United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/8-80-034
August 1980
Research and Development
&EPA
A Survey of
Pathogen Survival
During Municipal
Solid Waste and
Manure Treatment
Processes
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5 Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the "SPECIAL" REPORTS series. This series is
reserved for reports targeted to meet the technical information needs of specific
user groups. The series includes problem-oriented reports, research application
reports, and executive summary documents. Examples include state-of-the-art
analyses, technology assessments, design manuals, user manuals, and reports
on the results of major research and development efforts.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/8-80-034
August 1980
A SURVEY OF PATHOGEN SURVIVAL DURING MUNICIPAL
SOLID WASTE AND MANURE TREATMENT PROCESSES
by
Sylvia A. Ware
Ebon Research Systems
Washington, D.C. 20001
Contract No. 68-03-2460-5
Project Officers
Carlton C. Wiles
Laura A. Ringenbach
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency/ nor does mention of trade names or commercial products consti-
tute endorsement or recommendation for use.
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FOREWORD
The U.S. Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health and
welfare of the American people. Noxious air, foul water, and spoiled land are
tragic testimonies to the deterioration of our natural environment. The
complexity of the environment and the interplay of its components require a
concentrated and integrated attack on the problem.
Research development is that necessary first step in problem solution; it
involves defining the problem, measuring its impact, and searching for solutions.
The Municipal Environmental Research Laboratory develops new and improved
technology and systems to prevent, treat, and manage wastewater and solid
and hazardous waste pollutant discharges from municipal and community sources,
to preserve and treat of public drinking water supplies, and to minimize the
adverse economic, social, health, and aesthetic effects of pollution. This
publication is one of the products of that research and provides a most vital
communications link between the researcher and the user community.
This report summarizes studies that evaluated pathogen survival during
solid waste treatment. Methods discussed include incineration, composting,
landfill, and anaerobic digestion.
Francis T. Mayo, Director
Municipal Environmental Research Laboratory
111
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ABSTRACT
Municipal solid waste (MSW) and animal manures may contain microorganisms
that can cause disease in man and animals. These pathogenic microorganisms
include enteric bacteria, fungi, viruses, and human and animal parasites.
This report summarizes and discusses various research findings document-
ing the extent of pathogen survival during MSW treatment. The technologies
discussed are composting, incineration, landfill, and anaerobic digestion.
There is also a limited examination of the use of the oxidation ditch as a
means of animal manure stabilization. High gradient magnetic separation
(HGMS), and gamma radiation sterilization are mentioned as future options,
especially for animal waste management. Several standard methods for the
sampling, concentration, and isolation of microorganisms from raw and treated
solid waste are also summarized.
This report was submitted in fulfillment of Contract No. 68-03-2460-5 by
Ebon Research Systems under the sponsorship of the U.S. Environmental
Protection Agency. This report covers a period of March, 1978 to February,
1980 and work was completed as of March, 1980.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vi
Acknowledgements vii
1. Introduction 1
2. Conclusions 5
3. Recommendations 7
4. Pathogen Survival during
Specific Waste Treatment 8
I. Composting 8
II. Incineration 20
III. Sanitary Landfill 49
TV. Oxidation Ditch 69
V. Anaerobic Digestion 74
VI. Other Processes 78
5. Analytical Methods 80
References 92
Appendix A: Health Aspects of Solid Waste
Disposal 101
Appendix B: Hospital Waste , 103
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FIGURES
Number
1 Flow diagram of a high temperature combustion plant . . 23
2 A comparison of the efficiency of
total bacteria removal from incinerators 30
3 A comparison of the efficiency of
heat resistant spore removal from incinerators. ... 31
4 A comparison of the efficiency of total
coliform removal from incinerators. . 32
5 A comparison of the efficiency of fecal
coliform removal from incinerators 33
6 Air quality of various waste treatment facilities:
average values of total bacteria. ... 44
7 Air quality of various waste treatment facilities:
average values of total coliforms 45
8 Air quality of various waste treatment facilities:
average values of fecal coliforms 46
9 Air quality of various waste treatment facilities:
average values of fecal streptococci 47
10 Cross-section of an experimental sanitary landfill. . . 52
11 Change in total coliform bacteria
with time of leaching 58
12 Change in density of fecal coliforms
with time of leaching . 59
13 Change in density of fecal streptococci
with time of leaching ........... 60
VI
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TABLES
Number Page
1 Some Pathogens and Indicator Organisms Found
in Municipal Solid Waste. ........ 3
2 Composition and Analysis of Composite Samples
of Municipal Refuse .... 4
3 Amount of Soiled Diapers in Municipal Solid Waste ... 4
4 Survival of Pathogens During Composting . . 10
5 Species Investigated by Knoll 16
6 Some Pathogenic Fungi Associated with Composting ... 17
7 Survival of Human Parasites Inserted in Refuse-
Sewage Sludge Windrows . 19
8 Survival of Dog Parasites Inserted in Refuse-
Sewage Sludge Windrows 19
9 Microorganisms Associated with Dust from
Compost Operations. . 21
10 Incinerator Characteristics 22
11 Efficacy of Incinerator Operations in the
Destruction of the Microflora Associated
with Municipal Solid Wastes . . . 24
12 Efficacies of Various Incinerator Designs
in the Destruction of Microflora Associated
with Municipal Solid Wastes 27
13 Characterization of Gram-positive Cocci and
Gram-negative Bacilli ...... 35
14 Average Values of Selected Microorganisms
Present in Microbiological Aerosols
at an RDF Plant . . . . 39
15 Reported Aerosol Concentrations of Bacteria
Found in Ambient Air and Various Working Locations. .- 39
16 Ranking of Hi-Vol Samples Based on Average
Bacterial Levels 41
17 Hi-Vol In-Plant Bacteria Count/Cubic Meter;
High and Low Values (MPN) .............. 42
18 Hi-Vol Ambient Bacteria Count/Cubic Meters
High and Low Values (MPN) .............. 43
19 Range of Chemical Composition of Sanitary
Landfill Leachate ............. 53
20 Occurence of Streptococci in Leachate ......... 55
21 Distribution of Fecal Coliforms and Fecal
Streptococci in Leachates from the Upper Pipe .... 56
22 Microflora of Municipal Solid Waste and
Leachate from Simulated Landfills , . . ....... 63
vii
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TABLES (continued)
23 Operation of a Model Oxidation Ditch 71
24 Survival of Leptospira Pomona and
and Salmonella TyphimuriunT" 72
25 Conditions Favorable to Destruction of Leptospires. . . 73
26 Disposition of Selected Biological Materials 104
viia
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ACKNOWLEDGMENTS
Ebon Research Systems would like to thank our Project Officers, Mr. Carlton C.
Wiles and Mrs. Laura A. Ringenbach, for their assistance throughout this
project. We would also like to thank Dr. William L. West, Howard University
Medical School, and Dr. Lee Richman, Ebon Research Systems, who reviewed
the draft.
Table 3 is reproduced from Peterson, M.L. Soiled Disposable Diapers: A Poten-
tial Source of Viruses. American J. Public Health, 64:912, 1974. With
permission of the copyright owner the American Public Health Association.
Tables 10 and 11 are reproduced from Peterson, M.L.,and F.J. Stutzenberger.
Microbiological Evaluation of Incinerator Operations. Applied Microbiology,
18(1) 8-13, 1969. With permission of the copyright owner the American Society
for Microbiology.
Table 14 is reproduced from two tables in Duckett, E.J. Microbiological
Analyses of Dusts at the Equipment Test and Evaluation Facility. Report No. TR
78-2. National Center for Resource Recovery, Washington, D.C., March 1978.
With permission of the copyright owner the National Center for Resource
Recovery.
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SECTION 1
INTRODUCTION
PURPOSE OF THE REPORT
The purpose of this report is to summarize and discuss research findings
documenting the extent of pathogen survial after waste treatment. The technolo-
gies discussed are composting, incineration, landfill, and anaerobic digestion
since these are common or currently discussed methods of treating solid waste.
There is also a limited examination of the use of the oxidation ditch as a means
of animal manure stabilization. This examination is included since the oxida-
tion ditch has been recently promoted as a means of animal waste management, and
a certain amount of literature is available discussing its environmental
acceptability. High-gradient magnetic separation (HOIS) and gamma radiation
sterilization are mentioned as future options, especially for animal waste
management. Appendix A discusses health aspects of solid waste disposal and
Appendix B briefly examines disposal of hospital wastes.
Given the heterogeneous nature of MSW, it is difficult to sample raw waste
or residue in a representative manner. Methods of sampling, detecting, and
concentrating microorganisms isolated from waste or residue are not always
consistent or reliable, especially for viruses. Section 5 of this report
summarizes the analytical methods used in the studies discussed.
Concentrations of animal excreta present in MSW have not been quantified.
From available studies, it would appear that the greater proportion of fecal
matter in MSW is of animal rather than human origin (Peterson, 1971; Blannon and
Peterson, 1974; Cooper et al_., 1974a; Duckett, 1978).
The detection of various fecal organisms in MSW is evidence of fecal origin
and contamination. While many of these organisms are harmless, some are
etiologic agents which cause disease in man and animals, i.e., they are patho-
gens. Coliforms, streptococci, salmonella, and various parasites have been
isolated from MSW (see Table 1). Enteroviruses have also been detected in MSW»
The presence of these microorganisms in waste, and their survival after various
methods of treatment is an indication that other pathogens (perhaps more
difficult to detect) may also be present in waste and survive treatment. Hence,
a bacteriological and viral examination of raw or treated waste may include an
assay for: total bacteria, total and fecal coliforms, fecal streptococci, heat
resistant spores, and enteroviruses (poliovirus, echovirus, coxsackievirus).
The presence of pathogenic organisms in raw or treated waste is potentially
detrimental to public health. [It's not the fact that MSW is in the land that
it presents a potential problem.] Hanks (1967) has documented possible health
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hazards associated with poor solid waste management (see Appendix A). However,
there is not one epidemiological study which can directly trace outbreaks of
disease to the presence of pathogens in MSW, though there are studies relating
disease to water contamination by sewage sludge and animal manures. Though
various studies have shown that solid waste management is a hazardous occupation
in terms of injury and cardiovascular disease (Sliepcevich, 1955; Anderson,
1964; Cimino, 1975), there is no adequately designed study which shows a
statistically significant difference in rates of respiratory, gastrointestinal
or skin infections among sanitation workers, the group most frequently exposed
to solid waste. Hence, the health implications of the studies documented in
this report are not conclusive.
MSW - CHARACTERIZATION
The U.S. Environmental Protection Agency estimated that in 1971, municipal
solid waste (MSW) generation in the United States was approximately
3.32 Ib/person/day (Lowe, 1974). For a projected growth in solid waste genera-
tion of 3% to 4% annually, an estimated U.S. national average of around
3.91 Ib/person/day in 1980, or an urban area average of 4.33 Ib/person/day
results. Anderson (1972) has projected the generation of over 220 million dry
tons of MSW in 1980.
The composition of MSW is variable and depends on the geographical location,
the season, and the nature of the community generating the waste. Table 2 shows
a representative analysis of MSW collected in a large city. It should be empha-
sized that this analysis is only an indication of the content of MSW. Neverthe-
less, the high percentage of paper products in the refuse is typical. Human and
animal excreta are also found in MSW, the human excreta largely derived from
disposable diapers, and the animal excreta from household pet litter.
Peterson (1974) estimated that 0.65% to 2.5% wet weight of residual solid
waste was soiled disposable diapers (see Table 3). She found that approximately
33% of the diapers contained feces to an average value of 60 g/lb (wet weight)
of diapers, for an average of 0.2 g of feces/lb (wet weight) of solid waste.
Engelbrecht (1973) also reported that an average of 33% of diapers from a
residential area of Cincinnati were stained with feces.
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TABLE 1
SOME PATHOGENS AND INDICATOR ORGANISMS POUND IN
MUNICIPAL SOLID WASTE
Organism
Concentration*
Reference
Fecal streptococci
Total colifonus
Fecal coliforms
Salmonella sp.
Heat resistant spores
Total coliforms
Fecal coliforms
Salmonella sp.
Heat resistant spores
Total coliforms
Fecal coliforms
Total coliform
Fecal coliform
Fecal streptococci
10b (av.)
108 (av.)
107 (av.)
1.7 x 104 6.8 x 104
1.2 x 104 6.2 x 106
2.3 x 104 4 x 105
3.1
3.4 x
x KP
103
1.9 x
5.1 x
132 x 106t
i6t
248 x 10*
10'
1.5 x 104 5.6 x 106
86 x
86 x
396 x
10
6 = =
6 = =
10
Gaby, 1975
Peterson and
Stutzenberger,
1969
Peterson and
Klee, 1971
Peterson, 1971
Cooper et al.,
1974a
* Counts/g
t Sample 1
={= Sample 2
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TABLE 2
COMPOSITION AND ANALYSIS OF COMPOSITE SAMPLES OF MUNICIPAL REFUSE
(Kaiser, 1963)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Corrug. paper boxes
Newspaper
Magazine paper
Brown paper
Mail
Paper food cartons
Tissue paper
Wax cartons
Plastic coated paper
Vegetable food wastes
Citrus rinds and seeds
Meat scraps, cooked
Fried fats
Wood
Ripe tree leaves
Flower garden plants
Lawn grass green
Evergreen
Plastics
Rags
Leather goods
Rubber composition
Paint and oils
Vacuum cleaner catch
Dirt
Metals
Glass? ceramics, ash
Adjusted moisture
23.38%
9.40
6,80
5.57
2.75
2.06
1,98
0.76
0.76
2.29
1,53
2.29
2.29
2.29
2.29
1.53
1.53
1.53
0.76
0,76
0..38
0.38
0,76
Oo76
1.53
6,85
7.73
9.05
100.00
TABLE 3
AMOUNT OF SOILED* DIAPERS IN MUNICIPAL SOLID WASTE, 1971
(Peterson, 1974)
Sampling
Area
A
A
B
B
Date
Feb
April
July
July
Total
Waste Separated
Ib (wet wt)
800
9,200
2,800
3,600
Mount of Diapers
Soiled
Feces-Contaminated
% total waste t
2.5
0.9
0.6f
0.8 +
1.0
0.3
0.2 "I"
0.3 t
* Contaminated with urine or feces
t Mean values from multiple samples
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SECTION 2
CONCLUSIONS
From the literature reviewed, composting appears to be an effective method
of destroying pathogenic organisms provided that sufficient time/temperatures
are achieved. All organisms within the compost should be exposed to thermophi-
lic temperatures of 50°C to 60°C for at least seven days. There is some
evidence that parasitic cysts and ova (especially those of animal rather than
human origin) may survive long periods of composting. It should be emphasized
that though parasites may remain morphologically intact after composting, they
may not be viable.
Various investigators have shown that the extent to which microorganisms are
destroyed during incineration is a function of both the design and the manner of
operation of the incinerator. From available studies it is concluded that all
pathogens should be destroyed provided that the entire solid waste charge
quickly reaches an appropriate temperature. If an incinerator is charged beyond
its capacity, if the waste is too tightly packed, or if operating temperatures
are too low, then it is possible for pathogenic organisms to survive incinera-
tion. These organisms may remain in unburned residue, in quench water, or in
aerosolized form exitting the stack, especially if the stack is relatively
short.
There is also a possibility that pathogenic bacteria and viruses may survive
conditions within the sanitary landfill, and may be leached to ground or surface
water. However, there does appear to be a significant decrease in viral and and
bacterial content of leachate with time of operation or leaching of the fill.
Also, the relatively high temperature (60°C) achieved during the first aerobic
stages of waste biodegradation is inirnicable to many viruses and most pathogenic
bacteria. It has also been shown that the chemical and physical characteristics
of the leachate contribute toward^j5oth~viral and~bacterial inactivatJonl~ ~
Adsorption of viruses onto material in the fill is likely, and partly
explains the low rate of recovery of viruses from landfill leachate. It is not
clear whether viruses are inactivated when they are adsorbed onto particulate
matter in the fill.
No studies were available documenting the possibility and extent of pathogen
survival in anaerobically digested municipal solid waste. Studies of digested
sewage sludge have shown survival of pathogenic organisms at both mesophilie
temperatures (viruses, bacteria, parasites), and thermophilic temperatures
(viruses). For these studies, temperature, time of residence, and degree of
mixing were all factors determining the extent of pathogen survival.
5
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From the limited material presented, it appears that prolonged survival of
some of the more common pathogens present in animal wastes is possible within
the oxidation ditch environment. However, methods of operating field facilities
vary greatly, and the environmental characteristics of even one specific ditch
may change daily.
Though various studies have shown that pathogenic organisms present in muni-
cipal solid waste may survive treatment, it should be emphasized that there is
not one sound epidemiological study correlating an outbreak of any infectious
disease in this country with the pathogen content of treated wastes. Also,
there is no conclusive evidence that workers exposed to pathogen-containing raw
or treated municipal solid waste on a daily basis have a statistically signifi-
cant increase in gastrointestinal, respiratory, or skin infections as compared
to those of the populace at large. Hence, the health significance of pathogen
survival in solid waste after treatment is not at all clear.
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SECTION 3
RECOMMENDATIONS
• It has been established that MSW is contaminated with human and animal
excreta, and contains fecal microorganisms some of which may be pathogens.
However, the potential hazard presented by this contamination is not clearly
defined.
• Methods for isolating viruses from raw and treated waste and leachate need to
be improved. It is often not clear whether samples are truly negative for
viruses, or that their presence is undetected.
• Given reports of possible parasitic survival in composting sludge and
refuse/sludge mixtures, there is a need to clarify exactly how effective the
process is in destroying human and animal parasitic ova and cysts. One
recent study reported that parasites remain morphologically intact for
more than 49 days in refuse/sludge compost. However, no determination was
made of their viability. Any future study conducted should make this
determination to remove ambiguities.
• The extent to which pathogenic fungi survive composting should also be
determined.
• The most effective methods of operating an incinerator to ensure pathogen
destruction should be clearly delineated.
• The behavior of microbes in the sanitary landfill is not well understood.
This is especially true for viruses. Any investigation to correlate specific
chemical, biological, and physical characteristics of the fill environment
with microbial inactivation would be very useful.
• The extent to which a virus retains its infectivity when absorbed onto solids
is also not well-established. A study of viral inactivation on solid waste
components could be conducted in tandem with a study of factors effecting
elution of virus from the waste.
• There is a need to determine the effectiveness of anaerobic digestion as a
means of pathogen destruction. No relevant data for MSW were found in the
literature. Reports on the extent of virus inactivation, and bacterial and
parasitic destruction in digesting sludge suggest that the conditions of
anaerobic digestion may not be sufficient in effecting complete destruction
of the microbes.
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SECTION 4
PATHOGEN SURVIVAL DURING SPECIFIC SOLID WASTE TREATMENTS
I. COMPOSTING
The Process
Biological deconposition of organic solids by aerobic microorganisms results
in formation of a stable humus-like material and production of carbon dioxide
and ammonia. The process is termed composting and the humus-like material re-
maining is compost. Though composting may also be accomplished by anaerobic
organisms this is a much slower process and intermediate products formed smell
unpleasant. Decay may be initiated by psychrophilic, mesophilic, or
thermophilic organisms,- however, it usually proceeds through mesophilic to
thermophilic digestion (45° to 60°C).
The process reduces the mass and volume of the organic material while in-
creasing its density (Finstein and Morris, 1975). Thus, composting waste
material before land disposal will both extend the life of a landfill, and make
it more physically stable (Finstein and Morris, 1975). As an alternative to
landfilling, a benefit is that the humus can be applied to the soil as both a
conditioner and a fertilizer.
A variety of solid wastes may be composted including municipal solid waste
(MSW), agricultural plant wastes, manures and sewage solids. Mixtures of dif-
ferent wastes are often employed to provide a satisfactory nutrient balance for
growth of microorganisms, and to improve the physical characteristics of the
compost pile.
Before composting, the solid waste may be pretreated though this is not
essential. MSW, for example, may be sorted, magnetically separated, ground, and
undergo flotation, ballistic separation, or air classification. The moisture
content of MSW must be raised from about 30% to 60%e This may be accomplished
by mixing with sewage sludge, which also adds nitrogen to lower the C/N ratio.
Sewage sludge and animal manures on the other hand must be dewatered prior to
composting since at high water concentrations, air flow through the composting
material is impeded and aerobic conditions do not prevail.
Various composting techniques have been developed, principally in Europe and
Asia, though to a limited extent in the United States. Material to be conposted
may be contained in trenches in the ground, loaded into rotating drums, silos,
vertical bins or open tanks, stacked in open windrows or otherwise deployed.
Aeration may be accomplished by forcing air through the stack, or by mechanic-
ally turning or agitating the compost material. Depending on the technique and
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nature of the feed material, the process may be completed in almost any period
from 4 to over 200 days. A period of curing may follow digestion to ensure the
biological stability of the compost. After curing, the compost may undergo
further screening and grinding treatment.
Both batch and continuous processes have been developed. It is possible to
process wastes continuously in a tiered silo where there is a temperature gradi-
ent from the top to the bottom deck. This temperature difference means that
mesophilic organisms predominate at the top of the silo, while thermophilic
organisms are found at the bottom.
Continuous thermophilic composting is also possible where incoming waste is
heated by resident compost to eliminate the early mesophilic growth stage.
Inoculation with active thermophiles may be practiced in continuous composting
(Finstein and Morris, 1975). While most studies have indicated that microbial
inoculation of either mesophilic or thermophilic organisms is unnecessary, some
manufacturers inoculate their wastes prior to digestion (Wilde, 1958; Wiley,
1962; IPT, 1972; Finstein and Morris, 1975).
Survival of Pathogens
Pathogen destruction has often been assumed to occur during composting
because of the relatively high temperatures achieved. Some reports of total
pathogen destruction during composting are based on knowledge of the time/temp-
erature required for thermal death, and the recorded temperature of a particular
compost heap. These reports do not always contain evidence that sampling of the
compost was undertaken in order to confirm the destruction of specific micro-
organisms. More recent studies have included pathogen survival tests during
composting of various wastes by different methods. Some studies sample for
pathogens naturally occuring in the wastes, while others inoculate known
pathogens into the compost to determine their viability during the composting
process. Table 4 summarizes data from several of these pathogen survival tests.
The survival of pathogenic organisms during composting appears to depend on
two factors;
• the temperature achieved and the time of maintenance of that temperature
(Morgan and Macdonald, 1969; Wiley and Westerberg, 1969; Gaby, 1975).
• antibiotic action or antagonistic effect between organisms (Knoll, 1959;
Knoll, 1963)
It is generally agreed that most of the heat generated during composting is
produced by respiration of aerobic microorganisms attacking the carbon
containing wastes (Finstein and Morris, 1975). The growth of these microorgan-
isms depends on the moisture content and temperature of the compost, as well as
the availability of air and nutrients. Under favorable growth conditions,
temperatures in excess of 70°C are achieved within less than a week (Finstein
and Morris, 1975).
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TABLE 4
SURVIVAL OF PATHOGENS DURING COMPOSTING
Compost
Refuse/sew-
age sludge
Nightsoil &
"other
wastes"
Method
Open-pile,
2 turnings
per week
Not ident-
ified
Species
Not ident-
ified
Ascaris
eggs
Duration
(days)
6 to 8
weeks
50 to 60
Temp.
(°C)
65° to 66°
(max. )
60° to 66°
Comments
Pathogens destroyed;
species not identified;
no time/temperatures
2,000 Ascaris eggs/g
in fresh waste — only
100/g "largely"
degenerated or dead
after a week
Reference
Seabrook ,
1954
Stone,
1949
Refuse/
night-
soil
Refuse/
sludge
Refuse/
sludge
Layering of
equal wts. of
refuse/night-
soil in shallow
pits, top layer
of soil, no turn-
ing, anaerobic
Ascaris
eggs
10 to 15
40°
(max.)
Salmonella sp.
Shigella sp.
Undisturbed open Salmonella sp.
windrow, cultures
inoculated in gel-
atine capsules +
small bags of ground
refuse/sludge
50
20° to 70°
(range)
Decrease in viable
count irregular; after
3 to 5 months tended to
be negative though some
pits still gave viable
count. After 6 months
all counts negative
No test bacteria re-
covered
Bhaskaran
e_t al.,
1957
Knoll,
1963
In ampules in-
serted into
windrows
S. paratyphi 7 to 9
S. paratyphi 257
50°
(max.)
45°
(max.)
Destroyed
Resistant up to 247
days; complete de-
struction 10 days
later
Knoll,
1963
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Table 4 (continued)
Compost Method Species Duration
(days)
MSW/ Open windrow, Salmonella sp. 7 to 21
sewage mechanically Shigella sp.
sludge turned every few
days, moisture
content 50% to
60% Poliovirus 3 to 7
type 2
Human parasitic 7
cysts and ova
Dog parasitic 35
ova
Leptospira 2
Philadelphia
Histoplasma 26
capsulatum
Aspergillus 14
fumigatus
Temp.
(°C)
49° to 74°
(range).
49°
(max. )
60°
(max. )
72° (max.) on
day 20, 2 in.
depth
66° on day 27
mid-depth
49°
(max. )
49°
(max. )
60°
(max. )
36°
(day 14)
43°
(day 14)
Comments Reference
Disappeared whether Gaby,
naturally occurring or 1975
inserted under control-
led conditions
Inactivated 3 to 7
days after insertion
Disintegrated after
7 days exposure
Ova found intact after
35 days at both 2 in.
and mid-depth. Not
known if ova viable or
not
Very sensitive, did
not survive 2 days
One sample positive
taken from 2 in.
depth on day 26
No samples positive
after day 26
Positive at 2 in. depth
Positive at toe
No fungi isolated at day 35
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Table 4 (continued)
Compost
Swine
waste/
5% straw
Sludge/
refuse
Method
Thermophilic
windrow, mech-
anically turned
20 times per
week
American open
windrow system,
50% moisture
Species
Enteric
bacteria
Mycobacterium
tuberculosis
Duration
(days)
14
10
Temp.
60°
(max. )
65°
(av.)
Comments
Destroyed, early in-
crease in organisms
before thermophilic
temps, reached
No viable organisms
found in inserted
sample containers
Reference
Savage
et al . ,
1973
Morgan and
Macdonald,
1969
averaging 65° by
third day
21
Refuse
Night-
soil
Windrow com-
posting, 2
turnings
Ascaris eggs
Endamoeba
histolytica
(cysts)
Endamoeba
coli (cysts)
10
3
weeks
60°
(day 21)
65°
(av.)
60°
(av.)
For one windrow
only, viable organ-
isms recovered through
day 17. By day 21
no viable M. tuberculosis
No viable organisms
by day 10
Cysts more easily des- Scott,
troyed than Ascaris. 1953
Ascaris eggs "usually"
destroyed by day 15
-------
Table 4 (continued)
Compost
Refuse
Method
Windrow
Species Duration
(days)
Mycobacterium phlei 9 months
(Sept.-
Salmonella abortus June)
Temp.
(°C)
87°
(av.)
Comments
All sjjecies perished
Reference
Jansen and
Kunst,
1953
equi
Micrococcus aureus
Bacillus subtilis
M. phlei
B. subtilis
Salmonella
typhiitiurium
Pseudomonas
aeruginosa
3 months
(Dec.-
March)
68°
(max.)
All destroyed but
B. subtilis spores
in dry state still
viable
Erysipelotrix
rhusiopathiae
Raw Composting bin Salmonella
sewage forced out newport
sludge from bottom,
controlled re- Poliovirus type 1
circulation
around bin Ascaris lumbricoides
Candida albicans
60° to 70° All species destroyed
within 4 hours. Polio
virus type 1 inacti-
vated within 1 hour.
Wiley and
Westerberg,
1969
C. albicans most resistant
still viable at 28 hours
-------
Aerobic conditions may be promoted by turning of the compost or by addition
of a material such as straw to produce air pockets within the decomposing waste.
However, too frequent turnings will reduce the temperature and slow the process.
Savage et al_. (1973) have demonstrated that with addition of 5% (wt/wt) straw
and mechanical turning of swine waste 20 times per week, that the temperature
rises to 60°C within three days. The more rapidly the temperature rises to the
thermophilic range, the sooner the pathogenic organisms will be destroyed.
Savage et al. also reported an increase of Salmonella sp., fecal coliforms
and fecal streptococci during the mesophilic stage of composting, though all
enteric bacteria were destroyed within two weeks of attaining thermophilic
conditions.
In a study of refuse/sewage sludge composting, Gaby (1975) demonstrated that
fecal streptococci maintained populations as high as 10 /g even at temperatures
of 55° to 60°C. He found a consistent inverse relationship between the number
of total and fecal coliforms and the windrow temperature. The coliforms
appeared to be more heat sensitive than the streptococci, being reduced to less
than detectable levels at 49° to 55°C. Though salmonella species were often
isolated from raw sewage sludge, Gaby did not detect salmonella or shigella
species in compost after seven days exposure. All samples were negative for
coagulase-positive staphylococci after a day of composting except for one sample
isolated on the 49th day.
The work of Gaby was part of a major study to establish the technical feasi-
bility of composting municipal refuse with or without sewage sludge jointly
undertaken at Johnson City by the Environmental Protection Agency and the
Tennessee Valley Authority. The project also included insertion studies with
Mycobacterium phlei (Stone and Wiles, 1975). M. phlei cultures were grown on
Lowenstein Jensen (L-J) agar slants at 45°C for three days. All samples were
prepared in duplicate (136 sets total) and inserted into 12 windrows at depths
of 2 in., mid-depth (1 1/2 ft), and in the toe on day 0 or day 14. Duplicate
slants were removed at selected times and subcultured by washing with sterile
phosphate buffer (0.5 ml), transferring to a new Lr-J slant, and incubating at
37°C for at least 10 days.
No samples inserted on day 0 at mid-depth were viable after 14 days.
Temperatures achieved at mid-depth averaged in excess of 60° for at least two to
three weeks. Generally seven days at 53°C resulted in destruction of the micro-
organisms. One viable sample was retrieved from mid-depth at 59°C on the
seventh day of composting, though later samples were not viable.
The higher the temperature recorded, the shorter the time exposure necessary
to destroy the pathogen. Viable cells were found after 49 days at the depth of
2 in. where the temperature peaked at 33°C. Viable cells were also found up to
21 days where the maximum temperature recorded was 48°C.
Morgan and Macdonald (1969) conducted survival studies of the avirulent
Mycobacterium tuberculosis var. hominis at the Johnson City plant. Samples were
inserted in the compost during the fall, winter, spring, and summer months. M._
tuberculosis was normally destroyed by the 14th day of composting when the
14
-------
average temperature was 65°C. For one windrow, all microorganisms were des-
troyed by temperatures not exceeding 60°C.
Several studies have compared the destruction of pathogens in the summer and
winter compost heap, where maximum temperatures achieved might be expected to
differ. Jansen and Kunst (1953) examined the survival of a number of micro-
organisms placed in hermetically sealed tubes, and buried in both a summer and a
winter dump. They chose to study mainly non-pathogenic organisms with similar
resistance behavior to related pathogens as a "safety precaution." Summer dump
temperatures (September to June) were shown to have risen above 87°C, but did
not exceed 98°C (as shown by melting-point of chemicals sealed with the
cultures). None of the microorganisms buried (Mycobacterium phlei, Salmonella
abortus equi, Micrococcus aureus, Bacillus subtilis) survived as dry or wet
cultures. Wet and dry controls kept at room temperature still contained viable
cells in June.
The maximum temperature of the winter dump (December to March) was about
68°C. Mycobacterium phlei, Salmonella typhimurium, Pseudomonas aeruginosa and
Erysipelotrix rhusiopathiae were all destroyed during the process, whether
buried as dry spores or in a liquid medium. Bacillus subtilis spores were still
viable, though B. subtilis in the liquid state was destroyed. New growth was
demonstrated for all the controls kept in the laboratory by the investigators.
Here, not only was there a demonstration of the importance of temperature for
pathogen destruction, but an indication that moisture content is also important.
Knoll (1959) also investigated survival of pathogens in both summer and
winter windrows of mixed refuse/sludge (see Table 5). Gelatin capsules, inoc-
ulated with mixed and pure cultures of Salmonella sp., were placed in nylon bags
of MSW/sludge, and then buried in the windrows in three different positions as
indicated below. Temperatures at the three locations were measured daily.
After 50 days (both summer and winter windrows), none of the bacteria were
recovered from the buried samples, though all of the controls contained viable
cells. In a later study, Knoll (1963) demonstrated that at average temperatures
of 45°C, S. typhi were viable up to 247 days after inoculation of a refuse/
sludge windrow.
While most studies have stressed the importance of achieving thermophilic
temperatures as quickly as possible, Strauch (1964) demonstrated that this is
not true for spore-formers. Bacillus anthracis, for example, is more easily
killed when at the vegetative stage of growth. As germination takes place below
55°C, destruction of the organism is certain if the temperature is kept below
55°C for three days to permit germination, after which an increase in
temperature (above 55°C) destroys the organism after three or more weeks of ex-
posure (moisture content <40%). When the temperature does not exceed 55°C,
viable organisms have been isolated after 231 days (Golueke and McGauhey, 1970).
While the interior of the compost heap may reach thermophilic temperatures,
the outer layers often do not reach 55°C. Fungi colonies are known to persist
at the cooler outer edges (McGauhey et cd., 1953; Finstein and Morris, 1975).
Many species of fungi have been detected in compost heaps, including human
pathogens (see Table 6). When the compost is turned, the temperature drops
temporarily. There is the possibility that the interior may be recolonized by
15
-------
TABLE 5
SPECIES INVESTIGATED BY KNOLL
Summer Compost
Winter Compost
Mixed
Culture
Salmonella typhi
S. typhimurium
S. infantis
S. typhi
S. arechavaleta
S. litchfield
Pure
Culture
None indicated
S. para typhi B.
S. infantis
Summer Compost
Winter Compost
the fungi or other microorganisms which may have settled on the compost from the
air. Chang and Hudson (1967) noted reinvasion of the interior by thermophilic
fungi at around 50°C. As the compost cooled from a peak of 67°C, mesophilic
fungi reappeared. Gaby (1975) did not detect the pathogenic fungi Blastomyces
dermatitidis and Histoplasma capsulatum in samples of MSW/sludge compost, though
other genera were common, especially during the cooling stage (Mucor, Rhizopus
Penicillium, Aspergillus, Cladosporium and Cephalotecium). Seeded studies with
various fungal species (Histoplasma capsulatum, Blastomyces dermatitidis,
Geotrichum candidum and Aspergillus fumigatusT showed that none of the organisms
survived 27 days in the windrow at temperatures up to 60°C (Gaby, 1975). How-
ever, one viable sample of H._capsulatum was isolated after 26 days of exposure
from the 2 in. depth of the windrow where temperatures did not exceed 49°C.
Samples withdrawn from mid-depth at day 14 and day 24 were also positive for H.
capsulatum.
For poliovirus type 1 in raw sewage sludge, Wiley and Westerberg (1969)
reported inactivation after only one hour at 60° to 70°C. Gaby (1975) reported
that poliovirus type 2 was inactivated between three to seven days after
insertion in MSW/sewage sludge compost. The maximum temperature recorded for
the windrow as 49°C.
Knoll (1959, 1963) demonstrated that elevated temperatures are but one
factor accounting for pathogen destruction during composting. Antibiotic
inhibitors or mutually antagonistic effects in the mixed culture of the compost
pile also result in pathogen kill. Knoll demonstrated this by inoculating pure
cultures of Salmonella paratyphi B and S. cairo into a composting material held
at a constant temperature of 50°C and relative humidity of 50%. S. paratyjahd
were killed within two days, while S. cairo survived seven days. Identical
cultures of the two species were incubated at 50°C in the laboratory (with 50%
16
-------
TABLE 6
SOME * PATHOGENIC FUNGI ASSOCIATED WITH COMPOSTING
(Golueke and McGauhey, 1970; Finstein and Morris, 1975; Gaby, 1975)
Genera
Species
Disease
Torula
histolytica
Sporotrichum
schenckii
Candida
albicans
Geotrichum
sp_.
Aspergillus
Mucor
Penicillium
sp.
Cryptococcosis
(chronic, frequently
fatal attacks on
meninges and CNS,
maybe lungs, viscera,
skin and joints)
Sporotrichosis
(formation of nodules,
ulcers and abscesses
on skin and super-
ficial lymph nodes)
Moniliasis
(acute or subacute
infection of skin or
mucuous membranes
may localize on skin
nails, mouth, vagina,
bronchi, lungs)
Geotrichosis
(lesions of mucous
membranes resemb-
ling thrush, in-
fection of bronchi
and lungs)
Infections of
external ear, granu-
lomatous lesions in
skin, nasal sinuses,
bronchi, lungs.
* Not a complete listing.
17
-------
moisture). S. paratyphi were destroyed within eight days, while S. cairo sur-
vived in the incubator for 17 days.
In a related experiment, Knoll again examined the survival of S. cairo and
S. paratyphi B. He prepared an aqueous extract from two day old refuse/sludge
compost (at 50°C), and sterilized the extract. Pure extract, extract plus equal
volumes of bouillon, and a bouillon control were inoculated with one of the
species, and divided into four test series maintained at 37° and 50°C. At 50°C,
S. paratyphi disappeared from the extract plus bouillon after 10 days, from pure
extract in 16 days and from the control after 30 days. The more resistant S.
cairo survived 14 days in the bouillon plus extract, 24 days in pure extract,
and 30 days in the control. Figures quoted above are the maximum values
recorded; for some extracts time-to-kill was much shorter. Knoll has postulated
that the bactericidal effects may be caused by several substances rather than
one inhibitor. However, Gaby (1975) was unable to demonstrate either
bactericidal or bacteriostatic action for a wide variety of gram positive and
gram negative bacteria found in composted solid waste/sludge mixtures.
Many resistant forms of parasites are apparently destroyed during com-
posting. Stone (1949) reported destruction of Ascaris eggs in night soil (60°
to 66°C) after 50 to 60 days. Bhaskaran et al. (1957) found that at 40°C,
Ascaris eggs significantly decreased in viability in solid waste/night soil
compost after 15 days. However, some viable eggs were found in certain pits
even after 6 months. However, the compost was never turned and so anaerobic
conditions prevailed. Scott (1953) reported destruction of Ascaris eggs and
cysts of Endamoeba histolytica and Endamoeba coli within three weeks of windrow
composting at an average temperature of 60°C. The cysts were more easily
destroyed than the Ascaris eggs which were usually destroyed by the 15th day.
In parasite detection studies of refuse/sewage sludge compost, Gaby (1975)
reported that 8 to 135 samples were positive for parasites (protozoa, cestodes,
and nematodes) after 49 days of composting. Three percent of all compost
samples (day 0 to day 49) contained one or more parasitic ova or cysts. Though
the parasitic forms remained morphologically intact, no determination was made
of their viability.
In related insertion studies, Gaby demonstrated that while human parasites
inserted into refuse/sludge windrows disintegrated within seven days (Table 7),
dog parasites persisted in the compost for more than 35 days (see-Table 8).
Ascaris, Trichuris, Necatur, Ancylostoma, and Hymenolopsis were intact to the
end of the composting process. Again no determination was made of their
viability.
Belding (1958) has shown that the ova of Trichuris trichuria, Necator ameri-
canus, Ancylostoma duodenale, Ascaris lumbricoides and Hymenolopsis diminuta are
destroyed by time/temperature conditions less severe than those prevalent during
composting. Keller (1951) found that temperatures of 54° to 55°C for two hours
inactivated Ascaris ova in digested sludge. Krige (1964) could not detect
Ascaris ova in municipal compost where the temperature of the entire mass was
maintained at 60°C for five days, and stored for an additional 35 days before
disturbing. The work of Scott reviewed previously also suggests that the
remaining intact parasites found by Gaby could not have been viable.
18
-------
TABLE 7
SURVIVAL OF HUMAN PARASITES INSERTED IN REFUSE-SEWAGE SLUDGE
WINDROWS 9-5-68 TO 10-2-68
(Gaby, 1975)
Day
0
7
14
21
28
Depth
Midpoint
Midpoint
Midpoint
Midpoint
Midpoint
Tenp
op
140
153
159
141
Cysts
^C E. nana E. histolytica Hookworm ova
-H-+ ++ +-H-
60
67
71
61 - -
(+++) - Heavy infestation-many cysts or ova observed in wet mount.
(++) - Several cysts or ova observed in wet mount.
(-) - No cysts or ova observed in wet mount.
TABLE 8
SURVIVAL OF DOG PARASITES INSERTED IN REFUSE-SEWAGE SLUDGE WINDROWS
12-11-68 TO 1-20-69
(Gaby, 1975)
Temp. Q/a
Day Depth °F °C Hookworm Tapeworm Trichurius
0 2", Mid — —
6 2" 137.5 59
Mid — — -H-+ +++ x
20 2" 159 71 X +++ +++
Mid — — +-H- +++ +++
27 2" 120 49 +++
Mid 150 66 +++
35 2" 124 51 +++
Mid x X x
(+++) - Heavy infestation; large numbers of intact ova observed in wet
mounts.
(X) - Contaminated, lost or broken tube.
(—) - Temperature not indicated.
19
-------
Conditions within the Composting Plant
Armstrong and Peterson (1972) have studied the microbial flora in and around
a MSW/sewage sludge composting plant. Methods of sampling are discussed in
Section 5. Samples were taken during active and inactive work periods. Sta-
phylococcus aureus, gram negative and gram positive bacilli and fungi were found
at all locations sampled (see Table 9 for locations and colonies). S. aureus
and Alphahemolytic streptococcus predominated during activity, with highest
values of gram positive bacilli found at the rejects hopper. Fungi levels were
high at the leveling and metering gate, and the hand picking area. No enteric
coliforms were detected in the air.
Total microbial levels were as high at the leveling and metering gate and
the rejects hopper areas as reported values in factories (Winslow, 1926).
Levels at other locations were not significantly different from factory levels
and were much lower than reported values for municipal incinerators and RDF
plants (q.v. Incinerators). Armstrong and Peterson concluded that the rela-
tively low microbial counts resulted from "excellent housekeeping," the handling
of only small amounts of waste, and the newness of the plant.
Summary
Composting appears an effective method of destroying pathogens provided that
sufficiently high temperatures are maintained for long enough periods of time.
All organisms within the compost must be exposed to temperatures of 50°C to 60°C
for at least seven days. This is facilitated by turning of the compost. While
it seems that most pathogens are destroyed, some species may survive. Espec-
ially of interest in this regard are pathogenic fungi and parasitic ova. It
should be emphasized, that though pathogenic organisms may remain morphol-
ologically intact after composting, the viability of the remaining organisms has
not been established.
II. INCINERATION
The Process
Incineration is a method to reduce the volume and weight of municipal solid
waste, animal manures and sewage sludge. After burning of MSW, the residue re-
maining (10 to 15% by volume of original change) is landfilled. There are many
designs of incinerators from the older batch fed models to more modern continu-
ous rotary kilns.
In the conventional batch plant, refuse is stored in a giant refuse pit,
typically 30 feet deep, 100 feet long and 20 feet wide (IRT, 1972). The refuse
is delivered by overhead crane to a feedhopper mechanism, which regulates feed-
ing of refuse onto combustion grates in the primary combustion chamber. The
grates agitate the refuse to present maximum surface area for combustion, in a
conventional furnace, air is kept in excess (150 to 200%) to keep furnace temp-
eratures down to around 650° to 1095°C. Combustion gases from the primary
combustion chamber are further incinerated in a secondary chamber. Solids
remaining and unburned material are drenched with water in a residue bin. Air
pollution control equipment used may be electrostatic precipitators, wet scrub-
bers or bag filters.
20
-------
TABLE 9
MICROORGANISMS ASSOCIATED WITH DUST FROM COMPOST OPERATIONS*
(Armstrong and Peterson, 1972)
(
w
3
u
b w
O D
rH OJ
Sampling area -c D
(0
ti
Receiving hopper (1) 2
Leveling and
metering gate (3) 5
Hand picking (6) 2
Rejects hopper (5) 3
Grinder throwback (8) 1
Premixer (9) 3
Postmixer (9) 3
Ground -waste
transfer (11) 2
Windrow (7 day old) 4
Curing and storage 2
jNun-operacing 1 i
H W W
4-> D OJ 0) 3
>i 0 > > 0
rH O -i-l •'-1 O
Q O 4-> 4-> Q
P y -i-i -H to -H O W
93 O W i— I tjn— I OD
£ 4-1 O -— 1 (UrH r- 1 i J-i
fOO) IU IO -H r— 1 .CD
£>-! Era E<0 Cn 03 difO
CU4J TOJ2 fOJD C 4J (C
r-l tf) VJ M 3 O 4-1
< O O £ H CO
002267
0 4 6 2 17 22
0 1 3 3 14 8
0 3 2 4 12 15
121385
0 4 4 2 13 1
0 2 1 3 9 10
1 3 2 3 11 12
0 5 5 2 16 5
002158
UJJtJLd Lilly J
O
•H W
£3 Si SI
i— 1 O -H •«-!
O O 4-> 4->
SO -iH -H (0 -i-l
(1) O W i— 1 Dli— 1
x; 4-1 o 1-1 a; --H
1 DJ &••-* C -H
03 0) 1 O TO -H iH
.Ci-i6.<0 En3 en fa
Dj4-ifoJ3 n3J3 C 4-1
r^cn >-i M DO
rtj C3 O fcj c-i
0 8 5 9 29
5 11 14 11 63
1 8 15 14 46
3 18 11 8 55
0 6 2 2 15
1 7 5 3 17
3 12 5 4 34
1 5 10 6 34
2 18 10 3 38
2 11 2 2 25
*Microorganisms given in counts per 0.25 ft.
-------
In the system diagrammed in Figure 1, MSW is periodically charged into the
top of a vertical furnace which is supplementally heated by air from a super
blast heater to 1425° to 1650°C in the gas igniter. Slag from the base of the
gasifier and the igniter flows into a water quench tank (not shown). After
cooling, the gases are cleaned of particulate matter in an emission control
system.
The design and operating characteristics of four incinerators investigated
for pathogen survival are shown in Table 10. These incinerators, located in
Cincinnati and Chicago, were evaluated for efficacy in destroying bacteria by
Peterson and Stutzenberger (1969).
TABLE 10
INCINERATOR CHARACTERISTICS
(Peterson & Stutzenberger, 1969)
Incinerator
Characteristics
Design capacity*
No. of furnaces
Feed mechanism
Grate
I
500
2
Continuous
Traveling
II
500
4
Batch
Circular
III
1,200
4
Continuous
Rotary-kiln
IV
200
2
Batch
Reciprocating
Operat. Temp. 1,800°-2,000°F 1,800°-2,000°F 1,2000-1,700°F 1,800°-2,000°F
(primary)
650°-925°C
980°-1,090°C 980°-1,090°C 1,700°-2,200°F 980°-1,090°C
(secondary)
925°-l,200°C
Duration of burn- 1.75-2.0 1.5-1.75 0.5-1.5 1.0
ing (hr)
Total burning rate 22 20 50 6.5
(tons/hr)
Quench water recir- No No quench water Yes No quench water
culated
Estimated volume 80-85% 80-85% 80-85% 80-85%
reduction
* Expressed as tons per 24 hr."
22
-------
Incoming Municipal Refuse
air
super
blast
heater
NJ
OJ
gasifier
vertical
silo)
slag
gas
igniter
exhaust
gas
cooler
emission
control
Figure 1. Flew diagram for a high temperature combustion plant
(IKT, 1972)
-------
Pathogen Survival
Because of the high temperatures achieved, it has often been assumed that
pathogen destruction is complete on incineration. Peterson and Stutzenberger
(1969) showed that due to inadequate incinerator design and/or operations, that
significant numbers of coliforms and heat-resistant spore-formers survived in
the residue after incineration.
It should be remembered that this residue is destined for landfill. Of the
four incinerators described in Table 10, fecal coliform levels were lowest for
incinerators # IV (< 1 count/g) (see Table 11).
Incinerators # II and # III also accomplished significant reductions of
fecal coliforms. As shown in Table 11, total cells and total coliforms detected
in incinerator # IV residue were also significantly lower than in the other
three incinerators. Note that this incinerator was the smallest in capacity,
and burned waste at a much slower rate (6.5 tons/hour). Table 11 gives the bac-
terial populations found in both the solid waste charge and the residues for
these incinerators.
TABLE 11
EFFICACY OF INCINERATOR OPERATIONS IN THE DESTRUCTION OF THE
MICROFLORA ASSOCIATED WITH MUNICIPAL SOLID WASTES
(Peterson and Stutzenberger, 1969)
Material
Bacterial
Population*
Incinerator Design
I
Solid waste
Residue
Total cells
Heat resistant t
Total coliforms
Fecal Coliforms
Total cells
Heat resistant t
Total coliforms
Fecal coliforms
7.6
4.2
6.2
9.1
4.4
1.0
1.5
2.4
X
X
X
X
X
X
X
X
IO7
106
io4
107
10~"
IO4
10J
II
4.1
6.8
4.8
4.0
1.7
2.0
2,3
9
X
X
X
X
X
X
X
10^
10
IO6
10 b
IO6
IO4
IO2
5.6
2.7
5.4
1.2
1.2
3.9
4.1
5
III
X IO7
X IO4
X 10;?
X IO5
X IO6
X 10 3
X 101
IV
3.8 X
1.7 X
1.2 X
2.3 X
7.1 x
4.4 X
5
1
108
IO4
IO4
10 4
10 3
103
* Expressed as counts per gram.
t Expressed as spores per gram.
It was found that residues with a high bacterial population (especially # I)
contained unburned vegetables, animal wastes and newspapers, while the residue
from incinerator # IV was more completely burned.
In a related study, Peterson and Klee (1971) detected Salmonella sp in solid
waste prior to incineration, and after incineration in quenched residue and
quenchwater from incinerator # I. They pointed out that the recorded
temperatures achieved by the four incinerators were theoretically high enough to
kill even the most heat resistant spores. However, because of the high survival
24
-------
rate of both heat susceptible and heat resistant microorganisms, it is clear
that masses of the charged waste do not reach these temperatures.
The following reasons for incomplete combustion have been given:
• Organic waste is a poor conductor of heat. Also, as the charge
burns, water is formed, and the temperature of the wet mass falls
several hundred degrees.
• The incinerators may be charged beyond their capacity.
• The bulk density of the residue may prevent complete incineration
and thus sterilization does not take place.
• The forced draft in the furnace carries microbial aerosols up the
stack at high velocities. Hence, a sufficient time/temperature is
not achieved for sterilization.
• The design of the furnace may be inadequate. For example, if the
stack is short, there is an even greater chance that microbial
aerosols will fail to achieve sterilization temperatures before dis-
charge. The type of internal conveyors used, the design of
automatic vibrating grates, and even the lining of the furnace may
all be factors.
• The contamination of quenched residue by dust ever present in the
incinerator environment is also a possibility.
• Intermittent use of an incinerator results in lower operating temp-
eratures, as it takes time to raise the temperature of a cold
furnace.
The significance of stack height was investigated by Barbeito and Gremillion
(1968) in a study designed to examine the minimum temperatures required to pre-
vent release of dry and wet spores of Bacillus subtilis var. niger from the
stack exhaust of a municipal incinerator. They mixed dry spores with animal
bedding and dumped them in the firebox. The minimum temperatures required to
ensure destruction of the dry spores (concentration of 6 X 10 12 spores/ft3) were
371°C for firebox air and 196°C for firebrick refractory lining. Retention time
was 26.5 seconds. They found that retention time of the spores decreased with
increasing temperature, apparently due to increased velocity of expanding hot
air.
A liquid suspension of B. subtilis var. niger spores was disseminated into
the firebox as an aerosol. At a concentration of 5.3 X 109 spores/ft3 air and
retention time of 41 seconds, minimum temperatures to ensure destruction were
302°C for firebox air and 196°C for refractory lining (A^C^SiC^). Barbeito and
Gremillion also showed that the concentration of spores recovered per cubic feet
of air sampled decreased by one log as the spores recovered per cubic feet of
air sampled decreased by one log as the spores passed through the temperature
gradients in the last 59 feet of stack height.
25
-------
Peterson (1971), in a progress report on studies of microbiological survival
of the incineration process, collected data from eight incinerators including
the four previously described in Table 10. The incinerators were located in
Cincinnati, Chicago, Memphis, Atlanta and New Orleans.
A primary objective of this study was to develop and perfect sampling tech-
niques. The heterogeneous nature of MSW, and daily variations in its composi-
tion, have made the task of sampling for indicator organisms an unreliable
procedure. It was postulated that the number of enteric bacteria in a given
sample of waste or residue followed a Poisson probability distribution. Hence,
it was calculated that three 30 g subsamples (in duplicate) were required for
each raw refuse pile and each incinerator residue examined to give a 95% pro-
bability of positive sampling for enteric bacteria.
Before incineration, random samples of refuse were collected with sterile
tongs and placed in sterile 200 ml specimen cups. These samples were combined
into one 2,000 to 4,000 g sample, mixed, and a final 200 g sub-sample was
assayed for total viable bacterial cells, total coliforms, fecal coliforms, and
heat-resistant spores. Samples of quench water were similarly sampled and
assayed (see Section 5).
Air samples were taken by an Anderson sampler. Stack effluents were col-
lected after at least two hours of continuous normal operation using an impinge-
ment method adapted to the incinerator design. The effluent passed through a
water-cooled sterile stainless steel tube drawn by a 1.0 ft3/minute vacuum pump
(15 in. mercury). The effluent was collected in a 30 ml aliquot of sterile
0.067 M, (pH 7.2) phosphate buffer in a liter bottle. A 10 ft3 sample was
collected in a 10 minute run. Total viable bacterial count in the eight raw
refuse samples prior to incineration ranged from 4.0 x 10 to 6.8 x l(r
counts/g; total coliform densities were from 3.4 x 10^ to 5.1 x 107 counts/g,
with fecal coliform count of 1.5 x 104 to 8.1 x 105 counts/g. The high fecal
coliform density was interpreted as indicating fecal contamination of the waste.
None of the incinerator residues were sterile, though there were significant
differences in the microbial quality of each residue. As found in previous
studies (Peterson and Stutzenberger, 1969; Peterson and Klee, 1971), overall
performance of incinerator # 1 (continuous feed, traveling grate) was poorest,
with total viable cells (9.0 x 107 counts/g), heat-resistant spores (1.9 x 105
counts/g), total coliform count (1.2 x 105 counts/g), and fecal coliforms
(4.7 x 103 counts/g). Fecal coliform densities were less than 10 counts/g of
residue for both incinerator # IV and # V. Low total viable cells, spores and
coliforms were also obtained from incinerators # VI, # VII, and # VIII (see
Table 12).
Quench water from incinerator # VI contained less than 1 x 102 counts/ml of
total coliforms and 1 x 102 counts/ml of fecal coliforms. The total coliform
concentration in quench water from incinerator VIII was the same as for incin-
erator VI. Fecal coliform concentration for quench water from incinerator VII
was less than 1 x 10 counts/ml.
Quench water from incinerator # VIII contained total and fecal coliform
counts of 2.9 x 104 and 1.7 x 104 counts/100 ml respectively. Stack emissions
26
-------
Incinerator Number
Design of
Samples
Tested
TABLE 12
EFFICACIES OF VARIOUS INCINERATOR DESIGNS IN THE DESTRUCTION OF
MICROFLORA ASSOCIATED WITH MUNICIPAL SOLID WASTES
(Data expressed in arithmetic averages)
(Peterson, 1971)
Total Bacterial Count
Solid Waste
Residue
Quench Waters
Total Heat Total Fecal Total Heat Total Fecal Total Heat- Total Fecal
Viable Resistant Coli- Coli- Viable Resistant Coli- Coli- Viable Resist- Coli- Coli-,
Cells"'' Spores forms^f forms'^ Cellst Spores forms^ forms^ Cells § ant fortnsT forms!
Spores
-J
Continuous
feed, travel-
ing grate 4
II
Batch feed,
circulating
grate 3
III
Continuous
feed, rotary
kiln 6
IV
Batch feed,
reciprocating
grate 3
V
Continuous
feed, conical
burner 4
l.lxlO8 2.7xl05 3.0xl06 2.6xl05 9.0xl07 1.9xl05 1.2xl05 4.7xl03 —
4.5x108 l.lxlO5 6.7xl06 S.lxlO5 l.lxlO7 2.9xl04 2.8xl02
7.8xl07 3.8xl04 1.6xl06 1.2xl06 2.3xl06 9.7xl03 1.2xl02 2.0X101 —
4.8xl08 3.1xl04 l.lxlO6 6.3xl05 1.3xl04 5.6xl03 < 4 <
6.8xl08 1.9xl06 5-lxlO7 S.lxlO6 1.3xl06 l.lxlO5 2.GxlO1 3.8x10
-------
TABLE 12 (continued)
Incinerator Number
Design of
Samples Total
Tested Viable
Cellst
Total Bacterial Count
Solid Waste
Heat-
Resistant
Spores
Total
Coli-
formsf
Fecal
Coli-
formsf
Total
Viable
Cellst
Residue
Heat-
Basistant
Spores
Total
Coli-
formsf
Fecal
Coli-
formsf
Quench Waters
Total
Viable
Cells?
Heat
Resist-
ant
Spores
Total
Coli-
formsf
Fecal
Coli-
forms T
00
VI
Continuous
feed, rotary
kiln 2
VII
Continuous
feed, rotary
kiln 2
VIII
Continuous
feed, recipro-
cating grate 3
5.4xl07 3.5xl04 1.3xl07 5.6xl06 S.SxlO1 6-OxlO1 a.OxlO2 <1.0xl02 l.OxlO3 2.0xl02 <1.0xlo2 l.Oxlt?
4.0x106 2.5x104 3.4xl03 l.SxlO4 2.7x103 l.OxlQl
-------
were sampled for incinerator # V only. While most microorganisms were removed
by scrubbing, a few gram-positive bacilli (2 counts/ft3 air) escaped.
This study again demonstrates that the design and operation of a given
incinerator is an important factor in destruction of pathogenic organisms which
may be present in the solid waste charge. Of the incinerators evaluated, the
performance of incinerator # IV (batch feed reciprocating grate) was superior in
reduction of total and fecal coliforms. Incinerator # IV also showed a four log
order decrease in total viable cells. Incinerator # VI (continuous feed, rotary
kiln) showed a six log order reduction in total viable cells as did incinerator
# VIII (continuous feed, reciprocating grate). Figures 2, 3, 4, and 5 illus-
trate this difference in performance for the incinerators evaluated by Peterson
and Stutzenberger (1969), Peterson (1971), and Spino (1971).
Spino (1971) compared the efficiency of pathogen destruction of the New
Orleans East incinerator with the other seven described above. The New Orleans
East incinerator averaged a six log reduction of total bacterial count in the
residue (3.8 x 108 to 2.1 x 102 counts/g). The most efficient furnace in the
Cincinnati - Chicago studies averaged a 37 thousand-fold reduction (4.8 x 108 to
1.3 x 104 counts/g) while the other three furnaces averaged a 1 to 40 fold
reduction (6.6 x 108 to 2.4 x 104 counts/g). The Memphis incinerator gave a 27
thousand fold reduction (6.6 x 108 to 2.4 x 104 counts/g). No coliforms were
detected in the New Orleans East residue, but they were recovered in residues
from the other seven facilities. There was an average of 100 thousand-fold
reduction of aerobic spores for the New Orleans East incinerator compared to 10
thousand and one thousand fold from the Cincinnati - Chicago and Memphis studies
respectively. Salmonella give and Salmonella St. Paul detected in New Orleans
East refuse were not found in the incinerator residue.
Air Quality - the Incinerator and the Refuse Processing Plant
A major concern for all operations involved in the handling and processing
of solid waste is the quantity of dust generated. A number of studies have
shown that various microorganisms, some pathogenic, are associated with this
dust (Peterson, 1971; Armstrong and Peterson, 1972; Glysson et. al., 1974; Fiscus
et aU, 1977; Duckett, 1978).
Airborne bacteria are carried by dust and by water droplet nuclei. Dust
particles carrying bacteria may settle fairly rapidly, but any activity may re-
suspend the particles in the working environment. As Glysson et al^., have
pointed out, the bacteria transported by dust are probably too large for any
lung penetration (10/u), and, hence, the dustborne bacteria may present less of
a respiratory hazard than the smaller water droplet carried bacteria. Bacteria
transported by water droplets may remain air-suspended for some time and are
small enough (0.5 to 5/u) to penetrate lung tissue. Larger bacteria would be
trapped in nasal mucosa, and would eventually find their way into the gastro-
intestinal tract.
Glysson et al. studied the air quality of two incinerators and a transfer
station. Air~quality was evaluated using an Andersen air sampler to separate
air particles automatically into six aerodynamic sizes. Samples were collected
five feet from the floor and at important activity centers within the plant.
Colonies were developed for 24 hours at 37°C on trypticase soy agar (TSA). As
29
-------
9 .
U)
O
g
rd en
-P CQ
-H
8
5-1
O
rH
p -p
B tC
M-l -P
O d
6 .
5 _
1 .
II II
III III
IV
IV
V
VI
Figure 2. A comparison of the efficiency of total bacteria removal of incinerators
(Peterson and Stutzenberger, 1969; Peterson, 1971, Spino, 1971)
I Continuous feed, traveling grate
II Batch feed, circular grate
III Continuous, rotary kiln
IV Batch, reciprocating
V Continuous, conical
VI Continuous, reciprocating
Total column
is bacterial
concentration
in MSW
Bacterial cone.
in residue
incinerators
-------
s
en
-------
U)
NJ
.8
u w
O CJ
o 3
68
o q
IH -H
Total column is
total coliforms
in MSW charge
Total coliforms
in residue
II
III III
IV IV
V
VI
Figure 4. A comparison of the efficiency of total coliform removal of incinerators
(Peterson and Stutzenberger, 1969; Peterson, 1971; Spino, 1971)
I Continuous feed, traveling grate
II Batch feed, circular grate
III Continuous, rotary kiln
IV Batch, reciprocating
V Continuous, conical
VI Continuous, reciprocating
-------
CO
!
88
M-l
•H
*
M-l
O
£<
•H
-P
Total column is
fecal coliforms
in MSW charge
Fecal coliforms
in residue
IV IV
Figure 5. A comparison of the efficiency of fecal coliform removal of incinerators
(Peterson and Stutzenberger, 1969; Peterson, 1971; Spino, 1971)
I Continuous feed, traveling rate
II Batch feed, circular grate
III Continuous, rotary kiln
IV Batch, reciprocating
V No data given for incinerator
VI Continuous, reciprocating
-------
expected, for all facilities the bacterial content of the air was very dependent
on activity within the plant.
For the smallest incinerator (125 tons/day, TPD), highest bacterial levels
were recorded after washing the charging floor of the incinerator
(334 counts/ft3). Refuse was discharged directly onto the concrete floor from
packer trucks, and pushed into the charging hopper of the furnace (end-charged,
batch-fed) by a rubber-tired front-end loader. Emptying of the trucks was
associated with high bacterial levels (183, 141.2, 172.3, 207.2 counts/ft3), as
was charging of the hopper (240.8 and 117.5 counts/ft3). Lowest values were
recorded for periods of little or no activity (14.5, 23.8 counts/ft3 ). Changes
in manner of operation resulted in significant drops of bacterial levels. For
instance, when the trucks were emptied onto a previously wetted floor, levels
were only 32.6 counts/ft3. Dumping and moving bagged refuse gave an average air
quality of 52.1 counts/ft3.
A variety of colonies were counted without any attempt being made to dif-
ferentiate between organisms. Most colonies developed on the first stages of
the sampler, though the presence of smaller bacteria (i.e., those likely to
present respiratory tract hazard) was also confirmed by viable counts on stage
five and six plates (25% particles in hazard size range).
The presence of staphylococcus colonies was suspected for stages 2, 3, and
4, and confirmed by culturing 33 suspected colonies and testing for mannitol
fermentation using standard M-staphylococcus broth. Sixteen (16) colonies were
mannitol positive, and on microscope examination were seen to be gram positive
staphylococc i.
In a later study of air quality at the Southeast Oakland incinerator (600
TPD) and at a large refuse transfer station, Glysson e_t al. identified alpha and
beta hemolytes and E. coli in dust samples. Sampling methods were similar to
the previous study. Total colonies were developed on TSA with 5% defibrinated
sheep blood (see Section 5) for 24 hours at 37°C. E. coli was developed on
eosin methylene blue (EMB) agar for 24 hours at 37°C.
Again, significant densities of total bacteria were associated with tipping
and removal of unbagged refuse. A total bacterial count of 1,950 counts/ft^ was
recorded on the receiving/dumping floor as the truck was emptying refuse.
Levels of 800 and 670 counts/ft3 were recorded near the ashhopper-residue
discharge area and the charging floor, respectively. Values for the transfer
station were similarly high when trucks were emptied of trash. A value of 2210
counts/ft3 was recorded at the far end of the storage pit during trash dumping.
Despite the high total bacterial levels recorded by Glysson e_t al., at both
the incinerator and the transfer station E. coli values were surprisingly low
(see also Peterson, 1971) with a maximum value recorded of 3 counts/ft3. This
may be explained by the inability of E. coli to survive for long when in the dry
state.
In Peterson's study (1971), dust samples were taken from the waste dumping
areas, the charging floors and the residue areas of six of the incinerators pre-
viously described. Data are summarized in Table 13. Incinerator # VI which
34
-------
TABLE 13
CHARACTERIZATION OF GRAM - POSITIVE COCCI AND
GRAM - NEGATIVE BACILLI ISOLATED FROM 0.25 CU FT3 AIR
(Peterson, 1971)
Sampling
area
Dumping
floor
Incinera-
tor:
I
II
III
IV
V
VI
Charging
floor
Incinera-
tor:
I
II
III
IV
V
VI
Residue
area
Incinera-
tor:
I
II
III
IV
V
VI
Total
27
34
45
43
6
2
55
43
7
34
4
1
48
22
7
6
0
0
Gram
jitaphylococcus
aureus
2
1
2
0
0
1
1
1
0
1
0
0
0
0
4
0
0
0
- positive cocci
Staphylococcus
epidermis
19
18
25
23
0
0
44
13
4
17
0
0
34
7
0
3
0
0
Diplocooccus
pneumoniae
0
1
1
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
a-hemolytic
streptococci
6
14
17
20
6
1
9
29
3
16
4
1
14
15
3
3
0
0
35
-------
TABLE 13 (continued)
Sampling
area
Dumping
floor
Incinera-
tor:
I
II
III
IV
V
VI
Charging
floor
Incinera-
tor:
I
II
III
IV
V
VI
Residue
area
Incinera-
tor:
I
II
III
IV
V
VI
Gram
Aerobacter
Total
82
66
28
40
100
0
31
28
22
24
17
4
25
3
11
1
7
0
species
29
26
8
26
0
0
12
10
1
13
0
2
15
0
0
1
4
0
- negative bacilli
Escherichia Klebsiella
coli
2
6
2
4
0
0
2
1
1
0
0
2
1
0
1
0
0
0
pneumoniae
1
2
0
1
0
0
0
0
0
2
0
0
0
0
0
0
0
0
Others*
50
32
18
9
100
0
17
17
20
9
17
0
9
3
10
0
3
0
*Proteus, Pseudomonas, Alcaligenes
36
-------
showed the lowest level of microbial cells was newer and more hygienically man-
aged than the other incinerators sampled. Staphylococcus aureus, Diplococcus
pneumoniae (both pathogenic organisms associated with skin and upper respiratory
tract ailments) were found in small quantities in the incinerator dust. Large
quantities of Staphylococcus epidermis were detected in dust from the dumping
and charging room floors of four of the incinerators, and in dust from the
residue area of three of the incinerators. Alpha-hemolytic streptococci were
detected in dust samples from all of the incinerators especially in samples col-
lected from the dumping and charging room floors. Small amounts of E. coli were
found in the dust of five incinerators, indicating fecal contamination of the
wastes. Such contamination is obviously one way in which pathogenic organisms
may be transmitted to man and the environment.
The microbiological content of dusts at a pilot resource recovery plant in
Washington, D.C., was examined by Duckett (1978). The plant can process 10 to
15 tons/hour of MSW, and includes front-end recovery of glass, aluminum, and
ferrous metal. Three samples were collected during operating and nonoperating
periods in-plant at each of three locations: (i) near the primary shredder;
(ii) near the aluminum eddy current separator; and, (iii) in the densified
refuse-derived fuel (RDF) room. These sites were considered very likely to have
high levels of microbial aerosols, and were each chosen to represent a "worst
possible" situation. A total of 18 samples were collected using an Andersen
2000 Impactor Preseparator connected with a Sierra Instruments 216 Ambient
Cascade Impactor.
Some samples were assayed immediately after collection, while others were
stored over night. Samples were prepared by washing off each filter with 0.1%
of peptone dilution water containing 0.1% Triton X-100. Subsequent serial dilu-
tions were prepared from the original solution using the same general dilution
medium. Samples were assayed for total aerobes, total and fecal coliforms, and
fecal streptococci using the standard methods described by the American Public
Health Association (APHA, 1971) (see also Section 5).
Large numbers of viable cells were found on all plates. Levels of non-
respirable aerobic organisms were often so high that only "greater than"
estimates could be made. These estimates ranged from <1,400 x 103 counts per m3
air to >8,500 x 103 counts/m3 air. Highest levels were found in the RDF room
during activity periods.
The combined respirable fraction was also highest in the RDF room during
operation, when the level peaked at >7,000 x 103 counts/m3 air (other values -
490 x 103 and 630 x 103 counts/m3). A maximum level of 2,300 x 103 counts/m3
air for combined respirable size fractions was found near the primary shredder
during operation. The highest level of respirable bacteria at site (b) was much
lower (200 x 103 counts/m8 air).
Coliforms were either absent or present in much smaller concentrations.
Fecal coliforms were found in six samples, with the highest level recorded
during activity in the RDF room (>39 x 103 counts/m3 air). Highest total coli-
form count was in the same sample (>40 x 103 counts/m3 air). More than 90% of
the fecal coliforms collected were in the nonrespirable fraction of the dusts.
37
-------
Levels of fecal streptococci tended to be higher than levels of fecal
coliforms. Fecal streptococci were isolated from 15 of the 18 samples. Again
highest levels were found in the RDF room during operation (> 45 x 103 counts/m3,
>110 x 103 counts/m3). Overall average values for all organisms were found in
Table 14. Table 15 gives overall average values for other worksites to permit
comparison.
The fungus, Aspergillus fumigatus, was detected in three samples (four
plates), and Staphylococcus aureus in seven samples (11 plates) (Duckett, 1978).
Both organisms were found in respirable and non-respirable size fractions. No
Salmonella or Shigella were isolated. Klebsiella pneumoniae was found in one
respirable size sample collected from the RDF room. Citrobacter, Enterobacter,
and Arizona were found in occasional samples. The types of organism found and
the ratio of fecal coliforms to fecal streptococci are indicative of fecal con-
tamination of the wastes by animals other than humans.
Duckett stressed that various sources of error make these results approxi-
mate rather than absolute. Some of these sources of error are applicable to
other studies discussed. Possible sources of error mentioned by Duckett were:
• Preferential suppression of pathogens by non-pathogenic organisms
because of the higher survival and growth rates of the latter;
• Deterioration of samples stored overnight resulting in lower rates
of recovery;
• Use of dilution and growth media of a non-specific nature (i.e.,
media for bacterial growth not necessarily the preferred media for
each organism detected);
• Incomplete dispersion of clumped cells;
• Incomplete elution of cells from dust particles;
• The presence of microbial growth inhibitors.
As can be seen from Tables 14 and 15, concentrations of total aerobes for
both operating and non-operating modes are much higher than ambient values. The
level of total aerobes during operation is very much higher than the given
values for factories, incinerators, a sewage treatment plant, a resource
recovery plant, and spray irrigation. These very high average values are, how-
ever, of the same log order as the highest inplant value reported by Fiscus et
a!U (1977) in their study of the microbiological quality of air in the St. Louis
RDF plant. The average value for all inplant locations at the RDF plant was a
log order lower.
Fiscus et al. conducted an assessment of the relative bacteria and virus
emissions at the St. Louis Refuse Processing Plant and other waste handling
facilities. The St. Louis plant was operational from 1972 to 1976 treating
272 Mg/day of solid waste to produce RDF. The other facilities tested were a
municipal incinerator, a wastewater treatment plant, a refuse transfer station,
and a sanitary landfill. Testing was also undertaken in downtown St. Louis, and
for a refuse collection packer truck.
38
-------
TABLE 14
AVERAGE VALUES OF SELECTED MICROORGANISMS PRESENT IN
MICROBIOLOGICAL AEROSOLS AT AN RDF PLANT
(Duckett, 1978)
Mode of Opera-
tion
Nonoperating
Operating
Size of Average overall concentration (counts/np)
Bacteria
All
Respirable §
Nonrespirable #
All
Respirable §
Nonrespirable #
TA*
10,240
5,370
4,875
4.5 x 10 6
1.9 x 106
2.6 x 106
FST
141
36
106
3.1 x 104
9,925
21,370
FC +
36
0
36
8,620
1,340
7,280
* TA - Total aerobes, measured by Most Probable Number (MPN) method
t FS - Fecal streptococci, measured by MPN method
f FC - Fecal coliforms, measured by MPN method
§ Respirable - <10 /urn
# Nonrespirable - 10 to 80 /urn
TABLE 15
REPORTED AEROSOL CONCENTRATIONS OF BACTERIA FOUND IN AMBIENT
AIR AND VARIOUS WORKING LOCATIONS*
Environment
Concentrat ion (counts/m 3)
Total Fecal Fecal
aerobes streptococci coliforms
Reference
Urban air 495
Urban air
Country air
Schools/offices
Factories
Incineration 1,410
- 6,005
2,540
1,980
3,360
3,990
-27,830
Hers & Winkler,
Winslow, 1926
Winslow, 1926
Winslow, 1926
Peterson &
Stutzenberger,
1973
1969
Resource re-
covery plant 4,730 -12,720
Sewage treat-
ment plant 320 -42,390
Spray irri-
gation 106 -10,600
13,990-19,075 140-2,440 Diaz et al., 1976
Rickey & Reist, 1975
Bausum et al., 1976
* See also the work of Fiscus et al., 1977.
39
-------
The purposes of the study were several:
« To provide comparative data on airborne bacterial and viral levels
for the facilities selected;
© To identify any correlation between bacterial concentration and
particulate size;
« To evaluate the efficiency of particulate and microorganism removal
by a pilot scale mobile filter unit provided by EPA; and,
• To determine the efficiency of removal of microorganisms, trace
metals and asbestos from the RDF environment by the air classifier-
system.
Testing was conducted over a three or four day period for each facility,
partly because of cost considerations. Samples were collected using Hi-Vol
ambient air filters and Andersen agar plate impactors stationed at in-plant and
property line locations. Additionally, at the RDF plant, emissions from the air
classifier system were evaluated for microorganisms, trace metals and asbestos,
Samples were assayed according to the standard methods described in Section
5 (q.v.). As all virus assays were negative for reasons not determined, no com-
parisons were possible for viral counts. Though assays were made for Salmonella
sp. , Staphylococcus aureus, and Klebsiella sp. , results were generally negative,
indicating that either these species were present in very low concentrations, or
if present, were not viable.
Hi-Vol results for bacteria present are given below by rank order (see Table
16) . The range of bacterial levels for both in-plant and ambient locations is
shown in Tables 17 and 18. These tables give maximum and minimum values for
each facility, but do not distinguish between different sampling points in the
same facility. Average values for individual sampling points are shown in
Figure 6 for total bacteria, Figure 7 for total calif orms, Figure 8 for fecal
coliforms, and Figure 9 for fecal streptococci.
For in-plant samples, the total bacterial count was highest at the RDF plant
(1.68 x 10 6 counts/m 3 in the control room), and lowest at the landfill (95.6
counts/m3 air for working face East) (see Table 17). Total and fecal coliforms
were highest in the packer truck (352 counts/m3 for both), while fecal strepto-
cocci levels were greatest at the waste transfer station (6,340 counts/m3 air at
the truck ramp).
range of in-plant and ambient values for each facility was large, making
it difficult to interpret results. The range of airborne bacterial levels was
greatest downwind of the RDF plant, Since this plant was located upwind and
immediately adjacent to the incinerator, and the property-line sampling points
for both facilities were identical, it does not seem realistic to separate
ambient values for one plant from another.
Total bacterial colonies as measured by the Andersen agar plate samples
followed a similar pattern to the Hi-Vol assays , though the results are not
40
-------
TABLE 16
RANKING* OF HI-VOL SAMPLES BASED ON AVERAGE BACTERIAL LEVELS
(Fiscus et al., 1977)
Total bacteria Total coliform
Fecal coliform Fecal streptococci
(a) In-plant
RDF plant
Packer truck
Incinerator
Waste transfer
WWTP
Landfill
Packer truck
RDF plant
Waste transfer
Incinerator
Landfill
WWTP1"
Packer truck
RDF plant
Waste transfer
Incinerator
Landfill
WWTP
Waste transfer
Packer truck
RDF plant
Incinerator
Landfill
WWTP
(b) Ambient
Upwind and downtown
RDF plant
Incinerator
Downtown
Waste transfer
WWTP
Landfill
RDF plant
Downtown
Incinerator
WWTP
Waste transfer
Landfill
RDF plant
Downtown
Waste transfer
Incinerators
WWTP
Landfill
RDF plant
Incinerator
Waste transfer
Downtown
WWTP
Landfill
Downwind and downtown
RDF plant
Incinerator
Downtown
WWTP
Waste transfer
Landfill
RDF plant
Waste transfer
Incinerator
Landfill
Downtown
WWTP
RDF plant
Waste transfer
Incinerator
WWTP
Downtown
Landfill
RDF plant
Incinerator
Waste transfer
Downtown
WWTP
Landfill
* In descending order
t WWTP - Wastewater treatment plant
41
-------
TABLE 17
HI-VOL IN-PLANT BACTERIA COUNT/CUBIC METER: HIGH AND LOW VALUES (MPN)*
(Fiscus et al., 1977)
Total Bacteria
Location
Packer truck
RDF plant
Waste transfer
station
Incinerator
Wastewater
treatment
Sanitary
Low
13,500
3,820
2,870
15,300
<473
<95.6
High
114,000
1,630,000
30,550
239,000
174,000
2,480
Total Col i form
Low
3.76
0.755
2.07
<0.017
<0.020
<0.020
High
>352
>213
153
18.6
0.755
16.3
Fecal Col i form
Low
1.24
0.755
0.143
<0.017
<0.020
<0.020
High
>352
30.4
10.3
4.86
<0.061
16.3
Fecal Streptococci
Low
235
10.5
14.3
2.13
<0.946
<0.956
High
411
478
6.340
411
<1.79
6.70
Most probable number method, see Section 5.
-------
TABLE 18
HI-VOL AMBIENT BACTERIA COUNT/CUBIC METER: HIGH AMD LCW VALUES (MPN)*
(Fiscus et al., 1977)
Total Bacteria
Location
Incinerator
Upwind
Downwind
RDF Plant
Upwind
Downwind
Waste transfer
station
Upwind
Downwind
Wastewater
treatment
Upwind
Downwind
Sanitary
landfill
Upwind
Downwind
Down town
1
2
Low
470
1,900
2,830
949
< 477
< 469
< 477
< 477
239
< 95.2
<497
712
High
6,045
12,400
14,400
78,800
2,910
3,820
2,700
5,720
944
1,430
1,820
4,780
Total Col i form
Low
0.061
0.038
0.312
0.104
< 0.020
< 0.020
< 0.020
< 0.020
< 0.020
< 0.020
0.199
0.029
High
0.225
5.16
2.33
51.2
0.224
22.9
0.447
1.05
0.211
3.16
0.655
0.59
Fecal Col i form
Low
< 0.019
< 0.020
< 0.020
< 0.020
<0.020
< 0.018
< 0.020
< 0.020
< 0.020
< 0.020
< 0.020
< 0.019
High
-------
id
•H
I
•d
5
6j
5
4 -
3 .
2
1
0
tit
as
Truck
04
Bf
!
I A
Incinerator
en
en
I A
PDF plant
I A
Landfill
I A I A
Waste transfer Wastewater plant
I - In-plant, A - Ambient
Figure 6. Air quality of various waste treatment facilities - total bacteria, average valuss
(Fiscus et al., 1977)
-------
Ln
8
1
1
0
10
10
-2
10
1
-p -p
ll } I
o p
trH rH
*w m
ill!
JH -H -H a,
EH H EH !J
Truck
I A I A
RDF plant Landfill
I - In-plant, A - Antoient
I A
Incinerator
I A I A
Waste transfer Wastewater plant
Figure 7. Air quality of various waste treatirent facilities - total coliforms, average values
(Fiscus et al., 1977)
-------
102
CTl
8 10
0
•H
H
8
u
fi
10'
,-1
10
-2
::•
m
m<
Bft'-
I A I A I A
Truck Incinerator RDF plant Landfill
I - In-plant, A - Anbient
I A I A
Waste transfer Wastewater plant
Figure 8. Air quality of various waste treatment facilities- fecal colifonns, average values
(Fiscus et al./ 1977)
-------
--J
10"2
A
I A
RDF plant
Truck Incinerator
I - In-plant, A - Anbient
I A
Landfill
I A
Waste transfer
I A
Wastewater plant
Figure 9. Air quality of various waste treatment facilities - fecal streptococci, average values
(Fiscus et al.f 1977)
-------
directly comparable because of differences in the nature and methodology of the
sampling. One obvious difference between the two. was the very high values of
total bacteria found in the pressroom of the sewage treatment plant during dump-
ing of the filter cake (1.55 x 105 counts/m3). The Hi-Vol samples were taken
over a longer period of time (six hours), and hence the effect of this activity
is not seen for the Hi-Vol samples.
Because the results were difficult to interpret, a statistical analysis of
the data was undertaken. Analysis of variance procedures showed that RDF plant
concentrations were either significantly higher (95% confidence level) than the
other locations, or there was no statistically significant difference. The RDF
plant values were never significantly lower than the other facilities. Ambient
fecal streptococci values were significantly higher at the RDF plant than the
other locations, but in-plant samples were not significantly different. Since
only a few replicate samples were collected, and the range of values was so high
for each site, a greater number of samples might present a very different set of
statistical conclusions.
Some of the Hi-Vol and the Andersen samples were examined microscopically.
Gram-positive and gram-negative rods predominated with some gram-negative cocci
and actinomycetes.
Particulate tests on the air classifier system at the RDF plant showed un-
controlled particulate emissions of 14.2 to 17.8 kg/hr. Total bacteria in the
emissions averaged 5.3 x 107 counts/g (approximately the same concentration as
found in raw, shredded refuse). The pilot scale mobile filter, taking a side-
stream drawoff of the air classifier emissions, removed 99.95% of the particu-
late mass, 99.6% of total bacteria, and at least 99.9% of total coliforms. It
seems clear that a filter system on the air classifier discharge should be very
efficient at removing particulate matter and the associated bacteria.
Andersen samples do not give an indication of the number of bacteria carried
by a particle (which may vary), but do indicate the number of particles carrying
bacteria. The results of the Andersen samples showed that the smaller sized
bacteria, as transported by suspended particulate matter, represented a signifi-
cant percentage of the total bacterial count for all facilities tested.
As previously mentioned, the smaller sized bacteria present a greater
respiratory hazard than the larger bacteria, which are more likely ^to enter the
gastrointestinal tract via the upper respiratory system. The health implica-
tions of high dust levels in solid waste processing plants are, however,
unclear. One epidemiological study reported an increase in chronic bronchitis
among sanitation workers, but did not control for smoking habits (Ducel et al.,
1976). An earlier study showed that cardiovascular disease, arthritis, and skin
complaints were some of the occupational hazards of New York City refuse col-
lectors (Sliepcevich, 1955). Cimino (1975) was unable to show that respiratory
diseases, skin infections, or asthma were significantly more prevalent among New
York sanitation workers than other working groups, but did confirm the high rate
of cardiovascular disease.
Summary
It is clear from the studies completed to date that various bacteria may
48
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survive incineration. Possible reasons for this survival in spite of high tem-
peratures achieved within the furnace have been reviewed. The degree to which
both heat-tolerant and heat-susceptible organisms do survive incineration varies
greatly, depending on the design and operation of each furnace. The detection
of Salmonella sp. and their survival in residue after incineration is indicative
of the potential health hazard associated with incomplete sterilization of solid
wastes. The presence of fecal coliforms in waste, residue, and quench water is
indicative of fecal contamination of MSW; and spread of pathogenic organisms
from feces is obviously a possibility where sterilization is incomplete.
As shown in these studies, dust and associated bacteria levels are very high
within the incinerator and RDF plant environment if proper dust control measures
are not taken. Total bacteria levels at an RDF plant during activity are
especially high, and may exceed a million counts/m3 air if uncontrolled. It is
clear that certain precautions should be taken when working in such a dust-laden
environment. Various dust control systems have been evaluated for the Environ-
mental Protection Agency- The St. Louis study has already been mentioned. To
recapitulate, the attachment of a baghouse to a side stream drawoff of the air
classifier system removed 99.95% of the particulate mass, 99.6% of total
bacteria, and at least 99.9% of total coliforms. This same device was tested at
an RDF plant in Houston, Texas. Dust and associated bacteria removal
efficiences were up to 99.6% (Freeman, 1978).
In addition to installation of a properly designed dust control system, all
activities which tend to aerate or agitate the refuse should be kept to a
minimum and where possible circumvented. For example, use of a conveyer to
carry refuse through the plant would reduce dust levels. Bagging of refuse is
also a useful procedure. Glysson et al. (1974) recommended the use of dust
masks by personnel during high activity periods, and also suggested that some
form of wet-vacuuming would help control dust generation. The introduction of
handling procedures that reduce human exposure to the dust should obviously be
encouraged as a precautionary measure for all facilities processing solid waste.
III. SANITARY LANDFILL
The Process
Land disposal is the final method of disposing of solid wastes whether or
not they have been previously treated. This is because other methods of waste
treatment (incineration, composting, anaerobic digestion, etc.) reduce weight
and volume of the waste, but still leave a residue. Sanitary landfill is an
environmentally acceptable way of land-disposing of solid wastes. The selection
of a site for the fill is critical, and should include the following
considerations:
• hydrogeological survey of the area to determine the potential for
vertical and horizontal leaching from the fill,
• access roads to the area,
• availability of cover materials; and,
• grades for proper drainage.
49
-------
There are several appropriate methods of operating a fill depending on the
topography of the area and the climate. Where the water table is low, trenches
are dug and layers of rubbish and excavated earth are alternated in the fill.
For unprocessed municipal waste, the rubbish is covered with soil daily (6 in.
layer). For shredded waste or residues from previous treatments (incineration,
digestion, etc.), it is not necessary to cover with soil daily.
Where the water table is high, refuse is layered above the ground to heights
of 50 to 60 feet, when a final two-foot layer of soil covers the mound. When
the terrain is uneven, a ramp or slope method is used. Rubbish is layered on
the slope and covered with soil lying above the fill.
The rate and degree of bacterial activity within the fill depends on the
following factors (Engelbrecht and Amirhor, 1975):
• the moisture content of the fill,
• the temperature,
• the composition and properties of the waste material,
• microorganisms present in the waste or soil cover, and
• overall environment of the fill including oxygen availability.
The moisture content of MSW is usually in the range of 20 to 35%. The
moisture content of the fill may be increased by rainfall, runoff from the sur-
rounding area, or seepage into the fill. At 40 to 60% moisture, microorganisms
within the fill are very active.
Though initially aerobic conditions and, hence, aerobic bacteria prevail in
the fill, after a few days the limited oxygen supply -is exhausted, and
facultative and anaerobic microorganisms predominate. The initial exothermic,
aerobic bioreaction may result in a temperature high of around 60°C (Farguhar
and Rovers, 1973) though the temperature high is also dependent upon the initial
temperature of the fill material. Subsequent chemical and biological reactions
are primarily endothermic.
Temperatures within the fill slowly decrease from the initial peak value,
and within the fill essentially anaerobic conditions prevail. Biological action
by mesophilic organisms decomposes the organic matter to produce methane gas,
water, and the biodegraded residue. The activity is analogous to the anaerobic
digestion process suggested for methane recovery from wastes.
While sanitary landfill may be an environmentally acceptable means of solid
waste disposal, methods of operating fills are not always sound. Hazards
associated with improper landfill practices may be aesthetic (unsightly appear-
ance, blowing paper, etc.), obvious health dangers (accumulation, rats, insects,
birds), or involve spontaneous combustion of escaping gas.
50
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Survival of Pathogens
The degree of hazard presented by pathogenic organisms which may be present
in a landfill depends on three basic factors:
• the initial concentration and nature of contaminant in the waste;
• the extent of survival of pathogens within the fill; and,
• possible leaching of pathogens from the fill into the environment.
As already established, MSW and other solid wastes may be heavily contami-
nated by a variety of pathogenic microorganisms. Composted material destined
for landfill may contain pathogenic fungi and/or parasites (Gaby, 1975). Simi-
larly, the sludge from anaerobic digestion, especially the mesophilic
modification, may not be sterile. Given the initial contamination of the solid
waste to be landfilled, the survival of enteric organisms expected to be present
in waste (fecal coliforms, fecal streptococci, Salmonella sp. enteroviruses)
must be examined in the environment of the fill, as well as possible leaching of
pathogens from the site.
Excess moisture in the fill may result in formation of a leachate containing
water soluble chemicals, biological species, and suspended particulate matter.
Leachate may seep from the fill at the surface, or percolate through the fill
and the surrounding soil. Where drainage pipes are installed, the leachate may
be collected and treated if required. The amount of leachate produced by a fill
depends principally on the composition of the solid waste, the hydrological con-
ditions and the nature and gradient of the soil cover (Engelbrecht and Amirhor
1975). Note that not all landfills generate leachate. The physical and
chemical characteristics of leachate vary widely (see Table 19). While the
chemical properties of the leachate influence its biological composition, it is
not possible with present knowledge to make a direct correlation between the two
sets of properties (Engelbrecht and Arnirhoir, 1975).
Various studies have indicated that there is a significant bacterial popu-
lation associated with leachate, but that this population decreases in density
with time of operation or time of leaching (Quasim and Burchinal, 1970; Blannon
and Peterson, 1974; Cooper et al., 1974a; Engelbrecht et cd., 1974; Engelbrecht
and Amirhor, 1975; Glotzbecker and Novello, 1975).
Blannon and Peterson (1974) studied the occurrence and survival of fecal
coliforms and fecal streptococci in leachates collected from an experimental
field-scale sanitary landfill over an 11 month period. The trench-fill sampled
was 140 feet long by 30 feet wide (see Figure 10). The fill contained 435 tons
(wet weight) of compacted solid waste (1,035 Ib/yd3). The bottom of the fill
was lined with a clay soil liner (18 in.). The first leachate was collected
approximately six weeks after placement. Additional samples were collected
weekly from two pipes lying one within and one below the clay liner. Tempera-
tures at the center of the fill peaked at 60°C after a week, and gradually
decreased to 10° to 16°C after 11 months. The edges of the fill were some 5° to
9°C lower than the center.
51
-------
140 ft
8% ft
Polyethene, 6 mil
Hypalon liner, 30 mil
Figure 10. Cross-section of an experimental sanitary landfill
(Blannon and Peterson, 1974)
-------
TABLE 19
RANGE OF CHEMICAL COMPOSITION OF SANITARY LANDFILL LEACHATE"
Constituent
COD
BOD 5
TOC
pH
TS
TDS
TSS
Specific Conductance
Alkalinity (CaCOa)
Hardness (CaCOs)
Total-P
Ortho-P
NH.^N
NO 3 + N02-N
Ca
Cl
Na
K
S04
Range of Valuest
40-89,520
81-33,360
256-28,000
3.7-8.5
0-59,200
584-44,900
10-700
2,810-16,800
0-20,850
0-22,800
0-130
6.5-85
0-1,106
0.2-10.29
50-7,200
4.7-2,467
0-7,700
28-3,770
1-1,558
(continued)
53
-------
TABLE 19 (continued)
Constituent Range of Valuest
Na 0.09-125
Mg 17-15,600
Fe 0-2,820
Zn 0-370
Cu 0-9.9
Cd < 0.03-17
Pb < 0.10-2.0
* All constituents ariTlsxpressedTh mg/1 except pH and specific conductance
(/u noh/cm).
1" Summary Report: Municipal Solid Waste Generated Gas and Leachates.
Internal Report, U.S. Environmental Protection Agency, National Environ-
mental Research Center, Cincinnati, Ohio, 1974. Cited in Engelbrecht and
Amirhor, 1975.
54
-------
Organisms were determined by the most probable number technique (MPN)
considered to be more accurate than the membrane filter method (MF). Smith
(1972) and Glotzbecker (1974) have compared the two methods and shown that
density of total and fecal coliforms in leachate may be 2 or 3 logs higher using
the MPN method. However, Engelbrecht et al_. (1974) have called for comparison
of the two techniques with a control system included in the experimental design,
and with different suspending media.
A total of 60 streptococcal strains were identified (see Table 20). Fecal
streptococci and fecal coliforms were detected in leachates from both pipes.
Organisms found in the upper pipe were believed to have leached from the cooler
edges of the fill. The large number of organisms found in the lower pipe
indicated that the clay soil liner was a poor filter. During the first two
month period, average fecal streptococci densities in samples from the upper and
lower pipes were 48 million and 460,000 organisms/100 ml respectively. In the
upper pipe, fecal streptococci densities exceeded 10,000 organisms/100 ml during
the final sampling period. Fecal streptococci densities averaged 2,900
organisms/100 ml from the lower tube after 11 months.
TABLE 20
OCCURENCE OF STREPTOCOCCI IN LEACHATE
(Blannon & Peterson, 1974)
Species
Strains
Sanitary Significance
S.Faecalis var. liquefaciens 58.33 35
atypical S. Faecalis var. 8.33 5
S. faecalis biotype II 15 9
S. faecalis biotype III 5 3
S. durans 5 3
S. equinus 8.33 5
none— wide spread in
environment
none— associated with
vegetation
Indicative of fecal contami-
nation of the waste by
warm-blooded animals
Initial fecal coliform densities averaged 1.5 million/100 ml (upper
tube) and 280,000 organisms/100 ml (lower tube). Fecal coliform densities
dropped fairly rapidly in leachates from both tubes. In the upper tube
values varied from 30 to 180 organisms/100 ml for the last six months of the
investigation. Fecal coliform densities in leachates from the lower tube
averaged 20 organisms/ml for the last 2 months of the survey (see Table 21).
55
-------
Blannon and Peterson found that the ratio of fecal coliforms to fecal
streptococci in the leachate ranged from 0.011 to 0.272 for four samples
collected during the initial five weeks of leaching. One sample was found
with a ratio of 6.202. Human waste would be expected to have a fecal
coliform to fecal streptococci ratio of 4 or more, while the ratio for
warm-blooded animals would be less than 0.6 (Geldreich and Kenner, 1969).
Since the ratio of fecal colifonus to fecal streptococci reported by Blannon
and Peterson is low, the leachate was most likely contaminated by animal
excreta rather than human feces.
TABLE 21
DISTRIBUTION OF FECAL COLIFORMS AND FECAL STREPTOCOCCI IN LEACHATES FROM
THE UPPER PIPE
(Blannon & Peterson, 1974)
Collection Date
8-31-71
9-1-71
9-13-71
9-20-71
9-27-71
Densities/lOOml
Fecal col i forms Fecal Streptococci
2.6 x 106
4.9 x 106
2 x 103
9 x 103
3.3 x 104
2.4 x 108
7.9 x 105
7.9 x 104
3.3 x 104
1.70x 105
Ratio
FC/FS
0.011
6.202
0.025
0.272
0.194
In a related study, Glotzbecker and Novello (1975) compared the survival
rates of poliovirus and bacterial indicators in the same experimental fill,
and in an operating municipal landfill. Over a 4 1/2 month period, fecal
coliform densities in the municipal landfill leachate dropped from 4.6 x 102
to 23 counts/100 ml (MPN). Fecal streptococcal levels dropped from 1.5 x 103
to 1.1 x HT counts/100 ml.
Survival studies were conducted using Escherichia coli ATCC 11229, Strep-
tococcus faecalis SEC and poliovirus 1 Mahoney (LP) EKP-42. Within three
hours at 10°C, there was a 99.9% reduction of E. coli in the experimental
landfill leachate. S. faecalis survived just over five hours. Survival
times were much higher for the municipal landfill. At 10°C, 99.9% reduction
of E. coli took 56 days, and for S. faecalis more than 100 days. At 20°C,
survival time of E. coli dropped to 21 days, and S. faecalis to 35 days. The
leachates collected were transported in sample bottles containing EDTA to
protect against inactivation of bacteria on transport from the fills to the
laboratory. Addition of EDTA to the cell culture improved recovery of
viruses (plaque method), a finding in agreement with other studies (Cooper et
al., 1974a; Sobsey et al., 1975).
Poliovirus survival was less variable for the two fills. On day 90 at a
temperature of 10°C, there was 8.9% viral recovery for the municipal landfill
56
-------
and 36% for the experimental trench. On day 90 at 20°C, recovery from the
municipal fill was 0.01% and 0.43% respectively. There was a much more rapid
decrease in viral concentrations at 20°C than at 10°C indicating the suscepti-
bility of the viruses to inactivation at the higher temperature.
Engelbrecht (1973) also found a decrease in bacterial population with
temperature. He showed that the inactivation of Salmonella typhimurium,
fecal streptococci, and polioviruses was more rapid at 55°C than at 22°C for
a simulated landfill (lysimeter).
It was also found that inactivation of both the bacteria and the viruses
was pH dependent. At pH 7.0 and 55°C, fecal streptococci were stable in
leachate for up to eight days, but were reduced in density by four logs
within 24 hours at pH 5.3. S. typhimurium was more stable at both pH values
than fecal coliforms, and more stable than the fecal streptococci at pH 5.3.
Since landfill leachates commonly have pH values between 5.0 and 5.5
because of formation of organic acids (Fungaroli and Steiner, 1971), these
results seem to suggest that the known pathogen, S. typhimurium, is more
stable in the landfill leachate than the indicator organism.However, as the
rate of die-away of the Salmonella was still high (four logs within eight
days at pH 5.3, 55°C), and its density should be lower than that of the indi-
cator organism, survival of S. typhimurium seems unlikely in the environment
of the fill.
The rate of virus inactivation was also greater at the lower pH and
higher temperature. No viruses could be detected at either pH 7 or pH 5.3
after a few minutes at 55°C. At 22°C, the rate of inactivation was much
slower (30% to 50% in 100 hours at pH 7, and 95% in 100 hours at pH 5.3).
Though the poliovirus seems sensitive to low pH values, some other entero-
viruses are acid stable.
In a later study, Engelbrecht et_ al_. (1974) examined the decrease of bac-
terial population with time of leaching from a simulated landfill. They
reported that the total plate count of bacteria in leachate samples decreased
logarithmically over a 50 day period following first appearance of the leach-
ate. Total and fecal coliforms persisted for 40 to 60 days, and then rapidly
disappeared.
It was observed that initial densities of total coliform, fecal coliform,
and fecal streptococci reported by Engelbrecht et_ al. were several logs lower
than values reported by other investigators (Quasim and Burchinal, 1970;
Blannon and Peterson, 1974; Cooper et aJU, 1974b). Figures 11, 12, and 13
illustrate these differences which may have resulted from different methods
of analyzing the samples. Engelbrecht et al. used the membrane filter tech-
nique, while the other studies shown used the MPN method. Also a factor is
that the MSW had probably started to biodegrade prior to filling of the lysi-
meter. The waste was collected in a residential area of Cincinnati, randomly
selected and segregated, milled to a 1 in. size for placement in the lysi-
meter, and placed in cold storage in barrels for several days prior to ship-
ping to Urbana for this study. The lysimeter was filled with the waste five
days after collection. A temperature high of 65°C in the waste pile strongly
57
-------
I
-p
E'
o
u
•r)
cn
(0
"S
u
10
10
10
10
10
O—0 From Cooper et ot . , 1974b
0—Q From Engctorecht et ol . , 1974
From Qosim And Burchinol , 19 70
50 100
Time of Leaching (days)
Figure 11. Change in total coliform bacteria with time of leaching
(Engelbrecht and Amirhor, 1975)
58
-------
I
If
•5!
§
Q
-
a
10
8 10
10
From Cooper e' Jl., 19 74a
From Enqelbrecht et ol.j 1974
D UpPCr Pif>e From Blonnon And Peterson. 1974
• Lover Pipe
50
<_O[
JL.
•
<0.l
~5P-+
100 150 200 250
Time of Leaching (days)
oW
300
Figure 12. Change in density of fecal coliforms with time of leaching
(Engelbrecht and Amirhor, 1975)
59
-------
10'
CO
-p
•H
cn
10'
10-
10
10'
102
O O From Cooper etfli ,j 1974 t>
& a From Engelbrecht ejal-, 1974
D-—0 Upper Pipe
• • Lower Pipe
3|Qnfx)n An
-------
suggests that aerobic activity had already begun prior to placement in the
lysimeter. Hence, partial thermal inactivation of bacteria is also a possi-
bility.
In an attempt to describe bactericidal and virucidal factors within the
fill further, Engelbrecht and Amirhor (1975) reexamined conditions affect-
ing survival of S. typhimurium, fecal streptococci, and poliovirus in the
fill. Leachate samples were collected from a lysimeter containing milled MSW
(3,358 Ib), and from two landfills (one closed, the other operational).
Again it was found that inactivation was more rapid at pH 5.4 than at pH
7, and increased with increase in temperature. At 22°C, the effect of the
lower pH was more marked than at 55°C. For S. typhimurium at 22°C and pH 5.4,
there was a four log decrease in 48 hours (4.15 x KP cfu/ml to 60 cfu/ml). '
At pH 7.0 for the same time and temperature, S. typhimurium decreased approx-
imately 3 logs (4.5 x 105 to 5 x 102 cfu/ml). After only four hours at 55°C,
S. typhimurium concentration was less than 1 cfu/ml at both pH values.
For fecal streptococci, values dropped by six logs after 48 hours at pH
5.4 (2.99 x 106 to 4 cfu/ml), and by four logs at pH 7.0. Fecal strepto-
cocci were very sensitive to the 55°C temperature at both pH values
(<1 cfu/ml after four hours). Poliovirus inactivation was also very rapid at
pH 5.4 and 55°C (<10 PFU/ml after 15 minutes compared to 1.30 PFU/ml at pH 7).
Engelbrecht and Amirhor also showed that both the dilution of leachate
with water, and the age of material in the fill influenced the activation
capacity. Reduction in activation capacity was found to vary directly with
degree of dilution. For these studies, inactivation of bacteria in leachate
from the older fill was generally less than for leachate from the younger
fill.
An attempt was made to correlate the chemical and biological composition
of the leachate. Using ultrafiltration techniques to fractionate the leach-
ate, it was found that the degree of inactivation was greatest for a fraction
identified as 500 MW permeate (i.e., leachate containing material with molec-
ular weights greater than 500). This fraction contained relatively high con-
centrations of iron and zinc cations, and short chained fatty acids.
Reverse osmosis (RD) further fractionated the 500 MW permeate. The RO
permeate had a more pronounced effect on the stability of both the "S. typhi-
murium and the poliovirus, but no apparent effect on fecal streptococci.
Conversely, the RO retentate had a significant effect on the fecal strepto-
cocci but no obvious effect on S. typhimurium. Inactivation of poliovirus by
RO retentate proceeded slowly for .the first ten days (50% inactivation),
after which the rate of inactivation increased considerably.
RO permeate contained greater concentrations of very low molecular weight
fatty acids, and metal ions than the RO retentate. It was suggested that the
high concentration of fatty acids, and iron and zinc cations was partly re-
sponsible for inactivation of the S. typhimurium and the poliovirus. It was
not clear why the rate of inactivation of the fecal streptococci was greater
in the RO retentate.
61
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Results of inactivation tests with both bacteria and the poliovirus in
synthetic salt solution confirmed that high concentrations of iron and zinc
were associated with rapid inactivation, especially of the bacteria.
More recently, Riley et al_. (1977) have investigated the possibility that
the aliphatic acids present in raw leachate exert a bacteriostatic action on
coliforms. Chromatographic studies (paper and gas) established the presence
of acetic, proprionic, butyric, n-valeric, isovaleric, and n-caproic acids in
leachate collected from an aluminum pipe at the base of an operating waste
tip. Assay of this leachate on nutrient agar plates seeded with E. coli pro-
duced small, indistinct zones of growth inhibition. If the acids were re-
moved by ether extraction, then the "stripped" leachate did not inhibit coli-
form growth, while the acid concentrates gave sharp zones of inhibition meas-
uring 33 mm in diameter.
An on-going study of the chemical and microbiological characteristics of
landfill leachates is now being conducted by Scarpino (1978). The primary
objective of this study is to determine the health and environmental signif-
icance of the persistence of fecal streptococci in landfill leachates. The
project is divided into two phases: (i) to verify analytical methods and to
determine the presence of indicator organisms in leachate, and (ii) to study
the relationship between the extent of waste decomposition and the microbial
population dynamics. First published results of his investigation will be
available by the end of the year.
Cooper et al. (1974a) studied the effect of adding disposable diapers on
the composition of leachate from lysimeters simulating sanitary landfills and
open dumps. Sixteen "fills" and "open dumps" were loaded with unsorted
refuse that had been hammermilled 24 hours previously (densities of refuse
856 to 1000 lb/yd3 in the fills, 676 741 lb/yd3 in the open dumps). Various
amounts of diapers and feces were added to 12 of the lysimeters. The con-
centration of viruses added to each of the lysimeters was also varied. The
controls were two simulated sanitary landfills and two simulated open dumps
which received no feces, diapers, or viruses. Two fills were brought to
field capacity by weekly additions of water over a 16 week period, while the
rest were saturated with water over a two week period. Maximum temperatures
achieved were 29° to 38°C for the top 14 in. depth of fill, and 46° to 57°C
in the open dumps.
The total aerobic count decreased fairly steadily in leachate from lysi-
meters with and without added human infant feces and diapers. The addition
of feces and diapers resulted in no noticeable difference in the rate of
biodegradation of the MSW. The refuse itself had an extremely high level of
fecal streptococci (108/100 ml) and coliforms (105 to 106/100 ml). Total and
fecal coliform densities were similar, indicating widespread fecal contami-
nation of the wastes. The ratio of fecal coliforms to fecal streptococci in
the fresh waste indicated the presence of animal excreta in the MSW. Table
22 gives the initial and final bacterial concentrations in the leachate
samples.
62
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TABLE 22
MICROFLORA OF MUNICIPAL SOLID WASTE AND LEACHATE FROM SIMULATED LANDFILLS
(Cooper et a^., 1974a)
Organism Concentration
Total aerobic count Initial counts of 106 to 10 7 counts/100 ml
declined 2 to 3 logs over 20 weeks
Total coliform Initial counts of 105 to 106 counts/100 ml
declined rapidly to 10 within 8 to 10
weeks
Fecal coliform Composed 50 to 90 +% of total coliform
count, behaved similarly
Fecal steptococci Initial counts very high, about 108/100 ml
declining to 104 to 105 /100 ml at 20 weeks
Cooper e_t al_. (1974a, 1974b) also found that the appearance of poliovirus
type 1 in the leachates was sporadic over a 20 week period. Virus recovery
efficiency using EDTA and diluting the preclarified leachate with water 8:1
averaged 60%. No viruses were recovered from the two lysimeters brought to
field capacity over a 16 week period. For lysimeters brought to field
capacity within two weeks, there was very low recovery of viruses from the
first samples (average 2.5 PFU/5 ml). These results were considered suspect
by the investigators, so several lysimeters were emptied, refilled, and
reseeded with viruses. For the second test run, there were three consecutive
weekly recoveries of 150, 2,310, and 380 PFU/gallon." All further samples
were negative for the presence of viruses. No viruses were detected in
leachate from the open dumps, where, as previously mentioned, temperatures
averaged almost 20°C higher than the lysimeters.
Other studies on virus survival in the landfill environment seem to agree
with Cooper et a^. that few or no viruses appear in the leachate (Peterson,
1971a; Engelbrecht, 1973; Engelbrecht et a^., 1974; and Sobsey et. al_. , 1975).
Peterson detected poliovirus type 3 (150 PFU/100 ml) in one of 13 samples of
leachate from a lysimeter containing raw MSW. Here again, the lysimeter was
brought to field capacity more rapidly than would be considered normal, pro-
ducing leachate after only three days. Peterson also examined the survival
of poliovirus type-1 in a full scale sanitary landfill. Viruses were seeded
onto ground MSW which was placed in nylon bags, and inserted into a working
fill during normal operation. The bags were withdrawn periodically; on
examination no viruses were detected. Peterson also determined that there
was no virus migration in the fill, and concluded that at 40° to 60°C sur-
vival time of poliovirus type 1 in the fill would be about two to four days.
Engelbrecht et al. (1974) studied the inactivation of poliovirus type 1
and reovirus in a simulated landfill. They added viruses to the supernatant
-------
of centrifuged leachate samples, and found that poliovirus type 1 was not
significantly inactivated by initial leachates collected (days 36 to 47 of
lysimeter operation). Poliovirus inactivation by older samples of leachate
was more rapid. However, as the leachates became cloudy, and the samples
were not treated with EDTA before virus assay, it was not certain if the
viruses were inactivated, or adsorbed onto particulate matter in the leachate
sample. In contrast, reovirus was significantly inactivated after 36 days of
operation, and disappeared from the day 47 leachate after only 10 minutes
exposure.
Sobsey et a^. (1975) studied the survival of enteroviruses when inocul-
ated into simulated refuse contained in two lysimeters. Both laboratory and
field strains of poliovirus type 1 and echovirus type 7 were investigated.
None of these viruses were detected in leachate samples collected over a four
month period. The viruses were assayed by the plaque technique (small
volumes) and by the tissue culture technique (large volumes). The pH of the
lysimeters ranged from 5.4 to 6.1.
When viruses were added to the leachates, they were recovered with an
efficiency of 50% or more when concentrated 10- to 20-fold. This indicates
that the non-detection of viruses in leachate samples was not due to
deficiences in the detection method used.
The possibility of virus adsorption to MSW waste components was examined
by investigating the short-term interactions of viruses with paper, glass,
lawn waste, and foodscraps in (a) a salt solution (pH 5.5), and (b) in dis-
tilled water. The salt solution contained NaCl (2.5 g/l)t CaCfe (5.5 g/l),
MgCl2 (5 g/l)/ NH4C1 (0.75 g/1)/ and H3P04 (0.7 g/l)r and hence was similar
in composition to the major inorganic components of typical leachate.
While there was negligible adsorption in distilled water alone, for salt
solution (composition and concentration as indicated above) high percentages
of both viruses were adsorbed onto the solid waste components. Once the
viruses were solids-adsorbed, only a small proportion was removed by eluting
with either salt solution or glycine (pH 11.5).
The non-appearance of viruses in the leachate could also be explained if
the lysimeters were acting as plug-flow reactors. In this case, the lysi-
meters would not have been operational for a long enough period of time to
allow viruses to appear in the leachate.
Inactivation studies showed that survival of field-strain poliovirus in
composite leachates from both lysimeters was highly temperature dependent.
At 20°C, 95% inactivation of viruses took two weeks; at 37°C, 97% inacti-
vation was achieved within six days. The rates of inactivation were differ-
ent for the two lysimeters for reasons not determined (q.v. Glotzbecker and
Novello, 1975).
After termination of the experiment, the lysimeter contents were assayed
and found to contain no viruses. It was concluded that viruses may be re-
tained in a landfill for a long enough period to ensure inactivation. How-
ever, it was recommended that the mechanism of virus inactivation be studied
further, both in the laboratory and in the field.
64
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It should be pointed out that adsorption of viruses onto solids does not
rrean that viruses are inactivated. Several studies have demonstrated that
viruses (including coliphage T2, poliovirus type 1, and enteroviruses) retain
their infectious nature upon adsoption (Carlson et al., 1968; Moore et al.,
1975; Schaub and Sagik, 1975).
Movement of Microorganisms through Soil
Given the possible survival and leachage of bacteria and viruses from a
fill, the extent to which the organisms were retained, survive, or move through
various types of soil is obviously of paramount concern. Factors which
influence the behavior of microorganisms within the soil include (Gilbert et
al., 1976):
• soil texture/composition,
• soil moisture,
• salt concentrations,
• PH,
• climate (rainfall and temperature),
• nutrient availability; and,
• antagonisms.
Glotzbecker and Novello (1975) compared the survival of E. coli and
poliovirus in a sandy and a clay soil. They percolated leachate seeded with
E. coli (108 organisms/100 ml) down a clay soil column, and leachate contain-
ing JII_co]LL (108 organisms/100 ml) and poliovirus (105/100 ml) down a sandy
soil column. Leachates and percolates were examined for fecal coliform and
viruses.
The clay soil was most effective in retaining E. coli (3 fecal coliforms
/100 ml). Percolated leachate (640 ml) was collected for 119 days. This
volume was 1.8 times the calculated pore volume of the soil. E. coli
detected in percolate from the sandy soil column decreased from 1% (day 4) to
9% (day 14), to just over 0.1% on day 26. An increase from day 14 to 20 was
thought to be due to channeling in the soil (cf. Wellings et a^., 1975, also
reported breakthrough of viruses present in the soil as a result of fractures
and channels present in the strata).
Overall, more than 99% of E. coli disappeared from the leachate. Polio-
virus concentration in the percolate increased from 1% (day 4) to about 8%
(day 20), decreasing to 0.7% after 35 days.
Duboise et al. (1976) investigated poliovirus survival and movement in
sandy forest~soTT and confirmed the findings of previous investigators
(Wellings et aU , 1975, Schaub et al., 1975) that virus movement may be quite
considerable after rainfall. Movement of poliovirus I (Chat) was monitored
65
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through nonsterile core samples of a sandy forest soil. The core sairples
were loaded with either distilled water or dechlorinated final effluent from
an activated sludge treatment plant, to simulate alternate rainfall and land
irrigation respectively. The level of poliovirus applied was around 2 x 107
PFU of virus suspended in 20 ml of dechlorinated final effluent (Duboise et
al., 1976).
Application of dechlorinated effluent ("irrigation") enhanced retention
compared to the distilled water ("rainfall") for both continuous and inter-
mittent loading. The importance of pH was examined by adjusting the final
effluent to various pH values, and using as an eluate. At pH 9, virus
release was enhanced for both final effluent and water loadings. At pH 5.5,
virus retention was enhanced. Intermittent loading also improved virus
retention.
As the amount of "rainfall" was increased in volume, there was an accom-
panying increase in the percentage of viruses detected in the eluates from
the soil cores. When the cores were eluted with 500 ml of distilled water,
viruses, detected in the eluates ranged from 15 to 20% of the initial
concentrat ion.
It was shown that most of the viruses were retained in the top layer of
soil by adsorption onto ions contained in the effluent, up to the limits of
the soil's ion exchange capacity. Addition of distilled water resulted in a
dilution of ions and increased movement of viruses through the soil. Accord-
ing to Duboise, this suggests that an optimal range for poliovirus release
was exceeded. It also suggests that secondary bands of virus adsorption less
concentrated than the top soil layer might move down through the soil after
intermittent rainfall. This movement would be limited by the depth of the
soil, pH, ion concentration, soil moisture, etc.
To determine the effect of temperature, poliovirus survival and migration
in the soil cores was investigated for 84 days at 4°C and 20°C. There was no
apparent change in migratory ability over the 84 day period. After 42 days
at 20°C, no viruses were detected at a 10 cm depth (concentration 2 x 10 3
PFU/g soil at day 0). After 84 days at 20°C, viral concentration was 1.5
PFU/g soil at 1 cm depth (concentration at day 0 - 4.6 x 105 PFU/g soil).
Virus survival was greater at 4°C. After 84 days, concentration at 1 cm was
2.2 x 105 PFU/g soil, and concentration at 10 cm was 4.0 x 102 PFU/g soil.
Initial concentrations were 4.5 x 105 and 2.0 x 103 PFU/g soil at 1 cm and 10
cm depth respectively.
Damgaard-Larsen et a^. (1977) studied the movement of coxsackie virus and
tritiated water through four lysimeters containing clay (two), neutral sand
(one) and acidic sandy soil (one). They seeded municipal sludge with the
virus (initial concentration 106 TCID SQ/g), and dug the sludge into each
lysimeter soil. The pH of the clay soils ranged from 7.1 to 7.4, pH of the
neutral sand was from 6.0 to 6.4, and pH of the acid sand from 4.8 to 5.4.
The lysimeters (125 cm depth) were exposed to natural rainfall over a five
month period (December to May, total rainfall of 300 mm). The minimum air
temperature was -12°C, and the maximum temperature was 25.7°C.
66
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No viruses were found in leachate from any of the lysimeters at any time.
After 23 weeks, no viruses were detected in any soil sample. Tritium tracing
showed that there was some water penetration of the neutral sand by the begin-
ning of April; a month later tritium activity in the leachate was about 10
times the background activity. This represents a water breakthrough of about
1% of the total rainfall.
This study and a similar investigation by Lance et al. (1976) tend to
support the findings of Duboise et aJU discussed previously. Lance et al.
also examined movement of viruses in soil columns (250 cm depth) flooded with
secondary sewage effluent. Effluent containing 3 x 104 ppu/ml of poliovirus
type 1 (LSc) was passed through piping packed with loamy sand from an area of
the dry Salt River bed used over a four year period for groundwater recharge
of secondary effluent. The same soil had been flooded with sewage effluent
in the laboratory for a further three years.
Viruses were not detected in samples below 160 cm. Flooding of the col-
umn with the effluent did not result in virus desorption, nor in saturation
of the soil surface with viruses. Like Duboise et al_., Lance et a^. found
that flooding with deionized water increased the movement of viruses down the
column.
This movement was retarded by adding chloride to the deionized water.
Drying the column reduced or completely prevented desorption of virus
depending on the time allowed for drying. It was concluded that viruses
should be inactivated by passage through sandy soil provided that flooding
does not take place within 24 hours of land application.
The effect of alternate flooding and drying cycles on virus and enteric
bacteria mobility in land-applied secondary sewage effluent was examined by
Gilbert et a^. (1976). The effluent was percolated through six soil basins
(fine loamy sand/coarse sand/gravel/clay to a depth of 75 m), and water
samples were obtained from a series of observation wells (6.1 to 76.2 m deep)
after flooding every two months for a year. The average infiltration rate
was 90 m/year.
Poliovirus types 2 and 3, echovirus types 7 and 15, coxsackievirus B4,
and reovirus types 1 and 2 were all isolated from the sewage effluent. The
viral concentrations ranged from 158 to 7,475 PFU/100 liters. No viruses
were detected in the renovated water from any of the wells.
Salmonella sp. were also commonly found in the sewage effluent (17 to 26
counts/100 ml), but were never detected in the renovated water. Fecal coli-
forms, fecal streptococci, and total bacteria decreased by 4 logs (99.9%)
after passage of the wastewater through 9 m of soil. While it was clear that
the microorganisms were retained by the soil, the survival rate of the adsor-
bed viruses and bacteria was not determined.
This project (Flushing Meadows) has been continually operated for eight
years during which time viruses and enteric bacteria were either non-detectable,
or reduced to very low levels after filtering of the sewage effluent through
the soil recharge basins.
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Bitton et al_. (1976) studied adsorption of poliovirus type 1 and bacter-
iophage T2 onto soil columns covered with a constant head of either tap water
or secondary sewage effluent (3 cm). The sandy soil columns were removed
from a cypress dome, normally kept covered with secondary effluent. The tap
water was adjusted to pH 6.5, while the pH of the effluent ranged from pH 6.2
to 7.6.
Viruses were loaded on the columns either by suspending in tap water or
effluent and percolating through the soil at a constant flow rate, or by
placing a dose of the viruses on top of the soil, allowing them to soak com-
pletely in, and then eluting with secondary effluent.
For poliovirus type 1, adsorption was higher in the presence of tap water
(99.7%) than in the presence of secondary effluent (66.6%). For bacterio-
phage T2 suspended in tap water (initial concentration 3 x 104 PFU/ml),
adsorption on the sandy columns was about double (98.4%) that for T2 suspended
in secondary effluent.
It was also found that the secondary effluent desorbed greater concentra-
tions of both viruses than the tap water. It was postulated that organic
matter present in the secondary effluent (total organic carbon 27 to 37 mg/1)
in some way interfered with adsorption of the viruses on the soil columns.
Interfering substances have been shown to hinder virus adsorption onto various
materials (Carlson et a^., 1968; Oliver, 1968).
At the cypress dome site itself there is a clay loam layer (28% clay)
below the sand, while at the center of the dome is a layer of black organic
mud (61 cm). These layers may contribute to virus removal on site. However,
Wellings ^t aJL (1975) have isolated animal viruses from 305 cm deep wells in
the cypress dome indicating possible damage or structural inadequacies in the
clay layer.
All these studies indicate that movement of microorganisms through soil
is highly dependent upon a number of factors, and may be minimal or consid-
erable depending on the environmental factors discussed above. Survival and
movement of viruses in particular is of concern given that adsorbed viruses
may not be inactivated, but may be desorbed after a heavy rainfall to move as
a band through the soil.
Summary
There is obviously a possibility that pathogenic bacteria and viruses may
survive conditions within the sanitary landfill, and enter ground or surface
water through leachate penetration of the soil. However, there does appear
to be a significant decrease in viral and bacterial content of leachate with
time of operation or leaching of the fill. Also, the relatively high tempera-
ture (60°C) achieved during the first aerobic stages of waste biodegradation
is inimicable to many viruses and most pathogenic bacteria. It has also been
shown that the chemical and physical characteristics of the leachate contribute
toward both viral and bacterial inactivation.
68
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Adsorption of viruses onto material in the fill is likely, and partly
explains the low rate of recovery of viruses from landfill leachate. If
leachate does contain viruses, there is a possibility that the viruses would
be retained by the soil for a long enough period of time to become inactivated.
This would be especially true in very dry climates, or where rain is intermit-
tent and light.
IV. OXIDATION DITCH
The Process
Aerobic treatment of animal wastes may take place in a pond, lagoon or
ditch. When manures are held in a shallow container, dissolved oxygen is
probably sufficient for aerobic stabilization of the wastes. Otherwise, oxy-
gen must be added by means of floating aerators.
In the oxidation ditch, the waste slurry is circulated by use of a hori-
zontal shaft rotor. In addition to preventing settling out of solids, the
rotor aerates the waste. The ditch may be built directly below cattle penned
in a feedlot. Here, the ditch is covered with slatted flooring, and the animal
waste drops directly into a liquid medium present in the ditch.
Stabilization of wastes may be partially or completely accomplished
depending on the method of operation. If only partial stabilization is
achieved, the waste is generally held in an external lagoon until final dis-
posal. Several investigators mention the need for a holding basin to permit
flocculation and settlement of solids prior to containment within the ditch
(Diesch et_ al^., 1973). Environmental conditions vary considerably from one
operation to another, and within one ditch depending on the volume and the
nature of its contents. Variables, such as loading rate, pH, suspended
solids, biochemical oxygen demand (BOD), chemical oxygen demand (COD), dis-
solved oxygen, and temperature fluctuate considerably. One operational field
ditch is described in the section below. In 1967, there were over 400 oxida-
tion ditches operational in the U.S.
Several advantages to this mode of treatment include:
• relatively odor free operation;
• storage prior to land disposal;
• reduction of BOD and COD; and,
• economy of labor possible where slatted floors used.
Survival of Pathogens
As previously indicated, the increased confinement of livestock in feedlots
has resulted in increased difficulty in the hygienic disposal of wastes. Though
it is well-known that more than 150 diseases can be transmitted to man by ani-
mals, there is little quantitative data to describe the extent of this trans-
mission. However, there has been several studies to develop methods of
69
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detection and rates of survival of the more widespread and hazardous patho-
genic organisms found in animal wastes.
Diesch e_t aJU (1973) studied detection and survival of Leptospira pomona
and SalmonelTaTyphimurium in a laboratory model (1:10 scale) of an opera-
tional field oxidation ditch. Variables investigated were pHf dissolved
oxygen, temperature, and level of total solids.
The operations of the field unit oxidation ditch were previously studied
to determine essential environmental and working parameters for operation of
the simulated model. Briefly, the field unit consisted of a continuous chan-
nel of dimensions 172 feet x 7 feet x 4 1/2 feet deep. The unit was lined
with concrete to prevent percolation through the soil, and roofed with a
slatted floor. Water was added to the ditch, and oxygen was supplied to the
level of 0.5 to 1 ppm of dissolved oxygen in the manure and sludge. The
entire unit was contained in a rigid steel building, and housed from 36 to 45
head of cattle. Waste generated by the cattle dropped through the slats into
the ditch.
Severe foaming occurred within the ditch over the winter (November to
January). The possibility of aerosol transmission of pathogens could not be
ruled out. An initial plan to collect and study effluents discharged from
the field unit was abandoned. Over a three-year period, no effluents were
discharged.
Four cattle (average weight 1100 Ib) died of idiopathic toxicosis. These
deaths occurred hours after the rotor malfunctioned and according to Diesch
et al. may have been due to emission of toxic gases from the inadequately
aerated manure during this period.
Two laboratory models were designed to simulate the conditions prevailing
in the field unit. Both models were cooled by circulating ethylene glycol
through a stainless steel trough within the ditch. The cooler-condenser unit
was installed below each ditch which was insulated with two in. thick rigid
styrofoam. The ditches also had a plexiglass cover to protect the operators
against aerosols. Table 23 gives the operational parameters for Model A.
Model B was identical to Model A except that Model B had a storage pit to
facilitate separation and removal of solid materials. Two designs of rotor
were tested in Model B. The brush-type rotor was abandoned because of too
low water velocities. Cooling of the ditch was required during winter
operation (heated building) and slight heating during summer.
Survival times of Leptospira pomona and Salmonella typhimurium in the
manure slurry and in effluent and sludge from the settling are given in Table
24. As can be seen from these data, aeration of manure in the ditch
generally resulted in greater survival of the microorganisms than in the non-
aerated effluents and sludge. However, for S. typhimurium at 2°C survival
was longer in the sludge (87 days) and effluent (66 days) than in the slurry
(47 days).
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TABLE 23
OPERATION OF A MODEL OXIDATION DITCH (MODEL A DATA)
(Diesch et al., 1973)
Temp: surtmer* 13° to 25°C
winter 1.7° to 6.4°C
PH 6.8 to 8.4
Total solids (TS) 5,802-135,333 mg/1
TS attempted range 5,000-10,000 mg/1
Dissolved oxygen 1 to 5 ppm
Initial volume of manure 113 liters
Daily loading of manure 2.2 Ib/dayt
* Dow-Corning Antifoam A Spray added to prevent foaming in summer.
t Added regularly up to 10,000 mg/1 TS; then added intermittently to maintain
at this level. Addition of unchlorinated well water was necessary to keep
TS within desired range.
Burrows and Rankin (1970), in a study of pathogen survival in cattle
slurry, also found that certain bacteria (including Salmonella sp.) survived
for a longer period of time in an aerated cattle slurry than in non-aerated
samples. The bacteria studied were Salmonella typhimurium, Salmonella dublin,
Brucella abortus, Staphylococcus aureus, and Escherichia coli. Slurry was
collected from five farms where it was stored in polyethene bins (9 gallons
capacity). Each bin was seeded with one of the cultures (106 to 107 viable
units/ml) and then covered. Sanples were collected daily after agitation of
the slurry.
All microorganisms decreased in density with time. In most cases, bac-
teria could not be counted 10 weeks after seeding (direct counting and enrich-
ment techniques), though viable organisms were still detected after 12 weeks.
Organisms in the slurry from one particular farm survived for a longer time
than organisms in the other slurry samples. The slurry tank on this farm was
emptied three times a week, so the slurry in the bins was coirparatively fresh
at all times and probably contained a greater amount of dissolved oxygen.
Also, the slurry had a higher solids content (4.5% as opposed to 0.2% to 2.6%),
and a slightly lower pH (7.2 as opposed to 7.6).
Other investigators have also shown that survival of leptospires is
longer in aerated sludges. Chang et al. (1948) indicated that survival of
leptospires in domestic sewage was 12 to 14 hours. When the sewage was
aerated, survival time rose to two to three days. Other conditions influen-
cing survival of leptospires are summarized in Table 25.
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TABLE 24
SURVIVAL OF LEPTOSPIRA PCMONA and SALMONELLA TYPHIMURIUM
(Diesch et al.f 1973)
Substrate Organism Temp. Duration
Cattle Leptospira 20°C 138 days
pomona
5 days
14 days
2°C 18 days
9 days
11 days
Salmonella
typhimurium 20°C 17 days
14 days
2°C 47 days
87 days
66 days
Comments
*Minnesota summer temp.
survival time in slurry
some organisms still
viable
Survival time in effluent
Survival time in sludge in
model settling chamber
Slurry winter tempera-
tures, some organisms
still viable
Survival in effluent
In sludge in model set-
tling chamber
Slurry survival time
Effluent and sludge
Slurry survival time
Sludge survival time
Effluent surival time
*Maximum time measured.
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TABLE 25
CONDITIONS FAVORABLE TO DESTRUCTION OF LEPTOSPIRES
Condition Reference
Presence of other microorganisms Noguchi, 1918
Chang et al_., 1948
Okazaki & Ringen, 1957
Non-aeration Chang et al., 1948
Diesch et al., 1973
pH < 5 to 6 Okazaki & Ringen, 1957
> 7 Smith and Turner, 1961
< 8.4 Stockard et al., 1968
Temperatures < 7°C Okazaki & Ringen, 1957
> 36°C Ryu and Liu, 1966
Lack of Water Okazaki & Ringen, 1957
Derbyshire (1976) studied survival of enteroviruses in a series of field
and laboratory experiments, and found that the viruses were more rapidly
inactivated in aerated liquid pig manure than in untreated pig manure. Samp-
ling of raw and aerated manure concentrates over a ten week period consistently
showed the concentration of the former to be three logs greater than the
latter.
In related laboratory studies, raw liquid pig manure was seeded with
swine enterovirus, and continuously aerated and stirred for 71 days at 22°C.
The controls were seeded untreated manure. The virus was present up to 14
days in the aerated samples, and 71 days in the control. The mechanism of
inactivation was not identified. Viruses were recovered by concentrating the
waste by PE-60 adsorption, and isolating the viruses from the concentrates on
pig kidney cell cultures.
Summary
From the limited material presented, it appears that prolonged survival
of some of the more common pathogens present in animal wastes is possible
within the oxidation ditch environment. However, as pointed out by Diesch
et al. (1973), methods of operating field facilities vary greatly, and the
environmental characteristics of even one specific ditch may change on a
daily basis. Given that units may be badly designed or poorly managed,
pathogens may not only survive but thrive under certain conditions.
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V. ANAEROBIC DIGESTION
The Process
Anaerobic digestion involves biodegradation of the cellulosic fraction of
solid wastes by at least three sets of organisms: cellulolytic, acetogenic,
and methanogenic bacteria. Initially, the cellulose is converted to short
chain volatile acids. The methane-forming bacteria then convert the products
of acidogenesis to a mixture of methane and carbon dioxide. The process can
be used for stabilization of MSW, manures, agricultural wastes, and sewage.
Anaerobic digestion has received a great deal of attention recently as a
means of producing methane gas. However, the process is still in the pilot
plant and demonstration stages for solid wastes, though it is a common method
for stabilizing sewage sludge.
Digestion can occur at mesophilic (30° to 40°C) or thermophilic (50° to
60°C) temperatures. The detention time in the digester depends on the temp-
erature of digestion and the design of the fermenter. At lower temperatures,
detention time is longer. Generally, thermophilic processes would take from
5 to 15 days with complete mixing of the feed. A completely mixed mesophilic
digester might take from 15 to 30 days to stabilize the waste. This is the
process as currently applied to municipal sewage sludges.
The batch load digester employs two completely mixed reactors, one of
which ferments while the other is fed, resulting in an increase in
efficiency. Like the completely mixed process, it is necessary to premix and
dilute the manure, resulting in an improvement in biodegradation and gas pro-
duction. The plug-flow longitudinal reactor does not mix contents, and
operates at 20° to 30°C for 30 to 50 days. It is common practice to add
nutrients containing nitrogen and phosphorus to the digesting wastes, and to
balance the pH to the optimum value for growth of methanogenic bacteria by
addition of alkali.
Survival of Pathogens
Literature reports discussing the advantages of digestion of solid waste
point out that the sludge remaining is odor-free, does not attract flies, ands
is biologically stable. It is interesting to note that while many researchers
cite possible destruction of pathogens, studies to confirm or deny this
assumption are not yet available.
As Gaby (1975) pointed out, most of the pathogenic bacteria found in raw
refuse are facultative anaerobes, and could survive landfill conditions. It
might be suspected that pathogens could survive digestion at mesophilic tem-
peratures, or even at thermophilic temperatures if the retention time is very
short, and the contents of the digester are not well mixed.
Since no studies were available documenting the extent of possible
bacterial and viral survival in digested solid waste, it was decided that an
examination of the survival of microorganisms in digested sludge would give
some perspective to this potential problem.
74
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Inactivation of viruses in digested sludge may be caused by one or more
of tiie following factors (Palfi, 1973; Warl and Ashley, 1976):
• heat denaturation of the protein coat;
• enzymatic action on the protein coat;
• natural die-off; and,
• cleavage of viral proteins followed by nicking of
encapsulated RNA.
A completely mixed digester may give poor results for virus destruction
because some influent may exit early with the effluent. Also, the tempera-
ture may not be constant throughout the digester. Even for a high even temp-
erature, adsorption of viruses onto particulate matter may protect from
inactivation by heat. However, there seems to be general agreement that
virus inactivation in digested sewage sludge is primarily a function of
temperature and residence time.
Palfi (1973) has examined virus survival in digested sewage sludge before
and after modifications in digester operation. Hence, he was able to compare
different operating conditions though he was not able to control the vari-
ables. Initially, the digester operated with a retention period of 21 days
at 30°C, continuous inflow and outflow of sludge, and constant mixing.
After year-round sampling, he found that 28 out of 74 samples (38%)
contained one or more virus strains. Reovirus (35%) and echovirus type 11
(15%) were present in the highest number. Forty (40) strains were identified
in all. Viral densities ranged from 2.3 to 175.5 MPNCU/100 ml (most probable
number of cytopathogenic units). The average density was 39 MPNCU/100 ml for
the November to December period. The viruses were determined by the MPN-
method using 5-5 primary monkey kidney tube cultures.
Operating conditions were modified so that the sludge was digested in
three stages. Retention time was 20 and 10 days at stages one and two
respectively with complete mixing of sludge. Retention at stage three was an
additional 10 days without mixing. The temperature was raised to 33°C.
For winter sampling, 13 of 82 samples (15%) were positive for viruses.
Only 14 strains were identified. More than half the positive samples
contained poliovirus type 3. The average viral concentration was 5.4
MPNCU/100 ml; the range was 2.3 to 19 MPNU/100 ml.
Lund (1971) has also isolated viruses from sewage sludge digested for 50
to 60 days at 50°C. She noted an increase in heat stability of poliovirus
compared to other types of enterovirus. Neither Palfi nor Lund could deter-
mine virus recovery efficiency, as their data were drawn from operational
experience.
Ward and Ashley (1976) have studied the inactivation of radioactive carbon
labeled poliovirus in digested sludge under controlled laboratory conditions.
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They found that while the virus was fully recovered from the sludge, its in-
fectivity was inversely proportional to the time and temperature of
incubation. The decrease in infectivity ranged from greater than 1 log/day
at 28°C to about 1 log/5 days at 4°C. Infectivity of both free and solids-
associated virus was found to be identical. The process was investigated at
low temperatures to minimize the effects of heat inactivation. Raw sludge
was shown to have no virucidal activity, and, hence, it appears that
virucidal agents were produced by the bacteria of digestion.
In related studies, Ward et cd. (1976) confirmed the heat protective
effect described by Lund for poliovirus. At temperatures of 43°C, 47°C, and
51°C, poliovirus was bound to solids in both raw and digested sludge. The
inactivation was more rapid, however, in digested sludge.
Suspending raw sludge solids in the supernatant of digested sludge
produced irreversible inactivation of viruses. At 61°C, five minutes contact
with the supernatant improved the inactivation of raw sludge from 98% to
99.9% for poliovirus type 1 (Chat). At 51°C, five minutes contact improved
the inactivation of raw sludge from 96% to 99.99% for poliovirus type 1
(Mahoney). For poliovirus type 2 (712) at 51°C, there was an improvement
from 48% inactivation in raw sludge to 99% inactivation with addition of the
supernatant.
Ward et: al. pointed out that as they experienced difficulties in recover-
ing viruses from the digested waste, that the actual degree of inactivation
might be considerably less than indicated.
Given that solid waste may be contaminated with various parasites (Gaby,
1975), there exists the possibility of the survival of nematodes, protozoa,
and cestodes in digested solid waste. Again, there are no available studies
for MSW, though there have been a series of investigations of parasite sur-
vival in anaerobically digested sewage sludge.
Ova of Ascaris 1. suum in sewage sludge survived conditions simulating
the anaerobic digestion process, and later became embryonated (Fitzgerald and
Ashley, 1977). Sludge appeared to inhibit development, while protecting the
ova. Ova failed to embryonate when held at 38°C for 21 or 25 days in sludge,
but after removal and air exposure in 1% formalin for 58 days at 22°C, up to
90% of the ova embryonated. Ova held in physiological saline for 25 days
failed to embryonate. Under the same conditions, oocysts of Eimeria stiedai
were destroyed within five days.
The sludge used in this study was collected from four different sources.
One of the four systems was lethal to the ova, illustrating the highly vari-
able nature of sludge.
Fox and Fitzgerald (1977) have found the eggs or cysts of 10 genera of
parasites in anaerobically digested sewage sludge. The range of egg or cyst
counts per 100 g of digested sludge from four treatment plants was:
Ascaris lumbricoides 11 to 120 counts/100 g (0 to 113)
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Toxocara sp. 101 to 340 (0 to 279)
Tpxascaris leonina 0 to 16 (0 to 37)
Trichuris sp. 0 to 23 (0 to 23)
Cestodes (Taenia sp.
and Hymenolepis sp.) 0 to 33
Coccidia (Eimeria sp.
and Isospora sp.) 0 to 372 (0 to 50)
Entamoeba coli 0 to 34
The values in parenthesis refer to the concentration of the parasites in raw
sewage for five treatment plants.
The viability of the nematode ova was determined by Arther and Fitzgerald
(1977). Ova were isolated from fresh sludge by means of sugar flotation.
Extracted ova were placed in 1.5% formalin, and aerated for 21 to 28 days at
22°C. Ova were then removed from the formalin, when it was found on exami-
nation that larval development had occurred for A. lumbricoides (58%), T.
leonina (57%), Tbxocara sp. (48%), and Trichuris sp. (33%). Studies are
continuing to determine the ability of the ova to infect suitable animal hosts.
Digested sewage sludge may contain pathogenic bacteria as well as viruses
and parasites. Hess and Breer (1974) found that 81.9% of 136 sanples of an-
aerobically digested sludge contained Salmonella sp. Maximum concentration
was 106 organisms/liter with a mode of 103/liter.(The average concentra-
tion of Salmonella sp. in raw sludge was 10^ organisms/liter.) The average
value of E. coli in digested sludge (104 samples) was 107/liter, and in raw
sludge 10y organisms /liter.
Hess and Breer also demonstrated survival of Salmonellae in digested
sludge for up to 72 weeks after spreading on pastureland. They found a
direct correlation between the spreading of unsanitized sludge on land, and
an outbreak of salmonellosis in cattle after grazing upon the pasture.
Wizigmann and Wiirshing (1974) have also demonstrated survival of Salmon-
ellae, enterococces, and total enteric bacteria after anaerobic digestion of
sludge. As MSW and animal manures may also contain these organisms, there
remains the possibility that they may survive in digested solid waste. Given
the disease control measures practiced on the modern farm, it seems possible
that MSW, of variable and uncertain composition, is more likely to contain
problem organisms than manures.
Summary
No studies are yet available documenting the possibility and extent of
pathogen survival in anaerobically digested solid waste. Studies of digested
sewage sludge have indicated survival of pathogenic microorganisms at both
mesophilic temperatures (viruses, bacteria, and parasites), and thermophilic
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temperatures (viruses). An increase in heat stability of poliovirus has been
noted by several researchers.
It would appear that survival of pathogens present in solid waste (MSW
and manures) is a possibility, depending upon the design and operating para-
meters of the digester. Temperature, time of residence, and mixing of the
digesting waste are all determining factors.
VI. OTHER PROCESSES
Magnetic Separation
High^gradient magnetic separation (HQ^S) is a new technique to extract
weakly paramagnetic submicron particles from wastewater and slurries (DeLatour
and Kolim, 1976). The treatment relies on addition of a strongly magnetic
seeding agent like magnetite to the water. A chemical coagulant (any aluminum
or ferric salt at 3 to 20 ppm) is also added, and the suspension agitated for
up to five minutes. The coagulum formed is removed in the HQYIS.
DeLatour and Kolim demonstrated complete removal of total coliform and
fecal coliform bacteria from river bottom sludge after addition of 5 ppm of
A13+ (form not indicated), and 1000 ppm Fe^ and application of a magnetic
field of 1000 gauss. Concentrations of the controls were 20,000
organisms/100 ml for total coliforms, and 1,200 organisms/100 ml for fecal
coliforms. Flow rate of the sludge was 30 gpm/ft2. Total coliforms averaged
35/100 ml in surface water treated with 4 ppm Al3+(form not indicated), and
1000 ppm Fe304 with a field of 10 k gauss. Flow rate was 300 gpm/ft2 and the
control contained 22,000 organisms/100 ml.
Bitton and Mitchell (1974) demonstrated H(M3 as a means of removing
Escherichia coli bacteriophage T-y from water. The virus was adsorbed onto
magnetite in the presence of calcium chloride by passing the virus-containing
water through a filter placed in a magnetic field. The process accomplished
99% removal when the magnetite concentration was 400 ppm. Metcalf (1976) has
demonstrated the feasibility of removing poliovirus from water using HOIS.
It was not determined if there have been any attempts to remove pathogens
from solid waste systems by HGMS, but presumably animal slurries might be
amenable to this approach considering their high water content (e.g., cow
manure may be 85% water).
Gamma Radiation Sterilization
Radiation sterilization of agricultural or municipal solid wastes has
been suggested as the first stage of resource recovery (Padova et a^., 1974).
Since animal wastes may contain high densities of bacteria including
Salmonellae, refeeding of these wastes may be hazardous. Poultry waste, for
example, contains from 7 x 105 to 3.6 x 106 total bacteria/g with a coliform
count from 6 x 102 to 1 x I03/g (Carmi and Ashbel, 1974). Blair and Knight
(1973) have found Salmonellae in 33% of poultry samples analyzed.
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Irradiation of poultry wastes prior to refeeding was suggested by Jackson
(1970-1971). He has described a plant to treat 6.0 tons of poultry slurry
daily. At a moisture content of 82% to 83%, a dose of 1.2 x 105 rad "should"
kill "most" of the bacteria present, and enhance solids separation.
Simon and Tamasi (1974) have also described a plant to irradiate animal
wastes to produce a nutritive and microbiologically safe feed. They reported
destruction of Salmonellae in liquid swine manure at 0.4 Mrad.
It has also been suggested that irradiation of MSW could yield an animal
feed. Padova et aJU (1974) described a proposed pilot plant to grind and
separate 75 to 150 tons of garbage daily, yielding 50 to 100 tons of putres-
cible matter. Samples from this plant would undergo irradiation, and be
tested as a potential feed.
An additional use of irradiation-cured MSW has been proposed by Feates
and George (1974). They have treated compacted polymer-impregnated MSW with
gamma radiation to produce formed structural materials suggested as a replace-
ment for concrete, wood, or aluminum in building.
More data is available for irradiation of sewage sludges than for solid
waste. Van den Berg et. a^. (1974) have described the complete kill of fecal
coliforms in digested~~sludge at a dose of 120 Krad. At a water content re-
duced 50%, irradiation alone reduced fecal coliforms by only one log at doses
of 240 Krad.
Wizigmann and Wursching (1974) demonstrated that after irradiation of
sludge (60Co 260 Krad in 210 minutes), total bacterial and enterococcal
counts were reduced by two logs and five logs, respectively. Salmonellae
were found in two of 40 samples of irradiated sludge (and 16 of 25 samples of
digested sludge). The destruction of Ascaris cysts and ova by irradiation
was unconfirmed by the investigators.
Summary
It is not clear how effective, and how technically and economically feas-
ible, the above processes might be. However, they represent future options
in solid waste management, and illustrate the efforts that are being made to
improve waste management practices.
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SECTION 5
ANALYTICAL METHODS
Analytical methods for use in the studies discussed in Section 4 are
tabulated below. As previously mentioned, many of these methods are
standard. Each procedure described is detailed; the references at the foot
of each page allude to the studies which used this technique or a close
modification. The publication Methods for Bacteriological Examination of
Solid Waste and Waste Effluents by Dr. Peterson of the National Environmental
Research Center, Cincinnati, was an invaluable source of information for this
section. Interested readers are referred to this publication for further
details of general laboratory procedures and bacteriological methods.
PROCEDURE - COLLECTION OF SOLID WASTE SAMPLES
Organisms n.a.
Methodology
Using sterile tongs collect 20 to 40 random samples (100-200 g). Place
in sterile containers. If source contaminated, wear disposable gloves.
Avoid external contamination of the container. Identify samples in-
cluding all relevant data — time, date, location, temperature, etc.
Send to laboratory.
Limitations or Precautions
Examine within 1 hour after collection; in any case, no later than 30
hours after collection. Maintain temperature of collection as closely
as possible.
Additional Comments
References:
Peterson and Stutzenberger, 1969
Peterson, 1971
Peterson, 1972.
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PROCEDURE - COLLECTION OF LIQUID SAMPLES, QUENCH WATER, OR LEACHATE
Organisms n.a.
Methodology
If source contaminated, wear rubber gloves. Collect in sterile bottle or
plastic bag leaving air space for mixing the sample prior to assay.
Identify samples with all relevant data.
Limitations or Precautions
Protect containers from damage while shipping. Examine within 4 hours.
Maintain collection temperature as nearly as possible. Sample contains
residual chlorine, add 100 mg/1 sodium thiosulfate prior to collection of
sample to neutralize chlorine.
Additional Comments
Peterson (1971) concentrated quench water samples on a diatomaceous earth
layer.
References:Peterson and Stutzenberger, 1969.
Peterson, 1971
Peterson, 1972.
PROCEDURE - COLLECTION OF INCINERATOR STACK EFFLUENTS
Organisms n.a.
Methodology
Use Armstrong portable sampler mounted on steel plate with attached
sampling assembly and vacuum pump as described by Peterson (1972). Dry
heat sterilize prior to use. Draw effluents through sterile stainless
steel water-cooled probe at a rate of 1 ft3 of sample/minute (vacuum 14.3
on of water). Collect sample for 10 minutes (10 ft3). Identify and ex-
examine with 48 hours.
Limitations or Precautions
Reduce frothing by inserting end of probe entering the sample above the
buffered solution (1.27 cm). Insert probe into various stack locations
to give representative samples. Keep the probe dry since organisms may
be adsorbed in wall moisture.
Additional Comments
Peterson (1971) sampled stack effluents at the primary outlet, the
electrostatic precipitator outlet and the scrubber stack.
References:
Peterson and Stutzenberger, 1969
Peterson, 1971
^ Peterson, 1972.
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PROCEDURE - COLLECTION OF DUST SAMPLES
AND DETECTION OF GRAM POSITIVE AND NEGATIVE BACILLI
Organisms Gram Positive and Gram Negative Bacilli
Methodology
Draw air through sterile portable Anderson sanpler at rate of 1 ft? /min-
ute (vacuum of 15 in. Hg). Plates in sanpler are trypticase soy agar
(TSA) containing 5% sheep blood for respiratory tract and skin bacteria
(gm positive bacilli). Use 6 plates per sample. Use eosin methylene blue
agar for detection of intestinal tract bacteria (gm negative bacilli).
After collection withdraw plates, cover and incubate aerobically at 35°
0.5°C.
Limitations or Precautions
Maintain aseptic conditions throughout collection.
Additional Comments
Sample run for 15 seconds (Armstrong and Peterson, 1972) to give well
separated 1-30 colonies.
References:
Peterson, 1971
Armstrong and Peterson, 1972.
Peterson, 1972.
PROCEDURE - PREPARATION OF SOLID AND SEMI-SOLID SAMPLES FOR ANALYSES
Organisms n.a.
Methodology
Composite all random samples in a beaker (5000 ml), mixing well. Trans-
fer weighed 200 g subsample into sterile blender. Homogenize for 15 sec-
onds at 17,000 rpm with sterile phosphate buffered solution (1800 ml).
Prepare series of serial decimal solutions (10~1, 10~2, 10~3, 10~4) by
repeated dilution of 1 ml solution in 9 ml phosphate buffered water.
Limitations or Precautions
Make sure each solution is homogenized prior to sampling for subsequent
dilution by shaking vigorously 25 times.
Additional Comments
References:""
Peterson and Stutzenberger, 1969
Peterson, 1971
Peterson, 1972
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PROCEDURE - BACTERIAL COUNT BY AGAR POUR PLATE
Organisms Bacteria
Methodology
Pipe the prepared solution of sample (0.1 ml, 1 ml etc.) onto
duplicate trypticase soy agar plates with 7% defibrinated sheep blood
(TSA + blood). Add 10-12 ml of melted tryptose glucose extract agar to
petri dish. Mix well by rotating or tilting. Solidify as rapidly as
possible. Invert plates and incubate for 24 ± 2 hours at 35°± 0.5°C.
Count plates with 30-300 colonies using Quebeck colony counter. Express
results in counts per gram of waste (wet weight) per 100 ml water.
Limitations or Precautions
Accurate to only 2 significant figures.
Additional Comments
References:
Peterson and Stutzenberger, 1969.
Peterson, 1971
Peterson, 1972.
PROCEDURE - BACTERIAL COUNT BY AGAR STREAK PLATE
Organisms Bacteria
Methodology
Pipe the 0.1 ml sample of serially diluted samples on surface of labeled
duplicate blood agar plates. Plates contain TSA + blood spread evenly
over surface with sterile glass spreader. Invert and incubate for 24± 2
hours at 35° ± 0.5°C. Count plates with 30-300 colonies.
Limitations or Precautions
Additional Comments
References:
Peterson, 1971
Peterson, 1972.
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PROCEDURE - DETECTION OF COLIPORMS
MOST PROBABLE NUMBER (MPN) TECHNIQUE
Organisms Total coliforms
Methodology
Presumed Positive Test; Inoculate serial dilutions of sample into 5
large tryptose broth fermentation tubes. Incubate at 35°± 0.5°C for 24±
2 hours. If no gas present, incubate up to 48± 3 hours.
Confirmed Test; Use a sterile platinum loop (3 nun diameter) to transfer
medium from presumed positive tubes to a fermentation tube containing a
brilliant green lactose bile broth (2%). Incubate at 35°± 0.5°C for
48± 3 hours. The presence of gas in any tube indicates a confirmed pos-
itive test.
Completed Test; Streak samples from all confirmed positive tests on
eosin methylene blue agar plates as soon as gas is detected. Incubate
for 24 ± 2 hours at 35°± 0.5°C. Transfer one or more colonies from
plate to lactose tryptose broth in fermentation tubes and nutrient agar
slants. Incubate as before. Prepare gram stained smears from agar
slants if gas detected in lactose broth. Examine smears under oil immer-
sion. Compute MPN as indicated in APHA 1976.
Limitations or Precautions
Additional Comments
MPN best technique for quantifying coliforms in solid waste. Peterson
(1971) also used membrane filter technique for 3 incinerators in the 8
incinerator study. Spino (1971) also used membrane filter technique in
the New Orleans Incinerator Study.
References:
Peterson and Stutzenberger, 1969
Peterson, 1971
Peterson, 1972
Blannon and Peterson, 1974
Glotzbecker and Novello, 1975
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PROCEDURE - DETECTION OF COLIFORMS
Organisms Fecal Coliforms
Methodology ~ ——
Presumptive test as indicated on previous page. Transfer 3 mm loop of
broth from positive presumptive test to an E.G. broth fermentation tube.
Incubate in water bath for 24 hours at 44.5°± 0.5°C. Gas production is
a positive indication of fecal coliforms.
Limitations or Precautions
Tubes must be placed in water bath within 30 minutes of preparation.
Additional Comments
References:~"Peterson and Stutzenberger, 1969
Peterson, 1971
Peterson, 1972
Blannon and Peterson, 1974
Gaby, 1975
Glotzbecker and Novello, 1975
PROCEDURE - DETECTION OF VIABLE HEAT-RESISTANT SPORE FORMERS
Organisms
Heat-resistant spore-forming microorganisms capable of surviving 80°C
for at least 30 minutes.
Methodology
Transfer volumes of original and diluted samples (10 ml) into screw-
capped test tubes. Heat for 30 minutes at 80°C. Cool in cold water for
5 minutes. Determine viable heat resistant spores by agar pour plate
method described previously.
Limitations or Precautions
Water line must be 1 1/2 in. above level of samples in tubes.
Additional Comments
References: ~~ Peterson, 1972.
Peterson and Stutzenberger, 1969
Peterson, 1971 ^^
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PROCEDURE - DETECTION OF ENTERIC PATHOGENIC ORGANISMS
IN QUENCH WATER, INDUSTRIAL WATERS AND IN LEACHATE
Organisms Shigella and Salmonella sp.
Methodology
Filter sanple (800 ml) through a 1 in. layer of sterile diatomaceous
earth on a stainless steel membrane filter holder. Add half the clay to
90 ml of Selenite F enrichment broth and half to 90 ml of Selenite bril-
liant green sulfa enrichment broth. Shake both bath flasks well and
incubate for 16-18 hours in a water bath at 39.5°C. Streak one loopful
from each enrichment on four sets of plates of Salmonella-Shigella (SS)
agar, bismuth sulfite (BS) agar, eosin methylene blue (EMB) agar to
brilliant green agar and McConkey's agar. Incubate plates for 24-48
hours at 37°C. Transfer characteristic colonies to triple sugar iron
(TSI) agar slants. Incubate overnight at 37°C. Further identify accord-
ing to methods of Edwards and Ewing (1962).
Limitations or Precautions
Additional Comments
Reference:Spino, 1966
Peterson and Klee, 1971
Peterson, 1972.
PROCEDURE - DETECTION OF FECAL BACTERIA IN COMPOST
OrganismFecal Streptococci
Methodology
Incubate on KF streptococcal broth for 48 hours at 35°C.
Limitations or Precautions
Additional Comments
KF streptococcal broth is more conducive than KF streptococcal agar when
broth tested simultaneously. Samples were prepared as described by
Peterson, 1972 (q.v.).
Reference:Gaby, 1975\
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PROCEDURE - DETECTION OF GRAM POSITIVE BACTERIA IN COMPOST
Organisms Coagulase Positive Staphylococci
Methodology " ~
Prepare serial decimal dilutions of compost suspensions. Plate on Staph
110 medium and incubate at 37°C for 24 to 48 hours. Small round glist-
ening low colonies subcultured and later tested for coagulase activity.
Limitations or Precautions
Additional Comments
In Gaby's study, Chapman-Stone, TPEY and 5% blood agar were also compared
as media for isolating Staphylococci. Colonies grown on Staph 110 were
easiest to recognize.
Reference:~~Gaby, 1975.
PROCEDURE - DETECTION OF PATHOGENIC FUNGI IN COMPOST
Organisms Various Species
Methodology
Add compost (5 g) to sterile physiological saline (100 ml). Shake to
suspend and centrifuge for 15 minutes at 2500 rpm. Decant supernatant
and mix sediment with penicillin (10,000 units) and streptomycin (10 mg).
After 20 minutes standing at room temperature, inoculate 3 white Swiss
mice intraperitoneally each with 0.5 ml of sediment. After 3 weeks,
sacrifice mice. Remove and mince spleen and portion of liver. __ Use small
portions to inoculate 2 tubes of Sabouraud's agar (I) and 2 tubes of
Sabouraud's agar plus cycloheximide (0.5 mg/ml) and chloromycetin (0.05
mg/1) (II). Incubate for 4 weeks at 25°C, examining weekly. Prepare
smears of likely colonies and identify by standard cultural methods.
Also inoculate I and II with portion of the concentrated sediment. Incu-
bate for 6 weeks at 25°C and identify by cultural characteristics.
Limitations or Precautions
Additional Comments
Reference: ~~ Gaby, 1975
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PROCEDURE - DETECTION OF PARASITES IN COMPOST
Organisms Hookworms, Tapeworms, Wireworms
Ova and Cysts
Methodology
Preparation of Sample; Place compost (2 g) in flask (250 ml) containing
saline (20-30 ml) and glass beads to cover flask bottom. Shake to emul-
sify, tilt flask and allow sedimentation to occur.
(a) Direct mount
Prepare iodine mount using 0.05 ml of sediment for direct micro-
scopic examination.
(b) Brine flotation method
Mix suspension and strain through wire mesh funnel into centrifuge
tube (50 ml). Wash mesh with saline (15-25 ml). Centrifuge for 1
to 2 minutes at 2000 rpm. Decant supernatant and resuspend sedi-
ment in saline. (Save 10 ml for suspension for formalin-ether
method). Centrifuge remaining 10 ml as before, decant supernatant,
resuspend in brine. Transfer into shell vial, fill with brine to
lip and cover with slide. Avoid overflow and airpockets. After 15
minutes remove slide, fit with cover glass, seal edges with Vaspar
and examine microscopically.
(c) Formalin-ether sedimentation
Centrifuge 10 ml suspension from brine flotation method. Decant
supernatant. Add 10 ml of 10% formalin, mix and allow to stand for
5 minutes. Add ether (3 ml), shake for 30 seconds and centrifuge at
1500 rpm for 1 to 2 minutes. Four layers are formed. Decant top 3
layers and prepare an iodine mount from the bottom sediment.
Limitations or Precautions
Additional Comments
Reference: Gaby, 1975.
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PROCEDURE - ASSAY OF VIRUSES IN LEACHATE THROUGH SANDY SOIL
Organisms-Poliovirus type 1 (Chat)
Methodology ~~ " ~
Cell Culture; Grow HeLa cells on culture dishes (60 mm) containing Eagle
minimal essential medium, penicillin G (200 units/ml), streptomycin (16.6
units/ml), gentamicin (25 ug/ml) and Fungizone (0.5 ug/ml).
Virus Assay; Add 0.2 ml leachate to HeLa cell monolayers. Incubate at
37°C for 48 hours. Stain with 2% neutral red in Hanks balanced salt
solution for 2 to 3 hours. Count plaques, express findings in plaque
forming units/ml.
Limitations or Precautions
Assay samples within 24 hours after collection.
Additional Comments
In Duboise study, poliovirus was eluted from soil samples (5 g) with
tryptose phosphate broth by vortexing energetically for 30 seconds. The
eluates were centrifuged at 12,000Xg for 10 minutes and the supernatant
was assayed as described above.
Reference:Duboise et al, 1976^
PROCEDURE - PREPARATION OF CELL CULTURES FOR VIRAL ANALYSIS
Organisms
Poliovirus type 1 (field & lab strain)
Echovirus type 2 (field & lab strain)
Methodology
Grow BSC 1 cells in Eagle minimum essential medium (I) with 10% fetal
calf serum, 0.08% NaHCO , streptomycin (100 ug/ml) and pencillin (100
units/ml). Maintain cells in I containing 2% fetal calf serum, 0.12%
NaHC03, streptomycin (100 ug/ml) and penicillin (100 units/ml). Grow
baboon kidney cells as described by Melnick and Werner (1969).
Limitations or Precautions
Additional Comments
BSC 1 cells are a continuous line derived from African green monkey
kidney cells. Glotzbecker and Novello (1975) added EDTA to the cell
culture inoculum prior to plaque assay.
Reference: ~~~Sobsey et al., 1975
Glotzbecker and Novello, 1975
89
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PROCEDURE - PREPARATION OF CELL CULTURES FOR VIRAL ASSAY
(ALTERNATIVE CULTURE)
OrganismsPoliovirus I
Methodology
Cell Culture: Grow the HeLa cells in monolayers or minimum essential
medium containing fetal calf serum (5-10%), penicillin (100 units/ml) and
streptomycin (100 ug/ml). Disperse cells in 0.02% EDTA (10 ml volumes)
in Ca2+ and Mg2+ free phosphate buffered saline. Centrifuge for 5 minutes
at 1000 g. Resuspend cells in growth medium (cone. 5 x 10^ cells/ml).
Inoculation to bottles for plaque assay (50 ml aliquots in 32 oz pres-
cription bottles, 8 ml in 3 oz, 4 ml in 1 oz). Monolayers form after 3
to 4 days incubation at 37°C.
Limitations or Precautions
Additional Comments
Reference:Cooper et al., 1974.
PROCEDURE - ASSAY OF VIRUSES - PLAQUE TECHNIQUE
Organisms Poliovirus I
Methodology
Pour aliquots of leachage onto drained cell sheets in 32 oz bottles.
Leave to adsorb at 31°C for 45-60 minutes. Pour off sample and spread
overlay medium (50 ml) onto cell sheets. Overlay medium is 1.5% agar
(Difco), 3% gamma globulin free PCS, MgCl2 (25 mM), DEAF-dextran (0.02%),
NaHC03 (0.15%) in MEM without phenol red. After agar hardened, invert
medium and incubate 2 days at 37°C. Stain for counting by adding 3.5 ml
for 0.08% neutral red. Count after 4 hours expressing result as plaque
forming units/100 ml.
Limitations or Precautions
Additional Comments
Freezing samples containing viruses prior to concentration adversely
affected viral recovery in Cooper's study.
Reference:Cooper et al., 1974a.
90
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PROCEDURE - ASSAY OF VIRUSES - TISSUE CULTURE TECHNIQUE
Organisms Poliovirus type 1 (field and lab strains)
Echovirus type 7 (field and lab strains)
Methodology
Make leachate isotonic and purify by membrane filtration (0.22 urn poro-
sity nitrocellulose filter pretreated with Tween 80 to prevent virus
adsorption). Dilute 1:4 in maintenance medium described previously.
Inoculate into 1 or 16 oz bottles of BSC-1 cells. Incubate at 37°C
examining for cytopathic effects over 10 days. Filter samples of cell
lysate showing cytopathic effects through 0.22/urn porosity cellulose
ester filter (treated with Tween 80). Identify viruses serologically.
Estimate viral count from total sample volume inoculated and fraction of
bottles with cytopathic effects due to each virus.
Limitations or Precautions
Additional Comments
Sobsey et_ al. (1975) also used plaque techniques for small sample volumes
(0.2 ml sample in 1 oz bottle of BSC-1 monolayers).
Reference: Sobsey et al., 1975
91
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100
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APPENDIX A
HEALTH ASPECTS OF SOLID WASTE DISPOSAL
In a study of digested sludge, Palfi (1973) found that approximately 8%
of all samples analyzed contained poliovirus type 3 within weeks of a local
immunization campaign. Poliovirus type 3 and echovirus type 2 were found in
11% of all fecally stained diapers examined by Peterson (1974). There exists
the possibility that live attenuated viruses used in immunization programs
(e.g., the Sabin polio vaccine) may revert back to virulent wild virus strains
in the environment (Melnick, 1960).
Live strains of virus for vaccination are obtained by laboratory manipula-
tion of wild strains to increase the ratio of attenuated to virulent particles
(Melnick, 1960). The attenuated particles, which are selected from the mixture,
still cause the antigen/antibody formation necessary to protect from virulent
strains, but do not produce the disease. The effectiveness of any live
attenuated poliovirus vaccination program depends on the genetic stability of
the non-virulent vaccine. In vitro tissue culture markers are used to
distinguish between attenuated and virulent strains. For example, viruses
processing the d+ marker grow more rapidly than d- viruses at low bicarbonate
concentrations in agar. MS+ viruses grow more rapidly than MS- strains on
monkey stable kidney cells. T+ strains grow more readily at 40°C than T-
strains. Generally, the virulent wild polio viruses possess d+, MS+ and T+
markers as opposed to the d-, MS~P T- highly attenuated strains.
Melnick (1960) showed that a significant proportion of vaccinated children
(Sabin's attenuated poliovirus types 1, 2, and 3) excreted viruses which had
reverted to wild types. He found that d-T- markers reverted to d+T+ in 19%
of the children vaccinated, and that d-T- reverted to d+T- in 54% of the
children. Peterson (1974) also detected wild strains of poliovirus in her
examination of fecally contaminated disposable diapers found in MSW. This
indicates that either wild polio strains were circulating in the area, or at-
tenuated vaccine strains reverted in the wild. Upon repeated human passage,
these strains may increase in neurovirulence and attack unprotected members
of the community (Melnick, 1960; Peterson, 1974).
Various pathogenic bacteria have also been isolated from municipal solid
waste. For example, Salmonella sp. was isolated from refuse by both Spino
(1971), and Gaby (1975). Salmonella species are the most common cause of
acute food poisoning in man, and outbreaks of typhoid and paratyphoid fevers
have been traced to salmonella organisms. In the United States in 1970,
there were approximately 24,000 reported human cases of salmonellosis. Many
more cases are not reported or not diagnosed. It has been estimated that
there are at least two million cases per annum in this country alone.
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There are over 1,000 distinct serotypes, all of which are pathogenic to
man and/or animals. S. typhimurium is the most widespread, and infects both
man and animals. Infected cattle may excrete 10 million microorganisms per
gram of feces (Diesch, 1973). Salmonella contaminated manure may erode from
feedlots into streams and rivers, where it may infect fish, mollusks, and
other wild animals. The organisms may also be air-transmitted in dust.
Shigellosis (bacillary dysentary) is an acute bowel infection characterized
by gastrointestinal cramps, fever, and diarrhea. The organisms are excreted
by infected individuals and animals, and may be disseminated by fecal pollution
of the water supply; aerosol transmission; transfer of bacilli to flies; and
the handling of food by infected workers.
Leptospirosis (Weil's disease, spirochetal jaundice) is a widespread zoon-
osis caused by a variety of serotypes of the genus Leptospira. Leptospires
are shed in the urine of infected animals (average concentration 1 x lO^/ml)
for periods of several months. The organisms may live in the environment for
several weeks. L. icterohemorrhagiae, L. pomona, and L. canicola are the
commonest strains found in this country"It is associated with poor manage-
ment of animal wastes rather than MSW.
The disease may be transmitted to men and animals through ingestion of
contaminated food and water or by inoculation through broken skin. There
have been "several" reported outbreaks in this country as a result of
swimming in contaminated water (Diesch and McCullough, 1966). Certain
occupational groups are more exposed to the disease and, hence, have a higher
than average incidence of leptospirosis. These groups include farmers, sewer
men, abattoir workers, rat-catchers, and veterinarians.
Brucellosis is also associated with the above occupations and the poor
management of infected wastes. Brucella abortus commonly infects cattle and
hogs, and is found in the abortus of infected animals; Br. suis attacks hogs.
The disease is transmitted to man by direct contact, or by ingestion of in-
fected milk. It has been reported that the organisms have survived in feces
at 80°C for a year, though they are destroyed with a few hours of exposure to
direct sunlight (Stableforth, 1959).
Human and animal parasitic ova and cysts may also be found in slurries
and in MSW as a result of fecal contamination (Gaby, 1975). Nematodes such
as Ascaris lumbricoides, Tricuris trichium, and Trichostrongylus sp. may
cause toxocariasis in humans. Ingestion of nematode ova by a child may
result in ocular toxocariasis with retinal glaucoma (Powell, 1974). Protozoa
such as Entamoeba histolytica, Entamoeba coli, and Giardia Iambiia cause
amebiasis, a colitis characterized by passage of bloody mucoid stools.
As stated previously, there have been studies linking disease outbreaks
to contamination of water supplies by sewage sludge and animal slurries
(Powell, 1974). It should again be emphasized that there is not one sound
epidemiological study correlating an outbreak of any infectious disease in
this country with the pathogen content of municipal waste.
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APPENDIX B
HOSPITAL WASTE
Some investigators believe that the pathogenic organisms found in hos-
pital waste differ from those present in MSW only in their concentrations.
Others think that hospital wastes are much more dangerous due to their
"infectious" nature (Ross Hoffmann Associates, 1974a, 1974b). Research has
indicated that up to 15% of raw hospital waste is "potentially infectious"
with from 2% to 8% containing pathogens. Staphylococcus aureus is the most
common pathogen, but the waste also contains signficant counts of streptococci,
coliforms, Candida albicans, and Pseudomonas sp. (Ross Hoffmann Associates,
1974a, 1974b). Airborne transmission of microorganisms is especially signifi-
cant in the hospital environment.
Considering the well-documented pathogenic nature of much hospital waste,
it is interesting to examine the methods of solid waste handling and disposal
used in hospitals. Most hospitals take special care in handling infectious
waste by double bagging in waxed or plastic waste bags. They may also color-
code the bags according to degree of hazard. These bags may be hand-carried
or chute-delivered to a central disposal area. Pneumatic systems for
transporting bagged waste have been associated with high concentrations of
pathogens due to broken bags, etc. Grieble et aU (1974) described one chute
hydropulping waste disposal system as a "reservoir of enteric bacilli and
Pseudomonas in a modern hospital."
After collection, disposal remains a problem. Iglar and Bond (1973) sur-
veyed over 100 hospitals for methods of disposing of all solid waste, includ-
ing biological material. Biological material included afterbirth, amputated
tissue, autopsy tissue, animal carcasses, and bacteriological cultures. In-
cineration was the preferred form of disposal, but some biological material
was hauled away with mixed solid waste usually to a landfill (see Table Bl)
Some hospitals autoclave biological wastes or treat them with formalin prior
to disposal. Some biological material (afterbirth) is used by drug firms for
experimental work. Some hospitals even disposed of untreated wastes in dumps,
or fed the garbage to hogs, both of which are illegal and environmentally
unacceptable practices.
Grinders have also been used in hospitals for treatment of biological
waste. Jopke and Hass (1968) reported that regardless of design, grinders
generate bacterial aerosols which, however, could be minimized with an
exhaust system. After grinding, the waste is discharged into the sewage
103
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system. The local municipal sewage facilities may have problems in handling
this heavy load of suspended solids.
Iglar and Bond confirmed the findings of previous researchers that
hospital incinerators are often poorly operated. The staff may not be
competent, incinerators are often overcharged, and they may be used only
periodically so that necessary kill temperatures are not achieved (see also
Section 4, this report). They also found that the necessity of compliance
with air pollution-particulate emission standards has apparently forced sev-
eral hospitals to abandon incineration.
It does appear from this very brief examination of the solid waste dis-
posal practices of the American hospital, that there are no special methods
used by hospitals to dispose of highly infectious wastes that are applicable
to the management of MSW. Similar problems seem to exist for both types of
waste. The most common method of treating hospital wastes is incineration,
and for a variety of reasons, reviewed previously, incineration is not always
an efficient method of destroying those pathogens present in municipal waste.
TABLE Bl
DISPOSITION OF SELECTED BIOLOGICAL MATERIALS
(Iglar and Bond, 1973)
% Hospitals (Full-Scale Stage)
Type of
Biological
Material
Inciner-
ation
On-Site Burial
Hauling Away Use by
with Other Drug
Waste Firm
Not
Appli-
Other cable*
Afterbirth 26
Amputated tissue 50
Autopsy tissue 31
Animal carcasses 15
Bacteriological
cultures 69
9
34
7
11
4
1
21
51
3
6
13
24
27
83
* No material of indicated type discarded.
Refers to tissue replaced in body.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO
EPA-600/8-80-034
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
A Survey of Pathogen Survival During Municipal Solid
Waste and Manure Treatment Processes
5. REPORT DATE
August 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Sylvia A. Ware
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Ebon Research Systems
1542 Ninth Street, N.W.
Washington, D.C. 20001
10. PROGRAM ELEMENT NO.
1DC618
11. CONTRACT/GRANT NO.
68-03-2460-5
12,^P£)JvlSQRLN_Q AQ.ENC_XN AME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final Research
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officers: Carlton C. Wiles and Laura A. Ringenbach (513) 684-7871
16. ABSTRACT
Municipal solid waste (MSW) and animal manures may contain microorganisms that can
cause disease in man and animals. These pathogenic microorganisms include enteric
bacteria, fungi, viruses, and human and animal parasites.
This report summarizes and discusses various research findings documenting the
extent of pathogen survival during MSW treatment. The technologies discussed are
composting, incineration, landfill, and anaerobic digestion. There is also a
limited examination of the use of the oxidation ditch as a means of animal manure
stabilization. High gradient magnetic separation (HGMS), and gamma radiation
sterilization are mentioned as future options, especially for animal waste
management. Several standard methods for the sampling, concentration, and
isolation of microorganisms from raw and treated solid waste are also summarized.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Microorganisms
Bacteria
Refuse Disposal
Viruses
Wastes
Manure
Compost
Incineration
Landfill
Samp!ing
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
115
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
105
1 U S GOVERNMENT PRINTING OFFICE 1<*SO -6 57 - 1 6 5/006 1
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