Risk of Infectious Disease from Use of
Sludge on Land and Methods to Reduce These Risks
(U.S.) Environmental Protection Agency
Cincinnati, OH
Feb 86
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PB86-166378
EPA/600/D-86/038
February 1986
RISK OF INFECTIOUS DISEASE FROM USE OF SLUDGE ON LAND
AND METHODS TO REDUCE THESE RISKS
0. 8. Farrell
Wastewater Research Division
Water Engineering Research Laboratory
Cincinnati, Ohio 45268
WATER ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 4£.?68
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TECHNICAL REPORT DATA
(Please read Instructions on the reverie before completing)
REPORT NO.
EPA/600/D-86/038
3. RECIPIENT'S ACCESSION NO.
lbfe378/AS
4. TITLE AND SUBTITLE
Risk of Infectious Disease from Use of Sludge on
Land and Methods to Reduce these Risks
5. REPORT DATE
February 1986
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
0. B. Parrel!
8.'PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Wastewater Research Division
Water Engineering Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Water Engineering Research Laboratory, Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Author: J. B. Far>"ell
513-569-7645
FTS 8-684-7645
16. ABSTRACT
Virtually all of the infectious organisms in wastewater end up in the
sludge removed in the course of wastewater treatment. The health risks to
humans when sludges are applied to land depend on the densities of these
organisms, reductions that occur when the sludge is processed, the hardiness
of the organisms on or in the land surfaces, and the available pathway: to
man. This presentation discusses each of these issues for pathogenic bacteria,
viruses, protozoa, and helminths. The combination of sludge processing require-
ments and other controls, such as control of access and type of crops growing,
. .used by the U.S. EPA in their regulations governing sludge use on land are
^ yresented and discussed.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (Tills Report)
Unclassified
21. NO. Of PAGES
15
20. SECURITY CLASS (Thi
Unclassified
22. PRICE
EPA Form 2220-1 (R»v. 4-77) PREVIOUS COITION is OBSOLETE
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse
ment or recommendation for use.
11
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RISK OF INFECTIOUS DISEASE FROM USE OF SLUDGE ON LAND
AND METHODS TO REDUCE THESE RISKS
by
J. B. Farrell
Wastewater from a community is extensively contaminated with organisms
that cause infectious disease. Primarily these are organisms that are dis-
charged through the intestinal tract. Modern drinking water and wastewater
systems are based on an appreciation of the high disease hazards present
in wastewater. The organisms of concern are: bacteria, viruses, protozoa,
and the eggs of helminths (parasitic worms). All of these materials,
even viruses, end up in high densities in the sludge. Viruses, although
very small, are highly adsorbed or contained in solids, so proportion
removed with sludge is very high.
The questions we must ask about these organisms are the following:
a) Are these organisms in sludge at infective levels?
b) Are they reduced adequately by treatment?
c) Are there pathways that could lead to infection in man?
d) Do the organism densities decline rapidly with time when
sludge is applied to land?
The first part of this presentation will discuss items a, c, and d
for each class of organisms in turn. Item b will be discussed briefly but
will be taken up in more detail later.
Bacteria
The pathogenic bacteria of major concern which are found in sludge are
listed in Table 1. Symptoms of diseases produced by these organisms are dis-
cussed elsewhere (ref. 1). These diseases are frequently serious and some-
times life-threatening. Densities of the causative bacteria are reduced
by conventional treatment. A substantial dose of pathogenic bacteria (many
thousands of CFU's-colony forming units—in some cases) is generally needed
to cause disease and frequently densities are low enough that ingestion of
an infectious dose seems unlikely. However, most of these bacteria can
regrow if provided with a nutritious substrate, so even low densities are
of concern in certain circumstances.
Pathways to man include aerosols, animals, crops, drinking water from
surface or groundwater sources, vectors, and fomites. Results in the
literature indicate that bacteria live on soil and crops long enough to be
of sustantial concern (see Table 2). The aerosol route seems to be a
minor hazard that can be minimized by good application techniques.
Bacteria are relatively large and are filtered by most soils, excepting
coarse sandy soil and thin soils over fissured bed rock. Surface runoff
is of concern, as is transmission by crops and livestock. Transmission
by vectors and fomites can be minimized by proper pretreatment of sludge
and by good housekeeping.
2/6/86
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Vi ruses
Human viruses commonly found in wastewater are presented in Table 3.
Symptoms of these diseases are discussed by Kowal (1).
Illnesses produced ranee from mild to extremely serious.
Pathways to man are similar to those for bacteria, and most concerns
about disease transmission are similar. Viruses survive about as long as
bacteria on soil and plants and may survive considerably longer when carried
deep into the soil. Transmission via animals is possible because some
animals can be infected by human viruses. However, this risk is unproven
and may be slight., Potential for transmission to groundwater is greater
than for bacteria. Viruses normally adsorb strongly to solids including
soil granules. However, a change in the ionic condition of water may
cause them to desorb. There have been reports of considerable movement
of viruses after a heavy rainfall.
Viruses cannot regrow outside of living organisms, so hazard of trans-
mission is reduced. On tiie other hand, infective dose for viruses can be
very low, so caution must still be exercised when sludge containing
vi ruses i s used.
Protozoa
Types of protozoa which may be found in wastewater and sludge are
shown in Table 4. According to Kowal (1), only three species are of
major significance for transmission of disease to humans through waste-
water: Entamoeba histolytica, Giardia Iambiia, and Balantidium coli.
These organisms are hazardous when they survive wastewater treatment.
All of these organisms are greatly reduced in densities by sludge treat-
ment processes and especially by exposure on the soil. Pathways to man
from sludge application by transport to surface or groundwater are not
considered significant. The primary protective factor is their short
life on the soil. Any measure imposed to protect against viruses and
bacteria will surely be protective against protozoa. These agents are
much more dangerous to humans when discharged with wastewater into a
receiving stream, primarily because they can reach a swimming area or a
drinking water source in a matter of hours after discharge.
Helminths
Pathogenic helminths of major concern are listed in Table 5. Reime^s
et al. (2, 3) have found Ascari s, Trichuri s, and Toxocara to be the most
frequently recovered helminth eggs in municipal sewage sludge in the
United States. Taenia saginata and T_. solium, the beef and pork tapeworm,
are relatively rare in the United States but are fairly common in some
areas of the world.
The pathways to man are slightly different for helminths than for
viruses ana bacteria. Because of the relatively large size of the eggs,
they are filtered by the soil, and it is highly unlikely that they will
reach or travel with groundwater. They are relatively high in density
and tend not to be carried to surface waters by runoff. On the other
hand, they are extremely resistant to ordinary environmental conditions
and some survive in the soil for periods exceeding a year. The soil can
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present a hazard long after any evidence of sludge use has disappeared.
They can be ingested by grazing animals, by humans who eat crops grown on
sludge amended soil, or by children with pica (an occasionally encountered
habit of some children to consume dirt while at play). Like viruses,
helminths and their eggs cannot multiply outside of their host. Their
infective dose is very low—generally one egg is sufficient to produce an
infection. Unless the infection is massive, which -is unlikely, the
illness produced is not severe. Any potential cycle of infection is to
be guarded against. Such occurrences can take place when vegetables
supplied to a city are grown on farms irrigated with the city's improperly
treated sewage. Then infections of nearly all the inhabitants of the
city becomes possible, and has occurred.
Reduction in Organism Density by Conventional Treatment
The conventional means of treatment of wastewater solids are the
wastewater treatment process itself, anaerobic digestion at 35°C, aerobic
digestion at ambient temperatures, lime treatment to pH 12, storage in
lagoons, and drying on sand beds. All of these processes produce sub-
stantial reductions in densities of bacterial and viral pathogens. For
example, the sludge solids from conventional treatment (primary treatment
followed by the activated sludge process) ha«e about one-tenth the density
of organisms of fecal origin as the incoming wastewater solids. Anaerobic
digestion produces an additional reduction of about the same magnitude.
However, there is substantial and measurable survival. The helminth eggs
are almost unaffected, perhaps reduced by half, by processing through
digestion or even lime treatment. Since sludge after conventional treat-
ment still contains pathogens, it is clear that some protection must be
provided when sludge is used on land to minimize risk to human health.
Further Processing That Disinfects Sludge
In some cases, sludges or their products are used under conditions
where human contact is substantial. In these cases, sludges should
contain no pathogenic organisms. There are three types of treatment
available: exposure to certain chemicals, high energy radiation, or to
temperature in excess of 55°C (time of exposure depends on temperature).
All three of these treatments eliminate pathogenic bacteria and viruses;
unfortunately, helminth eggs are extremely resistant to chemical treat-
ment. Consequently, only high energy radiation or exposure to tempera-
tures above 55°C reliably destroys all three classes of organisms of
concern. The processes available that provide these treatments are:
composting when temperatures exceed 55°c
thermophilic anaerobic digestion (> 55°C)
thermophilic aerobic digestion (> 55°C)
pasteurization
gamma ray irradiation using radioactive isotopes
electron beam irradiation
Processing conditions found acceptable to the U. S. EPA are presented in
their regulations which *re attached (See Appendix II B of "Part 257-Criteria
for Classification of Solid Waste Disposal Facilities and Practices," which
is attached). Thermophi]ic anaerobic digestion is not in the EPA listing of
acceptable processes, primarily because there was no experience in the United
States with this process above 49°C. Recent research experience indicates that
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55°C can be achieved. Under this circumstance, thermophilic anaerobic digestion
will qualify as a suitable process to disinfect sludge. Another process that
may eventually qualify is long term storage (in excess of two years) of sludge
in lagoons in warm climates. EPA research not yet published indicates promising
results.
EPA's Control Approach
EPA's approach to control of risk of infectious disease from sludge
utilization is contained in Paragraph 257.3-6 in the attached regulation.
EPA divided sludaa use into three classes:
a) If sludge is not treated after removal from the wastewater
processing step, it can not be used on the land surface.
b) If sludge is treated by certain processes such as anaerobic
digestion at 35°C for 15 days, or lime treatment to pH 12, it
can be used on the soil surface under certain restrictions.
The restrictions require controlled access for 12 months after
use of sludge, crops for direct human consumption that can touch
the sludge can not be grown for 18 months, and grazing of animals
whose products are consumed by humans can not occur until one
month after sludge application.
c) If sludge is treated by a process that disinfects it and
reduces attraction of vectors, it can be used on the soil
surface with no restrictions related to transmission of
infectious disease.
These regulations are being considered for revision by EPA, with a
proposed revision due to be published in September of 1986. The basic ideas
noted above are thought to be sound and will probably form the structure of
the new regulation, although numerous minor changes are anticipated.
(1 ) Kowal , N.
78 pages,
REFERENCES
E., "Health Effects of Land Application of Municipal Sludge,"
EPA-600/1-85/015, September 1985.
(2) Reimers, R. S., Little, M. D., Englande, A. J., Leftwich, D. B.,
Bowman, D. C., and Wilkinson, R. F., 1981. "Investigation of Parasites
in Southern Sludges and Disinfection by Standard Sludge Treatment
Processes." EPA-600/2-81-166, U. S. Environmental Protection Agency,
Cincinnati, Ohio.
(3) Reimers, R. S., Little, M.D., Englande, A. J., McDonnell, D. B.,
Bowman, D. D., and Hughes, J. M., 1984. "Investigation of Parasites
in Sludges and Disinfection Techniques," U. S. Environmental Pro-
tection Agency, Cincinnati, Ohio.
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Table 1. Pathogenic Bacteria of Major Concern
Name
Nonhuman Reservoir
Campylobacter jejuni
Escherichia colt (pathogenic strains)
Leptospira spp.
Salmonella paratyphi A, B. C'
Salmonella typhi
Salmonella spp.
Shigella sonnei. S. flexneri.
S. boydii. S. dysenteriae
Vibrio cholerae
Yersinia enterocolitica.
Y. pseudotuberculosis
Cattle, dogs, cats, poultry
Domestic and wild mammals, rats
Domestic and wild mammals, birds,
turtles
Wild and domestic birds and mammals
'Correct nomenclature: Salmonella paratyphi A, S. schottmuelleri. S. hirsch-
feldi, respectively.
Source: Table 2 in Reference 1.
Table 2. Survival Times of Pathogens on Soil and Plants
Soil
Plants
Pathogen
Bacteria
Viruses
Protozoa
Helminths
Absolute
Maximum
1 year
6 months
10 days
7 years
Common
Maximum
2 months
3 months
2 days
2 years
Absolute
Maximum
6 months
2 months
5 days
5 months
Common
Maximum
1 month
1 month
2 days
1 month
Source: Table 1 in Reference 1.
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Table 3. Human Wastewater Viruses
Enteroviruses
Poliovirus
Coxsackievirus A
. Coxsackievirus B
Echovirus
New Enteroviruses
Hepatitis A Virus
Rotavirus ("Duovirus," "Reovirus-like Agent")
Norwalk-Like Agents (Norwalk, Hawaii, Montgomery County, etc.)
Adenovirus
Reovirus
Papovavirus
Astrovirus
Calicivirus
Coronavirus-Like Particles
Source: Table 10 in Reference 1.
Table 4. Type* of Protozoa in Wastewater
Name
Protozoan Class
Nonhuman Reservoir
HUMAN PATHOGENS
Enlamoeba histo/ytica
Giardia lamblia
Balantidium coli
Toxoplasma gondii
Dientamoeba fragi/is
Isnspora bell!
I. hominis
HUMAN COMMENSALS
Endolimax nana
Entamoeba coli
lodamoeba butschlii
ANIMAL PATHOGENS
Eimeria spp.
Enlamoeha spp.
Ameba
Flagellate
Ciliate
Sporozoan (Coccidia)
Ameba
Sporozoan (Coccidia)
Sporozoan (Coccidia)
Ameba
Ameba
Ameba
Isospora spp.
Sporozoan (Coccidia)
Ameba
Flagellate
Sporozoan (Coccidia)
Domestic and wild
mammals
Beavers, dogs, sheep
Pigs, other mammals
Cats
Fish, birds, mammals
Rodents, etc.
Dogs, cats, wild mammals
Dogs, cats
Source: Table 15 in Reference 1.
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Tabl e 5 . Pathogenic Helminths of Major Concern
Pathogen Common Name
NEMATODES (Roundwcrms)
Enterobius Pinworm
vermicularis
Ascaris Ftoundworm
lumbricoides
A. suum Swine
roundworm
Trichuris trichiura Whipworm
Necator americanusHookworm
Ancylostoma Hookworm
duodenale
A. braziliense Cat hookworm
A. caninum Dog hookworm
Strongyloides Threadworm
stercoralis
Toxocara cam's Dog roundworm
T. cati Cat roundworm
Nonhuman
Disease Reservoir
Enterobiasis
Ascariasis
Ascariasis Pig*
Trichuriasis
Necatoriasis
Ancylostomiasis
Cutaneous larva Cat, dog*
migrans
Cutaneous larva Dog*
migrans
Strongyloidiasis Dog
Visceral larva Dog*
migrans
Visceral larva Cat*
migrans
CESTODES (Tapeworms)
Taenia saginata" Beef tapeworm
T. solium Pork tapeworm
Hymeno/epis nana Dwarf tapeworm
Echinococcus Dog tapeworm
granulosus
£. multilocularis
Taeniasis
Taeniasis, Cysticerosis
Taeniasis Rat, mouse
Dog*
Unilocular hydatid
disease
Alveolar hydatid
disease
Dog, fox,
cat*
"Definitive host; man only incidentally infested.
"Eggs not infective for man.
Source: Table 17 in Reference 1.
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