United States
                     Environmental Protection
                     Agency
Environmental Sciences
Research Laboratory
Research Triangle Park NC 27711
                     Research and Development
EPA-600/S3-84-047  May 1984
&EPA          Project  Summary
                     Chemical  and  Physical
                     Characterization  of  Municipal
                     Sludge  Incinerator  Emissions

                     Roy L. Bennett, Kenneth T. Knapp, and Donald L. Duke
                       Particulate emissions from a group of
                     municipal  sludge  incinerators,  three
                     with multiple-hearth furnaces and one
                     with a  fluidized-bed furnace,  were
                     characterized in a study covering a
                     period from October 1,1979 to June 30,
                     1981. Objectives of the  investigation
                     were (1) to obtain specific elemental
                     emission concentrations, and (2) to pro-
                     vide source inventories and source sig-
                     natures, especially in terms of particle
                     size, that would assist in developing and
                     evaluating source apportionment mod-
                     els. Three of the plants investigated in
                     this study operated at or near auto-
                     genous burning conditions. Chemical
                     element composition was determined
                     for total and sized emission samples by
                     x-ray fluorescence  analysis. During the
                     study, considerable enrichment of sev-
                     eral elements (S, V, Cu, Zn, Cd, Sn and
                     Pb) in the emissions, compared to their
                     content in  the sludge feed, was ob-
                     served. The largest average enrichment
                     ratios were found  with cadmium (31),
                     zinc (14), lead (9), and sulfur (8).
                       Th/s Project Summary was developed
                     by EPA's Environmental Sciences Re-
                     search  Laboratory, Research  Triangle
                     Park, NC, to announce key findings of
                     the research project that is fully docu-
                     mented in a separate report of the same
                     title (see Project Report ordering infor-
                     mation at back).

                     Introduction
                       With  the  production  of municipal
                     wastewater sludge on a definite increase, an
                     attendant increase is  expected in the use of
                     incineration for sludge disposal  manage-
                     ment. A characterization study was con-
                     ducted on paniculate emissions from the
stacks of a group of municipal sludge in-
cinerators, three with multiple-hearth fur-
naces and one with a fluidized-bed furnace.
One purpose of the investigation was to pro-
vide information on the concentration of
chemical elements, especially heavy metals
such as cadmium (Cd) and lead (Pb), in the
emissions. A related objective focused on
obtaining source emission factors and source
signatures to help develop and  validate
source apportionment models.
  These investigations involved the collec-
tion of representative emission samples for:
(1) particulate mass emission determination;
(2) chemical characterization; and (3) parti-
cle size determinations, for both mass emis-
sions  and  individual  chemical element
emissions. Sulfur dioxide and sulfuric acid
emissions were determined; the gaseous
concentrations of hydrocarbons and nitrogen
oxides were monitored; and a few samples
were collected to determine the emissions
of high molecular weight  organic com-
pounds. At each incinerator, samples of the
feed sludge were collected and analyzed. In-
formation on operating conditions at the four
incinerator facilities during the test periods
are shown in Table 1.

  At each incinerator, the sludge was pre-
conditioned thermally with the hot exhaust
gases from the furnaces to produce a higher
solids sludge cake for better burning. At the
multiple-hearth  Incinerator 0, this process
was carried to  the point of positive heat
balance, resulting in autogenous burning.
Some supplemental fuel was burned at all
of the sites. At Incinerator 0 a total of only
16 gal of fuel oil was burned. This burning
occurred during the final two 29-h sampling
periods, and was carried out for shut-down
purposes. The remainder of the time  the

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Table 1.    Furnace Types, Control Systems, and Sludge Loadings of Tested Incinerators
Site
designation
0
P
Q
R
Furnace type
Seven-chambered multiple-
hearth
Eight-chambered multiple-
hearth
Fluidized-bed
Seven-chambered multiple-
hearth
Control equipment
Wet, tray-type scrubber
Wet, tray-type scrubber
Wet, tray-type scrubber
Single pass cyclone
scrubber
Average load
of unit tested
kg/h (dry)
1940
1740
839
1890
Sludge
percent moisture
63.5
49.3
66.2
71.3
sludge burned autogenously, combusting on
its own with no need for supplemental fuel.
At Incinerator P an average of 40 ft3/h of
natural gas was burned. The supplemental
fuel oil at Incinerator Q ranged from 0 to 64
gal/h and averaged 17 gal/h over the three-
day  test period.  Incinerator  R  was not
designed for autogenous  combustion and
never reached this condition. An average of
40 gal/h of fuel oil was consumed.

Experimental

Sampling  Procedures
  A standard U.S. Environmental Protection
Agency (EPA) Method 5 sampling train was
used to collect particulate samples for deter-
mining mass emission rates. The impingers
were adapted for use in determining gaseous
sulfur oxides by EPA Method 8. The first im-
pinger contained  150 ml  of 80% isopro-
panol, which was followed by a high-purity
glass wool  plug inserted in the U-tube be-
tween the first and second impingers. The
second  and third impingers contained 100
ml each of 3% hydrogen peroxide solution;
the fourth impinger was filled with approxi-
mately 400 g of indicating silica gel. Prior to
sampling, a velocity profile of the duct at the
sampling location was determined through
transversing with a Pitot tube system. A 5-ft
heated,  Pyrex-lined probe was used to col-
lect all Method 5 and Method 8 samples at
a  single point  determined to  have the
average velocity of the flue gas within the
duct.
  Samples used for chemical characteriza-
tion  by  x-ray fluorescence analysis (XRF)
were collected with a modified Method 5
train in which the conventional sample box,
filter holder, and glass impingers were re-
placed by an  EPA-designed heated sample
box housing a stainless steel filter holder for
47-mm filters. The particulate characteriza-
tion samples were collected in sets consisting
of two  Gelman A glass fiber filters, two
Millipore AA, one Nuclepore 0.8-^im filter,
and six  Teflon 0.2-^m filters. To  provide a
variety of loadings on the filters,  sampling
periods  ranged from 15 sec to 10 min. In all
cases, an attempt was made to sample iso-
kinetically.  Collections  on all filters were
analyzed by XRF.
  University of Washington Mark III cascade
impactors were used to collect samples for
measuring the particle  size distribution  of
total mass emissions, as well as individual
chemical element emissions. The impactor
samples were taken in-stack at the point of
average gas velocity; this same  sampling
point was used for the characterization sam-
pling. Samples were collected isokinetically,
with a sampling rate between 0.5 and 0.75
ftVmin through the impactor.
  Composite pre-burn sludge samples and
post-burn ash were collected  at  all in-
cinerators except at the fluidized-bed unit,
where only sludge samples were taken. The
sludge samples were heated to 600C for 30
min to remove the volatile contents prior to
chemical analysis.

Analytical Methods
  Elemental  contents of the  emission
samples, as well as of the sludge and ash
samples, were determined with a Siemens
MRS-3 multi-channel wavelength dispersive
x-ray fluorescence  spectrometer.  The
Siemens MRS-3 has  15 fixed  wavelength
monochromators and  a scanning channel
that  allows  analysis  for  11  additional
elements.

Results and Discussion

Sludge Content
  The elemental composition of the ashed
sludge feed material, determined by XRF, is
shown in Table 2. The values represent the
averages for four to six composite samples
taken during  two- to  three-day  testing
periods at each incinerator.

Elemental Emissions
  The mean concentrations of the elements,
determined by XRF, in the emissions from
the four plants are shown in Table 3. The
Table 2.    Elemental Composition (Percent) of Municipal Wastewater Sludge
Element
Na
Mg
Al
Si
P
S
Cl
K
Ca
77
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
As
Se
Br
Cd
Sn
Sb
Ba
Pb
Sitt
AV
1.0
1.8
34
W.I
64
0.93
0.45
13
17.
084
0.03
0.22
070
67
0.01
003
0 12
0.30
<03
<0.04
<005
002
0.30
0.03
025
034
> O
SD
0.09
0.08
0.28
0.46
0.44
0.15
0.01
0.09
0.62
0.06
0.01
0.02
0.11
1.0
0.003
0.01
0.02
0.04



0.005
0.02

0.02
0.13
Sitt
AV
0.7
1.0
3.6
13.0
4,4
13
008
1.1
6.2
0.76
0.04
0.50
0.23
17
0.03
0.14
0.75
1.1
<0.3
<004
<0.05
0.04
0.25
0.02
0.41
0.48
; P
SD
011
0.17
047
3.3
0.22
0.41
0.18
024
1.2
0.05
001
0.27
0 11
79
002
0.08
043
008



0.05
0.03
0.004
0 11
0.18
Site
AV
<0.6
0.87
4.0
170
4.1
0.82
<0.5
1.2
7.5
0.77
0.03
0.22
0.34
7.6
0.01
0.06
0.27
1.0
<0.03
<0.04
<0.05
0.08
0.25
0.01
0.45
0.59
> Q Site R
SD

0.13
0.23
2.7
0.13
046

0 15
1.0
0.04
0.01
0.24
0.12
6.4
0.02
0.07
0.37
0.07



0.04
0.03
0.001
0.04
0.25
AV
<0.2
0.92
5.2
12.0
3.7
047
0.68
1.1
9.8
1.18
<0.01
0.38
0.11
5.4
0.01
0.06
0.44
1.4
<0.03
<0.04
<0.05
003
0.19
001
027
023
SD

0.03
0.14
0.34
0.12
0.06
0.19
0.02
0 15
0.04

0.02
0008
0 10
0.002
0008
002
003



0.005
0.006
0.001
0.01
0.03
Avg. Content
16 cities la)
0.44
0.60
1.83

1.56

038
1 22
3.62
023
0.004
0.14
0.019
3.06
0001

0,13
0.21
0.0014
0.0003
0.005
0.010
0.022
0.001
0.06
0.18
lat Furr, A.K., A.W. Lawrence, S S C. Jong, M.S. Grandolpho, R.A. Hofstader, C.A. Bache, W.H. Gutenmann,
   and D J. Lisk, Environ. Sci. Techno/., 10,683,  1976

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 Table 3.    Mean Concentrations of Elemental Emissions Ing/Nm3) from
           Municipal Sludge Incinerators

                   Site O        	 S/te P           Site Q
     Element
                                                     Site R
AV
        SD
                 AV
                         SD
                                 AV
                                          SD
                                                  AV
                                                           SD
Na
Mg
Al
Si
P
S
Cl
K
Ca
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
As
Se
Br
Cd
Sn
Sb
Ba
Pb
350
90
128
590
590
660
230
210
780
28
~35
97
27
370
<6
<22
85
810
<29
~45
~49
42
180
6
10
510
110
32
47
100
120
300
90
90
170
12

39
13
80


29
220



15
51
2
4
190
290
440
1570
4180
1730
930
130
460
2620
450
38
480
82
7070
25
125
810
1840
<29
20
57
34
1230
23
290
1170
230
550
1980
4826
1890
410
110
500
2660
460
14
330
30
8170
a
121
690
1240

3
19
15
450
7
280
530
100
51
160
270
210
730
47
54
440
33
9
14
23
228
<6
<22
14
87
<29
18
39
7
30
<2
20
114
50
18
48
80
69
270
65
22
150
10
2
8
8
71


4
28

17
17
2
9

7
65
240
21
37
620
570
2610
1990
120
160
16
<6
230
10
230
<6
<22
520
1830
<29
26
170
1890
790
43
14
2140
170
6
20
290
350
910
2280
110
88
21

106
1
145


310
1650

1
140
1410
640
40
15
1880
 relative standard deviation of the samples
 analyzed  (between 45 and 95 samples per
 site) to obtain each of these concentrations
 averaged  33%, 72%, 32%  and 68% for O,
 P,  Q  and  R,  respectively.  The greater
 variability of P and R reflect the wider range
 of operating conditions, e.g., the rates of
 feed and  stack gas flow during the testing
 oeriods.   It  is apparent immediately that
 elements  such  as Zn, Cd, and  Pb had a
 higher concentration in the emissions than
 would have been expected based solely on
 their concentration in the sludge. Enrichment
 factors, calculated by dividing the concen-
 tration in the total paniculate emission by the
 concentration in  the sludge,  are listed in
 Table 4. Conditions causing enrichment are
 volatility  and interaction  of  the volatile
 elements with the extremely fine particles not
 efficiently removed by scrubbers.
Total Particulate Mass and
Sulfur Oxides
  The emission rates and concentrations of
paniculate mass, sulfur dioxide and sulfuric
acid were obtained from the Method 5 and
Method 8 tests run afte'r the scrubber outlets.
Lowest paniculate emissions were observed
at the fluidized-bed incinerator, Q. Highest
sulfur oxide emissions were found at In-
cinerator R, presumably due to the sup-
plementary  fuel oil  burned  to maintain
combustion.
                            Particle Size Distribution
                              The average mass median diameters ob-
                            tained from the particle size distribution
                            measurements were 0.28, 0.30,1.1 and 0.85
                            u,m at Incinerators 0, P, Q and R, respec-
                            tively. Individual size distributions for several
                            elements, as well as the total mass distribu-
tion, are shown in Figure 1.  For convenience,
the largest and smallest size fractions have
been assigned finite values. The Zn distribu-
tion, predominantly submicrometer particles,
was characteristic of that of S, Cd, Pb, and
other elements exhibiting enrichment in the
emissions, probably due to their volatility in
the furnace. Phosphorus exhibited a group
of mid-range particles around 2 ^m. Iron was
distributed through all sizes, with a signifi-
cant fraction of large particles evident even
in the controlled, post-scrubber emissions.
Only a small fraction of the total mass was
greater than 2 ^m (see Figure 1).
  At Incinerator  R  panicle  size measure-
ments were also made before the scrubber.
Figure 2 shows the distribution at the scrub-
ber  inlet, where  large  particles were
preponderant;  however, a second mode oc-
curred  near 2 urn and at the scrubber outlet,
where the mass concentration of the smaller
particles predominated because of the scrub-
ber's more efficient removal of larger  par-
ticles.   Evident   in  these  pre-scrubber
measurement is the contrast in the distribu-
tion of a more volatile element such as Cd
with that of calcium (Ca) (see Figure 2).

Conclusions
  The  more volatile elements,  Cd,  Pb and
Zn, were  enriched in the  emissions. Cad-
mium had the highest average enrichment
ratio, with a 31-fold increase in the emis-
sions. The average mass median diameters
for the particles emitted at all four sites were
small, ranging from 0.28 urn to 1.1 ^m. Few
                            Table 4.    Enrichment Ratios of Elements in Emissions Relative to
                                       Content in Sludge
Incinerator
Element
Na
Mg
Al
Si
P
S
Cl
K
Ca
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Br
Cd
Sn
Sb
Ba
Pb
0
2.76
0.42
0.30
0.46
0.73
5.64
4.00
1.32
0.36
0.26
9.33
3.50
0.30
0.43


5.67
21.47
_
16.50
4.73
1.67
0.32
11.97
P
0.81
0.86
0.85
0.63
0.76
1.38
0.63
0.81
0.82
1.16
1.75
1.88
0.70
0.81
1.67
1.71
2.11
3.25
_
7.0
9.56
2.50
1.36
4.70
Q
	
1.16
0.78
0.31
1.01
17.6
_
0.89
1.16
0.84
6.0
1.27
1.35
0.59


7.0
28.7
7.7
1.6
2.36

0.89
3.83
Ft
, 	
0.03
0.01
0.08
0.23
8.14
4.28
0.16
0.023
0.02
_
0.87
0.10
0.06

_
1.75
1.89
_
98.9
6. JO
4.6
0.07
13.65
Average
enrichment
	
0.38
0.49
0.37
0.68
8.19
2.97
0.80
0.59
0.62
5.69
1.88
0.61
0.54
	
	
4.13
13.83
	
31.
5.68
2.92
0.66
8.53

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5
4

3
2
n~^
1 '
Q 0
o1 1 00
<
<075
050
n ?f\

0.00
0




1


I-
-



;
I



0.2
1






02




O.i
1






0.5




- 7
'






1




2
1






2

/












4. Zin

i i
5 /C
' '
C Iro





5 1C




) 20
1






) 20


-

5


-
-



5




3 C







OC

.
-

? 7

-

-



7




02







0.2



	
0.5







0.5




;







1




2





1 	 1

i

B. Phosphorus
_
	
5 70 20 5C
i i i
D7/i tftl

-



5 10 20 5C
u./o
0.50
0.25
n nn

35
30
25
20
15
10
5
Q
)
Figure 1.
     Diameter, D (um)                         Diameter, D (um)

Particle size distribution of zinc, phosphorus, iron, and total paniculate emissions
from Incinerator 0.
particles were larger than 2 u.m. The volatile
elements were found predominantly in the
submicrometer range.
  The enrichment of Cd (especially relative
to that of Zn) is much greater at Incinerator
R than at the other facilities. A contributing
factor to  this higher  enrichment  is Cd's
greater  predominance in small particles, as
well as  the lower  efficiency of the control
device.  Incinerator R has a wet, single-pass
scrubber system that is considerably less ef-
ficient for submicrometer  particle removal
than  scrubbers  at the other  incinerators.
Elemental particle size measurements at In-
cinerator R before the scrubber inlet showed
that 72% of the Cd was associated with par-
ticles smaller than  1 pirn (see Figure 2). Only
28% of the Zn was associated with this size
range.
                                                40

                                                35
                                               ~\	1	1	1	1	r
                                                    A. Cadmium
                                                       Scrubber Inlet
B.
   Calcium
   Scrubber Inlet
                                                                                                                    75
                                                  0.1 0.2   0.5  1    2    5  10  20
                                                               Diameter, D (u)
                                                                          500.1 0.2   0.5   1   2     5   10  20   50
                                                                                           Diameter, D (urn)
                                             Figure 2.    Particle size distribution of cadmium, calcium, and total paniculate mass before the
                                                          scrubber and total paniculate emission after the scrubber at Incinerator ft.

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      The EPA authors, Roy L. Bennett (also the EPA Project  Officer, see below),
       Kenneth T. Knapp,  and Donald L. Duke are with Environmental Sciences
       Research Laboratory, U.S. Environmental Protection Agency, Research Triangle
       Park. NC 27711.
      The complete report,  entitled "Chemical and Physical  Characterization of
       Municipal Sludge Incinerator Emissions," (Order No. PB 84-169 325; Cost:
       $10.00, subject to change) will be available only from:
             National Technical Information Service
             5285 Port Royal Road
             Springfield, VA22161
             Telephone: 703-487-4650
      The EPA Project Officer can be contacted at:
             Environmental Sciences Research Laboratory
             U.S.  Environmental Protection Agency
             Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
                                                   ''t 1
                                                                                  ft U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/947

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