600R72107
PB-222 160
MICROBIOLOGICAL STUDIES OF COMPOST
PLANT DUST
David H. Armstrong, et al
National Environmental Research Center
Cincinnati, Ohio
November 1972
EPA
R2-72-131
EPA-R2-72-131, 1972
DISTRIBUTED BY:
National Technical Information Service
U. S. DEPARTMENT OF COMMERCE
5285 Port Royal Road, Springfield Va. 22151
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PB 222 160
EPA-R2-72-131 Environmental Protection Technology Series
November 1972
Microbiological Studies of
Compost Plant Dust
O
National Environmental Research Center
Office of Research and Monitoring
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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.EPA-R2-72-131
November 1972
MICROBIOLOGICAL STUDIES OF
COMPOST PLAINT DUST
David H. Armstrong and Mirdza L. Peterson
Solid Waste Research Laboratory
National Environmental Research Center
Cincinnati, Ohio 45288
(Mr. Armstrong is now with the California Regional
Water Quality Board, Oakland, California 94612)
Program Element 1D2063
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH ANH MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO- 45268
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REVIEW NOTICE
The Solid Waste Research Laboratory of the National
Environmental Research Center, Cincinnati, U. S. Environmental
Protection Agency, has reviewed this report and approved pub-
lication. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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FOREUORD
Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise and other forms of
pollution, and the unwise management of solid waste. Efforts
to protect the environment require a focus that recognizes
the interplay between the components of our physical environ-
ment-air, water,and land. The multidisciplinary programs of
the National Environmental Research Centers provide this
focus as they engage in studies of the effects of environmental
contaminants on man and the biosphere and in a search for ways
to prevent contamination and recycle valuable resources.
The study described here was made to determine the nature
*
and extent of respirable microorganisms emitted into the at-
mosphere during the storage, processing, and composting of
municipal solid waste and sewage sludge. The results of the
study will serve as basis for developing guidelines for en-
vironmental air concentrations related to solid waste
handling operations.
Andrew W. Breidenbach, Ph.D.
Director, National Environmental
Research Center, Cincinnati
ili
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TABLE OF CONTENTS
ABSTRACT - 1
INTRODUCTION 2
MATERIALS AND METHODS
Air sampling equipment and techniques 3
Media 3
Sampling locations 5
RESULTS 7
DISCUSSION 10
REFERENCES 13
Preceding page blank
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ABSTRACT
To help evaluate the effects of solid wastes handling and
processing on the roicrobial quality of the environment, a
quantitative study was made of the microbial flora of the
dust in and around a municipal solid waste-sewage sludge com-
posting plant. Air samples were taken with an Andersen volu-
metric sampler used in conjunction with trypticase soy agar
that contained 5% sheep blood and with eosin roethylene blue
agar. Sampling vu>s carried out during the inactive and active
work periods. Samples were obtained from ten different areas
at a height of 5 ft. The highest total microbial counts of
63 and 55 per 0.25 cu ft of air were obtained in the leveling
and metering gate area of the receiving building and in the
rejects hopper area of the processing building. Staphylococcus
aureus, gram-negative bacilli, gram-positive bacilli, and furgi
were present in 911 areas sampled. No colifont: organisms were
among gram-negative bacilli.
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INTRODUCTION
The effects of airborne microorganisms in a number of human
environments have been reported by Robertson, 1967; Greene et al. t
1962; Winslow, 1926; Willia.ns et al.,1956; and Cvjetanovic, 1958.
A study of airborne microorganisms inside municipal incinerators
(Peterson, 1971) has shown the potential health hazard of dust
from municipal solid waste. Other research in this field has in-
cluded a study of airborne microorganisms around ;, sewage treatment
plant (Kenline, 1967); the study indicated that streptococci may
spread several hundred yards from the source.
This study of dustborne microorganisms was carried out at
the Joint U.S. Public Health Service - Tennessee Valley Authority
Composting Project, Johnson City, Tennessee, where the windrow
system was used. The compost was made from ground municipal solid
waste mixed with raw or partially digested sewage sludge. As with
any solid waste handling and processing operation, the compostir.q
process can concentrate and stir up dust that may be a health
h^ard to the persons who come in contact with the dust. In this
case, there fs threat of contamination from both the waste and
the sewage sludge.
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MATERIALS AND HETHQDS
Air sampling equipment and techniques. Air samples were taken
with an Andersen sieve sampler (Andersen, 1958), (Figure 1).
This six-stage multijet sampler separates airborne particles
Into six aerodynamic sizes that cover the range for respiratory
tract penetration. Thus, the organisms reported in the data ar
primarily those that could enter the respiratory tract. Each
of the ?1x stages of the sampler covered a petri dish contain-
ing 26 to 28 ml of solid agar media. Air was drawn through the
sterile sampler at 1.0 cu ft per roin with a vacuum of 15 in of
mercury. Because of the large numbers of organisms involved,
the sampler was run for 15 sec (0.25 cu ft air) to get well
separated 1 to 30 colonies.
Background samples were taken at times of complete in-
activity after the dust had had at least 24 hrs to settle.
Activity samples were taken at times when the dust reached
its maximum levels.
Media. At each sampling site, the sampler was used with two
types of media: tryticase soy agar (TSA, BBL product) that
contained 5% sheep blood and eosin methylene blue agar (EMB,
Difco product). The TSA/blood agar was used to isolate a
wider range of fastidious organisms such as staphylococci,
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STAGE NO.
JET SIZE
-JET VELOCITY
STAGE 1
0.0465" OIA.
3.54 FT/SEC
STAGE 2
0.0360" DIA.
5 89 FT/SEC
STAGE 3
0.0280" DIA.
9.74 FT/SEC
STAGE 4
0.0210" OIA.
17.31 FT/SEC
STAGE 5
OO135" OIA.
41.9S FT/SEC
STAGE 6
0 0100 ' OIA.
76.40 FT/SEC
FIG. t. ANDERSEN SIEVE SAMPLER
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streptococci, and pnaumococci. The EHB agar «
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o
o
RECEIVING HOPPIR
RECEIVING HOPPER CONVEYO
UVEtING & MEURING GATE
EL! VAT ING am CONVEYOR
RFIEC'S HOPPEf
MAGNETIC
RASPER
GRINDER
MIXER
® BUCKtT ELEVATOR
0 GROUND REFUSE STORAGE BIN
© S1UD(.E THICKENER
O SLUDGE COAGULATING TANK
@ SLUDGE HOLDING TANK
© CHEMICALS MIXING TANK
\ «tjtcfrrg~pNl5T-,ii I
,— , GKOUND^iiifutMo WINQBOWS
UN HID COMPOST
I
WEIGHING
n
Uja£fc=S--^
!
; i
A A A A
CURING & STORAGE
_^ »•»*
GRINDING
SCREENING
I
SHIPPING
WINDROWING TURNING
COMPOSTING
FIG. 2. PROCESS FLOW DIAGRAM OF USPHS W COMPOSTING PROJECT. JOHNSON CITY, TENNESSEE.
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transferred to a bel* (9);
• the ground-waste transfer area where the waste
sludge mixture is dumped into a truck (11);
• the windrow area where a 7-day-old windrow is
being turned over (downwind); and
• the curing and storage area where the cured
compost is being transferred to a truck (downwind).
The air temperatures during the study ranged from
15 to 40 F. The week before this sampling, the area
experienced some rain and snow that probably tended
to hold down the outside dust.
RESULTS
Table 1 shows microbial concentrations per 0.25
cu ft, by functional area, during the inactive and
active work periods. During the activity, the heaviest
mlcrobial concentration (63 and 55 organisms per 0.25
cu ft air) was encountered in the leveling and metering
gate area and rejects hoppes* area. The lowest counts
(15 and 17 per 0.25 cu ft air) were observed in the
grinder throwback and premlxer areas.
The general distribution of the predominant micro-
bial types encountered in ":he different sampling areas
differed rather markedly. Thus, Staphylococcus aureus
and alphahemolytic Streptococcus, which are usually
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TABLE 1. MICROORGANISMS ASSOCIATED WITH COMPOST OPERATIONS DUST
Sampling area
Receiving hopper (1)
Leveling and
metering gate (3)
Hand picking (6)
Rejects hopper (5)
Grinder throwback (8)
Premixer (9)
Postmixer (9)
Ground-waste
transfer (11)
Windrow
(7 day old)
Curing and storage
During inactivity
colom'ci/0.25 cu ft
Staphylococcus
aureus
2
5
2
3
1
3
3
2
4
2
a-hemol.
Streptococcus
0
0
0
0
1
0
0
1
0
0
ai
•f**
f «c-
l/l •—
l_ U
js ^O
V.
0
4
'
3
?
4
2
3
5
0
>
*-»
c •«-
i-
O
2
6
3
2
1
4
1
2
5
2
c
3
U.
2
2
G
4
3
2
3
3
2
1
0
6
17
14
12
8
13
9
11
16
5
During activity
colonies/0.25 cu ft
Staohylococcus
aureus
7
22
8
15
5
i
10
12
5
8
a-hemol.
Streptococcus
0
5
1
3
C
1
3
1
2
2
Gram-positive
bacilli
8
11
8
18
6
7
12
5
18
11
01
*J
ty -r-
01 •—
C »-
1 O
fB XI
5
14
15
11
2
5
5
10
10
2
en
c
u.
9
11
14
8
2
3
4
6
3
2
«->
o
22
63
46
55
15
17
34
34
38
25
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considered to be human borne, predominated in the
leveling and metering gate, the rejects hopper, the
post mixer, and the ground-waste transfer areas.
Staphylococcus aureus was Isolated from all areas
sampled. The highest count of dust-borne fungi and
gram-positive bacilli was observed 1n the rejects
hopper area of the processing building. No attempt
was made to characterize gram-positive bacilli and
fungi; gram-negative bacilli were classified under
genus Pseudomonas and genus Proteus. No collform
organisms were isolated.
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DISCUSSION
When discussing data of the kinds presented here, it is
probably most useful to dis<_uss them in relation to other
environmental conditions.
Comparative data from airborne mcrobial populations in
various environments (Winslow, 1926) per 1 cu ft air are
shown below:
Total microbial levels
Environment (colonies per cu ft air)
Country air 56
General offices and schools 95
City streets 72
Factories 113
The levels of microorganisms in the leveMng and metering
gate and in the rejects hopper areas were twice as high as
those in factories. There were, however, no significant
quantitative differences in microfcial levels between the other
composting plant areas sampled and the factories.
The values obtained for dust microorganisms in this com-
posting plant were very low compared with the six municipal
incinerators investigated in a previous study (Peterson, 1971).
The dustiest area of the municipal incinerators had a total
10
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count of 197 colonies per 0.25 cu ft atr. In contrast, the
dustiest (leveling and metering gate) area of the compost plant
had a value of 63 per 0.25 cu ft air. Other studies (Randall
and Ledbetter, 1C67) have shown that air over an activated
sewage sludge waste treatment unit may contain from about 8
to 1170 microorganisms per cu ft, with enteric organisms con-
stituting 19% of the total.
The fact that sewage sludge was used in the process sug-
gested the possibility that enteric organisms might be dis-
seminated into the air. That there were no coliforms isolated
in the sludge-handling areas was "ather surprising. The
absence of coliform organisms in sludge-handling areas may
possibly have been the result of careful housekeeping and
properly designed operational system. To these factors can
be added such considerations as the particle size of the con-
taminants, which determines the rate of sedimentation, and
environmental factors such as temperature, humidity, and air
currents.
\
The distribution of staphylococd and streptococci was
also of particular interest. These organisms predominated in
the leveling and metering gate, the postmixer.and the ground-
waste transfer areas; small numbers were isolated from six
11
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other sampling sites. Stiphylococcus aureus was isolated from
all sampling sites. Staphylococci can survive for long periods
t
in dry air and can easily be transported through the environ-
ment by the movements of air currents.
In summary, the values reported are intended to serve «
a rough indication of the air micrcflora that is constantly
changing because of the movement of air currents and the
settling out of particles. Soirewhat higher microoial counts
would be expected during spring, sunnier, or fall. The rela-
tively clean waste handling operation at the Johnson City
Plant reflected the newness of the plant, the excellent
housekeeping*and the relatively small quantities of waste
beiny handled at sampling-time. Even though the operation is
comparatively clean, however, the possibility of health
hazards should be carefully considered. Using face masks is
recommended in areas of heavier contamination.
If, in the future, epidemiological justification for im-
plementing microbial control measures for solid waste-borne
aerosols becomes evident, this report might serve as a guide-
line of feasibility. The technique* used in this study in-
dicate the parameters which must be considered in a monitoring
program.
12
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REFERENCES
Andersen, A. A., New sampler for the collection, sizing
and enumeration of viable airborne particles.
J. Bact. 76:471-484, 1958.
Cvjetanovic, B. , Determination of bacterial air pollution
in various premises. J. Hyg. 56:163-168, 1S58.
Greene, V. W., D. Vesley, R. G. Bond, and G. S. Michaelsen,
Microbiological contamination of hospital air. I.
Quantitative Studies. Appl. Microbiol. 10:561-566,
1962.
Kenl^ne, P., Studies of microbial air flora areund sewage
treatment plants. Personal communication» 1967.
Peterson, M. L., Pathogens associated with solid waste
processing. Progress report. U.S. Environmental
Protection Agency, Cincinnati, Ohio. SW-49r, 1971.
Randall, C W. and J. 0. Ledbetter, Bacterial air
pollution from activated sludge units. Am. Ind. Hyg.
27:506-519, 1967.
Robertson, P., Microbiological studies of hospital incin-
erator stack effluent. Personal communication, 1967.
Williams, R. E. 0., 0. M. Lidwell, and A. Hirsch, The
bacterial flora of the air of occupied rooms. J.
Hyg. 54:512-523, 1956.
Winslow, C. - E. A., Fresh air and ventilation. New York,
E. 0. Dutton & Company, p. 19-25, 1926.
«U.S.Gcwtrnm*nt Printing Otric*: 1972 — 759-914/3128 Region S-ll
13
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BIBLIOGRAPHIC DATA '• «< T-»« >•«• 2-
SMEET EPA-R2-72-131
4. 1 itir .i:..i Subtitle
MICROBIOLOGICAL STUDIES OF
COMPOST PLANT DUST
D. H. Armstrong and M. L. Peterson
Solid Waste Research Laboratory
National Environmental Research Center
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
12. S|>>n>orin£ DrjiJniVai on Name and AJJiovs
same
3. Kri'jpicnt'j. -4cci-!.KrJs iind Documi-nt Analysis. 17o. l)i s
*Microorganisms, Sludge, Air, Dust, Volumetric analysis, Bacteria,
Fungi
Sewage sludge, Municipal solid waste, Environmental air concentra-
tions, Microbial flora, Andersen volumetric sampler, Trypticase soy
agar, Solid waste management, Staphylococcus aureus, Gram-negative ba-
cilli. Gram-positive bacilli
17e. roSATI l-'ielJ/Gfoup
18. Atailat.iluy Statement
19. •'K'uTiiy < Us- (I hi* |2l. No. of
Kcpo.-tT I 20
20. Scvuiiiy V faV-
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