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

-------
                           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

-------
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

-------
 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

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           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

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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

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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

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                       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

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APPENDICES
    70

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                           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

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      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

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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

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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

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      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

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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

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     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

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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

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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

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      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

-------
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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