There are many different kinds of victims of sludge.
Although we never suffered as much physical harm as the Zanders
from land application of sludge, we nevertheless were victims
because our property was contaminated with Salmonella and E.
coli! We are trustees for a farm surrounded on three sides by
Kansas City, Missouri's 1200 acre sewage sludge application
site. For ten years we have suspected there might be a
problem with toxic contaminated surface water run-off from
the site which collects on the property.
On May 6, 1998, James Macy, Regional Director of the
Missouri Department of Natural Resources, called a meeting
with Kansas City's Sludge Manager, John Bozarth, and EPA's
Regional Sludge Coordinator, John Dunn, to evaluate our
concerns over the potential contamination of the farm, since
there was documented ground water contamination at the
property line. The ground water contamination under the
sludge disposal site included fecal coliform, aluminum and
nitrogen. Arsenic had also been a ground water contaminate
in one area of the sludge disposal site. Both the City and
EPA agreed to do comparison ground water testing on the Trust
property as well as soil testing for the nine toxic
"regulated" metals, aluminum, thallium and pathogenic disease
organisms. Two months after the meeting, the City and EPA
backed out of the testing agreement and Kansas City fired
its Sludge Manager. As an honorable man, Macy, who had given
his word that the tests would be done, committed the State to
do the soil test for toxic metals, since the State could not
force either the City or EPA to comply with the agreement
made in May. When the City and EPA refused to do the testing
they had committed too, we decided since the State was only
going to do the metals test, we would do the soil testing for
pathogens.
The first immediate problem we had to overcome was to
find a laboratory to do the tests. There was no laboratory
in Kansas City that could or would do the actual testing for
us because of conflicts of interest. The only laboratory we
could find within 150 miles of Kansas City that would do the
testing only had the capability of testing for fecal coliform
and the pathogenic disease organisms Salmonella, E. coli and
fecal streptococci. If the laboratory had known the purpose
of the tests, there would have also been a conflict of
interest, since the laboratory does sludge testing for a
number of small community sewage treatment plants.
On the evening of August 16, 1998 the ALICE MINTER TRUST
collected four soil samples from its farm and an access right
of way where toxic comtamination was suspected. The times,
date and location were documented by photographs. The
following morning the samples were delivered to the
laboratory.
No sludge or manure has ever been applied on our farm
and no sludge had been applied to the City of Kansas City's
sludge disposal drainage area for almost a year, so we were
shocked by two of the test reports which revealed both
Salmonella and E. coli at a little less than 800,000 COL/100
ML. That is 800,000 colony forming units of each bacteria per
100 grams of soil! EPA claims it will allow no more than 75
Salmonella bacteria per 100 GRAMS in Class A sludge
fertilizer. There is no standard for E. coli in sludge or
soil.
What was more amazing was that the tests revealed fecal
coliform bacteria at a level of 650,000 per 100 ML of soil on
our farm roadway where the City claimed it has not applied
any sludge since 1991. According to EPA, the safe level of
fecal coliform in sludge for public contact sites is 1000 per
gram of sludge.
A fourth test comparing fecal coliform at 50,000 colony
forming units to fecal streptococci at 10,000 colony forming
units (4.4 to 1 ratio) revealed that the toxic contamination
in the soil was from human waste.
We were astounded by the Salomella and E. coli numbers
because for the past 10 years EPA and USDA have claimed
infectious pathogenic disease organisms were destroyed either
in the sewage treatment process for Class A sludge or within
30 days after application for Class B sludge. EPA claims
there are no pathogenic disease organisms in unregulated
Class A sludge for use on home lawns and gardens when the
fecal coliform level is less than 1000 per gram in sludge. In
this case the fecal coliform levels was 30 and 90 per gram of
soil vs 8000 units of Salmonella and E. coli per gram of
soil.
When the laboratory report was sent to one of the major
sludge product producers, J. Patrick Nicholson, CEO of N-
Viro International, his reaction was that the Trust must be
using chicken manure as a fertilizer on the farm. According
to Mr. Nicholson, the use of chicken manure was the only
thing which would account for the high Salmonella numbers.
Although manure is being blamed for the rise in both
foodborne and waterborne diseases, the results from these
pathogen tests clearly indicate that sludge could be the
culprit instead of animal manure.
The 1998 Certified laboratory's test reports show that
not only will bacteria survive the treatment process, but it
will survive for long periods of time in the soil. Bacteria
will also leave the sludge disposal site in surface water
run-off and it will regrow in the soil. This is not some
startling new evidence. In a letter dated April 6, 1998, Rob
Atwill, a professor with the School of Veterinary Medicine,
University of California-Davis writes of the danger of
pathogens in sludge:
We veterinarians are all too aware of the ability of
trucks and our own boots to move pathogens between
locations. Large numbers of wildlife, particularly
birds, such as flocks of blackbirds or cowbirds, can
quickly transmit pathogens between a nearby field and a
dairy. Application of biosolids [sludge] to animal
forage crops such as alfalfa can likewise expose our
food animals to human pathogens. Animal consumption of
water contaminated with sewage discharges has been
associated with Salmonella being transmitted from humans
to poultry in Southern California. The incident resulted
in a large outbreak investigation by the California
Department of Health Services, California Veterinary
Diagnostic Laboratory System, and the California
Department of Food and Agriculture.
Professor Atwill warns, "In addition, many of these
pathogens can be transmitted to livestock, such as dairy and
beef cattle. These pathogens can replicate in our livestock
populations and become a meat-borne or milk-borne human
health risk."
D. Strauch in his 1991 paper, "Survial of pathogenic
micro-organisms and parasite in extreta, manure and sewage
sludge" reported that two groups of researchers had found
that pathogenic disease organisms will be taken up inside the
food crops. In other words, it will do little good to wash
the outside of fresh vegetables and fruit when the pathogenic
bacteria, viruses and worms from the sludge can be inside the
plant. Strauch concluded in his report that, "In any case,
the agricultural utilization of hygienically dubious sewage
sludge poses a risk for the whole national economy."
The Trust's laboratory test results revealed that EPA
and USDA lied to us when they claimed all the pathogenic
disease organisms would be destroyed in the soil within 30
days. According to D. Strauch, who is with the Institute of
Animal Medicine and Hygiene, University of Hohenhiem, this is
not the case. Salmonella has survived in forest stands
between 424 and 820 days. It appears that in spite of EPA
claims to the contrary not only is it not safe to harvest any
food or feed crops 30 days after sludge has been used, it's
not safe to grow crops on pollutant contaminated soil a year
after sludge has been applied.
Both animal manure from confined animal feeding
operations (CAFO's) and sewage sludge used as a fertilizer
can cause serious damage to human health and the environment
and can cause foodborne and waterborne diseases if not
properly managed. Could it be a mere coincidence that after
the final Part 503 sludge rule was released promoting the
widespread land application of sludge in 1993, that there was
a dramatic increase of bacterial food poisoning by Salmonella
and E. coli, from 6.5 MILLION INCIDENTS in 1994 TO 80
MILLION INCIDENTS in 1996?
In May 1996, Ralph J. Touch, Chief Sanitarian for the
U.S Public Health Service reported in his "Emerging
Infectious Diseases" Paper that the Centers for Disease
Control said that bacterial food posioning affects as many as
80 MILLION PEOPLE ANNUALLY.
Yet, in May 1997, the six federal agencies responsibile
for food safety which includes the FDA, CDC, USDA and EPA
reported to the President in "FOOD SAFETY FROM FARM TO TABLE,
A NATIONAL FOOD-SAFETY INITIATIVE" that there were only
between 6.5 and 33 million food related illnesses in the
United States each year. It would appear that the CDC forgot
to use its current data in the report, since the numbers
quoted by these government enforcement agencies, who are all
promoting the use of sludge as a fertilizer, were from 1994
figures.
EPA now wants Congress to create a separate law
controlling manure which appears to be aimed at dairy farmers
opposed to sludge use. EPA has even funded a lobbying
campaign through the WEF. They claim the pathogenic
organisms in animal manure are causing people to become ill
when exposed to it, especially in contaminated water. At the
same time, the agency has removed its sludge disposal
marketing program from all safety provisons of the
environmental laws.
Pathogenic disease organisms in sludge can pose a public
health risk when humans come in contact with them through
breathing contaminated air, drinking contaminated water,
eating contaminated food, and playing or working in
contaminated soil. Although EPA recognizes the danger from
exposure to pathogens in sludge, it claims both its
unrestricted Class A (used on home lawn and gardens), and
semi-restricted Class B sludge products (used on food crop
production land) are completely safe when they comply with
the pathogen reduction requirements of the Part 503 Sludge
Use and Disposal Standard.
The first requirement for heat dried, sanitized or
composted Class A pathogen reduction is that the sludge must
meet either the density requirements for the indicator
organism, fecal coliform, which must be less than 1,000 most
probable number (MPN) per gram total solids (dry-weight
basis) or Salmonella sp. which must be less that 3 MPN per 4
grams of total solids (dry-weight basis) when the sludge is
used or disposed or prepared for sale or give-away. EPA
concluded that fecal coliform bacteria could be used to
indicate the presence of other pathogenic organisms in the
sewage sludge. The fecal coliform was selected because an
analytical method existed for it, it was cheap and because
POTWs routinely conduct fecal coliform analyses. Class B
sludge products must meet the requirements for fecal coliform
density of less than 2 million MPNs per gram per total
solids.
Fecal Coliform Test
Pathogen reduction does not mean pathogen elimination.
It only takes a very few of some of the deadly bacteria and
emerging viruses to cause disease and death. Although the
EPA asserts that the fecal coliform tests or Salmonella sp.
tests for pathogens and the pathogen reduction alternatives
ensure that pathogen levels in sludge products either Class A
or Class B are reduced to levels considered safe to be
applied to land, some microbiologists have questioned this
contention.
Gerba and Rose cite a study by Clarke and Kabler (1964)
where "as early as 1960 there was concern that coliform
bacterial standards used to detect domestic pollution were
not adequate in regard to viruses" (p.394). According to
these researchers, viruses are more resistant to inactivation
and removal by treatment processes than the coliform bacteria
and can survive in the environment for longer periods of time
than the bacteria. They give examples from reports in the
literature of where viruses have even been isolated from
drinking water meeting U.S. bacteriological standards. They
state:
These reports have initiated concerns in regards to the
adequacy of the standards and guidelines governing the
hygienic quality of potable waters. Water which was
presumed to be safe based on currently used coliform
standards should not be assumed to be free of viruses."
Dr. Aaron Margolin, a microbiologist, certified in virus
and protozoa, from the University of New Hampshire is
critical of the fecal coliform tests. He says:
Throughout the literature--it is permeated with many
examples--my own labs being one--time and time again
where bacteria are inadequate indicators or predictors
of the presence and/or absence of these other infectious
organisms, viruses and intestinal parasites...while
someone may be able to tell you what the fecal coliform
levels are of the sludges--that is well and good and I
don't doubt that the levels are what they are saying
they are--but that does not necessarily or adequately
predict what the other pathogens in the sludge are.
(p. 2)
Twenty-three years before, in 1974, Gerald Berg, Chief,
Biological Methods Branch of the EPA's National Environmental
Research Center in Cincinnati, Ohio warned of the inadequacy
of the fecal coliform test. He stated:
For some time we have been aware that fecal coliforms
are not always reliable indicators for viruses and that
neither fecal coliforms nor other bacteria are inviolate
indicators of fecal pollution. To be sure, fecal
coliforms indicate a sanitary hazard, but certain other
bacteria may seem to be fecal coliforms in the standard
membrane filter test. Moreover, fecal coliform may
multiply in waters where pathogenic bacteria and
certainly viruses cannot. And fecal coliforms may be
destroyed in waters polluted with certain industrial
wastes--wastes that do not seem to affect fecal
streptococci and may not affect viruses either. Clearly,
it is a matter of some importance to develop a bacterial
indicator system that can definitively differentiate
fecal organisms from free-living forms. (p. xii)
Salmonella Test
The effectiveness of the Salmonella sp. test has also
been questioned by microbiologists. In 1995,
when William Yanko, Laboratory Supervisor, Alan Walker,
James Jackson, Leticia Libao, and April Garcia, staff
scientists in the CSDLAC Microbiology Laboratory, conducted a
study to evaluate the Part 503 Salmonella methods and two
other Salmonella methods previously developed to test sludge
and composts, they found the other methods were superior to
the 503 methods. They undertook the study because as they
stated in the report "the designation of specific Salmonella
methods in the 503 regulations has essentially established
standard testing protocols without documenting the validity
or suitability of the cited methods for the intended
purpose". (p. 369)
In their study, these scientists analyzed ten samples
each of activated sludge, anaerobically digested sludge, and
compost using the different Salmonella methods. Statistical
analysis indicated that there was a significant difference
between the methods, with the two methods that had been
developed for testing sludge recovering significantly more
Salmonella than the 503 methods. One 503 method failed to
detect Salmonella in 43% of the samples containing
Salmonella. Based on their findings the scientists suggest
"that a thorough evaluation of methods using a
multilaboratory round-robin format should be conducted to
establish appropriate methods for Salmonella compliance
testing." (p. 389)
The National Research Council also criticizes the 503
Salmonella methods. They state that because of the small
sample size and interference by a large number of
nonsalmonella bacteria the Part 503 Salmonella method is "apt
to underestimate the number present in any given sludge
sample" (p. 122)
The density of fecal coliform or Salmonella in the
sludge must be met for all six of the Class A pathogen
alternatives. The reason for these requirements is stated by
Walker, Knight, Stein, (1994), "Perhaps the most significant
of the requirements is to avoid regrowth of bacteria as
indicated by the results of a fecal coliform or Salmonella
test." (p. 111)
As the reliability of these tests in detecting pathogens
in both Class A and Class B sludge has been called into
question by some scientists, there is a real danger of
undetected regrowth of Salmonella. Although the EPA claims
that any one of the six alternatives for Class A pathogen
reduction will prevent regrowth of Salmonella, an EPA-
sponsored survey of distribution and marketed sludges in the
U. S. (Yanko 1987) found that Salmonella was often present in
PFRP-treated sludges and sludge products (13) (high-
temperature composting, heat-drying, heat treatment, and
thermophilic aerobic digestion). The conclusion of the author
was that the occurrence of pathogenic bacteria in distributed
and marketed sludge products represented a potential health
hazard, but the extent of the health risk was unknown.
In 1994, Constantine Skanavis and William Yanko
conducted a study of composted sewage sludge based soil
amendments for potential risks of salmonellosis. They
analyzed samples of composted sewage sludge, amendment
materials added to the compost (bulking agents such as aged
redwood, fir bark, redwood chips, rice hulls, and sawdust)
and four bagged commercial sludge soil conditioner products
representing different blends of materials for home garden
use. These bagged products were designated Product A
(recycled compost), Product B (made with rice hulls), Product
C (made with wood chips) and Product D (made by modifying
sludge with the addition of the company's proprietary
formulation).
All samples were tested for total and fecal coliforms
and the presence of Salmonella. The average total and fecal
coliform concentrations were significantly lower in the
composted sludge compared to the four compost-based products.
Although there were no significant differences in total and
fecal coliform concentrations among products A, B, and C, the
average total and fecal concentrations in Product D were
significantly higher than in A,B,C products and the bulking
agents. Laboratory tests detected salmonella in the compost-
based products but not in the compost material used to make
the products. Thirty-six percent of Product D samples were
positive for Salmonella. Product D also contained the highest
average concentration of Salmonella. Product A was second
with 27 percent and Products B and C were tied with 22
percents of the samples positive for Salmonella. Because
Salmonella was detected in the sludge products but not in the
compost, the authors retested (using another testing
procedure) four samples that had been negative for
Salmonella. Retesting resulted in detection of Salmonella in
2 of the 4 compost samples. The authors conclude that
"compost-based products could, in specific situations,
represent a source of Salmonella infection. This study,
therefore, points to the need for intensive study of the
factors associated with Salmonella spp. regrowth." (p. 9)
Enteric Viruses
Salmonella is not the only threat to public health.
According to Dr. Margolin, enteric viruses also pose a
danger. He says:
Enteric viruses are so small and have characteristics
that are very unique to only themselves. One of these
characteristics is that when complexed with organic
material and/or particulate material--given the right
temperature...conditions are extremely ripe for the long
survivability of viruses in sludges...and because of
their characteristics--the way they act as particles--
that with the high water table, it makes a perfect
situation for the transport of these infectious agents
from the sludge into the underground aquifers, (p. 2)
In a meeting of Milton, New Hampshire Board of Selectmen
on September 29, 1997, Dr. Margolin told Dr. Bolton
concerning land application of sludge that if the sludge
application was allowed he would put in a proposal to come
back and study their town again. "Because I think it would be
a neat little experiment--especially to actually see what the
end results are--because in the lab--the lab data would tell
us you would wind up being exposed to pathogens." (p. 11)
EPA's Part 503 pathogen reduction requirements for Class
A sludge products have been met if pathogens are below
detectable limits. Just because they are undetectable does
not make them safe. Gerba and Rose in their report on enteric
viruses in drinking water state:
Thus, viruses may be present in numbers below the
detection limits of the methods. The significance of low
levels of contamination can be exemplified by the low
infectious dose of viruses. Studies on minimum
infectious dose (i.e., that dose which causes infection
in 1% of the exposed population) indicates that as few
as 1 to 2 tissue-culture plaque-forming-units of enteric
viruses are capable of causing infection (Ward and Akin,
1984; Ward et al., 1986)
Risks from Pathogens
When Straub, Pepper and Gerba (1993) reviewed the
literature to assess the microbial (bacteria, viruses and
parasites) risks associated with application of sludge to
agricultural land, they found that "despite a 1-2 log 10
decrease in bacterial and viral number, significant
concentrations of these pathogens persist after sludge
treatment (Pepper and Gerba 1989; Soares 1990)." (p. 70)
Furthermore, most methods used in the detection of pathogens
were not 100% efficient and concentrations were always
underestimated. They also discovered that methods did not
exist for the detection of all pathogens that the sludges
could contain. They stated that "It would not be
unreasonable to suggest that the actual concentrations of
enteric viruses are 10-100 times the number observed
experimentally". (p. 81)
In their summary of the review of the literature,
Straub, Pepper, and Gerba state the various risks found to
public health from the microorganisms in the sludge applied
to the land:
This becomes a public health concern because the
infectious dose for some of these pathogens may be as
low as 1 particle (virus) to 50 organisms (Giardia).
When sludge is applied to land for agricultural use and
landfill compost, these pathogens can survive from days
(bacteria) to months (viruses) to years (helminth eggs),
depending on environmental conditions. Shallow aquifers
can become contaminated with pathogens from sludge and
depending on groundwater flow, these organisms may
travel significant distances from the disposal site.
Communities that rely on groundwater for domestic use
can become exposed to these pathogens, leading to a
potential disease outbreak. Currently, methods to
determine the risk of disease from pathogens in land-
disposed sludge are inadequate because the sensitivity
of pathogen detection is poor. (p. 85)
Emerging New Pathogens
Of particular worry to microbiologists are the emerging
new pathogens. The Institute of Medicine published a report
in 1992 entitled Emerging Infections: Microbial Threats to
Health in the United States in which they defined emerging
infections as "new", reemerging or drug-resistant infections
whose incidence in humans threatens to increase in the near
future." The report describes the urgency of addressing the
problem of emerging infectious pathogens. "It is time to
mount an organized collaborative national and global counter
offensive against these potentially deadly microorganism."
(Quote from 1992 National Institute of Medicine report.)
According to Ralph Touch, Chief Sanitarian of the Public
Health Service, "emerging infectious diseases in the United
States include a wide variety of parasitic, bacterial and
viral diseases." (p. 3)
Bernard LeGuenno, a virologist who leads the national
reference center for hemorrhagic fever at the Pasteur
Institute in Paris, in an article "Emerging Viruses" in
Scientific American of October of 1995, writes about the
emerging hemorrhagic fever viruses which he says are "among
the most dangerous biological agents known."
According to his article, one of these viruses, the
hantavirus, has shown up in several places in the United
States. LeGuenno reports "Hantavirus Sin Nombre, {Spanish for
"no name"} strikes 114 and kills 58 in New Mexico, Colorado
and Nevada in 1993; in 1994 a researcher at Yale University
is accidentally infected with Sabia but survives" (p, 58)
LeGuenno vividly describes what happens when one is infected
by these dangerous viruses:
Sabia and Sin Nombre both cause illnesses classified as
hemorrhagic fevers. Patients initially develop a fever,
followed by a general deterioration in health during
which bleeding often occurs. Superficial bleeding
reveals itself through skin signs, such as petechiae
(tiny releases of blood from vessels under the skin
surface), bruises or purpura (characteristic purplish
discolorations). Other cardiovascular, digestive, renal
and neurological complications can follow. In the most
serious cases, the patient dies of massive hemorrhages
or sometimes multiple organ failure. (pp. 56-7)
An article by Peter Jaret (medical writer) entitled
"Viruses" in National Geographic for July 1994 also reports
the latest pathogen threat from emerging viruses--the "hot
agents--viruses that spread easily, kill swiftly, and have no
cures or vaccines." (p. 64) These viruses are so deadly that
extreme precautions must be observed by scientists who study
them. According to the article, scientists at CDC "must wear
suits hooked to outside air supplies and enter a lab via
airtight hatches that seal behind them. All materials
entering the lab must be sterilized or burned to ensure that
nothing hazardous escapes." (p. 64)
Jaret began his article with a firsthand graphic
description of the effects of one of these deadly hot
viruses, Lassa fever, on its young victim:
First came fever. Then Hamid Mansaray, a young nurse's
aide at a remote African hospital, began to hemorrage.
Blood erupted from his nose and mouth. It burst out of
capillaries beneath his skin and eyes. By the time I
reached the village of Panguma in Sierra Leone, Mansaray
lay isolated in a special ward. Doctors had diagnosed an
obscure illness called Lassa Fever. Its cause was a
virus, an infective agent so small that 100,000 all
clumpted together would still scarcely be visible.
(p. 64)
He also describes his trepidation upon entering the
Lassa fever ward where Mansaray lay:
It is also what made my chest tighten as we entered the
Lassa fever ward. I knew that in neighboring Liberia a
medical team had unsuspectingly treated a pregnant woman
who was infected with the Lassa virus. Within four weeks
two patients from the ward and two of the hospital staff
were dead.
According to Jaret, although the Lassa fever virus is
frightening, a more frightening hot virus is the one that
causes Ebola fever. He reports that the Ebola virus, which
was first documented in 1976 when it killed half the people
in a small village in the Sudan, affects its victims much
like the Lassa virus causing fever and bleeding. He wrote
that by the time it had later struck Zaire, it was "seemingly
more virulent than before." (p. 64) It killed 90% of its
victims in over 50 villages.
Although these hot viruses have mostly been found in
Africa, the rest of the world is not safe from infection--
including the United States. Jaret reports on what could have
been a disastrous outbreak of Lassa fever in Chicago.
According to his account, in 1989, a 43-year-old mechanical
engineer, who had recently returned from attending his
parents' funerals in Nigeria, came to a suburban Chicago
clinic with a fever and sore throat. He was sent home with a
prescription for antibiotics. More than a hundred people had
come into contact with him before he died. Jaret reports the
concerned reaction of the CDC to this incident: "We had all
the makings of a catastrophe," said C.J. Peters, who directs
the CDC's Special Pathogens Branch. The disaster may have
been prevented because threat of the AIDS virus had led to
stringent standard sanitary procedures. According to Jaret,
"Next time," says Peters, "we may not be so lucky."
(pp.65., 67).
We may not be so lucky because as Jaret says in his
article "When a rare virus does emerge from its seclusion,
modern air travel may offer it a free ride anywhere in the
world. "(p. 65) This was brought home to us in 1996 when a
research laboratory outside of Alice, Texas, which our fire
and safety company serviced, averted a near catastrophe when
during the quarantine period they discovered a monkey brought
over from Africa was carrying the Ebola virus. Fortunately,
the monkey was destroyed before it could spread the virus.
Detection of Pathogens
It has been recognized in Germany, at least since D.
Strauch published his paper in 1991, that" most pathogenic
agents can survive the treatment process" and the sewage
treatment process causes some of the pathogenic disease
organisms to be absorbed or enclosed in faecal particles
during the treatment process. "Therefore," according to
Strauch, "sewage sludge is rightly described as a
concentration of pathogens."
In a personal interview with scientist David Lewis of
the EPA, who is a whistleblower, more disturbing facts about
pathogens and their detection came to light including the
information about the AIDs virus. According to Lewis,
standard test methods underestimate the number of water
repellant contaminates. In looking at the aids virus found on
medical and dental tools, Lewis discovered that the HIV
virus, when it was covered with a water repellant lubricant
such as silicone, was still infectious after several days.
The water repellant lubricants such as silicon and petroleum
products cover the pathogens and prevent them from being
found by standard test methods. It was only when he dissolved
the lubricants with acetone or other solvents, that the
pathogens showed up in tests. "Body fluids also break down
the lubricants surrounding the contaminates," he said. Lewis
has brought these facts to the attention of the Food and Drug
Administration who is supposed to be setting up a committee
to study the problem.
"The problem of pathogen detection in sludge, according
to Lewis, "is that the sewage treatment process changes the
outside crust of the aggregates in sludge and only the
pathogens on the outside of the aggregates are measured by
standard tests." He says that most of the microbes are
trapped inside the aggregates. When ultrasound was used to
break open the aggregates of sludge the trapped microbes were
revealed. In effect, it appears that the treatment processes
hide most of the pathogens rather than destroying them.
Straub, Pepper and Gerba say that the list of pathogens
are not constant but keep changing:
As advances in analytical techniques and changes in
society have occurred, new pathogens are recognized and
the significance of well-known ones change.
Microorganisms are subject to mutation and evolution,
allowing for adaptation to changes in the environment.
In addition, many pathogens are viable but nonculturable
by current techniques (Rozak and Colwell 1987), and
actual concentrations in sludge are probably
underestimated.(p. 58)
They add further:
Thus, no assessment of the risks associated with the
land application of sewage sludge can ever be considered
complete when dealing with microorganisms. As new agents
are discovered and a greater understanding of their
ecology is developed, we must be willing to reevaluate
previous assumptions. (p. 58)
Some pathogens have even developed resistance to time-
tested controls such as heat and refrigeration. Several of
the alternatives to reduce pathogens in sludge products use
heat at temperatures of 55 C and above to achieve Class A
status. However, according to the article "Pathogen
Destruction and Biosolids Composting" in Biocycle of June of
1996, "There is some evidence that coliforms and Salmonella
sp. can survive prolonged exposure to temperatures of 55 C."
They cite a study done by Droffner and Brinton (1995) using
DNA gene probes, where they detected E. coli and Salmonella
sp. in samples collected from an in-vessel composting
facility after the first 15 days of active composting at a
temperature above 55 C. In Table 5-4 Processes to Further
Reduce Pathogens in A Plain English Guide to the EPA Part 503
Biosolids Rule, composting time and temperature requirements
for within-vessel composting method was 55 C or higher for
three days! Droffner and Brinton found that it took 56 days
and 90 days for the densities of Salmonella sp. and E. Coli,
respectively, to decline below the detection limit...These
investigators also "cite evidence of mutant strains of E.
coli and Salmonella sp. resistant to thermal environments in
composting." (p. 68)
According to microbiologists, some bacteria form an
endospore, a cell type developed from the vegetative
bacterial cell through a sequence of morphological changes.
Although the vegetative cell of bacteria is usually killed by
heat and disinfectant, the endospore is resistant to agents
that kill the vegetative cell (heating, drying, freezing,
chemicals, and radiation). Nester, Roberts, Pearsall and
McCarthy (1978) in their text Microbiology point out the
threat that endospores present. They say:
Endospores represent the most resistant form of life
known; they tolerate extremes of heat and dryness, the
presence of disinfectants, and radiation. Some members
of Bacillus and Clostridium play a role in fixing
atmospheric nitrogen and others cause serious infectious
diseases. Thermophilic strains of Bacillus can grow at
temperatures above 70 C (158 F) (p. 260)
Linne and Ringsrud (1979) in their text Basic Techniques
for the Medical Laboratory also point out how spores, as
highly resistant forms of bacteria, pose a great problem in
sterilization. They state that certain spores have been known
to survive 16 hours of boiling. (p. 452)
One of the methods for treating sludge for pathogen
reduction is adding lime to a pH of 12. According to a study
done by John Walker, when he was with the USDA in Beltsville,
liming doesn't prevent regrowth of Salmonella. When John
Walker (USDA) and a colleague conducted experiments to
determine what would happen to disease organisms in limed
soil, they found Salmonella organisms even at the highest
lime levels which indicated that Salmonella had regrown when
the pH dropped. (p. 46) According to Dean of the EPA, "We
know that a limed sludge if stored too long will putrefy,"
(p. 46).
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