor A
pH ------------------------------------------ Vendor B Vendor C
Pellets Crushed
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2\*\........................... 0.00542/ 0.00658/ 0.00105/ 29.7/
0.0137 0.0132 0.00156 27.9
4.............................. 0.984 0.0621 0.00186 0.315
6.............................. 0.0835 16.7 0.00484 0.0323
8\*\........................... 44.9/ 30.8/ 0.011/ 0.0494/
24.3 53.5 0.00832 0.368
9.............................. 13.7 NA NA NA
10............................. 0.0742 0.0839 0.0118 0.139
11............................. 0.00951/ NA NA NA
0.0177
12\*\.......................... 127/ 74.6/ 0.143/ 0.0251/
155 23.5 0.0672 0.0249
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\*\Duplicate analyses were performed at pH levels 2, 8 and 12.
NA--Not Analyzed.
Significant differences were observed between vendors in the
treatment of elemental mercury. Vendor A's stabilized elemental mercury
exhibited highly variable leaching as a function of pH. The variability
observed prompted additional testing at pH 9 and pH 11 to verify and
better characterize the significant swings in leachate mercury
concentration. Leaching increased from less than 0.01 mg/L at pH 2 to
over 24 mg/L at pH 8, reached a minimum of 0.009 mg/L at pH 11, then
increased significantly as it approached pH 12 (to greater than 127 mg/
L). Vendor B's stabilized elemental mercury shows a gradual increase in
mercury leaching (from levels of 0.001mg/L to 0.15 mg/L) with the
increasing pH of the leachate fluid. Vendor C's stabilized elemental
mercury showed a pattern of decreased leaching with increasing pH,
approaching the level of 0.025 mg/L only at a pH of 12. These results
clearly show that there are significant differences in the
effectiveness of the various treatment technologies. More importantly,
the results show that leaching of mercury from the stabilized elemental
mercury is pH dependent.
One treatment vendor in Europe, Bj[auml]sta [Aring]tervinning, has
developed a mercury treatment process that results in the formation of
mercuric selenide. This vendor was one of the treatment vendors that
submitted proposals to the Department of Defense's Defense Logistic
Agency (DLA), expressing interest in treating their stockpile of
elemental mercury. Mercuric selenide is indicated by solubility
calculations to be one of the more insoluble mercury salts. Even though
our study was underway, when we learned of Bj[auml]sta
[Aring]tervinning's proposal to treat the DLA stockpile, we were very
interested in including their treated waste form in our study. Due to
logistical difficulties, we were unable to obtain a treated waste form
from this vendor. We were, however, able to obtain laboratory-grade
mercuric selenide and conduct limited leachate studies at pH 7 and 10
which bracket the conditions found at many landfills.\14\ We also
assessed the effects of the addition of 500 ppm of chloride at pH 7 and
10. Unlike the other treated waste forms formed from treatment using a
variety of reagents, the final waste form in this case was a known
compound: Mercury selenide. Thus, there was readily available
information on mercuric selenide solubility and the potential
significant effects of chloride on that solubility. Geochemical
solubility calculations for the mercuric selenide compound indicated
that chloride ions would promote the solubility of mercury. Chloride
ions tend to form strong soluble complexes with mercury, greatly
increasing mercury's mobility. While mean groundwater chloride
concentrations are approximately 160 mg/L, landfill leachates range
from 59 to 6,560 mg/L in industrial landfills and 96 to 31,100 mg/L in
hazardous waste landfills.\15\ In our study, more than a three-fold
increase in solubility was observed at both pH conditions with the
addition of 500 ppm of chloride. At pH 7, the leachate concentration of
mercury increased with the addition of chloride from 0.006 mg/L to
0.021 mg/L; at a pH of 10, the concentration of mercury increased from
0.028 mg/L to 0.11 mg/L. This indicates that major ions present in a
given disposal environment may significantly impact the release of
mercury from the treated waste form.
---------------------------------------------------------------------------
\14\ Characterization and Evaluation of Landfill Leachate
(Draft), SAIC, September 2000.
\15\ Ibid.
---------------------------------------------------------------------------
I. What Were the Peer Review Results?
The complete results of the Peer Review are provided in the docket
to today's notice (Docket Number: RCRA-2002-0029), along with EPA's
responses to the Peer Review comments.
[[Page 4487]]
1. What Questions Were Asked of the Peer Reviewers?
In order to provide a more complete analysis, and in accordance
with EPA policy, we presented the two new studies for formal,
independent peer review. The three peer reviewers selected for this
process are national experts with significant technical expertise in
hazardous waste leaching, have no prior association with these studies,
and have no perceived or actual conflict with any impact of the study
results. The members of the peer review panel were tasked with
evaluating the adequacy of the experimental design, conduct, and
conclusions of the two studies. The peer review panel also provided
information on how the studies can be used to provide a framework to
determine whether additional protective measures are required to
prevent loss of mercury to the environment from the treatment and co-
disposal of mercury-bearing wastes in landfills.
Additionally, the members of the peer review panel were asked if
additional studies were warranted for other factors that impact
solubility (e.g., liquid/solid ratio, redox conditions, leachate
composition) or affect ability to leach (such as use of
macroencapsulation).
2. What Did the Peer Reviewers Say About the Study of the Treatment of
Mercury Surrogate Wastes?
Two of the peer reviewers stated that the experimental design was
appropriate for the study. One reviewer, however, said the design did
not follow the Data Quality Objectives (DQOs) process, and argued that
there is little relationship between the objectives and the design. We
disagree with this reviewer, however. EPA has developed the DQOs
process as the Agency's recommended planning process when environmental
data are used to select between two opposing conditions, such as
achieving or not achieving a numerical standard.\16\ The DQOs process
is used to develop qualitative and quantitative statements of the
overall level of uncertainty that a decision-maker is willing to accept
in results or decisions derived from environmental data, i.e., Data
Quality Objectives. The DQOs process entails a seven step systematic
procedure for defining the criteria that a data collection design
should satisfy, including when to collect samples, where to collect
samples, the tolerable level of decision error for the study, and how
many samples to collect, balancing risk and cost in an acceptable
manner. When this process is not directly applicable (i.e., the
experimental objective is estimation, research, or any other objective
that does not select between two distinct conditions), the Agency
recommends the use of a systematic planning method for defining
performance criteria.\17\ For this research project, a systematic
planning method was used. The project planning process used and the
planning documents development were guided and overseen by EPA/ORD
staff, and the Quality Assurance Project Plan (QAPP) was reviewed and
approved by an EPA/ORD quality assurance expert. EPA believes that the
project objectives and criteria were logical, given the intended end-
use of the data, well-defined, and achievable.
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\16\ See EPA/600/R-96/055; Guidance for the Data Quality
Objectives Process. http://www.epa.gov/quality/qs-docs/g4-final.pdf
\17\ Ibid.
---------------------------------------------------------------------------
The three reviewers all stated that the study was conducted
properly. The three reviewers also stated that the studies met the
objectives of: (1) Evaluating the ability of alternative treatment
technologies to achieve a goal of 0.025 mg/L or less for the
stabilization of mercury over a range of pH levels from 2 to 12; and,
(2) to compare constant pH leaching protocol results to standard TCLP
results. Two of the reviewers evaluated the ability of each treatment
technology to meet the treatment goal, and concluded that the ability
of each technology to meet the treatment goal in the constant pH
leaching was pH-dependent.
The reviewers suggested additional studies to fill in specific data
gaps. One reviewer noted that additional extractions up to at least pH
12.5 are needed to supplement the report. While we agree evaluation of
a broader range could be helpful, we do not believe that additional
studies are cost effective, because only a small fraction of hazardous
waste landfills have been observed to have leachates above pH 12. In
cases where disposal is proposed at or above pH 12.5, additional data
for such conditions may be necessary to establish that treatment is
effective for the expected disposal conditions. (See section II.F of
today's notice for a discussion of pH levels in hazardous waste
landfills.)
Another reviewer suggested that two or more actual wastes (rather
than surrogates) containing over 260 mg/kg of mercury be subjected to
stabilization and leaching by the TCLP as well as by the constant pH
protocols. EPA agrees that using actual wastes, rather than surrogates,
for treatability tests can be desirable. However, in many cases during
the history of establishing treatment standards in the BDAT program,
EPA has used surrogates in lieu of actual wastes, whenever
representative ``hard-to treat'' wastes were not readily obtainable.
Specifically, in the case of characteristic wastes, which can be
extremely variable, using a surrogate allows us to evaluate a ``hard-
to-treat'' waste. Using a ``hard-to-treat'' waste is useful if the
ultimate treatment results will be used for other forms of that waste,
which in the case of a characteristic waste like D009, is likely the
case. In the studies discussed in this notice, where we were trying to
determine how these forms of mercury would respond to treatment and
determine how the treated waste forms would react to various pH
environments, we are comfortable that using surrogate wastes did not
diminish the value of the studies.
3. What Did the Peer Reviewers Say About the Elemental Mercury Study?
One of the peer reviewers agreed that the experimental design was
appropriate for the study. Another reviewer said that a statement of
acceptable errors should have been included (e.g., a treatment
technology must be effective on 90% of wastes with a 90% confidence).
Without such a statement, he said, it is difficult to decide when a
technology provides adequate treatment. EPA believes that a statement
of acceptable errors as constructed by the reviewer was not
appropriate. The objective of the study was to determine how these
forms of mercury would respond to treatment and to determine how the
treated waste forms would behave in various pH environments.
Another reviewer also said the experimental design was generally
appropriate; however, it failed to confirm that concentrations of
elemental mercury in the treated wastes were at the values reported by
the vendors. He added that the recoveries (i.e., measure of total
mercury present) for treated elemental mercury wastes submitted by
Vendors A and C are so low that they cast doubt on the results of the
leach tests. We disagree. The analysis of mercury content of the
treatment residuals and that of the leachates are two distinct
analyses. The low recoveries for the treated elemental mercury wastes
were a result of the difficulty in digesting the solid waste form to
dissolve the mercury and make it available for analysis; as a result,
waste loadings reported by the vendors could not be verified. Regarding
the leach tests, all spike recovery measurements of the leachates
achieved
[[Page 4488]]
quantitative recoveries between 84% and 109%. Thus, there is no
evidence of a problem with the analysis of mercury in the leachates. We
believe this is because the mercury was in solution, and therefore,
available for analysis.
All reviewers said that the study was conducted properly. Reviewers
were then asked whether the stated objectives were adequately met. All
reviewers agreed that the studies met the objectives of: (1) Evaluating
the ability of alternative treatment technologies to achieve a goal of
0.025 mg/L or less for the stabilization of mercury over a range of pH
levels from 2 to 12; and, (2) to compare constant pH leaching protocol
results to standard TCLP results.
The reviewers all agreed that the results of the bulk elemental
mercury study supported the conclusion that the presence of chloride
ions in a given disposal environment may significantly impact the
release from a treated waste form (mercury selenide).
4. What Additional Studies Are Recommended?
When asked if further studies were recommended for other factors
that impact solubility, one reviewer recommended additional extractions
up to at least pH 12.5. Again, as described above, we do not agree that
additional studies are warranted for this pH range, as few landfills
have been shown to maintain pH conditions in excess of pH 12. This
reviewer also recommended that mercuric selenide waste should be
evaluated over the range of pH 2 to 12.5, with varied chloride content
in the leachate. We agree that if additional studies were planned, it
would be useful to further investigate mercuric selenide or elemental
mercury treated to a mercuric selenide composition across a wider range
of pH values than the 2 pH conditions in our study. We also believe
that varying chloride content and other potentially significant
variables across the pH range for all waste forms would be a useful
study, and would provide additional information on the potential
effects of chloride content in landfill leachate.
5. Must Site-Specific Disposal Conditions Be Considered Along With
Appropriate Treatment Technology as Decisions Are Made About Disposal
of Mercury Wastes?
Peer reviewer opinions were mixed as to whether the studies
supported the assertion that site-specific disposal conditions must be
considered along with appropriate treatment technology as decisions are
made about disposal of mercury wastes. One reviewer stated that the
studies provide useful data on pH and chlorides, but do not provide
adequate support for an absolute requirement. The reviewer also stated
that, ``For any disposal of hazardous wastes, treated or untreated, it
is scientifically preferable to use site-specific information.'' This
reviewer maintained, however, that requiring the factoring of site-
specific conditions into decision making is not always feasible.
Another reviewer's comments countered that these research results do
support the assertion, because they demonstrate that leaching fluids,
which vary greatly in pH under different disposal conditions, can have
an important impact on the amount of mercury leached from the treated
wastes. The third reviewer suggested that if several actual wastes have
been tested and are shown to be stable at all pH values, then selection
of stabilization technology would not require any site-specific
considerations. We do not agree with this reviewer's comment, because
we believe that there are other factors (redox conditions, presence of
chlorides, etc.) besides pH, which would likely impact the solubility
of the treated waste form.
The complete results of the peer review are provided in Docket
Number: RCRA-2002-0029, along with EPA's responses to the peer review
comments.
J. What Conclusions Do We Reach From the Treatability Studies?
For wastes containing a wide range of mercury compounds, treatment
can result in a residual of reduced solubility under certain pH
conditions. Our treatability studies showed that the leaching of
mercury out of the stabilized waste form varied with pH. We saw that
some of the vendor's treatment of surrogate waste performed better in
certain pH ranges. For example, Vendor A performed best (i.e., achieved
levels less than 0.025 mg/L) except in very alkaline conditions (i.e.,
when the pH was greater than 10), whereas Vendor B's treatment
performed best only under very alkaline conditions. Because the pH in a
hazardous waste landfill can vary anywhere from near pH 2 to over pH
12, it appears that none of the treatment processes tested in the
studies presented here are effective for the entire range of pH levels
that could exist.
We find that the evaluated processes are effective to a degree for
the treatment of elemental mercury wastes. Several have been
demonstrated to achieve 0.025 mg/L or better under certain pH
conditions. However, vapor pressure measurements \18\ and observation
of small droplets of mercury in some samples of the treated wastes lead
us to believe that some treatment processes did not result in complete
treatment of all the elemental mercury in every test sample. We also
believe that the testing conditions cannot be considered to be worst-
case, because the additional presence of sulfide and chloride ions in
leachates can promote formation of soluble mercury complexes.
---------------------------------------------------------------------------
\18\ C.H. Mattus, ``Measurements of Mercury Released from
Solidified/Stabilized Waste Forms,'' Oak Ridge National Laboratory,
ORNL/TM-2001/17, April 2001. Available at http://osti.gov/bridge.
---------------------------------------------------------------------------
The physical properties of elemental mercury present significant
challenges to its long-term management. Mercury cannot be destroyed.
Elemental mercury is easily vaporized due to its vapor pressure at
ambient temperatures. Also, elemental mercury is not significantly
soluble \19\ and therefore not readily detected by short term leachate
tests, such as the TCLP. Disposal of large amounts of elemental mercury
require control of both volatilization losses and any subsequent
solubilization in leachates. Thus, for protective long-term management
in a disposal environment, elemental mercury first has to be treated to
convert it to a form with reduced volatility and solubility, and then
measures must be put into place to prevent these treatments from being
degraded once the properties of the treatment residual have been
determined.
---------------------------------------------------------------------------
\19\ The solubility of elemental mercury is 0.056 mg/L at
25[deg]C (MERCK Index).
---------------------------------------------------------------------------
The physical properties of mercury also present treatment
challenges. At ambient conditions, mercury is an extremely dense liquid
with high surface tension. It does not appreciably dissolve into, or
adhere to, wastes or environmental media, and because of its density
and surface tension, it is extremely difficult to distribute
homogeneously through the treatment reagents. Consequently, large
volumes of treatment reagents are needed to contact and react with the
elemental mercury, resulting in low waste loadings and large volume
increases.
The current treatment standard for high mercury and elemental
mercury wastes is recovery of mercury followed by land disposal of any
treatment residuals that pass a leaching standard.\20\ The results of
the treatability studies outlined in this notice lead us to conclude
that, at this time, we cannot
[[Page 4489]]
establish a new national treatment standard allowing for disposal of
high mercury and elemental mercury wastes. We continue to believe that
the current recovery standard is the most appropriate standard for most
high mercury waste. No technology demonstrated adequate stability
across the plausible range of pH conditions found in landfills. We
recognize that other factors, including leachate salinity, can have a
significant effect on the solubility of treated mercury wastes. These
other factors may be the reason that we have not been able to find a
single technology that is effective in all or many situations.
---------------------------------------------------------------------------
\20\ Residuals that do not pass the leaching standard would
require additional treatment to meet the standard for the applicable
subcategory of mercury waste.
---------------------------------------------------------------------------
K. Why Are Treatability Variances an Option for High Mercury Wastes?
While these circumstances do not allow us to modify or provide an
alternative national treatment standard for high-mercury hazardous
wastes to allow for disposal, we are deferring to our variance process
for stakeholders who believe it would be appropriate to use an
alternative treatment technology for their wastes and expected disposal
conditions. Under 40 CFR 268.44(h), we allow facilities to apply for a
site-specific variance for wastes generated under conditions specific
to only one site. In such cases, the generator or treatment facility
may apply to the Administrator, or EPA's delegated representative, for
a site-specific variance from a treatment standard.
In cases where roasting and retorting for a certain waste is
inappropriate, a generator can consider petitioning for a site-specific
variance from that treatment standard. At a minimum, the generator
would want to look for the treatment technology that would be most
effective in the expected pH range for the chosen disposal site. In
general, for a site-specific petition to be granted, it should
demonstrate that treatment has occurred and that the treatment residues
are stable in the intended disposal environment.
For example, a variance may be appropriate for a high mercury
subcategory waste that also is radioactive (i.e., a mixed waste). The
current regulations require high mercury-organic subcategory mixed
wastes be treated by retorting (RMERC) or incineration (IMERC) and high
mercury-inorganic subcategory mixed wastes be treated by RMERC. At the
time of promulgation, the assumed approach for compliance with these
regulations was separation of the mercury from the wastes and recycling
of the pure elemental mercury back into commerce. However, this assumed
compliance scenario is invalid for mixed wastes containing mercury
because there is no use for recovered mercury that is radioactively
contaminated.
To manage this type of waste, it would appear reasonable to use, on
a site-specific basis, the ``inappropriate'' variance approach (Sec.
268.44(h)(2)(i)). A petitioner using this approach would necessarily
have to describe the specifics and likely effectiveness of the
stabilization treatment that will be used. As demonstrated by the
studies described in today's notice, the stability of treated waste
forms can be highly dependent on pH conditions. In determining whether
the proposed technology is protective, EPA would expect the petitioner
to demonstrate the technology's effectiveness under the planned
disposal conditions.
LDR variance petitions should be submitted in accordance with the
procedures in 40 CFR 260.20. Petitions should include, among other
things, a description of the process that generates the waste, the
rationale for the variance request, and data on the proposed waste
treatment process.\21\ Site-specific circumstances often dictate the
types and amount of information that we will need to evaluate a
petition, so stakeholders who are considering petitioning for a
treatment variance should engage EPA early in the process to ensure all
of the necessary information is, or will be, available.
---------------------------------------------------------------------------
\21\ Note that when submitting data, petitioners should also
include evidence that appropriate quality assurance/quality control
procedures were followed in generating the data. For guidance, see
Final Best Demonstrated Available Technology (BDAT) Background
Document for Quality Assurance/Quality Control Procedures and
Methodology; USEPA, October 23, 1991.
---------------------------------------------------------------------------
L. What Other Implications Arise From the Treatability Studies?
Because these treated waste forms may be chemically altered by
environmental conditions, macroencapsulation prior to land disposal
could be used to provide a barrier against leachate intrusion and
attack on the treated mercury waste. Macroencapsulation would also
provide a barrier to reduce emissions of elemental mercury vapors. In
order to meet the performance requirements of 40 CFR 268.45, Table 1,
the macroencapsulation treatment must completely encapsulate the waste
and be resistant to degradation by the waste, its contaminants, and
materials into which it may come into contact after placement. We
promulgated such a requirement for wastewater treatment sludge from the
production of vinyl chloride monomer using mercuric chloride catalyst
in an acetylene-based process; hazardous waste K175 (65 FR 67068,
November 8, 2000). For K175 wastes, we estimated that
macroencapsulation and placement in a hazardous waste landfill
utilizing high density polypropylene vaults adds an additional $150 to
$200 per ton of waste disposed to the treatment costs.\22\ For a review
of the current state of encapsulation technologies and materials being
used to immobilize elemental mercury, mercury-contaminated wastes,
soils, or sludges, see the technical report ``Advances in Encapsulation
Technologies for the Management of Mercury-Contaminated Hazardous
Wastes,'' Battelle, August 30, 2002, available in the docket for this
notice.
---------------------------------------------------------------------------
\22\ Economics Background Document--USEPA Final Rule Listing
Wastewater Sludges Generated By Chlorinated Aliphatic Chemical
Manufacturing Facilities, as RCRA Hazardous Waste Codes K174 and
K175: Industry Profile and Estimation of Regulator Costs; page 74.
http://www.epa.gov/epaoswer/hazwaste/id/chlorali/ca_ebd.pdf_____________________________________-
Having concluded that treatment residues of elemental mercury are
potentially subject to attack by leachates and that the technologies
may not have fully reacted with the mercury, we are evaluating whether
to propose modifying the treatment standards for the radioactive
elemental mercury waste subcategories of U151 and D009. The current
treatment standard for these wastes is amalgamation (AMLGM). We could
propose, for example, to replace this standard with the more
restrictive requirement of amalgamation followed by macroencapsulation.
We could also require post-treatment testing to ensure effective
treatment. If we decide to amend the treatment standards, we would
publish a proposed rule for public comment.
Dated: January 22, 2003.
Robert Springer,
Director, Office of Solid Waste.
[FR Doc. 03-2035 Filed 1-28-03; 8:45 am]
BILLING CODE 6560-50-U