United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA/600/S2-89/011 Sept. 1989
Project Summary
Treatability Potential for EPA
Listed Hazardous Wastes in Soil
Raymond C. Loehr
This study developed comprehen-
sive screening data on the treatability
in soil of: (a) specific listed haz-
ardous organic chemicals, and (b)
waste sludge from explosives pro-
duction (KO44) and related chem-
icals. Laboratory experiments were
conducted using two soil types, an
acidic soil (Mississippi soil) with less
than one percent organic matter, and
a slightly basic sandy loam soil
(Texas soil) containing 3.25% organic
matter. These experiments evaluated
the: (a) relative toxicity of the chem-
icals and waste, (b) degradation of
the chemicals and waste in the soils,
(c) adsorption characteristics of the
chemicals in the two soils, and (d)
toxicity reduction that occurred dur-
ing degradation.
The major conclusions were:
1. The chemical structure of the
compounds evaluated affected
their relative toxicity. With chlo-
rophenols, the relative toxicity
was related to the position of the
chlorine group on the phenol ring.
The order of relative toxicity was
para >meta >ortho. The same
order appeared to occur for
methylphenols and nitrophenols.
The chemical substituted on the
phenol ring appeared to have an
effect on toxicity. Nitro-substi-
tuted phenols appeared to be less
toxic than the methyl- or chloro-
substituted phenols. Mixing of the
chemicals with the soils did not
affect the relative toxicity of the
chemicals in the two soils.
2. Data characterizing the chemical
loss in the soil and in the water
soluble fraction (WSF) extracted
from the soil as well as the
toxicity reduction In the WSF
could be represented satisfac-
torily by either first or zero order
kinetics. In most cases, the data
were represented by either kinetic
parameter with high correlation
coefficients.
3. The rates of chemical loss were
higher in the Texas soil. Chloro-
phenols with chlorine substituted
in the meta position had greater
half-lives and lower loss rates.
Chemicals with a nitro group
substituted in the phenol ring ap-
peared to have a lower loss rate.
4. The Freundlich equation de-
scribed the adsorption of most of
the chemicals with the two soils
satisfactorily. The values of the
Freundlich constant (Kf) for the
chemicals in the two soils were
different For the acid extracta-
bles, the K, values generally were
greater in the Mississippi soil. For
the amines and alcohols, the K,
values were greater in the Texas
soil.
5. The loss of the applied chemical
in the soil and in the WSF as well
as the reduction of the WSF
toxicity were compared for nine of
the chemicals. The chemical loss
in the WSF was about 1.5 times
faster than the chemical loss in
the soil. The WSF toxicity de-
creased at about the same rate as
the WSF chemical concentration.
No enhanced mobilization of the
applied chemical occurred during
degradation.
This Project Summary was devel-
oped by EPA's Robert S. Kerr Environ-
mental Research Laboratory, Ada, OK,
to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report order-
ing information at back).
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Introduction
This study was conducted to provide
comprehensive screening data on the
treatability in soil of: (a) EPA listed
hazardous organic chemicals, and (b) a
specific hazardous waste and related
chemicals. The results provide data that
can be used when permitting decisions
are made related to: (a) management of
spills, (b) remediation of contaminated
soils, and (c) the use of land as a waste
management alternative. The degradation
and partitioning data can be used as
input to predictive models that estimate
the movement of chemicals in the un-
saturated zone of the soil. The models in-
tegrate the processes that affect chem-
icals in soil (degradation and partitioning)
so that an assessment can be made of
the extent to which protection of human
health and the environment occurs. The
understanding that results from the use of
such models allows the identification of
chemicals and wastes that require control
to reduce or eliminate their hazard
potential prior to application to soil. Lab-
oratory studies were conducted to de-
termine: (a) degradation kinetics, (b)
sorption, (c) toxicity of the chemicals and
waste, and (d) the reduction in toxicity
that occurred during degradation.
Designated Chemicals and
Wastes
The chemicals and specific waste that
were part of this study are identified
hazardous wastes. These chemicals can
be expected to be components of many
industrial compounds and wastes that
enter the soil from spills and inadequately
sealed impoundments (pits, ponds and
lagoons) and as part of wastes applied to
operating land treatment units. The
chemicals that were evaluated are iden-
tified in Table 1. The specific hazardous
waste, and chemicals related to that
waste, that were evaluated are noted in
Table 2.
Samples of the explosives waste
sludge (K044) and the chemicals TNT,
RDX, and HMX were obtained with the
help of the U.S. Army Toxic and Haz-
ardous Materials Agency (USATHAMA).
A sample of wastewater treatment sludge
resulting from the manufacture and
processing of explosives was obtained
from the Holston Army Ammunition Plant
with the assistance of USATHAMA. This
material was stored at 4°C until required
for analysis and use.
Soils
The intent of this study was to provide
comprehensive screening data on the
treatability of specific chemicals and a
hazardous waste in soil. The charac-
teristics of the soil will affect the
degradation, sorption, and treatment po-
tential and two soils with different charac-
teristics were used. One was an acid soil
with a low organic content and the other
was a basic soil with a higher organic
content and cation exchange capacity
(CEC). The acid soil, obtained from an
area near Wiggins, Mississippi, was sup-
plied by researchers at Mississippi State
University and was referred to as Mis-
sissippi soil. The basic soil was obtained
from an area near Austin, Texas, that, to
the knowledge of the personnel of this
project, had not been exposed to in-
dustrial chemicals or wastes. This soil
was referred to as Texas soil.
Relative Toxicity and Chemical
Loading
The relative toxicity tests that were
conducted were not intended to provide
information on toxicity from a human
health or safety or from an environmental
standpoint. Rather, these tests were used
as a relative toxicity screening method.
Such tests also can be used to identify
the relative toxicity reduction that occurs
when chemicals and waste are managed
by the land treatment process.
Although no single bioassay procedure
can provide a comprehensive toxicity
evaluation of a chemical, a valid toxicity
screening test can provide information
about the relative toxicity of a compound
and can help predict non-inhibitory
chemical application rates. The Microtox*
system is a relatively simple, rapid and
inexpensive test and was used as the
toxicity screening method in this project
to determine: (a) the relative toxicity of
the chemicals and wastes, (b) the non-
inhibitory chemical and waste loadings
used in the degradation studies, and (c)
the toxicity reduction that occurred in the
respective studies. The use of the
Microtox® procedure to screen and
predict the treatability potential of waste
in soil has been evaluated and found to
be satisfactory.
Degradation Studies
These experiments were conducted to
determine the removal kinetics of the
designated chemicals and wastes in soil.
Several of the chemicals could no
evaluated because of chemical reac
in the soils that made analytical detei
impossible. These were Diphenylan
m-Phenylenediamine and Thiophenol
Biodegradation is believed to be
most important removal mechanism
organic compounds in soil systems.
degradation of organics is accompli:
in a series of biochemical reacti
through which a parent compouni
changed or transformed to organic
inorganic end products. Complete de
dation is the term used to describe
process whereby constituents are mi
alized to inorganic end products, inc
ing carbon dioxide, water, and inorg
nitrogen, phosphorus, and sulfur c
pounds. Aerobic soil bacteria possess
ability to biochemically catalyze
oxidation of organic compounds. For
reason, and because the zone of in
poration at land treatment sites genei
is aerobic, the protocol used in this st
allowed aerobic conditions and aerc
biodegradation reactions to occur.
The primary goal of biodegrada
testing is to obtain an overall estimati
the rate at which a compound will I
degrade in a soil environment. While
compounds appear in the environmen
pure form, a common approach
studying removal rates of organic c<
pounds has been to evaluate indivic
compounds. Although this approach f
vides an understanding of the rerm
rates for specific compounds, it is rec
nized that during actual land treatm
chemicals normally are applied as n
lures. Interactions between compounds
a mixture within the soil matrix may p
mote or inhibit their removal from s
The noted chemicals (Tables 1 and
were evaluated as individual compoui
using standard laboratory microcos
and protocol.
In this study, no distinction was mi
between specific loss mechanisms. I
moval rates can be due to biodegrai
tion, chemical degradation, hydroly;
photolysis and volatilization. The che
icals that were evaluated did not have
high volatilization potential and volatili
tion was not considered an important
moval mechanism in these degradat
experiments.
The rate of degradation was expe
mentally determined by measuring I
difference between the amount of co
pound initially added to a soil and tl
which was recovered after specified tii
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Table 1. Chemicals
Compound
Acid Extractables
Phenol
o-Cresol
p-Cresol
m-Cresol
2-Chlorophenol
3-Chlorophenol
4-Chlorophenol
2,3-Dichlorophenol
2, 4 -Dichlorophenol
2,5-Dichlorophenol
2, 6-Dichlorophenol
3,4-Dichlorophenol
2,4,5-Trichlorophenol
2,4, 6-Trichlorophenol
Pentachlorophenol
2, 4 -Dimethyl phenol
2-Methyt-4-Chlorophenol
3-Methyl-4-Chlorophenol
3-MeV>yl-6-Chlorophenol
p-Nitrophenol
2,4-Dinitrophenol
4, 6-Dinitro-o-Cresol
Thiophenol
Amines
Diphenylamine
m -Phenylenediamine
Toluenediamine
Brucine
Alcohols
Isobutyl alcohol
Allyl alcohol
Propargyl alcohol
1-Butanol
2, 3-Dichloropropanol
Methanol
Other
Carbon disutfide
2-Nitropropane
Thiourea
that were Evaluated in this Study
Formula
C6H60
C7HgO
C7H80
C7H80
CgH5CIO
CeH5CIO
CgH5CIO
CeH4CI20
CeH4C/20
C6H4C/20
CeH4CI20
CeH4CI20
C6H3CI30
CeHyClsO
CgHClsO
CgH100
C-fH^IO
C7H7CIO
C7H7C/0
CeHgNOj
CeH^Os
CTH^OS
CeHgS
C12H,,N
CeHeA/2
C7/VWH2>2
^23^26^204
C4H,00
CaHgO
C3H40
C4H,00
C3H6C/2
CH4O
CS2
0^7^02
CH4W2S
EPA Hazardous Waste
Number
U188
U052
U052
U052
U048
NOS
NOS
NOS
U081
NOS
U082
NOS
U230
U231
U242
U101
NOS
U039
NOS
U170
P048
P048
U014
X016
X017
U221
P018
U140
POOS
P102
U031
X006
U154
P022
U171
U219
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Table 2.
The Hazardous Waste and Related Chemicals that were Evaluated
Specific Hazardous Waste
K044 - Wastewater treatment sludge from the manufacturing and processing of explosives
Explosive and Munitions Manufacturing Chemicals
Compound Formula
EPA Hazardous
Waste Number
2,4-Dinitrotoluene
2,6-Dinitrotoluene
TNT (2,4,6-Trinitrotoluene)
RDX +
HMX+ +
C7H6A/204
C7H6N204
C7H5N306
C3H6A/606
C^gNgOg
U105
U106
-
-
-
RDX = Hexahydrotrinitrotriazine
+ HMX = Cyclotetramethylenetetramtramine
intervals. A plot of the disappearance of a
constituent originally present in the
chemical/soil mixture versus treatment
time provided the following: (a) the type
of reaction (generally zero or first order),
(b) the reaction rate constants for the
zero or first order reactions, and (c) the
half-life (t1/2) time of each constituent of
concern. The soil used: (a) had not had
previous exposure to industrial chemicals
or wastes, and (b) did not receive any
pretreatment such as soil amendments or
specially acclimated biological cultures
prior to these experiments. The naturally
occurring soil microbial consortium was
responsible for the bioremediated re-
moval of the chemicals.
Chemical mass loadings were deter-
mined as part of the toxicity screening
evaluations and ensured that the loadings
at which the chemicals were applied did
not inhibit soil microbial activity. Soil pH
was not adjusted nor were supplementary
organic substrates used.
Adsorption Experiments
The persistence of hazardous organic
compounds in soils is related to reactions
that affect the transport and fate of such
chemicals. One of the most important
reactions is adsorption. Adsorption is the
process by which ions or molecules
present in one phase tend to concentrate
at a surface or interface. The tendency of
organic molecules to adsorb on soil is
determined by the physical and chemical
characteristics of the chemical compound
and the soil to which it is added. The two
driving forces for adsorption are the
lyophobic (solvent-disliking) character of
a solute relative to a particular solvent,
and the affinity of the solute for the solid,
such as electrical attraction.
Adsorption is the major retention
mechanism for most organic and inor-
ganic compounds in soils. As a result, the
leaching potential of a chemical in soil is,
in general, proportional to the magnitude
of the adsorption (partitioning) coefficient
of that chemical in a soil. The adsorption
potential of a chemical is governed by
the properties of both the soil and the
chemical. Important properties of the
chemical that affect adsorption include:
(a) chemical structure, (b) acidity of
basicity of the molecule (pKa or pKb), (c)
water solubility, (d) permanent charge, (e)
polarity, and (f) molecule size.
At equilibrium, the solute remaining in
solution is in dynamic equilibrium with
that of the soil surface. At this point, there
is a defined distribution of solute between
the liquid and solid phases. The preferred
form for depicting this distribution is to
express the quantity qe (amount of solute
sorbed per unit weight of solid sorbent)
as a function of the equilibrium solution
concentration (Ce) at a fixed temperature.
An expression of this type is an
adsorption isotherm.
An adsorption equation that has be
used widely for solid-liquid systems
the Freundlich equation:
Qe = Kf C,""
where qe is the equilibrium distribut
coefficient (mg of chemical/gm of j
sorbent), Ce is the equilibrium chemi
concentration (mg/liter of solvent), and
and 1/n are constants The constant,
is related to the capacity or affinity of I
adsorbent and the exponential term, 1
is an indicator of the intensity, or how I
capacity of the adsorbent varies with 1
equilibrium solute concentration. T
Freundlich isotherm has had success
describing sorption behavior of organ
and the adsorption data generated in tl
study were evaluated by this equation.
Toxicity Reduction
A major objective of this study was
provide comprehensive screening d<
on the treatability of specific orgar
chemicals in soil. Hazardous constituer
that enter the soil are to be detoxified
immobilized. When a chemical is add
to the soil, it is transformed into otr
products through chemical and biologic
reactions with or without complete detc
ification and immobilization. Measuri
the loss of the parent compound does r
assure that complete detoxification a
immobilization occurs. Intermediate d
radation products, which may be
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mobile and/or toxic than the parent
compound, may be generated as the
parent compound degrades. Additional
information on the transformation and/or
detoxification of a chemical is necessary
to establish that the loss of the parent
compound leads to the complete detoxifi-
cation of the chemical or waste. Such
information can be obtained using either
chemical or bioassay analyses.
The reduction of toxicity that occurred
in selected degradation studies was eval-
uated by determining the toxicity of the
water soluble fraction (WSF) of the chem-
ical/soil mixture at the same sampling
intervals used to obtain the degradation
data. The chemical compounds that can
be extracted with water represent the
potentially leachable fraction of the
chemical or any intermediate chemical
detoxification products. The WSF of the
chemical poses the greatest threat to
groundwater contamination. Hence,
evaluating the loss of the potentially
leachable fraction of a chemical is
important. The concentration of the
parent chemical in the WSF also was de-
termined. This concentration was ex-
pressed in terms of quantity of chemical
that was water extractable per kg of the
soil. To put the toxicity reduction data in
perspective, the WSF toxicity reductions,
he WSF chemical concentration reduc-
tions and the soil chemical concentration
reductions were compared.
Conclusions
Specific conclusions based on the
results of the project include:
1. The Microtox0 biological assay rep-
resents an appropriate method with
which to evaluate the EC50 toxicity
of a chemical or waste.
2. Comparison of the EC50 data indi-
cated that: (a) the alcohols were less
toxic than the acid extractable com-
pounds, and (b) within chemical
categories, there were considerable
differences in relative toxicity.
3. The chemical structure of the com-
pounds evaluated affected the rela-
tive toxicity of a compound. With
chlorophenols, the relative toxicity
was related to the substitution posi-
tion of the chlorine group on the
phenol ring. The order of relative
toxicity was para>meta>ortho. The
EC50 data suggested that the same
order occurred for methylphenols
and nitrophenols.
4. The chemical that was substituted
on the phenol ring appeared to have
an effect on toxicity. Nitro-substi-
tuted phenols, even when substi-
tuted in the para position, appeared
to less toxic than the methyl- or
chloro-substituted phenols.
5. When the chemicals were mixed
with two different soils, and the EC50
value of the water soluble fraction
(WSF) of the soil mixtures was
measured, the values also indicated
that chemicals with the chlorine in
the para position had the greater
toxicity. Mixing of the chemicals with
the soils did not affect the relative
toxicity of the chemicals in the two
soils.
6. In general, the acceptable non-
inhibitory chemical loading rates for
the Mississippi soil were lower than
those for the Texas soil. There was
no consistent pattern for the
differences.
7. The chemical or waste loading pro-
cedure (described in Table 9, Sec-
tion 4 of the full report) resulted in
chemical loadings that did not inhibit
the non-acclimated organisms in the
laboratory microcosms, except in
one case (4,6-Dinitro-o-Cresol). This
procedure provided a good estimate
of initial, acceptable chemical
loadings that can be used in lab-
oratory degradation studies.
8. Both zero and first order kinetics
provided adequate representation of
the data. For most of the chemicals,
the data could be fit to either
kinetics with high correlation coef-
ficients.
9. The rates of chemical loss were
higher in the Texas soil than in the
Mississippi soil. There did not ap-
pear to be any pattern to the differ-
ences in rates in the two soils.
10. Chlorophenols with the chlorine sub-
stituted in the meta position had
greater half-lives and therefore lower
chemical loss rates. This was par-
ticularly evident with the mono-, di-,
and trichlorophenols in the Texas
soil.
11. Chemicals that had a nitro group
substituted on the phenol ring ap-
peared to have a lower loss rate.
12. The Freundlich equation described
the adsorption of the chemicals on
the two soils satisfactorily, with high
correlative coefficients, except for a
few chemicals.
13. The range of chemical concentra-
tions evaluated ranged from the low
mg/l concentrations to near or at
saturation concentrations, and for
most chemicals covered two to three
orders of magnitude. For these con-
centration ranges, a linear ad-
sorption relationship, i.e., n = 1, did
not occur.
14. The values of the Freundlich con-
stant (Kf) for the chemicals in the
two soils were different. For the
acid extractables, the Kf values gen-
erally were greater in the Texas soil
which had the higher pH and the
greater organic carbon content. For
the amines and alcohols, the K,
values were greater in the Mis-
sissippi soil, which had the lower pH
and the lower organic carbon
content.
15. Two loading rates, the Texas soil,
and nine chemicals (phenol and eight
chlorinated phenols) were used in
this study. Both first and zero order
kinetics satisfactorily fit the water
soluble fraction (WSF) chemical loss
data and the toxicity reduction data.
16. The higher chemical loading rates
resulted in higher chemical concen-
trations in the WSF and higher WSF
toxicities at the beginning of the
experiments.
17. The higher chemical loading rates
generally resulted in slower chemical
losses (higher half lives) and slower
toxicity reduction. However, at both
loading rates for each chemical, the
chemicals were degraded and the
toxicity was reduced. No differences
due to the loading rates were
apparent in zero order kinetics.
18. The loss of the chemicals in the
WSF was about 1.5 times faster than
the loss of the chemical in the soil.
19. The WSF toxicity for each chemical
decreased as the soil chemical and
the WSF chemical concentrations
decreased.
20. The WSF toxicity decreased at about
the same rate as the WSF chemical
concentration when the data for all
nine chemicals were compared.
21. No enhanced mobilization of the ap-
plied chemicals occurred as the deg-
radation and detoxification occurred.
22. No water soluble toxic products ap-
peared to be formed as the chem-
icals were degraded in the soil.
23. The Freundlich equation described
the sorption of 2,4- and 2,6-Dinitro-
toluene in the two soils satisfactorily.
It did not do so for TNT, RDX, or
HMX.
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24. No loss of 2,4-Dinitrotoluene occur-
red over a 47-day study even though
the loading rate used was de-
termined to be acceptable using pro-
cedures discussed in Section 4 of
the full report. Degradation loss rates
were obtained for 2,6-Dinitrotoluene
and TNT. First order kinetics were a
better representation for TNT than
were zero order kinetics.
25. The half life of TNT in the Mississippi
soil was shorter, and the loss faster,
than in the Texas soil. No difference
in the loss rates in the two soils for
2,6-Dinitrotoluene was apparent.
26. The sludge resulting from the
manufacture and processing of ex-
plosives contained: (a) high concen-
trations of nitrogen and COD, (b)
concentrations generally less than 10
mg/l for heavy metals, and (c) no
TNT, RDX or HMX.
27. The munitions sludge had a high
toxicity as measured by the
Microtox® procedure. The constitu-
ents causing the relative toxicity
were in the soluble phase of the
sludge.
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Raymond C. Loehr is with the University of Texas at Austin, Austin, TX 78712.
Scott G. Hullng is the EPA Project Officer (see below).
The complete report, entitled "Treatability Potential for EPA Listed Hazardous
Wastes in Soil," (Order No. PB 89-166 581/AS; Cost: $21.95, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
Ada, OK 74820
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
-., I
Official Business
Penalty for Private Use $300
EPA/600/S2-89/011
885
8R(NCH
IL
CHICAGO
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