Thermal Destruction of Bacillus Anthracis Surrogates
in a Pilot-Scale Incinerator

Paper #328

Joseph P. Wood3, Paul Lemieux3, Doris Betancourt3, Nicole Griffinb, Jeffrey Ryan3
Peter Kariherb, David Natschkeb

a US Environmental Protection Agency, Office of Research and Development, Research
Triangle Park, NC 27711

b Arcadis G & M. Research Triangle Park, NC 27709
ABSTRACT

The decontamination of a building following a biological warfare agent (such as Bacillus
anthracis) release may result in a significant quantity of building decontamination
residue (BDR). This BDR would consist of various materials such as ceiling tile, carpet,
wallboard, concrete, and wood, which would be removed from the building either before
or after decontamination efforts. Although the BDR is likely to have been
decontaminated, the possibility exists for the presence of trace amounts of biological
agent. Although a likely disposal technique for the BDR is high temperature
incineration, complete destruction of microbiological organisms in an incinerator
environment is not a certainty, due to heat transfer limitations and matrix effects. This
paper describes experiments that were performed in a pilot-scale rotary kiln incinerator to
evaluate the thermal destruction of B. anthracis surrogates (bacterial spores) present
within bundles of carpeting and ceiling tile. Another purpose of the experiments was to
evaluate sampling and analytical techniques to measure spores in the exhaust gas and
material bundles. No spores were detected via any of the three sampling trains in the
exhaust gas for the carpet burn tests conducted in July and August 2005, although the
detection limit was determined to be 22 spores/dry standard ft3. Combustion of the
nylon-6 carpet resulted in increased nitrogen oxide (NOx) emissions, with short-term
spikes in emissions levels from approximately 30 ppm baseline to roughly 150 ppm with
each carpet bundle charged. The use of biological indicator strips to quantify thermal
destruction of spores embedded within carpet and ceiling tile bundles was successful.
Spores embedded within wet ceiling tile bundles took at least 35 minutes to completely
destroy, possibly exceeding typical incinerator solid waste residence times. The charging
of ceiling tile bundles had minimal impact on the air pollutant emissions studied.

INTRODUCTION

After a building has gone through decontamination activities following a terrorist attack
with a biological warfare (BW) agent such as Bacillus anthracis (B.A.), there will be a
significant amount of residual material and waste to be disposed. This material is termed
"building decontamination residue" (BDR). Although it is likely that the BDR will have
already been decontaminated, the possibility exists for remaining B.A. spores to be

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present in absorbent and/or porous material such as carpet, fabric, ceiling tiles, office
partitions, furniture, and personal protective equipment (PPE) and other materials used
during cleanup activities. It is likely that much of this material will be disposed of in
high-temperature thermal incineration facilities, such as medical/pathological waste
incinerators, municipal waste combustors, and hazardous waste combustors.1

Although pathogens such as B.A. present in BDR are killed at typical incineration
temperatures (> 800 °C [1472 °F]), gas-phase residence times (> 2 s), and solid-phase
residence times (> 30 min), it is possible for some of the pathogens to escape the
incinerator due to bypassing the flame zones, cold spots, and incomplete penetration of
heat through the bed.1 In the early 1990's, the US EPA performed testing of commercial
hospital waste incinerators2 by inputting large quantities of Geobacillus
stearothermophilus (an anthrax surrogate) spores into the combustors and measuring the
number leaving in the stack emissions and in the incinerator bottom ash, in terms of Log
reduction in spore concentration. It was determined that, in certain cases, only a 3-Logio
reduction in spore destruction was found, in spite of acceptably high operating
temperatures and sufficiently long residence times.

As a result of the 2001 anthrax attacks, the EPA instituted an experimental and
theoretical research program to investigate issues related to the thermal destruction of
contaminated BDR3 initially including carpeting, ceiling tile, and wallboard. Tests are
being performed at bench- and pilot-scale. This paper describes experiments that were
performed in a pilot-scale rotary kiln incinerator to evaluate the thermal destruction of B.
A. surrogates (bacterial spores) present within bundles of carpeting and ceiling tile.
Another purpose of the experiments was to evaluate three novel sampling and analytical
techniques to measure bacterial spores in the exhaust gas. Thermal destruction of spores
in the ceiling tile was determined by quantification of spore strips. Emissions of NOx,
carbon monoxide (CO), total hydrocarbons (THC), and other pollutants were measured
on a continual basis throughout the testing.

The results described in this paper may be of use to incinerator owners and operators that
choose to combust BDR, by providing some technical background and guidance
regarding what might be required to ensure complete destruction of biological agents and
the potential impacts on air emissions.

EXPERIMENTAL
Facility Description

Tests were performed from July 2005, through December 2005, using EPA's Rotary Kiln
Incinerator Simulator (RKIS), which is located at EPA's campus in Research Triangle
Park, North Carolina. The RKIS consists of a primary and secondary combustion
chamber (SCC), each rated at 73 kW (250,000 BTU/hr). The RKIS can burn a variety of
fuels, including surrogate hazardous waste, although for the tests described herein, only
natural gas was burned in the primary chamber. The RKIS is equipped with continuous
emissions monitors (CEMs) for measuring oxygen (02), carbon dioxide (C02), water
vapor (H20), CO, NOx, sulfur dioxide (S02), and THC. However, for the tests described

2

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herein, only data for 02, C02, CO, NOx were logged for all of the tests, with THC levels
measured for some of the testing, for various technical reasons. Emissions were
monitored in the exhaust duct, where sufficient mixing and cooling had taken place.
Temperature readings are taken throughout the kiln system, although only kiln exit
temperatures are reported here. Figure 1 is a diagram of the RKIS (note surrogate wastes
were not used in the tests described herein); further details of the RKIS can be found
elsewhere.1 Some general operating characteristics of the kiln during the tests are
summarized in Table 1. An overview of the test program reported here is found in Table
2.

Figure 1. US EPA's Rotary Kiln Incinerator Simulator'

CEM Duct 3
(0) TC

44-

Duct 4
TC

4

Secondary Combustion Chamber

'////////////////////////A

SCC	see Mid

• CEMs	TC 0

SCC Mix
TC °

m//////////////////A

Surrogate
Waste
Injection



CEM (1),
Duct 5^
TC

-2nd Floor

Kiln Exit
• TC

Afterburner



CEM (2).

Ramrod



-Ground Floor-

Kiln Section Transition Section

Table 1. Summary of RKIS Baseline Operating Parameter Values

RKIS Operating Parameter

Range or approximate value for tests

Primary combustion chamber (PCC) air
flow

83 - 89 standard cubic meters per hour
(2920 - 3145 standard cubic feet per hour;
SCFH)

Natural gas flow PCC

-5.7 SCM per hour (200 SCFH)

Natural gas flow SCC

0 SCFH

Air flow SCC

~ 20 SCM per hour (700 SCFH)

Draft PCC

~ 0.05 inches water

Kiln rotation speed

0.5 rpm for the tests conducted in July and
August. Kiln was not rotating for the
October and December tests.

Kiln exhaust gas oxygen level

~ 15.5%

3

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Table 2. Summary of RKIS Tests

Date of

Building

Bacterial spore

Purpose of test

Comments

Test

Material

surrogate/form





7/20, 7/21,

Carpet in

Geobacillus

Determine

Kiln rotating

7/27, and

sterile water

Stearothermophilus

emissions of



8/17/05



soaked in the water

spores; Evaluate









spore emissions









sampling trains













10/6, 10/7,

Carpet soaked

2 BI strips in

Thermal

First strip used

&

in water

sealed pipe with

destruction

to determine if

10/13/05



thermocouple

quantification

living or dead;





(T/C)

using spore strip

second strip to







technique.

quantify. On









10/6, T/C not









working









correctly











12/8-

Ceiling tile

No spores; just

Temperature

Bundles wet

12/9/05



temperature

profiles

and dry





profiles















12/13,

Ceiling tile

2 BI strips in

Thermal

Both wet and

12/16,



sealed pipe with

destruction

dry bundles

12/20, and



T/C

quantification

tested

12/29/05





using spore strip









technique.



Building Material Experiments

Tests performed in July and August 2005, were with carpet bundles soaked in a solution
of sterile water containing Geobacillus stearothermophilus at a level of approximately
108 spores per gallon (2.6 x 107 per liter). The carpet bundles were made from Nylon-6
material, weighed approximately 1 pound dry, and weighed on average about 2.1 pounds
(0.95 kg) wet. The wetted bundles were approximately 3 inches wide by 3 inches high by
11 inches (7.6 cm by 7.6 cm by 28 cm) long, and sealed in plastic bags. For each day of
testing, a total of six carpet bundles were fed to the kiln, with one bundle fed every 10
minutes. The primary purpose of these tests was to determine spore emissions levels in
the exhaust gas while evaluating the bacterial spore emissions sampling trains themselves
as well. Sampling for bacterial spores in the exhaust gas began with the first bundle fed;
sample gas extraction occurred approximately in the area of CEM (2) as noted in Figure
1. The three spore emissions sampling trains are discussed in more detail below.

Tests performed in October 2005 were with the same carpet type and size described
above, and all samples were wetted (to simulate carpeting that may have become wetted

4

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during the decontamination process). However, for this series of tests, the carpet samples
were bundled together using a titanium cage, and a small sealed metal pipe was
embedded into the carpet bundle. Inside the metal tube were two biological indicator
(BI) spore strips and a Type K thermocouple (to measure charge probe temperature).
Additional details of this pipe - BI - thermocouple arrangement can be found elsewhere.1
For each of the three days of testing, a total of five carpet bundles were fed to the kiln.
The primary purpose of these carpet tests was to evaluate thermal destruction of spores as
a function of time the bundle remained in the kiln. The carpet bundle was thrown into the
kiln at the end opposite of the burner (the kiln was not rotating), and removed after the set
time period using a gaffe to hook and remove the titanium cage and remaining carpet
bundle. A secondary purpose for this series of tests was to evaluate the method used to
determine thermal destruction efficiency, i.e., through the use of spore strips inside a
sealed pipe. This approach to quantifying spore destruction using BI strips is described
in more detail below.

Tests in December 2005 were performed with ceiling tile bundles. The bundles consisted
of 14 pieces; each individual piece was 7.62 cm x 7.62 cm x 1.9 cm (3 inches by 3
inches, and 3/4 inch) thick. The ceiling tile pieces were bound together in a cage made
from titanium, and the total length of the bundle was about 11 inches (28 cm). The
purposes of these ceiling tiles tests were to evaluate thermal destruction of spores as a
function of time and gas temperature, and any potential air pollution emissions impacts.
(Initial tests with the ceiling tiles were conducted without bacterial spores, to characterize
temperature profiles.) Subsequent tests for spore thermal destruction analysis were
conducted using BI strips encased in a metal pipe, which was embedded into the ceiling
tile bundle - similar to what was done for the carpet bundle BI tests. Tests were
conducted with both wetted and dry bundles. The mass of the dry bundles was on
average approximately 500 grams; while the mass of bundles that were soaked in water
averaged about 1519 grams (includes mass of titanium cage).

Spore Emission Test Methods

During our carpet burn tests 3 sampling trains were co-located to pull from the exhaust at
a location defined by a straight run. Each train was defined by an ice-chilled impinger
train with gas flow controlled by an EPA Method 5 box. Each impinger train consisted
of two Greenberg-Smith impingers filled with a sterile, pH 7.4 phosphate buffer solution,
1 empty impinger, and a silica gel impinger to protect the gas meter. The 3 trains
differed in the approach to sample cooling prior to the impinger train. These were:
cooled sample probe, dilution sample probe, and virtual impactor probe.

The "cooled probe" technique uses a pH 7.4 phosphate buffer solution for the collection
of spores. The gas stream is cooled to less than 38 °C (100 °F) using a cooled probe prior
to impinger collection. The cooled probe consisted of an Allihn condenser with ice water
pumped through the jacket.

The "virtual impactor" technique uses a virtual impactor to concentrate the larger
biological particles and separate them from the fine particulate prior to impinger
collection, with a cutpoint of 0.5 microns.

The "dilution probe" technique uses a pH 7.4 phosphate buffer solution for the collection
of spores. The gas stream will be cooled to less than 38 °C (100 0 F) using a dilution

5

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manifold prior to impinger collection. The sample stream is mixed with HEPA filtered
air to provide this dilution.

After sampling, each impinger solution was analyzed separately. Upon receipt, samples
were centrifuged to concentrate all particulate, including spores, into a single solid "plug"
that was recovered, washed, and diluted to 1 mL with sterile buffer solution. Analysis
consisted of spreading 0.1 ml of this concentrated sample onto 3 replicate trypticase soy
agar plates (TSA) plates, incubating at 60 °C (140 °F) over night, and manual counting.
A quantifiable limit of 30 CFU (colony forming units) per plate is used. Data from our
bio laboratory have shown a typical RSD (relative standard deviation) of 30 % for
samples above this quantifiable limit. Plates over 300 CFU are rejected as "too numerous
to count" and repeated at a greater dilution factor. Based on the above described
analysis, this results in an impinger detection limit of 300 CFU, or 1,200 CFU per gas
sample (based on 4 impingers in the train).

Using a sample flow rate of 0.91 dry, standard (20 0 C, or 68 °F) ftVminute, a sample
time of 1 hour, this corresponds to a detection limit of about 22 spores/dry standard ft3, or
about 20 spores per standard cubic foot, wet basis. Note that this quantifiable limit
determination assumes that no spores are lost in the sampling probe.

Bacteriological Methods

As mentioned previously, Geobacillus stearothermophilus (ATCC 7953) spore strips -
2.0 x 106 spores/strip (Raven Biological Laboratories, Inc.) were used as biological
indicators. Two spore strips were used per test; both were placed in a metal pipe and
embedded inside the material sample.

After completion of the test, spore survivability was qualitatively analyzed by placing
one of the heat-treated spore strips in 25 ml of sterile nutrient broth (NB) and incubated at
55°C ± 2 (131 °F) for 7 days. A positive control consisting of a spore strip of G.
stearothermophilus (non-heated) in 25 ml of NB was incubated along with the heat-
treated spore strip. Development of turbidity during the 7-day incubation period was
scored as positive. Absence of growth (no turbidity) was scored negative.

To quantify the spore population (survivability) after the test, a 1/100 dilution of the 2nd
heat-treated spore strip (w/v) was homogenized in a Nasco masticator blender - 10
beats/sec. Dilutions were plated in triplicates on TSA plates and incubated at 55°C (131
°F) ± 2 for 24 hours. Concomitantly, a positive control consisting of a 1/100 dilution of a
G. stearothermophilus non-heated spore strip was homogenized, plated and incubated at
55°C (131 °F) ± 2 for 24 hours to determine the initial spore population prior to heating.
The spore population for both the heat-treated spore strip and the positive control was
determined by colony-forming units (CFU)5.

Spore survivability was determined by Logio Reduction (LR)6:

LR = logio ( c ) - logio (t )	(1)

where

c = CFU of positive control
t = CFU of heat-treated spore strip

RESULTS AND DISCUSSION

6

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Spore Emission Test Results

No spores were detected via any of the three sampling trains in the exhaust gas for the
carpet burn tests conducted in July and August 2005. The possibility exists that spores
were indeed present in the exhaust gas, i.e., not destroyed in the kiln or in the exhaust
gas, but were below the level of detection. With the average amount of water soaked into
the carpet bundle being around 1.1 pounds (0.5 kg), and the spore density in the water at
1 x 108 spores/gallon (2.6 x 107 per liter), this corresponds to approximately 1.32 x 107
spores per bundle, or 7.92 x 107 total spores charged to the incinerator during the test.
With gas flow determined at the point of sampling to be on average 100.1 standard
ftVminute, the maximum number of spores that could be present in the exhaust during the
1-hour test, but still escape detection, is 120,000 CFU. Therefore the minimum
destruction efficiency is calculated to be 2.8 LR (see equation 1).

For all of these tests, average kiln exit temperatures prior to the feeding of the carpet
ranged from about 804 - 827 °C (1480 - 1520 °F). With the feeding of each bundle
every 10 minutes, kiln exit temperature rose between 38 - 149 °C (100 - 300 °F), but then
backed down and stabilized at around 815 °C (1500 °F), until another bundle was fed.

Consistent with work done previously to characterize the impact combustion of carpet
has on air pollutant emissions7, NOx emissions spiked temporarily (referred to as a
transient puff) from a baseline level of about 30 ppm to a peak of about 150 ppm, then
back to the baseline level. This puff occurred over the course of about 10 minutes, the
time interval that each carpet bundle was charged to the kiln. In general, CO emissions
increased as well, with baseline levels of about 20 - 30 ppm increasing by about 5-10
ppm with the introduction of the carpet bundles. Correspondingly, exhaust gas oxygen
baseline levels were about 15.5 %, were reduced to between 11-12% with the feeding of
each bundle, but then rose back to baseline levels prior to the introduction of another
bundle.

Carpet - Spore Thermal Destruction Results

As mentioned above, these tests were conducted in October 2005 to quantify bacterial
spore thermal destruction efficiency using BI spore strips, as a function of time the
bundle was left in the kiln. The results of these tests are shown in Tables 3 through 5.
During these experiments, Raven Spore Strips were used. The manufacturer states the
organism, Geobacillus stearothermophilus, is present on the strip at a concentration of
2.0 x 106. Our analysis of spore strips which were not subjected to any thermal treatment
(i.e., a positive control) resulted in a level of 1.9 x 106, confirming the manufacturer's
stated level. As can be seen in the tables below, in general, thermal destruction
(surviving spores < 1.00 xlO6) didn't begin until approximately 7 minutes (see runs D
and E of 10/7 test, and run F of 10/13 test). Not coincidentally, the tests resulting in the
greatest destruction of spores also indicate the spore strips were subjected to the highest
temperatures (maximum charge probe temperature). In general, spore strips left in the
kiln longer were exposed to higher temperatures, although there are exceptions, which
may be due to various reasons, including variable kiln gas exit temperature and variable
placement within the kiln bed. Lastly, a negative control (TSA with no known spores

7

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was poured into plates or into the tubes used for the spore strips and examined for
growth) was used once per test, and all were found to have no growth.

Table 3. Carpet/Spore strip chamber: Surviving Number of Spores for Tests Conducted 10/6/05













Negative

Run designation

A

C

D

E

F

Control



1.35 x

1.25 x

1.53 x

2.08 x

1.24 x



Number of spores surviving

106

106

10®

10®

10®

0

Time in kiln (minutes)

2:04

4:53

4:53

6:10

6:10

0:00

Average Kiln Exit Temperature

Not

803

807

809

818



° C (°F)

available

(1477)

(1485)

(1489)

(1504)



Maximum Charge Probe



112

101

120

103



Temperature ° C (°F)

56 (133)

(233)

(214)

(248)

(218)



Table 4. Carpet/Spore strip chamber: Surviving Number of Spores for Tests Conducted 10/7/05













Negative

Run Designation

A

C

D

E

F

Control



1.77 x

1.38 x

9.7 x



1.50 x



Number of Spores Surviving

106

106

105

0 (NG)

10®

0

Time in kiln (minutes)

5:53

5:57

7:05

6:46

5:07

0:00

Average Kiln Exit Temperature

831

833

833

843

842



° C (°F)

(1527)

(1532)

(1532)

(1549)

(1547)



Maximum Charge Probe

218

138

264

552

142



Temperature ° C (°F)

(425)

(280)

(507)

(1026)

(287)



NG= No growth

Table 5. Carpet/Spore strip chamber: Surviving Number of Spores for Tests Conducted 10/13/05

Run Designation

A

C

D

E

F

Negative
Control





1.24 x

1.57 x

1.52 x

2.4 x



Number of Spores Surviving

1.42x10®

10®

10®

10®

105

0

Time in kiln (minutes)

4:02

4:02

5:00

6:00

6:51

0:00

Average Kiln Exit Temperature



772

788

786

792



° C (°F)

783 (1441)

(1421)

(1451)

(1447)

(1457)



Maximum Charge Probe

Not

84

137

292

261



Temperature ° C (°F)

functioning

(184)

(278)

(557)

(501)



Ceiling Tile - Temperature Profiles and Spore Thermal Destruction
Results

The thermal destruction test results for the spores in ceiling tile bundles are found in
Tables 6 through 9, and Figures 2-3. As with the carpet bundles, the initial number of
spores on the strips was 2.0 x 106. A positive control test was conducted on 12/19/05,
Run D, and the post-run spore count was 1.3 x 106. For the dry ceiling tile bundles, a 1
to 2 logio reduction in the number of spores occurs sometime between 5 to 10 minutes,
and complete destruction (6 logio reduction) occurring after 12 minutes. For the wet
ceiling tile bundles, although the results are somewhat variable, reduction in spores (from
a 1-2 logio reduction up to complete destruction) occurs between 35 -38 minutes.

8

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However, as shown in Figure 3, spore survival is dependent on internal bundle
temperature, regardless of whether the bundle is wet or dry.

Baseline (prior to the ceiling tile charge) NOx emissions were between approximately 20-
25 ppm, and temporarily increased by a few ppm with the introduction of each ceiling tile
bundle.

Table 6. Surviving Number of Spores forTests Conducted 12/13/05

Run Designation

A

B

C

D

Negative
Control

Number of Spores Surviving

5.3 x
105

6.9 x
105

7.0 x
105

5.3 x
104

0

Time in kiln (minutes)

5:07

5:05

9:58

9:55

0:00

Wet or dry bundle
Average Kiln Exit Temperature
° C (°F)

dry
779
(1435)

dry
779
(1435)

dry
779
(1435)

dry
777
(1431)



Maximum Charge Probe
Temperature ° C (°F)

206
(402)

108
(227)

212
(414)

499
(930)



Table 7. Surviving Number of Spores for Tests Conducted 12/16/05

Run Designation

A

B

C

D

E

F

G

Negative
Control

Number of Spores
Surviving

TFTC

TFTC

TFTC

TFTC

TFTC

7.3x10 5

TFTC

0

Time in kiln (minutes)

11:50

11:58

15:09

15:08

18:00

30:15

35:04

0:00

Wet or dry bundle

dry

dry

dry

dry

dry

wet

wet



Average Kiln Exit
Temperature ° C (°F)
Maximum Charge Probe
Temperature ° C (°F)

803
(1477)
335
(635)

804
(1480)
398
(748)

806
(1483)
562
(1044)

802
(1475)
643
(1189)

802
(1475)
464
(868)

798

(1469)

Not

working

801
(1473)
357
(675)



TFTC= too few to count

Table 8. Surviving Number of Spores forTests Conducted 12/20/05











Negative

Run Designation

A

B

C

E

Control



6.5 x

1.6 x

6.2 x





Number of Spores Surviving

105

106

105

TFTC

0

Time in kiln (minutes)

35:03

30:08

35:01

36:55

0:00

Wet or dry bundle

wet

wet

wet

wet



Average Kiln Exit Temperature

801

806

808

810



° C (°F)

(1473)

(1482)

(1486)

(1491)



Maximum Charge Probe

300

128

144

438



Temperature ° C (°F)

(572)

(263)

(292)

(821)



9

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Table 9. Surviving Number of Spores for Tests Conducted 12/29/05

Run







D

(positive







Negative

Designation

A

B

C

control)

E

F

H

Control

Number of

















Spores

1.2 x

5.5 x





7.8 x



1.8 x



Surviving

106

105

TFTC

1.3x10®

105

2.5 x104

106

0

Time in kiln

















(minutes)

8:01

8:01

9:03

0:00

9:00

31:55

37:55

0:00

Wet or dry

















bundle

dry

dry

dry



dry

wet

wet



Average Kiln



822









821



Exit



(1512)









(1509)



Temperature °

824



821

Not

818







C(°F)

(1516)



(1510)

applicable

(1505)

819 (1507)





Maximum

















Charge Probe



162









275



Temperature

165

(323)

265

Not

568

Not

(527)



° C (°F)

(329)



(509)

applicable

(1055)

functioning





Figure 2. Ceiling Tile Bundle Spore Survival as Function of Time in Kiln

10000000 1

Time in Kiln (min)

CONCLUSIONS/SUMMARY

A series of tests was performed at a pilot scale incinerator with the following objectives:
determine thermal destruction of B. Anthrcicis surrogate spores in carpet bundles by
measuring their levels in the exhaust gas; evaluate the bacterial spore emissions sampling

10

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trains used for this measurement; evaluate thermal destruction of spores in carpet and
ceiling tile bundles as a function of time and temperature, using BI strips; and lastly,
evaluate any potential air pollution impacts associated with the thermal treatment of the
building materials. The results described herein mostly have implications for incinerator
owners and operators that may have to deal with BDR, by providing some technical

Figure 3. Ceiling Tile Bundle Spore Survival as a Function of Internal Temperature

10000000

1ooooo

looooe

(0
>

>

3

to

V

i_

o
a.

to

10000

1000

100"

10

~ Wet Bundles
¦ Dry Bundles

200 400	i7

Max. Charge T (°F)

1400

background and guidance regarding what might be required to ensure complete
destruction of biological agents and the potential impacts on air emissions.

No spores were detected via any of the three sampling trains in the exhaust gas for the
carpet burn tests conducted in July and August 2005. The detection limit was determined
to be 22 spores/dry standard ft3, corresponding to a maximum potential number of spores
emitted equal to 120,000, and a minimum destruction efficiency of 2.8 LR. Additional
research is needed to lower the detection limit for the three sampling trains. Combustion
of the nylon-6 carpet resulted in increased NOx emissions, with short-term spikes in
emissions from approximately 30 ppm baseline to roughly 150 ppm with each carpet
bundle charged.

11

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The use of BI strips to quantify thermal destruction of spores embedded within carpet and
ceiling tile bundles was successful. BI strips are normally only used in a qualitative
manner, i.e., to indicate whether complete destruction of spores was obtained or not. But
this novel, quantitative approach was useful in determining the time window when
thermal destruction begins and when complete destruction is obtained, as a function of
the building material, and whether the material is wet or dry. Spores embedded within
wet ceiling tile bundles took at least 35 minutes to completely destroy, possibly
exceeding typical incinerator solid waste residence times. The charging of ceiling tile
bundles had minimal impact on the air pollutant emissions studied.

ACKNOWLEDGEMENTS

The authors would like to thank Richie Perry and Jarred Novak of ARCADIS; and Marc
Calvi of EPA/NRMRL for their invaluable help.

REFERENCES

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