GUIDANCE DOCUMENT FOR SUBPART F
Air Emission Monitoring
LAND DISPOSAL TOXIC AIR EMISSIONS
EVALUATION GUIDELINE
Office of Solid Waste
U.S. Environmental Protection Agency
Washington, D.C.
December, 1980
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FOREWORD
This manual presents a procedure for assessing the impact of
hazardous air emissions from disposal facilities on the downwind
population. The disposal facilities considered in this document include
surface impoundments, seepage facilities, landfills, and land treatment
facilities. The application of the procedure may be extended to waste
piles depending upon the similarity of air emissions routes and the
characteristics of the emitting surface in contact with the atmosphere.
These facilities will hereinafter be referred to as disposal facilities
or land disposal facilities.
The report is prepared to provide the facility owner or operator
and the permit writer guidance on evaluating .the performance of facility
design, and preparation and analysis of the permit application. The
manual will also provide a quantitative tool for the rational evaluation
of hazardous air emissions from land disposal facilities, and for
prediction of ambient air quality of hazardous waste components.
Chapter 2 presents the method of estimating the hazardous air
emission rates from disposal facilities. Chapter 3 describes a screening
technique for predicting ambient air quality, The preliminary evaluation
by the screening technique will form a basis for requiring a more
sophisticated evaluation of the impact of the-disposal facilities.
Chapter 4 is an attempt to gather data on the present background
concentrations of hazardous chemicals in urban and rural ambient air.
The background concentration will affect the extent of emission control
required for prevention of adverse health effect on the downwind public.
A logical source of such information would be site-specific monitoring
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data. The data properly taken around a disposal site will provide a
basis for performing an ultimate test of comparing the predicted with
actual result. The example calculations presented in Chapter 6 will
serve as a quick reference for the use of the analytical techniques.
This report was completed around mid-December, 1980, as a part of
documents to support proposed regulations which will be published in the
Federal Register in February, 1981.
11
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CONTENTS
Page
I. INTRODUCTION 1
II. ESTIMATION OF EMISSION RATES FROM DISPOSAL FACILITIES 5
1) Surface Impoundments 5
2) Landfills 12
3) Land Treatment Facilities 18
III. AMBIENT AIR QUALITY MODELING FOR AREA SOURCES 22
IV. EVALUATION OF EXPOSURE CONCENTRATION 27
V. EXAMPLE CALCULATIONS 44
1) Estimation of Emission Rates from Surface Impoundments 45
2) Estimation of Emission Rates from Landfills 45
3) Estimation of Emission Rates from Land Treatment 47
Facilities
4) Dispersion Modeling-Screening Technique 57
5) Consideration of Other Health Criteria 60
VII. REFERENCES 68
APPENDICES
A. Methods for Determining K-Values 70
B. A Model for Volatile Chemical Emissions to Air
from Landfarming of Oily Wastes 76
111
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LIST OF TABLES
Table No. Title Page
1 Mass Transfer Coefficients for Reference Compounds 11
2 List of Chemicals Assessed Weight of Carcinogenic 28
Evidence
3 Ambient Air Concentrations of Probable Carcinogens 32
4 Comparison of Ambient Air Concentrations and
Maximum Allowable Concentrations 36
5 Harzardous Organic Vapors and Particulate Trace Metals 42
in Ambient Air at Hazardous Waste Facilities
IV
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INTRODUCTION
1.1 Purpose
This guidance manual is prepared to present a brief description
of technical information that can be used in evaluating the potential
of emissions of volatile hazardous chemicals into the atmosphere
from land disposal facilities. The land disposal facilities include
surface impoundments, seepage facilities, landfills, and land
treatment facilities. The method for predicting the impact of the
facility on ambient air quality essentially consists of two step
processes; first, it requires estimation of emission rates of toxic
components from a land disposal facility; second, this information
is in turn used for air dispersion modeling to predict the ambient
air quality.
1.2 Content Description
The dispersion modeling technique is rather general to the
extent that it is applicable to area sources of which land disposal
facilities are a type. The estimation of emission rates, however,
requires a particular method that is suited to each application of
land disposal facilities. Although waste piles are not specifically
covered in this report, it is believed that one of the methods
(most likely the land treatment model) may be used for the estimation
of volatile emissions from waste piles based on the similarity of
transport routes and configuration. In all cases the estimation
method for the emission rates addresses volatile constituents in
the waste. The particulate matter emissions are generally derived
from the expression of "emission factors", but this aspect of
emission rate estimation is not addressed in this report.
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The techniques presented here are predictive models, and do
not involve the methods of actual measurements. However, the
methods of performing measurements of emission rates as well as
ambient air concentrations of waste constituents have been established,
and these measurements may be effectively used to verify the accuracy
of the prediction.
The land disposal facility should be designed, maintained and
closed in a manner which will not impair post-closure uses of the
land and soil, and public health will not be endangered due to air
emissions and water infiltration. The procedure presented here
will allow one to make a preliminary evaluation on the adequacy of
design for a disposal facility from a standpoint of atmospheric
dispersion of volatile hazardous chemicals. The evaluation examples
will serve as a quick reference problem for estimating the emission
rates and for comparing the estimated concentrations with the permit
provisions. The approach to arriving at allowable ambient air
concentrations will be presented in a Permit Writers Guidance Manual
which will expand the material contained in Chapter IV of the manual.
The evaluation procedure can be used to check the adequacy of
the facility design to minimize the potential of air emissions of
hazardous substances as necessary to protect public health.
The main body of the report will address various models needed
for the evaluation and predictions. Specific examples are shown in
a later chapter to facilitate their use.
1 .3 Use of Other Manuals
EPA has published a number of technical resource documents and
manuals to support recently proposed RCRA regulations. Each document
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supports the appropriate area of concern. But some documents also
contain references and a brief description of the subject matter
related to air emissions. These documents and manuals include:
0 Management of Hazardous Waste Leachate
0 Guide to the Disposal of Chemically Stabilized and
Solidified Wastes
0 Closure of Hazardous Waste Surface Impoundments
0 Design and Management of Hazardous Waste Land Treatment
Facilities
0 Soil Permeability Test Manual
0 Leachate Characterization from a Hazardous Waste Facility
0 Landfill Closure Manual
0 Ground-Water Monitoring for Owners and Operators of
Treatment, Storage or Disposal Facilities
0 Landfill and Surface Impoundment Performance Evaluation
0 Evaluating cover Systems for Solid and Hazardous Waste
0 Guide to the Disposal of Chemically Stabilized and Solidified
Wastes
0 Hydrologic Simulation on Solid Waste Disposal Sites
0 Management of Hazardous Waste Leachate
0 Lining of Waste Impoundment and Disposal Facilities
0 Design and Management of Hazardous Waste Land Treatment
Facilities.
0 Closure of Hazardous Waste Surface Impoundments.
This manual is not directly related to any of the above manuals.
However, the reader is encouraged to consult the above documents
for any materials relevant to the 'evaluation of air emissions.
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The predictive models presented in this manual are based on the
best information currently available in the literature. The correlations
pertaining to the estimation of volatile emissions from surface impound-
ments are presently being tested in the field using the "concentration
profile technique." In the models for estimating emissions from covered
landfills, the diffusion in soil pore is considered a rate controlling
step. The effect of barometric pumping and thermal diffusion on the
rate of emissions has been mentioned in the literature. But the information
is lacking on importance of these phenomena in comparison with diffusion
controlling transport. The land treatment model is rather a recent
endeavor and would require further experimental verification to identify
all parameters affecting air emissions and to substantiate its accuracy.
The techniques of measuring air emission rates and of monitoring
ambient air concentrations of specific chemicals are beyond the scope
of this manual and are not presented here.
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II. ESTIMATION 0? EMISSION RATES PROM DISPOSAL FACILITIES
1 ) Surface Impoundments
la order for the hazardous compound in the waste to "be
emitted into the atmosphere, the following three 'elementary
processes must occur:
1. The hazardous compound, in the surface impoundment must
travel to the surface where it is in contact with the atmosphe .
2. At the surface(or liquid-air interface), the hazardous
compound must vaporize or establish the vapor liquid equilibrium
which determines its concentration in. the air phase in the
*
immediate vicinity of the surface cased on the concentration
in the liquid phase at the.surface.
3. Once vaporized at the interface.,, the hazardous component
»
must be' transported into the bulk, of the air st-ream.
In the transport of the hazardous component in the liquid
and air phases corresponding to steus 1 and 3 above,, it encounters
inherent resistances.. If a pure volatile liquid is vaporized
into the atmosphere, the resistance for steps 1 and 2 is zero, and
only the resistance in the air phase (step 3) is controlling. On the assumption
of no resistance for mass transfer rate in Step 2, the science of "thermodynamics"
can be used to quantify the equilibrium phenomena. The mass transfer coefficients
(k , k ) expressed in a unit of gr-mol/cm "sec can also be expressed in units
L g
of #-mol/ft -hr, cm/sec, or I/day. The method of conversion is shown in the
examples. The reciprocals of the resistances encountered in steps 1 and 3, or
mass tansfer coefficients are designated by
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kr : liquid phase mass transfer coefficient(step 1 above),
gr-mol/cm - sec.
k_ : gas phase mass transfer coefficient(step 3 above),
o
gr-mol/cm -sec.
In addition to the volatilization of the hazardous component,
other processes would occur simultaneously in the surface
impoundment. Engineers are often concerned with biodegradation,
outflow in the effluent and sludge,
transport through soiiT^and accumulation. Quantitatively, one
can write the following material balance for the amount of
a hazardous substance being transported and transformed:
*
Input = Output •+• Biodegradation + Air Emissions •*• Transport
through Soil + Accumulation
Our primary concern is the air emissions. The rate of air
emissions of a hazardous substance, i, is expressed by**
o. « X,-A (x. - x*) * MW - (1)
-1- i- i i i
where Qi : rate of air emissions of a component i , gr/sec.
Z.r • overall mass transfer coefficient (expressed in the
liquid phase • concentration), gr-moi/cm2-sec
A : area of surface impoundment, cm2
X-L : concentration of component i in the impounded
liquid, mole fraction
* Output includes the amount in the effluent and sludge.
.£.
** The correct formula is ei - y (Q± + Q. ) = KL A (x± - x±) where
y± is the mole fraction of the component i in the air phase. Since
Qj=0 (subscript j refers to-air), and d-y± ) =1 for low air
i
emissions, Equation (1) results.
6
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x± : liquid-phase concentration of component i in-
equilibrium with the air phase concentration of
component i , mole fraction
i : molecular weight of hazardous component i
In Equation (1) 3Lr is the reciprocal of the overall resistance
atrributable to the sum of individual resistances. The method
of combining the individual mass transfer coefficients is well
established.
(2)
where J. is the constant establishing the equilibrium between
the liquid and air phases expressed by y± = X xit and yi is
the mole fraction of component i .in the air phase. There are
several ways of determining the values of £ (X-values) for
use in Equation (2). There is a compilation of the results of
the vapor-liquid equilibrium experiments, and Henry's law
constants, from which the K-values can be calculated. The I-values
can also be determined from Raoult's law and the activity
coefficient concept. Detail methods on the evaluation of the K-values
are beyond the scope. of this report. For a brief summary, the reader
may consult the appendix.
It is commonly assumed that the concentration of component i
in the air stream is negligible compared with that in the liquid
phase, that is x* = 0 in Equation (1). Hence an adequate expression
for the emission rates from the surface impoundment is
X^A-Xi (3)
In ord.er to calculate the emission rates using Equation (3),
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the overall mass transfer coefficient must be known. The mass
transfer coefficients, kr and k , in the liquid and air phases
are correlated and reviewed' by various experimenters in academic
institutions, and industries (7) (22). The results are summarized below:
1- Surface impoundment retaining natural surface
a. liquid- phase mass transfer coefficient
*. 3J. «
k. = (H.4Re - 5) ^r1-^ - , *y Cohen(4) (4)
** •' -
k- = 5.78(1.024)0~2° U°-67 H~0-85 i'H2° , by Owens'ds) (5)
Jj O U "~ "™ "~ *" """" ^"™
I)02,H2C
b. gas-phase mass transfer coefficient
v n no^« TT°*78 u-0.67 ri-0.11 Pair
k = 0.0958 U£ir Lsc de - ^ by MacKay(11,
2. Surface impoundment aerated by the mechanical surface aerato
a. liquid-phase mass transfer coefficient
J (POVR) (l.024)e-2°(
by Reinhart (14) (g)
"When the air emissions from the non-wastewater surface
impoundment need to be estimated, the ratio of the diffusion
(Note: In the correlations given by Equations (4) - -(8) , the mass transfer coefficients,
kL , k , are expressed in Ib-mol/ft -hr. The conversion to gr-mol/cm2•sec is
straightforward.)
8
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coefficients of component! in water in Equations (4- or 5) and
(7) should be replaced by the diffusion coefficients in the
solvent to calculate the liquid-phase mass transfer coefficients.
Other investigators recommend the use of the relationship (is)(is),
MW.
j in a solvent _ / ^_ >0.5 f^\
Tt MW
•"j in a solvent i
The similar relationship has been used for the approximation of the
gas-phase diffusivity ratios. Kyosai compares the experimental results
with 'the ratios of molar or critical volumes in relationship to the
diffusivity equation proposed by Wilke and Chang (24 ).
The emission rates of volatiles from the surface impoundment
could be seasonal due to the seasonal temperature variation.
The correction to the temperature variation can be incorporated
in the evaluation of the mass transfer coefficients by recog-
nizing the factors dependent upon the temperature.' There are
explicit terms for the temperature correction.-in...the., correlations
of the mass transfer coefficients. The dependence of the diffusion
coefficients upon temperature can be accounted for noting that
the gas phase diffusivity is proportional to temperature by
1.5 power and the liquid phase diffusivity is directly propor-
tional to temperature.
Por a given surface impoundment, the individual mass-transfer
coefficients for various compounds can be simplified by
refering to a typical compound whose base values are known
or easy to evaluate. Several experimenters (13), (is), (is) used
oxygen as reference compound for the liquid phase mass transfer,
and water vapor as reference compound for the air phase mass
transfer. Upon taking the ratios of Equations(4 or 5), (6), (7),
and (8) and considering the temperature effect with respect
9
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to a reference compound and temperature(25°C used in the present
example below), one can obtain
1 . Natural surface impoundment
a. liquid-phase
- 273 * e
MWi 298
b. gas-phase
273
(11)
298
2. Aerated surface impoundment
a. liuid-hase
MW0~ n 9- 1.0249""20 273-1- e 0.5
(12)
b. gas-phase .
298
273 •«• ©
The liquid phase mass transfer coefficients for oxygen and the gas-phase
mass transfer coefficients.for water vapor are calculated using Equations
(5) , (6) , (7) , and (8), and listed on Table 1. The convective liquid-phase
—5 2
mass transfer coefficients calculated by Equation (4) is 4.2 x 10 gr-mol/cm -sec
~3 2
in comparison with 2.4 x 10 gr-mol/cm -sec calculated by Equation (5). The
former represents the results obtained from the wind tunnel experiments, and
the latter is for free flowing stream. The conservative number is used. The
liquid-phase and gas phase mass transfer coefficients for all substances
10
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of concern can be calculated individually by Equations (4) through (8), or
more simply by Equations (10) through (13). The experimental and calculated
mass transfer coefficients for O in the liquid phase and HO in the air
phase is needed to use Equations (10) - (13). The field measurement values
in the literature are comparable to these values (15) (22).
Table 1. Mass Transfer Coefficients for
Reference Compounds (25 C)
Natural Surface Turbulent Surface
2 -5
k (gr-mol/cm -sec) 2.4 x 10 0.12
22
(0 in water) 0.18(lb-mol/ft -hr) 866.2(lb-mol/ft -hr)
2 -5 -4
k (gr-mol/cm -sec) 2.7 x 10 4.6 x 10
(H20 in air) 0.2(lb-mol/ft2-hr) 3.41(lb-mol/ft2-hr)
Care must be taken in estimating the emission rates from the aerated
surface impoundment, particularly the activated sludge process. It can be
visualized as consisting of two distinct zones where emissions occur. One
zone is the core of aeration where the mass trnasfer coefficients calculated
by Equations (7) and (8) are applicable. Beyond a certain region of
turbulence caused by aeration, the turbulence diminishes. The air emissions
are comparable to the natural surface impoundment, and the mass transfer
11
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coefficients for the second zone can be calculated by Equations
(4' or 5), and (6). The emission rates from the turbulent and
convective zones must be summed to obtain the overall emission
rates from an aerated surface impoundment (7)» It can be shown
that in order to use Equation (3) the area-averaged overall
mass transfer coefficients give identical answers:
In Equation (14) £r is the area-averaged overall mass transfer
coefficient to be used -in Equation (3) for the aerated surface
impoundment, (£r)c is *ke overall mass transfer coefficient
for the convective region, (Ej^j is the overall mass transfer
coefficient for the turbulent region, A_ is the effective
C
surface area of the convective region, A^ is the effective
surface area- of the turbulent region, and A is the total
» .
• .
surface area of the aerated surface impoundment. A /A and
c
Am/A represent the fractions of the' convective and .turbulent
surface areas, respectively.
2) Landfills
The approach to estimation of air emissions from landfills presented here
is an extension of the study on hexachloro benzene emissions
from landfills undertaken under the EPA contract(7). The estimation
method described by Farmer is based on the diffusional process
in the soil pore. Additional emissions of air pollutants caused
by generation of gases, in soil are shown by Thibpdeaux (17) to
be a significant portion of air emissions when the hazardous
12
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waste, is land-filled with gas-generating: wastes such, as domestic
garbage.
Farmer, et. al presented a method of estimating" the emission
rate front landfills based on the controlling- mechanism of
diffusion: through: soil.. ChemicaL vapors- originated front hazardous
waste move upward by molecular diffusion until the vapors reach
the air-soil interlace. The rate of air emissions at steady state
is expressed by
10/y ^
•p f r* • rr- N
a io* i
where q^ is the rate of emissions of component i per- unit area,
gr/cm2-sec r B^ isr the diffusion coefficient of component i,. cm.2/sec ,
Ba is air-filled porosity, cm?/cm?, (£ » I - P^/2.65 — w-fB), p^ is
the soil, bulk: density r gr/cnr r w is the soil water- content,, gr/gzr,
F£ is the total porosity, cm?/cmr, (P^ » t — fB/2.65), h is the
depth: of soil, cover, cm,. dia is the concentration: of component i
at the Soil—ai2T interface, gr/cm ,. C. is the concentration of component
i in the air space at the immediate vicinity of the waste(or- in.
equilibrium with the waste), gr/cm3.
Thibodeaux- presented the following; simple expression to
incorporate the long-temr values for- the site-specific soil
conditions (17).
q. = - E^ , (Cf — C, ) (2.44 x IO4) C16)
where 2.44 x 1Q4 ig the molar volume, of gas, cm /gr-mbl, :
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mass transfer coefficient(expressed in the gas phase concentration),
gr-mol/cm -sec, and C. is the concentration of component i in the air far
away from the soil-air interface. The overall mass transfer coefficient is
expressed by
1 1 1
K k . k .
where k . is the soil phase mass transfer coefficient of component i
(expressed in the gas phase unit), gr-mol/cm -sec, or k . = D.'6/(h*'c« 2.44x10 ),
G is the porosity of the cover material,t is the tortuosity, and k .is the
air phase mass transfer coefficient, gr-mol/cm -sec.
It has been shown, that the resistance to air emissions in the
air phase is negligible compared with that in the soil phase (17).
Equation (is) can be used with C^ =0 for.all practical purposes. .
The diffusion coefficient in the gas phase is dependent upon
the type of the compound, and temperature, and can be related to
the variation of molecular weight and temperature by the following
proportionality relationship (7) $.8).
1 0.5
'i
or 1 i «=
°-5 < — > "1
14
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where M¥^ is the molecular weight of component it. gr/mol,. and T. is
temperature, °K» ?or matter of choice,, a temperature of 298°K is
used for 1^,. and ID1 * o.oss Cm2/sec for benzene is. used(MW=7S.l).
Equation C19) "becomes
D. ~l.Sxlcf4C - )- £- (2Q)
MW.,
It is convenient to use- the partial pressure of a hazardous:
component- in the- rapor space in place of the equilibrium concen-
tration. One can express.
P?
Bar
X. (21)
-
where p^ is. the partial pressure of component i in equilibrium, with
the waste,. mmEgv and H is the gas. constan1rr(62,363 CTi3-imnHg/°K.moi) .
* *
The emission rate of a hazardous component from a landfill can
"be estimated with the use of Equations (15), (20), and (21), or
(16) and (17). information needed for the estimation includes
the porosity, moiture content, and bulk density of cover soil,
the partial pressure of component i in equilibrium with the
waste, the cover thickness, the molecular weight of the component,
temperaure, -and the landfill area.
The soild waste landfilled with the hazardous waste is
subject to the biological process occuring in soil, and generates
gases due to anaerobic processes. The convection caused by the
generated gases carries volatile chemicals toward the surface
of soil. Thibodaaux (17) incorporated the transport mechanism
15
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to account for the air emissions resulting from the moving gas.
The equation presented for the rate of air emissions is
q, = V - : - + ¥ 0, (22)
where V is the average gas velocity in the soil pore in the
upward direction, cm/sec. In order to obtain the concentration
of component i at the soil-air interface, Cio, the air- phase
mass transfer given "below "by Equation (23) should be utilized,
*i = - kg,i (Cioo - Cio> 2'44 X 1°
Equations (22) and (23) should be solved simultaneously to
estimate the emission rates from a landfill with gas generation.
Several examples of using Equations (22) and (23) are given in
the example section.
The comparison between Equations (15) and (16) shows that
the porosity and the air-filled -oorosity are related by
10/3
Pa
C = 1.73 - (24)
P2
*T
There are other transport processes which will add to air
emissions. Several investigators are concerned with the effect
of barometric pumping and thermal diffusion caused by temperature
gradient across the soil. It appears that the role of these
processes is insignificant compared with the overall emissions.
Hence these additional emissions are not considered in this report.
16
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Synthetic material is often used as a cover material.
Farmer expresses the effectiveness of the synthetic material
in retarding the volatilization and movement of chemical vapors
in terms of the equivalent thickness of soil (25). He presented
a graph wich correlates polyethylene thickness (h-, cm) in
terms of the equivalent thickness of soil (h , cm) corresponding
eq.
to a bulk density ( fL) of 1.19 gr/cm and a soil water content
(w) of 0.2 gr/gr. This correlation can be presented by the
following equation:
(25)
h
eq
h
When synthetic material and soil are used together in layers,
their individual resistances to air emissions are additive.
Equation (15) can be rewritten as
1
h
10/3 ?
P /P
rc, / rnfi
heq
10/3 9 \
P /P
ro-l ' rV\
ci
(26)
where P . and Prp1 are the air-filled porosity and the total
porosity, respectively, used in obtaining the equivalent soil
thickness. The data presented by Farmer can be used to evaluate
,, as follows:
1.19
the values of P , and
T1
2.65
Pa1 = PT1 ' (
Then Equation (26) becomes
= 0.551
= 0-313
17
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or
h
,10/3
134.6
0.31310/3 /0.5512
(27)
10/3
+ 1962.8
(28)
Similarly, the estimation of air emission rates from a
landfill covered by soil and polyethylene film with internal
gas generation can be made "by
. = V
Di ^10/3/^2
+ 1962.8 hf )] - 1
+ V C* (29)
3) Land Treatment Facilities
There is very limited information with regard to models
and experimental data dealing with air emissions during land
treatment operations. Recent experimental results sponsored
by API indicate that important variables significantly affecting
air emissions include soil type, humidity, and loading rate.
These experiments are carried out on a laboratory scale using
18
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oily sludges generated in refineries. Other factors under study
are temperature, air velocity, and mode of application. The
sludges are applied into soil by surface spreading and subsurface
injection.
The rate of emissions at time t (sec.) after the application
of the waste by surface spreading or subsurface injection can
*
be expressed by
Dei Cig
q, = =75- (30)
"*• ^ /^ T"N I A / T_ 1_ \ ^"t ^ I / £•
mio
2
where q. is the rate of emission of component i, gr/cm -sec,
D . is the effective diffusivity of component i in the air-
O
filled soil pore, cm /sec, m. is the initial amount of component
i placed for land treatment, gr, h is the depth of subsurface
S
injection, cm, h is the depth of soil contamination below the
soil surface, cm(assumed to be 5 - 6 inches = 12.7 - 15.24 cm),
2
A is the surface area of waste application, cm , C. is the
gas-phase concentration of component i at the oil-gas interface
in the soil pore, gr/cm .
The concentration of component i in the gas side of the
interface, C. , can be determined by (See the appendix for
derivation)
* See the appendix for detailed derivation supplied by Thibodeaux.
This model has not been verified experimentally except the API's
preliminary data.
19
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z
1 + H,
o
iwo
(31)
hs -
where H is the Henry's law constant in concentration, C. is
the initial concentration of i in the oily waste, gr/cm , z is
the oil layer diffusion length, cm, D . is the effective
diffusivity of i in the waste, cm /sec, and a is the interfacial
s
p "2
area per unit volume of soil, cm /cm .
The average emission rate over the evaporation life-time
t, sec can be obtained by integrating Equation (30) and dividing
with respect to time, which yields
q± = 2 q at t = td (32)
where t, is the dry-out time, sec, to be determined by
i Cig A
(33)
The path length of diffusion through the film and lunrD type of
oil in soil can be estimated from
zo =
PpWf
for film form oil
(34)
w
zo =
d
2
for lumn form oil
(35)
v/here d^ is the soil clump diameter, cm, p is the soil clump
density (2.65 gr/cm5), wf is the fraction of oil in film form
20
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on the soil, and f is the waste oil density, gr/cm . The interfacial
area is
a = 6/d for film (36)
s p
a = 2.7/d for lump (37)
The mass fraction of oil in the film form can be estimated by
0.5 M,
W£ = (38)
h j>_ A
p JB
where P is the bulk soil density, gr/cm , and M is the total application
amount of waste, gr. The example calculations given later will facilitate
the use of the above equations.
Volatile wastes are incorporated into soil for land treatment by sub-
surface injection. This method of application reduces volatilization in
comparison with surface spreading, and bring the waste in intimate contact
with microbia in soil. The depth of subsurface injection is 5 - 6" in the
commercial practice.
21
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III. AMBIENT AIR QUALITY MODELING POR AREA SOURCES (5)
Hazardous substances evaporated into the atmosphere from disposal
facilities may introduce significant impacts on human health and the
environment in the surrounding region. we win consider the use of air
quality modeling to assess whether emission reductions are necessary
to avoid exceeding acceptable levels of hazardous substances.
Once a maximum acceptable concentration for a hazardous substance
is designated,,air quality modeling can be used to estimate a maximum
allowable emission rate. For modeling purposes, disposal facilities
can be considered as area sources with emissions occurring at ground
level. In most cases it can be assumed that no plume rise will occur.
Since the health effects being considered are thought to be related
to long-term exposure, the modeling techniques recommended calculate
annual average concentration estimates. The highest concentration
caused by a ground-level source occurs near the source. However, it
is not possible to estimate concentrations closer than 100 meters
from a source using standard dispersion models. Therefore, the model-
ing for this regulation should focus on concentrations at 100 meters
from the facility or, if the property line is greater than 100
meters from the facility ^ at the property line.
Two approaches are possible for estimating; impacts of disposal
facilities. - The first approach is a screening technique, i.e.,. a
simple approach suitable for making preliminary concentration estimates.
The second approach is to use a refined model, i.e., a computer program
for making reasonably accurate concentration estimates. It is not
always possible to use the screening technique, in which case it is
necessary to use the refined model at the outset. Also, if the
screening technique suggests that the facility may have an unacceptable
impact, the refined model should be used to estimate the impact more
accurately.
The screening technique is based on treating the disposal facility
as a virtual point source. Disposal facilities have their emissions
initially spread over the area of the facility. The virtual source
approach hypothesizes a point source located at an appropriate distance
upwind such that the horizontal dispersion at the facility -}s equal
to the facility width. The horizontal dispersion downwind of the
facility can then be simulated as if all the facility emission
were being emitted from the virtual point source.
The calculation of the impact of a disposal facility is simpli-
fied by using the virtual source approximation. Further simplification
is possible by assuming that the facility is a ground-level source,
assuming no atmospheric destruction or decay, and using one assumed
meteorological situation. Starting, for example, with the equation
underlying the Climatological Dispersion Model (2> • the equation
simplifies to:
22
-------
where' x a net concentration (gr/m )
Q * emission rate (g/sec)
LV = virtual downwind distance to receptor
or - vertical dispersion coefficient (m) (given in Figure 1
. as a function of downwind distance)
u - wind speed (ra/sec)
In order to estimate the annual average concentration at a given
receptor it is. necessary to multiply this concentration by the frequency
with which the given meteorological conditions occur- For the wind
sector (s) in which the source impinges the receptor, refined models
perform a summation of the concentration for each stability class and
wind, speed class times- the frequency with which those conditions occur.
The screening technique uses just one stability class and one wind
speed to represent average conditions. The screening technique is
limited to cases where the source emissions impinge the receptor in
only one wind sector,, i.e.,. the. source lies entirely within one sector
upwind. Since each sector is 22-1/2°, the source must be no more than'
22-1/2°
ZL tan ( y - — ). Thus, for a source to receptor distance (L) of 100 m, the
screening technique should only be used if the source is less than 40
meters in width.
If the source is adequately small compared to the source-
receptor distance, the screening technique can be used by using as a
frequency factor the total frequency that the wind is in the sector
of interest without regard to speed or stability class. The equation
for calculating concentrations then becomes:
(40)
where $ = frequency that wind blows fro'm the sector of interest
and other terms as defined above.
The following are recommendations for determining values for
each of the parameters in the concentration equation:
2
-z,
-------
X ~ This 1S the net concentration resulting from uncontrolled
emissions and Is to be compared to the acceptable concentration.
The concentration is proportional to the emission rate. Therefore, if
the estimated concentration is a given factor higher than the acceptable
concentration, then the acceptable emissions rate can be found by
reducing the Initially used emission rate by that factor.
Q - Earlier discussion in the document discusses the calculation
of the emissions rate. Note that this is a total emissions rate for
the entire area of the facility, gr./sec.
LV.- The determination of the downwind distance is complicated
by the virtual source approach used in the screening technique. LetL
be defined as the distance from the center of the facility to the
receptor. As discussed above, L should be the greater of (1) the
distance from facility center to property line, and (2) 100 meters.
(Concentrations cannot be estimated less than 100 meters from a source.)
The virtual point source approach also requires determining how far upwind
a point souce would have to be located to have the same horizontal dis-
persion as is inherent in the area source. .This distance from the virtual
point to the center of a disposal facility (L ) may be calculated here as :
, , cot (^)
Where S = the V/idth Of the facility perpendicular to the most
frequent wind direction.- m.
The distance to be used in calculating concentrations is the total
distance from virtual point to receptor, i.e., LV = L + L'.
a - Since D stability is by far the most frequently occurring
stability class, a should be taken from the curve for D stability
as given in Figure 1 (taken from reference 19). The distance used
to determine a should be the distance from facility center to
receptor (i.e., L , not L ), because a at the facility is assumed
to be negligible. v
u - Various references (e.g., the Climatic Atlas of the United stateson
provide information on annual average wind speed. If these references or
this data are not available, a default value of 5 m/sec may be used.
$ - The Climatic Atlas of U.S. also compiles the frequency that the
wind blows from various directions for many U.S. cities. For this
screening technique, $ should be set equal to the frequency of the most
common of the standard 16 wind directions. If this information is not
available, a default frequency of .15 may be used.
24
-------
. i Tj - ,^-^*~
1,000
~—'~ ""*' - ~-*l— •"•-. ~~ . _"'*T Hi "—._!!!_• ^'- ^*.'li—V4v;.|i"'.:!^.'« "*-' i" *~ .. "i TL.' N;;TII'-P—::'.•<•;•' T" .; ....rrr1:. "-['jt:——. .. ~ Ti'i.,".;—., • i • f"**. 'i*:— :Ti^.;;pi"i'*''*':" j
m
mm
r too
~^-.-JS~
...y:-—j—-~'-
100
DISTANCE DOWNWIND,
Figure i. Vertical dispersion coefficient as a function of downwind distance from the source.
Estimates
339-901 O - 89 - 2
25
-------
As. discussed above, the screening technique is not always suitable
for estimating the impact of a disposal facility. in particular, if
the source width is greater than 401 of the distance from source center
to receptor, the: consideration of just one sector and the use of the
virtual point source approach lead to increasingly less reliable con-
centration estimates.
If the screening technique is not suitable, or if the screening
technique implies that unacceptable impacts may occur, the Climatological
Dispersion Model should be used to obtain a more accurate estimate of
concentrations. This model considers average emission rates, and the
joint frequency distribution of wind speed and stability class for
each of 16 wind directions. (This data is generally available from
the National Climatic Center in Asheville, North Carolina.) This model
also provides a more sophisticated integration of the impact of area
sources. This model is a computerized model available on EPA's UNAMAP
system. The model is described in Reference 1. Guidance on model inputs
and other issues as given in the Guideline for Air Quality Model(20)
should be followed in performing this modeling.
For acutely toxic pollutants assessment of short-term effects
can be accomplished by using short-term air pollution dispersion
analysis for ground level concentration effects. The prediction of
the worst case conditions can be performed similarly.
26
-------
IV. EVALUATION OF EXPOSURE CONCENTRATION
The subject of risk assessment will be covered more thoroughly in the
permit writers guidance manual which EPA is planning to issue in the future.
The presentation in this Chapter will focus on aspects of evaluation pertinent
to arriving at acceptable ambient levels of hazardous substances. It is neither
attempted to recommend a risk level nor to present an exhaustive list of
chemicals exhibiting evidence of carcinogenesis ,or other health effects.
Harzardous materials volatilized from surface impoundments, landfills,
and land treatment facilities will be dispersed into the atmosphere by wind
and will impact the downwind population. The maximum allowable concentration
represents the level that may result in incremental risk of human health
over the short-term or long-term period at an assumed risk. For carcinogenic
compounds for example, the long-term effect will be cancer risk over the
lifetime. If one defines the unit risk for a carcinogenic compound (Ru) as
lifetime risk if the concentration of a hazardous substance in the air is
1 /Lgr/m and if this is breathed continuously for a lifetime, the maximum
allowable concentration, C .(/tgr/m ), at a tolerable level of risk can be
obtained by
Cmi = risk/Ru (42)
The unit risk for a number of hazardous compounds obtained from the EPA's
Cancer Assessment Group is listed in Table 2 (12),
The background ambient concentration will indicate the present level
of concentration at a locality, which becomes additive to the long-term
or short-term effect on the downwind impact. In order to study the level of
present ambient air risk for various toxic compounds, urban and rural ambient
data for several compounds have been gathered. Table 3 summarizes the collected
data. As one might have expected, the ambient air concentrations vary from
location to location.
The Water Criteria Documents (6) make use of a risk range of 10 to
10 in presenting the exposure concentration levels of cacinogens.
27
-------
Table 2. List of Chei^Hals Assessed
Weight of Carci..Jgenic Evidence
Chemical
Acetaldehyde**
Acroleiii**
Acrylonitrile
Allyl Chloride*
Arsenic
Asbestos
Benzene
Benzyl Chloride*
Beryllium**
Cadmium*
Chlorobenzene
Coke Ovens
*Changed frcro Dec. 1
**Adcted since Dec. 1
Date
1/80
2/80
4/78
9/79
4/78
6/78
1/79
8/79
12/79
5/7b
9/79
3/78
Excellent
X
X
X
X
X
Substantial
X
X
Suggestive
X
X
X
Inadequate
Data
•
X
X
Unit Riskft
.
8.5 x 10~5
9.9 x 10-"7
3.4 x 10"3
4.8 x 10"5
2.7 x HT1
2 x ID"3
, 1979 memorandum from Joseph Padgett
8, 1979 memoraivJum fran Joseph Padgett
IV)
00
-------
List of dhemicals Assessed
Weight of Cai ^nogenic Evidence
Chemical
o-Cresol
m-Cresol
p-Cresol
o-Dichlorobenzene
p-D ichlorobenzene
Diethyl-nitrosamine (DEN)**
Dimethyl-nitrosamine (DMN)**
Ethylene Dibromide
Ethylene Dichloride
Ethylene Oxide*
Formaldehyde
Maleic Anhydride*
Date
X
6/79
6/79
6/79
9/79
9/79
12/79
12/79
4/78
6/78
10/79
11/79
2/79
Excellent
Substantial
X
X
X
X
X
X
.
Suggestive
X
Inadeqjate
Data
X
A
X
X
X
Unit Risk
_ —
7.2 x ID"2
0.29 x HP2
5.9 x 10-4
1.2 x 10~5
1.2 x 10~4
3.4 x 10~5
*Charged from Dec. 18, 1979 memorandum from Joseph Padgett
**Addad since Dec. 18, 1979 memorandum from Joseph Padgett
(V)
-------
List of Cb^icals Assessed
Weight of Cai^Jiogenic Evidence
Chemical
Manganese
Methyl Chloroform
Methylene Chloride
Methyl Iodide
Nickel**
Nitrobenzene
N-nitroso-N-ethylurea (NEU)**
N-nitroso N-methylurea (NBIJ)**
Perchloroethylene
Phosgene
Polycyclic Organic Matter
Propylene Oxide
Date
8/79
1/79
1/79
9/79
12/79
6/79
12/79
12/79
4/78
8/79
7/78
9/79
Excellent
X
X
t
Substantial
i
•
X
X
X
1
1
Suggestive
X
X
X
X
X
Inadequate
Data
X
X
Unit Risk
4.8 x 1(T4
— —
1.8 x 1(T3
— ; —
.65 x 10"2
3.5 x 10-2
7.6 x 10~6
.
»
*Changed from Dec. 18, 1979 memprandun from Joseph Padgett
**Addad since Dec. 18, 1979 memorandum from Joseph Padgett
o
-------
List oE Chemicals Assessed
Weight of Carcinogenic Evidence
Chemical
Toluene
Trichloroethylene
Vinyl Chloride
Vinylidene Chloride*
o-Xylene
m-Xylene
p-Xylene
Date
8/79
8/78
8/78
5/78
9/79
9/79
9/79
Excellent
X
•
Substantial
X
.
x
*
Suggestive
t
I
Inadequate
Date
X
X
X
X
Unit Risk
4.2 x 10-6
4.1 x 1(T6
3.0 x lO"5
^Changed from Dec. 18, 1979 memorandum from Joseph Padgett
**Added since Dec. 18, 1979 memorandum from Joseph Padgett
POM - It should be emphasized that POM represents a mixture of organic compounds. There is substantial
evidence that some components of POM particularly frcm cxmbustion processes are associated with induction of
human cancer. Special attention should be given to POM emission because not all the components have evidence
for its carcinogenic action. So the source and composition is important in characterizing the specific POM
emission.
Beryllium - The risk unit is very high and may be revised when final data are available from the Mancuso
study.
-------
Table 3
Ambient Air Concentrations of Probable Carcinogens*
Los Angeles ' New York Azusa Bayonne Near Gas Urban
Calif. N. Y. . Calif. N. J. Station
.flanges Av.
Av.
Av. Ranges Ranges Ranges Av.
Rural or
Background
Av.
Chemical
highest
Acetaldehyde (6) (6)
13.1 / . y
Acrolein
Acrylonitrile
Allyl Chloride
Arsenic
(1000)-
t(L\ ( C\ ( f-\
(83000) (3000) v; (400) ^ '
(0.003)
Asbestos -(0.065 )J6^ \(6)
Benzene p>7 15
/ s~ \ \ O
2400(6; 0.017
Ben/yl Chloride
Beryllium
(0.006)
C3dmiUm . ~ (0.007) ^ ,
(0.001) ,
--(0. 008) ^6)o. 001 5 )^6^ (0.0001
(0.001) (o.03) (8) ° ~
^(Q.3)^8^ ' (0.0001) *• -1
Clilorobenzene
Coke Ovens I
*.Concentrations in ppb; ( ) in
Superscript refers to the reference cited.
-------
Urban
Ranges Av.
Rui 3 or
Background
Chemical
o-Cresol
m-Cresol
p-Cresol
o-Dichlorobenzene
p-Dichlorobenzene
Diethyl-nitrcsanune (DEN)
Dinethyl-nitrosamine (DMN)
Eth/lene Dibronide
Ethylene Dichloride
Ettiylene Oxide
Formaldehyde
Maleic Anhydride
-------
Los Angeles New ,?r
Calif. N. \
Azusa Bayonne Near Gas Urban
Calif N. J.• Station
Ranges Av. Ranges Av. Aw
Ranges Av.
Rural or
1 jkground
Av.
Chemical .
Manganese
Metliyl Chloroform
Me thy Lena Chloride
Methyl Iodide
Nickel
Nitrobenzene
N-nitroso-N-ethylurea (NEU)W
N-nitroso N-metlylurea (NRU)
Perchloroethylene
Phosgene
Polycyclic Organic Matter
Propylene Oxide
0.6 , o 0.01
^2 -12 °-05 °'035
(0.009) (0.002)
°-001 0.009
-v.10
-------
n,
Los Angeles New York ^Jmsa Bayonne Near
Calif. N. Y. Calif N. J. Gas
Station
Ranges Av. Ranges Av. Av. Range
Urban
Range Av,
or
Background
Av.
Chemical
Toluene
Trichloroethylene
Vinyl Chloride
Vinylidene Chloride
o-Xylene
m-Xylene
p-Xylene
^125(D 57(D 14(D
.53(1) 8(1) 3<1)
^61^) 16^) 5.5(1)
^25(1) 6(D 2(D
VJ1
Hexachlorobenzene
Chloroform
PAH
Toxaphene
TCDD
Carbon Tet.
(0.49)^
(73)(6)
(0.0436)
(6)
0
(0.49)(6)
(0.02)(6) (0.00053)(6
0.13
18.6
-------
4. Comparison of Ambient Air Concenti Jions and Maximum Allowable Concentration.^^ 10~^ Risk
Unit Risk Concentration @ 10"^ Risk Ambient Air Cone.(pub) .
/Ugr/m-
Chemical
Aoetaldehyde
Acrolein
Acrylonitrile
Allyl Chloride
Arsenic
Asbestos
Benzene
Benzyl Chloride
Beryllium
Cadmium
Clilorobenzene
Coke Ovens
7.9
8.5x10~5 0.1176 0.054
9.9x10~7 10.1. 3.23 :
3.4x10~3. 2.94x10~3 — (3000) ' (400)
4.8x10~5 0.208 . 0.065 3-15 0.017
2.7x10"1 3.7x10"5 - . ' : (0.0015) (L3x10"4)
_X _^ (O.OOl)
2x10 J 5x10 ' o~ (o.oooi)
/-(0.03)
Concentration in ( ) is >/gl>/m3
-------
Unit Risk Concentration ® 10 Risk Ambient Air Concentration
-o
Urban Av. Rural or Background
o-Dichlorobenzene
1.39x10~4 3.3x10~5
Diethy1-nitree amine (DEN)
~2. ' ' 3.45x10~3 1.14x10"3
Diirethyl-nitrosamne
1.7x10~2 2.2x10~3
Ettylene Dibrcmide
Ethylene Dichloride
Ethylene Oxide
Formaldehyde
Maleic Anhydride
-------
Unit Risk Conct Jration © 10 Risk Ambient Air Concentration
oo
• • "' •z . -'
yttgr/m . ppb Urban Av. Rural or Backgro
Chemical
Manganese
Methyl Chloroform
Metnylene Chloride
Methyl Iodide
Nickel
Nitrobenzene
N-mtroso-N-«thylurea (NEU) -
N-nitroso N-metlylurea (NRU)
Perchloroethylene
Phosgene
Polycyclic Organic Matter
Propylene Oxide
2.08x10~2
0.05 0.035
1.8x10~3 - 5.56x10"3 (9x10~3) (2x10"3)
. '
0.65X10""2 : 1.54x10"3 3.2x10~4
3.5x10"2 2.86x10"4 6.78x10"5 .
A 0.001 n nnQ
7.6x10~b 1.32 0.194 MQ ' U-UUy
_ ' . -__ : :
unc
-------
Unit Risk ConcentratJn. @ 10~5 Risk Ambient Air Concentration J
Urban Av. Rural or Background
Chemical
Toluene
Trichloroethylene
Vinyl Chloride
Vinylidene Chloride
o-Xylene
m-Xylene
p-Xylene
'
10
4.2x10~6 2.38 0.44
4.1x10~6 2.44 0.954
3.0x10~5 0.33 0.082
' '• .- "• 5 ' ' •'••• '
10
. . . '. ' 4 '
Hexachlorqbenzene
Chloroform
PAH
Toxaphene
TCED
Carbon Tet.
PCB
5.71x10~4
6.29x10
1.7x10"
9.43x10
2.4x10*
1.35x10^'
-5
-4
'.1.75x10-
0.159
5.89x10~5
1.06x10~2
0.0015
0.033
7.2x10"'
6.26x10"
1.27x10~6 1.1xlO~7
0.417
0.0075
0.066
0.1•- 15
5.3x10~:
1.18x10"
0.12 - 18.6
* From water quality criteria documents.
** Calculated from potency slope(4.34 l/mg/kg day) obtained from ingestion study.
0.1
1.28x10~6
0.13
-------
Table 4 is a comparison of the ambient air data with the maximum allowable
concentration calculated at 10 risk. The third and fourth columns in the
table represent the maximum allowable concentrations at 10~ risk in /tgr/m
and ppb respectively. The ambient air concentration values which are
considered "representative" for background are chosen and tabulated in
Columns 5 and 6 for the purpose of comparison. It can be seen that the
present ambient levels of some compounds are already too high to meet the
10 risk value. In fact, in certain urban areas, the ambient air levels
exceed 10 risk at present. The ambient air concentrations higher than
those in Table 3 are reported in Reference (28) for several metropolitan
areas in the State of California.
In an area with a higher background concentration, the emission rate
allowable for a disposal facility should be comparatively less. In view
of the fact that the present ambient air concentrations are mostly higher
than the level at 10 risk, it may not be possible to achieve the maximum
allowable concentration calculated by Equation (42) at that risk. The case-
by-case evaluation will determine whether or not the facility will contribute
significantly to degradation of present ambient levels so as to require
reduction or elimination of hazardous emissions. The permit evaluation
will consider risk assessment in consistency with other criteria goals.
Table 2 does not attempt to present exhaustively all carcinogenic
compounds, but is merely a collection of data that the EPA's CAG has
compiled at the time this report is completed. It is not meant to limit
control and risk assessment of hazardous air emissions only to those
compounds in the list. The compounds which are missing from the list or
the data of which are inadequate or incomplete will be added to the list
40
-------
as more data become available. If the results of a health effect study
on another compound become available from some other source, such
information could be used as a basis of evaluating the allowable
exposure concentrations.
Also other effects on human health due to exposure to high ambient
air concentrations of chemicals should not be neglected during the
evaluation process. These effects include acute toxicity, responses to
central nervous system, teratogenicity, mutagenicity, bioaccumulation,
radioactivity, nephrotoxicity, hepatotoxicity, phytotoxicity, toxicity
to aquatic species, photochemical reactivity, etc. The compilation of
data concerning these effects is not available at this time. An example
presented later will address the tecknique of evaluating the health
effect potential based on other criteria goals.
In the case of emissions of total hydrocarbons, a caution should be
exercised in evaluating the impact of a facility located in the area
where the ambient air quality of photochemical oxidants is not presently
acceptable. Since most of hydrocarbons (except methane) participate in
the formation of photochemical smog sooner or later depending upon its
reaction rates, the prevention of further degradation of the ambient
air quality of photochemical oxidants can be achieved by removal of
volatile hydrocarbons to the extent possible.
Table 5 shows the upwind and downwind concentrations of several
compounds in the ambient air around land disposal facilities (29) . The
organic species were collected on Tenax adsorbent and analyzed by GC/FID
after identifying with GC/MS. Trace metals were collected on high-volume
filters and analyzed from the collected particulates.
41
-------
TABLE 5 CONCENTRATIONS OF SELECTED HAZARDOUS ORGANIC VAPORS FOUND IN THE AMIBENT AIR AT HAZARDOUS WASTE FACILITIES
i
Ambient Air Concentrations, ppb
n-Hexane
Facility
Code No.
13
14
15
16
17
18
Background
Type©
R, I
R, I
R
R
U
U
Up-
wind
15.0
3.4
7.4
14.0
24.0
15.0
Down-
wind
11.0
10.0
20.0
42.0
98.0
42.0
Benzene
Up-
wind
4.0
8.4
6.1
11.0
28.0
10.0
Down-
wind
5.0
83.0
240.0
44.0
84.0
57.0
n-Heptane
Up-
wind
42.0
3.0
4.4
12.0
27.0
11. 0
Down-
wind
2.0
15.0
100.0
, 36.0
97.0
62.0
Toluene
Up-
wind
58.0
22.0
26.0
106.0
150.0
8.5
Down-
wind
60.0
30.0
170.0
150.0
950.0
30.0
n-Octane
Up-
wind
6.7
2.3
1.4
5.0
20.0
8.0
Down-
wind
2.2
3.8
25.0
31.0
46.0
38.0
Ethyl
Benzene
Up-
wind
4.9
3.0
3.4
21.0
28.0
16.0
Down-
wind
11.0
8.8
64.0
24.0
37.0
56.0
Xylenes
Up-
wind
10.0
10.0
15.0
94.0
79.0
54.6
Down-
wind
32.0
16.0
240.0
100.0
140.0
270.0
Dlchloro-
Benzene
Up-
wind
0.0
0.0
0.3
3.0
3.0
0.8
Down-
wind
1.6
0.6
26.0
3.0
6.6
3.7
Naphthalene
Up-
wind
0.0
0.2
0.5
0.0
3.0
0.4
Down-
wind
0.8
0.0
22.0
••• -
8.0
4.0
©Background Type: R = Rural, I = Industrial, U = Urban
-------
Cont'd
TABLE 5 PARTICULATE TRACE METALS IN AMBIENT AIR
AT HAZARDOUS WASTE FACILITIES
Facility
Code No.
01
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
DL®. ug
Back-®
Ground
Type
U
R
R
R
U
R
R
U
U
U
R.I
R,I
R
R
U
U
l/mj
Trace Metal Concentration, ug/m1
Cadmium
up- down-
wind wind
BDL©
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BOL
BDL
.03
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
.03
.04
.03
.02
Chromium
up- down-
wind wind
0.14
.11
BDL
.07
BOL
BDL
BDL
BDL
-.03
BDL
BDL
BDL
BDL
BDL
.02
BDL
0.18
.12
BDL
.17
.45
BDL
BDL
.04
BDL
BDL
BDL
BDL
BDL
BDL
.08
.12
.01
Cobalt
up- down-
wind wind
BDL
'BDL
?OL
.04
.07
.07
PPL
POL
RPI.
.01
BDL
BDL
BPl.
BDL
BHL
RP.L
BDL
BDL
BDL
.04
.13
.05
BDL
RDL
BDL
.02
BDl
BDL
DDL
BDL
BDL
BDL
.01
Copper
up- down-
wind wind
0.12
.01
BDL
.05
.06
.05
.16
.27
.12
.13
.03
• 12
.05
.02
.28
.11
0.16
.15
.04
.13
.84
.03
.20
.27
.08
.09
.06
.02
.01
.03
.17
.19
.01
Iron
up- down-
wind wind
3.2 5.9
.40 1.69
.36 10.7
4.0 30.9
10.5 71.4
1.0 2.8
.47 .29
6.0 5.9
3.9 4.6
5.5 5.6
.53 2.7
.44 .54
3.4 10.2
.70 .87
5.2 21.1
3.9 28.8
.02
Lead
up- down-
wind wind
0.51
.06
.04
.45
.90
.32
.09
.67
.35
.41
BDL
.06
.18
.02
.91
.42
•0.62
.90
.47
.80
2.83
.34
.09
.54
.38
.54
.13
.13
.28
.06
1.23
2.19
.01
Nickel
up- down-
wind wind
BDL
BDL
.04
.03
.04
.05
BDL
BDL
BDL
BOL
BDL
BDL
.02
.01
.05
.02
0.03
BDL
.05
.14
.35
.02
BDL
BDL
BDL
BDL
.02
BDL
.12
BDL
.09
.11
.02
Zinc
up- down-
wind wind
0.08
BDL
BDL
.02
.23
BDL
BDL
.21
.43
.48
.05
.08
.06
.02
.28
.03
0.33
.08
BDL
.46
2.45
.62
.11
.46
.42
.44
.10
.16
.07
.04
.70
1.53
.01
Background type: R = Rural, U = Urban, I = Industrial
© BDL * Below detection limit
© DL = Detection Limit
-------
V. CONTROL TECHNOLOGIES
Removal of volatiles from the waste prior to disposal will
reduce their air emissions. Some suggest the use of wind barriers
to slow down emission rates from surface impoundments. The techniques
of removing volatile organic compounds from wastewaters have been
extensively reviewed previously (9), (10).
Steam stripping is one of the control alternatives for removal
of volatiles from wastewater prior to surface impoundment. For
hydrocarbon mixtures, control alternatives would be recycle or
recovery of volatiles by conventional distillation processes, or
disposal by incineration. Use of adequate cover material for
landfills and adequate depth of subsurface injection for land
treatment may provide some or considerable reduction in air emissions,
Hazardous wastes landfilled with sanitary wastes are subject
to considerable volatilization as a result of decomposition of
waste material. Extraction of decomposition gas from sanitary
landfills has been practiced by means of a collection system which
consists of a series of gas wells operating under vacuum. The
evaluation of an emission potential of such a landfill will require
knowledge on the emission rate from the landfill, and the gas
collection rate.
44
-------
VI. EXAMPLE CALCULATIONS
1. Estimation of Emission Rates from Surface Impoundments
A wastewater being treated in a POTW was analyzed for its toxic compounds.
The following data was obtained
Compound Concentration(mg/L)
Benzene 20
Acrylonitrile 3
Chloroform 10
Perchloroethylene 1
The POTW has a surface area of 0.25 acre, about 10% of which is estimated
to be the effective zone of turbulence. Estimate the emission rates from
the surface impoundment.
The gas and liquid phase mass transfer coefficients for convective and
turbulent zones can be calculated using Equations (10) - (13). Specific
examples for benzene (MW=78.1) at 25 C is given below.
i) Convective zone
a) Liquid phase
32 _ ,- 273 + 25 ,-
k = ( )u's ( ) 2.4 x 10~S
11 78.1 298
gr-mol
= 1.54 x 10
2
cm • sec
b) Gas phase
or—mo 1
^
--_.. •!„„!- ,- ,-
. , _ .0.335 ...1.005 _ _ , -5 , ,._ , -5
k . = ( - ) (1) 2.7 x 10 = 1.65 x 10
.
9/1 78.1 cm2-sec
ii) Turbulent (or Aerated) zone
45
-------
a) Liquid phase
32 1.02425'20 gr-mol
k . = ( )° (D° 0.12=0.096—
., — \ /
fl 78.1 1.0245 cm -sec
b) Gas phase
k . . (^L)0'25 (I)0'92 4.6 xio"4 =3.19x.lO-4
. — \ / \ j. / ^ + \j ** -*\j — ^ • «*• -^ *» • •*• v ,_
g>1 78.1 cm -sec
We need to know the value of vapor-liquid equilibrium constant, K, to combine
the gas-phase and liquid-phase mass transfer coefficients. From the example
o
given in the appendix, one can get K = 308 for benzene at 25 C. The overall
liquid phase mass transfer coefficients in the convective ( (K ) ) and
turbulent ( (K ) ) zones are calculated using Equation (2)
L T
4
= 6.51 x 10
1.54 x 10~5 308 x 1.65 x 10
(KL)C = 1.54 x 10
gr-mol
2
cm •sec
1 1
+ = 20.6
-4
(K) 0.096 308 x 3.19 x 10
L T
(Kjm = 0.049
gr-mol
L'T 2
cm -sec
Use of Equation (14) yields the area-averaged overall mass transfer coefficients,
gr-mol
1'= 1.54 x 10~ (0.9) + 0.049 (0.1) = 0.00491
2
cm -sec
46
-------
2
Note: The overall liquid phase mass transfer coefficient given in gr-nol/cm -sec
can be converted to the unit of cm/sec, or I/sec as follows:
density of the wastewater = 1 gr/cm
0.00491 x 78.1
K^ (in cm/sec) = =0.38 cm/sec
or if the depth of the surface impoundment' is 304.8 cm(10 ft),
0.38
K (in I/sec) = = 1.25 x 10 I/sec
304.8
The concentration of benzene in mg/L can be converted to mole
fraction:
20 1 1/78.1
xi = 3~ X 3~ X
10 10 1/18
20 18
= 4.61 x 10
106 78.1
Equation (3) is used to calculate the emission rate for benzene
Q. = 78.1 (0.00491) (0.25 x 4047 x 1Q4) (4.61 x 10~6)
= 17.9 gr/sec
Similar calculations will yield the emission rates for other toxic
components.
2. Estimation of Emission Rates from Landfills
i) Hazardous waste is to be landfilled. The proposed 1/2 acre
landfill will be covered by a soil layer of 30 cm above the hazardous
waste section. The laboratory tests on soil show an average yearly
porosity of 0.16. The vapor in equilibrium with the waste was analyzed
47
-------
for the compounds among the list of carcinogenic evidence using the
head space method. The results of the analysis are:
Concentration in Equilibrium
, Vapor Space PARTIAL PRESSURE
Compound f ^ , . / „ \
(% by volume) (mmHg)
Benzene
Trichloroethylene
Ethylene Dichloride
Estimate the emission rates from the landfill.
Since the air phase resistance is small, Equation (16) can be
rewritten as
q, = — c*
0.96
0.149
0.916
7.3
1.13
6.96
The diffusion coefficient of benzene at 25 C is estimated using
Equation (20)
D. = 1.5 x 10~4 ( )°'5 (273 + 25)1'5 = 0.088 cm2/sec
1 78.1
The concentration of benzene in the vapor in equilibrium with the
waste is calculated from Equation (21)
, 7.3 (78.1)
C. = = 3.07 x 10 gr/cm
1 62363 (298)
HenCS 0.16 (0.088)
Q. = (3.07 x 10 )0.5 (4047 x 10 ) = 0.17 gr/sec
1 30 (1.73)
Similar calculations will give the emission rates for trichloroethylene
and ethylene dichloride.
0. for trichloroethylene = 0.034 gr/sec
0. for ethylene dichloride = 0.18 gr/sec
-------
ii) The proposed landfill in example i above is redesigned to
employ a soil cover with thickness of 60 cm. Polyethylene film
(thickness 0.03 cm) will be placed between the waste and the cover.
Analyses were performed on the waste , instead of its equilibrium
vapor, to determine the composition. The results of the analysis are:
Benzene 3 % by weight
Trichloroethylene 1 % by wt.
Ethylene dichloride 4 % by wt.
Sp. Gr. of the waste : 0.9 gr/cm
The soil tests showed an annual average moisture content of 19 %
at a bulk density of 1.15gr/cm . Evaluate the landfill as before.
The polyethylene film can be converted to equilibrium soil
thickness. The use of Equation (16) to obtain the thickness of
soil corresponding to bulk density of 1.19 gr/cm and a soil moisture
content of 20 % gives
h = 134.6 h.
eq f
= 134.6 (0.03) = 4 cm
The air-filled porosity and total porosity of the soil are
1.15
P = 1 - - 0.19(1.15) = 0.348
a 2.65
1.15
P = 1 - = 0.566
2.65
P-a°/3 / PT = 0.34810/3/0.5662 = 0.0925
*
The partial pressure p. of each component i in equilibrium with
49
-------
the waste can be estimated by
p. = K. P x.
*i i i
where K. is the vapor liquid equilibrium constant (It can be obtained
using the method shown in the appendix ; K. = If. P./J?) , 7T- is tne
activity coefficient of component i (assumed to be 1 in hydrocarbon
mixtures) , P. is the vapor pressure of component i, mmHg, P is the
total pressure, 760 mmHg, x. is the mole fraction of component i in
the waste.
1) benzene (3 % by wt.)
3/78.1
x. = - = 0.0768 mole fr.
1 100/200
p. = 0.0768 (95) = 7.3 mmHg
Similarly
2) trichloroethylene
*
p. = 1.13 mmHg
3) ethylene dichloride
*
p . = 7 mmHg
Hence the quilibrium vapor phase concentrations can be computed as in
Example i:
* -53
C. for benzene = 3.07 x 10 gr/cm
* -63
C. for trichloroethylene = 8 x 10 gr/cm
* -53
C. for ethylene dichloride = 3.73 x 10 gr/cm
Use of Equation (28) yields the estimated emission rates
(3.07x10 5)0.5(4047xl04)
Q. for benzene = 0.088
——— + 1962.8(0.03)
0.0925
= 0.077 gr/sec
50
-------
O. for trichloroethylene = 0.016 gr/sec
0. for ethylene dichloride = 0.084 gr/sec
iii) The wastes in Examples i and ii are to be landfilled after
mixing with municipal garbage. Estimate the emission rates for each
case.
a) Example i with gas generation
The gas generated as result of decomposition of the garbage will
contribute to additional release of hazardous air pollutants. The
emission rate will be estimated from Equation (22) at an average
velocity of generated gas at 1.63 x 10 cm/sec in the landfill (17) .
To use Equation (22) the concentration at the interface, C. , must
be known. An expression for it can be obtained by equating Equation (22)
and Equation (23) , or
*
ci
c = - _ - (43)
10 k .(2.44x10 ) h-V-t
1 + g>1 _ - (exp( — — ) - 1)
The gas-phase mass transfer coefficients required in Equation (43)
are obtained from the relationship given by Equation (11) ,
^H 0 0.335 2?3 + 25 1.005
k . for benzene = ( - ) ( - ) k
S'1 m. 298 g'H2°
18 0.335 gr-mol
= ( ) 2.7x10 1.65x10
78.1 cm -sec
51
-------
Similarly,
-5 2
k . for trichloroethylene = 1.4 x 10 gr-mol/cm -sec
g»i
-5 2
k . for ethylene dichloride = 1.53 x 10 gr-mol/cm -sec
The interface concentrations are
1) benzene
30(1.6xlO~3) (1.73)
= 6.01
V6 0.088(0.16)
3.07X10'5
C. =
10
1.65x10 5(2.44xl04) .. .,
_ . o • UJ- • , >
1 + ( e -1 )
1.63x10
= 1.25 x 10 gr/cm
2) trichloroethylene
D. = 1.5xlO~4(l/131.4)°*5 2981'5 = 0.067
_g •*
C. = 3.24x10 gr/cm
3) ethylene dichloride
D. = 0.078
i
-7 3
C. = 1.63x10 gr/cm
Hence the emission rates estimated from Equation (22) are
1) benzene
Q,- =
3.07xlO~5 - 1.25xlO~7
1.63x10 + 1.63x10 (3.07x10 )
6.01 .
e 1
4
x (4047x10 ) = 1.02 gr/sec
(0.5)
52
-------
2) trichloroethylene
Q. = 0.26 gr/sec
3) ethylene dichloride
0. = 1.22 gr/sec
b) Example ii with gas generation
Equation (29) will be used to estimate the emission rates. As seen
*
above, C. <
-------
3. Estimation of Emission Rates from Land Treatment Facilities.
An oily waste is treated in a one acre landfarm by subsurface injection
2 '
at an application rate of 1.5 #/ft . The depth of injection is 5 (12.7 cm).
The waste analysis shows the presence of benzene in the oil at a level
of 1500 ppm by weight. The porosity of the soil in the cultivation layer
is determined to be 0.35 by test. Estimate the average emission rates.
Other pertinent information:
Average MW of the waste: 200
Sp gr. of the waste : 0.9 gr/cm
Cultivation layer soil bulk density: 0.8 gr/cm
The use of Equation (30) requires the concentration of benzene on the
vapor side of the oil-vapor interface, which can be calculated from
Equation (31).
The initial concentration of benzene in the oil
c. = 150° = 1.35X10"3 gr/cm3
1W° 106/0.9
2
The application rate =1.5 #/ft , or
NT 454 2
-—= 1.5 x = 0.733 gr/cm
A 30.4r
The total depth of penetration
h = h + depth of penetration = 12.7 + 12.7 = 25.4 cm
The mass fraction oil in the film form (Equation (38))
0.5 M,,, 0.5
(25.4)(0.8)
wf = =— ( —— ) = (0.733)
= 0.018
54
-------
From Equation (34), the oil film thickness on soil is (use d = 0.005 cm)
0.005(2.65)(0.018)
z - = 0.000044 cm
° 6(0.9)
From Equation (35) the diffusion path length for the lump is
z = 0.005/2 = 0.0025 cm
o
The vapor pressure of benzene at 25°C is 95 mmHg. If the activity coefficient
of benzene in oil is assumed to be unity for a total pressure of 760 mmHg,
the vapor liquid equilibrium constant K = 0.125 (See Eq.(A-5) in the
appendiK). Using Equation (A-8) in the appendix, one gets
0.125 200
H = = 1.14x10
C 2.44x10 0.9
Also -72 ! -5
D . for benzene in oil = 1x10 cm /sec (D .c< —- • D . = 10 @/u=lcp)
wi wi /• wi
D . = D. £ (recommended by Thibodeaux(26))
ei i
4/3 2
0.088x(0.35) ' = 0.022 cm /sec
a for film (Equation (36)) = 6/0.005 = 1200 cm /cm
s
2 3
a for lump (Equation (37)) = 2.7/0.005 = 540 cm /cm
S
Substitution of these values into Equation (31) yields
1.14xlO~3
C. for film =
6(0.022)(0.000044)
1 + 1.14x10
(1.35xlO~3)
lxlO~5(1200)(645)
= 1.54xlO~6 gr/cm3
Where 2 22 22
h + h h - 2 h = 25.4 + (25.4)(12.7) -2(12.7) = 645 cm
p p s s
55
-------
C. for lump =
1.14 x 10
-3
- 1 + 1.14x10
-3
6(0.022) (0.0025)
lxlO~7(540) (645)"
(1.35xlO~3)
= 1.54 x 10"6 gr/cm3
m
io
(wt. of benzene applied per unit area of landfarm)
1500 _3
= 0.733 x — = 1.1 x 10 gr/cm
io6
The dry-out time is calculated using Equation (33)
25.4 + 12.7
t, for film =
a
2(0.022)(1.54xlO~6)
t, for oil =
a
38.1
2(0.022)(1.54xlO~6)
(l.lxlO~3)(0.5) = S.lxlO5 sec
(3.6 days)
(l.lxlO~3)(0.5) = 3.1xl05 sec
In this case the dry-out times for both film and oil lump are the same,
From Equation (30) the average emission rate during the period of the
dry-out time is
2(0.022) (1.54 x io"6)(4047xl04)
Q. for film layer =
12.7
2(0.022)(3.1xl05)(12.7)(1.54xlO~6)
l.lxlO~3(0.5)
1/2
= 0.11 gr/sec
Q. for oil layer =0.11 gr/sec
The average emission rate is
0.11 + 0.11 = 0.22 gr/sec
56
-------
4. Dispersion Modeling-Screening Technique
A disposal facility (1/2 acre) is emitting volatile hazardous
chemicals at the following rates:
Compound Emission Rate(gr/sec)
benzene 0.17
trichloroethylene 0.034
ethylene dichloride 0.18
Evaluate the impact of the facility on ambient air quality.
In order to utilize the screening technique for estimating the
impact, the following data are obtained from the permit applicant:
Distance from the facility to the downwind public: L=1000 m
Frequency that wind blows from the sector of interest: v> = 0.25
Average annual temperature: 25 C
Stability Class: D
Annual average wind speed: 5 m/sec
At L = 1000 m.S D stability, O*~ = 32 m.
Distance from virtual point to the disposal facility (Equation (41))
(0.5x4047xlQ4)0'5 . , 22.5, ,. ,„ ,,,, .
L = cot( ) = 11300 cm (113 m)
2 2
The width of the facility
S = (0.5x4047xl04)°*5
= 4500 cm (45 m)
Since S ^ 400 m, the screening technique can be used. The virtual
downwind distance is
L = 113 + 1000 = 1113 m
57
-------
The net downwind concentration is obtained from Equation (40)
1) benzene
16 ' 2(0.17)
(0.25) = 4.9x10 gr/ in (=0.49 /agr/iti )
271(1113) J27T (32) (5)
2) trichlorobenzene
% = 1x10 gr/m (0.1
3) ethylene dichloride
f. = S.lxlo"7 gr/m3 (0.51
The background concentration of each compound should be added to the
results above to obtain the downwind concentrations. The estimated annual
average of the downwind concentration would be higher than the net concen-
tration given above if the the background concentration is taken into
account.
At an assumed lifetime cancer risk of 10 the maximum ambient levels
of each compound not allowed to exceed are obtained from Equation (42)
1) benzene
Cmi- = 5" = °-21
mi . _ , -5
4.8x10
2) trichloroethylene
3) ethylene dichloride
10"5
C . = =0.83 >gr/m
mi n _ , -5 /^(
1.2x10
To account for the additive health effect of carcinogens, the sum of
normalized permissible maximum concentrations (SNPMC) is determined
58
-------
0.49 0.1 0.51
SNPMC = + + =2.99
0.21 2.4 0.83
The maximum allowable downwind concentrations of each compound at 10 risk
are now:
1) benzene
0.21
= 0.07yUgr/m
2.99
2) trichloroethylene 0.1/Ogr/m
3) ethylene dichloride 0.51^ugr/m
In order to meet these concentrations, the emission rates of benzene from
the disposal facility should be reduced to
0.07
0.17 x = 0.024 gr/sec
0.49
Or other adjustments on the emission rate of each component can be made
to meet SNPMC £ 1. For example, if the allowable downwind concentration
of benzene is doubled while that of ethylene dichloride is reduced by a
factor 2, the allowable concentration should be
1) benzene 0.14 ^ugr/m
2) trichloroethylene 0.1 ^wgr/m
3) ethylene dichloride 0.25 jaq-r/m
0.14 0.1 0.25
SNPMC = + + =* 1
- 0.21 2.4 0.83
Hence the emission rate of each compound should not exceed
0 14
1) benzene 0.17 x -^TX =0.05 gr/sec
u • 41 y
2) trichlorobenzene 0.034 gr/sec
3) ethylene dichloride 0.18x :rV, =0.09 gr/sec
59
-------
5. Consideration of Other Health Criteria
Ambient air monitors are installed to monitor the effect of a treat-
ment facility on the ambient air concentration of cyanides.. The treatment
facility is a 0.25 acre agitated lagoon. The average concentration of
cyanides in the form of hydrogen cyanide in the lagoon is about 2000 mg/L.
Estimate the impact of the facility on the downwind monitor when the
average wind velocity is 5 m/s (stability class = D). Additional
information obtained is:
Background cyanide concentration in the ambient air = 0.1 /xgr/m .
Distance of lagoon to the downwind monitor = 200 m.
Effective zone of turbulence = 5 %.
Average temperature = 25 C.
Calculations similar to Example 1 can be used to estimate the
overall mass transfer coefficient(MW of HCN = 27).
i) Convective zone
a) Liquid Phase
32 0.5 gr-mol
fcL i = ( — ) x 2.4xlO~b = 2.6x10
' 27 cm -sec
b) Gas Phase
18 0.335 gr-mol
k . = ( —) x 2.7x10 = 2.36x10 •
27 cm2-sec
ii) Agitated zone
a) Liquid Phase
32 0.25 gr-mol
= 0>12S - -
27 cm • sec
60
-------
b) Gas Phase
18 0.25 . . gr-mol
. = ( — ) x 4.6x10" = 4.16x10
> 27 cm2-sec
The vapor-liquid equilibrium constant, K. , for HCN in aqueous solution
is estimated by
K. =
The vapor pressure of HCN at 25°C = 735 nraiHg from a handbook, and ^ = 1
will be used for the dilute concentration.
(1) (735)
K. = - = 0.967
1 760
The overall liquid phase mass transfer coefficients in the convective
((KT) ) and turbulent ((KT)T) zones are obtained from Equation (2)
l_i C LI
11 * 4
- = - + - = 8.23x10
^iPc 2.6xlO"5 0. 967x2. 36xlO~5
(K.I = 1.22x10
-5
gr-mol
L c 7
cm -sec
3
= 2.49x10
(K.)T 0.125 0.967x4.16xlO"4
Li 1
(KL)T = 4.01x10
_4 gr-mol
cm -sec
The average mass transfer coefficient for the entire lagoon is obtained
as follows:
61
-------
K. = 1.22xlO"5 (0.95) + 4.01xlO"4(0.05)
LJ
, 3.16X10'5
cm- sec
The concentration of HCN in the aqueous solution is converted to mole
fraction,
2000 1/27 _3
x. = ——— x = 1.33x10 mole fraction
1 106 1/18
The emission rate of HCN from the treatment lagoon is estimated from
Equation (3)
Q. = 27(3.16xlO~5)(0.25x4047xl04)(1.33xlO~3)
= 11.5 gr/sec.
Dispersion modeling will be used to estimate the impact on the
downwind monitor. As in Example 4, the width of the facility is
S = (0.25 x 4047 x 104)0'5 = 3180 cm (31.8 m)
Since S < 80 m where 80 m is 40 % of the 200 m, the screening technique
can be used. The distance from virtual point to the disposal facility is
31.8
L = (5.03) = 80 m
2
The virtual downwind distance is
Ly = 80 + 200 = 280 m.
The net concentration impacting the downwind monitor is (Equation (40))
62
-------
(i) = 2xio- (=2000
21V (280) n (8. 5) (5) m3 in
When thw wind is blowing toward the downwind monitor, the concentration
at the downwind monitor is estimated to be
2000 + 0.1 = 2000
m3
The impact of the facility on the downwind population located at say
500 m from the facility can be predicted similarly. If the frequency of
wind blowing toward the population is 0.25, the net concentration is
X - - -- .52 - (o.25) = 1.08X10'4
27V (580) /2~K (18. 6) (5) m
(=108 — — = 98 ppb )
m
To evaluate whether or not this concentration is within the acceptable
level recommended in the other criteria goals, the drinking water standard
obtained from analysis of toxic effects data, which is protective of human
health against the ingestion of contaminated water, is used. This
standard is 200 yMg/L. Based on daily consumption of 2 L of water and 20 m
of air, the acceptable ambient air concentration of cyanide is calculated
as
200 £21 2 L
L yugr
= 33.3 ——- (=30.1 ppb by volume)
__ 3 ., .. m'
20 m x 0.6
where it is assumed that only 60 % of the inhaled cyanide is absorbed.
The average concentration impacting the population is higher than the
acceptable value. The cyanide emission from the treatment facility is
adversely impacting the downwind public.
63
-------
NOMENCLATURE
2
A : surface area of disposal facility, cm
a : interfacial area per unit volume of soil for the oily waste, cm /cm
s
a : surface area per unit volume of surface impoundment, ft
C. , C.T : concentration of gas and liquid phases at the gas liquid
ig iL
interface in the pore, gr/cm
C. : initial concentration of component i in the landfarming waste, gr/cm
iwo
C. : concentration of component i at the soil-air interface, gr/cm
c
ioo : concentration of component i in the air far away from the soil-air
interface, gr/cm
*
C. : concentration of component i in the air space at the immediate vicinity
of the waste(or in equilibrium with the waste), gr/cm
C : maximum permissible concentration, /Xgr/m
m '
D : diffusion coefficient, cm /sec (Note: D. means the diffusion
1'H2°
coefficient of component i in water)
2
D . : effective diffusivity of component i in the air-filled soil pore, cm /sec
D . : diffusivity of component i in the waste, cm /sec
V/1
d : diameter of aerator turbine or impeller, ft
d : effective diameter of quiscent area of surface impoundment, m
d : soil clump diameter, cm
P
2
g : gravitational or conversion constant, ft/sec
H : Henry's law constant, atm/mol/m
H : Henry's law constant in concentration (C. = H C. )
c ig c iL
H : effective depth of surface impoundment, ft
h : depth of soil cover, cm
h : soil equivalent to polyethylene film
h : polyethylene film thickness, cm
64
-------
h : depth of penetration by soil contamination below the surface, cm
P
.h : depth of subsurface injection, cm
J : oxygen transfer rating of surface aerator, normally about 3 Ib 0 /hr-hp
K.: vapor-liquid equilibrium constant
1C : overall mass transfer coefficient, gr-mol/cm -sec
2
k , k : gas and liquid phase mass transfer coefficients, resp., gr-mol/cm 'sec
g L
k . : gas phase mass transfer coefficient of component i in air,
gr-mol/cm .sec
k_ . : liquid phase mass transfer coefficient of component i a disposal
L,l
2
facility, gr-mol/cm -sec
L : distance from center of a disposal facility to property line, m
i
L : virtual downwind distance to receptor (L + L), m
i
L : distance from virtual point to center of a disposal facility, m
NL, : amount of waste application, gr
m. : initial amount of component i placed for landfarming, gr
MW : molecular weight
N : Froude number, d u /g
r R
N : power number, P g/ P d to
N : gas Reynolds number, P d u> /g
R s »g
N^_ : gas Schmidt number, n g/ O D.
SC ^ /*g ^' ) g i,air
p : partial pressure, mmHg
P : total pressure, mmHg
P : pure component vapor pressure, mmHg
P : air-filled porosity, cm /cm
31
P : total porosity, cm /cm
POWR : total power input to aerators in the aerated surface impoundment, Hp
65
-------
P : power to impeller, ft-lb force/sec
0 : rate of emissions from a disposal facility, gr/sec
2
q : emission rate per unit area of the area source, gr/cm -sec
R : gas constant, cm •mmHg/ K-mol
*
Re : roughness Reynolds number (See Reference 4 for the expression)
Ru : unit risk
S : width of area source, m
T : temperature, K
t : time, sec
t : dry-out time, sec
U : surface velocity, ft/sec, normally 0.035 x wind speed(ft/sec) for
natural surface, ft/sec, and 0.1 ft/sec for outside of region of
effect of aerators in the biological treatment.
u : wind speed, m/sec
U . : wind speed, m/hr
air
V : volume of surface impoundment, ft
V : average gas velocity in the soil pore in the upwind direction, cm/sec
w : soil water content, gr/gr
w : fraction of oil in film form on soil
x : liquid phase mole fraction
y : gas phase mole fraction
z : oil layer diffusion length, cm
66
-------
Greek Letter
o< : oxygen transfer correction factor
2
LL : viscosity, lb-f-sec/ft
X(chi) : net ambient concentration of a hazardous substance originated
from disposal facility emissions, gr/m
0. : standard deviation of the concentration distribution in the vertical
direction, m
: relative frequency of occurrence from stability wind rose
9 : temperature, °C
f : activity coefficient
j> : density, lb/ft3
P : density, gr/cm
u» : rotational speed of turbine impeller, rad./sec
Subscript
air : air
c : convective
HO : water
g : gas
i : hazardous component i
j : hazardous component j
I
L : liquid
0 : oxygen
p : soil particle
T : turbulent
Tol : toluene
w : waste
67
-------
VII.REFERENCES
1. The Alkyl Benzenes, National Academy Press, Washington, D.C.
1980.
2. Busse, A.D., J.R. Zimmerman, User's Guide for the
Climatological Dispersion Model, EPA-R4-73-024, U.S.
EPA, Research Triangle Park, North Carolina 27711,
December 1973.
3. Climatic Atlas of the United States, U.S. Dept. of
Commerce, NOAA, NCC, Federal Bldgl, Asheville,
North Carolina 28801, 1974.
4. Cohen, Y., W. Cocchlo, and D. MacKay, "Laboratory Study
of Liquid-Phase Controlled Volatilization Rates in Presence
of Wind Waves," E.S. & T., No.5, p.553 (1978)
5. Edited by Source Receptor Analysis Branch, U.S. EPA, RTP.
6. EPA Water Quality Criteria Documents, October 1980.
7. Freeman, R.A., "Stripping of Hazardous Chemicals from Surface
Aerated Waste Treatment Basins," Monsanto Co., 1978.
8. Health Assessment Document for Cadmium, U.S. EPA, RTP,
N.C., 1979.
9. Hwang, S.T., "Treatability of Organic Priority Pollutants
by Steam Stripping," Water, 1980.
10. Hwang, S.T., "Tray & Packing Efficiencies at Extreme
Dilution," Vol VI, Recent Advances in Separation Processes,
CRC, in press.
11. MacKay, D., R.S. Matsugu, "Evaporation Rates of Liquid
Hydrocarbon Spills on Land and Water, " Can. J. Chem. Eng.,
5JU 434 (1973).
12. McGaughy R., Assistant Director, Carcinogen Assssment
Group, EPA.
13. Owens, M., R.W. Edwards, J.W. Gibbs, "Some Reaeration
Studies in Streams," Inter. J. Air Water Pollu., 8,
496 (1964).
14. Reinhart, J.R., "Gas-Side Mass-Transfer Coefficient and
Interfacial Phenomena of Flat Bladed Surface Agitators,"
University of Arkansas, Ph.D. Thesis, 1977.
15. Smith, J.H., D.C. Bomberger, Jr., and D.L. Haynes, "Pre-
diction of the Volatiliztion Rates of High Volatility
Chemicals from Natural Water Bodies," SRI Report,
August, 1979.
68
-------
16. Thibodeaux, L.J., "Air Stripping of Organics from
Wastewater: A Compendium," Proceedings of the Second
National Conference on Complete Water Use, Chicago,
Illinois, May 4-8, 1978.
17. Thibodeaux, L.J., "Estimating The Air Emmissions of
Chemicals From Hazardous Waste Landfills," for Publication
in J. of Hazardous Materials, July 31, 1980.
18. Thibodeaux, L.J., Chemodynamics, John Wiley & Sons, Inc.,
1979.
19. Turner, D.B., Workbook of Atmospheric Dispersion Estimates,
EPA, 1970.
20. OAQPS Guidelines Series, Guideline on Air Quality Models,
EPA-45012-78-027, April 1978.
21. Colection and Analysis of Purgeable Organics Emitted from
Wastewater Treatment Plants, EPA-600/2-80-017, Mar, 1980,
EPA, Cincinnati, Ohio.
22. Wastewater Engineering, Metcalf & Eddy Inc., McGraw-Hill, 1972.
23. Kyosai, Shunsoku, Desorption of Volatile Priority Pollutants in
Sewers, Japan Ministry of Construction, July 1980.
24. Wilke, C.R., and Chang P., Correlation of Diffusion
Coefficients in Dilute Solutions, A.I.Ch.E. J.,
Vol. 1, 264(1955).
25. Farmer, W.J. et al., "Land Disposal of Hexachlorobenzene Wastes,"
EPA-600/2-80-119, EPA, Cincinnati, Ohio, August 1974.
26. Thibodeaux, L.J., Private Communication, December 1980.
27. Farmer, W.J., "Volatilization Losses of Pesticides from Soils,"
EPA-660/2-74-054, August, 1974.
28. "Atmospheric Hydrocarbon Concentrations, June-September, 1976",
State of California Air Resources Board, January 1977.
29. Project Summary, Air Pollution Sampling and Monitoring at
Hazardous Waste Facilities, IIT Research Institute, 1980.
69
-------
APPENDICES
70
-------
Appendix A
Methods for Determining K-values
1. Prom Experimental Data:
The liquid sample taken from a surface impoundment can be
equilibrated in a head space, and the liquid and vapor phases
can be analyzed for concentrations of each hazardous component.
The K-value is
K = yi/Xi (A-1)
where K is the K-value or the vapor-liquid equilibrium constant,
y^ is the mole fraction of hazardous component i in the vapor
phase, and x^ is the mole fraction of hazardous component i in
the liquid phase. When the partial pressureCp^, mmHg) of component
i in the vapor phase is measured, y^^ = PJ/P where P is the total
pressure, mmHg.
The K-values determined this way are valid at the applicable
liquid concentrations and temperature. If Henry's or Raoult's laws
hold for the liquid mixtures, the Z-value could be used over a range
of concentrations.
2. Prom Henry's Law Constant:
Henry's law often holds for aqueous solutions of sparingly
soluble organic compounds. Examples are benzene, chloroform, etc.
in wastewater. Henry's law constants are expressed in several
different units. A collection of Henry's law constants in
atm/(mol/nr ) is attached herewith(Table A-1). Other Henry's law
constants may be found in a handbook. The Z-value can be determined
by one of the following ways:
at
-
mol/n
atm r
H( - -) x 106
P(atm) M\iL
3V . .
71
(A-2)
-------
atm Ib-mol
H("} c
Z = - * - - (A-3)
nr atm. _ Ib-mol
R( - 5- ) T(°Z)
mol °K
where P is the total pressure, atm, MWaVf ±fl the average moiecular
weight of solution, R is the gas constant(8.2x10"^ mol&og )• T
is the temperature, °Z , C,.cmid ^s ^e ^^u^d density''. Ib-mol
/ft5 , and (3 _ is the gas density, Ib-mol/f.t .
gas
Example
Henry's law constant for benzene in water is 5.55 x 10"
atm/(mol/m5) at 25 °C. Calculate the K-vakie by Equations (A-2)
and (A-3).
1) Equation (A-2)
5.55 x 10~3 x 106
K = = 308.3
(1) (18)
2) Equation (A-3)
Cliquid = 62-4/18 = 3.467 lb-mol/ft5
Cgas - M- - 10.73(460.77) = °'°0255 1^mol/"3
5.55 x 10~3 3.467
K = = 308.5
8.2 x 10"5(298) 0.00255
3. From Raoult's Law
Raoult's law fiften holds for hydrocarbon mixtures. The K-value
can be calculated by
P,
Z = —i (A-4)
P
where P. is the vapor pressure of a hazardous component at a temp-
erature of concern, mmHg, and P is the total pressure.
72
-------
3. Other cases:
When Henry's law constants are not available or the RaouJt's
law does not hold for the mixture, the K-value can be obtained by
i i / \
1 P
where y. is the activity coefficient, Pi is the vapor pressure of
a hazardous component, mmHg, P is the total pressure, mmHg. There
are methods of determining the activity coefficients for aqueous
solutions and hydrocarbon mixtures. These methods are not discussed
here. If y is close to unity as in the case of hydrocarbon mixtures,
Equation (A-5) becomes Raoult's law. If fr" is not close unity but
remains constant at low concentrations, Equation (A-5) becomes
Henry's law.
4. Henry's law constant in concentration:
• The Henry's law constant (H ) expressed in concentration unit
C
occurs in problems involving landfarming. The constant is related
by • '
C.g = H-c C.L (A-6)
where C. (gr/cm ) and C., (gr/cm ) are concentrations on the
gas and liquid side of the oil-air interface in the soil pore
spaces. H is related to H or K as follows:
atm gr-mol 10
H = H ( ) C ( ) (A-7)
'Z O 'Z
gr-mol/m c nr P(atm)
and
gr-mol MW_V
Hc . K 0
where C is the molar density of vapor(1/2.44x10 gr-mol/cm ),
MW is the average molecular weight of the oil, and fw is the
density of the oil, gr/cm .
73
-------
Table A-1. Henry's Law
Compound
Acenaphthene
Benzene
Carbon tetrachlorlde
298
298
298
Molecular
Weight
g/mol
154.2
78.1
153.8
H, m3 atm/mol x 10"3
Calculated Experimental
5.48
28.6
0.241
5.55
30.2
Chlorobenzene
1,2,4-Tnchlorobenzene
Hexachlorobenzene
298
298
112.6
181.5
284.8
3.7(1
2.32
3.93
1.42
1.70
1,2-D1chloroethane
1,1,1-THchloroethane
Hexachloroethane
298
298
295
99.0
133.4
236.7
1.35
4.08
1.10
4.92
9.85
1,1-Dlchloroethane
Chlorofora
1,2-Dlchlorobenzene
293
298
298
99.0
119.2
147.0
5.54
3.23
2.00
5.45
3.39
1.94
1,3-D1chlorobc»nzene
l,4-D1chlorobenzene
1,1-Dlchloroethylene
298
298
293
147.0
147.0
97.0
2.96
15.1
2.63
2.72
15.0
1,2-trans-01chloroethylene 293 96.9
1,2-D1chloropropane 293 113.0
1,3-Dlchloropropylene 298 111.0
4.05
2.75
1.35
5; 32
2.82
3.55
Ethyl benzene
Methylene chloride
Bromoform
298
298
298
106.2
G4.9
252.8
6.44
3,04
0.595
6.44
3.19
0.532
-------
Molecular ," ,
^ Weight H, mj atm/mol x 10"J
Compound K g/mol Calculated Experimental
Bromodlchloromethane •- 163.8 - - 2.12
THchlorofluoromethane 290 137.4 104 58.3
01 bromochlorome thane - 168.8 fr — 0.783
llexachlorobutadlene .293.. 260.8 25.7 10.3
Hexachlorocyclopentadlene 298 272.7 36.2 16.4
Nitrobenzene 298 123.1 0.023 0.024
4,6-D1n1tro-o-creso1 - 198.1 - - 0.0014
Phenol 298 94.1 - - 0.0013
Acenaphthylene 298 152.2 i - - ' 0.114
i
I
Fluorene 298 116.2 - - 0.117
Tetrachloroethylene 298 165.8 28.5 28.7
Toluene 298 92.1 6.44 5.93
Trlchloroethylene 298 131.5 11.7 11.7
Aldrln 293 364.9 - - 0.496
Dleldrln 298 380.9 - - 0.058
Chlordane 298- 409.8 - - 0.048
lleptachlor 298 373.4 - - 1.48
Meptachlor epoxide 298 389.3 - - 0.032
Arochlor 1254 290 328.4 - - 8.37
Toxaphene 298 413.9 - - . 4>.89
-------
APPENDIX B
DRAFT
A MODEL FOR VOLATILE CHEMICAL EMISSIONS
TO AIR FROM LANDFARMING OF OILY WASTES
by
L. J. Thibodeaux, U A, Fayetteville, AR
and
S. T. Hwang EPA, Washington, D C
Nov. 22, 1980
76
-------
An overview of petroleum industry landfarming operations for
disposal and treatment of organic waste was given by Knowltcn and
Rucker (1) . The land is cultivated to provide a continuing supply of
oxygen. Water and fertilizer are added, if needed. The end products
of landfarming are carbon dioxide, water, and increased humus
content of the soil. The most common wastes treated within the
petroleum industry are oily sludges and biosolids.
Typically a heavy oily sludge is spread several inches thick.
The soil is then cultivated at frequent intervals for about two
-months. Vacuum trucks apply free flowing oil waste directly to the
•
land. Heavy, solidified wastes are distributed over the landfarm
from dump trucks and spread with a bulldozer. Cultivation, of the
waste into the soil is done with various kinds of farm implements.
Application rates vary widely from 200 to more than 600 barrels
per acre per year. The application thickness can vary from several
inches to a thin layer .of a fraction of an inch. Avoiding clumps
and spreading as a uniform layer as possible makes subsequent
cultivation most effective. The cultivation depth is usually the
top six inches of soil. Refinery waste suitable for landfarming
are: tank cleanings with 20 to 50 percent oil, separator cleanings
with 10 to 20 percent oil, other cleanings with approximately 10 percent
oil, a wast'ewater treatment plant sludge zero % and filter clays
with approximately 8 percent oil.
To evaluate the extent of atmospheric emission of volatile
chemicals from landfarming oprations transport mechanisms from the
soil surface and the soil pore spaces must be considered. During
the time the oily waste is placed upon the soil and cultivated,
77
-------
vaporization can occur directly from the surface. The exposed
liquid or semi-solid contains volatile component i of mole fraction
*
x . The vapor concentration, ci Of this chemical in equilibrium
with the oily waste is: _ 0
' . o. P. MW.
X—Hrs-1
where MML is molecular weight of the volatile chemical, PI is pure
component vapor pressure, If. is the liquid phase activity coefficient,
R is the gas constant and T is absolute temperature. The flux
rate from the surface is:
*
q. = k . C. MW. (? \
Hi g,i i i \£l
where q. . is in gr/cm -s, k .is the gas phase mass transfer coefficient.
2*3
in gr-mol/cm -sec and C. is in gr/cm . The rate equation assumes no mass
transfer resistance in the oil phase. This assumption will be
* •
valid only for a very short period of time, as the volatile chemical
species is lost from the surface molecules need to be replaced from
the lower liquid layers and hence the resistance increases. Eq.
(2) however, provides an estimate of the maximum volatilization
rate. See Thibodeaux. (2) for the development of a model for the
evaporation of liquid chemicals spilled or otherwise placed on
land.
Soil Pore-space Evaporation and Diffusion Model
A model, for the vaporization and movement of pure liquid
spilled on a dry soil has been presented by Thibodeaux (3)- The
pure liquid is assumed to soak into the dry soil and contaminates
it to a depth h • The liquid coats the pore walls and particle junction
P
sites. The chemical evaporates from the interstitial soil surfaces,
78
-------
and the vapor diffuses through the pores upward toward the air-soil
interface. In a very short time a hypothetical "dry" zone develps
near the surface, and liquid vaporization occurs from the plane formed
between this zone and the remaining "wet" zone. As vaporization
occurs the dry zone increases in depth and the wet zone decreases.
It is further assumed that the soil column is isothermal, that no
vertical liquid movement occurs by capillary action, no adsorption
on soil particles, and no biochemical oxidation. Equations are
developed for the evaporation life time and flux rate. This paper
extends the model to the evaporization of chemical species from oil
waste mixture in .land farm-type treatment type operations.
Oily wastes are placed on the soil surface or injected below
the surface. When placed on the surface the waste is then cultivated
into the soil column to the depth of the plow slice h (cm). Subsurface
injection is'done to a depth below the surface h_ (cm), where h < h .
s - p
Figure 1 shows these depths and the relative locations of the "wet"
and "dry" zones for volatile speciesi in the oily waste. The
following is a general model which applies to either the surface
application or subsurface injection method.
W/A/C)
Figure 1 Evaporation and Diffusion from landfarra 'Soil
79
-------
Species i in the oily waste mixture exerts a concentration c
19
(g/cm3) while in the wet zone the evaporation diffusion life time t.
for initial mass of i m. (g) incorporated into the zone h - h
S
s
10
t. = (h + h ) m. /(2 D . A C. ) (3)
d p s 10 ei ig
where Dei(cm2/s) is the effective diffusivity of i in the air-filled
soil pore species and A(cm2) is the surface area over which oily
waste is applied (i.e., mio/A is the application rate). The flux
rate, q.(g/cm2.s) through the wet-dry interface is
q. = D . C. / fh2 + 2 D . t A (h - h ) C. /m. 1 (4)
^i ei ig L s ei p s ig 10 J
where t is the time after application. For the surface application
case h =o in equations "5 and 4. In both cases t £ td .
The effective wet zone pore space concentration of species, i, c.
must reflect the diffusion-resistance within the oil phase
and within the airfilled pore spaces. The rate i moves through the
oil phase in the wet zone is equal to the rate i moves from the top
of the wet zone to the surface. This equality is:
a A y(D ./z )(C. - C.T) = (D . A/(h - y))(C. - 0) (5)
s wi o iwo iL ei p ig
where a (cm2/cm3) is the interfacial area per unit volume of soil
S
for the oily waste, Dwi (cm2/s) is the effective diffusivity of i
in the Oil. z (cm) is the oil layer diffusion length, and C. (gr/cm ) is the
O . IWO
initial concentration of i in the oil. For equilibrium at the interface
C. = H C._ (6)
ig c iL
where c (g/cm^) and c (g/cm3) are. concentrations on either side
of the interface, and HC (cm^ oil/cm^ air) is the Henrys law constant
in concentration form... Combining Equations 5 and 6 yields;
c
c. =
19
D ZQ
C. (7)
iwo
80
-------
where f(y) = y (h - y) accounts for the lenthening dry zone.
The average value of this function during the evaporation diffusion
process is
f(y) = (h2 + h h - 2 h'2)/6 (8)
p p s s
and should be used to estimate f(y) in Equation (7). For small
values of the oil layer coating the soil particles, z , or large
o
interfacial area, a , Equation 7 reduces to c. = H c and the
1<5 ^ ^k
process is air pore space diffusion controlled.
Oil mass distribution within the soil column will be assumed
to be bidispersed . One fraction of the mass, f mio , is in "film"
form. This fraction, a thin film that coats the soil clumps, is in
direct contact with the air filled pore spaces and is readily
available for transport to the surface. The remaining mass is in
"lump" form and is (l-f )raio- The lump fraction is contained
in the dead-end air-filled pore spaces or in the spaces between
soil particles. The lumps are relatively large and have low
interfacial area so that molecules ofi have a more tortu path
to the air-filled pore spaces that connect with the surface. Figure
2 shows the bidispersed nature of oil in a soil column. Since
approximately half of the pore spaces in soil are air filled (4),
f=0.5 seems reasonable as a first approximation.
Air/Soil interface
Soil particle
Air pore space
Oil lumps
Figure 2. Bidispersion Oil
on Soil Column.
ft1
-------
Soil with a high degree of organic matter is usually found to
have a structure classed as spheroidal clumps (4)• These clumps
are reported to have diameters up to one half inch. By using spheres
and associations of spheres it is possible to construct simple
geometric models and estimate the oil phase diffusion path,
z0(cm), and the interfacial area per volume, ag (cm^/cin3), for the
film and lump oil forms.
Soil
clumns
Oil lump
Oil film
a) film form b) lump form
Figure 3. Sphere Models for Oil Forms in Soil.
Figure 3 shows simple sphere models for oil forms in the soil column
For oil in film form the thickness or diffusion path length,
z ( cm) , is
o
z = d P w./ 6 P
o p i p f I w
(9)
where d (cm) is soil clump diameter, j> (g/cm^) is soil clump
density, w is the fraction of oil in film form on the soil, and
p (g/cm3) is the oil density. The interfacial area for the film
• w
form is;
= 6/d
p
(10)
82
-------
For oil in lump form the mass will be assumed to be trapped in the
space formed by eight spheres in an orthogonal arrangement. Figure 3
shows a two-dimensional view of the lump form model. For diffusion
path length for the lump is:
and the a for the lump is:
S
a = 2.70/d (12)
s p . •
In the case of bidispersed oil the model equations developed
for evaporation and diffusion (i.e., Equations 3,4,7 and s ) apply
for each form. Because of relative diffusion path lengths and
interfaclal areas the dry zone for the film mass fraction will grow-
faster than that for the lump mass fraction. In other words the
life-time for dry-out will be shorter for the film form. The
volatile component i in the film form will contribute to initial
high flu.x rates of relative short duration. This is because z is
0 .. ' o
small and ag is large. Volatile component i in lump form will have
lower flux rates and larger life- time. This is due to large z and
lower as values. The net result is high initial flux rates
contributed to by both oil forms. The average flux rate during
time period t is twice the point rate value obtained by Equation 4*
The point rate falls as the square root of time. The film form
does not contribute to the flux when t > tf . The flux continues to
fall until t= t_ (i.e. , lumps lif.e-time) . The air filled pore spaces
L
still contain vapor of i and this remaining small quantity moves to
the surface by vapor diffusion. Thibodeaux (3) presents a model
rate edquation that is exponential in form for this period. The
time for depleting the soil air filled pore spaces of 90$ of the
-------
remaining vapor is
*0.1 » O..794i4/Dei (13)
The model is capable of handling the emission of multiple
volatile components from the oil. This can be done by treating
each component individually using the model equations and assuming
no interaction or interference between species. The total flu x
rate is the sum of the individual species flux rates. The total
flux for surface application should decrease as /"t" just as for
individual species.
. The re-cultivation of the waste treatment area sometime after
the first application may result in a temporary increase in the
vapor emission rate. If the area is plowed after a period of time
t (s) and this period is less than the life-time of species in
either film or lump form, the remaining masses in the wet zones are
uniformly redistributed in the plow slice. The mass of i, m.- (g) ,
volatilized during the period t is;
m - = 2 A t q - (14)
it ^it
where q-Cg/cm^.s) the flux rate of species! at t=t . The remaining
mass,m. -m - , is now used in the model equations to compute the
flux rates after plowing. The remaining mass contains the initial
film and lump from distribution.
Preliminary results from laboratory simulation experiments of
landfarming volatile emissions(5) suggests that the model is
qualitatively reasonable. Equation 4 shows that concentration in
the air above an area, treated by surface application then cultivated,
should fall with the /"t. Emission data where concentration in the
air from a laboratory simulation is measured with time should have
84
-------
100011
9
8
7
6
5
. 4
O
z
LU
O
O
O-,.
£2
1
9
8
•i
5
4
"16!
Run«*1
Run** 2
Run" 3
Slope = -0.58
Slope = -0.838
Slope = -0.56
j Run«4
! Run*»5
] Run*6
Slope =-0.47
j Slope = -0.618
! Slope--0.48 ',
Run«8
'Slope = -1.3
2 3) 4 561789,1; 2 3, 4567891
3 4 5 6|7 891
2 '3- .4. !5:,6i7|8i9i1
,2 3 4 5:67,891
— I
T I I T I
I
I I I I MM
I I I I M I II
I I I I I I III
I I I I I M I
•
a
••
in
oo
100
TIME MINUTES
FIGURE 4. CONC. vsTIME
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a slope of -0.5- Figure 4 shows the analyzis of some preliminary
data for eight experiments. The average slope is -0.68 with a
range of -0.39 to -1.3.
86
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LITERATURE CITED
1. Knowlt.on, H.E. and J. E. Rucker, "An Overview of Petroleum
Industry Use of Landfarming", 71st An. Mtg., AICKE, Miami Beach,
November 16, 1978. .
2. Thibodeaux, L. 0., Chemodynamics, Wiley, NY (1979) p.319-325.
3. Thibodeaux, L.J., ibid, p. 333-339.
4- Brady, N.C. , The Nature and Properties of Soils, 8th Ed.,
Mcmillan Pub. Co., New York (1974), p. 67-
5. Rucker, E.J., Progress Report: Air Emissions from Landtreatment
of Oily Sludges, API,. Washington, DC, October 10, 1980.
87
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