vc/EPA
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S1-81-028 Apr 1981
Project Summary
Aerosols Generated by Liquid
Sludge Application to Land
H. J. Harding, R. E. Thomas, D. E. Johnson, and C. A. Sorber
This report provides data on charac-
terization of geographically diverse
digested municipal sludges with
respect to microbiological, trace
metal, pesticide, and polychlorinated
biphenyl constituents plus micro-
organism levels in aerosols generated
in the land application of these
sludges, utilizing tank trucks and
spray guns. With a knowledge of
aerosol levels from this practice,
recommendations can be made to
reduce exposure to potentially harm-
ful materials.
This Project Summary was develop-
ed by EPA's Health Effects Research
Laboratory, Cincinnati. OH. to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report information at back).
Introduction
Land application of human waste is
an attractive waste disposal alternative
to disposal in surface waters This
approach avoids contamination of the
surface water supplies, returns nutri-
ents to the soil, reuses the water and
other wastes, and provides additional
waste treatment. The policy of the
Environmental Protection Agency is to
"press vigorously for publicly-owned
treatment works to utilize land treat-
ment processes to reclaim and recycle
municipal wastewater " Disposing of
municipal sludge has become a major
public concern in that sludge will be
produced at municipal treatment plants
in the U.S. at the rate of approximately
four and one-half billion dry kilograms
annualy by the early 1980's. At the
present time, municipal sludge is being
disposed of via incineration (35 per-
cent), ocean disposal (1 5 percent), land-
fills (25 percent), and land application
(25 percent) Incineration contributes to
air pollution and is also energy
dependent. Federal regulations will
prohibit ocean dumping of sludge after
1 981 Landfill is not practical mall areas
of theU.S and has potential problems in
contamination of ground and surface
waters due to the concentration of
sludge in one area Land application is
an attractive alternative to these
processes
Objectives
This study was initiated to provide
information on the generation of harm-
ful microbial aerosols near sites practic-
ing land application of liquid municipal
sludge Very little information is avail-
able regarding the production of
microbial aerosols as to the types or
quantities of organisms produced
Because of the importance of land
application of municipal sludges, the
U S Environmental Protection Agency
must collect the necessary data to
answer the safety questions If
problems are identified, then it is likely
that changes in the mechanism in
applying sludge can be made using
current technology
The original objective of this study
was to determine if the use of tank
trucks in applying liquid sludge to land
resulted in the formation of pathogenic
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microbial aerosols A secondary objec-
tive was to characterize the sludge from
several sites practicing land application
for the presence and levels of micro-
biological constituents, trace metals,
and pesticides
During preliminary site evaluation,
sites were identified which utilized
high-volume spray guns to apply liquid
sludge The program objectives were
expanded to include evaluation of
aerosols generated at spray application
sites and to compare these results to
those from the truck sites and to sites
conducting spray application of waste-
water.
Methods
A preliminary screen was conducted
at six sites to characterize sludge with
regard to bacteria I and viral microorgan-
isms, trace metals, organochlorme
pesticides, and polychlormated bi-
phenyls (PCB's), and to evaluate each
site for its suitability for aerosol
monitoring Four sites were selected for
aerosol monitoring, two practicing tank
truck application and two practicing
spray gun application From five to eight
aerosol monitoring runs were made at
each of the four sites, and a special
enterovirus aerosol run was conducted
at one of the spray sites
The preliminary screens were used to
indicate what levels of microbiological
and chemical constituents could be
routinely expected in liquid sludge The
aerosol data were used to indicate
'Whether there was aerosolization of
microbiological constituents and as
input to dispersion modeling
Conclusions
All six sites and all samples contained
measurable levels of cadmium, copper,
mercury, nickel, lead, and zinc The
mean concentrations ranged from 1 5 7
/yg/g for mercury to 9,180/jg/g for zinc,
on a dry weight basis. Molybdenum was
detected in only three samples, at con-
centrations of 40, 48, and 140/ug/g, dry
weight.
Of the 16 priority pollutant pesticides
and seven PCS formulations screened
for in the sludge, only chlordane and
Aroclor 1248 were detected in any of
the samples The chlordane concentra-
tion in sludge fell between 11 and 16
/ug/g in the four samples in which it was
detected. Both samples from one site
(Muncie, Indiana) were found to contain
AR 1248, at 25 and 26/ug/g.
Microbiological screens of sludge
samples from all sites contained four
non-enteric bacteria and eight entero-
bactena organisms. Other organisms
were found in samples from one or more
of the sites
Generation of microbiological
aerosols most likely does occur at sites
utilizing tank trucks, but results m very
low bacterial aerosol levels. Monitoring
at these sites is difficult due to the fact
that a truckload of sludge is applied over
a short penod'of time while the truck
passes over several hundred meters of
land.
There was strong evidence for aero-
solization of microbiological organisms
at the spray application sites, notably
among the fecal coliforrn, fecal strepto-
cocci, and mycobactena results Fecal
coliforrn and fecal streptococci were
detected downwind at both sites, while
at Portland they were not consistently
detected at the background site and at
St. Petersburg were approximately two
orders of magnitude lower at the back-
ground sites Mycobactena data at St
Petersburg gave similar results to the
fecal coliforrn data
On a special virus run, 1,470 m3 of air
was sampled and no human enteric
viruses were detected from the pooled
sample. This converts to a concentra-
tion of less than 0 0016 pfu/m3 of air,
and the implication is that aerosol-
ization of viruses does not present a
significant problem
Recommendations
Where tank truck application is
exercised as the means of sludge
disposal, the generation of aerosols is
likely to be minimal If further reduction
is deemed necessary, the option of sub-
surface injection should be considered
Where spray application is the means
of disposal certain practices may be
observed to reduce formation of and
exposure to aerosols, e g , creation of a
buffer zone around the application site,
application as much as possible under
ideal meteorological conditions, and the
use of low-pressure, downward-
directed nozzles
The presence of microbiological
organisms in the sludge, as well astoxic
metals, pesticides, and polychlormated
biphenyls (PCB's), suggests that the
composition of the sludge should be
well known before land application is
accomplished. In addition to aerosol
generation, there is a potential for
harmful effects through soil and ground
water, and there should be some assur-
ance prior to land application that levels
of these contaminants do not exceed
tolerable levels
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H. J Harding, R. E Thomas, and D. E Johnson are with the Southwest Research
Institute, San Antonio, JX 78284, and C. A Sorber is with the University of Texas
at San Antonio, TX 78285
Norman E. Kowal is the EPA Project Officer (see below)
The complete report, entitled "Aerosols Generated by Liquid Sludge Application to
Land," (Order No PB 81-178 857, Cosf $11.00, subject to change) will be
available only from.
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Health Effects Research Laboratory
U S Environmental Protection Agency
Cincinnati, OH 45268
i US GOVERNMENT PRINTING OFFICE 1981 757-012/7064
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
Environmental
Protection
Agency
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Official Business ..
Penalty for Private Use $300
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