EPA/600/A-93/160
Management of Arsenical Wood Preserving
Residuals by Recovery and Immobilization
Ronald J. Turner
U.S. Environmental Protection Agency
Cincinnati, Ohio
Mary Beth Foerst
IT Corporation
Cincinnati, Ohio
AIR & WASTE MANAGEMENT
ASSOCIATION
«
SINCE 1907
For Presentation at the
86th Annual Meeting & Exhibition
Denver, Colorado
June 13-18, 1993
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93-RP-131B.05
INTRODUCTION
Pentavalent arsenical compounds of varying fornulations have
been used as wood preservatives in substantial quantities for
over 50 years. Currently, there are five arsenical wood
preservative formulations listed in the American Wood Preservers
Association Standards: Type ft, B, and c chromated copper
arsenate (CCA), ammoniacal copper arsenate, and ammoniacal copper
zinc arsenate. Type C CCA wood preservative contains 34 percent
arsenic, 18.5 percent copper, and 47.5 percent chromium. Type C
is the predominant arsenical, water soluble, wood preservative
formulation used in the U.S. for applications such as decks,
docks, foundation and marine piling, fences, and utility
poles.fl)
The EPA is evaluating performance of alternative techno-
logies, including processes utilizing immobilization and metal
recovery/reuse, for treatment of CCA wood preserving wastes. The
arsenic residual wastes are classified under the Resource
Conservation and Recovery Act (ROW) as F035. The category
includes wastewater, process residuals, drippage, and spent
formulations generated at plants that use inorganic preservatives
containing arsenic or chromium* The disposal of waste CCA
treated wood is not specified in the F035 classification.
CHARACTERISTICS OF ACTIVE CCA FACILITIES
The distribution of preservative use by the wood preserving
industry in 1989 is summarized in Table 1. Seventy seven percent
of these plants use inorganic arsenical wood preservatives.
The CCA Is shipped to the treatment facility as a 50 percent
concentrate. The concentrate is diluted with water to a 1-2
percent ccft working solution. The preservative is applied by
pressure processes. The two methods used commercially are full
cell and modified full cell. The treatment cycle consists of 1)
applying an initial vacuum to remove air entrained in the wood;
2) flooding the treatment vessel with preservative; 3)
pressurization to about 150 psig; 4} draining the excess
preservative; 5) depressurizing and applying a vacuum to remove
free liquid from the wood; 6} returning the free liquid to the
work tank; ?} and opening the treatment vessel and removing the
wood. The complete cycle takes about one hour. The treated
lumber sits on a drip pad for about 24 hours before transfer to
storage.
Wood preservation facilities using inorganic compounds
typically have no net generation of wastewater. The rain runoff
from storage and liquids from the sump under the treatment vessel
are filtered and recycled to the work tank. The screenings and
other potentially hazardous solid process wastes are drummed for
offsite disposal. This is F035 as defined in 55FR 504501,
12/6/90. The quantity of waste generated annually range from a
few drums at newer facilities to a dozen or more drums from older
facilities, due to housekeeping practices and other production
factors. The facilities are required to manage their process
residuals by contracting with commercial waste removal and
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93-RP-131B.05
RCRA-permitted/disposal companies. Some facilities rely on the
suppliers of the preservatives for Baste consolidation and ship-
ment.
Three CCA wood treatment facilities were visited by EPA for
sampling and analysis. The metals data are summarized in Table
2. The highest arsenic concentration in the samples from
residues destined for offsite disposal was 15 percent. The
highest chromium concentration was 9 percent. Copper was also
present in concentrations up to 10 percent. Other toxic metals
in the screened solid samples in low or moderate concentrations
included lead (80 to 190 »g/kg), mercury (1 to 3 mg/kg), and
cadmium (0 to 200 mg/kg). Additional elements were present at
concentrations considered typical for these waste streams.
IMMOBILIZATION
The treatment process of immobilization, also known as
solidification/stabilization (s/s), chemical fixation or
encapsulation, is commonly applied when the contaminants consist
of "heavy" metals such as cadmium, trivalent chromium, and lead
at low to moderate concentrations, additives or binders are
mixed with the waste to immobilize and reduce the solubility of
the inorganic hazardous constituents. Binding agents typically
used are Portland cement, cement and flyash, lime and flyash, and
dust from cement and lime kilns.
If the form of arsenic in the waste is arsenite or arsenate
(oxyanions), the usual metal hydroxide formation mechanism does
not apply and the stabilization of arsenic with conventional
binders can be unsatisfactory and result in incomplete
immobilization.(1) The arsenic in the screened solids were not
speciated. However, the arsenate in the CCA is reduced to
arsenite in the wood preserving process.
Purpose and Scope
The objectives of the immobilization studies were to
determine if this technique can be applied to inorganic wood
preserving wastes and to characterize the effect of
immobilization on the waste. Two immobilization tests were
conducted with F035 obtained in cooperation with a commercial
treatment, storage and disposal facility (TSD). One series of
tests was conducted at a research facility, and employed
conventional binders such as cement and flyash; the other
represented the process in service at the TSD for wastes
containing chromium or other heavy metals: a waste shredder,
conveyor belt, blender, pugmill, and a final ribbon blender.
Portland cement was the binder used by the TSD for the F035. The
unconfined compressive strength test was used by the research
facility to measure the physical strength and the Toxicity
Characteristic Leaching Procedure (TCLPj was used as an
indication of the chemical leachability of the contaminants from
the immobilized waste. The TSD's RCRA permit requires chromium
reduction from hexavalent to trivalent and a TCLP less than 5.0
ng/L prior to final disposal in a landfill cell.
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. 93-RP-131B.05
TSD Procedures
The TSD received 43 drums of F035 waste which were
consolidated from six different CCA wood treating facilities.
The drums were emptied into a 20 cubic foot steel rolloff
container and mixed with a backhoe for 30 minutes. About 6 cubic
feet of the mixture was transferred to an 8 foot diameter trough
for additional nixing prior to collecting the F035 samples for
analytical characterization and laboratory tests. The rolloff
container with the remaining material was then noved to the
stabilization facility for processing. Portland cement was added
at 20 percent by weight in the pugmill. Ferrous sulfate was
added to the first blender at a predetermined rate (not known to
the IPA) based on the mass feed rate of the waste. Grab samples
were obtained from the front, middle, and rear of an open,
plastic lined 20 cubic foot container on the back of the truck
which received the stabilized mix. The volumetric increase due
to treatment was estimated at between 30 and 40 percent.
TSD Results
The TCLP results are summarized in Table 3. The total
arsenic concentration of the F035 before stabilization was about
3 percent. The TCLP of this material was 39 mg/L. After
stabilization, the TCLP value was 0.12 mg/L versus the naximum
permitted concentration of 5.0 ng/L, The total chromium
concentration was over 1 percent in the F035, with a TCLP of 9.2;
after stabilization, the TCLP was o.75mg/L. The leachability of
copper, lead and antimony were also lowered by stabilization,(2)
Waterways Experiment Station Procedures
Several buckets of the untreated F035 were transported to
the Waterways Experiment Station (WES), U.S. Army Corps of
Engineers, Vicksburg, MS for immobilization tests with three
binder systems: cement, kiln dust, and lime/fly ash. Preparation
of the test specimens included an initial screening to determine
the appropriate water/binder/waste ratios for evaluation.
Determination of the optimal ratio was based on the results of
the Cone Index Test performed on the initial screening samples
after they had cured for 48 hours. The screening tests involved
mixing binder, water, and waste in a Hobart K4555 mixer at three
water-to-waste weight ratios: 0.0, 0.05, and 0.10. A total of
three binder/waste ratios for the cement and kiln dust binders
and four binder/waste ratios for the lime/fly ash binder were
evaluated. Final binder/waste ratios were 0.10, 0.15, and 0.20
for cement, 0,1, 0.2, and 0.3 for kiln dust, and 0.1/0.1,
0.1/0.2, 0.2/0.1, and 0.2/0.2 for line/fly ash. No additional
water was required.
WES Results
The TCLP results for arsenic and chromium are shown in
Table 4. All samples were cured for 28 days. These data show
that treatment with cement, kiln dust, or lime/fly ash did not
effectively immobilize the arsenic or chromium to the 5.0 mg/L
target values.(3)
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93-RP-131B.05
RECOVER*
The extraction of the copper, chromium, and arsenic frora the
F035 residue or "soil" may be preferable to direct immobilization
and land disposal if the metals can be recovered for reuse. The
amount of material requiring land disposal would also be
diminished. A total of 30 bench-scale extraction tests were
conducted at EPA's Test and Evaluation Facility (T&E) in
Cincinnati, Ohio, with the untreated F035 from the TSD. The TSE
treatability tests use 1M solutions of sulfuric acid,
hydrochloric acid, sodium hydroxide, and ammonium hydroxide. The
metals data fron the inhouse leaching study are shown in Table S.
The results indicate that the arsenic in the extracted residues
(unstabilized) from these tests would not pass the TCLP test.
Only the 3 hour extraction with heated sulfuric acid gave a
residue that passed the TCLP test,
Lewis Environmental Services Inc., conducted separate bench-
scale extraction tests with F035 from an undisclosed source under
a Small Business Pollution Prevention Grant funded by EPA. . This
process used strong sulfuric acid in a counter current leaching
step to recover the metals for reuse in the wood preserving
process, A water wash was treated separately with activated
carbon for additional metals recovery. The treated "soil" passed
the TCLP for arsenic (Table 6). Pilot-scale tests of the system
are scheduled at one of the CCA supplier's facility. (1)
CONCLUSIONS
The arsenic and chromium TCLP results were more favorable
from the TSD cement and ferrous sulfate immobilization process
than any of the three binder systems tested at the Waterways
Experiment Station. The mechanism for this decreased mobility or
the long term stability of the material is not known. Although
it appears technically feasible to recover the metal values from
F035 residues, there is presently little interest from metal
recycling facilities to accept wastes with large amounts of
arsenic. The CCA wood preserving chemical suppliers and wood
preservers are encouraged to continue their efforts towards
reuse. Arsenic fixation processes may be applicable (e.g.
Cashman Process, developed to treat arsenic-containg base metal
sulfide concentrates by hydrometallurgical processes), but
additional studies may be required. The recycle of waste CCA
treated wood into useful, environmentally safe products is
another area for future research.
DISCLAIMER
Although the research described in this paper was funded
wholly or in part by the United States Environmental Protection
Agency, it has not been subject to the Agency's review and
therefore does not necessarily reflect the views of the Agency,
and no official endorsement should be inferred. This paper is
not intended to determine whether immobilization treatment of
F035 is a viable alternative.
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93-RP-131B.05
REFERENCES
(l) Workshop on Removal, Treataent, and Disposal, Arsenic and
Mercury, EPA/600/R-92/105, August 17-20, 1992 Alexandria, VA.
(2) Waste Characterization and Treatability Report for inorganic
Wood Preserving Waste: F035, September 30, 1992 (Internal EPA
Report)
(3) F035 Stabilization/Solidification Study, Waterways
Experiment Station, November 2, 1992 (Internal EPA report)
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TABLE 1
DISTRIBUTION OF PRESERVATIVE USE FOR 1989
Plants Treating With Ho. of Plants
CREOSOTE 43
CREOSOTE/PENTAGHLOROPHENOL 9
CREOSOTE/INORGANICS 21
PEKTACHLOROPHEHOL/INORGAN1CS 15
PEHTACHLOROPHEHOL 19
INORGANICS 420
CREOSOTE/PEMTACHLOROPHENOL/INORGANICS 17
TOTAL 5441
1 Pressure Treaters Only. Non Pressure Plants (9) Not Included
Source: Hicklewight (1990)
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TABLE 2. METALS DATA FROM F035 SAMPLING AT THREE
CCA WOOD TREATING FACILITIES*
AKALYTE
ANTIHOHY
ARSENIC
BARIUM
BERYLLIUM
CADHIUH
CHROMIUM
COPPER
LEAD
MERCURY
NICKEL
SELENIUM
SILVER
THALLIUM
ZINC
AQUEOUS
PROCESS
RECYCLE STREAM
(mg/L)
12-70
3,000-4,000
0.2-3
<0.05
2-7
3,000-6,000
1,800-2,100
0.2-2.4
0.03-0.3
0.1-0.7
2.5
0-0.25
0-1.7
3-19
TREATMENT RE-
TORT SUMP
(mg/L)
0.1-3
10-SOO
0.02-0.6
<0.05
0.01-0.9
10-900
3-280
0.01-0.05
0-0.003
0.01-0.2
0-0.5
0-0.05
0-1.7
0.1-3.5
FREE DRIPPAGE
(mg/L)
5-45
700-2,400
0.7-2
<0.05
0.5-1.5
800-2,300
300-900
0.1-0.2
0.005-0.06
0.1-0.3
0-0.5
0-0.05
0-1.7
4-7
SOLIDS
SCREENED SOLIDS
(rag/kg dry
weight)
50-1,500
8,000-150,000
40-450
0.2-1
0-200
5,000-90,000
3,000-104,000
80-190
1-3
0-250
0-65
2.6-6.5
100-250
140-650
RESIDUAL SOLIDS
TCLP EXTRACT
(mg/L)
0.1-1
2-250
0.07-0.25
<0.005
0-0.08
0-14
19-205
<0.002
<0.0002
0.03-0.6
<0.25
<0.025
<0.85
0.07-2.4
The three facilities visited were 30+, 10+, and
process recycle streams, the treatment cylinder
the residual sol Ids from the filter screens.
<2 years old. One grab sample fro« each of the aqueous q
sumps, and the post-treatment free drlppage; grab samples of i.
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TABLE 3. METALS DATA FROM F035 STABILIZATION/SOLIDIFICATION TREATABILITY STUDY
CONDUCTED AT A TREATMENT, STORAGE, AND DISPOSAL (TSD) FACILITY!
ANALYTE
AKT1MONY
ARSENIC
BARIUM
BERYLLIUM
CADHIUK
CHROMIUM
COPPER
LEAD
HERCURY
NICKEL
SELENIUM
SILVER
THALLIUH
ZINC
SOLIDS
BEFORE TREATHENT
(rag/kg or pptn)
540
30,500
93
<1.0
<1.0
12,500
8,300
73
10.8
25
<1.0
<2.0
NA
44
AQUEOUS (TCLP EXTRACT OR SOLID)
BEFORE TREATMENT
(mg/L or ppm)
1.0
39
<2,0
<0.05
<0.05
9.2
10.4
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TABLE 4. METALS DATA FROM F035 STABILIZATION/SOLIDIFICATION
TREATABIUTY STUDY AT WATERWAYS EXPERIMENT STATION*
ANALYTE '
ARSENIC
CHROMIUH
BEFORE TREATMENT
(ppm)
77,000
20,000
AFTER TREATHENT TCLP
CEMENT
(mg/1)
9
16
KILN DUST
(mg/L)
32
20
LIME/FLY ASH
Cmg/U
28
IS
* One sample fro» etch type of binder for TCLP, performed In triplicate.
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TABLE 5.
TCLP METALS DATA BASED ON F035 BENCH-SCALE LEACHING EXPERIMENTS CONDUCTED AT
U.S. ERA'S TEST AND EVALUATION (T&E) FACILITY
[AQUEOUS
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TABLE 6
TCLP TEST RESULTS OF LEWIS ENVIRONMENTAL
ACID LEACHED SOIL*
REGULATORY
LEVELS
ARSENIC 0.71 MG/L S.O MG/L
CHROMIUM 0.22 HG/L 5.0 MG/L
* NUMBER OF SAMPLES NOT PROVIDED BY VENDOR
a
b
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4. TITLE AND SUBTITLE
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before comple
1. REPORT NO.
EPA/600/A-93/160
5. REPORT DATE
Management of Arsenical Wood Preserving Residuals
by Recovery and Immobilization
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Ronald J. Turner, U.S. EPA, RREL, Cincinnati, OH
Mary Beth Foerst, IT Corporation, Cincinnati, OH
8. PERFORMING ORGANIZATION REPORT NO.
|. PERFORMING ORGANIZATION NAME AND ADDRESS
1-U.S. Environmental Protection Agency
Cincinnati, OH 45268
2-IT Corporation
Cincinnati, OH 45268
10. PROGRAM ELEMENT NO.
1 1. CONTRACT/GRANT NO.
68-C9-0036
12. SPONSORING AGENCY NAME AND ADDRESS
Risk Reduction Engineering Laboratory—Cincinnati, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 4526S
13. TYPE OF REPORT AND PERIOD COVERED
Published Paper
14. SPONSORING AGENCY CODE
EPA/600/14
IS. SUPPLEMENTARY NOTES
Project Officer = Ronald Turner (513) 569-7775; Air & Waste
Management Association, Denver, Colorado,.86th Annual Meeting, 6/13-18/93 , p:i-i2
16. ABSTRACT
Chromated copper arsenate (CCA) is the predominant wood preservative used
in the U.S. (67% by volume of wood treated). The residuals from pressure
treatment of lumber consist of washdown waters, drippage, treating cylinder
sediment, spent formulations and filter screenings. Analyses of these materials
indicate arsenic, copper, and chromium concentrations of 1-3 percent each. The
solid residues are currently land disposed in RCRA permitted facilities after
stabilization and meeting a leachate standard of 5.0 mg/L for arsenic and
chromium characterisitc wastes. Bench-scale research studies were conducted by
the EPA and the private sector to investigate the extractability of the arsenic
and metals for reuse by the wood preserving facilities and to determine whether
the solid residues are rendered nonhazardous by extraction. Stabilization
techniques were also evaluated for immobilization of the arsenic and other
metals. The feasibility for recovery of CCA from treatment residues has been
demonstrated. Conventional stabilization did not effectively immobilize the
arsenic or chromium.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Wood Preserving
Arsenic Stabilization
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (Tllil Keport/
Unclassified
21. NO. OF PAGES
13
20. SECURITY CLASS
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