United States
Environmental Protection
Agency
Municipal Environmental
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-038 Apr. 1984
SERA Project Summary
Analysis and Assessment of
Incinerated Municipal Sludge
Ashes and Leachates
Thomas L. Theis, Margaret McKiernan, and Lawrence E. Padgett
Research was conducted to analyze
the physical and chemical properties of
ashes from incinerated municipal sludge
and of corresponding dewatered sludge.
Samples were gathered from 10 waste-
water treatment plants ranging in size
from 0.22 to 27.1 mVsec. These
samples were subjected to a series of
physical, chemical, and biological tests,
including batch and chemical extractions
and the Ames Salmonella assay.
Results showed that the addition of
supplemental chemicals during waste-
water or sludge treatment strongly
influenced the leachate properties and
composition of both dewatered sludge
and ash samples. Both iron(lll) and
aluminum salts acted to concentrate
trace metals, which were then readily
leached from the sludge ashes. The
addition of lime during treatment
elevated the ash and sludge pH values,
which determine the availability of
metals to the environment. In the
absence of inorganic chemical addition,
incineration acted generally to decrease
trace metal availability.
The behavior of arsenic during the
various leaching tests was the opposite
of that for metal cations with respect to
pH. Low pH values resulted in the
release of larger numbers of cations,
but arsenic release was usually greatest
at high pH values.
Incinerated sludges demonstrated
weak mutagenic activity in the Ames
assay. Four of the 10 ash samples gave
positive results, generally in the presence
of activating mammalian enzymes. In
addition, one dewatered sludge sample
also gave positive results. Both frame-
shift and base-pair mutagens were
implicated.
This Project Summary was developed
by EPA's Municipal Environmental
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
In the United States, slightly more than
4.5 million metric tons (5 million tons) of
municipal wastewater sludge solids are
produced yearly. This figure is expected to
increase to 6 million metric tons (6.6
million tons) per year by 1985. Presently,
some 30 percent of these solids are
thermally reduced in volume by incinera-
tion methods, the most popular of which
are the multiple-hearth and fluidized-bed
types. An average figure of 75 percent for
the volatile fraction of municipal sludge
yields about 338,000 metric tons (373,000
tons) of ash residue that m ust be disposed
of yearly. The most common disposal
methods are landfilling and lagooning.
Because of the initial cost and complex
operation of sludge incinerators, their
use is confined mostly to wastewater
treatment plants with capacities exceed-
ing 0.044 mVsec (1 MGD), most being
greater than 0.22 mVsec(5 MGD). Thus,
though the total quantities of ash
generated are not as great as other types
of combustion wastes, their disposal can
be a sizable operation on a local basis.
Handling the ash from both of the
commonly used incineration methods
often involves contact with water. In the
fluidized-bed system, the ash is removed
from the exit stream by a scrubber. For
the multiple hearth system, ash handling
can be either wet (for slurry pipelines) or
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dry. But even for dry handling, the ash is
usually conditioned for disposal with
water.
The purpose of this research was to
investigate the physical and chemical
properties of the ashes from a number of
incinerated municipal sludges and of the
corresponding dewatered sludges. Charac-
teristics that define the release of
inorganics were determined using single-
reagent leachate tests, and the effects of
organics were assessed through applica-
tion of the Ames Salmonella assay.
Experimental Methods
Representative samples of dewatered
sludge and incinerated sludge ash were
obtained from 10 municipalities. Analyses
for pH, moisture content (for dewatered
sludge only), and volatile matter were
made according to established methods.
Bulk composition for major and trace
elements was achieved through an HF-
aqua regia digestion procedure followed
by analysis with flame or flameless
atomic absorption spectrophotometry
(AAS). The method of additions was used
with deuterium arc background correction.
Dewatered sludge samples were further
treated with hydrogen peroxide (final
concentration 2 percent) to eliminate
interferences from organic matter. Anal-
yses for arsenic and selenium were made
by flameless AAS using the nickel
complexation method.
Three single reagent extraction tests
were used in this research: ASTM
Method A water shake extraction proce-
dure (ASTM-A), U.S. Environmental
Protection Agency (EPA) extraction
procedure (EP), and the International
Atomic Energy Agency (IAEA) leaching
test.
Ames assays were performed on a
number of inorganic and organic extrac-
tion procedures (Table 1). In tabulating
results, revertants were taken from the
linear portion of the dose-response
curve and were reported at the highest
concentration that was not toxic to the
bacteria. Ratios of diluted-to-original
samples ranged from 1:10 to 1:10,000.
Results
Pertinent information and basic data
characterizing the sludge ash and dewa-
tered sludge samples appear in Tables 2
and 3, respectively.
Except for sample number 10, each ash
sample produced an alkaline reaction in
distilled water. Samples 5,6, and 8, to
which lime was added at the treatment
facility, also displayed the highest pH
values. The pH of the dewatered sludge
Table 1. Extraction Procedures
Extraction
Type
Inorganic
(ASTM Method A.
neutral)
Inorganic
(acidic)
Inorganic
(acidic)
Inorganic
(near-neutral)
Inorganic
(basic)
Inorganic
(basic)
Inorganic
(acidic)
Inorganic
(IAEA method.
neutral)
Organic
(acidic)
Organic
(strong solvent)
Organic
(Soxhlet)
Organic
(Soxhlet)
Organic
Inorganic/ organic
(resin column)
Reagent
Double-
distilled
water
1.0 N
nitric acid
0.1 M
hydroxylamine
hydrochloride
in 0.01 M
HNOs
0.05 M
calcium
chloride
0.01 M
sodium
hydroxide
0.1 M
sodium
pyrophosphate
0.2 M
oxalic acid/
0.4 M
ammonium
oxalate
Double-
distilled
water
0.5 M
acetic
acid
Dimethyl
sulfoxide
95% Ethanol
Benzene
Acetone
Water/eluted
with acetone
Solution (ml)
Solid fgj Contact
Ratio Time Comments
4:1 48 hours Collects water-soluble
materials from the ash.
5:1 24 hours Collects strong acid-
soluble materials.
50.7 30 min. Dissolves Mn oxides.
1O:1 16 hours Releases easily-exchange-
able species.
1O:1 16 hours Dissolves Al oxides.
10:1 16 hours Dissolves Al oxides.
10:1 1 hour Dissolves oxides of
Fe andAI.
12:1 1 week Collects water-soluble
materials.
5:1 24 hours Collects weak acid-
soluble organics.
10:1 24 hours Collects organics.
and
1 week
20:1 12 hours Collects organics.
20:1 12 hours Collects organics.
4:1 1 week Collects organics.
4:1 48 hours Collects and concen-
trates organics.
is, without exception, lower than that of
the corresponding sludge ash. But this
result is to be expected since acidic
volatiles such as hydrogen sulfide and
carbon dioxide are driven off during
incineration.
Values for bulk elemental concentrations
of the ashes and dewatered sludges are
given in Tables 4 and 5, respectively.
Elevated values of iron, aluminum, and
calcium are evident in those locations
where ferric chloride, aluminum sulfate,
or lime were added. Though comparisons
of absolute mass conservation in Tables 4
and 5 are not valid since the samples
were gathered at different locations and
times in their respective treatment
schemes, the ash and dewatered sludge
concentrations do, nonetheless, correspond
generally on the basis of fixed solids.
Analyses for the elements arsenic,
cadmium, chromium, nickel, lead, and
-------
iblo 2. General Characterization for Sludge Ash Samples
Highest
Operating
Type of Temperature Disposal Physical
Sample Incinerator fC) Method Characteristics pH
1 Multiple
hearth
2 Multiple
hearth
3 Fluidized
bed
4 Multiple
hearth
5 Multiple
hearth
6 Multiple
hearth
7 Multiple
hearth
8 Multiple
hearth
9 Fluidized
bed
10 Fluidized
bed
925
760
760
980
840
870
925
760
730
790
Landfill
Landfill
Lagoon to
landfill
Lagoon to
landfill
Landfill
Lagoon
Lagoon
Landfill.
lagoon
occasion-
ally
Landfill
Landfill
Brown, 7.71
variable
Light brown, 8.81
very fine
Gray, very 7.94
fine
Brown, 8. 15
fine
Brownish-gray 9.81
intermixed
with fibrous
material
Dark brown, 1 2. 20
very fine
Reddish-brown 8. 79
variable
Brown, 11.72
fine
Black and 8.02
brown,
fine
Light brown. 5.89
fine
% Volatile Chemical
Matter Addition
0.28 Polymer,
picket
liquor
0.59 Fed*
Alum
0.89 Polymer
0.20 Polymer
5.85 Feds,
lime
0.49 Fed 3,
lime,
polymer
0.04 Polymer
0. 16 FeC/3
lime
polymer
1.35 Alum,
polymer
0.53 Polymer
Purpose of
Chemical
Addition
Sludge
conditioning
phosphorus
removal
Phosphorus
removal
Sludge
conditioning
Sludge
conditioning
Sludge
conditioning
Sludge
conditioning,
phosphorus
removal
Sludge
conditioning
Sludge
conditioning
phosphorus
removal
Sludge
conditioning
phosphorus
removal
Sludge
conditioning
Fe(HI) & Al
Added-mg as
FeC(3/g Dry
Sludge"
93.3
158.6
97.5
240.0
46.2
Chemical dosage normalized to a weight per weight basis of dried sludge solids, regardless of the manner.
,'lenium in the ASTM-A shake test were
niformly low (frequently at or near the
Jtection limit), and they are not summarized
ere. This test is buffered by protolysis
(actions that occur at the surface of the
}lid material. Thus, the pH during the
at remains close to those values given
i Tables 2 and 3—that is, in the neutral to
Ikaline range. In addition, the ionic
rength is generally low (though uncon-
•olled). Neither of these conditions
romotes the release of surface-bound
letal species.
Results for both ash and sludge
amples in the EP test appear in Table 6.
:omparison of Table 6 with Tables 2 and
reveals that the leachability of all
lements studied in the EPA-EP appears
3 depend strongly on the earlier addition
f iron(lll) and/or aluminum salts to the
vastewater during treatment or to the
sludge for conditioning. Table 7 summa-
rizes the important trends in terms of
average values extracted for both ashes
and sludges. The correlation with iron(lll)
and aluminum addition and the amount
of metal cations released is a direct one.
For arsenic, which has an anionic
aqueous chemistry, an inverse relation-
ship exists. At pH 5, the most common
forms of iron and aluminum oxides
possess positively charged surfaces,
implying that the proton can successfully
compete for surface sites against trace
metal cations. Under these conditions,
however, arsenic (existing most probably
as arsenate or arsenite) will be electrosta-
tically attracted to the surface. Attractive
chemical forces may also exist. An ad-
ditional feature of the data is that (ex-
cept for cadmium) incineration acts to in-
crease the leachability of cation elements
if iron(lll) and/or aluminum(lll) salts have
been added. For arsenic and cadmium,
incineration decreases their leachability.
If these salts are not added, cat ionic
elements are generally less teachable in
the ash than the sludge.
A summary of the IAEA leaching test
results appears in Table 8. This test was
performed on six ash samples only. The
data show a trend toward greater metal
release for those ashes obtained from
treatment facilities that use iron or
aluminum salts (samples 5, 8, 9). Again,
an inverse relationship exists for arsenic,
which has an anionic aqueous chemistry.
The amount of a given metal released
was found to change as the test proceeded,
revealing some interesting trends. Figure
1 shows detailed IAEA release data for
ash Sample No. 1. Changes in concentra-
tion for the indicated metals are shown
-------
Table 3. General Characteristics for Dewatered Sludge
Flow to Dry Sludge
Treatment Produced
Plant
Sample (MGD)
1 615
2* 36
3 6
4 163
5" 53
6" 18
7 8
8b 18
9° 5
10 5
a FeC/i, alum added.
" FeC/3. time added
0 Alum added.
" Portion of ash is recycled as
' Anaerobically digested.
(Metric Tons
Per Day)
435
24
6.1
136
27
18
4.4
16
9.3
3.2
Color
Black
Dark
brown
Dark
brown
Dark
brown
Gray
Black
Black
Dark
brown
Black
Black
Samples
% Solids
18.2
37.8
35.1
33.1
24.1
21.1
15.8
29.2
16.0
17.0
% Volatile
Content
54.6
68.4
60.0
30.1"
62.5
43.2
69.1
30.8*
52.2
75.6
pH
4.95
5.43
5.73
5.79
7.17
6.53
5.38
7.23
5.91
5.24
a dewatering aid.
along with pH, which rises sharply during
the test (probably because of the exposure
to solution of a base deposit). Though the
metal cations chromium and cadmium
show gradual declines with increasing
pH, arsenic release rises. As suggested
earlier, such behavior would be expected
as the surface assumes a negative charge
at the high pH. Trends similar to those of
Figure 1 were also found for other ash
samples. Such changes during the IAEA
test suggest a rather nonuniform distri-
bution of major and minor elements, both
on the surface and as a function of depth
in the ash.
In the Ames test, the extraction
procedures that resulted in the greatest
number of positives were those designed
to extract nonpolar organic compounds.
or to concentrate them, or both. Table 9
summarizes these results. Four of the ten
ashes gave positive results using the
Ames criteria of induced reversions
greater than two times the spontaneous
reversion rate, with one or more extractants.
In addition, one dewatered sludge (Num-
ber 5) was tested and also gave positive
results. Most positives were found in the
presence of the activating mammalian
enzymes, suggesting that the compounds
responsible for the positive results are in
a promutagenic form. In addition, strain
Table 4.
Sample
1
2*
3
4
5"
6b
7
5b
9C
10
Bulk Concentration of Metals
Al As Ca
34800
35600
64000
75000
38000
9200
38000
29200
10800O
22800
3.7
1.2
1.7
3.7
8.1
20.1
2.7
20.8
1.3
1.8
74000
146000
68000
102500
118000
380000
90000
245500
58500
80000
in Sludge Ash ffjg/g dry wt.)
Cd Cr Cu Fe
270
21
900
190
9
4
7
5
14
45
6560
2200
810
4800
1670
350
2060
1150
870
350
4700
3200
3300
6000
4900
1500
5500
3600
7000
4500
305000
82000
50000
62000
101000
1 71 700
82500
17900O
41300
40700
Hg
8.4
8.8
3.1
5.0
7.0
4.5
9.2
9.0
5.8
2.0
K
6600
6600
8800
6500
3800
800
7400
2700
23000
3900
Mn
2000
5500
2500
WOO
800
500
5000
4300
1800
5000
Na
10900
24600
25800
19400
29900
16100
28OOO
8700
265000
13500
Ni
3900
840
880
1230
1200
690
670
1700
980
270
Pb
1190
760
1070
2080
1620
90
23O
1650
16OO
910
Se
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
Zn
10700
4400
6000
15100
9OOO
900
6400
8OOO
23800
4000
" FeCIs, alum added.
b Feds, lime added.
c Alum added.
Table 5. Bulk Concentration of Metals in Dewatered Sludge Samples (jg/g dry wt.
Sample
As
Cd
Cr
Fe
Ni
' FeCIs, alum added.
" FeCIa, lime added.
c Alum added.
Pb
Se
7
2°
3
4
5"
6"
7
8*
5C
10
0.5
0.4
0.5
0.8
1.6
4.1
0.5
2.0
0.4
0.4
120
7
250
90
4
1
3
2
5
18
2230
820
440
3500
340
80
420
560
380
90
168.500
21,200
19,200
47,300
44,000
78.900
21.200
131,000
21,100
9,500
950
140
190
840
230
130
140
930
210
80
430
240
480
1O40
530
20
70
1090
420
240
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
<4.0
responsiveness verifies the increased
sensitivity of the R factor strains TA 98
and TA 100 over the original strains TA
1538 and TA 1535. These two strains
produce the greatest number of positives,
indicating that mutagens in the samples
can induce both base pair and frameshift
mutations.
The full report was submitted in
fulfillment of Grant No. R-806690-01 by
the University of Notre Dame under the
sponsorship of the U.S. Environmental
Protection Agency.
-------
'able 6.
Sample
1
2a
3
4
5"
6"
7
5"
5C
10
Percentage of Elemental Extractions in the EPA EP
As
17.5
1.7
14.5
13.5
1.6
2.3
15.0
3.9
1.5
2.8
Cd
.4
2.4
1.O
1.1
13.8
17.5
5.0
5.O
2.5
0.6
Ash
Cr
0.1
.4
.1
.01
.9
6.4
.03
1.3
.1
.01
Test"
Dewatered Sludge
Ni
0.4
85.6
0.8
0.3
79.0
59.1
51.5
12.1
80.2
1.6
Pb
.3
.2
.2
.2
.2
4.5
0.8
.1
.1
.1
As
15.7
10.0
4.0
20.0
5.2
.5
9.8
1.5
5.0
7.5
Cd
3.9
4.7
1.8
2.1
33.8
51.0
6.7
26.5
6.4
2.1
Cr
1.13
.05
.8
.2
.3
1.9
.1
2.8
.3
.1
Ni
13.7
15.1
3.7
27.3
78.1
30.0
15.5
44.9
54.0
51.6
Pb
.4
.6
.2
.04
.04
.7
1.0
.1
.2
.3
FeCla. alum added.
FeC/a, lime added.
Alum added.
Computed as a percentage of total concentration.
'able 7. Average Percent Removed in EPA-EP Test for Ash and Sludge
Ash Sludge
Element
As
Cd
Cr
Ni
Pb
Added
2.2
8.2
2.0
63.2
1.0
FeflllJ/AI
Not Added
12.6
1.6
0.03
10.9
0.3
Added
4.4
24.5
0.8
43.6
0.3
FefllH/AI
Not Added
11.5
3.3
0.3
21.2
0.4
'able 8. IAEA Leaching Test Results for Sludge Ash Samples (Total Percent Extracted)
Sample As Cd Cr Ni Pb
1
3
4
5
8
9
60.2
54.0
24.0
5.0
2.8
17.5
O.O8
0.01
0.04
0.7
0.2
0.8
0.01
0.03
.
0.2
0.1
0.07
0.01
-
-
0.03
-
0.03
_
0.02
0.02
0.02
0.02
0.02
-------
25
20
15
£ 10
2
i
o
IAEA
Ash No. 1
10.0
9.0
8.0
Q.
7.0
6.0
5.0
2 4 6 8 10 12 14 16 18
Number of Equilibration Periods
Figure 1. IAEA leaching test for sludge ash Sample No. 1.
20 22
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'able 9. Positive Results of Test Extractions Using the Ames Positive Determination Method
Activation
'ample Source _ Extraction _ Strain (+/-)
Valdwick ash
'ort Huron
sh
idianapolis
sh
ersey City
sh
srsey City
udge
DMSO
Ammonium
oxalate
Acetonez
(50 g ash)
Soxhlet
benzene
Resin
column
Resin
column
DMSO
Cadi
H£> {IAEA)
Ammonium
oxalate
Soxhlet
benzene
Acetone-i
(25 g ash)
Acetonez
(50 g ash)
Resin
column
Acetone ^
(25 g sludge)
Acetonez
(50 g sludge)
Resin
column
98 +
1535 +
1537 +
100 +
7535 +
1537 +
1537
1537
100
1535 +
1535 +
7537 +
98
98 +
7537 +
1538 +
98 +
98 +
98 +
100
1537 +
1538 +
95 +
35 + -
7535 +
7535 +
95 + -
700 + -
7535 +
7537 +
7535 +
-------
Thomas L Theis, Margaret McKiernan, and Lawrence E. Padgett are with the
University of Notre Dame, Notre Dame, IN 46556.
A. E. Eralp is the EPA Project Officer (see below).
The complete report, entitled "Analysis and Assessment of Incinerated Municipal
Sludge Ashes and Leachates, "(Order No. PB 84-155 563; Cost: $13.00, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES P,
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
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REGION V tPA
LIBRARIAN
230 b DfcAKbUHN ST
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* U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/911
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