United States
                    Environmental Protection
                    Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
                    Research and Development
EPA/600/S2-87/046 Sept. 1987
&EPA         Project  Summary
                    Potential Emissions of Hazardous
                    Organic  Compounds from Sewage
                    Sludge  Incineration

                    Sueann Mazer, Philip H. Taylor, and Barry Dellinger
                      Very little field data is available con-
                    cerning organic emissions from sewage
                    sludge incinerators. This is of particular
                    concern because hydrophobic hazardous
                    organic compounds,  such as certain
                    pesticides, polynuclear aromatic hydro-
                    carbons, and polychlorinated biphenyls,
                    have been shown to partition onto the
                    sludge during the wastewater treatment
                    process. The environmental fate of these
                    compounds during sewage sludge in-
                    cineration is largely unknown.
                      Laboratory thermal  decomposition
                    studies were undertaken to evaluate
                    potential organic emissions from sew-
                    age sludge incinerators. Precisely con-
                    trolled thermal decomposition experi-
                    ments were conducted on sludge spiked
                    with mixtures  of hazardous  organic
                    compounds, on the mixtures  of pure
                    compounds in absence of sludge, and
                    on unspiked sludge. These experiments
                    were conducted using laboratory flow-
                    reactor systems interfaced with a gas
                    chromatograph or  gas chromatograph-
                    mass spectrometer for product analysis.
                    Issues which were addressed included
                    the effect of the sludge matrix on the
                    thermal decomposition behavior of the
                    hazardous sludge contaminants; poten-
                    tial emissions from incineration of con-
                    taminated and  uncontaminated sludge;
                    the relative contributions of the biomass
                    and the contaminants to mass emissions
                    in sewage sludge incineration; and
                    potential emissions due to volatilization
                    of organics from sludge in the drying
                    zones of multiple hearth incinerators.
                      In addition  to the global thermal
                    decomposition studies describe above,
                    elementary reaction kinetic studies were
                    conducted using a laser photolysis/
laser-induced fluorescence technique.
To permit an in-depth understanding of
some of the fundamental chemistry oc-
curring in sewage sludge incinerators,
the reaction rates of OH radicals with
model chlorinated hydrocarbons were
measured.
  This Project Summary was developed
by EPA's Water Engineering Research
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
Is fully documented In a separate report
of the same title (see Project Report
ordering Information at back).

Introduction
  While incineration has been  used to
dispose of sewage sludge since  the
1930's, concern regarding potential en-
vironmental insult due to organic emis-
sions from this disposal  method  has
developed only  recently. Very  little is
known  about organic emissions from
municipal  sludge incinerators, and the
research program described herein was
designed to begin filling in such a data
base, and to support the development of
regulations for  sewage sludge  in-
cinerators.
  The Domestic Sludge  Exclusion re-
moves from hazardous waste status the
solvents, industrial effluents,  process
wastes, etc., which are  discharged to
publicly owned treatment works. As  a
result, some 20,000 metric tons of priority
organic pollutants enter wastewater
treatment  plants in the  United States
each  year. It is documented that priority
pollutants such as pesticides, polychlori-
nated biphenyls, phenols,  phthalates,
polynuclear aromatic hydrocarbons, diazo
dyes,  common solvents, and nitrosamines

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  concentrate on sewage sludge. Most of
  these contaminants are found in con-
  centrations of 0.1  to  100 /itg/g  (ppm),
  based on the dry weight of the sludge.
  Some potentially toxic  organics found in
  sewage sludge are biodegradation pro-
  ducts from less toxic precursors.  For
  example, nonylphenol, a biodegradation
  product from nonylphenol  ethoxylates
  (common nonionic surfactants), has been
  detected at levels around 1000 ng/g in
  sewage sludge.
    While emissions of metals, particulates,
  and gases such  as SOX and NOX have
  been characterized to some extent for
  sludge incinerators, very little data exists
  concerning organic emissions. Limited
  field data  indicates  that polynuclear
  aromatic  hydrocarbons and  chlorinated
  dioxins and furans are  emitted from
  sludge incinerators.
    Assessment of organic emissions from
  municipal sludge incineration is further
  complicated by  the wide range  of in-
  cineration conditions  which  occur. In-
  cineration parameters  are not generally
  as well characterized  or  controlled as
  they are for hazardous waste incineration.
  This is particularly true for the  multiple
  hearth incinerators,  which  constitute
  about 80% of the incinerators used for
  sewage sludge disposal. The other 20%
  are  primarily fluidized  bed incinerators,
  in which  conditions are better defined
  and controlled.
    The laboratory studies described herein
  were designed to generate a data base
  on  potential  organic  emissions from
  sewage sludge incinerators. The research
  is broken down into three major areas:
    1. Potential emissions  of hazardous
      sludge contaminants and products
     of incomplete combustion  (PIC's)
     from sludge incineration;
  2. Potential emissions of organics due
     to volatilization in the drying zone of
     the multiple hearth incinerator; and
  3. Elementary  reaction  rates  of
     hydroxyl radicals with model sludge
     contaminants.


Thermal Decomposition of
Spiked Sludges and Spiking
Mixtures

Experimental
  To study the thermal decomposition of
common sewage sludge  contaminants,
and  to  identify products  of  incomplete
combustion  (PIC's)  from contaminated
sewage sludge, thermal  decomposition
studies were conducted on the Thermal
Decomposition  Unit-Gas  Chromato-
graphic (TDU-GC) system and the Thermal
Decomposition Analytical System (TDAS).
Block diagrams of these systems are given
in Figures 1 and 2, respectively. Both
systems include  thermal  decomposition
units in which temperature, atmosphere,
and mean residence time can be precisely
controlled. In the case of the  TDU-GC,
this thermal  unit is interfaced with an in-
line  gas chromatograph (GC),  while  in
the case of the TDAS, the analytical in-
strumentation is an in-line gas chromato-
graph-mass spectrometer  (GC-MS).
Details  concerning  these systems are
given in the full report.
  Thermal decomposition studies  were
conducted on a relatively clean sludge
spiked with mixtures of contaminants, on
mixtures of pure contaminants (without
sludge), and on unspiked sludge.  Con-
 taminants were studied in three mixtures
 rather than as pure compounds so that a
 number of compound classes could be
 investigated within the constraints of the
 program. The contaminants which were
 studied  were  heptachlor; pentachloro-
 phenol; diphenylnitrosamine; pyrene;
 butyl  benzyl  phthalate; 2,3',4,4',5-
 pentachlorobiphenyl;  azobenzene;  and
 technical-grade nonylphenol.
   Sewage sludge used for these studies
 was a filter-cake sludge containing 17%
 solids,  and was obtained from a  local
 wastewater treatment plant  from  a pri-
 marily  residential municipality.  This
 sludge was not adequately dewatered for
 efficient incineration, but was otherwise
 similar  in composition to sludges which
 are incinerated. The sludge was spiked at
 about 1  mg/g with the  organic compo-
 nents, except nonylphenol, which was
 spiked at 10  mg/g. These levels are at
 least an order of magnitude greater than
 those typically found in  "real world"
 sludges, but such  spike  levels were re
 quired to minimize interferences on the
 TDU-GC from the sludge matrix.
  Variables investigated  in these studies
 included gas  phase temperature (300C
 to 1000C), oxygen level  (air for combus-
 tion  studies and  nitrogen for pyrolytic
 studies), and sample matrix (spiked sludge
 versus mixtures of pure spike compounds)
 For spiked sludges and mixtures of pure
 compounds, the TDU-GC was used to
 generate thermal  decomposition curves
 as a function of reactor temperature and
 oxygen level. The TDAS was then used to
 identify products of incomplete combus-
tion (PIC's) by selecting reactor tempera-
tures that, based  upon  TDU-GC  data,
would yield the majority of the PIC identifi
                                            Thermal Decomposition Unit


Captt
Effluent

ire of
Products

SSSS&

sssss


Controlled High
Temperature Exposure

SSSSS
^
SSSS^sS

Sample Insertion
and Vaporization
\ 1
High Temperature Transfer



Pressure and
Flow Regulation




Compressed Gas
and Purification


                                        Multifunctional
                                      Gas Chromatographic
                                        Instrumentation
                            Containment or Destruction of
                                  Effluent Products
Figure 1.    Block diagram of TDU-GC.

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                         High Temperature Transfer
            Capture
               of
            Effluent
            Products
77/7/77,
 Controlled
   High
Temperature
 Exposure
  Sample
 Insertion
   and
Vaporization
                                      In-Line
                                 Gas Chromatograph
                                  (High Resolution)
Figure 2.   Block diagram of TDAS.
                                                      Computer
                                                       System
                                                      NIH-EPA
                                                      Chemical
                                                     Information
                                                       System
                                                   Pressure and
                                                  Flow Regulation
Compressed Gas
and Purification
                                                 Coupled
                                                  Mass
                                               Spectrometer
                                                (Magnetic)
cations. The unspiked sludge was studied
using the TDAS only, since there were
no contaminant thermal decomposition
profiles to generate.
  A  thermal decomposition  run  was
initiated  by inserting  the sample,  con-
tained in the sludge probe, into the sample
insertion region of the TDU-GC or TDAS.
After allowing laboratory air to be purged
from the  system,  the insertion  region
was  programmed from 50C to 200C at
15C/min. During sample heating, the
vaporized sample components  were con-
veyed  into the reactor  using  either
nitrogen or air. The reactor temperatures
were varied over the range of 300C to
1000C, and a 2-second gas-phase mean
residence time  was  maintained  in the
reactor. The reactor  effluent  (both un-
decomposed parents  and  products  of
incomplete combustion) was trapped at
the head  of the in-line gas chromato-
graphic column. After purging the system
with a helium carrier gas, the GC was
programmed to elute the trapped species,
                 which were detected using an FID detec-
                 tor for the TDU-GC,  or a mass spectro-
                 meter for the TDAS. Frequent  method
                 blanks and duplicates were run to ensure
                 the integrity of the data.

                 Results and Discussion
                    The thermal  decomposition of nonyl-
                 phenol typifies the behavior observed for
                 the majority of the sludge contaminants.
                 Thermal  decomposition  profiles for
                 nonylphenol  as  a  function  of  matrix
                 (spiked onto sludge versus run in a mix-
                 ture of pure  compounds)  and of atmo-
                 sphere (nitrogen versus air) are shown in
                 Figure 3. These curves indicate that for a
                 given matrix, the compound was more
                 stable in  nitrogen than in air. This is
                 typical behavior for many organic com-
                 pounds and  was not surprising  here.
                 Figure 3  indicates  that sample  matrix
                 also affected the thermal decomposition,
                 with nonylphenol being more difficult to
                 destroy in the presence of sludge than in
                 the presence of the pure mixture.
                                                   While the sludge appeared to stabilize
                                                 most of the contaminants studied, there
                                                 were some cases where the sludge en-
                                                 hanced the thermal decomposition, and
                                                 some  where  the sludge exerted little
                                                 effect.  Based  on the limited data from
                                                 eight hazardous  contaminants, the fol-
                                                 lowing trends were observed:
                                                    The sludge exerted little if any effect
                                                     on the ease of destruction of very
                                                     fragile contaminants.
                                                    If a contaminant was intermediate
                                                     in thermal stability, it was more dif-
                                                     ficult  to destroy in the presence of
                                                     the sludge.
                                                    If a contaminant was very stable in
                                                     the pure  mixture, the sludge en-
                                                     hanced its ease of destruction.
                                                   Comparing the overall thermal stability
                                                 of the eight sludge contaminants, pyrene
                                                 was the most stable  and butyl  benzyl
                                                 phthalate was the least stable. The rela-
                                                 tive ease  of incineration of the eight
                                                 hazardous  contaminants increases in the
                                                 following order: pyrene < pentachloro-

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   700
  .1/0
  .c
  c
    1
    0.1
  0,01
                        1	\	r
               Npnylphenol
                ~t - 2.0 sec
                 OH
       HC-CH2- CH-
        (      t
       CH3   CH3

O /Vg2, Mixture
Q AIR, Mixture
& N2. Sludge
O AIR, Sludge
                       J	1	1	I	I   I
                                                J	L_
            700    200    300    400    500    500    700
                               Exposure Temperature, C -~
                                                   800    900   WOO
 Figure 3    Thermal decomposition profiles for nonylphenol
 biphenyl  <  pentachlorophenol < di-
 phenylamine < azobenzene < nonyl-
 phenol < heptachlor < butyl benzyl
 phthalate.
   A multitude  of thermal reaction pro-
 ducts were identified for spiked sludge,
 and mixtures of pure spiking compounds.
 Analysis of the data indicates that some
 PIC's could be  attributed to  the sludge,
 while others could be attributed to the
 contaminants, and still others may  have
 formed through an interaction of the
 sludge and the contaminants. Interaction
 between the sludge and chlorinated con-
 taminants may  be the source of the trace
 emissions  of chlorinated dioxins  and
 furans from certain sludge incinerators.
  The majority of the PIC's were aromatic,
 and the remainder were primarily chlori-
 nated  or  unchlorinated  short-chained
 unsaturated aliphatic hydrocarbons. The
 reader is referred to the final  report for a
 complete  discussion and tabulation  of
 PIC's, since only a few examples can be
 given here. Pentachlorophenol, for ex-
 ample,  yielded chlorinated  benzenes,
 tetrachlorophenol,  tetrachloropropyne,
 hexachlorodihydro-naphthalene,  and
 other PIC's.  Diphenylnitrosamine  was
 100% converted to diphenylamine at very
 low temperatures; this primary PIC  was
then the precursor  for carbazole, ben-
zonitrile,  biphenyldicarbonitrile,  and
possibly other PIC's.
  The sludge itself yielded a  number of
PIC's which are of environmental concern.
                               At relatively low temperatures (~500C),
                               desorption/decomposition products from
                               the sludge included primarily compounds
                               having the cholesterol-fused ring struc-
                               ture  and alkenes or  cycloalkanes.  At
                               higher temperatures (~800C), benzene,
                               styrene,  toluene,  benzaldehyde,  ethyl-
                               benzene, xylene, and various polynuclear
                               aromatic hydrocarbons were formed as
                               PIC's.  A number  of these  are on  the
                               Appendix VIII list of hazardous compounds
                               and/or have produced positive results in
                               various toxicological  tests.  Since  the
                               sludge used for these experiments origi-
                               nated  in a  relatively nonindustrialized
                               municipality, these PIC's are attributed to
                               the biomass rather than to environmental
                               contaminants.
                                These laboratory studies indicate that
                               PIC's from the sludge contributed  much
                               more  to the total mass emissions than
                               did PIC's from the contaminants. This is
                               primarily because the contaminants were
                               spiked at only parts-per-thousand levels
                               in the  sludge, meaning that the relative
                              weight of the  starting sludge was orders
                              of magnitude greater  than that of the
                              starting contaminants. For "real world"
                              sludges, which  generally contain con-
                              taminants as parts-per-million rather than
                              parts-per-thousand levels, the  relative
                              contribution of the biomass to total mass
                              emissions is expected to be even greater.
                                The  fact  that  potentially toxic com-
                              pounds were  formed from  the  sludge,
                              combined with  the fact that the  total
  levels of PIC's were many times greater
  for the sludge than for the trace con-
  taminants,  indicates the importance of
  incinerating all sludges under highly con-
  trolled  and environmentally  safe
  conditions.


  Multiple Hearth Approximation

  Experimental
    Because both temperatures and resi-
  dence times in  the drying zone of the
  multiple hearth incinerator are relatively
  low, it was hypothesized that incineration
  efficiency would be poor in this zone. The
  temperature appeared to be high enough
  to volatilize many organic species, but
  not  sufficiently high  to  initiate  their
  thermal decomposition.  For this reason,
  an experiment was designed to determine
  the potential for emissions from the drying
  zone of a multiple hearth incinerator.
   The thermal exposure within the drying
  zone of the multiple hearth  incinerator
  was best mimicked by gradually heating
  the sludge in the insertion region of the
  TDU-GC while maintaining the reactor at
  a low temperature. Therefore, a single
  sludge sample was placed in the sample
  insertion region of the TDU-GC, and was
 successively heated at  15C/min  in
  nitrogen over four temperature ranges.
 These temperature ranges were 50C to
 200C, 200C to 300C, 300C to 400C
 and 400C  to  500C. The  gas-phase
 residence time of desorbed species in the
 insertion region was less than 1 second.
 During the entire experiment, the reactor
 was  maintained at  a  nondegradative
 temperature (300C). While the sample
 was being  heated over a given tempera-
 ture range,  any  evolved species were
 condensed at the head of the  in-line gas
 chromatographic column.  After  these
 species were collected,  they were
 analyzed using programmed temperature
 capillary gas chromatography (GC), with
 flame ionization detection (FID). Once the
 GC run was complete, the same sample
 was then heated over the next tempera-
 ture range  and the analytical process
 repeated. This procedure was repeated a
 total of four times, until a final tempera-
 ture of 500C was achieved.

 Results and Discussion
  Results of this experiment indicate that
 the majority of the volatile sludge compo-
 nents desorbed during the initial program
 step between 50C and 200C. Signifi-
cant residuals also desorbed in the 200C
to 300C and the 300C to 400C ranges,
but a  marked decrease in desorbed or-

-------
ganics was seen between 400C and
500C. Overall this experiment clearly
illustrated the potential for major emis-
sions from volatilization  and/or  in-
complete combustion of sludge compo-
nents in the drying zone of the multiple
hearth incinerator.
  A  comparison  of potential emission
levels from the multiple  hearth versus
the fluidized bed incinerator is shown in
Figure 4. The top chromatogram depicts
volatile species desorbed from the sludge
and  conveyed through  the reactor  at
300C, while the bottom  chromatogram
shows the remaining species after these
volatilized organics have been subjected
to an 800C reactor temperature. While
the thermal conditions in the top chro-
matogram approximate those in the drying
   (a) Reactor at 300 C
      (transport temperature)
zone of the multiple hearth incinerator,
those in the bottom chromatogram are
more characteristic of the thermal regime
in the  fluidized  bed incinerator.  This
indicates that the thermal regime of the
fluidized bed incinerator  is  much less
likely than that of multiple hearth to lead
to major gaseous organic emissions.


Hydroxyl Radical
Reactivity Studies

Experimental
  For the combustion of hydrocarbons,
OH radicals are the dominant reactive
species under all  but the most fuel-rich
environments. Although it is recognized
that  chlorine atom  reactivity may be
                                             I li  II
                                            U.UUJU I III
                                            -
                                                116
important for chlorinated hydrocarbons
such as those produced as PIC's in the
thermal  degradation of contaminated
sewage sludge, OH reaction kinetics are
considered most significant with respect
to the  oxidative destruction  of these
materials. Since there is a general paucitv
of data on OH-chlorocarbon  reaction;.
and  data are practically non-existent a:
the  high temperatures which simulant
incinerator conditions, the high tempera-
ture elementary  reaction rates of OH
radicals with select chlorocarbons were
determined for this program via a  laser
photolysis/laser-induced  fluorescence
technique.  This experimental  approach
allows the generation and detection of
OH  radicals  in a "clean" environment
where essentially only OH-chlorocarbon
reactions can occur. This eliminates the
complexities of rate constant determina-
tions in  multireaction media such  as
shock tubes, flames, and flow reactors.
  The experimental test system consisted
of five inter-dependent components; (1) 
test cell and temperature control system,
(2) the carrier gas and sample delivery
system, (3) the pump laser system, (4) the
probe beam system, and (5) the detection/
measurement system. The test cell was a
specially designed pyrex cell  which al
lowed  gas  reactants to be  heated,  ir-
radiated with laser beams, and observed
By monitoring relative concentrations of
OH over time, the reaction rates of OH
radicals with organic  molecules were
calculated.
  The chloromethanes were chosen  as
model chlorocarbon compounds for this
initial study because chlorinated hydro
carbons are  both known sludge  con
taminats and stable PIC's produced from
decomposition of contaminated sludge.
Pseudo-first order rate constants were
generated for  all the chloromethanes over
a temperature range of 296 to 782K.
    (b) Reactor at 800 C
                                                   129

Figun 4 .    Comparison of potential emissions levels from fa) drying zone of multiple hearth
            versus fb) fluidized bed incinerator.
                                        Results and Discussion
                                          Table 1 presents bimolecular rate con-
                                        stants for reactions of OH radicals with
                                        the chloromethanes over a temperature
                                        range  of 571  to 782K.  A  statistical
                                        propagation of error analysis was appliec
                                        to the data collection procedure with the
                                        results presented in Table 2. With  minoi
                                        exceptions, good precision was indicated
                                        as standard deviations in the rate con-
                                        stants were generally less than 10% of
                                        the measured value. The temperature
                                        dependence of the bimolecular rate con-
                                        stants  were  evaluated  with  weighted
                                        least-squares algorithms in  relation tc

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 the Arrhenius expression:

           k = A exp [-Ea/RT]

 and the three-parameter non-Arrhenius
 expression:

           k = BTn exp [E/T].

 The data analyzed in this manner always
 exhibited non-Arrhenius kinetics with the
 results presented in Table 2.
Table 1.


Reactant
CH3C1
CH3C1
CH3C1
CH2C12
CH2C1 2
CH2C12
CHC13
CHC13
CHC13
CC14
CC14
CC14
Chloromethane-OH Rate
Constants as a Function of
Temperature (571 to 782 K)
kdO^crrf/molec-s) TfKJ
8.380.296* 578
15.961.31 687
24.972.25 776
11.120.590 580
19.832.94 674
33.264.09 773
14.071.60 571
20.001.46 680
31.731.81 772
J.650.056 614
3.540.050 773
5. 120.800 782
 * Standard deviation in rate constant.

  The rate  data  indicated relative  OH
 reactivities for the chloromethanes to be:

  CHC13 ^ CH2C12 > CH3C1  CC14.

 The high temperature relative reactivities
 for CH3C1,  CH2C12, and CHC13 are in
 accord  with their  gas-phase thermal
 stabilities under oxidative conditions. In
 other words, OH reactivity increases with
 increasing  C1  substitution for  the
 chloromethanes. This  indicates that  OH
 reactivity is more sensitive to the ease of
 hydrogen  atom  abstraction (which  in-
 creases  as  the C1  atom  substitution
 increases) than to the total number of
 abstractable H atoms present. If we extend
this hypothesis to the  limit of  perchlori-
 nated compounds, these results indicate
a much smaller OH reactivity as compared
to  any of  the hydrogen-containing
chloromethanes. Although the C-C1 bond
in CC14 is weaker than any C-H bond in
the  remaining  chloromethanes, the
endothermicity of this reaction due to the
low stability of HOC1  formation results in
a relatively high-energy reaction pathway.
  Extrapolating these results to the types
of PIC's  produced in the oxidative de-
gradation  of  contaminanted  sewage
sludge, perchlorinated hydrocarbons such
as C2C12,  C2C14,  C3C14,  and  C4C140,
should prove more difficult to incinerate
than their hydrogen  containing analogs
(i.e.,  C2HC1, C2HC13) due to the lack of
abstractable hydrogen atoms. Additional
PIC's believed to form from the sludge
matrix, such  as simple aromatics (i.e.,
benzene, toluene, styrene), should prove
more difficult  to incinerate than  their
chlorinated analogs because of the larger
C-H bond energies.

Conclusions
  Based  on laboratory  studies  of the
thermal  decomposition  of  hazardous
organic mixtures  and sewage  sludge
spiked with various  hazardous organic
compounds, the following conclusions are
proposed:
   Some  common  hazardous organic
    contaminants  are  relatively fragile
    and easily destroyed, but their pro-
    ducts of incomplete combustion pose
    a greater incineration challenge.
   Contaminants  of moderate-to-high
    thermal stability may be volatilized
    in the drying zone of multiple hearth
    incinerators and emitted with great
    efficiency.
   The thermal decomposition behavior
    of common  hazardous sludge  con-
    taminants differed when  these
    principal organic hazardous con-
    stituents (POHC's) were decomposed
    as mixtures in a sludge matrix versus
    as mixtures of pure compounds. The
    following trends  were observed for
    the eight POHC's tested:
     For very fragile POHC's, the sludge
      exerted no effect on the inciner-
      ability of the POHC.
    For  POHC's  of intermediate
      thermal  stability (most of  the
      compounds  tested),  the sludge
      appeared to decrease the inciner-
      ability of the POHC (i.e., compound
      was more stable in sludge).
Table 2.    Non-Arrhenius Parameters for Chloromethane-OH Reactions

   Reactant        BfcrrP/molec-s)          n       E(cal/mole)
                        T Range (K)
CH3C1
CH2C12
CHC13
CC14
5.891.22*xW2'
5.140.98x10'21
8.380.45x10'21
4.560.80xia22
3.0
3.0
3.0
3.0
-14559*
7559
7021
331 67
296 - 776
298 - 773
298 - 772
296 - 782
* One standard deviation in data.
      For very stable POHC's the sludge
        increased the incinerabilityof the
        POHC  (i.e., POHC was  more
        readily destroyed in presence  of
        sludge).
    Thermal  decomposition products
     from  the biomass  itself  included
     potentially hazardous PIC's which
     are on EPA's Appendix VIII list.
    Total  mass emissions from the
     biomass are expected to be  much
     greater than  from  trace  con-
     taminants.
    Interactions between the sludge and
     chlorinated contaminants may pose
     additional health risks in incineration
     of sludge from industrial sites.


 Recommendations
   The results of this study have answered
 some  very basic  questions;  however,
 some very important questions have been
 raised. The following additional research
 is recommended:
    Conduct additional laboratory studies
     to explain the  sludge stabilization
     effect on hazardous organics.
    Extend  laboratory testing to  other
     sludges  and contaminants.
    Extend  the laboratory analysis to
     include  identification of volatile
     emissions.
    Conduct laboratory analysis of the
     uncombusted  sludge  residue  to
     determine the chemical composition
     of full-scale particulate emissions.
    Conduct additional laboratory studies
     on the effects of sludge heating rate
     in both multiple  hearth and fluidized
     bed systems.
    Utilize laboratory test data to guide
     future full-scale emissions  testing
     and derive correlations  between
     predicted versus observed emissions.
    Based on laboratory  data, establish
     a  "hit list" of suspected major in-
     cinerator emissions  that would be
     the subject of full-scale compliance
     testing.
   Determine health  effects of these
     emissions to compare with other
     sources  for the  establishment of  a
     mass emissions regulatory standard.
  The  full report was submitted in ful-
fillment of  Cooperative Agreement No.
CR-811777 by the University of Dayton
Research Institute under sponsorship of
the  U.S.  Environmental  Protection
Agency.

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     Sueann Mazer, Philip H.  Taylor,  and Barry Del linger are with the University
       of Dayton Research Institute, Dayton, OH 45469.
     Richard A. Dobbs is the EPA Project Officer (see below).
     The complete report  entitled "Potential  Emissions of Hazardous  Organic
       Compounds from Sewage Sludge Incineration," (Order No. PB 87-199 626/
       AS; Cost: $18.95, subject to change)
     will be available only from:
             National Technical Informaiion Service
             5285 Port Royal Road
             Springfield, VA 22161
             Telephone: 703-487-4650
     The EPA Project Officer can be contacted at:
             Water Engineering Research Laboratory
             U.S. Environmental Protection Agency
             Cincinnati, OH 45268
United States
Environmental Protection
Agency
     BULK RATE
POSTAGE & FEES PAID
        EPA
   PERMIT No G-3b
Official Business
Penalty for Private Use $300
EPA/600/S2-87/046

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