Air Pollution
Aspects of
Sludge Incineration
EPA Technology Transfer Seminar Publication
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EPA-625/4-75-009
AIR POLLUTION ASPECTS
OF SLUDGE INCINERATION
ENVIRONMENTAL PROTECTION AGENCY* Technology Transfer
June 1975
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ACKNOWLEDGMENTS
This seminar publication contains materials prepared for the
U.S. Environmental Protection Agency Technology Transfer Program
and has been presented at Technology Transfer design seminars
throughout the United States.
A portion of this publication appeared originally in the
Technology Transfer Process Design Manual for Sludge Treatment
and Disposal. Additional information included was prepared by
Gordon Cuip, representing Culp, Wesner, CuipClean Water
Consultants, Eldorado Hills, Calif.
NOTICE
The mention of trade names or commercial products in this publication is
for illustration purposes, and does not constitute endorsement or
recommendation for use by the U.S. Environmental Protection Agency.
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CONTENTS
Page
Introduction
1
Particulate Matter .
. . . .
1
Metals
8
Gaseous Pollutants .
9
Organics
10
Conclusions . . . .
11
Case Histories . . .
11
Livermore, Calif.
11
Palo Alto, Calif.
12
References . . . .
12
111
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I NTRODUCTION
Incineration offers the opportunity to reduce sludge to a sterile landfill and remove offensive
odors, but it also has the potential to be a significant contributor to the air pollution problem in an
urban community. The quantity and size of particulate emissions leaving the furnace of an
incinerator vary widely, depending on such factors as the sludge being fired, operating procedures,
and completeness of combustion. Incomplete combustion can form objectionable intermediate
products, such as hydrocarbons and carbon monoxide. There is also the potential for discharge of
air pollutants such as sulfur dioxide, nitrous oxides, and metals such as mercury.
PARTICULATE MATTER
New Source Performance Standards (NSPS) regulating discharges from municipal sludge incin-
erators have been promulgated by the Environmental Protection Agency (EPA). These standards
limit the discharge of particulate matter from both new and modified sewage sludge incinerators.
The process weight and opacity restrictions placed on this atmospheric pollution source are: 1
No more than 0.65 g/kg dry sludge input (1.30 lb/ton dry sludge input).
Less than 20 percent opacity. Visible emissions caused solely by the presence of uncom-
bined water are not subject to the opacity standard.
Available data indicate that, on the average, uncontrolled multiple-hearth incinerator gases con-
tain about 0.6 grain of particulate per standard cubic foot of dry gas. 2 Uncontrolled fluid-bed reac-
tor gases contain about 1.0 grain of particulate per standard cubic foot. 3 For average municipal
wastewater sludge, these uncontrolled pollutant concentrations correspond to about 33 pounds of
particulates per ton of sludge burned in a multiple hearth, and about 45 pounds of particulates per
ton of sludge burned in a fluid-bed incinerator. Particulate collection efficiencies of 96 to 97 per-
cent are required to meet the NSPS, 4 based on the above uncontrolled emission rate.
Sludge incinerators differ from most other types of incinerators in that the sludge does not nor-
mally supply enough heat to sustain combustion. Furthermore, there is less emphasis on retaining
ash in the incinerator and much of it is discharged in stack gases. Particulate emissions to the atmos-
phere are almost entirely a function of the scrubber efficiency and are only minimally affected by
incinerator conditions. Sludge incinerators in the United States are equipped with scrubbers of vary-
ing efficiency. These scrubbers range from simple spray-tower-type units to venturi-type scrubbers
with pressure drops up to 40 inches of water.
Existing State or local regulations in the United States tend to regulate sludge incinerator emis-
sions through incinerator codes or process weight regulations. 5 Many State and local standards are
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Table 1 .Sludge incinerator facility A : Summary of results
Item
Run number
Average
1
2
3
Date 1-11-72 1-12-72 1-12-72
Test time, minutes 108 108 108 108
Furnace feed rate, ton/h dry solids 0.550 0.560 0.560 0.557
Stack effluent:
Flow rate, dscfm 2,880 2,550 2,660 2,700
Flow rate, dscf/ton feed 314,000 273,000 285,000 291,000
Temperature,°F 59 59 59 59
Water vapor, volume % 1.93 1.92 2.23 2.03
C0 2 ,volume%dry 12.8 12.6 11.5 12.3
0 2 ,volume%dry 4.8 4.7 6.4 5.3
CO. volume % dry 0 0 0 0
SO 2 emissions, ppm <0.3 <0.3 <0.3 <0.3
NOx emissions, ppm 4.2 5.7 6.4 5.4
HCI emissions, ppm <3.8 <2.9 <4.1 <3.6
Visibleemissions,%opacity <10 <10 <10 <10
Particulate emissions:
Probe and filter catch:
gr/dscf 0.024 0.005 0.004 0.011
gr/acf 0.023 0.005 0.004 0.011
lb/h 0.583 0.116 0.099 0.266
lb/ton of feed 1.06 0.207 0.177 0.48 1
Total catch:
gr/dscf 0.032 0.007 0.010 0.0163
gr/acf 0.031 0.007 0.010 0.016
lb/h 0.779 0.160 0.227 0.389
lb/ton of feed 1.42 0.286 0.405 0.704
Note.dscfm indicates dry standard cubic feet per minute; dscf indicates dry standard cubic feet; acf indicates actual cubic
feet.
Source: Background Information for Proposed New Source Performance Standards, EPA Report APTD-1 3526, June 1973,
vol. 2, appendix.
corrected to a reference base of 12 percent carbon dioxide or 6 percent oxygen. Corrections to
CO 2 or 02 baselines are not directly related to the sludge incineration rate, because of the high per-
centage of auxiliary fuel required. In some regulations, the CO 2 from fuel burning is subtracted from
the total when determining compliance.
2
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Table 2.Sludge incinerator facility A 2 : Summary of results
Item
Run number
Average
1 2
3
Date
5-3-7 1
5-4-71
5-4-71
Test time, minutes
60
60
60
60
Furnace feed rate, ton/h dry solids
0.325
0.325
0.325
0.325
Stack effluent:
Flow rate, dscfm
3,480
3,600
3,320
3,470
Flow rate, dscf/ton feed
642,500
664,600
612,900
640,600
Temperature, °F
80
80
78
79
Water vapor, volume %
3.4
3.4
3.4
3.4
CO 2 . volume % dry (less auxiliary fuel)
4.0
5.1
4.0
4.4
SO 2 emissions 1
Visible emissions, Ringelmann No. 2
<1
<1
<1
<1
Particulate emissions, total catch:
gr/dscf (corresponds to 12% C0 2 )
0.020
0.031
0.048
0.033
gr/acf
0.019
0.029
0.047
0.032
lb/h
0.596
0.956
1.365
0.972
lb/ton of feed
1.84
2.94
4.20
2.99
1 No SO 2 detected.
2 Opacity was not recorded.
Note.Tested by local agency using code method 1. Probe and filter catch not analyzed separately. dscfm indicates dry
standard cubic feet per minute; dscf indicates dry standard cubic feet; acf indicates actual cubic feet.
Source: Background In formation for Proposed New Source Performance Standards, EPA Report APTD-1 3526, June 1973,
vol. 2, appendix.
In developing the foregoing NSPS, tests were conducted on the gaseous discharges from several
sludge incinerators. Stack tests were conducted by EPA at five locations, including three multiple-
hearth incinerators and two fluid-bed reactors, as follows: 6
A. Fluidized-bed reactor, 1,100 lb/h dry solids design capacity, operated at 100 percent
capacity during test, equipped with a 20-inch-water-pressure-drop venturi scrubber
operated at 18 inches water pressure drop. Tested by EPA and by a State agency, the lat-
ter using code method 8 (see tables 1 and 2).
B. Multiple-hearth (six hearths) incinerator, 750 lb/h dry solids design capacity, operated at
64 percent capacity during test, equipped with a 6-inch-water-pressure-drop single-
crossflow perforated-plate impinjet scrubber (see table 3).
C. Multiple-hearth (six hearths) incinerator, 900 lb/h dry solids design capacity, operated at
35 percent capacity during test, equipped with a 6-inch-water-pressure-drop single-
crossflow perforated-plate impinjet scrubber (see table 4).
3
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Table 3.Sludge incinerator facility B: Summary of results
Item
Run number
Average
1
2
3
Date 10-13-71 10-14-71 10-14-71
Testtime, minutes 120 120 120 120
Furnace feed rate, tons/h dry solids 0.237 0.236 0.249 0.24 1
Stack effluent:
Flow rate, dscfm 3,300 2,950 2,120 2,790
Flow rate, dscf/ton feed 835,000 750,000 511,000 699,000
Temperature,°F 198 196 199 198
Water vapor, volume % 3.64 4.02 3.65 3.77
CO 2 vo lume% dry 3.8 4.7 2.7 3.7
0 2 ,volume%dry 17.3 1.40 15.8 15.7
CO, volume % dry 0 0 0 0
SO 2 emissions, ppm 2.29 to 2.57 2.75 2.53
NO emissions, ppm 44.2 to 24.3 27.6
14.3
HCI emissions, ppm 0.624 to 1.33 0.858
0.621
Visib leemissions,%opacity <10 <10 <10 <10
Particulate emissions:
Probe and filter catch:
gr/dscf 0.0245 0.0196 0.0173 0.0205
gr/acf 0.0187 0.0155 0.0132 0.0158
lb/h 0.690 0.495 0.315 0.500
lb/ton of feed 2.91 2.10 1.26 2.09
Total catch:
gr/dscf 0.0374 0.0374 0.0457 0.0402
gr/acf 0.0289 0.0287 0.0348 0.0308
lb/h 1.06 0.945 0.832 0.946
lb/ton of feed 4.47 4.00 3.34 394
Note.dscfm indicates dry standard cubic feet per minute; dscf indicates dry standard cubic feet; acf indicates actual cubic
feet.
Source: Background Information for Proposed New Source Performance Standards, EPA Report APTD-1 3526, June 1973,
vol. 2, appendix.
D. Fluidized-bed reactor, 500 lb/h dry solids design capacity, operated at 95 percent capac-
ity during test, equipped with a 4-inch-water-pressure-drop single -crossflow perforated-
plate impinjet scrubber (see table 5).
E. Multiple-hearth incinerator, 2,500 lb/h dry solids design capacity, operated at about 50
percent capacity during tests, equipped with a 2 .5-inch-water-pressure -drop cyclonic iner-
tial jet scrubber (see table 6).
4
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Table 4.Sludge incinerator facility C: Summary of results
Item
Run number
Average
1
2
3
Date 7-15-71 7-15-71 7-16-71
Test time, minutes 80 80 80 80
Furnace feed rate, tons/h dry solids 0.111 0.149 0.146 0.135
Stack effluent:
F low rate, dscfm 1,230 1 ,490 1,400 1,373
Flow rate, dscf/ton feed 665,000 600,000 575,000 613,000
Temperature, °F 80 80 77 79
Water vapor, volume % 3.23 3.00 2.95 3.06
CO 2 . volume % dry 10.0 10.1 10.2 10.1
02, volume % dry 7.7 7.3 7.4 7.5
C0,volume%dry 0 0 0 0
SO 2 emissions, ppm 15.9 to 11.9 14.5 to 14.6 14.6 to 13.3 14.2
NOx emissions, ppm 402 to 140 90.8 to 74.3 14.5 to 142 163
50.6 to 61 .8
HCI emissions, ppm 3.50 to 2.62 2.33 to 2.62 2.52 to 2.62 2.72
Visibleemissions,%opacity <10 <10 <10 <10
Particulate emissions:
Probe and filter catch:
gr/dscf 0.01 27 0.0620 0.0196 0.0314
gr/acf 0.00985 0.0477 0.01 52 0.0242
lb/h 0.127 0.620 0.196 0.314
lb/ton of feed 1.14 4.16 1.34 2.21
Total catch:
gr/dscf 0.0195 0.0696 0.0260 0.0384
gr/acf 0.0150 0.0535 0.0201 0.0295
lb/h 0.206 0.889 0.3 12 0.469
lb/ton of feed 1.86 5.97 2.14 3.23
Note.dscfm indicates dry standard cubic feet per minute; dscf indicates dry standard cubic feet; acf indicates actual cubic
feet.
Source: Background In formation for Proposed New Source Performance Standards, EPA Report APTD-1 3526, June 1973
vol. 2, appendix.
The results of these tests are shown in tables 1 to 6. Figure 1 summarizes the results of the
particulate measurements. The results from the unit using a venturi scrubber operating at 18-inch
water pressure drop were used as the basis for the standard. The other systems using other types of
scrubbers operating at lower pressure drops failed to meet the promulgated NSPS of 1.3 lb/ton dry
sludge input. The study of these facilities indicated no relationship between the mass emission rates
and the percent of rated capacity at which the incinerator was operating, but a strong relationship
between pressure drop across the scrubber and mass emission rates was found. 4 All of the systems
easily met the opacity standard. Observations at 15 other facilities indicated they all met a 10-percent
5
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Table 5.Sludge incinerator facility D: Summaiy of results
Item
Run number
Average
1
2
3
Date 7-21-71 7-21-71 7-22-71
Test time, minutes 120 96 96 104
Furnace feed rate, tons/h dry solids 0.255 0.237 0.202 0.23 1
Stack effluent:
Flowrate,dscfm 1,190 1,170 1,240 1,200
Flow rate, dscf/ton feed 280,000 296,000 368,000 315,000
Temperature, °F 99 99 95 98
Water vapor, volume % 3.92 4.90 3.48 3.83
C0 2 ,volume%dry 8.8 9.9 9.1 9.3
0 2 ,volume%dry 6.3 7.4 8.2 7.3
CO,volume%dry 0 0 0 0
SO 2 emissions, ppm 8.29 to 11.2 14.8 to 14.8 14.2 to 15.4 13.8
17.8
NO emissions, ppm 154 to 168 41.2to42.9 187 to 170 132
161
HCI emissions, ppm 0.780 to 260 4.16 to 1.56 2.35 to 2.09 2.26
Visible emission, %opacity <10 <10 <10 <10
Particulate emissions:
Probe and filter catch:
gr/dscf 0.0551 0.0766 0.0545 0.0621
gr/acf 0.0468 0.0650 0.0467 0.0528
lb/h 0.562 0.768 0.579 0.636
lb/ton of feed 2.20 3.24 2.87 2.77
Total catch:
gr/dscf 0.0665 0.0859 0.0653 0.0726
gr/acf 0.0565 0.0729 0.0559 0.0618
lb/h 0.678 0.861 0.694 0.744
lb/ton of feed 2.66 3.63 3.43 3.24
Note.dscfm indicates dry standard cubic feet per minute; dscf indicates dry standard cubic feet; acf indicates actual cubic
feet.
Source: Background In formation for Proposed New Source Performance Standards, EPA Report APTD-1 3526. June 1973,
vol. 2, appendix.
opacity. The estimated costs of the scrubbing systems used as standard practice in the United States
are typically about 4 percent of the total incineration facility for a plant serving 100,000 people.
The scrubber required to achieve the proposed particulate standards would increase the cost an esti-
mated 0.4 percent. Annual operating costs were estimated to be increased by 0.9 percent. 5
6
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Table 6.Sludge incinerator facility E: Summary of results
Item
Run number
Average
1
2
3
Date 8-5-71 8-5-71 8-5-71
Test time, minutes 96 96 96 96
Furnace feed rate, tons/h dry solids 0.689 0.855 0.290 0.611
Stack effluent:
Flow rate, dscfm 9,840 8,510 10,290 9,547
Flow rate, dscf/ton feed
Temperature,°F 135 145 145 142
Watervapor,volume% 16.3 18.6 14.8 16.6
CO 2 . volume % dry 4.2 4.3 2.2 3.6
0 2 ,volume%dry 14.9 14.9 16.9 15.6
CO. volume % dry 0 0 0 0
SO 2 emissions, ppm 2.01 2.07 2.12 2.07
N0 emissions, ppm 62.8 to 46.0 33.5 to 75.8 44.3 to 54.7 61.2
HCI emissions, ppm 11.9 6.83 10.9 9.88
Visible emissions, % opacity <10 <10 <10 <10
Particulate emissions:
Probe and filter catch:
gr/dsf 0.0260 0.0136 0.0134 0.0177
gr/acf 0.0196 0.0099 0.0101 0.0132
lb/h 2.19 0.99 1.18 1.45
lb/ton of feed 3.18 1.16 4.07 2.80
Total catch:
gr/dscf 0.0335 0.0221 0.0170 0.0242
gr/acf 0.0252 0.0159 0.0128 0.180
lb/h 2.83 1.61 1.50 1.98
lb/ton of feed 4.11 1.88 5.17 3.72
Note.dscfm indicates dry standard cubic feet per minute; dscf indicates dry standard cubic feet; acf indicates actual cubic
feet.
Source: Background Information for Proposed New Source Performance Standards, EPA Report APTD-1 3526, June 1973,
vol. 2, appendix.
7
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Figure 1. Particulate emissions from sludge incinerators at wastewater treatment plants.
(See reference 4.)
Wastewater sludges contain metals that could be hazardous if discharged into the atmosphere.
Unfortunately, there are very few data on the metals being discharged to the atmosphere from
municipal sludge incineration. The forms in which metals are found in sludge will influence their
behavior on incineration. 5 For example, if cadmium is present in the sludge in solution as cadmium
chloride, it could volatilize upon incineration. If it is present as a precipitated hydroxide, it would
probably decompose to the oxide, but would not volatilize at the temperatures of incineration. It is
believed, however, that most of the hazardous or potentially hazardous metals, with the exception of
mercury, will not disproportionately appear in stack gases because of volatilization, but will be con-
verted to oxides and appear in the particulates removed by scrubbers or electrostatic precipitators
and in the ash.
METALS
PLANT, CONTROL EQUIPMENT
8
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Some data are available on the discharge of manganese and nickel, which indicate the following
emission rates from incinerator facilities with emission controls:
Metal
Emission factor range,
millipounds per ton (dry solids)
Mn
Ni
O.5tol.6
.2to8.2
In both cases, the higher limit is represented by a single measurement.
Mercury is an example of a substance that presents special problems during incineration. High
temperatures during incineration decompose mercury compounds to volatile mercuric oxide or
metallic mercury.
Tests for mercury have been conducted by EPA 7 on 42 sewage treatment plant sludges. The
mercury content ranged from 0.6 ppm to 43 ppm (in terms of dry solids) with an average value of
4.2 ppm. Tests on five incinerators equipped with scrubbers showed an average emission factor of
1.65 grams of mercury emitted to the atmosphere per metric ton of dry sludge incinerated.
Mercury-removal efficiencies of water scrubbers varied from 68 to 96 percent. A study of the fate
of mercury in municipal incineration plants has reported 8 that 9.7 percent of the mercury entering
a multiple-hearth furnace at Palo Alto, Calif., escaped the wet scrubber and entered the atmosphere,
59 percent appeared in the furnace ash, and the remainder appeared in the scrubber underflow. In
the same incinerator, only 0.84 percent of the lead in the sludge feed entered the atmosphere, with
88 percent in the ash and the rest in the scrubber underflow. The wet scrubber removed 93 percent
of the lead and 76 percent of the mercury from the exhaust gases.
In accordance with Section 112 of the Clean Air Act Amendments of 1970, a national emission
standard for mercury as a hazardous atmospheric pollutant resulting from sludge incineration was
proposed on October 25, 1974. This proposed hazardous pollutant standard limits the atmospheric
discharge of mercury from the incineration and drying of wastewater-treatment-plant sludges to a
maximum of 3,200 g/d. 9 This limit is based on maintaining an average ambient mercury concentra-
tion of 1 /1g/m 3 over a 30-day period. At an average emission rate (using wet scrubbers) of 1.65
grams of mercury per metric ton of dry solids incinerated, incineration facilities of 1,939 metric
tons per day of dry solids (2,138 tons per day of dry solids) will approach this limit. There are,
however, no known existing wastewater plants or new plants anticipated for use in the foreseeable
future that will approach this size.
GASEOUS POLLUTANTS
Gaseous pollutants that could be released by sludge incineration are hydrogen chloride, sulfur
dioxide, oxides of nitrogen, and carbon monoxide. Data are presented in tables 1-6 on the quanti-
ties of these materials found in stack gases. Carbon monoxide is no threat if the incinerator is prop-
erly designed and operated. Hydrogen chloride, which would be generated by decomposition of
certain plastics, is not a significant problem at concentrations currently observed. Consideration of
9
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the possibility of SO 2 and NO pollution is aided by examination of the sulfur and nitrogen content
of sludges. Sulfur content is relatively low in most sludges. In addition, much of this sulfur is in
the form of sulfate, which originated in the wastewater. Sulfur dioxide is not expected to be a seri-
ous problem. At San Mateo, Calif., the SO 2 discharge concentrations were found to be 10.2 ppm as
compared to a 300-ppm standard. 1 0
Sludge typically has a high nitrogen content from proteinaceous compounds and ammonium
ion. Limited data are available for predictmg whether a high proportion of these materials will be
converted to oxides of nitrogen on combustion. From the data available, the concentration of
oxides of nitrogen from sludge incineration should be less than 100 ppm from a properly operated
incinerator, and were observed to be less than 10 ppm from facility A (table 1). Considering this
low concentration, the production of oxides of nitrogen will probably not limit the use of incinera-
tion for disposing of sludge in most cases.
ORGANICS
In addition to the major air pollutants resulting from the burning of sludge, toxic substances
can arise because of the content of pesticides or other organic compounds in the sludge. Unfor-
tunately, very limited data are available on the concentrations of these materials in municipal
sludges or their fate in an incinerator. Data reported by EPA, 5 in a random selection of sludges,
showed the following levels of materials present in the raw sludges:
Compound
Range (ppm)
Aidrin
16 (in one sludge only)
Dieldrin
0.08 to 2.0
Chlordane
3.0 to 32
ODD
Notdetectedto0.5
DOT
Not detected to 1.1
PC Bs
Not detected to 105
Pesticide and polychlorinated-biphenyl (PCB) determinations were made on sludges collected
during the incinerator tests at three of the five plants listed in tables i-6. PCBs were found in all
of these sludges, but concentrations were low (1.2 to 2.5 ppm). Pesticides and PCBs were found
only in the sludge. They were not found in the ash from either type incinerator, nor in the inlet or
outlet scrubber water. Ash can be analyzed for these materials to the same degree of sensitivity as
the sludge. A level of 0.1 jig/g (ppm) could easily have been detected. It is quite certain that these
materials are not being carried out in the ash.
The mass flow rate of water to the scrubber is about 400 times the dry solids flow rate to the
incinerator. Consequently, the concentration at which these materials can be detected in water must
be sufficiently low to be sure that they are not escaping in the scrubber water. Fortunately, analyti-
cal techniques are such that these materials can be detected in water down to 0.1 ng/g (ppb). Thus,
it is reasonable to believe that they are not in the scrubber water.
Since the PCBs do not appear in ash or scrubber water, they are either destroyed by incinera-
tion or remain as vapors in the water-scrubbed (and cooled) gas stream. All of these materials have
some solubility in water, and it is likely that no trace would be present in the scrubber water. Conse-
10
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quently, their escape as vapors from the incinerators seems unlikely. However, one should also exam-
ine the available data on the decomposition of PCBs and pesticides in other situations.
Rapid thermal degradation of most pesticides has been shown to begin at approximately 500°
C with near total destruction at 9000 C (1,652° F). 1 ,1 2 If these materials volatilize before burning,
the use of afterburners on incinerators would be needed to provide complete destruction. One man-
ufacturer of pesticides achieves near total destruction of pesticides in its multiple-hearth carbon re-
generator by providing an afterburner using a 0.23-0.80-second retention time at 1,600° to 1,800° F.
The PCBs are even more thermally stable than most pesticides, as one would suspect. An in-
cinerator at St. Louis, Mo., achieves total destruction of concentrated PCBs at 2,400° F with a re-
tention time of 2.5 seconds. Experiments have shown, however, that 99 percent destruction is possi-
ble at 1,600° to 1,800° F in 2.0 seconds on pure PCBs.
Tests on municipal sludges 1 0 that total destruction of PCB was possible when oxidized
in combination with sewage sludge and with an exhaust gas temperature of 1100° F versus 1600° F
required when PCBs are handled separately. Ninety-five percent destruction of PCBs was achieved
in a multiple-hearth furnace with no afterburning at the normal exhaust temperature of 700° F.
CONCLUSIONS
The EPA Sewage Sludge Incineration Task Force 5 concluded that it has been adequately dem-
onstrated that existing well-designed and -operated municipal wastewater sludge incinerators are
capable of meeting the most stringent particulate emission control regulation existing in any State
or local control agency. This observation, coupled with the fact that the newly promulgated Federal
NSPS are based on demonstrated performance of an operating facility, indicates that use of proper
emission controls and proper operation of the incineration system will enable a facility to meet all
existing particulate matter regulations. Although only the venturi scrubber (tables 1-6) met the pro-
mulgated standard in the EPA tests, EPA 4 has stated that
Impingement scrubbers tested by EPA did not meet the standard but, in our best judgment, would do so if
used in conjunction with an oxygen meter that automatically regulates fuel burning rate. In our best judgment,
electrostatic precipitators could also provide more than adequate control. There are no EPA test data on
either of these control systems because during the test program there were no existing plants using them.
CASE HISTORIES
LIVERMORE, CALIF.
A recent evaluation 10 of the environmental impact of sludge incineration at Livermore, Calif.,
provides an interesting case history. Livermore proposed to install multiple-hearth furnaces for
11
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sludge incineration and lime recalcining. Much of the offgas from the recalcining furnace will be re-
cycled to the plant for recarbonation of the lime-treated wastewater. The Bay Area Air Pollution
Control District (BAAPCD) adopted standards for discharge as shown in table 7. Also shown in
table 7 are the results of analyses made at a nearby (San Mateo) multiple-hearth sludge incinerator.
These test data and those presented in tables 2-6 indicate that little difficulty should be encountered
in meeting particulate, hydrocarbon, and carbonyl standards with a properly designed and operated
system. Of major interest in Livermore was the potential impact of NO , although there were no
standards established. The relative contributions of NO in the Livermore valley from several sources
were evaluated with the following results:
Source
Pounds N0 per day
Automobiles
Sludge hauling ... .
Sludge oxidation...
Lime recalcining . . .
28,000
10
50
12
The sludge-hauling value is only for the hauling of sludges to the border of the valley where it and
the pesticides and PCBs it contains still must be dealt with in an environmentally acceptable fashion.
In this example, the NO contribution from multiple-hearth incineration was slightly higher than the
NO contribution from hauling only, but still was an insignificant fraction (0.2 percent) of the
total NO discharge in the study area. The average per capita discharges of pollutants from automo-
biles and sludge incinerators were also calculated, and the results are shown in figures 2-4.
Table 7.Emission limits at Livermore, Calif.
Test
Test results
Emission limits 1
Hydrocarbons, C 2 -C 6 , ppm (dry basis) at 6 percent 02
Total carbonyls, ppm (dry basis) at 6 percent 02
Grain loading, gr/dscf 2 atl2percent CO 2
0.4 - 2.2
3.4 - 7.6
0.017-0.021
25
25
0.15
According to the California BAAPCD regulation 2 for Units under 100 tons per day capacity with emissions adjusted to 6
percent 02.
2 dtcf indicates dry standard cubic feet.
Source: F. P. Sebastian et al., Sludge IncinerationAir Emission Standards vs. TechnologyA Case Study, presented at
Water and Wastewater Equipment Manufacturers Association Industrial Water and Pollution Conference and Exposition, Detroit,
Mich., Apr. 1974.
PALO ALTO, CALIF.
Figure 5 illustrates the results obtained at Palo Alto, Calif., with a multiple-hearth furnace
equipped with multiple-tray impingement scrubbers. Nitrous oxide emission at Palo Alto was only
0.037 g/day 1 0 as compared to 0.29 shown in figure 4 as a typical value. If this level of NO were
achieved in the Livermore example discussed earlier, the NO discharge from incineration and
recalcination would be even less than that from hauling alone.
REFERENCES
National Source Performance Standards, Municipal Incineration, Fed. Reg., 36, No. 247,
24876, Dec. 23, 1971.
12
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1972 automobile
40.8
1975 automobile
Oxidation
0.019
0
4.8
10
I
20
GRAMS PER DAY
30 40
Figure 2. Relative per capita contributions of hydrocarbons from automobiles and sludge incineration.
(See reference 10.)
1972 automobile I
1975 automobile
Oxidation
0.057
-I-
50
I
0 10 20 30 40 450 460
GRAMS PER DAY
Figure 3. Relative per capita contributions of carbon monoxide from automobiles and sludge incineration.
(See reference 10.)
1972 automobile
1975 automobile
Oxidation
36.0
I I I I I
0 10 20 30 40 50
GRAMS PER DAY
Figure 4. Relative per capita contributions of nitrogen oxides from automobiles and sludge incineration.
(See reference 10.)
40.8
470
4.8
0.29
13
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310
300 300.0
290
/
I,
UJ
30 D
C ,,
25.0 25.0 0.15
20 0.10
10 0.05
0 0.75 - 0
Hydro- Carbonyls, Sulfur
carbons, ppm oxides
ppm (SO 2 ), gr/dscf
ppm
Standards Actual
Figure 5. Standards and emissions from the Palo Alto multiple-hearth incinerator.
(See reference 10.)
2 Balakrishman, D. E. Williamson, and R. W. Okey, State of the Art Review on Sludge Incin-
eration Practice. Federal Water Quality Administration Report 17070 olV 04/70, 1970.
3 R. S. Bard, A Study of Sludge Handling and Disposal. Federal Water Pollution Control Ad-
ministration Publication WP-20-4, May 1968.
4 Background Information for New Source Performance Standards, EPA Report 450/2-74-003,
APTD-1352C, Feb. 1974, vol. 3.
report, Sewage Sludge Incineration Task Force, EPA, Feb. 1970.
6 Background In formation for Proposed New Source Performance Standards, EPA Report
APTD-1 3526, June 1973, vol. 2, appendix.
7 Background Information on National Emission Standards for Hazardous Air Pollutants
Proposed Amendments to Standards for Asbestos and Mercury, EPA 450/2-74-009a, Oct. 1974.
8 A Study of Pesticide disposal in a Sewage Sludge Incinerator, Versar, Inc., Monthly prog-
ress report, EPA Contract No. 68-01-1587, Sept. 9, 1974.
10.2
6.1
Particulate
emissions,
14
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and MercuryProposed Amendments to National Emission Standards, Fed. Reg.,
39, No. 208, pt. 2, 38064, Oct. 25, 1974.
°F. P. Sebastian et al., Sludge IncinerationAir Emission Standards vs. TechnologyA Case
Study, presented at Water and Wastewater Equipment Manufacturers Association Industrial Water
and Pollution Conference and Exposition, Detroit, Mich., Apr. 1974.
11 B j j Research on Equipment and Methods for Decontamination and Disposal of Pesticides
and Pesticide Containers, annual report, USDA Grant No. 12-14-100-9182(34), Mississippi State
University, June 1968 to June 1969.
1 2 Organic Pesticides and Pesticide ContainersA Study of Their Decontamination and Com-
bustion, Foster D. Snell, Inc., final report, Bureau of Solid Waste Management Contract No. CPA-
69-140, 1970.
15
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METRIC CONVERSION TABLES
Recommended Units
Description
Length
Area
Volume
Mass
Time
Force
Moment or
torque
Stress
Unit
metre
kilometre
millimetre
micrometre
square metre
square kilometre
square millimetre
hectare
cubic metre
litre
kilogram
gram
milligram
tonne or
megagram
second
day
year
newton
newton metre
pascal
kilopascal
Symbol
m
km
mm
jjm.
m2
km2
mm2
ha
m3
1
kg
g
mg
t
Mg
s
d
year
N
N-m
Pa
kPa
Application
Description
Precipitation,
run-off,
evaporation
River flow
Flow in pipes.
conduits, chan-
nels, over weirs,
pumping
Discharges or
abstractions,
yields
Usage of water
Density
Unit
millimetre
cubic metre
per second
cubic metre per
second
litre per second
cubic metre
per day
cubic metre
per year
litre per person
per day
kilogram per
cubic metre
Symbol
mm
m3/s
m3/s
l/s
m3/d
m3/year
I/person
day
kg/m3
Comments
Basic Sf unit
The hectare (10 000
m2) is a recognized
multiple unit and
will remain in inter-
national use.
The litre is now
recognized as the
special name for
the cubic decimetre.
Basic Sf unit
1 tonne = 1 000 kg
1 Mg = 1 000 kg
Basic SI unit
Neither the day nor
the year is an SI unit
but both are impor-
tant.
The newton is that
force that produces
an acceleration of
1 m/s2 in a mass
of 1 kg.
The metre is
measured perpendicu-
lar to the line of
action of the force
N. Not a joule.
of Units
Comments
For meteorological
purposes it may be
convenient to meas-
ure precipitation in
terms of mass/unit
area (kg/m3).
1 mm of rain =
1 kg/m2
Commonly called
the cumec
1 l/s = 86.4 m3/d
The density of
water under stand-
ard conditions is
1 000 kg/m3 or
1 000 g/i or
1 g/ml.
Customary
Equivalents
39.37 in.=3.28 ft=
1.09yd
0.62 mi
0.03937 in.
3.937 X103=103A
1 0.764 sq ft
= 1.196sqyd
6.384 sq mi =
247 acres
0.00155 sq in.
2.471 acres
35.314 cu ft =
1.3079cuyd
1. 057 qt = 0.264 gal
= 0.81 XlO^acre-
ft
2.205 Ib
0.035 oz = 1 5.43 gr
0.01543 gr
0.984 ton (long) =
1.1 023 ton (short)
0.22481 Ib (weight)
= 7.233 poundals
0.7375 ft-lbf
0.02089 Ibf/sq ft
0.14465 Ibf/sq in
Description
Velocity
linear
angular
Flow (volumetric)
Viscosity
Pressure
Temperature
Work, energy.
quantity of heat
Power
Recommended Units
Unit
metre per
second
millimetre
per second
kilometres
per second
radians per
second
cubic metre
per second
litre per second
pascal second
newton per
square metre
or pascal
kilometre per
square metre
or kilopascal
bar
Kelvin
deqree Celsius
joule
kilojoule
watt
kilowatt
joule per second
Symbol
m/s
mm/s
km/s
rad/s
m3/s
l/s
Pa-s
N/m2
Pa
kN/m2
kPa
bar
K
C
J
kJ
W
kW
J/s
Comments
Commonly called
the cumec
Basic Sf unit
The Kelvin and
Celsius degrees
are identical.
The use of the
Celsius scale is
recommended as
it is the former
centigrade scale.
1 joule = 1 N-m
where metres are
measured along
the line of
action of
force N.
1 watt = 1 J/s
Customary
Equivalents
3.28 fps
0.00328 fps
2.230 mph
1 5,850 gpm
= 2.120cfm
15.85 gpm
0.00672
poundals/sq ft
0.000145 Ib/sq in
0.145 Ib/sq in.
14.5 b/sq in.
5F
T ~17-77
2.778 X 10 7
kw hr =
3.725 X 10-'
hp-hr = 0.73756
ft-lb = 9.48 X
10-»Btu
2.778 kw-hr
Application of Units
Customary
Equivalents
35.314 cfs
15.85gpm
1.83 X 10 3 gpm
0.264 gcpd
0.0624 Ib/cu ft
Description
Concentration
BOD loading
Hydraulic load
per unit area;
e.g. filtration
rates
Hydraulic load
per unit volume;
e.g., biological
filters, lagoons
Air supply
Pipes
diameter
length
Optical units
Unit
milligram per
litre
kilogram per
cubic metre
per day
cubic metre
per square metre
per day
cubic metre
per cubic metre
per day
cubic metre or
litre of free air
per second
millimetre
metre
lumen per
square metre
Symbol
mg/t
kg/m3d
m3/m2d
m3/m3d
m3/s
l/s
mm
m
lumen/m2
Comments
If this is con-
verted to a
velocity, it
should be ex-
pressed in mm/s
(1 mm/s = 86.4
m3/m2 day).
Customary
Equivalents
1 ppm
0.0624 Ib/cu-ft
day
3.28 cu ft/sq ft
0.03937 in.
39.37 in. =
3.28ft
0.092 ft
candle/sq ft
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