United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
E PA/600/SR-92/003 May 1992
Project Summary
Emissions of Metals,
Chromium and Nickel
Species, and Organics from
Municipal Wastewater Sludge
Incinerators
William G. DeWees, Robin R. Segall, Laurie Cone, and F. Michael Lewis
In order to provide data to support
regulations on municipal wastewater
sludge incineration, emissions of met-
als, hexavalent chromium, nickel
subsulfide, polychlorinated dibenzo-di-
oxins and furans (PCDD/PCDFs),
semivolatile and volatile organic com-
pounds, carbon monoxide (CO), and to-
tal hydrocarbons (THCs) from two mul-
tiple hearth incinerators and a fluidized
bed incinerator were measured. The
emissions were controlled at each unit
with venturi/scrubbers and, on two of
the units, emissions from wet ESPs were
determined. Flue gas sampling was con-
ducted at the inlet and outlet of the air
pollution control devices. Feed sludge
was tested for metals, moisture, and
carbon and hydrogen content. Testing
occurred at both normal and improved
(low CO) combustion conditions. Two
additional tests were conducted under
this study to evaluate draft methods for
sampling and analysis of hexavalent
chromium and systems for continuous
monitoring of CO and THC emissions.
All test results arefully documented in
individual site reports. Emission test re-
sults are separated into normal and low
CO conditions. Gas concentrations,
mass emission rates, metals-to-particu-
late ratios, and emissions factors are
presented. The ratios of hexavalent-to-
total chromium and nickel subsulfide-
to-total nickel are given. Analytical re-
sults for the process samples are pro-
vided. Isomer-specific PCDD/PCDF and
semivolatile and volatile organic com-
pound concentrations are reported. Con-
tinuous emission monitoring results for
SO2 NO^, CO2, O2, CO, and THC are pre-
sented.
This Project Summary was developed
by EPA'a Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The U.S. Environmental Protection
Agency's (EPA's) Office of Water (OW) has
been developing new regulations for sew-
age sludge incinerators and EPA's Risk
Reduction Engineering Laboratory (RREL)
has been assisting OW collect supporting
data. There is particular concern regarding
chromium and nickel species in the emis-
sions from incineration of municipal waste-
water sludge because of the associated
cancer risk. OW has drafted risk-based
sludge regulations under Section 405d of
the Clean Water Act that have been pub-
lished for comment in the Federal Register,
Volume 54, No. 23, February 6,1989. Final
regulations are scheduled for publication in
the Federal Registers July 1992.
The draft regulations are based on the
risk incurred by the "most exposed indi-
vidual" (MEI). The MEI approach involves
calculating the risk associated with an indi-
vidual residing for 70 yr at the point of
maximum ground level concentration of the
emissions just outside the incinerator facil-
ity property line. EPA's proposal for regulat-
ing sewage sludge incinerators is based on
ensuring that the increased ambient air
concentrations of metal pollutants emitted
from sludge incinerators are below the am-
Printed on Recycled Paper
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bient air human health criteria. The concen-
trations are identified in the proposed regu-
lations as Risk Specific Concentrations
(RSCs). Both nickel and chromium emis-
sions from sludge incinerators presented a
specific problem in establishing RSCs, be-
cause unknown portions of the emissions of
these metals are in forms that are harmful to
human health. In performing the risk calcu-
lations, EPA assumed that 1 % of the emis-
sions of chromium from the sludge incinera-
tors is in the most toxic form, hexavalent
chromium. This was based on limited data.
For nickel, EPA assumed that 100% of the
nickel emissions are in the most toxic form,
nickel subsulfide. No data on nickel
subsulfide were available so the most con-
servative approach was taken. The lack of
a substantial data base on hexavalent chro-
mium and nickel subsulfide prompted EPA
to plan additional measurements of these
constituents in sewage sludge incinerator
emissions.
To collect additional data, a comprehen-
sive test program was developed to deter-
mine the ratios of hexavalent-to-total chro-
mium and nickel subsulfide-to-total nickel
for a typical sewage sludge incinerator un-
der normal combustion conditions (higher
concentrations of carbon monoxide and to-
tal hydrocarbons) and improved combus-
tion conditions (lower concentrations of car-
bon monoxide and total hydrocarbons).
Test Methods
At Site 5 (continuing a numbering system
initiated in a previous 4-site project) tests
were only conducted for methods develop-
ment purposes. At Site 6, emissions were
measured at the inlet and outlet of the
control device. At Site 7, an evaluation of
CO and THC continuous emission monitor-
ing systems (CEMSs) was performed. At
Sites 8 and 9, emissions were measured at
the inlet of the venturi scrubber, at the
midpoint located between the venturi scrub-
ber and the wet ESP, and at the outlet of the
wet ESP. For Sites 6,8, and 9, midpoint and
outlet air emission samples were collected
and analyzed for particulate matter, metals,
PCDD/PCDFs, volatile and semivolatile
compounds (except Site 6), and hexavalent
chromium and nickel subsulfide species.
Continuous emission monitoring (CEM) for
O2, CO2, CO, SO2, and NOX at the control
system inlet and O (except Site 6), CO
(except Sites 6 ana 9), CO, SO2 (except
Sites 6 and 9), NOX (except Sites 6 and 9),
and THC was conducted at the control
system outlet stack. The monitoring data
were used principally to determine process
and control equipment operating conditions
during the chromium and nickel speciation
tests. Process samples consisting of sludge
feed, scrubber inlet and discharge water,
and bottom ash (except Site 8) were col-
lected. Process samples were analyzed for
the metals listed in Table 2 and were sub-
jected to ultimate and proximate analysis.
The heating value of the sludge feed was
calculated from the carbon and hydrogen
content.
Particulate matter and metals sampling
was conducted following the procedures in
the draft EPA method, "Methodology for the
Determination of Trace Metals Emissions in
Exhaust Gases from Stationary Source
Combustion Processes."
Flue gas sampling for PCDD/PCDFs and
semivolatile organic compounds followed
procedures in SW-846 Method 0010, ex-
cept that a final toluene rinse was con-
ducted and analyzed separately for PCDD/
PCDF. The samples were analyzed for
PCDD/PCDF using SW-846 Method 8290
and for other semivolatile organic com-
pounds using a combination of SW-846
Methods 3540,3550,3510,3520, and 8270.
Flue gas sampling for volatile organic
compounds employed the volatile organic
sampling train (VOST) in accordance with
SW-846 Method 0030.
Flue gas sampling and analysis for
hexavalent chromium followed the proce-
dures in the draft EPA method, "Determina-
tion of Hexavalent Chromium from Station-
ary Sources." This sampling train continu-
ously recirculates the impinger solution to
the sample nozzle to prevent conversion of
hexavalent chromium during sampling. A
radioactive hexavalent chromium isotope
was used to verify that conversion was not
significant. Hexavalent chromium samples
were analyzed by ion chromatography
coupled to a diphenylhydrazine post-col-
umn reaction (IC/PCR) on the filtered
impinger samples. Diphenylhydrazine com-
plexes of tri-and hexavalentchromium were
analyzed colorimetrically.
Flue gas sampling and analysis for nickel
species followed the draft EPA method,
"Methodology for the Determination of Nickel
Compound Emissions from Stationary
Sources." Analysis of the nickel speciation
samples was performed following the Nickel
Producers Environmental Association
(NiPERA) sequential leaching method. The
ratios of sulfidic nickel species, nickel
subsulfide (Ni3S ) and nickel sulfide (NiS),
to total Ni were determined.
EPA Methods 1, 2, 3, and 4 were used in
conjunction with the sampling procedures
described above. Method 3 samples were
collected as backup for O2 and CO2 determi-
nation should the CEMSs data be unavail-
able.
The CEMSs used to measure concentra-
tions of CO, CO2,02, NOx, SO , total hydro-
carbons (THC as propane) followed the
EPA instrumental Methods 10, 3A, 7E, 6C,
and 25A, respectively. The primary intent of
the continuous monitoring effort was to: (1)
determine concentrations of these com-
pounds and (2) provide a real-time indica-
tion of combustion conditions. The continu-
ous monitoring systems were calibrated
daily, but no attempt was made to certify the
monitors using the EPA instrumental test
methods.
The dewatered sludge samples were
analyzed for the target metals after determi-
nation of their moisture and ash content,
heating value, and proximate and ultimate
analyses.
Incinerator and control system operating
parameters were monitored during all
manual test runs to characterize the system
operations.
Results
The metals found in the greatest concen-
tration in the sludge were lead, chromium
and nickel. The particulate matter and met-
als emissions factors from the normal con-
trol device (venturi/scrubber) outlet are
shown for normal and low CO conditions
(Table 1). At Sites 6, 8, and 9, the metals
were measured at the venturi/scrubber inlet
and outlet, and for Sites 8 and 9, at the outlet
of the wet ESP. The removal efficiencies
were calculated and are summarized in
Table 2.
The need for sampling hexavalent chro-
mium without artifact formation and analy-
sis of the resulting samples specifically for
hexavalent chromium at low concentrations
was a major accomplishment of this test
program. Sampling activities conducted at
Site 5 were dedicated to developing a suit-
able measurement method for hexavalent
chromium in emissions from incineration of
municipal wastewater sludge. Hexavalent
chromium sampling at the venturi/scrubber
outlets at Sites 6,8, and 9 followed the same
procedures of the draft EPA method. The
surrogate recoveries for Sites 6, 8, and 9 at
both midpoint and wet ESP outlets are
shown in Table 3, along with the ratio of
hexavalent to total chromium measured with
the recirculation train. At Site 6, the
hexavalent to total chromium ratio increased
from 1.9% to 8.3% between the normal
combustion conditions to the low CO (im-
proved combustion) conditions. This obser-
vation, shown graphically in Figure 1, can
be explained by the higher hearth tempera-
tures and excess oxygen levels recorded
during the improved combustion condition
that would favorthe formation of hexavalent
chromium. At Site 8, a fluidized bed incin-
erator, the hexavalent chromium to total
chromium ratio was below the detection
limit (<2%) at both the scrubber and wet
ESP outlets. At Site 9, a multiple hearth
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Table 1. Particulate and Metals Stack Emission Factors for Steady State (Low CO) and
Normal Operation
Emission Factors (g metal emitted/g metal fed)
Pollutant
PM (g/kg dry
sludge feed)
Arsenic
Beryllium
Cadmium
Chromium
Lead
Nickel
Site6
Normal
0.37
NO*
<0.069
0.917
0.011
0.123
0.030
Si te6
Low CO
0.45
ND
0.059
0.906
0.005
0.136
0.013
Site 8
Normal
4.59
ND
<0.0001
0.0003
0.0001
<0.0001
<0.0001
Site 9
Nonnal
0.36
•eO.OH"
ND
0.336
0.036
0.101
0.004
Site 9
Low CO
0.04
<0.013
ND
<0.008
0.001
0.006
0.0004
'ND - Not detected, all sample measurements were below the analytical detection limit.
" < • Outlet samples were below analytical detection limit, calculated ratio is less than value
shown.
Table 2. Metals and Particulate Removal Efficiency Across the Various Control Devices (%)
Element
Arsenic
Beryllium
Cadmium
Chromium
Lead
Nickel
Particulate
Matter
Site 6
Normal
Scrubber
NA*
>65.5
71.9
99.3
71.3
93.4
98.5
Site 6
Low CO
Scrubber
NA
>86.7
77.3
99.4
78.1
94.5
97.6
Site 8
Normal
Scrubber
>99.5
>99.95
99.82
99.92
99.91
99.89
99.99
Site 8
Normal
Wet ESP
NA
NA
71.0
62.0
>96.0
81.0
78.0
Site 9
Normal
Scrubber
NA
-
0.0
0.0
5.0
89.0
85.0
Site 9
Low CO
Scrubber
NA
-
45.0
89.0
54.0
96.0
95.0
Site 9
Low CO
Wet ESP
NA
-
>98.0
88.0
96.0
90.0
87.0
'NA • Not applicalbe.
Table 3. Hexavalent Chromium Sampling Results
Site 6
Normal
Site 6
Low CO
Site 8
Nonnal
Site 9
Nonnal
Site 9
Low CO
Venturi/Scrubber Outlet
Surrogate recovery
Hexavalent to
'NA - Not applicable.
90.5
95.6
66.8
84.3
90.5
total Cr ratio
Wet ESP Outlet
Surrogate recovery
Hexavalent to
total Cr ratio
1.9
NA1
NA
8.3
NA
NA
<1.8 11.9
81.5 90. 1
<1.4 29.9
7.9
93.1
42.5
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11
10
9
g a
I M
3
2 -
1 -
Run 11
Pun 9
rm-0.98
Run 3
Run 13
40
60
80
100
120
CO to CCz Ratio (ppm to %)
Figure 1. Correlation of combustion efficiency and hexavalent to total chromium ratio of Site 6.
furnace, the hexavalent to total chromium
ratio increased from 11.9% to 29.9% be-
tween the normal combustion conditions to
the low CO (improved combustion) at the
scrubber outlet and increased from 29.9%
to 42.5% at the wet ESP outlet. The in-
creased percentage of hexavalent chro-
mium at the wet ESP outlet is a result of
higher collection efficiency of trivalent chro-
mium by the wet ESP.
The results of the nickel sampling and
analysis indicate that within the detection
limit of the wet chemical method, no nickel
subsulfide was present in the air emissions.
Sampling for PCDD/PCDFs was per-
formed at the venturi/scrubber outlet at Sites
8 and 9 (termed the Midpoint at Site 9) and
at the wet ESP outlet at Site 9. Sampling at
Site 9 was conducted at both normal and
lowCOconditions. The resultsforthe PCDD/
PCDF sampling are shown in Table 4.
At Site 9, sampling for semivolatile or-
ganic compounds was performed at the
venturi/scrubber outlet (Midpoint) and the
wet ESP outlet under both normal and low
CO conditions. The results for the
semivolatile organic compound sampling
are shown in Table 5. The concentration of
Table 4. Dioxin/Furans Emissions Summary
Concentration (ng/DSCM
Congeners
Total Tetra-
Octa CDD
Total Tetra-
Octa CDF
Total Tetra-
Octa CDD/CDF
Site 8
Normal
Outlet
0.721
1.41
2.13
Site 9
Normal
Outlet
3.2
12.4
15.6
Site 9
Normal
Mid-Point
20.2
81.9
102
Site 9
Low CO
Outlet
0.7
2.1
2.8
Site 9
Low CO
Mid-Point
1.6
7.1
8.7
the volatile organics in the flue gas are
presented in Table 6.
At Sites 6 and 9, a positive correlation
between carbon monoxide emissions and
THC emissions was observed. At Site 8,
both the CO and THC emissions were suf-
ficiently low that a correlation could not be
seen.
At Site 7, positive correlations were dem-
onstrated for the "Hot" and "Cold" THC
CEMs.
The accomplishments of the study were
far greater than could have been antici-
pated at the outset of the program. Specifi-
cally, the following has been accomplished.
(1) Documented hexavalent chromium
emissions from sewage sludge incin-
erators.
(2) Documented nickel subsulfide emis-
sions from sewage sludge incinera-
tors.
(3) Developed a hexavalent chromium
sampling and analytical method.
(4) Developed a nickel speciation sam-
pling and analytical method.
(5) Provided additional metals data.
(6) Provided additional trace organics
data.
(7) Documented a correlation between CO
and THC.
(8) Documented that CO and THC con-
centrations can be reduced when the
plant has a CO and/or THC monitor to
improve combustion conditions.
(9) Demonstrated that the use of a wet
ESP is a viable retrofit option for signifi-
cantly reducing particulate and metals
emissions.
The full reports were submitted in fulfill-
ment of Contract No. 68-CO-0027 under
the sponsorship of the U.S. Environmental
Protection Agency.
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Table S. Semivolatile Emissions Summary for Outlet and Midpoint at Site 9
Concentration
Analyte
Phenol
1 ,4-Dichlorobenzene
Benzyl alcohol
1 ,2-Dichlorobenzene
4-Methylphenol
2-Nitrophenol
Benzole acid
1,2, 4- Trichlorobenzene
Naphthalene
4-Chloroaniline
2-Methylnaphthalene
4-Nitrophenol
Dibenzofuran
Phenanthrene
Fluoranthene
bis (2-Ethylhexyl)phthalate
OUT-MMP-7A
ND*
30.8
800
25.6
ND
196
2850
699
976
ND
43.4
ND
45.2
44.9
ND
29.2
MID-MM5-7
ND
33.4
1120
26.7
ND
284
3220
768
864
ND
45.5
ND
44.7
33.4
13.3
26.1
OUT-MM5-7C
176
ND
4100
ND
21.2
43.1
5090
ND
ND
ND
ND
97.4
ND
13.7
ND
ND
MID-MM5-7C
162
ND
3930
ND
20.6
76.4
4240
ND
ND
ND
ND
1440
ND
ND
ND
71.6
• m 68°F - 29.92 inches Hg.
*ND » Not detected; used as zero (0)
Table 6. Volatile Organics Emissions Summary
Concentration, ng/DSCM*
Sites
Venturi/Sc rubber
Outlet
Acrylonitrile
Vinyl Chloride
Methylene Chloride (m/z - 86)
Chloroform
1 .2-Dichloroethane
1, 1, 1-Trichloroethane
Carbon Tetrachloride
Trichloroethene
Benzene
Tetrachloroethene
Toluene
Chlorobenzene
Ethylbenzene
ND»
ND
108
16.8
ND
6.8
ND
5.2
6.2
9.4
7.7
ND
2.6
Site 9
Wet ESP
Outlet
1060
66.2
38.3
24.1
ND
17.5
ND
24.6
6390
29.0
4080
55.5
100
• - 68PF - 29.92 inches Hg.
"NDm Reportedas notdetected'orestimated'values;both expressed as zero
(0) in calculating totals and averages.
£u.S. GOVERNMENT PRINTING OFFICE: 1993 - 750-071/80005
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'illiam G. DeWees is with DEECO, Inc., Gary, NC27519, Robin R. Segall is with the Office of
Air Quality Planning and Standards, Research Triangle Park, NC 27711, Laurie Cone is with
Entropy Environmentalists, Inc., Research Triangle Park, NC 27709, and F. Michael Lewis is
with F. Michael Lewis, Inc., Mountain View, CA 94040.
arry E. Bostlan* and Eugene P. Crumpter** are the EPA Project Managers (see below).
w complete report consists of nine volumes entitled "Emissions of Metals, Chromium and
Nickel Species, and Organics from Municipal Wastewater Sludge Incinerators," Set Order
No. PB92-151 547; Cost: $232.00, subject to change).
"Volume I. Summary Report," (Order No. PB 92-151 554; Cost: $19.00, subject to change).
"Volume II. Site 5 Test Report • Hexavalent Chromium Method Evaluation," (Order No. PB
92-151 562; Cost: $19.00, subject to change).
"Volume III. Site 6 Test Report," (Order No. PB 92-151 570; Cost: $26.00, subject to
change).
"Volume IV. Site 6 Test Report - Appendices," (Order No. PB 92-151 588; Cost: $35.00,
subject to change).
"Volume V. Site 7 Test Report - CEMs Evaluation," (Order No. PB 92-151 596; Cost: $17.00,
subject to change).
"Volume VI. Site 8 Test Report," (Order No. PB 92-151 604; Cost: $26.00, subject to
change).
"Volume VII. Site 8 Test Report - Appendices," (Order No. PB 92-151 612; Cost: $43.00,
subject to change).
"Volume VIII. Site 9 Test Report," (Order No. PB 92-151 620; Cost: $26.00, subject to
change).
"Volume IX. Site 9 Test Report - Appendices," (Order No. PB 92-151 638; Cost $66.00,
subject to change).
ie above reports will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
le EPA Project Managers can be contacted at:
* Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
"(formerly with the Office of Water)
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle ParK, NC 27711
ted States
/ironmental Protection
jncy
Center for Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
icial Business
laity for Private Use $300
V600/SR-92/003
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