United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-91/049 Mar. 1992
EPA Project Summary
A Comparative Evaluation of
Two Extraction Procedures: The
TCLP and the EP
R. Mark Bricka, Teresa T. Holmes, and M. John Cullinane, Jr.
The 1984 amendments to the Resource
Conservation and Recovery Act (RCRA)
require that the U.S. Environmental Pro-
tection Agency (EPA) restrict the land
disposal of hazardous wastes. The Ex-
traction Procedure Toxiclty Characteris-
tic (EP) test is used to determine if an
improperly managed waste poses an
unacceptable risk to groundwater and
should therefore be managed as a haz-
ardous waste. Regulatory thresholds,
based on the EP test, have been estab-
lished for eight metals, four pesticides,
and two herbicides.
The Toxicity Characteristic Leaching
Procedure (TCLP) is a newer regulatory
test developed to address a Congres-
sional mandate to identify additional
characteristics of wastes, primarily or-
ganic constituents, that may pose a threat
to the environment. The TCLP has been
promulgated for use in determining spe-
cific treatment standards associated with
the land disposal restrictions of RCRA.
The TCLP has also been proposed as a
replacement procedure for the EP test.
Two studies were conducted to com-
pare the results of the TCLP with those of
the EP. In the first study, a synthetic
heavy metal waste was chemically so-
lidified/stabilized with and without a va-
riety of interfering compounds. The so-
lidified/stabilized waste was cured for
28 days and subjected to the TCLP and
EP extractions. The extracts were ana-
lyzed for Cd, Cr, Ni, and Hg. In the second
study, two solidified/stabilized, heavy
metal wastes and an untreated
perchloroethene (PCE) still-bottom
waste were used. Twelve volatile organic
compounds were added to each waste
type at two ratios. The EP and TCLP were
performed on three samples from each
waste type. The extract from each sample
was analyzed for As, Ag, Ba, Cd, Cu, Ni,
Pb, and Zn and for the 12 volatile organic
compounds. The losses due to the me-
chanics of the TCLP and EP extractions
were also estimated by spiking the TCLP
and EP extracts with known concentra-
tions of organic compounds before and
after extracting the wastes.
The results of these studies indicate
that, for most of the metal contaminants,
the TCLP and EP produce similar results
when TCLP extraction fluid 2 (acetic acid
solution) is used but differ when TCLP
extraction fluid 1 (acetate buffer) is used.
The results of testing for volatile organic
contaminants indicate that, for 8 of the
12 contaminants, the concentrations
measured in the TCLP extractants were
significantly greater than those mea-
sured in the EP extractants.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
One of the most significant dangers posed
by hazardous waste stems from the leach-
ing of toxic constituents into groundwater.
The EPA EP test addresses the properties
of a waste that are directly related to the
potential of the waste to pose a hazard to
groundwater when disposed of in a landfill
environment. The toxicity characteristic is
assessed when the waste is subjected to
the EP, and the extract is analyzed for
UT) Printed on Recycled Paper
-------
eight metals, four pesticides, and two herbi-
cides.
The TCLP is a "second-generation" ex-
traction procedure developed by the EPA.
The TCLP is proposed as a replacement for
the EP test as a waste characterization
pool. This procedure has also been pro-
posed as a method of addressing the short-
comings of the EP. Since the TCLP was first
published in the Federal Registers 1986, it
has undergone several modifications. This
study was conducted using the June 13,
1986, publication of the TCLP. More re-
cently, the November 7, 1986, version of
the TCLP method has been published in the
Code of Federal Regulations, Part 267,
Appendix I.
There are many differences between the
EP and TCLP methods, some of which are
obvious; others are buried within the proce-
dures. The most obvious difference is that
the TCLP requires the use of the zero-
headspace extraction (ZHE) vessel for vola-
tile compounds and an extraction fluid se-
lection step for nonvolatile extractions. Other
differences include:
• In the TCLP method for nonvolatiles,
one of two extraction fluids is selected
to extract the solid waste sample. The
type of extraction fluid is determined in
an initial test on the waste and is based
onthe waste's alkalinity. Extraction flu id
1 is an acetate buffer at a pH of
4.93 ±0.05. Extraction fluid 2 is an
acetic acid solution with a pH of 2.88
± 0.05. The EP uses distilled deionized
water as an extraction fluid, and 0.5 N
acetic acid is added to the solid waste/
water slurry to maintain the pH at 5.0
± 0.2. The acetic acid is added as re-
quired, up to a maximum of 4 g of 0.5 N
acetic acid per 1 g of solid waste.
• The TCLP method for volatiles requires
the use of extraction fluid 1. The EP has
no volatiles extraction procedure.
• The TCLP requires that the ZHE vessel
be used for volatiles extraction.
• The TCLP procedure requires the use
of 0.6- to 0.8-^im glass fiber filter and
excludes the use of prefilters. The EP
requires the use of 0.45-u.m cellulose
triacetate filters and allows the use of
glass fiber prefilters.
• The TCLP requires that the particle size
of the solid be small enough to pass a
9.5-mm standard sieve. The EEP allows
the use of the Structural Integrity Pro-
cedure if the sample is monolithic in
nature. If the sample is not a monolith,
the EP requires that the particle size be
small enough to pass a 9.5-mm stan-
dard sieve.
• The TCLP requires rotary agitations in
an end-over-end fashion at 30 ±2 rpm.
The EP allowsthe use of either a stirred
open vessel or a rotary end-over-end
agitator.
• The extraction period for the TCLP is
18 hr. The extraction period for the EP
is 24 ± 2 hr.
• The EP requires monitoring and adjust-
ment of the pH during the extraction.
The TCLP does not.
This study was designed to compare the
extraction efficiencies of the TCLP with those
of the EP. This comparison was accom-
plished in two ways. In the first, the metal-
extraction effectiveness of the two extrac-
tion methods was evaluated on a synthetic
metal sludge, with and without different
interfering materials. The second involved
evaluating the efficiency of the extraction of
selected volatile compounds from three so-
lidified/stabilized wastes and evaluating the
loss of the volatiles during both the process
of conducting the extractions and the stor-
age of the extracts before their analyses.
Procedures
In the first study (A), a synthetic metal
sludge containing cadmium (Cd), chromium
(Cr), nickel (Ni), and mercury (Hg) was
treated with a lime/kiln dust binding agent.
During the mixing process, three concen-
trations of 10 materials that might interfere
with the binding and contaminant contain-
ment properties were added to the sludge.
A different batch of waste/binder was mixed
for each of the interfering materials. After
the materials had cured under constant
temperature and 100% humidity for at least
28 days, samples were ground and sub-
jected to the EP and TCLP tests.
In the second study (B), two of the wastes,
the metal plating sludge and metal plating
solution, were first solidified using Type 1
Portland cement as binding agent. Sepa-
rate batches of the two solidified wastes and
perchloroethene (K030) still-bottom waste
were divided into two portions, and a solu-
tion of 12 volatile organics was added at
either 0.1 or 1.0 weight percent. The vola-
tile organics included chloroform, carbon
tetrachloride, benzene, toluene, ethylben-
zene, two ketones, and five di-, tri-, and
tetra-chloromethane and chloroethene com-
pounds. The wastes were cured for 14 days,
and samples were subjected to the EP and
TCLP tests. The EP and TCLP extracts
were analyzed for metals and volatile or-
ganic compounds.
A separate part of this study was de-
signed to detect any losses of volatile or-
ganics that might occur during the EP and
TCLP procedures or during subsequent ex-
tract handling and storage. The leachate
solutions were spiked during two separate
steps of the EP and TCLP, either before
extraction or after the liquid/solid separation
step.
Both studies were intended as multrf actor
factorial experimental designs to facilitate
statistical analysis. Complete internal and
external laboratory quality assurance/qual-
ity control measures were used throughout.
Results and Discussion
Study A - Leaching of the
Solidified Metal Sludge
The concentrations of the metals in the
solidified sludges that were released in the
EP and TCLP extractions in Study A are
summarized in Figures 1 through 4. The
results were normalized to the total amount
of metal extracted to correct for the differ-
ence in amount of extractant used in the two
tests.
As illustrated in Figure 1, for 34 of the
40 conditions under which the TCLP and
EP were compared, the EP extracts con-
tained higher concentrations of cadmium.
These results, however, are not statistically
significant, perhaps because of the high
variability in the data. Nickel concentrations
(Figure 2) are similar for both extraction
procedures (18 having lower TCLP and
22 lower EP concentrations). Chromium
(Figure 3) and mercury (Figure 4) concen-
trations were higher in the TCLP extracts
(25 of 40 chromium and 28 of 40 mercury
having higher TCLP extract levels).
All extractions of the metal sludges used
extraction fluid 2 for the TCLP and the full
amount of acid for the EP so that the buffer-
ing capacity of the EP and TCLP extraction
fluids was equal. The small but significant
differences seen in the amounts of chro-
mium and mercury extracted by the TCLP
procedure cannot be attributed solely to pH
influences but must be a function of other
differences between the extraction proce-
dures such as time of extraction or method
of agitation.
Study B - Organic Extraction
from Metal Wastes and Still
Bottoms
Metals in Extracts
The two solidified/stabilized metal wastes
produced TCLP and EP extracts that were
not significantly different for the majority of
cases studied (Figure 5). Arsenic and lead
were the only contaminants for which
-------
o
Interference Compound
Figure 1. Average normalized Study A cadmium extract concentrations expressed as the TCLP
concentration divided by the EP concentration.
the TCLP extracts were significantly more
concentrated than were those of the EP.
Again, for these solidified wastes, extrac-
tion fluid 2 was used, which is identical in
alkaline neutralization capacity to the EP
extraction fluid when all 400 ml of 1 he acetic
acid is required.
Organics in Extracts
With some exceptions, TCLP extracts
typically contained about one and a half
times as much of each of the organics as did
the EP extracts (illustrated for the 1 % spiked
sample in Figure 6). Extracts from the 1%
spiked samples averaged only about 50%
higher organic levels than did those of the
0.1% spiked samples. No correlation was
found with any of the physical properties of
the organic materials, such as vapor pres-
sure, solubility, pH, or boiling point.
Volatile Losses
The wastes were spiked in different steps
of the TCLP and EP procedures to give an
indication of the amount of loss of the organ-
ics during the test. When chlorobenzene
and carbon disulfide were added to the
extraction fluid before leaching, over 99% of
both were lost. The organics were either
absorbed by the waste solids or were lost
from the extracting fluids during the proce-
dure.
Spiking the extraction fluid after the leach-
ing procedure resulted in 5% to 20% loss of
chlorobenzene and about 10% to 25% loss
of carbon disulfide. Evidently, a maximum
of about 25% of the volatile organic spike
was lost during sample placement in the
sample vial, storage, and analysis. The high
recoveries indicate that the materials were
probably well dispersed so that the loss of
carbon disulfide and chlorobenzene from
the samples spiked before leaching cannot
be attributed to poor sample dispersion.
Conclusions and Observations
This study was conducted to compare the
results of the TCLP and the EP. The EP and
TCLP extractions were performed on a num-
ber of different wastes subjected to a variety
of conditions. Based on the results of this
study, the following conclusions were drawn
and observations made.
(1) Generally, the TCLP was a more ag-
gressive leaching procedure than was
the EP.
• When TCLP extraction fluid 2 was
used to extract metal contaminants,
the EP and TCLP produced similar
results.
• When TCLP extraction fluid 1 was
used to extract metal contaminants,
the EP and TCLP produced statisti-
cally different results, with theTCLP
generally being the more aggres-
sive extraction.
• The TCLP ZHE was only a slightly
more aggressive extraction for vola-
tile organics than was the EP extrac-
tion in this study.
(2) Although the TCLP ZHE was a more
aggressive extraction procedure than
was the EP for the volatile organics,
the difference in the concentrations of
volatile organics in the TCLP and EP
extracts was less than expected.
(3) When the ZHE vessel was used, cross
contamination presented a potential
problem.
(4) The TCLP and EP extraction of the
solidified/stabilized specimens ap-
peared to produce conditions that per-
mit dechlorination reactions to occur.
Significant amounts of 1,1-dichloro-
ethene were detected in the TCLP and
EP extracts although no 1,1-
dichloroethene was added, and none
was detected in the raw wastes.
-------
20
15
10
1
o
I
Interference
Concentration
D 0%
B2%
S5%
8%
I
o
I
5
1
I
I
CO
«
§
£
Interference Compound
Figure 2. Average normalized Study A nickel concentrations expressed as the TCLP concentration
divided by the EP concentration.
Recommendations
The TCLP method, although more diffi-
cult to perform than the EP method, is an
extraction test that can be performed in
most laboratories. The TCLP method, un-
like the EP method, addresses semivolatile
and volatile contaminants. Several areas
should be clarified in the TCLP extraction
method. The following recommendations
are based on the results of this study.
(1) The ZHE vessel is difficult to clean.
The TCLP method needs to make rec-
ommendations on the most effective
method of cleaning the ZHE vessel.
Modification of the value design is
highly recommendedtoimproveclean-
ing techniques.
(2) The TCLP method is vague about pro-
cedures for sample collection from the
ZHE vessel when Tedlar bags are not
used. A section describing the collec-
tion of a sample using volatile vials
should be included in the TCLP
method.
(3) Additional research should be initiated
to investigate why volatile chlorinated
compounds extracted from solidified/
stabilized wastes are converted to other
chlorinated forms.
The full report was submitted in fulfillment
of Interagency Agreement No. DW930146-
01 by the U.S. Army Engineer Waterways
Experiment Station under the sponsorship
of the U.S. Environmental Protection
Agency.
-------
40 -
30 -
20 -
CO
| 10 -
3
2* n
o.
li 3.5
Q
CO
$.3.0
'&
3
5 2.5 •
2.0
1.5
1.0
0.5
Q
r
I
" if'
,
'.
!
:
:
\\
I
\
:
:
\
•
• n
; \ \
":
j
-
':
•
*
\
\
\
:
: a
: j
: ',
»
1 !
\
L
a
a
\
\
•
;
:
•
j
\
\
I
| |
1- c?
a
:
;
\
»
•u
te
I
Hydroxide
c
Interference
Concentration
D0%
%8%
~f
;
n r
L :
: : .
: : ;
: :
J\\
:;
* -0 « q>
S S C i
-j 8 €
C3 1
o
-
-
-
_
_
-
-
-
-
L .
\\
\\ ~
\\
si
Interference Compound
Figures. Average normalized Study A chromium extraction concentrations expressed as
the TCLP concentration divided by the EP concentration.
-------
Interference Compound
Figure 4. Average normalized Study A mercury extract concentrations expressed as the TCLP concentration
divided by the EP concentration.
-------
ouv
400
300
-9 S
I i J
g
wrr.
Interference Compound
Figure 5. Average normalized Study B metal extract concentrations expressed as the TCLP
concentration divided by the EP concentration.
4
I3
i
Sludge Type
& PCE
B WES
B WTC
II
il
= 1
a
1
I
I
Q)
I
I
C\l
cvf
0)
I
I
t
Ul
Interference Compound
Figure 6. A verage normalized Study B1.0 percent organic extract concentrations expressed as the
TCLP concentration divided by the EP concentration.
7
•A-U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-OKO/40181
-------
R. MarkBricka, Teresa T. Holmes, andM. John Cullinane, Jr., are with the U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MS 39180-6199.
Car/ton C. Wiles is the EPA Project Officer (see below).
The complete report, entitled "A Comparative Evaluation of Two Extraction Procedures:
the TCLP and the EP " (Order No. PB91-240 564/AS; Cost: $26.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-91/049
------- |