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Proceedings of the 1983 Workshop on
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UTILIZATION OF MUNICIPAL WASTEWATER
AND SLUDGE ON LAND
edited by
A. L Page, Thomas L. Gleason, lli, James E. Smith, Jr.,
I. K. Iskandar, and L. E. Sommers
Sponsored by
U.S. Environmental Protection Agency
U.S. Army Corps of Engineers
U.S.D.A. Cooperative State Research Service
National Science Foundation
University of California-Kearney Foundation of Soil Science
1983
University of California
Riverside, CA 92521
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Proceedings of the 1983 Workshop on
UTILIZATION OF MUNICIPAL WASTEWATER
AND SLUDGE ON LAND
edited by
A L. Page, Thomas L. Gleason, ill, James E. Smith, Jr.,
I. K. Iskandar, and L. E. Sommers
Sponsored by
U.S. Environmental Protection Agency
U.S. Army Corps of Engineers
U.S.D.A. Cooperative State Research Service
National Science Foundation
University of California-Kearney Foundation of Soil Science
1983
University of California
Riverside, CA 92521
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Although the information in this document has been funded wholly or in
part by The United States Environmental Protection Agency under Contract
No. CR 810529-01-2 to the Department of Soil and Environmental Sciences,
University of California, Riverside, it does not necessarily reflect the views
of the Agency and no official endorsement should be inferred.
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PREFACE
The proceedings consist of opening remarks, position papers, and work-
shop findings. Briefly, the position papers discuss institutional constraints,
hydrologic and nutrient management, pathogens, metals, organics, engi-
neering and economics, and an overview of public health effects. These
papers set the stage tor six separate subject matter sessions. Each work-
shop used the position papers as a basis for assessing the current state-of-
the-art and identifying research needs for its respective topic area. The
workshop sessions considered engineering systems, institutional con-
straints, management considerations in sludge and effluent use, and
public health and risk assessment. Following the report of each workshop
session appear questions and answers. These questions were raised both
during the workshop session and when the moderators presented their
findings in the concluding plenary session. In an appendix appear the
names and affiliations of the individuals responsible for organizing the
workshop and the contributors/participants to the workshop.
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ACKNOWLEDGEMENTS
The workshop on Utilization of Municipal Wastewater and Sludge on
Land was made possible by support from the U.S. Environmental Protec-
tion Agency, the U.S. Army Corps of Engineers, the U.S. Department of
Agriculture—Cooperative State Research Service, the National Science
Foundation, and the University of California-Kearney Foundation of Soil Sci-
ence. The financial support from these agencies is gratefully acknowledged.
A number of various federal agencies, colleges universities, and munici-
palities participated in the organization and planning of the workshop. The
idea for a second workshop to evaluate progress made in research and
development on land application of municipal wastewater and sludges
since the original 1973 workshop originated with Dr. A. L. Page, University
of California, Riverside, Drs. Raymond Thacker, William Rosenkranz,
Thomas Gleason, and James E. Smith, Jr., U.S. Environmental Protection
Agency—Office of Research and Development, and Dr. Alex Iskandar, U.S.
Army Corps of Engineers/Cold Regions Research and Engineering
Laboratory. Dr. Lee E. Sommers, Purdue University, and A. L. Page made the
necessary preliminary plans to establish the Organization and Planning
Committee. The Planning Committee met twice (February 12 and June 9,
1982) and developed the format for the workshop. The Committee also
selected topics and authors for the position papers as well as topics,
moderators, and recording secretaries for the six separate workshop ses-
sions. We acknowledge with appreciation all those who participated in the
organization and planning of the workshops. Committee members, along
with assignments, are listed in the Appendix.
Special thanks are due to the authors of the position papers, and the
moderators and recording secretaries of each of the six workshop ses-
sions. The moderators assumed the responsibility for the conduct of their
respective workshop sessions, the presentation of the findings of the
workshop session, and with the help of their recordings secretaries, the
preparation of their workshop reports. Moderators and recording
secretaries also served as reviewers for selected position papers. Sincere
thanks are due the 209 invited workshop participants who were assigned
to one of the six workshop sessions according to their interest and expert-
ise. These individuals gave freely of their knowledge and experience in ad-
dressing the issues set forth in the workshop sessions. A listing of the
workshop moderators, recording secretaries, and the invited individuals
who participated in each workshop appears in the Appendix.
Local arrangements for the workshop were coordinated with Mr. Stanley
Smith and Mr. Roger Dean from the Denver Regional Environmental Protec-
tion Agency office and Dr. Hunter Follett of Colorado State University. We
acknowledge with thanks their help In handling the many details associ-
ated with local arrangements. The most capable assistance of Mr. Michael
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Linville, U.S. Environmental Protection Agency—Cincinnati, in the organiza-
tion of registration and meeting room facilities, and Mrs. Winnie Gillette,
University of California, Riverside, who assisted in registration and the typ-
ing of visual aids and workshop reports is also gratefully acknowledged.
We acknowledge with deep appreciation the most capable assistance of
Mr. Tony Ganje, University of California, Riverside, who reviewed and edited
the proceedings from cover to cover.
Finally, we owe a most special debt of gratitude to Mrs. Leslie Webster,
University of California, Riverside, who assisted the workshop committee
in each and every phase of their responsibilities from the initial meeting to
the final publication of the workshop proceedings.
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TABLE OF CONTENTS
Preface Ill
Acknowledgements V
Workshop Highlights 1
Introduction and Background 9
Opening Remarks
A DECADE OF PROGRESS
Courtney Riordan 15
THE NECESSITY OF REGIONAL RESEARCH
Raymond J. Miller 23
Postion Papers
INSTITUTIONAL CONSTRAINTS
D. Lynn Forster and Douglas Southgate 29
ENGINEERING AND ECONOMICS
Charles E. Pound, Douglas A. Griffes,
and Ronald W. Crites 53
HYDROLOGIC MANAGEMENT: NUTRIENTS
Dennis R Linden, C. E. C/app,
and Robert H. Dowdy 79
HYDROLOGIC MANAGEMENT: TRACE METALS
Andrew Chang and A. L. Page 107
FOREST SYSTEMS
Dale W Cole, Charles L. Henry, Peter Schiess,
and Robert J. Zasoski 125
PATHOGENS
Charles P. Gerba 147
SPECIFIC ORGANIC COMPOUNDS
Michael R. Overcash 199
METALS
Terry J. Logan and Rufus Chaney 235
AN OVERVIEW OF PUBLIC HEALTH EFFECTS
Norman E. Kowal 329
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Workshop Findings
POLITICAL AND INSTITUTIONAL CONSTRAINTS
William Davis, Richard White, Lee Christensen,
and Hunter FoUett 399
ENGINEERING SYSTEMS
Raymond Loehr, Sherwood Reed, Takashi Asano,
and James Parr 409
MANAGEMENT CONSIDERATIONS IN EFFLUENT USE
Parker F. Pratt, William E. Sopper, Richard Thomas
and Lowell Leach 419
MANAGEMENT CONSIDERATIONS IN SLUDGE USE
Lee E. Sommers, V. V, Volk, and Lee W. Jacobs 427
PUBLIC HEALTH AND RISK ASSESSMENT: PATHOGENS
Elmer Akin, Wiley Burge, and Bernard Sagik 439
PUBLIC HEALTH AND RISK ASSESSMENT:
ORGANICS & INORGANICS
Herbert Pahren, Delbert D. Hemphill, James Ryan,
and Mary Beth Kirkham 453
Appendix
Organization and Planning Committees 465
Names and Addresses of Participants 467
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WORKSHOP HIGHLIGHTS
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Page 3
WORKSHOP HIGHLIGHTS
The significant developments in land treatment and future research
needs identified in each workshop are briefly summarized.
POLITICAL AND INSTITUTIONAL CONSTRAINTS
Findi ngs
• Research conducted in the past decade has provided information
needed to base federal, state and local guidelines and regulations;
identify and resolve design problems and operational constraints,
and to identify and resolve general concerns.
• The need exists to provide land treatment information to the general
public in an understandable form to allay health fears.
• Unqualified assurance of no risk cannot be provided. Assuming good
management in a given situation, assurance can be given that land
application of sludges and wastewaters can be accomplished with mini-
mal risk.
• Federal regulations should contain minimum standards for key health
parameters; require public notification of noncompliance as well as
good management practices; require consideration of reasonable alter-
natives for management of wastewaters and sludges, and provide suf-
ficient flexibility to permit states and local agencies to combine
environmentally sound and socially acceptable management practices
with their unique social, political, and physical factors.
• Public acceptance can be Improved by involving of elected officials,
opinion leaders in decision making, and continuing education and
communication programs for all affected groups and individuals.
Research Needs and Recommendations
• Major research needs Include: risk assessment data for pathogens and
organic contaminants in wastewater and sludges; land treatment
system case studies and follow-up studies; a continuing interagency
sludge task force, and better communication between universities and
municipalities.
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Page 4
ENGINEERING SYSTEMS
Fi ndi ngs
• Land application is a viable, environmentally sound and cost-
effective technology for both wastewater and sludge disposal. More
than a thousand wastewater land treatment systems are currently in
operation; a similar number in various stages of planning are ex-
pected to be in operation within the next decade.
• Land treatment is not just a disposal process. This total systems
approach allows rational engineering designs to include appropriate
provision for pollutant removal within the soil-plant ecosystem.
Wastewater treatment is the primary goal of a land treatment system.
• When properly designed and operated, the reliability and performance
of land treatment of municipal wastewater systems are equal to or
greater than other conventional practices. They are dependable in
all climates and geographical areas of the USA.
• Information developed since 1973 permits the design of systems that
meet existing water quality criteria.
Research Needs and Recommendations
• Major information gaps exist in the following areas: postconstruc-
tion performance evaluations and cost documentation of existing land
treatment systems; design criteria for application of municipal
wastewater and sludge to forest ecosystems; and heavy metal loading
criteria in terms of regional considerations and long-term sludge
loadings.
MANAGEMENT CONSIDERATIONS IN EFFLUENT USE
Findlngs
• Land treatment systems are now successfully operated throughout the
world. Infiltration rates, nitrogen leaching and crop uptake of
nitrogen, and runoff among other potential problems, can be con-
trolled through proper engineering operation and management.
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Workshop Highlights
Page 5
• Soils and climates have been characterized as to their suitabilities
for various land treatment systems.
•Adequate information is available for slow rate systems to assess:
crop selection, response, and management; erosion control; hydraulic
loading rates; heavy metal, suspended solids and phosphorus reten-
tion; quality criteria for irrigation use; and decomposition of most
of the organic materials in the wastewater (some synthetic organics
are exceptions).
•Adequate information is available for rapid infiltration systems to
determine retention of suspended solids, reduction in biochemical
oxygen demand (BOD) and heavy metal loadings.
Research Needs and Recommendations
• There is a general need for more technology transfer and training of
managers of land treatment systems.
• Mathematical models of slow rate and rapid infiltration systems have
been developed but must be verified by field data so that they can
be used to maximize the efficiency and reliability of wastewater
treatment systems.
• A major research need is for risk assessment of potential human
exposure to pathogens in land treatment systems, as opposed to those
risks associated with conventional municipal wastewater treatment
systems. Also required are long-term studies of ecosystem dynamics
both on-site and off-site, of renovation efficiency 1n relation to
site aging; and of ecosystem collapse and recovery 1n a system not
properly operated.
MANAGEMENT CONSIDERATIONS _I_N SLUDGE USE
Findings
• Guidelines have been developed to enable the environmentally safe
use of sewage sludge containing median concentrations of metals and
organics when the sludge 1s applied at agronomic rates based on
nitrogen or phosphorus utilization by crops. Sludge can be success-
fully used as a substitute for conventional fertilizer materials,
especially phosphorus and to a lesser extent, nitrogen.
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Page 6
•Current guidelines for the cumulative application of copper, zinc
and nickel are safe but should be refined to reflect regional soil
differences. Soil properties should be re-assessed to account for
regional differences in soil characteristics.
• Concentrations of synthetic organics in sludges are generally low
but high concentrations way exist in some sludges. Most synthetic
organics are decomposed in soil. Current federal regulations for
PCB's in sludges are adequate to protect animal health.
•Groundwater monitoring for nitrate-nitrogen is not needed where
sludge nitrogen additions do not exceed fertilizer nitrogen recom-
mendations for the crop grown.
•Utilization of sludge for reclamation of disturbed land at rates
higher than those for agricultural land, when properly implemented
and managed, improve the quality of soils, groundwater or vegeta-
tion.
Research Needs
•Major information needs for the agricultural use of sludge include:
determination of the availability of metals to plants following ter-
mination of sludge applications; development of models to predict
and further refine nitrogen behavior in sludge-amended soils with
emphasis on ammonia volatilization, organic nitrogen mineralization
and denitrification; and determination of the factors affecting or-
ganic chemicals' decomposition, mobility, fate and potential accumu-
lation in plants and animals.
• Major information needs for the application of sludge to forest land
include: the quantitative determination of nitrogen cycling, and
development of data required to establish criteria for site selec-
tion, metal limits, and runoff and leachate quality. Improved ap-
plication and management techniques are also needed.
• For land reclamation, methods are needed to maintain vegetative cov-
er, and to identify the plant species that are most responsive to
relatively high loading rates of sludge as well as tolerant of ad-
verse conditions of disturbed land.
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Workshop Highlights
Page 7
PUBLIC HEALTH AND RISK ASSESSMENT: PATHOGENS
Findings
• With proper management and safety allowances based on research data,
land application is a safe, beneficial and acceptable alternative
for treatment of municipal wastewater and sludge.
• At the time of the workshop, in the U.S. there are no known out-
breaks of infectious disease attributable to land application of
wastewater or sludges.
• Major improvements in monitoring methods, especially in the virus
area, have been achieved. Data generated during the decade since
1973 provided the scientific bases for criteria at the federal
level.
• In terms of current detection capability, federal sludge disposal
criteria are adequate to protect public health from pathogenic
microorganisms. Data currently being generated will provide guid-
ance to any consideration for relaxation of the criteria. Criteria
and management guidance based upon geographical considerations are
warranted.
Research Needs and Recommendations
• Although some major research needs identified in 1973 are still
pending, research priortles have changed. For example, epidemio-
logical studies no longer remain a high priority research need.
• For bacteriology, Information needs Include: survival and growth of
pathogens, Improvement of detection methodology and virulence
assessment, effectiveness and mechanisms of treatment processes,
relevance of current Indicators and their movement through soils.
• For parasitology, the needs include: pathological effects of re-
peated low level ascarld infections; virulence of swine vs. human
ascaris; potential pathological significance of naeglerla and simi-
lar organisms 1n waste-treated soils, and survival of ascaris ova
in sludge-treated soils.
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Page 8
• For virology, the needs include: site monitoring studies of survival
and movement of viruses under a wide range of soils, climatic, hydro-
logic, and waste conditions; effectiveness of conventional sewage
treatment processes along with land treatment, and methodology to
detect hepatitis A, Norwalk-agent and rotaviruses.
PUBLIC HEALTH AND RISK ASSESSMENT: ORGANICS AND INORGANICS
Findi ngs
• No longer are there serious gaps 1n knowledge of the impact on human
health of organic and inorganic contaminants 1n municipal wastewater
and sludge when applied to land.
• At annual sludge application rates less than 15 mt/ha, where a
reasonable drainage and cyclic establishment of sustained aerobic
soil conditions occur, and groundwater remains deeper than 0.3 to
0.7 meters from the soil surface, leaching of metals and organics
should pose little or no threat to groundwater processes. However,
adjustments may be necessary because of site specific conditions.
• Wastewaters should not be chlorinated prior to high rate application
to land since precursors to halogenated organics may form.
• Except of cadmium, heavy metals are not expected to create a human
health problem in sludge-amended soils.
Research Needs and Recommendations
• In view of the substantially better data base today, an internation-
al panel should re-evaluate the 1972 recommendations of the WHO/FAO
limits for cadmium 1n the diet.
• More research is needed on the factors affecting migration of orga-
nics through various soils, and their decomposition 1n groundwater.
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INTRODUCTION AND BACKGROUND
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Page i1
INTRODUCTION AND BACKGROUND
On February 23-25, in Denver, Colorado, a workshop on Utilization of
Municipal Wastewater and Sludge on Land was convened, A total of 203
invited researchers and practitioners of land treatment from all areas of
the United States and abroad assembled to evaluate advances made in the
state of knowledge during the last decade, that is, since 1973 when a
similar conference was held in Champaign, Illinois. Thirty-seven percent
of the participants in the Denver conferences were from colleges, univer-
sities, arid agricultural experiment stations; thirty-one percent were from
federal government agencies; sixteen percent each were from state and
local governments and consulting firms. More than thirty people partici-
pated in each of the six separate workshop sessions. Significant develop-
ments in land treatment since 1973, and critical future research needs and
recommendations identified by each workshop session, are discussed in the
"Highlights" and "Workshop Findings" sections of these proceedings.
This workshop was co-sponsored by the U.S. Environmental Protection
Agency, USDA-Cooperative State Research Service (CSRS), the University of
California-Kearney Foundation of Soil Science, the U.S. Army Corps of
Engineers, and the National Science Foundation.
The 1973 Conference in Champaign was cosponsored by the U.S. Environ-
mental Protection Agency (USEPA), U.S. Department of Agriculture (USDA)
and the National Association of State Universities and Lard Grant Colleges
(NASULGC). In 1973, there was a need to Identify research needs asso-
ciated with the recycling of municipal sludges and effluents on land. The
major approach then was presentation and discussion of state-of-the-art
papers, and development of an agenda for critical research. This earlier
conference provided the stimulus for an extensive program of research con-
ducted by federal, state, municipal and private agencies.
The data base established from that ongoing research enabled the pro-
mulgation of federal and state regulations and guidance concerning munici-
pal sludge and effluent use or disposal on land. In addition to regula-
tions formulated on the federal level, more than 20 state governments
established regulations or guidelines for land application of municipal
sludges and effluents. Over the past ten years, continuing research has
led to the use of land application for treatment of municipal wastewater
and sludge at more than 1,000 sites nationwide.
Although substantial progress has been made in land application of
sludges and effluents, there was a need to assess and evaluate progress
over the past decade. In 1979, USDA-CSRS Technical Committee for "Optimum
Utilization of Sewage Sludge on Agricultural Land" contacted the chairman
of the EPA-USDA-NASLUGC Subcommittee on "Recycling of Municipal Effluents
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Page 12
and Sludges on Land" to explore the feasibility of convening such a
workshop. Subsequently, ad hoc meetings were held to discuss 1n greater
depth the possible need to hold a second conference along the lines of the
1973 EPA-USDA-Universities workshop. In 1981, an EPA sludge policy com-
mittee was formulated between Agency offices, thereby clearly signaling a
need to assess information available and to define future needs for re-
search on land application practices. All of these processes, happening
more or less simultaneously, culminated in a planning meeting held in
Washington, D.C., on June 9, 1982, where the decision was made to convene
a second workshop with the following objectives: (1) reassess the research
needs enumerated in 1973 in light of present knowledge on land application
of municipal sludges and effluents, (2) identify still existing critical
research needs, and (3) formulate recommendations for future research and
development.
This publication Includes state-of-the-art papers and the findings of
the workshop. It also delineates specific research needs and recommen-
dations and thereby provides agencies with the information essential to
establish priorities for research. The Information contained 1n the
publication will provide guidance for all those involved 1n research and
development associated with the land application of municipal wastewater
and sludge.
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OPENING REMARKS
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Page 15
A DECADE OF PROGRESS
Courtney Riordan
Acting Assistant Administrator
Research and Development
U.S. Environmental Protection Agency
Washington, O.C.
INTRODUCTION
I am pleased to participate in this second Environmental Protection
Agency (EPA), Office of Research and Development (ORD) Workshop on
Utilization of Municipal Wastewater and Sludge on Land. The co-sponsor-
ship of the other agencies is greatly appreciated. I have an abiding
interest in the use of the land as a medium for managing treatment, use,
and disposal of sludges. We are revisiting an environmental problem area
that is as important today as it was at the time of the first workshop.
This afternoon I would like to review briefly some of the progress
made since the Champaign, Illinois Workshop in 1973. A great deal of
work has been completed since 1973 in both the municipal wastewater and
sludge areas. I expect that the workshop participants will recognize the
accomplishments during those 10 years, but I also realized that there is
still work to be done. The science, public perception, and socio-
economic problems and issues are extremely complex, having defied fully
definitive answers for many years.
The ORD within the EPA has long been actively involved In fostering
the development of applicable technology and providing scientific data
for the Agency 1n the areas of land treatment of municipal wastewater and
sludge treatment, utilization, and disposal. The 1973 workshop accom-
plished the objective of identifying the state-of-knowledge in these two
important technology areas. It was also successful 1n identifying the
critical categories of research and development where the views of
national experts were sought concerning additional scientific knowledge
and technology needed for successful utilization of land application
techniques. Consideration of the economic, engineering, health and
aesthetic aspects were included in this request for guidance. The work-
shop proceedings, Reayaling Municipal Sludges and Effluents on Land,
Identified research needed in ten major areas:
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Page 16
RIORDAN
1. Educational and Informational Needs
2. Public Health Aspects
3. Dimensions of the Problem
4. Land Resources - Sludge
5. Land Resources - Effluents
6. Plant Characteristics and Response - Soil - Nutrient
Relationships, Crop Selection, and Management
7. Plant Characteristics and Response - Toxic Chemicals
8. Options, Problems, and Economics - Engineering Systems
9. Options, Problems, and Economics - Agricultural Management
10. Political and Institutional Constraints
The science and engineering communities utilized the guidance ema-
nating from the workshop to direct their research efforts. The progress
toward resolving the issues 1s substantial and I'd like to take a few
minutes to give you my perspective relative to the two areas to be ad-
dressed during these three days.
LAND TREATMENT OF MUNICIPAL WASTEWATER
The 1972 amendments to the Federal Water Pollution Control Act (PL
92-500) called for the EPA Administrator to encourage recycling of poten-
tial sewage pollutants through the production of agriculture, silvi-
culture, or aquaculture products, reclamation of wastewater and the
ultimate disposal of sludge In a manner that will not result in environ-
mental hazards. This paraphrases a key section of the Act, but when
placed in the context of a newly established national goal of eliminating
the discharge of pollutants, it became clear that use of the land 1n
managing wastewater and sludges was going to be necessary. In 1973 the
technology for this concept was 1n its Infancy and we really didn't know
how to design land treatment systems with assurance that they would per-
form satisfactorily.
Several things happened for research on land application of waste-
water 1n a relatively short time 1n the early 70's. The Muskegon Land
Treatment Demonstration Project, largest 1n the nation, got underway
along with several smaller projects and began producing data. Those land
treatment aspects which could have Impact on public health such as aero-
sols and toxic materials such as heavy metals 1n the food chain were
intensively studied, along with nutrient management (primarily phosphorus
and nitrogen) and engineering design.
The result of these efforts by the university community, state,
federal, and local governments was the development and publication In
1977 of the Proaeee Design Manual for Land Treatment of Municipal
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A Decade ol Progress
Page 17
Wastewater. Continued study of land treatment systems resulted 1n the
1981 revision of the manual, incorporating the latest scientific and
engineering information. This manual has been a real milestone in waste-
water management, especially since it incorporated the joint efforts of
the four federal agencies primarily involved in the development and eva-
luation of the technology: the Environmental Protection Agency, the Ariiy
Corps of Engineers, Department of Agriculture, and the Department of the
Interior.
The 1977 and 1981 amendments to the Clean Water Act recognize that
land treatmet technology has advanced beyond the R&D stage and has been
designated as an alternative system(s) within the Innovative/Alternative
Technology portion of the EPA Construction Grant Program. Most state
governments have established regulations or guidance for land application
of effluents and municipal sludges. We clearly have come a long way in
this area during the past ID years.
LAND APPLICATION OF SLUDGES
While the use of land for treating wastewater faced unresolved
design and management questions as well as socio-economic problems and
political issues, resolution of the problems and issues associated with
application of sludges to the land has been even more difficult. In 1973
when PL 92-500 came into full play, a major portion of the municipal
sludge generated in the United States was applied to the land 1n some
manner. Some was even placed in open dumps and a large amount was stored
in lagoons or by other means because of the difficulties associated with
di sposal.
Soon after the passage of the 1972 amendments to the Federal Water
Pollution Control Act it became clear that a great deal more sludge would
be generated because of the national requirement of secondary treatment.
It also became quickly apparent that the then existing practice of dispo-
sal was inadequate for protection of the environment.
The 1973 workshop recognized these facts and Identified many of the
technical problems and the research and development necessary to resolve
them. EPA recognized the need to come to grips with sludge management
problems and formed an Interagency Task Force in 1974 to review the tech-
nical and socio-economic issues that existed and to develop guidance that
could be applied at the state and local level to begin a nationwide
sludge management effort. Management would Include treatment technology,
beneficial uses, and disposal.
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Page 18
RiOROAN
The principal result of the efforts of the Task Force came about in
1977 when a technical bulletin Municipal Sludge Management: Environmen-
tal Factors was issued. Some of you here helped put that document
together.
Several other positive things happened during the past decade: the
Council for Agricultural Science and Technology (CAST) issued a report in
1976 and another recently (1981) dealing with sludge technology. The
1981 report addresses the problems of cadmium and zinc in sludges and
their impact on crops.
A Process Design Manual for Sludge Treatment and Disposal was issued
by EPA in September 1979. This manual was published to provide the engi-
neering comunity and related industry with a new source of information to
be used in the planning, design, and operation of present and future
wastewater pollution facilities. This manual describes the latest treat-
ment methods and techniques for more effectively managing municipal
sludges.
A design manual on Utilization of Municipal Sewage Sludge will be
available in October 1983. This manual will give detailed information
for (1) agricultural utilization, (2) application to forest land, (3)
application to disturbed land, and (4) dedicated land disposal.
Potential health impacts associated with applying sludge to the land
have been studied extensively since 1973, addressing the heavy metals
problems, nutrient issues, and the microbiological aspects. The parasite
aspects have been particularly important since very little sound scien-
tific knowledge was available at that time. In fact, analytical tech-
niques to identify the presence and viability of parasitic organisms were
not even available.
No single entity could conduct the RAD needed to fill the tech-
nology voids. However, a large amount of progress has been achieved
through Interagency or other cooperative efforts. A few brief examples
will serve to Illustrate how this has been done with EPA as one of the
partners.
Composting
Cooperative research with the Department of Agriculture (USDA) has
developed the static pile process from the concept to full-scale applica-
tion. Major scientific issues have been resolved and adoption of the
process by municipalities has been extensive. Within vessel techniques
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A Decade o: Progress
Page 19
applicable to ntore confined situations are now under study. The USDA
work resetted in a manual for composting sewage sludge by the Beltsville
Aerated-Pile method* which was published by EPA.
Disinfection
The Department of Energy with some EPA participation, developed a
method for disinfecting sewage sludge by means of gamma ray Irradiation.
Development work was carried out at the Sandia Laboratories utilizing
Cesium 137. The method destroys pathogenic organisms, making the product
more widely acceptable for use as fertilizer or animal feed. The work
has proceeded through pilot-scale and is ready for full-scale evaluation.
The Massachusetts Institute of Technology developed a method for
sludge disinfection using high energy electrons. The National Science
Foundation supported the work through pilot-scale and at least one city
is planning to utilize the method at full-scale.
land Application
EPA sponsored a field evaluation of a highly coordinated approach to
land application of sltidge. The project is conducted by the Ohio Farm
Bureau Development Corporation 1n conjunction with Ohio State University.
This 1s a multldlsclpllnary study considering the socio-political aspects
in addition ta microbiological and epidemiological features of land ap-
plication. The five year study has been completed arc the report Is ex-
pected tc be completed this fa?1» "lie project appears tc have produced a
successful model approach for use of sludge on private lands for meeting
the needs of small communities.
Sludge-Amended Pasture Land
EPA and the Food and Drug Administration (FDA) cooperated with the
Metroplitan Denver Sewage Disposal District #1 to evaluate the impact of
cattle grazing on pasture land which had received controlled applications
of municipal sludge. Pasture land which had never received any sludge
was used as a control area. Some direct feeding of sludge was also
Included 1n the study, which showed that the effects on cattle from expo-
sure to sewage sludge are essentially benign, especially when the sludge
is relatively low 1n contaminants of concern and tilled into the soil.
The direct Ingestion studies showed Increases of lead 1n bone tissues and
PCB's, DDE, dleldrln and oxychlordane in fat tissues. With regard to
cadmium, there was uptake into livers and kidneys in the feeding study,
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Page 20
RIORDAN
but not in the pasture experiments. These Increases apparently did not
affect the health of the cattle. Muscle, the cattle part most consumed
by humans, 1s protected from uptake of metal sludge contaminants.
We in EPA, plan to continue our research and development activities
in the municipal sludge area over the next few years. Our efforts will
be concentrated on the technology gaps that interfere with or constrain
use or disposal.
Improved methods of treating or processing sludge to prepare it for
environmentally sound use or disposal will be tested and evaluated. Di-
gestion offers a great deal of potential for Improvement 1n this regard
and as a means of conserving energy at the same time. Other thermal pro-
cessing techniques such as wet-oxidation have potential beyond current
use and new processes to make a useful product, such as Inert aggregate
for highway construction or a useful oil substitute are being examined.
The research associated with the health aspects of sludge management
1s currently reaching a point where specific concerns, such as the impor-
tance of parasites, may soon be placed 1n proper perspective.
I again must emphasize that EPA resources are limited. We need the
continued support and cooperation of the universities, federal, state and
municipal agencies, equipment manufacturers and others. This 1s the only
way that enough talent and other resources can be brought to bear on this
difficult environmental problem area. My colleagues and I see this work-
shop as one of -the ways we can obtain high quality advice and guidance.
Experience 1n sludge issues since 1977 indicates that an EPA policy
for sludge management 1s going to be necessary 1f we are to deal with the
issues in a workable and environmentally sound manner. The Administrator
therefore, established an Agency Sludge Policy Committee 1n October 1981
to address this problem. The Committee Includes the Assistant Admini-
strator for Water, Associate Administrator for Solid Wastes and Emergency
Response and the Associate Administrator for Policy and Resource Manage-
ment. A Sludge Task Force provides the technical support for the Commit-
tee. The Task Force 1s very active now and 1s getting good cooperation
and assistance from EPA offices and regions. It Is also obtaining inputs
from Individuals and organizations outside of EPA who are experts 1n
sludge management issues and technology. The Task Force expects to
complete Its work with a report to the Policy Committee by this fall.
Areas to be addressed include:
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A Decade of Progress
Page 21
- Review of Sampling and Analytical Procedures
- Institutional/Legal Background
- Costs of Sludge Disposal and Reuse Options
Exposure and effects of contaminants of concern will be assessed, as
will risks, costs, and benefits. An evaluation of regulatory and econo-
mic Impacts will be a final step, leading to sludge management guidelines
and establishment of EPA sludge management policy. In addition, there
will most likely be recommendations for follow-up actions, such as addi-
tional research needed.
This workshop is intended to contribute to the Task Force efforts,
as well as give us 1n the research area some sound guidance concerning
the critical technology and sciences areas needing additional study or
development efforts.
In closing, I want to express my appreciation for your assistance to
EPA and other federal agencies in resolving the complex Issues and tech-
nical problems surrounding the use of the land for waste management.
Wastewaters and sludge must be applied to the land as a principal manage-
ment method, but only in an environmentally acceptable manner. Your
assistance will be invaluable in reaching a workable approach. I know
that you will work to make the next two days as productive and meaningful
as the 1973 workshop. I offer you my encouragement toward that end.
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Page 23
NECESSITY OF REGIONAL RESEARCH
Raymond J. Miller
Dean and Director, College of Agriculture
University of Idaho
Moscow, Idaho
Any program that deals with land, particularly agricultural lard and
what happens when wastewater or sludge is added to those lands 1s going
to involve agricultural researchers.
Over the last year or so you have probably read or seen several
reports on the strengths and weaknesses of agricultural research. I do
not recall any of these reports talking about one of the real strengths
of the agricultural research system in this country. That is regional
research. Each state agricultural experiment station in the Land Grant
Universities receives funds from U.S.D.A. These come to the states by
formula through the Cooperative State Research Service, Of these funds
at least 25% must be spent on Regional Research. This requirement and
the resulting cooperation are unique to CSRS, the State Agriculture
Experiment Station, and to this country. These few dollars result in a
planning research process and system that results in programs and accom-
plishments that could be obtained in few if any other way. In addition
it brings in scientists from other agencies, such as ARS.
Let me use one example, granted an excellent example of a regional
project to explain the benefits. That is W-124, Optimum Utilisation of
Sewage Sludge on Agricultural Land.
This project started 5 years ago 1n the 12 western states. Since
the objectives were similar to those of a project 1n the North Central
region, NC-118, the two projects were combined into one, W-124. Subse-
quently, the membership was expanded to include the Northeast and the
South. So it is really a national project. This project also Includes
scientists from ARS, EPA, and SCS.
One of the objectives of the project was to obtain data that would
provide some uniformity and therefore comparability across the U.S. This
project put in place a program that used a common sludge, Chicago, which
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Page 24
MILLER
was supplied by EPA and Chicago, applied at standard rates in 14 states,
using a common crop - barley. Five years data will be collected. Data
from 16 soil types and for 5 heavy metals (cadmium, copper, zinc, lead,
and nickel) and their concentration in the foliage and grain will be
obtained. In addition, they will have data on nitrogen and phosphorus
availability, nitrogen mineralization and carbon cycling.
This data will be published as a regional publication, making avail-
able a large data bank which can be used as a standard across geophysical
and geoclimatic zones in the U.S. In addition, appropriate parts of the
information will be published 1n professional journals.
Where else could you put together such a comprehensive program to
obtain so much data, and do it with a minimum of overhead. A relatively
small number of dollars 1n the right system have generated a large, well
planned and coordinated program. This project has brought together one
of the best groups of soil chemists in this country.
An excellent system - regional research.
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POSITION PAPERS
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INSTITUTIONAL CONSTRAINTS
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Page 29
INSTITUTIONS CONSTRAINING THE
UTILIZATION OF MUNICIPAL WASTEWATER
AND SLUDGE ON LAND
D. L. Forster and D. D. Southgate
Department of Agricultural Economics and Rural Sociology
The Ohio State University
Columbus, Ohio
ABSTRACT
The variety of social and regulatory constraints on land
application programs identified in the literature 1s reviewed in this
paper. Also summarized are the results of a survey of commities that
have mounted such programs. Only a small minority of the surveyed
communities identify institutional factors as being resDonsible for
seriously limiting the expansion of their respective programs.
INTRODUCTION
Among the conclusions reached at the 1973 Conference on Recycling
Municipal Sludges and Effluents on land was that "unless political and
Institutional constraints on the land application of effluents and
sludges are recognized, Identified, and resolved, (land application)
projects will likely fall, regardless of their technical, scientific,
and economic feasibility" (NASULGC, 1973, p. 232). A variety of poten-
tial social, legal, and regulatory constraints were Identified. Among
them were unfavorable public attitudes toward landspreading activities,
a variety of local and state regulations that apply to those activities,
as well as the sometimes ambiguous nature of the legal regime within
which sludge and effluent landspreaders must function.
The past decade's experience has served to emphasize that social,
legal, and regulatory environments are of primary concern to municipali-
ties contemplating a land application program. All of us can think of
recent Instances where a technically sound program had to be scuttled
because it could not overcome the opposition of a county health board, a
township council, a state environmental protection agency, or a group of
concerned private citizens.
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FORSTER AND SOUTHGATE
The past decade was also a period of time when the Incentives to
initiate or expand land application activities grew. Federal laws
encouraged its use. Changes in environmental regulations limited the
use of other sludge and effluent disposal options. Skyrocketing energy
prices reduced the economic attractiveness of incineration and other
methods. At the sane time, fertilizer price increases and the rising
cost of water {both of which were caused largely by energy price hikes)
heightened the interest of potential participants in land application
p rograms.
This changing structure of incentives has enhanced the interest of
communities in the social, legal, and regulatory constraints to land
application. Recent literature has established the types of instito
tional constraints that have been encountered by communities. Section
II of this paper uses that literature to define the concept of
"Institution" and to identify a taxonomy of institutional constraints.
In Section III, an attempt is made to document effects of some of the
past decade's institutional changes. Also identified are the likely
impacts of federal regulation of land application and of the effec-
tiveness of campaigns designed to win public support for landspreading.
Finally in the fourth section, some implications for the design of both
landspreading programs and public policy dealing with those programs are
identified. Also discussed there are the needs for additional study of
the Institutions constraining the utilization of wastewater and sludge
on land.
INSTITUTIONS FACING LAND APPLICATION
An Institution is defined as a collective action in control of
individual action (Commons, 1934). Institutions include family, econo-
mic sphere (e.g. union or business), bureaucracy, and other social
groupings and the behavioral norms of these groupings (Gordon, 1980).
In a sense, attitudes and the more formal rules of society are a product
of social institutions to which individuals conform.
Institutions tend to be static, Inherited from the past, dic-
tatorial, and creatures of habit. They Inhibit change. However, new
Institutions evolve as society re-evaluates its rules and norms in light
of new technology (Gordon, 1980).
Attitudes and formal rules toward land application of municipal
wastewater and sludges are the Institutions dictating the use of this
technology. These Institutions tend to be Inherited, governed by habit,
dictatorial, and difficult to change. However, land application tech-
nology has changed and continues to change. It forces changes 1n these
static Institutions. Thus, the Institutions we describe today will be
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Institutional Constraints
Page 31
replaced tomorrow with new ones. Whether they will be nore favorable
toward land application remains to be seen. That will be determined by
those who lead society in its evaluation of this changing technology.
Constraining Attitudes
1. Concern about health risks including pathogens, parasites,
metals in food chain: Probably the most constraining attitude is that
land application of wastewater or sludge adversely affects public
health. Concern is expressed over cadmium, lead, and some organic com-
pounds entering the food chain or being directly injested. The possibi-
1 ity of pathogenic organisms and parasitic ova being distributed by land
application also is discomforting.
The available literature suggests that little hazard confronts
sewage plant workers. No demonstrated hazard has been documented for
communities adjacent to well managed land application systems (Burge and
Marsh, 1978; Uiqa and Crites, 1980). Yet the public intuitively
suspects that land application systems are unsafe. Public opposition is
usually the strongest when health risks are perceived to be present.
Since most people are risk averse, opponents of land application can
often thwart programs by rousing the community with the idea that land
application might be unhealthy. If the safety of land application is
suspect, there is little chance of gaining public support regardless of
its other merits (Bruvold, 1972).
2. Concern about the environment: Concentrations of zinc,
copper, nickel and industrial organic compounds may be present in
wastewater and sludge. There is the fear that these could accumulate in
the soil and become toxic to crops. High salinity in some wastewater
may also present long run problems to arid soils. Excessive applica-
tions of wastewater nitrogen may cause leaching of nitrogen to
underground water supplies. Land application near streams or lakes may
result in runoff of nutrients, metals, and organics to surface water
supplies.
Well managed systems can avoid these problems. Low application
rates and proper placement of wastewater and sludges can assure that
land application does not threaten the environment. However, the public
may perceive potential environmental damage, and that perception can
disrupt the most environmentally safe land application program.
3. Concern about nuisances: Odor is the primary concern.
Sludge and wastewater are considered to be foul-smelling and capable of
threatening the surrounding community with an odor nuisance. Other
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FORSIfcH AND SOUTHGATE
potential nuisances are the damage to roads by trucks and equipment,
sludge spills, and the perception of the neighborhood as a "dumping
ground."
4. Concern about land values: Threats to the cornmnnitv' s
health and environment and the threat of nuisances would disrupt the
land market. Residential and commercial land prices would plummet. The
wealth of most land owners in the community would diminish. Opponents
of land application can easily paint a grim picture of economic ruin for
the community due to the threat of nuisances, health risks, and environ-
mental damage. Only the possible threat need exist for the most safe,
well managed land application to be met with stiff resistance from the
community.
5. Historic precedents which shape attitudes: From the 1840's
to the 1900's, fears of disease and epidemics pushed communities to
adopt waste treatment technologies. Land treatment was the initial
technology adopted and was responsible for sharply reducing death rates
(Jewell and Seabrook, 1979). In Europe, a trend away from land treat-
ment developed in the late 1800's and early 1900's. Expanding towns put
Increased loads on land treatment systems, and populations moved closer
to the "sewage farms." Sewage treatment technologies such as sedimen-
tation, chemical precipitation, and screening were developed for land
application systems. Later these technologies were combined with per-
colating filter and activated sludge methods to replace land treatment.
Europe, in the last part of the 1800's adopted a philosophy of par-
tial treatment of effluents rather than the complete treatment offered
by land treatment. In the United States, this philosophy was soon
widely accepted due to the distribution of the population and availabi-
lity of large quantities of water near most cities. By the 1920's in
the United States, land treatment had been replaced by other treatment
methods which emphasized partial treatment of effluents (Jewell and
Seabrook, 1979).
Today, land treatment of wastewater comprises only a small propor-
tion of the municipal waste treatment. In 1975, total municipal
wastewater discharges in the U.S. amounted to 90.8 x 10 m3/day (24
billion gallons per day). Wastewater treatment totaled only about 0.7
billion gallons per day (Asano and Madancy, 1982). Land application of
sludge is more widely accepted than 1s wastewater treatment. Still In
1979, only 31 percent of the nation's municipal sludge was landspread.
Incineration and landfilUng stabilized sludge accounted for 22 and 29
percent, respectively. Ocean disposal comprised about 12 percent of the
total (Walker, 1979).
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Institutional Constraints
Page 33
Given that attitudes tend to be creatures of habit and Inherited
from the past, it should be no surprise that the attitudes of the public
sanitary engineers and public officials are less than favorable toward
1 and application.
6. Cultural influences: There are general attitudes regarding
land application which prevail over nearly any community. Women are
less accepting of land treatment than are men (Musselman, et al., 1980;
Olson and Brunold, 1982). Due to women's traditional role as the one 1n
the family responsible for the family's health and cleanliness, it is
not surprising that they are more reluctant than men to accept a prac-
tice with possible health risks.
Age is negatively correlated with acceptance (Musselman, et al.,
1980; Olson and Bruvold, 1982). Most new technologies are accepted less
readily by the old, and land application is no exception.
Formal education is positively correlated to acceptance (Olson and
Bruvold, 1982). Especially when a person's formal education stops at
less than twelve years, land application is more likely to be dis-
favored. Exposure to new ideas 1s a product of education, and this
exposure generally leads to greater acceptance of new technologies.
Experience or exposure increases acceptance. Those who have
experience with land application are much more receptive than those who
have no experience. Similarly, those who are exposed to land applica-
tion concepts through educational programs are more favorable toward it
than those with limited exposure (Musselman, et al., 1982).
7. Farmer attitudes: A successful land application program
usually requires acceptance by the farm community. The following atti-
tudes are characteristic of farmers and may affect land application
programs.
Farmers exhibit a strong inclination toward short run economic
gain (Napier, et al., 1980). This 1s a double edged sword for land
application orograms. On the one hand, 1t means that fanners are likely
to adopt land application when there are short run economic benefits.
On the other hand, 1t may encourage practices which are not conducive to
long run soil productivity. For example, the threat of excessive metal
accumulation ten or fifteen years from now might provide little incen-
tive for lower sludge application rates.
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Page 34
FORSTER AND SOUTHGATE
Farmers perceive themselves to be stewards of the land (Napier,
et al., 1980). While this attitude may be contradictory to the previous
one In some situations, farmers consider themselves to be stewards of
natural resources for future generations. This attitude can assist in
the development of a responsible land application nrogram when measures
to assure an environmentally safe program are made known to fanners.
Farmers oppose laws or regulations which impose land use controls.
They feel they should have the right to determine how to use their land.
Zoning and other land use control options can be expected to be met with
stiff opposition (Napier and Mast, 1981).
Farmers strive for Individualism. There is a strong urge to adhere
to self sufficiency. Also, they are conservative; there is a reverence
for traditional values. Finally, farmers tend to hold strongly to an
"agrarian Ideology" (Rohrer and Douglas, 1969). This agrarian Ideology
is composed of the proposition that all nonfarm occupations rely on far-
mers for sustenance; there 1s no like dependency for farmers. Another
proposition of the agrarian ideology 1s that farm or rural life is
"better" or "more natural" than urban life.
These attitudes - individualism, conservatism, an agrarian
ideology - lead to the often expressed view that municipal waste is an
urban problem. The problem ought to be solved in the city by those
creating the waste and not by pushing 1t off on rural communities.
Opponents to land application can successively Impede a well designed
program by turning these attitudes against land application.
8, Municipal officials' attitudes: There is a bias against
land application on the cart of those responsible for waste treatment
(Jewell and Seabrook, 1979). Due to the historic evolution of waste
treatment, municipal officials and the technical community are unfami-
1 1ar with land treatment. For the past half century, waste treatment
texts have Ignored or only briefly mentioned land application. Waste Is
considered a disposal problem, not a resource recovery problem.
Also, municipal officials usually underestimate the community's
acceptance of land application (Olson and Bruvold, 1982). When a land
application system is proposed, officials are more likely to be
confronted by those expressing negative views than those in favor.
Thus, officials tend to overestimate the opposition to land application.
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Institutional Constraints
Page 35
Regulatory and Legal Constraints
Federal legislation has encouraged land application and generally
has refrained from placing constraints on it. The Federal Water
Pollution Control Act Amendments of 1972 (PL 92-500) encouraged the
recycling of potential sewage pollutants through the production of agri-
cultural, silvicultural, or aquacultural production. It also contained
provisions which require consideration of "appropriate alternative waste
management techniques," such as land application, in order to receive
federal grants. The 1977 Clean Water Act further encouraged the use of
"innovative and alternative" technologies such as landspreading.
EPA has encouraged the consideration of land application through
Its construction grants program. It is in the process of finalizing a
set of regulations for land application and is developing proposed regu-
lations to govern the distribution and marketing of sludge. Generally,
these proposed regulations are intended to encourage responsible, well-
managed land application systems.
However, the lack of final land application regulations may be
impeding progress in developing new land application systems.
Communities may be using a wait and see attitude until final regulations
are issued.
State legislation and regulation is less supportive of
landspreading. In nearly every state, at least one form of license or
permit is required. Several agencies, each with different regulations,
may be involved where land application 1s thought to affect water
quality, food production, and air quality (Deese, et al., 1980). At
least thirty-one states have issued guidelines or regulations concerning
land application. Most of the remaining states approve land application
on a case by case basis (Morris and Jewell, 1977).
State regulations often constrain the land application of
wastewater since they usually require the secondary treatment of waste
prior to land application. When secondary treatment 1s required, land
application of wastewater can not be cost effective when compared with
conventional treatment systems (Morris and Jewell, 1977).
State and local regulations or guidelines may Incorporate permit
requirements, application rate restrictions, wastewater or sludge analy-
sis requirements, monitoring requirements, maximum concentrations of
metals, nitrogen, and organic*, and land use restrictions. While these
may appear to be constraints, they are usually established as "rules of
the game" for responsible, well-managed programs to achieve safe land
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Page 36
rOHSTER AND SOUTHGATE
application programs. They are intended usually to constrain only those
which might detrimentally affect human wealth or the environment.
Other local constraints may include zoning or other land use
controls, health codes, and nuisance laws. These can be effectively
used by opponents to delay or completely block the best planned land
application program. To assure a successful program, local public
officials' attitudes must t>e assessed early* Their attitudes, like
those of the public at larqe, may need to be changed before a program is
v iable.
The method of land acquisition may provide constraints to the land
application program (Christensen, 1982). Land may be purchased and held
in fee simple ownership by a community. While this insures a long term
planning horizon, it usually festers local opposition. The community
purchasing a "sludge farm" is likely to raise the ire of neighboring
land owners. Also government purchase can result in the local property
tax base beinq reduced and the community's land owners havinq a heavier
property tax burden (Walker, 1979). Another method of acquiring land is
by purchasing an easement or a portion of the bundle of ownership
rights. Commuruties might purchase the right to use land for sludge
application during certain months of the year, for example (Christensen,
1982). The use of easements might provide a long run planning horizon
needed for the community, yet leave the land in private ownership.
However, the temporary use of privately owned land is the most common
method of land acquisition. Some communities pay land owners for the
temporary use of land, but most are allowed to land apply sludge or
effluent without charge.
While the land acquisition method has a bearing on the success of a
land application program, it is not crucial. More important is the
working relationship between the community and rural residents and
landowners (Christensen, 1982). Antagonism between these parties can
destroy a program even though tight legal provisions have been
established.
Finally, management of the land application site may present
constraints to program acceptance. Poorly trained operators, odorous
conditions, high application rates, and little information about sludge
or wastewater content almost guarantee problems. Transporting from one
legal jurisdiction to another multiplies potential legal constraints and
public acceptance problems. Use of sludge and wastewater near residen-
tial areas is likely to generate opposition. Public opposition is
highly correlated with land use intensity near land application sites
(Deese, et al., 1980; Olson and Bruvold, 1982).
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Institutional Constraints
Page 37
Lessons About Changing Institutions
Communities can influence public acceptance, but they can not
control it. Even the most well planned program may face too many insti-
tutional rigidities to succeed. The following lessons can help, not
guarantee, the break down of institutional barriers by changing atti-
tudes.
The public needs to be involved in the decision making process. In
a program's early stages, ideas need to be developed, the attitudes and
potential support of affected groups assessed, and rapport with influen-
tial individuals established (Donnermeyer, 1977; Dotson, 1982; Ellis and
Disinger, 1981; Stitzlein, 1980). The public is then involved in making
decisions concerning wastewater or sludge use. Problems are discussed,
information is disseminated, alternatives are developed and analved
and the public participates 1n decision making. During this process
technical and economic data need to be communicated effectively and
understandably to the lay public. Avoided is the "public hearing" model
which takes the form of a "we-they" winner-take-a11 battle between
wastewater treatment officials and rural residents. Rather, seminars
and workshops are scheduled with several small groups to allow favorable
group dynamics to operate (Ellis and Disinger, 1981).
Incentives need to be clarified continually. The economic justifi-
cation of a land application program needs to be emphasized. It is pro-
bable that agriculture benefits from receiving wastewater or sludge, and
the community benefits from the relatively low cost of land treatment.
The size of these benefits needs to be assessed and made public early
(Deese, et al., 1980).
Odor, health and environmental issues need to be addressed early
and with vigor. Treatment plants must resolve odor problems or a land
application program likely is doomed. Demonstration sites can be used
to show the lack of odor. Experts from the agricultural community need
to assess the proposed program and Identify the soils, application
rates, and wastewater or sludge contents which provide an environmen-
tally safe program. Public health officials need to evaluate the
program and assure the public that the program will not be detrimental
to local health or to the food chain.
Advisory groups can be established to facilitate public involve-
ment. Roles which these groups might fill Include helping pick suitable
sites, bringing farmers and rural residents Into planning, promoting the
Idea that wastewater or sludge 1s a resource out of place, pointing out
local problems or probable constraints, and scrutinizing the programs'
technical and management aspects.
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Page 33
"ORSTEfl AMD SOU SGATE
An education program car remove much of the communities opposition
(Deese, et al., 1980; Dotson, 198?; Ellis and Qisinger, 1981; Musselman,
et al., 1980). Complete and unhiased information needs to be nade
available through a wide variety of techniques. Forums for public edu-
cation might include seminars and workshops with concerner] citizens,
lectures to community groups, tours of the wastewater treatment plant
and land application sites, newspaper articles, television and radio
irte-vfews. Written ratertelj varying in scope from brief brochures to
university purM icat^cns, should ae mate ^vailas'e, The U.S. EFA, state
agencies., anc renv 'aid grant cclieijes tisve tMs hfritteri material
available. Mso, svailasle *rcm these sources, are films anc ta3es con-
cerning land application.
Management of tie land application program needs tc constantly
focus on winning and maintaining public acceptance. Land application at
sites removed from residential areas; sludge, wastewater, and soil ana-
lysis prior to application; monitoring sites often after application;
well kept records; low application rates; soil incorporation of odorous
sludges; responsible vehicle operators; clean vehicles; and cleaning up
application sites and roads are some of the practices which can help win
public acceptance.
Written agreements between the community and landowners should be
used when private landowners are involved. The purpose of these
agreements is to minimize future misunderstandings. Application rates,
sludqe or wastewater quality, method and time of application, and legal
liability should be clarified.
THE INSTITUTIONAL ENVIRONMENT CONFRONTING
A SAMPLE OF LANOSPftEA&INS COMMUNITY
During the past ten years, rising energy prices, increasing water
scarcity, and certain changes in the regulatory environment promoted
increased reliance on land application as a sludge and effluent manage-
ment technique. If anything, these charges have increased the impor-
tance of institutional constraints on the growth of land application
programs. In order to gain a preliminary idea of the role played by
those institutional constraints during the past decade, a mail survey of
communities that now have a land application program, have had such a
program, or have expressed an interest in mounting such a program was
conducted. Some results of that survey are summarized in this section.
During t^ne latter part of 1982, the authors of this paper collected
a sample of 177 U.S. communities. Sources contacted during this sample-
building process include regulatory officials, cooperative extension
personnel, and others who are knowledgeable about land application ip
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Institutional Constraints
Page 39
their respective states or regions. Questionnaires to be used in the
survey were reviewed by university researchers and municipal officials
in the state of Ohio. The initial mailing of the questionnaires
occurred in November, 1982. After a follow-up mailing about three weeks
later, 110 questionnaires (equal to 62 percent of the original sample)
had been returned.
The sample includes a large number of communities from states such
as Ohio, Michigan, and Illinois, where sludge 1andspreading is more com-
mon, as well as quite a few cities and towns from California, where land
application of effluent is widespread. In addition, one-half of the
communities had a 1982 population of less than 25,000; over four-fifths
of them had populations of less than 100,000 in 1982. One might keep in
mind these two characteristics of the sample when reviewing the results
reported below. For example, a midwestern or southwestern town located
in an agricultural area might have an experience with local institu-
tional constraints that is vastly different from the local institutional
constraints facing a land application community in a more densely popu-
lated, less agricultural region, such as New England.
Resides collecting basic information on community size, wastewater
treatment and sludge management practices, etc., the survey instrument
was designed to answer the following questions:
- What have been the trends in state and local regulation of land
application during the past decade?
- Have institutional constraints played a large role in limiting
the expansion of land application programs?
- What are municipalities' perceptions of the impacts of future
institutional change?
- What role do public relations campaigns play in promoting the
success of a land application program?
Changes in Legal and Regulatory Constraints
It is fair to say that major changes in the legal environment for
1 andspreaders occurred during the past decade. Local regulations (e.g.,
permit requirements, limitations on sites and applicaion rates, etc.)
were practically non-existent in 1972. Only 10 percent of the sample
recalls encountering such regulations ten years ago. By 1982, though,
over 60 percent of the communities reported that their own or neigh-
boring jurisdictions had adopted regulations. This percentage is higher
in the northeast and in California. It is interesting to note, however,
that local prohibitions have been encountered by relatively few of the
communities in our sample. Evidently, even where local communities feel
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FORSTER AND SOUTHGATE
strongly enough about land application to consider regulating it, they
are still willing to accept a well-managed land application program.
State regulation of land application programs were encountered by
just 40 percent of the communities in 1972. By 198?, however, more than
four-fifths of the surveyed communities reported that state law com-
pelled them to obtain permits from the state and to conform to land
application guidelines established by state agencies. Thus, the states
are now the major sources of rules and regulations covering land appli-
cation.
Effects of Regulatory Change
Establishing that a major change in legal institutions occurred
between 1972 and 1982 does not necessarily prove that it has greatly
constrained the expansion of land application. Economic concerns seem
to have motivated communities to move forward with a land application
program. Our sample was asked to rate the importance of a variety of
factors affecting the decision to initiate or to expand such a program.
The relatively high cost of other sludge disposal methods was identified
as the most important of these factors.
large; the commumties that had expanded their programs
reported that most groups (owners of land application sites, neighbors
of those sites, environmental groups, government officials, etc.) were
irlSSfn at t^te very 1east' neutral about that expansion
Indeed at ^nce» neither social nor legal constraints seem to
have played a major role in many communities' decisions to downscale or
to avoid increasing land application. (Approximately 25 municipalities
respondmg to our survey reported making such a decision.) High
sludge/effluent transportation costs and lack of 1 and application sites
were the reasons given most often for such a decision.
Let us note, however, that there might be institutional constraints
underlying these two technical" or "economic" reasons. For example,
local opposition might have forced some communities to rely on more
distant application sites.
Impacts of Future Institutional Change
We have noted that state governments currently set most of the
rules governing land application. Increased federal regulation has been
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111sti*i j 11on.i Lonslrainls
Page 41
debated for several years. We were interested in eliciting the munici-
palities assessment of the likely impacts resultinq from federal regula-
tion.
Our survey indicates that knowledge of proposed federal standards
is highly imperfect. However, the answers to our questions sugqest that
community officials disagree with those who argue that the existence of
federal standards would greatly ease the task of winning public accep-
tance for a land application program. Also, whereas relatively few
officials fear that promulgation of federal regulations would put their
1 andspreadinq proqrains out of business, the great majority of them doubt
that those regulations can be designed with enough flexibility to take
special local conditions into account. On balance, then, one cannot
infer from our survey results that there is strong support among
1andspreadinq communities for federal regulation of land application.
Role of a Public Relations Campaign
Over time, a "conventional wisdom" has stressed the need for com-
munities to mount an educational effort in order to win public accep-
tance for landspreadinq programs. It might be interesting to note that
only sliqhtly more than one-half of the communities expanding their
landspreadinq programs report the use of an educational campaign. Of
course, this survey result might be somewhat misleading in that one com'
munity can benefit from some other community's or agency's public rela-
tions efforts. Among the nore effective educational methods identified
by the operators was field demonstration plots.
Summary of Survey Results
This survey supplies only preliminary answers to questions dealing
with landspreaders' institutional environments and how those environ-
ments can be or might be changed. However, one survey result suggests
that institutional constraints have not proven to be a significant
barrier to most communities wishing to expand land application. In
1972, practically all surveyed communities applied their sludge and
effluent to idle land owned by the public sector. Most communities
reported that, in 1982, better than half of their sludqe and effluent
was spread on privately-owned land and that the greater part of acreage
used in land application programs was pasture or cropland. This result
might be due to a lack of publicly-owned land to support expanded land
application programs. More likely is that public attitudes toward this
disposal option have changed markedly, thereby allowing for expansion of
well-managed land application programs.
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FORSTER AND SOUTHGATE
IMPLICATIONS
Land application of wastewater and sludge has expanded over the
past ten years due to technological and economic forces. Further expan-
sion is expected. Institutional constraints have increased with proli-
ferating federal, state, and local government intervention.
But institutions tend to be static and creatures of habit. As a
technology begins to be adopted, institutional constraints are expected.
These institutional constraints include public attitudes and a society's
formal rules. Public attitudes constraining land application are con-
cerns about health risks, the environment, nuisances, and land values.
These attitudes are shaped by historic precedents and cultural influen-
ces. Farmers' and municipal officials' attitudes also are constraining.
Society's formal rules include federal, state, and local regula-
tions. While federal legislation has encouraged land application, some
state and local regulations have hampered it. Land use controls, health
codes, and nuisance laws have been used at the local level by opponents
to frustrate land application. Some land acquisition and management
strategies have negatively affected land application in communities.
The existence of these institutional barriers inhibit the growth of
land application. Institutions frustrate efforts to change and can be
expected to construct barriers to change. An important issue is how to
build public acceptance that will accomodate an emerging technology like
land application. A host of methods are available to build public
acceptance. They include public involvement in the decision making pro-
cess, clarification of incentives for land application, resolution of
odor, health, and environmental problems, establishment of advisory
groups, aggressive educational programs, and responsible management of
land application,
Our survey results indicate that landspreading communities have
witnessed substantial growth in state and local regulations during the
past decade. In spite of (or possibly because of) this expanded regula-
tory framework, communities have been able to respond to the economic
incentives that are favorable to land application. The public has been
generally supportive of this treatment method. The majority of com-
munities have used educational or public relations campaigns to enhance
this support. The legal and regulatory frame-work has not been per-
ceived as limiting. However, there is no strong support for new federal
regulations.
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Institutional Constraints
Page 43
Future research in this area should center around the question of
how acceptance of a safe, well-managed land application program can be
better assured. How can programs be designed to win public acceptance?
The difficulty of this research is that cultural influences, historic
precedents, and public concerns change from community to community.
Thus, programs designed to win public acceptance differ across the
c ountry.
Other future research should address the formal rules and regula-
tions being adopted. Are state and local regulations sufficient to
assure safe land application programs? What rules artd regulations could
be designed to encourage safe, well-managed programs? How can these
rules and regulations be made flexible to accommodate special local con-
ditions and future change?
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Page 44
rORS'TER AND SOUTHGATE
REFERENCES
1. Asano, T. and R. S. Madancy. 1982. Water reclamation efforts in
the United States, p. 277-291. J_n E. J. Middlebrooks (ed.).
Water Reuse. Ann Arbor Science Publishers, Ann Arbor, MI.
2. Bruvold, W. H, 1972. Public attitudes toward reuse of reclaimed
water. Contribution No. 137. University of California, Water
Resources Center, Berkeley. 54 p.
3. Burge, W. D. and P. B. Marsh. 1978. Infectious disease hazards of
1 andspreading sewage wastes. Journal of Environmental Quality
7:1-9.
4. Christensen, L. A. 1982. Irrigating with municipal effluent: a
socioeconomic study of community experiences. ERS-672. U.S.
Department of Agriculture, Washington, D.C. 49 p.
5. Commons, J. R. 1934. Institutional economics. University of
Wisconsin Press, Madison, WI.
6. Deese, P. L., J. R. Miyares, and S. Fogel. 1980. Institutional
constraints and public participation barriers to utilization of
municipal wastewater for land reclamation and biomass production.
Report to President's Council on Environmental Equality.
7. Donnermeyer, J, 1977. Socio-cultural factors associated with the
utilization of municipal waste on farmland for agricultural pur-
poses. p. 154. In C. E. Young and D. J. Epp (ed.). Wastewater
management in rurTT communities; a socio-economic perspective.
Institute for Research on Land Water Resources, Pennsylvania State
University.
8. Dotson, K. 1982. Public acceptance of wastewater sludge on land.
U.S. Environmental Protection Agency, MERL, Cincinnati, OH.
9. Ellis, R. A. and J. F. Disinger. 1981. Project outcomes correlate
with public participation variables. Journal of Water Pollution
Control Federation 53:1564-1567.
10. Gordon, W. 1980. Institutional economics, the changing system.
University of Texas Press, Austin.
11. Jewell, W. J. and B. L. Seabrook. 1979. A history of land
application as a treatment alternative. EPA 430/9-79-012. U.S.
Environmental Protection Agency, Washington, D.C. 83 p.
12. Morris, C. E. and W. J. Jewell. 1977. Regulations-and guidelines
for land application of wastes - a 50 state overview, p. 9-28,
In R. C. Loehr (ed.). Land as a waste management alternative. Ann
Arbor Science Publishers, Ann Arbor, MI.
13. Musselman, N. M., L. G. Welling, S. C. Newman, and 0. A. Sharp.
1980. Information programs affect attitudes toward sewage sludge
use in agriculture. EPA-600/2-80-103. Environmental Protection
Agency, Cincinnati, OH. 51 p.
14. Napier, T. L., B. Kohl, D. 0. Hansen, and G. Hooks. 1980. Rural
life and farmers attitudes; an Ohio survey. Research Circular 260.
Ohio Agricultural Research and Development Center, Wooster, OH.
15. Napier, T. L. and D. S. Mast. 1981. Attitudes toward land use
controls within a multi-ethnic county of Ohio. Journal of the
Community Development Society 12:103-122.
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Institutional Constiamts
Page
16. National Association of State Universities and Land Grant Colleges
1973. Proceedings of the Joint Conference on Recycling Municipal
Sludges and Effluents on Land. NASIILGC, Washington, D.C. 244 p.
17. Olson, B. H. and W. Bruvold. 1982. Influence of social factors
on public acceptance of renovated wastewater, p. 55-73. _ln_
E. J. Middlebrooks (ed.). Water reuse. Ann Arbor Science
Publishers, Ann Arbor, MI.
18. Rohrer, W. C. and L. H. Douglas. 1969. The agrarian transition i
America: dualism and change. Bobbs-Merri11 Co., Inc., New York.
19. Stitzlein, J. N. 198CI. Public acceptance of land application of
sewage sludge. _I_n Utilization of wastes on land: emphasis on
municipal sewage. U.S. Department of Agriculture, Washington, D.C
20. Uiga, A. and R. W. Crites. 1980. Relative health risks of acti-
vated sludge treatment and slow rate land treatment. Journal of
Water Pollution Control Federation 50:2865-2874.
21. Walker, J. M. 1979. Overview: costs, benefits, and problems of
utilization of sludges, p. 167-174. Jn_ Proceedings of eighth
national conference on municipal sludge management. Miami Beach,
FL.
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Page 46
FORSTER AND SOUTHGATE
QUESTIONS AND COMMENTS FROM THE FLOOR:
Susan Young, INCOG, Tulsa, OK: Have you developed any feel for
public attitudes toward state regulators and regulations? U.S. Federal
regulators and regulations? (e.g, More confidence in state agencies or
federal agencies?)
D. Lynn Forster: The confidence in local, state or federal regula-
tors depertdes directly on how much credibility these regulators have with
the public. The public is reluctant to grant credibility when regulators
have positive attitudes toward new technologies (e.g., 1 andspreading)
which promise change. Probably the safest methods for regulators to win
public confidence is to support the status guo, to maintain credibility
by trying to avoid change. Of course this incentive to avoid change is
the problem with any regulatory approach. Regulators supportive of
change find gaining credibility to be an uphill battle.
Betty H. Olscm, University of California, Irvine: 1. What would be
the drawbacks of not having consulted the directors of the controlling
agenaies in the results of the survey?
Lynn Forster: Local community decision makers were included in the
sample. We felt they were likely to have the best perspective on their
local situations.
Betty H. Olson: 3. What is the single most important factor in
determining acceptance of land application?
Lynn Forster: From the community's perspective, economics is the
single most important factor. For the public at large, concern about
health risks seems to be the most often expressed. Of ourse, this con-
cern, as well as other concerns, may be a guise for concern about the
impacts of land application on property values.
Betty H. Olson: 3. How do you deal with influential individuals
who are elected and very much controlled by the electorate?
Lynn Forster: These individuals must be brought into the decision
making process early. They should be involved as problems are discussed,
information is disseminated, and alternatives are developed.
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Institutional Constraints
Page 47
Ebba Lund, Royal Veterinary and Agricultural University,
Copenhagen, Denmark: In your very interesting presentation, it seems
that you left out the aspect that land application is not a new idea.
For instance, the French literature published more than a century ago,
contain the same problems and discussions. Many European countries have
had systematic application programs for a century. It seems that the
important new factors are the population growth and the difficulties in
finding suitable application sites. In Denmark, in spite of careful stu-
dies, it is not Jtnown what happens to half of the sludge produced. How
is the U.S. situation? It seems important when we consider further land
application to "know when sludges are now being applied. Perhaps without
being registered.
Lynn Forster: In many communities, land application programs have
been mismanaged. Application rates have been excessive. Sites have been
poorly chosen. Recordkeeping has been nonexistent. In some communities,
public giveaway programs have been an Important disposal methods. In
these programs, control over sludge use is completely lost. You are
correct in saying that in many communities there has been incomplete
knowledge of where sludge has gone.
Merry L. Morris, New Jersey Department of Environmental Protection;
Since we are largely dealing with the issues of distrust and credibility
(or lack of it), has your study indicated which groups (federal govern-
ment, state government, county officials, local officials, extension
agents, Soil Conservation Service personnel) have credibility? Clearly
technical information from a source without credibility will not go far
to allay public fears.
Lynn Forster: Our survey did not address the topic of credible
sources. However, 1t 1s our experience that agricultural Institutions
are perceived as a credible information source. Personnel from land
grant universities, Cooperative Extension Service, and Soil Conservation
Service seem to have a high degree of credibility.
Stephen Campbell, BIOGRO Systems, Annapolis, MD: 1. Sludge
disposal low bid contract type work creates shortcuts and reduced costs,
therefore, utilities or contractors don't do public relations. 2.
Public is not being properly educated - engineers and academians talk
over heads of average concerned citizens.
Kenneth Dotson, EPA,-MEBL, Cincinnati, OH: Who educates the public
is more important than the message or program in gaining public accep-
tance.
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Page 48
I OHS1LH AN!J SOiUNGATE
Donald B. Aulenbach, Rensselaer Polytechnic Institute: EPA has
pushed sewers and conventional treatment. Now, it is difficult to re-
indoctrinate the public into the use of land application where appli-
cable.
Regarding nuisance odors from land application, they are frequently
much less objectionable than the odors from nearby farms having hogs
(unless you are used to the odor of hogs).
Frank Rumenik, North Carolina State University: Your list of
constraining attitudes was excellent in serving to stimulate recognition
of problems faced in getting community acceptance. However, I suggest
that instead of health and environment being the prirmry concerns it is
really nuisance and land values which you listed as No. <7 and No. 4.
Then, because of preoccupation with these understandable personal
interests, either knowing or unknowing, strong arguments are mide on an
historical and cultural precedent as you noted in No. 5 and No.6. If
this is the case, then it ie most important to simply address nuisance
and land value concern and not overwhelm individuals or public hearings
with technical facts on health and environmental protection. Recognition
of the real issues, whether openly addressed or admitted, can allow more
meaningful public interaction and reduced tension. Sometimes the percep-
tion that data on health and environment are neded when the real issue is
nuisance and land Values causes discussions to get an different tracks
and then emotionalism and frustration often results. It appears that
another point is to emphasize that the relative risk-benefits of alter-
natives must be judged on an equal basis. The issue is not whether waste
ie to handled but what is the best alternative and these alternatives
must be evaluated on the same basis, either zero tolerance or a given
¦risk-benefit.
Jack L. Cooper, National Food Processors Association, Washington,
D.C.: I complement the preparers and presenters for the excellent
reports, and summarize my concerns as follows:
1. It is the perception of safety that is the major concern of food
processors. No matter how safe a particular disposal operation
may be, if it is portrayed as unsafe by the press and if the
public at large perceives it as being unsafe, food processors
accepting crops grown in sludge-amended soils could have their
reputations ruined.
2m Public involvement in decision making is very important. In
discussions with the public, special consideration should be
given to concerns of consumers of crops, particularly food
processors.
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Institutional Constraints
Page
3. Enforceable agreements are needed to assign legal responsibility
for actions and consequences of improper action.
4. Records of sludge, soil and crop testing, application rates and
sites, crops grown, etc,, must be kept and trade available to the
public.
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ENGINEERING AND ECONOMICS
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Page 53
ENGINEERING AND ECONOMICS OF APPLYING WASTEWATER
AND SLUDGE TO LANO
Charles E. Pound, Douglas A. Griffes, Ronald W. Crites
Metcalf & Eddy, Inc., Des Plaines, Illinois,
Metcalf 81 Eddy, Inc., Des Plaines, Illinois,
George S. Nolte and Associates, Sacramento, California
BACKGROUND
Land application of wastewater has been practiced for centuries
wherever waterborne waste transport systems were developed. Farming
with wastewater is the logical extension of the practice, thereby
resulting in a beneficial use of the water and nutrients. The practice
was introduced into the United States more than 100 years ago. General
interest in the subject waned after the turn of the century in favor of
more mechanized methods of wastewater treatment (1).
Interest in land application of wastewater, as reflected by the
number of references published, began to return in the 1960's (2). As
the scientific and engineering community again picked up the subject
they asked questions for which there were no documented answers. Studies
were initiated to answer some of the questions and included those
conducted by the faculties of Pennsylvania State University, University
of Arizona, University of California and others (3). Also, agencies
such as the U.S. Army Corps of Engineers (U5ACE), U.S. Department of
Agriculture (USDA) and the Federal Water Pollution Control
Administration (FWPCA) (forerunner of the U.S. Environmental Protection
Agency, USEPA} became interested in conducting or sponsoring
investigations into these subjects.
Concurrently, the practice of applying sludge derived from
municipal wastewater to land also was questioned. It seemed logical
that if the relatively few contaminants remaining in the wastewater
after the solid matter or sludge has been removed can cause problems>
surely the more concentrated sludge must at least be suspect.
Therefore, investigations into the land disposal of sludge also
increased in the 1960's.
The Clean Water Act Amendments of 1972 (P.L. 92-500) brought with
it a need to develop alternative technologies for treating and
disposing of wastewaters and sludges in an economical and
environmentally sound manner. This act further encouraged investigative
efforts into the land application of wastewater and sludges.
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POUND, GHIFFES AND CR:TES
It was with this background that the 1973 Research Needs Workshop
was held. Statements of current knowledge and areas of needed technical
information were developed that could be used as a guide for
establishing design constraints and for directing future research
activities (4). Over the next 10 .years a great number of research
activities were conducted to fill the data and information needs
outlined during the Workshop.
With the advent of the energy crises, came a change in conclusions
about the most economical sludge stabilization processes. The least
energy consuming processes quickly became the most interesting. This
resulted in the elimination of sludge incineration in most cases. This
change, coupled with the replacement of primary treatment plants with
secondary treatment plants, the reduction of marine sludge disposal
options, and the concern over sludge give-away programs for private use
contributed to ever increasing quantities of sludge.
The following paragraphs present an assessment of the needs at the
practical engineering community and the adequacy of the technical tools
currently available to meet the challenges presented by a dwindling
public works dollar and an increasing volume of wastewater and sludge.
To the practical engineer involved in the planning and design of land
application systems, it is not only important that specific technical
questions be answered, but that information be readily available,
concise, and in a useable form. Consequently, both research and
informational needs of the engineering community are addressed.
WASTEWATER APPLICATION
Resources available to the community for the planning and design of
wastewater application systems have advanced significantly over the past
decade. There is now a great deal of practical information available
concerning each of the three basic processes:
• Slow Rate (SR)
t Rapid Infiltration (R1)
• Overland Flow (OF)
State of Knowledge
In 1975 and 1976 a series of Technology Transfer seminars were held
and design criteria and case studies were presented. One of the first
documents developed and published was the "Process Design Manual for
Land Treatment of Municipal Wastewater" (5). Published in 1977, this
manual was prepared as a joint effort of the USEPA, USAGE and USDA.
Concurrent with this effort, other comprehensive engineering guidelines
were developed by other independent groups. Among the most notable of
these was a two volume engineering text prepared at Cornell University
(6).
Another important milestone occurred in 1978 with the International
Symposium on "State of Knowledge in Land Treatment of Wastewater" in
Hanover, New Hampshire (7). This symposium summarized the practical
aspects of land treatment and identified suitable approaches for design.
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Engineering and Economics
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The efforts of the last decade were culminated in the publication
of a second edition of the Process Design Manual in 1981 (8). The
revision was deemed necessary because of the large amount of research
data, design criteria and operating experience made available during the
four preceding years. Of particular importance were the results of EPA
long-term effects studies (9). The design approach of the manual is
essentially empirical, i.e., observation of successful performance
followed by derivation of criteria and mathematical expressions that
describe overall performance. As a result, the design procedures
presented in the manual are expected to be conservative.
Some of the more rational design procedures are presented in the
manual. It also describes several currently available mathematical
models for evaluating a system's response to a particular constituent or
it's overall performance. A more detailed discussion of specific models
for land treatment is available (10).
One important engineering subject not covered by the Process Design
Manual was that of costs. The first comprehensive reference on this
subject was published by the EPA in 1975 (11). This report provided
cost curves for the major components of land treatment systems. The
information was derived from a combination of:
• Previously published information
• Surveys of then existing facilities
• Consultation with contractors
• Cost calculations based on typical preliminary designs
Although this report was revised in 1979 (12), many of the original
cost curves were left unchanged. Several computer programs for cost
estimation were developed from this original data (13, 14, 15),
Assessment
An assessment of the information base currently available to the
engineering community is given in Table 1. In this table, the
availability, completeness, and practicality of information is
considered for each of the major planning and design factors.
Generally, the information base is considered "adequate" when it:
• Accurately reflects the current research and demonstration data
• Allows the engineer to define acceptable design criteria and to
predict performance with a reasonable degree of confidence
Planning Methodology-
Planning is a critical project phase for land treatment systems.
The site specific nature of land treatment and the multi-disciplinary
approach necessary for planning create special requirements for many
typical wastewater agencies and engineering firms. Recognizing this
need, planning methodology has been well addressed in the Process Design
Manual and other guidelines.
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Table 1. Assessment of Existing Engineering Information for
Wastewater Application Systems
Status on Current Design Information
Factor Slow Rate Rapid Infiltration Overland Flow
Planning Methodology
Preapplication Treatment
Storage Requirements
Loading Rate Determination
Treatment Performance:
BOD & SS
Nitrogen
Phosphorus
Pathogenic Organisms
Trace Organics
Distribution
Management of Renovated Water
Crop Management
Costs
Adequate
Mostly Adequate
Adequate
Adequate
Adequate
Mostly Adequate
Mostly Adequate
Adequate
Limited
Adequate
Adequate
Adequate
Mostly Adequate
Adequate
Adequate
Adequate
Mostly Adequate
Adequate
Limited
Limited
Mostly Adequate
Limited
Adequate
Mostly Adequate
Adequate
Mostly Adequate
Adequate
Adequate
Adequate
Adequate
Mostly Adequate
Limited
Limited
Adequate
Limited
Adequate
Adequate
Adequate
Mostly Adequate
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Engineering and Econorrvcs
Page 57
Preapplication Treatment-
Requirements for unnecessarily high levels of preapplication
treatment have significantly constrained the implementation of cost-
effective land treatment systems in many areas of the country. This
problem continues to some degree in spite of the guidelines currently
available. Current thinking on appropriate levels of preapplication
treatment is summarized in the USEPA 1982 guidance on Facilities
Planning (16) and the Process Design Manual.
For slow rate systems a range of preapplication treatment from
primary to biological treatment with disinfection has been recommended
depending on requirements for:
• Protection of public health as it relates to human consumption
of crops or crop byproducts or to direct exposure to applied
wastewater
• Prevention of nuisance conditions during storage
• Prevention of operating problems in distribution systems
Of these three factors, public health protection is the most difficult
to define. Because of the uncertainties that are often involved and the
emotional nature of this issue, conservative standards generally have
been applied by State or local public health or water quality control
agencies. Continuing system demonstrations will be valuable for further
refinement of these standards.
The degree of public contact is much less with rapid infiltration
and overland flow systems so preapplication treatment guidelines are
related primarily to required system performance and the avoidance of
nuisance conditions. Recommended pretreatment levels range from primary
to biological treatment for rapid infiltration systems. Nitrogen
removal by nitrification-denitrification in the soil can be maximized by
limiting preapplication treatment to primary levels (17). For overland
systems minimal preapplication treatment, such as screening or
comminution, can be acceptable at isolated sites.
Storage Requirements--
There is little design guidance available for determining storage
requirements. This limited guidance Is aimed primarily at slow rate and
overland flow systems. Three computer programs were developed by the
National Climatic Center to estimate storage days when inclement weather
days preclude operation. Generalized information generated from these
program is available (18), or the programs can be run for a specific
location using climatic criteria set by the user.
Loading Rates—
Systematic procedures for estimating design loading rates are
presented in the Design Manual for all three processes.
For slow rate systems, design loading rates may be limited by
either soil permeability or nitrogen concentrations in the
groundwater. Insitu testing is the recommended procedure for
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POUND, GRIFFES AND CRITES
determining soil permeability. Hydraulic loadings are based on a
monthly water balance prepared for the design climatic conditions, using
the estimated soil permeabiTity values. For nitrogen loadings, an
annual water and nutrient balance is constructed which accounts for
nitrogen concentrations in applied and percolating wastewater, crop
uptake, and denitrification and volatilization.
The critical loading rate for rapid infiltration systems is usually
limited to the hydraulic capacity of the soil. BOD, nitrogen, and/or
suspended solids loadings may be critical in some cases. Ranges of
hydraulic loadings are suggested in the Design Manual based on results
from different types of field measurements.
For overland flow systems, guidelines were developed which relate
the hydraulic loading rate to the level of preapplication treatment and
desired treatment performance. Application rates and slope length were
found to be design factors of greatest importance.
Treatment Performance—
BOD and Suspended Solids—All three processes are capable of
providing excellent treatment performance with respect to BOD and
suspended solids. It is only with overland flow systems that some
different required performance levels for removal of these constituents
will affect design criteria. A strong correlation between detention
time of the wastewater on the slope and BOD removals has been well
documented (8, 19). Overland flow systems have experienced problems in
removing algae from stabilization pond effluents.
Nitrogen—Nitrogen removals and transformations are often a
critical design consideration for all land treatment processes.
Consequently considerable research effort has been directed in this area
during the last ten years.
Slow rate system designs are often limited by the allowable nitrate
concentrations in the underlying groundwater. Crop uptake is the
predominate nitrogen removal mechanism with denitrification and
volatilization of ammonia playing lesser roles. Each of these factors
has been addressed in recent design guidelines and sufficient
information is now available to predict nitrogen performance reasonably
well. Nevertheless, refinement and optimization of this information
should continue to be an important objective in the future because of
the direct impact on hydraulic loading rates, land area, and system
cost. Procedures to estimate dilution of nitrates due to mixing and
dispersion in the groundwater also need to be developed.
Nitrification-denitrification is the primary nitrogen removal
mechanism for rapid infiltration. Relationships have been demonstrated
between nitrogen removal and total organic carbon concentration,
infiltration rates, lengths of flooding and drying cycles, soil
temperature and pH. Although these relationships are now at least
partially understood, more effort is needed to develop criteria for
design optimization.
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Engineering and Economics
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Much the same thing can be said for overland flow systems.
Nitrification-denitrification is also the major removal mechanism here,
although crop uptake and ammonia volatilization can also be
significant. General relationships have been demonstrated for several
design and operating parameters, however criteria for design
optimization have not yet been established.
Phosphorus--At the application rates typically encountered with
slow rate systems, phosphorus removal generally is not a matter of
concern. Phosphorus removal can be accounted for in terms of crop
uptake and adsorption and precipitation in the soil. Conservative
design techniques for determining removal capabilities and the useful
life of slow rate systems have been developed (8, 20).
For rapid infiltration systems, phosphorus removal capabilities and
predictions of useful life can be more critical because of the lower
adsorption capabilities of granular soils and the high hydraulic
loadings involved. Long-term precipitation of phosphorus in the soil
column is significant but relatively unpredictable mechanism. An
empirical model has been developed which shows removal is largely a
function of detention time in the soil (21).
Phosphorus removal from overland flow is generally poorer than it
is for the other systems because most of the applied wastewater flows
over the surface and does not contact the soil matrix and adsorption
sites. Enhancement of phosphorus removal has been achieved by aluminum
sulfate addition before application of wastewater. Design information
is limited and optimization criteria are required.
Pathogenic Organisms--Removal of microorganisms, including
bacteria, viruses, parasitic protozoa, and helminths has been a
continuing subject of interest and investigation for all three
processes. Although with each process some significant questions
remain, concern with pathogenic organisms has greatly decreased as
performance of these systems has been demonstrated. For slow rate
systems, the consensus reached in the development of the Design Manual
was that microorganism removal is not normally a limiting factor in the
design procedure (8).
Considerable research has been conducted on wastewater aerosols in
the last 10 years (8). The reported relationship between wastewater
aerosols and incidence of disease in Israel was subjected to further
research and discredited (22). The risk to health from wastewater
aerosols appears to be low and land treatment systems do not present any
more of a health hazard from aerosols than do conventional treatment
plants (8, 23, 24).
Microorganism removal is more critical for rapid infiltration
system design than for the other two systems because of the granular
soils and high hydraulic loading rates typically encountered. Study of
virus removal has been limited to date, although indications are that
effective reductions can be achieved (25). Further demonstration and
study may be required.
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Because most of the renovated wastewater from overland flow is
collected and discharged to surface waters, the concerns are different
than with the other two processes. In general, the removal efficiency
of overland flow systems for pathogenic organisms is comparable to that
of conventional secondary treatment systems. Demonstrations of
microorganism removal have been limited so far, particularly for
viruses. Reduction of enteric viruses by approximately 85* was reported
in a 1976 study (26).
Trace Orqanics — Increasing attention has been given recently to the
ability of land treatment systems to remove trace organic compounds.
Based on results of investigations conducted so far, it appears that all
three processes can provide effective removal of trace organics. A
model has recently been developed for overland flow systems which
relates to trace organic removals to molecular weights, octanol/water
partition coefficient, and Henry's constant for each individual compound
(27). In general, though, the modeling or trace organic performance is
in a very preliminary stage, consequently very little design guidance is
currently available. Such guidance is particularly important for
communities with large industrial wastewater contributions.
Distribution—
There is an ample amount of guidance available on the distribution
techniques for all three processes. To a large extent, this information
was developed by adapting conventional agricultural irrigation
techniques to wastewater application.
One special consideration for wastewater systems has been
distribution design for winter operations. Various techniques have been
demonstrated which allow winter operation of forest (slow rate), rapid
infiltration, and overland flow (to a limited extent) systems.
Management of Renovated Water-
Management of renovated water can take various forms, including
underdrainage of agricultural land, runoff collection for overland flow,
and recovery wells for rapid infiltration. As with distribution
systems, many of these techniques are conventional ones employed by the
agricultural community or for groundwater control. There are special
considerations for wastewater application, of which the following stand
out:
• Stormwater collection and/or release for overland flow systems
• Using the groundwater aquifer for seasonal storage of
irrigation water following rapid infiltration
• Agricultural drainage problems in previously unlrrigated areas
Crop Management--
Although many standard agricultural practices are directly
applicable, there are some special considerations for crop selection and
management of wastewater application systems (primarily slow rate but
also overland flow to a lesser extent). The most significant
requirements commonly encountered are:
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• Maximizing nutrient uptake
• Tolerance of crops to high soil moisture conditions
• The need to schedule applications according to wastewater
availability rather than crop need
Another aspect of crop management is the method of ownership and
control of the agricultural system. There is considerable guidance
available for situations where the wastewater agency controls the entire
operation. However there is less guidance available for planning
alternative arrangements such as contractual relationships with
independent farmers, and leasing arrangements.
Costs--
As mentioned earlier, comprehensive cost information for facilities
planners is currently available (12). The methodology and much of the
actual cost information is still adequate for most planning purposes.
However, the information is somewhat outdated as it was prepared in 1974
and 1975 at a time when there was very little cost data available from
recently constructed systems.
Future Needs
Upon consideration of the practical problems faced by the
engineering community in the planning and design of wastewater systems,
there are certain deficiencies in currently available engineering
guidelines which still must be addressed. These include both research
needs to fill in specific technical gaps and information needs to
synthesize existing knowledge into a practical format. The following is
a summary of major future needs.
Information Needs:
1. Updated cost information based on surveys of recently
constructed facilities and current unit costs.
2. A better definition of grant procedures for alternative forms
of management and control (such as leasing, contract
operations, etc.).
Research Needs:
1. Determination of trace organics removal performance and
mechanisms (particularly for rapid infiltration).
2. Prediction and optimization of nitrogen removals, particularly
for rapid infiltration and overland flow. Prediction of
denitrification is the most important need.
3. Prediction and verification of phosphorus removal by rapid
infiltration.
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POUND GRIFFES AND CRITES
4. Optimization of phosphorus removal by overland flow, especially
using supplemental techniques.
5. Prediction of algae removal by overland flow.
6. Post closure performance of land treatment sites. Long term
fate of pollutants.
7. Refinement of the relationship for rapid infiltration between
long term hydraulic loading rates and initial field tests of
infiltration rates.
8. Prediction of dilution of percolate with groundwater by mixing
and dispersion.
SLUDGE APPLICATION
In the last 10 years the use of sludge on agricultural land has
been an increasingly controversial subject. Less controversial has been
the use of sludge on turf, forest, and drastically disturbed land. The
state of knowledge on land application of sludge has increased
significantly in the past decade. However, many more informational and
research needs remain.
State of Knowledge
For discussion purposes, the technical knowledge associated with
sludge application to land was divided into seven areas:
1. Sludge Properties
2. Planning and Site Selection
3. Application Methods
4. Trace Metal Loadings
5. Nitrogen Decay Rates
6. Stabilization and Disinfection
7. Dedicated Land Application
A significant amount of information has been generated for the
first three areas. This information is considered as adequate for
purposes of design.
In 1978 EPA sponsored a technology transfer publication on Sludge
Treatment and Disposal that included a section on Principles and Design
Criteria for Sewage Sludge Application on Land (28). That document
contains information on planning and site selection, process design,
facilities design, management, monitoring and costs. The emphasis was
on recycling of sludge to land in a useful or beneficial manner. A
discussion of planning and design for disposal of sludge on land was
included in one chapter of the EPA Process Design Manual, Sludge
Treatment and Disposal (29). In this case the emphasis was on
maximizing the placement or application of sludge on lands without
consideration of beneficial use.
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In 1983 EPA plans to publish a Process Design Manual on Utilization
of Municipal Sewage Sludge on Land (30). In addition to the subjects
covered in the 1978 EPA publication the new design manual will have
chapters on application to drastically disturbed lands and dedicated
land application.
In the remaining four areas the state of knowledge for design of
sludge application systems also has advanced. Nevertheless, the
mechanisms and processes involved are only partially understood.
Sludge Properties-
Recognition of the importance of nitrogen and heavy metal
concentrations in design led to increased emphasis on characterizing
sludges for these constituents. Phosphorus, potassium and trace
organics such as PCB's also are important constituents for agricultural
use systems. The presence of toxic organics and the chemistry of
organic transformations in sludges requires further research. Data are
available in publications (28, 30, and 31) on median concentrations of
these constituents in anaerobically and aerobically digested sludge.
Planning and Site Selection-
Site selection criteria have been established for topography, soil
permeability, and depth to groundwater. Site identification procedures
are available to avoid undesirable soils, geology, hydrologic features
and land use.
A usual procedure is to draw concentric circles of increasing
radius around the source of the municipal sludge. A preliminary area
requirement is calculated by dividing the annual sludge production by a
nominal loading rate such as 10 tons/acre/ yr. Starting within the
nearest circle, the unsuitable land is excluded and the procedure
continues moving progressively outward from the inner circle until
sufficient land is located.
Application Methods-
Liquid sludge (1 to 10 percent solids) can be applied by
sprinklers, surface irrigation, trucks, or injection equipment.
Injection equipment can be either truck-mounted tanks with injection
shanks or tractor-pulled devices connected to a sludge pump by an
irrigation hose. Many varieties of injection equipment are available
commercially.
Dewatered sludge and composted sludge can be applied with a
tractor-drawn agricultural manure spreader or similar device mounted on
a truck (32, 33). Sludge cake should be allowed to dry on the soil
surface after spreading and then be incorporated into the soil (34).
Trace Metal Loadings-
Land application of sludge can add significant quantities of trace
metals to the soil. From a phytoxicity standpoint, zinc, copper, and
nickel are the metals of concern. From a human health standpoint,
cadmium is the metal that has received the most attention (35, 36).
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POUND, GRIFFES AND CRITES
The concern for cadmium arises from estimates that dietary intake
of cadmium in the United States is nearly 50 percent of the limit set by
the World Health Organization. The level of cadmium in many crops is
increased following application of cadmium-laden sludges to soils. The
EPA has established annual loading limits for cadmium to avoid excessive
accumulation of cadmium in food-chain crops (37, 38).
Crops vary in their uptake of cadmium. Some cultivars (varieties)
of crops exclude more cadmium than others. Available data suggest that
cadmium uptake can be genetically controlled and that cultivars can be
selected for their low uptake and little translocation to edible parts
According to EPA regulations, the pH of the soil-sludge mixture
must be maintained at or above 6.5 (38). Recent research with sweet
corn showed, however, that kernel cadmium did not increase with a soil
pH of 5.7 to 6.5 (39). The authors suggest that the 0.5 kg/ha limit may
be unnecessarily restrictive for non-accumulator crops such as sweet
corn.
Alternatives to food crops, such as forest, turf, cotton, or
biomass production have been investigated (40, 41). Such alternatives
are attractive because nitrogen loading is the primary constraint hence
much of the current use of sludge is on non-food-chain crops.
Ultimate site capacity often is estimated using a cumulative metal
loading (28, 42). Current research tends to indicate that metal
loadings are not necessarily cumulative in their effects on crops and
that the phytotoxicity levels may be overly conservative (36, 39). The
long term effects of sludge application on crop-metal content should be
researched.
Nitrogen Decay Rates —
Nitrogen in most sludges occurs primarily in the organic form. The
organic nitrogen must "decay" or become biologically transformed into
inorganic forms that are available to plants. The rate of decay may
range from 15% to 35% per year or more. The difference can be
significant in determining the allowable loading rate based on crop
nitrogen use.
The new Design Manual (30) prescribes the following decay rates for
use in design procedures although these values may vary depending upon
site specific conditions:
(36).
Type of Sludge
Raw primary or waste activated
Aerobically digested
Anaerobically digested
Percent available
in the first year
40
30
15
Composted
10
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After the first year the amount of nitrogen decay or mineralization
decreases by approximately 50% each year until it stablizes at about 3*
of the remaining organic nitrogen. For a given sludge, the lower the
decay rate the higher will be the allowable sludge loading rate.
Stabilization and Disinfection—
Considerations of odor control, public health and safety, and ease
of handling have led to considerable developments in sludge
stabilization and disinfection. Composting is a process that can both
stabilize and disinfect sludge (42). The Beltsville aerated-pile method
converts undigested sludge into a composted product that is
aesthetically acceptable and avoids odor production (43).
Irradiation has been proposed as a disinfection alternative or
supplement to anaerobic digestion prior to land application (44).
Pathogen reduction can be achieved with liquid, dried, or composted
sludge (45).
Dedicated Land Application--
Sludge application rates at dedicated sites are significantly
higher than rates for agricultural or forested sites (30)• The concept
is to provide minimal pretreatment of the sludge and apply at the
maximum rate consistent with organic decomposition. In order to oxidize
all available nitrogen (nitrification), it has been estimated that a
limiting nitrogen application rate would be 3.8 Mg/ha/d which translates
to approximately 1.7 dry tons of sludge per acre per day.
Information Needs
Engineering needs that are not normally classified as research
needs are discussed in this section. The major needs are for
comprehensive, up-to-date information on costs, energy, monitoring and
public attitude assessment.
Cost Estimation—
Pretreatment and transportation are generally the largest costs in
land application of sludge. Information is available for most
pretreatment processes (29, 47) and for transportation (28, 30).
However, the costs of land application are less well documented.
Capital and operating costs are available 1n the literature for only a
few individual systems. Subsurface injection costs (48), dedicated land
application costs (30, 46) and operating costs of landspreading (49)
have been reported. What 1s needed is a comprehensive report on costs
of land application including all types of land application techniques
and a wide range of sludge quantities.
Energy Requirements-
Data on energy requirements have been assembled (50) but there
remain deficiencies 1n energy conservation assessment. Energy
requirements of distribution systems such as injection and spreading
have not been presented 1n a comprehensive manner that Includes
currently used equipment and a wide range of sludge types and
quantities.
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POUND, GRiFFES AND CRITES
Monitoring Requirements—
The design engineer needs to know what monitoring procedures and
schedules are realistic for potential environmental effects. A detailed
and extensive monitoring program, proposed in the absence of practical
guidance, can be very expensive and may not be warranted. Guidance in
this area also would be helpful to regulatory agencies. Guidance should
include the need and extent of monitoring of soils, groundwater, sludge
properties, and crop quality (28).
Public Attitude Assessment--
The subject of land application of sludge has been fraught with
controversy about cadmium loadings, risk assessments, and agruments over
safety. Such controversy leads the public and many engineers to assume
the worst and decide that land application is not an appropriate
disposal method. Issues like the Del Monte ban on sludge application
(51) and the controversial statements by Dr. Lisk over safety of land
application need to be put into perspective (52, 53).
Positive programs such as those in Madison, Wisconsin, (51) and at
Columbus, Ohio (52) need to be capsulized and published widely. The
Ohio project, conducted by the Ohio Farm Bureau Development Corporation,
concluded that the more efficient methods for reaching the public are:
1. Small, easily readable information pamphlets.
2. A film on land application which could be used by community,
farm, and interested public groups.
3. A speaker's bureau to provide knowledgeable speakers on land
application to community organizations who frequently seek
topics for their meetings.
Research Needs
Research and development related to land application of sludge is
needed in several areas.
1. Application methods for forestland
2. Long term heavy metal loadings
3. Design criteria for forest application
4. Refinement of nitrogen availability
5. Low cost methods of sludge stabilization and disinfection
Application Methods for Forest land—
Forestland has significant potential for land application, however,
the methods of application are relatively limited, especially for
dewatered sludge. Liquid sludge can be sprayed on the land, either from
moving vehicles or from sprinkler systems. Sprinkler systems using
modified nozzles have proven most effective (56). Dewatered sludge is
difficult to apply to developed forestland and is generally restricted
to initial applications on new plantations. New methods of application
could overcome this restriction.
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Long Term Heavy Metal Loadings—
Sites where land application has occurred over a number of years
have been analyzed (57). Only one site out of 9 produced crops with
metal concentrations in the phytotoxic range and the surface soil at
that site had a pH of 3.7. More controlled research on the phytotoxic
effects of long term heavy metal loadings is necessary. The entire
question of cadmium as a measure of public health problems and use as a
design guideline should be reviewed, including the basic assumptions
implicit in the criteria for daily ingestion by humans, the actual
levels of intake, and the amount potentially attributable to crops grown
on sludge-amended soils.
Design Criteria for Forest Application-
Application rates to agricultural land are limited either by
nitrogen or heavy metal loadings. For forest applications, rates have
not developed sufficiently to allow straight-forward process design.
Denitrification rates, nitrogen storage in acidic soils, and nitrogen
availability rates have not been widely established. Cadmium loading
restrictions do not apply and phytotoxicity limits for zinc, copper, and
nickel have not been established. Loadings of trace elements such as
boron may turn out to be limiting to some tree species.
Refinement of Nitrogen Availability--
There is a need for test methods to determine, for a given sludge
and soil, how fast the organic nitrogen will become available to the
crop and to soil bacteria. Does soil texture, temperature, or pH affect
this rate? Is the current method of relating decay rates to type of
pretreatment adequate? Initial organic nitrogen concentration has been
correlated with nitrogen availability in recent research (55).
Stabilization--
Low cost stabilisation methods are needed specifically for forest,
drastically disturbed land, and dedicated land application. Lime
stabilization, for example, may be desirable for stabilization of raw
sludge prior to application to drastically disturbed land. Pretreatment
methods need to be optimized to provide the necessary stabilization and
disinfection for the specific application at the least cost.
Disinfection is not necessary prior to dedicated land application and
may not be required prior to forest or disturbed land application.
CONCLUDING STATEMENT
The last 10 years have brought a dramatic increase in energy costs
which affected our comparison of alternative technologies for treatment
and disposal of both wastewater and sludges. Assuming energy costs will
rise relative to other costs during the next decade, we will see efforts
continuing toward development of low energy consuming or even net energy
producing technologies. Such technologies may be particularly
applicable for sludge management in large population centers.
Nevertheless, the use of land application of wastewater and sludges,
especially for beneficial reuse of water and nutrients, will continue to
offer cost competitive options and play a predominant role in solving
our waste management problems.
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POUND, GRIFFES AND CRITES
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Control Federation. Volume 19, No. 2, p. 6. February, 1982.
54. Cunningham, J. and M. Northouse. Land Application of Liquid
Digested Sewage Sludge (Metrogro) at Madison. Proceedings of the
Third Annual Madison Conference of Applied Research and Practice on
Municipal & Industrial Waste, Madison, Wisconsin. September 10-
12, 1980.
55. Parker, C. F. and L. E. Sommers, Mineralization of Nitrogen in
Sewaqe Sludqes. Journal of Environmental Quality. Volume 12. No.
1, pp. 150-156. T5SI
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Engineering and Economics
Page 73
QUESTIONS AND COMMENTS FROM THE FLOOR:
Betty H. Olson, University of California, Irvine: How much aon-
eidevation is being given to making land application of wastewater or
sludge application economically feasible at local, state, and federal
levels?
Charles Pound: I am not in the best position to answer your
question since Metcalf & Eddy is not involved directly in the review of
proposed projects. However, since 1977 the EPA has offered economic
incentives for land treatment of wastewater and land application of
sludge as Innovative and Alternative technologies. On the local and
state levels land application must compete as a low cost technology with
other waste treatment technologies. Most of these agencies are primarily
concerned with protecting the environment and the public health rather
than promoting the economics of any given process. Therefore, a conser-
vative approach is usually taken, sometimes leading to the detriment of
the economic issues of land application.
Merilyn B. Reeves, League of Women Voters: What is the state of
knowledge in regard to level of treatment prior to land treatment? The
discussion paper referred to the fact that nitrogen removal can be done
with primary treatment, or in the case of overland flow, lees than pri-
mary. For phosphorus removal or pathogens is secondary treatment
necessary? For areas like the Chesapeake Bay the issue of nutrient remo-
val, and its cost, is of prime importance. Is land treatment considered
advanced treatment, and is it made too expensive by requiring secondary
treatment first?
Charles Pound: To answer your first question first, I believe that
we have a reasonably well developed state of knowledge with regard to
pretreatment prior to most land application systems. Experience has
shown us that acceptable performance in rapid infiltration, overland
flow, and surface Irrigation systems, can be achieved with primary
effluents. However, from a practical standpoint, additional treatment Is
often necessary to minimize the possibilities of odor production and
nuisance conditions. Secondary treatment and disinfection 1s often bene-
ficial for pathogen removal prior to Irrigation particular for systems
where there may be some degree of public contact.
On your second question: Please note that conventional secondary
treatment will not provide significant amounts of phosphorus removal.
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Page 74
POUND, GRIFFES AND CRITES
Dr. Merry L. Morris, New Jersey Department of Environmental
Protection: What do you include in the category of "monitoring"? The
range of monitoring activities or requirements is quite extensive. What
do you consider could be case specific and which could be regional or
national requirements?
Charles Pound: It is very difficult to develop general monitoring
requirements for all land application systems since the requirements will
vary considerably from site to site and will depend upon the process
employed, the application rates, and other factors. In general, though,
the monitoring program for most land application systems should include
at least some monitoring of groundwater at the perimeter of the site.
Water quality samples should be taken periodically, perhaps as frequently
as monthly during the initial period of operation. Later, the frequency
can often be reduced to quarterly or less. Typical parameters of concern
for most land application systems are nitrogen, TDS, chloride, and
possibly total organic carbon (TOC). Case-specific monitoring require-
ments may include constituents krtown to be contributed from local
industrial sources.
Merry Morris: What do you consider to be the advantages of forest
application of wastewater effluents or sludges?
Charles Pound: There are several advantages which can sometimes be
realized by the application of wastewater or sludge to forest lands.
First, forest lands are often less expensive than other land which may be
available. Also, steeper, less desirable areas can be utilized as com-
pared to open land. Quite often the water can be applied year round,
Including during winter conditions. Finally, forest application systems
can often enable one to minimize site disturbance and to Isolate the
systems from public view and public access.
Charles F. Jelinek, Food and Drug Administration: In general,
sludge should not be applied by spraying to food or feed (including
forage and fodder) crops. Studies have shown that dried sludge adheres
to plants with great tenacity, even through heavy rains. Animals eating
such crops can ingest organics and pathogens directly. Many organics
bioaccumulate in fatty tissues, and can thus be present in muscle or milk
in comparatively high levels. Likewise, organics, toxic metals and path-
ogens present on food eaten by humans, such as vegetables and fruits, can
be consumed directly by the individual.
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Engineering and Economics
Page 75
Robert B. Dean, Lun-Dean Environmental Company, Copenhagen, Denmark:
Further to the question of establishing monitoring requirements - engi-
neers would like a complete set of monitoring specifications before they
start. However, this is not the most-effective monitoring system. A
good quality control program should be used to establish monitoring
requirements based on performance. Monitoring of only a few parameters
can give essentially all of the useful information at a greatly reduced
cost. The problem is that we do not know in advance which will be the
critical parameters for a new site. They can only be found out by
experience•
Terry J. Logan, Ohio State University: We do not have adequate
knowledge of sludge properties, especially sludge metal chemistry and
content of organics.
Charles Pound: For planning purposes there is sufficient infor-
mation in the literature on sludge properties. For design purposes each
sludge to be land applied should be characterized for constituents of
concern. Municipal sludges should be analyzed for nitrogen, phosphorus,
metals, and potentially toxic organics. Characterization for all toxic
organics is very expensive and is seldom done 1n practice. Generally,
the extent of organics content determination is limited to PCB's and
pesticides.
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HYDROLOGIC MANAGEMENT: NUTRIENTS
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Page 79
HYDROLOGIC AND NUTRIENT MANAGEMENT ASPECTS OF MUNICIPAL
WASTEWATER AND SLUDGE UTILIZATION ON LANfc^
D. R. Linden, C. E. Clapp, and R. H, Dowdy^
USDA-ARS and Department of Soil Science
University of Minnesota
St. Paul, MN
INTRODUCTION
The bi'osystem of soil, organic crop residues, and growing crops
can effectively renovate municipal wastewater effluents and sewage
sludges. Soils and crops have proven to be effective treatment systems
in research and in practice. Treatment systems have been designed to
handle a wide variety of materials from clear effluents to sludges
under various crop, soil, and climatic conditions. The success of
these treatment systems is often highly dependent upon decisions during
operations. Adequately designed systems can prove ineffective when
management decisions fail to make adjustments for changing conditions.
A critical management need for the successful operation of most waste
renovation systems is the control of the hydrology and hydraulics for
water movement at and near the soil surface. Successful renovation of
wastes and protection of the environment are often linked to this
critically important, biologically-active, and man-controllable zone of
the treatment system.
The purpose of this paper is to discuss the hydrologic and
nutrient management needs of operational land treatment systems and to
give specific examples of management adjustments that have been used to
control and improve the renovation of wastes. The term land treatment
system covers a wide range of system types, including slow rate, rapid
infiltration and overland flow effluent systems, as well as dry and
liquid sludge applications for utilization or disposal. Some
management considerations are unique to a particular waste renovation
- Contribution of the Soil and Water Management Research Unit, North
Central Region, USDA-ARS, St. Paul, MN 55108, in cooperation with the
Minnesota Agric. Exp. Stn., Misc. J. Ser. Paper No. 1851.
—^ Research Soil Scientist, Research Chemist, and Research Soil
Scientist, respectively, USDA-ARS, St. Paul; and Assistant Professor,
Professors, respectively, Dept. of Soil Science, Univ. of
lesota, St. Paul, MN.
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LINDEN. CLAPP AND DOWDY
system, whereas others can be manifested in general terms to apply to
many systems. For example, the necessity to avoid water-logged soils
for crop production applies primarily to effluent irrigation systems,
but concern for crop uptake of nitrogen (N) applies to almost all waste
renovation systems. For this reason some background information on the
similarities and differences in systems will be presented before
discussing several key problems requiring management consideration.
DESIGN AND OPERATION OF A LAND TREATMENT SYSTEM
There are three important aspects to the design and operation of a
waste renovation land treatment system. The first aspect is the type
of material to be utilized. There are obviously different requirements
for handling sludges than effluents. Type of delivery system, method
of application, need for incorporation, and rate of application are
largely functions of the type of material. Only small quantities of
sludge need to be applied to land in comparison with dilute effluents,
for comparable fertilizer value.
The second aspect of the design and operation of a land treatment
system involves the soil, geology and climate of the area. Different
management is required when faced with shallow or deep soils, slow or
high permeability, steep-sloped or level surfaces, humid or arid
climate, cold or warm conditions, and crop or forest lands. Effluent
should be applied differently to a moderately permeable soil in a cold,
semi-humid climate than to a highly permeable soil in a warm, arid
cl imate.
The third aspect for the design and operation of a land treatment
system is the economic constraints for the design combined with the
philosophy of the designer. Systems have been designed'and operated
for a final treatment process whereby maximum application rates are
desired. Systems have also been designed and operated as direct
resource recycling systems wherein either nutrients or water for crop
production have dictated lower application rates. The Beltsville
sludge trenching system (Sikora et al., 1982) and the Minnesota
agricultural watershed (Duncomb et al., 1982) are examples of different
systems.
Soils and crops can renovate wastes because they act as a physical
filter for the removal of solids, a chemical reaction medium for
immobilization of dissolved constituents, and a biological reaction
medium for the conversion of constituents by living organisms. The
filtering activity is caused by water flow through small openings
(pores) which trap large particles. Chemical reactions include
precipitate formation, sorption and others. Biological reactions
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Hydroiogic Management: Nvilrvems
Page 81
include for example, nitrification, denitrification and crop uptake.
These processes are the core of a soil-crop renovation system. The
predominant renovation mechanisms depend upon the material to be
renovated, the soils, and climate, and the philosophy of the system.
These are the processes that can be influenced by the management of the
system. It is also the observation of these processes and their
effects on renovation that will dictate the need for management
decisions.
Land application of wastewater effluents can be categorized into
three systems: slow rate or crop irrigation systems, rapid
infiltration or groundwater recharge systems and overland flow systems.
Crop irrigation systems such as Penn State (Sopper and Kardos, 1973a),
Apple Valley, MN (CIapp et al., 1977b), Muskegon, MI (Ellis et al.,
1982) and Michigan State (Tesar et al., 1982) usually involve ordinary
agricultural or silvicultural techniques while utilizing effluent as a
nutrient or water resource. The final renovation of N from the water
primarily involves management of the crop. Other constituents of
effluent may also be affected by the crop, but the soil usually acts as
the primary physical filter and chemical reaction medium. Management
of this type of system primarily needs to provide a favorable
environment for crop production (Linden et al., 1978).
Groundwater recharge systems such as Flushing Meadows (Bouwer et
al., 1974) involve ordinary hydroiogic and hydraulic considerations for
maximizing the chemical and physical filtering capacity of the soil.
Considerable attention must also be given to the micro-movement for
biological renovation within the soil mass. The primary management
needs of this type of system are to maintain both a high hydraulic
capacity and a favorable environment for biological denitrification.
Overland flow systems such as those at WES (Lee and Peters, 1979)
and CRREL (Palazzo et al., 1982} utilize only a small portion of the
soil profile, while effluents run over the soil surface through a
standing crop. Management considerations involve both the crop (NO^-N
uptake) and the micro-environment near the soil surface for biological
deni tri fication.
Land treatment systems for sewage sludges are designed for either
disposal or utilization. There 1s a wide variety of sludge types,
including liquid (less than 5% solids), slurries, filter-cake and
dried, and composted materials, which can be applied to land 1n one of
the two systems. A land disposal system such as the Beltsville sludge
entrenchment study (Sikora et al., 1982) Involves the placement of a
maximum amount of material 1n a minimum amount of space. The primary
management consideration Is to minimize the migration of materials away
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LINDEN, CLAPP AND DOWDY
from the disposal site. Sludge utilization land treatment systems such
as the Rosemount, MN watershed (Clapp et al., 1977a; Duncomb et al.,
1982) and the Fulton County, IL, project (Peterson et al., 1980)
involve using the nutrients and organic matter in sludges as a resource
for crop production and soil improvement. The primary management
considerations of these systems are to incorporate and keep the
material in the root zone until it is utilized for crop production.
With this wide diversity in types of effluent and sludge systems
in mind, the remainder of this paper will deal with some very specific
management considerations and problems for meeting the renovation
requirements of a system. Some of these key problems are unique to a
specific system, whereas others may be involved in more than one type
of system. Specific examples from cases reported in the literature and
from our own experiences of more than 12 years of work on land
treatment systems will be used.
SPECIFIC PROBLEMS AND MANAGEMENT CONSIDERATIONS
Soil Sealing and Hydraulic Degradation
The effect of the applied material and the method of application
on the ability of the soil to conduct water and air is important in
slow rate and rapid infiltration effluent treatment systems, as well as
liquid sludge treatment systems. Soil pores can be blocked by
suspended solids, gas bubbles from chemical and biological reactions,
microbial biomass (bacteria, fungi, and algae), and soil solids from
compaction, erosion, or reorientation during wetting (especially from
rain or sprinkler-drop action), thereby restricting water and air
movement. Such restrictions can cause problems in maintaining the
designed hydraulic loading rates in rapid infiltration effluent
systems, poor soil aeration for crop production, reduced applications
of effluent in crop utilization systems, and increased risk of runoff.
Fortunately, these problems can be minimized by proper management. Two
examples will illustrate how proper management minimized soil sealing.
At the Flushing Meadows rapid infiltration effluent project in
Phoenix, AZ. (Bouwer et al., 1974; Rice, 1974), special management
techniques were developed in order to minimize the causes and effects
of soil sealing. Effluent was allowed to flow overland through a
grassed area, to remove suspended solids in the effluent, before
ponding in infiltration basins. Thus a major cause of sealing was
removed before final land treatment. Even with pretreatment, the soil
infiltration capacity decreased with time in the basins, necessitating
further management adjustments. Periodic drying cycles, occasional
physical disturbances of soil (removal of deposits), and grass cover
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Hydrologic Management: Nutrients
Page 83
crops were necessary in order to restore and maintain high infiltration
rates. Drying cycles caused the surface layer to dry and crack, thus
reopening the surface. Grass cover promoted root channelization,
keeping the soil open and porous.
At the crop irrigation effluent study at Apple Valley, MN (Clapp
et al., 1977b; Marten et al., 1979; Marten et al., 1981), low
infiltration rates under conventionally-managed corn (Zea mays L.)
culture restricted water and nutrient supplies for optimum crop
production. Grass or small grain cover-crops prevented sealing and
allowed larger and more frequent irrigation with effluent. We found
that corn could be grown in rye or perennial grass covers. In both
systems strips were tilled in order to partially suppress the growth of
the grass and to prepare a good seed bed for the corn. With annual rye
no other competition suppression was needed because the rye was
maturing as the corn began rapid growth. Some additional herbicidal
suppression was required with perennial grass as the cover crop. The
grass biomass protected the soil surface from rain and irrigation drop
action and promoted the formation of biomass-related porosity of the
soil surface layer. The combined cropping system allowed good corn
production while maintaining a high infiltration capacity of the soil.
The combination grass and corn crop system was a management adjustment
made after operations began in order to prevent soil sealing. Such
adjustments may be necessary for other land waste treatment systems in
order to optimize the performance of the system.
Crop Management
Crops are an integral part of most land treatment systems and
require special management. Important management criteria for the
successful operation of a land treatment system Includes: (1) selection
of the best adapted crop, (2) pretreatment of soil with lime and
fertilizers, (3) attention to soil drainage and aeration requirements,
(4) use of higher seeding rates than normal, (5) allowance of
sufficient time for stand establishment, (6) selective or complete
reduction of competition from weeds or grasses, and (7) timely
harvesting. Some attention has been given to each of these aspects of
crop management 1n waste renovation research and a complete review will
not be given here. Crop management needs can be summarized, however,
as follows: the manager should attempt to provide the best possible
physical, chemical, and biological environment for the best adapted
crops that have some economic value. In some cases this may require
more management skill than simply controlling the application of the
waste material. Several examples from our experiences with wastewater
irrigation will help Illustrate the need for these special management
skills.
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LINDEN, CLAPP AND DOWDY
During the fall and early spring, following an August seeding of
perennial forage species, only light and infrequent irrigations of
wastewater were applied (Marten et al., 1979). This practice allowed
time for seed germination and seedling establishment in order to insure
a good stand of each species. The established stand thus had the best
opportunity to withstand heavy and frequent wastewater irrigations
begun later in the spring and continued for several years. Differences
in persistance of the various species which occurred later was not
related to ability of the plants to become established under wet soil
conditions. The same practice was followed each year with the annual
corn crop (Marten et al., 1980).
Forage harvesting schedules had to be adjusted to take advantage
of the regrowth and N uptake characteristics, while not reducing the
regrowth potential of the plant (Marten et al., 1979). Such management
adjustments require considerable knowledge of the growth
characteristics of forage species, and depended on the amount of
wastewater applied in our studies (Linden et al., 1981).
Runoff
All land used for agricultural crop production should be managed
in such a way as to minimize soil erosion and water runoff. This maxim
is particularly true for landscapes receiving wastewater sludges and
effluents because relatively greater loss of plant nutrients will
reduce the productive potential of a given site, and the risk of
pollution of surface waters will be magnified. Obviously, overland
flow systems designed for wastewater treatment are special cases where
controlled runoff is desirable.
Most sewage sludge constituents that possess a potential for
surface water contamination are only sparingly soluble, with the
exception of N. In this context, conservation practices and structures
that minimize sediment runoff will also greatly reduce the hazard of
surface water contamination. Using terracing and conservation tillage
practices, we were able to hold sediment losses to a minimum within a
watershed that contained slopes of up to 12%. On the areas cropped to
continuous corn, sediment losses occurred only during high intensity
storms in the spring and early summer prior to canopy closure (Ouncomb
et al., 1982).
Sediment yields never exceeded 1.0 Mg/ha per storm on areas
receiving 8 to 15 Mg/ha of sewage sludge annually by injection. Copper
(Cu), chromium (Cr), and zinc (Zn) concentrations (Table 1) did
increase slightly in the sediments removed from sludge-treated areas,
but the concentrations of cadmium (Cd), Cr, Cu, nickel (Ni), lead (Pb),
and Zn (Table 2) were not increased in the runoff waters.
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Hydrologic Management; Nutrients
Page 85
Table 1. Elemental content of selected stormwater sediments from corn
areas after 5 years of sewage sludge applications at the
Rosemount watershed in 1978.
Date
Treatment
Sediment
Yield
Element
N
P
Zn
Cu
Cd
Ni
Pb
Ci
kg/ha
mg/g
—ug/g—
6/30
Control
830
10.0
626
52
27
0.8
18
27
4!
Sludge
552
7.7
862
73
46
0.8
18
35
9;
7/10
Control
170
0.4
_
40
14
0.5
44
u
SIudge
44
0.3
775
76
45
0.8
18
34
9(
The losses of metals from grass sod areas were confined
essentially to snowmelt runoff (Dowdy et al., 1980), since sodded areas
yielded very little sediment. Trace metal concentrations in snowmelt
waters were low, in the parts per billion range. Surface applications
of sewage sludge during the growing season to grass areas did not cause
increased Cd, Ni, or Pb concentrations in snowmelt runoff. Copper
concentrations were consistently higher in snowmelt from sludge-treated
areas than from control areas. However, winter applications of sludge
on frozen, snow-covered grass areas, that had previously been
sludge-treated, did result in increased Cr, Cu, Ni, Pb, and Zn
concentrations in snowmelt runoff. Copper concentrations, which
exhibited the largest change, were increased from 10 to 100 yg/L. The
significance of this increase must be considered in light of USPHS
drinking water standards of 1000 pg Cu/L.
The fact that Cu was the first and most consistent metal to appear
in snowmelt runoff from grassed areas was not unexpected from a
chemical point-of-view. All sludge applications were applied on the
grass sod and accumulated as a mat on the soil surface. As snow
melted, water filtered through the sludge mat, leaching
organically-complexed metal ions out of the residual sludge and into
runoff waters. Copper complexes are the most stable and soluble of the
trace metals we measured and may be the fulvic acid types studied by
Sposito et al. (1979).
Metal contamination of surface and groundwaters as a result of
land applications of wastewater effluents is unlikely, particularly
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LINDEN, CLAPP AND DOWDY
Table 2. Elemental content of selected storm runoff water under corn
and grass crops after 5 years of sewage sludge applications at
the Rosemount watershed in 1978.
Element
Date
Treatment
Runoff
N
P
Zn
Cu
Cd
Ni
Pb
Cr
cm
—mg/L —
ug/L—
Corn
4/7
Control
2.1
24.0
0.15
19
10
<2
4
<12
3
SIudge
3.9
47.8
0.87
27
18
<2
9
<12
5
6/28
Control
0.8
3.7
0.14
28
4
1
4
22
12
SIudge
0.6
3.1
0.82
21
14
<1
3
<15
< 2
6/30
Control
4.4
1.4
0.15
13
5
<1
6
<15
3
SIudge
1.6
0.9
0.97
17
8
<1
4
<15
< 2
7/10
Control
0.4
0.5
0.23
16
5
<1
5
<20
< 3
SIudge
0.4
0.6
0.51
12
7
<1
7
<20
< 3
9/14
Control
2.5
1.7
0.20
72
7
<1
2
<27
<10
Sludge
1.8
2.1
0.61
19
12
<1
<11
<27
<10
Grass
4/7
Control
2.2
59.2
0.99
46
20
<2
12
<12
3
Sludge
2.8
24.9
5.22
57
74
<2
9
<12
25
Sludget
3.1
49.6
7.78
52
92
<2
' 14
<12
26
6/26
Control
0.7
6.4
0.99
22
9
<2
4
<15
< 1
SIudge
0.4
18.0
6.39
139
24
<2
8
<15
3
SIudget
0.5
47.3
7.64
30
29
<2
12
<15
4
7/10
Control
0.1
2.4
2.82
122
14
<1
7
<21
7
SIudge
0.8
18.5
9.54
39
37
<1
19
<21
27
Sludget
0.7
7.2
8.03
34
63
<1
12
<21
16
9/14
Control
2.9
2.5
1.09
14
6
<1
< 3
<25
< 9
Sludge
3.1
11.8
5.80
42
41
<1
9
<25
< 9
Sludget
2.7
13.1
6.41
15
45
<1
< 3
<25
< 9
t Received winter application of 4.0 Mg/ha sewage sludge 1n January
1978.
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Hydrologic Management: Nutrients
Page 87
when renovation systems are managed 1n such a way as to maintain a
vegetative soil cover. In addition to management techniques that limit
environmental degradation due to land application of sewage sludge,
municipal effluents have very low trace metal concentrations (Dowdy et
al., 1978).
Nitrogen
Nitrogen is the element of major concern in land application of
municipal wastewater effluents and sewage sludges. Average
concentrations of 20 to 40 mg N/L for effluents and 3 to 5% N (30 to 50
g N/kg) for sludges are typical. When these amounts of N are applied
to land at accepted agricultural rates and undergo biochemical and
microbial transformations in the soil, questions immediately arise as
to possible environmental pollution of surface and groundwaters. Much
of the research on municipal waste utilization conducted during the
past ten years has dealt with these potential problems of N management.
Application rates of N for most waste utilization experiments have
covered the range from low (deficiency) to very high (excess) amounts,
depending on the crops and soils under investigation. Our studies at
Apple Valley with wastewater effluent applied to corn and forage
grasses used annual N applications ranging from 190 to 830 kg N/ha/yr
(Dowdy et al., 1982). Sewage sludge experiments have provided even
greater N rates, including 620 to 1380 kg N/ha/yr for corn and reed
canarygrass on a terraced watershed (Ouncomb et al., 1982), 250 to 1460
kg N/ha/yr for turfgrasses (Clapp et al., 1982), and 1600 to 6300 kg
N/ha/yr on small corn plots (Stark and Clapp, 1980).
Emphasis in waste utilization studies 1s placed on N because its
transformations 1n the soil-piant-water system encompass the whole N
cycle. Forms of N in effluents are especially important, having ratios
of NH.-N:N07-N:organic N ranging from 11:1:2 (Clapp et al., 1978) to
6:7:1 (Deese et al., 1977). A high NH.-N to NOj-N ratio appears to be
desirable from both soil storage and water quality aspects. The NH.-N
form of N accumulates 1n the cation-exchange complex of soils, delaying
its conversion to the NO^-N form which can be leached into groundwater.
The Penn State project (sopper and Kardos, 1973b) experienced yield
reductions of corn and high NO-j-N leaching when effluent-N changed to
higher N03-N contents.
A few attempts have been made to account for N in the
soi1-water-crop system by measuring characteristic N components in a
field experiment (Sopper and Kardos, 1973b; Clapp et al., 1977b; Oeese
et al., 1977). Excessive N may have adverse effects such as reducing
yield and quality of fruit crops, delaying maturity of cotton, lowering
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LINDEN, CLAPP AND DOWDY
sugar content of sugar beets and starch content of potatoes, and
causing lodging of grain crops (Bouwer and Chaney, 1974). However,
feed quality of forage grasses and corn fodder was not reduced when
these crops were grown on land irrigated with effluent supplying large
amounts of N (Sopper and Kardos, 1973b; Marten et al., 1978).
For rapid infiltration wastewater effluent treatment systems, N
transformations in the soil below the infiltration basins were governed
by flooding and drying sequences (Bouwer et al., 1980). If short,
frequent flooding periods (~2 da) were used, the soil remained
sufficiently aerobic for essentially complete conversion of the N in
the effluent to NO^-N in the renovated water. With longer flooding
periods (~2 wk), CL in the soil was depleted during flooding, as NH^-N
in the effluent was adsorbed by the cation-exchange complex of the soil
and then nitrified during drying. Resulting NO^-N was partially
denitrified and the rest leached out during the next flooding period.
With nitrification-denitrification as the main mechanism for N
removal in rapid infiltration systems, the flooding and drying sequence
that maximizes denitrification and N removal percentage depends on
various factors which must be evaluated for each particular system.
Pertinent factors include the NH^-M and C contents o£ the effluent,
infiltration rates, CEC of the soil, exchangeable NH^ percentage, depth
of CL penetration in soil during drying, and temperature. The combined
laboratory and field data from the Flushing Meadows experiments (Bouwer
et al., 1980) showed that to achieve high N removal percentages, the
amount of NK^-N applied during flooding must be balanced against the
amount of 0,, entering the soil during drying. Flooding periods must be
long enough to develop anaerobic conditions in the soil. Infiltration
rates must be controlled to the appropriate level for the particular
effluent, soil, and climate at a given site.
In a 30-year study of a rapid infiltration site at Hollister, CA
(Levine et al., 1978) effective N removal was provided by 7 m of soil.
Input total N levels of 40 mg/L were reduced to less than 4 mg/L within
a shallow aquifer. No pollution hazard was posed by NO^-N. A
comparison of total N input to that gained by the soil revealed that
only 2% of the wastewater N could be accounted for in the upper 300 cm
of the soi1 profile.
For overland flow wastewater treatment systems, a number of
mechanisms are involved in N removal, including volatilization,
biological nitrification-denitrification, adsorption, soil storage, and
plant uptake (Martel et al., 1982). The NH.-N form can be removed by
any of the above mechanisms. Most of the organic N is initially
removed by sedimentation, then incorporated into the soil or converted
to NHj. The major losses other than crop uptake measured at Utica, MS
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Hyarologic Managemert: Nutrients
Page 89
(Peters et al., 1981) were volatilization of NH^ (about 9% of applied
effluent N) and nitrification-denitrification (j4 to 42%).
Specific design and operating criteria to optimize N removal or
NHj conversion in overland flow systems have not been established,
however, the following general relationships can be stated: (1) total N
and NH., removed is inversely related to application rate and directly
relatea to slope length, (2) rate of nitrification is reduced if
wastewater is applied continuously, and (3) the overall N removal and
NH-j conversion efficiency is reduced as soil temperature drops below 13
to 14°C, due to decreased biological activity.
In contrast to wastewater effluents, most N in sewage sludges
occurs in the organic form, with NH^-N comprising about 10 and 30% of
the total N for aerobically- and anaeroblcally-digested sludges,
respectively. The rate of organic-N mineralization, therefore, becomes
a top priority research objective in terms of determining N
availability. Organic-N mineralization for freshly applied sludges has
been studied by several investigators in the laboratory. Premi and
Cornfield (1971) found from 2.3 to 4.2% of the added organic N had
mineralized after six weeks of incubation. Epstein et al . (1978)
reported that 41% of a digested sludge's organic N had mineralized
after 15 weeks of incubation. Magdoff and Chromec (1977) found that 14
to 25% of the organic-N from an applied anaerobically-digested sludge
mineralized during a 13-week period, whereas 36 to 61% of the organic-N
mineralized from an applied aeroblcally-digested sludge. Ryan et al.
(1973) showed that 4 to 48% of the organic-N in an
anaerobically-digested sludge had mineralized after 16 weeks of
incubation. Pratt et al. (1973) found that 35, 10, 6, and 5% of the
residual organ1c-N 1s mineralized for the first, second, third, and
fourth year, respectively, following application of sludge to
agricultural land in California, whereas sludge application guidelines
from Wisconsin cite a decay series of 15 to 20, 6, 4, and 2% (Keeney et
al., 1975).
Our studies on residual-N availability from soils treated with
sewage sludge in a field experiment indicated that application rate was
more important than sludge type (Stark and Clapp, 1980). Those
experiments proved that the chemical indexes of N availability were as
reliable as more time-consuming incubation procedures for determining
the N-supplylng capacity of soils and sludges. Later studies on N
availability from field soils five years after incorporation of sewage
sludge have shown the importance of residual m1neral-N in assessing
long-term N supplying power of heavy sludge applications (Harding et
al., 1981).
Concern about groundwater contamination by N0.J-N from application
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LINDEN, CLAPP AND DOWDY
of excessive amounts of effluents and sewage sludges has led to
extensive monitoring of experimental sites with shallow wells and
porous ceramic cup water samplers. Our Apple Valley wastewater
effluent experiment showed that NO^-N levels in soil water at 125-cm
depths increased significantly witn increased effluent application
rates, especially under corn, but only occasionally exceeded 10 mg/L
during early and late season (Fig. 1), when applications surpassed crop
uptake demands (Larson et al., 1980). The Rosemount sewage sludge
watershed study (Duncomb et al., 198?) illustrated N overloading
problems where N0,-N contents of soil water at 150-cm depths increased
to 200 and 60 mg/L for corn and reed canarygrass areas, respectively,
when annual N applications approached 800 kg N/ha, The data from this
study suggest the ratio of total N application to crop removal should
not exceed approximately 2.0 to prevent NO^-N buildup at depths below
the rooting zone of crops.
When municipal effluents and sewage sludges are applied to
agricultural land, the primary objective becomes their use as a source
of plant nutrients for crop production. Similarly, the most effective
method of removing an element, e.g., N, is to harvest the plants that
have taken up the element, and remove them from the area. Crop yields
serve as an indicator of effectiveness of a waste utilization system
and are influenced by many additional factors other than those directly
related to the waste material, including climate, soil physical and
chemical properties, drainage, crop species, crop and soil management,
and application rates and schedules. The quantity of an element
removed by a waste utilization system is determined by total dry matter
produced (crop yield) and the content of that element in the harvested
part of the crop.
Total N uptake for corn under the effluent irrigation system at
Apple Valley (Clapp et al,, 1978) ranged from 110 to 170 kg N/ha/yr for
applications of 200 to 650 kg N/ha/yr (55 to 26% uptake). Other
researchers in Pennsylvania (Sopper and Kardos, 1973b; Hook and Kardos,
1977) and in Florida (Overman and Nguy, 1975) obtained average values
of 100 kg N/ha/yr uptake from 200 kg N/ha/yr applied (50%) and 180 kg
N/ha/yr uptake from 580 kg N/ha/yr applied (31%), respectively.
Corresponding uptake values for reed canarygrass in Minnesota (Clapp et
al., 1978) ranged from 235 to 420 kg N/ha/yr for applications of 235 to
800 kg N/ha/yr (100 to 523 uptake). Reed canarygrass in Pennsylvania
(Hook and Kardos, 1977) gave values of about 390 kg N/ha/yr uptake from
630 kg N/ha/yr applied (62%), and in Alberta (Bole and Bell, 1978) gave
59 to 237 kg N/ha/yr uptake from 52 to 410 kg N/ha/yr applied (113 to
58%), respectively. Similar N uptake values were obtained for reed
canarygrass and orchardgrass in New Hampshire (Palazzo and McKim 1978;
Palazzo, 1981). The 4-year average uptake of N by corn and reed
canarygrass following sewage sludge application (Duncomb et al., 1982)
was 225 kg N/ha/yr (26%) and 355 kg N/ha/yr (34%), respectively. Our
results indicate that high yielding and good quality crops of corn and
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Hydrologrc Management: Nutrients
Page 91
20
15-
10-
CORN
1976
? s-
z
0
1
i—r
UJ
u
8 20-
z
Ul
£E
t 15-
z
1—I 1—I—I—I
A M J J A S O
1977
10-
5-
o-^t—r
A M J J A S O
20 n
15
10
FORAGE
1976
20-i
15-
10-
1977
I j | | | | |
A M J J A S O
MONTH
Figure 1. Monthly mean nitrogen concentrations at 125-cm depth under
the high effluent treatment of corn and forage crops for
1976 and 1977 at the Apple Valley wastewater effluent
project.
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LINDEN, CLAPP AND DOWDY
forage grasses can be produced under very high levels of N applied in
wastewater effluent or sewage sludge, providing best management
practices are followed to decrease adverse environmental effects.
Uptake of N by crops during treatment of wastewater effluent by
overland flow systems depends on plant species as well as other factors
influencing biological interactions. Water-tolerant forage grasses
generally have high N uptake capacities. At the Utica, MS site (Peters
et al., 1981), a grass mixture of reed canarygrass, tall fescue,
perennial ryegrass, and common Bermudagrass removed between 179 and 222
kg N/ha/yr. At Hanover, NH, annual plant uptake by a mixture of tall
fescue, orchardgrass, reed canarygrass, and perennial ryegrass ranged
from 210 to 332 kg N/ha/yr (Palazzo et al., 1982). Proper management
of the crop is extremely important in overland flow systems, especially
with regard to stand establishment, weed control, nutrient status, and
cold tolerance.
Phosphorus
Phosphorus is another component of wastewater sludges and
effluents that theoretically could degrade surface and groundwaters.
Like trace metals, P compounds are only sparingly soluble, and the
greatest threat for degradation of the environment would be associated
with P as a component of sediment eroded from the landscape. However,
significant increases in the P concentrations of runoff waters from
sludge-treated areas on our watershed have been observed (Table 3).
Phosphorus concentrations and total P losses were considerably higher
from the sludge-treated grass areas than from comparable corn areas.
Incorporating sludge into the soil on the corn areas lowered P losses.
Dunigan and Dick (1977) also reported that incorporation of sludge
reduced P losses by 5 to 18 times. Maximum P loss occurred from the
grass area that received winter applications of sewage sludge.
Ketcheson (1978) and Shelton and Lessman (1978) also found greater
soluble P losses during winter months after sludge was applied during
the same winter period. The same general trends of increased P in
storm runoff from sludge-treated areas appear to hold for runoff events
occurring during the growing season.
Although in a soluble form, P loadings by wastewater effluent
irrigations on croplands are much less than P additions via sewage
sludge applications. Phosphorus additions were 2 to 4 times less than
those made in our sludge utilization studies, even with an annual mean
addition of 2.4 m of effluent. Our 6-year field study of wastewater
renovation indicated that soils receiving comparable quantities of P as
effluent or mineral fertilizer (rates for good crop management) behave
in a similar manner with no apparent leaching of P to a 60-cm depth
-------
Table 3. Phosphorus applied versus phosphorus in snowmelt runoff from
terraced corn and grass areas at the Rosemount watershed.
CornGrass
Runoff Runoff
Year
Treatment
Applied
Concen-
tration
Quantity
Applied
Concen-
tration
Quantity
kg/ha
mg/L
kg/ha
kg/ha
mg/L
kg/ha
1976
Control
65
0.1
0.0
58
0.3
0.1
Sludge
614
0.3
0.1
267
1 .5
0.3
1977
Control
16
0.2
0.0
20
0.7
0.3
Sludge
332
0.8
0.5
371
2.6
1.4
1978
Control
17
0.4
0.1
17
0.8
0.2
Sludge
301
1.1
0.4
533
4.3
1.2
Sludget
—
—
648
10.4
3.1
1979
Control
17
0.2
0.1
17
0.6
0.9
Sludge
579
1.0
0.4
405
2.5
1.2
Sludget
—
...
—
521
6.7
8.6
t Received winter applications of 4.0 and 5.3 Mg/ha sewage sludge in
January 1978 and 1979, respectively.
(Latterell et al., 1982). For crops receiving twice this P loading, P
leaching to the 60-cm depth was observed.
Phosphorus ranks second only to N in nutritional Importance to
crops. Some soils require additions of P fertilizer to sustain plant
growth. Effluents and sludges, when applied in sufficient amounts to
satisfy N needs for plants, will often provide P in excess of crop
uptake, although P uptake by crops is neither as htgh nor covers as
wide a range as N uptake. Corn and reed canarygrass removed about 35
and 55 kg P/ha/yr, respectively, with wastewater effluent application
rates of 65 and 160 kg P/ha/yr at Penn State (Sopper and Kardos, 1973b)
and 190 and 250 kg P/ha/yr at Apple Valley (Clapp, et al., 1978).
Sewage sludges applied over a 4-year period on corn and reed
canarygrass at the Rosemount watershed removed an average of 38 and 42
kg P/ha/yr, respectively, for applications of 460 kg P/ha/yr (Duncomb
et al., 1982). The long-term effects of P application are usually
associated with determining when the soil sorption capacity will be
exceeded and thus shorten the life of a land treatment site.
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LINDEN, CLAPP AND DOWDY
Phosphorus removal from wastewater effluents by rapid
infiltration and overland flow renovation systems is often less
efficient than was observed in our slow infiltration studies. Since P
removal in these systems is a result of sorption on soil-colloids
and/or precipitation on the soil matrix, renovation efficiency is a
direct function of effluent application rate and retention time within
the treatment zone. Bouwer et al, (1980) reported a P removal of about
40% when secondary effluent was applied at maximum hydraulic loadings
at the Flushing Meadows project. By reducing hydraulic loadings (i.e.,
increase retention time), these researchers were able to increase P
removal to about 80%.
Literature summarized by the USEPA (1981) suggests that overland
flow systems generally remove 40 to 60% of the P from wastewaters.
Jenkins et al . (1978) observed an 80 to 90% P removal when effluent was
applied to their overland flow system at approximately 0.05 m/wk during
the summer months, but P removal decreased to about 30% during winter
applications in New Hampshire. In Mississippi, increased retention
times and/or reduced effluent application rates significantly increased
P removal from applied wastewater (Peters and Lee, 1978; Lee and
Peters, 1979). Similar trends have been reported by Thomas et al.
(1974) and Abernathy (1983). However, additions of aluminum sulfate to
the effluent prior to land application greatly improved P reductions in
overland flow systems (Thomas et al., 1976; Peters and lee, 1978).
Other Macro Nutrients
The macro nutrients K, Ca, and Mg, and the element Na, usually
vary in concentration in effluents and sludges with respect to water
source and wastewater treatment processes. Levels of K in most waste
materials are not high compared to crop K requirements. Wastewater
effluents can have a range in K concentrations of 10 to 15 mg/L, and
with annual applications of 2.5 m should provide 250 to 375 kg K/ha/yr.
High producing forages removing up to 350 kg K/ha/yr will require
additional fertilizer K to maintain soil K levels and avoid deficiency
(Marten et al., 1979). Sewage sludges are commonly low in K (<1%) and
crops must be supplemented with K fertilizer for optimum growth when
insufficient K is available from the soil. Plant K uptake may also be
adversely influenced by high-lime (Ca) sludges or by soils containing
free CaCO^. Waste utilization experiments have not been designed to
study K interactions and uptake because it is not a serious threat for
water contamination. Usually fertilizer K is added in ample amounts,
so as not to limit plant growth.
Most effluents and sludges contain sufficient amounts of Ca and
Mg, and these nutrients normally do not adversely affect crop response.
Effluent Ca and Mg levels can range from 10 to 20 and 5 to 25 mg/L,
respectively. Sludge Ca and Mg values range from 3 to 5% and 0.5 to
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Hydrologic Management: Nutrients
Page 95
1.0%, respectively, except for high-lime materials, which can contain
15% Ca. Corn and reed canarygrass may remove up to 25 and 50 kg
Ca/ha/yr and 25 and 40 kg Mg/ha/yr, respectively (CIapp et al., 1978;
Duncomb et al., 1982).
There has been concern that high concentrations of Na and
associated salt anions in effluents could lead to degradation of soil
structure and permeability and that Na could compete with K for
exchange sites in the soil and for plant uptake. We observed that an
equilibrium was established between effluent, soil, and soil water
after four years to give an exchangeable Na percentage of 6.0% in the
Apple Valley study, even though Na concentrations of 275 mg/L and an
application rate up to 8,000 kg Na/ha/yr were used (Larson et al.,
1979). We know of no problems associated with Na for either effluent
or sludge experiments. The higher salt concentrations of sewage
sludges (2.5 to 6.0 dS/m) may limit plant growth (Larson, et al., 1981;
CI app et al., 1982). This effect is not relatively wide-spread, but
will bear observation in the course of waste utilization studies.
The potential for groundwater contamination by sludge-borne trace
metals is extremely limited (Dowdy and Volk, 1983). Although some
studies have noted movement of metals to layers below the zone of
incorporation, it appears that Zn is the element that most consistently
has potentia^o move in soils. The mechanisms by which it moves,
whether as Zn , as an anionic form, or as a chelated compound, have
not yet been established. Trace metal movement will most likely occur
with large applications to a sandy, acid, low organic matter soil that
receives high rainfall or irrigation. Even under these conditions the
extent of movement will be limited, but metals may move through open
soil channels or cracks where the soil has no opportunity to attenuate
them.
PERSPECTIVES ON FUTURE RESEARCH
Short term research on the management of land treatment systems
for the renovation of municipal sewage wastes has resulted in the
development of systems that are successfully operated throughout the
world. Many short term and site specific management problems have been
encountered and solved. Infiltration rates, N leaching, crop response,
and runoff, among other potential problems, can be controlled through
proper management. Proper management, however, requires some very
specific management skills and continuous, perceptive observation of
the system. It is the necessity for transferring such skills from
successful operation of land treatment systems to new designs that
dictate future research in this area. Research information must be
broad enough to be applicable to new sites and conditions in order to
allow design of improved systems.
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LINDEN, CLAPP AND DOWDY
Needs for research over the long term are more numerous. Site
aging with respect to trace metals and P are examples of these longer
term needs. The fate of applied materials such as N and trace metals
after cessation or during long periods of application also require
longer term research. Will soils continue to immobilize P and metals
in forms that prevent water contamination or plant uptake? While we
may have a reasonable understanding of how much of various materials
will move within the soil mass over the short term, an understanding of
the chemistry controlling such phenomena is very limited. This
information is essential to development of sound management criteria
applicable to a wide range of soil and climatic conditions. Simulation
models (Gupta et al., 1978; Iskandar, 1981) could provide many of the
answers required for solving the long term research problems of land
treatment systems.
LITERATURE CITED
Abernathy, A. R. 1983. Overland flow treatment of municipal sewage at
Easley, SC. EPA-600/S2-83-015. R. S. Kerr Environmental Research
Laboratory, Ada, OK.
Bole, J. R., and R. G. Bell, 1978. Land application of municipal
sewage waste water: yield and chemical composition of forage
crops. J. Environ. Qual. 7:222-226.
Bouwer, H., and R. L. Chaney. 1974. Land treatment of wastewater.
Adv. Agron. 26:133-176.
Bouwer, H., R. C. Rice, and E. D. Escarcega. 1974. High rate land
treatment 1: Infiltration and hydraulic aspects of the Flushing
Meadows project. J. Water Poll. Control Fed. 46:834-843.
Bouwer, H., R. C. Rice, J. C. Lance, and R. G. Gilbert. 1980.
Rapid-infiltration research at Flushing Meadows project, Arizona.
J. Water Poll. Control Fed. 52:2457-2470.
Clapp, C. E., D. R. Duncomb, W. E. Larson, D. R. Linden, R. H. Dowdy,
and R. E. Larson. 1977a. Crop yields and water quality after
application of sewage sludge to an agricultural watershed, p.
185-198. Jji R. C. Loehr (ed.) Food, fertilizer, and agricultural
residues. Ann Arbor Science Publishers, Ann Arbor, MI.
Clapp, C. E., D. R. Linden, W. E. Larson, G. C. Marten, and J. R.
Nylund. 1977b. Nitrogen removal from municipal wastewater
effluent by a crop Irrigation system, p. 139-150. In R, C. Loehr
(ed.) Land as a waste management alternative. Ann ATEor Science
Publishers, Ann Arbor, MI.
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Hydrologic Management: Nutrients
Page 97
Clapp, C. E., A. J. Palazzo, W. E. Larson, G. C. Marten, and D. R.
Linden. 1978. Uptake of nutrients by plants irrigated with
municipal wastewater effluent. Proc. State of Knowledge in Land
Treatment of Wastewater, Int. Symp., Hanover, NH, August 20-25,
1:395-404.
Clapp, C. E., D. B, White, R. C. Polta, and N. J. Durben. 1982. Yield
and composition of turfgrasses during six years of fertilization
with sewage sludge. Agron. Abstr. 1982:27.
Deese, P. L., R. F. Vaccaro, B. H. Ketchum, P. C. Bowker, and M. R.
Dennett. 1977. Ionic distribution in a spray Irrigation system,
p. 39-66. In R. C. Loehr (ed.) Food, fertilizer, and agricultural
residues. TtrTn Arbor Science Publishers, Ann Arbor, MI.
Dowdy, R. H., C. E. Clapp, G. C. Marten, D. R. Linden, and W. E.
Larson. 1982. Wastewater crop management studies in Minnesota.
Chap. 3. p. 35-47, Jh^F. M. D' Itri (ed.) Land treatment of
municipal wastewater, vegetation selection and management. Ann
Arbor Science Publishers, Ann Arbor, MI.
Dowdy, R. H., C. E. Clapp, D. R. Duncomb, and W. E. Larson. 1980.
Water quality of snowmelt runoff from sloping land receiving
annual sewage applications, p. 11-15, Proc. Nat'l Conf.
Municipal Indust. Sludge Utilization Disposal, Alexandria, VA, May
28-30.
Dowdy, R. H., G. C. Marten, C. E. Clapp, and W. E. Larson, 1978.
Heavy metals content and mineral nutrition of corn and perennial
grasses irrigated with municipal wastewater. Proc. State of
Knowledge 1n Land Treatment of Wastewater, Int. Symp,, Hanover,
NH, August 20-25. 2:175-181.
Dowdy, R. H., and V, V, Volk. 1983, Movement of heavy metals 1n
soils. D. W. Nelson, K. K. Tanjl and D. E. El'rich (ed.)
Chemical mobility and reactivity 1n soil systems.. Soil Scl. Soc.
Am., Madison, WI. (In press).
Duncomb, D. R., W. E. Larson, C. E. Clapp, R. H. Dowdy, D. R. Linden,
and W. K. Johnson. 1982. Effect of liquid wastewater sludge
application on crop yield and water quality. J, Water Poll.
Control Fed. 54:1185-1193.
Dunlgan, E. P., and R. P. D1ck. 1977. The quality of surface runoff
water from fertilized and sewage sludge-treated soils, p.
151-152, Rep. Proj. La. Agric. Expt. Station, Dept. Agronoirjy,
Baton Rouge, LA.
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LINDEN, CLAPP AND DOWDY
Ellis, B. G., A. E. Erickson, L. W. Jacobs, and B. D. Knezek. 1982.
Crop management studies at the Muskegon County Michigan land
treatment system. Chap 4. p. 49-64. F. M. D'ltri {ed.) Land
treatment of municipal wastewater, vegetation selection and
management. Ann Arbor Science Publishers, Ann Arbor, MI.
Epstein, E., D. B. Keane, J. J. Meisinger, and J. 0. Legg. 1978.
Mineralization of nitrogen from sewage sludge and sludge compost.
J. Environ. Qual. 7:217-221.
Gupta, S. C., M. J. Shaffer, and W. E. Larson. 1978. Review of
physical/chemical/biological models for prediction of percolate
water quality. Proc. State of Knowledge in Land Treatment of
Wastewater, Int. Symp., Hanover, NH, August 20-25. 1:121-132.
Harding, S. A., C. E. Clapp, and W. E. Larson. 1981. Residual
nitrogen availability from soils five years after sewage sludge
incorporation. Agron. Abstr. 1981:26.
Hook, J. E., and L. T. Kardos. 1977, Nitrate relationships in the
Penn State "Living filter" system, p. 181-197. In R. C. Loehr
(ed.) Land as a waste management alternative. AnnTrbor Science
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Iskandar, I. K. (ed). 1981. Modeling wastewater renovation, land
treatment. John Wiley & Sons, Inc., New York, NY.
Jenkins, T. F., C. J. Martel, D. A. Gaskin, D. J. Fisk, and H, L,
McKim. 1978. Performance of overland flow land treatment in cold
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Keeney, D. R., K. W. Lee, and L. M. Walsh. 1975. Guidelines for the
application of wastewater sludge to agricultural land in
Wisconsin. Tech. Bull. 88. Wisconsin DNR, Madison, WI.
Ketcheson, J. W. 1978. Effect of slope and application time in sludge
runoff losses. Agron. Abstr. 1978:28.
Larson, W. E., C. E. Clapp, R. H. Dowdy, D. R. Linden, and G. C.
Marten. 1979, 1980, 1981. Utilization of sewage wastes on land.
Unpublished reports, USDA-ARS, St. Paul, MN.
Latterell, J. J., R. H. Dowdy, C. E, Clapp, W. E. Larson, and D. R.
Linden. 1982. Distribution of phosphorus in soils irrigated with
municipal wastewater effluent: A five-year study. J. Environ.
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Lee, C. R., and R. E. Peters. 1979, Overland flow treatment of a
municipal lagoon effluent for reduction of nitrogen, phosphorus,
heavy metals, and coliforms. Progress in Water Technology 11:
175-184.
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Hydrologic Management: Nutrients
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Levine, P. E., J. V. Olson, and R. W. Crites. 1978. Nitrogen and
phosphorus removal after 30 years of rapid infiltration. Proc.
State of Knowledge in Land Treatment of Wastewater, Int. Symp.,
Hanover, NH, August 20-25. 2:17-25.
Linden, D. R., C. E. Clapp, and J. R. Gilley. 1981. Effects of
municipal wastewater effluent irrigation scheduling on nitrogen
renovation, reed canarygrass production, and soil water
conditions. J. Environ. Qua!. 10:507-510.
Linden, D. R., W. E. Larson, R. E. Larson, and C. E. Clapp. 1978.
Agricultural practices associated with land treatment of domestic
wastewater. Proc. State of Knowledge in Land Treatment of
Wastewater, Int. Symp., Hanover, NH, August 20-25. 1:313-322.
Magdoff, F. R., and F. W, Chromec. 1977. Nitrogen mineralization from
sewage sludge. J. Environ. Sci. Health A12(4 & 5):191-201.
Martel, C. J., T. F. Jenkins, C. J. Diener, and P. L. Butler. 1982.
Development of a rational design procedure for overland flow
systems. CRREL Report 82-2, Hanover, NH.
Marten, G. C., C. E. Clapp, and W. E. Larson. 1979. Effects of
municipal wastewater effluent and cutting management on
persistence and yield of eight perennial forages. Agron. J. 71:
650-658.
Marten, G. C., R. H. Dowdy, W. E. Larson, and C. E. Clapp. 1978. Feed
quality of forages irrigated with municipal sewage effluent.
Proc. State of Knowledge in Land Treatment of Wastewater, Int.
Symp., Hanover, NH, August 20-25. 2:183-190.
Marten, G. C., W. E. Larson, and C. E. Clapp. 1980. Effects of
municipal wastewater effluent on performance and feed quality of
maize vs. reed canarygrass. J. Environ. Qual. 9:137-141.
Marten, G. C., D. R. Linden, W. E. Larson, and C. E. Clapp. 1981.
Maize culture in reed canarygrass sod to renovate municipal
wastewater effluent. Agron. J. 73:293-297.
Overman, A. R., and A. Nguy. 1975. Growth response and nutrient
uptake by forage crops under effluent irrigation. Commun. Soil
Science and Plant Analysis 6:81-93.
Palazzo, A. J. 1981. Seasonal growth and accumulation of nitrogen,
phosphorus, and potassium by orchardgrass irrigated with municipal
wastewater. J. Environ. Qual. 10:64-68.
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Page 100
LINDEN, CLAPP AND DOWDY
Palazzo, A. J., T. F. Jenkins, and C. J. Martel. 1982. Vegetation
selection and management for overland flow systems. Chap. 8. p.
135-154. Jji F. M. D'Itri (ed.) Land treatment of municipal
wastewater, vegetation selection and management. Ann Arbor
Scientific Publishers, Ann Arbor, MI.
Palazzo, A. J., and H. L. McKim. 1978. The growth and nutrient uptake
of forage grasses when receiving various application rates of
wastewater. Proc. State of Knowledge in Land Treatment of
Wastewater, Int. Symp., Hanover, NH, August 20-25. 2:157-163.
Peters, R. E., and C. R. Lee. 1978. Field investigations of advanced
treatment of municipal wastewater by overland flow. Proc. State
of Knowledge in Land Treatment of Wastewater, Int. Symp., Hanover,
NH, August 20-25. 2:45-50.
Peters, R. C., C. R. Lee, and D. J. Bates. 1981. Field investigations
of overland flow treatment of municipal lagoon effluent. WES
Tech. Report EL-81-9, Vicksburg, MS.
Peterson, J. R., C. Lue-Hing, J. Geschwind, R. I. Pietz, and D. R.
Zenz. 1980. Metropolitan Chicago-Fulton County sludge
utilization program, p. 322-338. _[n W. E. Sopper, E. M. Seaker,
and R. K. Bastian (ed.) Land reclamation and biomass production
with municipal wastewater and sludge. The Pennsylvania State
University Press, University Park, PA.
Pratt, P. E., F. E. Broadbent, and J. P. Martin. 1973, Using organic
wastes as nitrogen fertilizers. Calif. Agric. 27(6):10-13.
Premi, P. R., and A, H. Cornfield. 1971. Incubation study of nitrogen
mineralization in soil treated with dried sewage sludge. Environ.
Pollut. 2:1-5.
Rice, R. C. 1974. Soil clogging during infiltration of secondary
effluent. 0. Water Poll. Control Fed. 46:708-716.
Ryan, J. A., D. R. Keeney, and L. M. Walsh. 1973. Nitrogen
transformations and availability of an anaerobical ly-di (jested
sewage sludge in soil. J. Environ. Qual. 2:489-492.
Shelton, C. H., and G. M. Lessman, 1978. Quality characteristics of
agricultural and waste disposal runoff water. J. Soil Water
Conserv. 33:134-139.
Slkora, L. J., W. D. Burge, and J. E. Jones. 1982. Monitoring of a
municipal sludge entrenchment site. J. Environ. Qual. 11:321-326.
Sopper, W. E., and L. T. Kardos (ed.). 1973a. Recycling treated
municipal wastewater and sludge through forest and cropland. The
Pennsylviania State University Press, University Park, PA.
-------
Hydrologic Management, Nutrients
Page 101
Sopper, W. E., and L. T. Kardos. 1973b. Vegetation responses to
irrigation with treated municipal wastewater, p. 271-294. In W.
E. Sopper and L. T. Kardos (ed.) Recycling treated municipal
wastewater and sludge through forest and cropland. The
Pennsylvania State University Press, University Park, PA.
Sposito, G., K. M. Holtzclaw, and C. S. LeVesque-Madore. 1979. Cupric
ion complexation by fulvic acid extracted from sewage sludge-soil
mixtures. Soil Sci. Soc. Am. J. 43:1148-1155.
Stark, S. A,, and C. E. Clapp. 1980. Residual nitrogen availability
from soils treated with sewage sludge in a field experiment. J.
Environ. Qua!. 9:505-512.
Tesar, M. B., B. D. Knezek, and J. E. Hook. 1982. Management studies
of annual grasses and perennial legumes and grasses at the
Michigan State University water quality management facility.
Chap. 6. p. 79-105. Iri_F. M. D'ltri (ed.) Land treatment of
municipal wastewater, vegetation selection and management. Ann
Arbor Scientific Publishers, Ann Arbor, MI.
Thomas, R. E., B. Bledsoe, and K. Jackson. 1976. Overland flow
treatment of raw wastewater with enhanced phosphorus removal.
EPA-600/2-76-131. R. S. Kerr Environmental Research Laboratory,
Ada, OK.
Thomas, R. E,, K. Jackson, and L. Penrod. 1974. Feasibility of
overland flow for treatment of raw domestic wastewater.
EPA-660/2-74-087. R. S. Kerr Environmental Research Laboratory,
Ada, OK.
USEPA, USACOE, USOI, and USDA. 1981. Process design manual for land
treatment of municipal wastewater. EPA 625/1-81-013.
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Page 102
LINDEN, CLAPP AND DOWDY
QUESTIONS AND COMMENTS FROM THE FLOOR:
Donna J. Griffin, Minteoh, Inc., Tulsa, OK: Dr. Linden shoved a
slide reflecting more runoff from sludge plots than control. I
questioned it as I would anticipate greater infiltration of sludge-
amended soils.
Dennis R. Linden: In theory and practice sludge applications to
land have two conflicting effects on infiltration. First of all, the
organic materials in sludge do promote soil structure and to the stabi-
lity of soil structural units during wetting which should be an enhan-
cement to infiltration. The second effect 1s that of sealing or clogging
of soil pores because of the deposition of f1ne-gra1ned materials. This
effect is a detriment to infiltration, but 1s of minor significance if
sludge applications are incorporated into the soil.
Little experimental evidence exists to show major Impacts of sludge
applications on the Infiltration characteristics of soil.
Kenneth Dotson, EPA, Municipal Environmental Research Laboratory,
Cincinnati, OH: Were concentrations of nitrogen in soil-water under
sludge application plots NO -N or N?
Dennis R. Linden: Concentrations were of NO -N, reported as mg of
NO -N per L in water. 3
3
Stephen Campbell, BIOGRO Systems, Anapolis, MD: 1. Does soil com-
paction from application equipment affect the percolation of water
through soil, and to what extent is it a management factor?
Dennis R. Linden: Yes, Soil compaction from traffic will reduce
percolation of water and is a major management factor. The moisture con-
dition and "traff1cabH1ty" (ability to withstand loads without serious
compaction) are factors that need to be considered. Scheduled drying-out
periods must be allowed In order to permit farming (planting, cultiva-
tion, harvest, etc.) practices without damage to the soil.
In general a soil with good Internal drainage will have suitable
traff1cab1l1ty after about two days of drainage and drying.
Stephen Campbell: 2. Was sludge actually applied on top of snow for
your runoff studies?
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Hydrologic Management Nutrients
Page 103
Dennis R. Linden: This 1s not a generally recommended practice, but
in this carefully monitored experimental situation, there were no adverse
effects to the environmental quality from the "on snow" application of
sludge. "On snow" applications of animal wastes (manures) have been
shown to reduce soil erosion because of the soil surface stabilizing
Influence.
-------
HYDROLOGIC MANAGEMENT: TRACE METALS
-------
Page 107
FATE OF TRACE METALS DURING LAND TREATMENT
OF MUNICIPAL WASTEWATER
A. C. Chang and A. L. Page
Department of Soil and Environmental Sciences
University of California
Riverside, CA 92521
Application of municipal wastewater to land has been practiced since
the advent of wastewater treatment (Iskandar, 1978; Jewell and Seabrook,
1979). Through this practice, wastewater receiving various degrees of
pretreatment has been introduced into the soil system with waste disposal
being the primary objective. The public health and hydraulic aspects of
spreading wastewater have been extensively investigated. However, only
within the past two decades has attention been given to their effects on
water quality. Although soils have been shown to be an effective medium
in attenuating suspended solids, biodegradable organic matter and patho-
gens, land treatment systems have not performed in a consistent manner
under diverse conditions. During the 1973 workshop on Recycling Munici-
pal Sludges and Effluents on Land the need to better characterize soils'
performance as a wastewater treatment medium was keenly recognized. It
was also recognized that phytotoxic levels of trace metals accumulate in
soils and that accumulation of hazardous trace metals in harvested plant
tissue may restrict land treatment of wastewater.
Conceptually, land treatment differs from conventional municipal
wastewater treatment in two aspects. In a conventional wastewater treat-
ment system, each unit process is designed to deal with one category of
pollutants in water. As the wastewater is being purified in a treatment
plant, it passes through a treatment train consisting of several selected
unit processes arranged in a logical sequence. For land treatment, a
system is expected to remove the multitude of pollutants from applied
wastewater in one step. Unlike a conventional wastewater treatment sys-
tem which consists of a treatment mode and a discharge mode, the treat-
ment and the discharge are frequently combined Into a single operation 1n
land treatment (except overland flow systems). Because effluents from
land treatment may directly enter surface or groundwater, it 1s Important
that final quality of the discharge can be controlled and predicted 1f
operational conditions change.
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Page 108
CHANG AND PAGE
Existing land treatment systems are usually designed and operated
to optimize the removal of suspended solids and BOD. Although trace
metals are not expected to be a limiting factor in land treatment, it is
essential that potential detrimental effects of trace metals are not
overlooked. This report reviews and summarizes results from case studies
concerning the fate of trace metals during land treatment of wastewater
effluents.
TRACE METALS IN WASTEWATER
"Site specific" is an inherent feature of all land treatment sys-
tems. It 1s essential that the composition of wastewater to be treated
is carefully matched with the characteristics of the site and planned
system. Successful application of land treatment methods depend on sev-
eral interrelated factors such as soil type, topography, groundwater
characteristics, climate, etc. Since cllmatological, hydrological, and
pedologlcal features of a land treatment site can not be easily altered,
pretreatment of wastewater or selective management techniques are often
necessary to make up for deficiencies of the site. In this manner, con-
taminants not compatible with the prescribed land treatment scheme may be
removed prior to water application or by Imposing special management of
the system.
Pretreatment requirements for land treatment vary for overland flow,
rapid infiltration and slow rate systems. Although overland flow systems
designed for treating municipal wastewater are comparatively new, they
will accept a wastewater with minimum pretreatment and produce an efflu-
ent similar in quality to secondary effluents from conventional waste-
water treatment systems (Hall et al., 1979), High rate systems charac-
terized by rapid 1nfiltration/percoTat1on through porous soil medium, are
frequently used for effluent polishing. Unless the Influent to a high
rate land treatment system 1s properly pretreated, the hydraulic loading
and the treatment performance will be difficult to maintain. Many
operating high rate application systems 1n the U.S. renovate secondary
effluents (Bouwer et aK 1974; Leach et al., 1980). The function of slow
rate systems may range from simply provicfTng water for crop Irrigation to
substituting for advanced treatment. The degree of pretreatment required
for slow rate systems must, therefore, be adjusted accordingly.
Trace metals are minor constltutents 1n municipal wastewater. Trace
metal contents of municipal wastewater are, however, almost always higher
than its source water due to industrial waste contribution and Input from
domestic sources such as human wastes and consumer products used daily
(Hathaway 1980). For a typical municipal wastewater 1n the U.S., non-
Industrial sources' share of total trace metal load usually are <25% of
the total metal loading (Klein et aj_., 1974; Davis and Jacknow, 1975;
Levins et al., 1979).
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Hydrologic Management Trace Metals Page 109
Once trace metals enter the wastewater stream they tend to be
adsorbed by wastewater solids or form Inorganic precipitates (Blakeslee,
1973; Chen et al., 1974), During treatment, trace metal concentrations
of wastewater wTll be reduced as suspended solids and biodegradable orga-
nic matter are separated from the water. Since wastewater treatment
systems are not designed and operated to optimize the removal of trace
metals, consistent removal of metals 1s not always achieved. Table 1
summarizes concentrations of selected trace metals In municipal waste-
water and treated effluents. Even after secondary treatment, significant
amounts of trace metals present in effluent are present as finely divided
suspended particles {Chen et al., 1974).
Table 1. Concentrations of trace metals in municipal wastewater and their
treated effluents.
Raw Wastewater1" Primary Effluent7 Secondary Effluent2
Element Range Median Range Median ftange " Med11 an
---------- - - - - - mg -L~1 -------------
As
<0.0003-1.90
0.085
<0.005-0.03
<0.005
<0.005-0.023
<0.005
B
<0.123-20.0
-
<0.01-2.4
1.0
<0.1-2.5
0.7
Cd
<0.0012-2.14
0.024
<0.02-6.4
<0.02
<0.005-0.15
0.005
Cr
<0.0008-83.3
0.40
<0.05-6.8
<0.05
<0.005-1.2
0.02
Cu
<0.0001-36.5
0.42
<0.02-5.9
0.10
<0.006-1.3
0.04
Hg
<0.0001-3.00
0.11
<0.0001-0.125
0.0009
<0.0002-0.001
0.0005
Mo
<0.0011-0.874
-
<0.001-0.02
0.007
0.001-0,0018
0.007
N1
0.002-111.4
0.23
<0.1-1.5
<0.10
0,003-0.6
0.004
Pb
0.001-11.6
0.12
<0.02-6.0
<0.2
O.003-0.35
0.008
Se
<0.002-10.0
0.041
<0.005-0.02
<0.005
<0.005-0.02
<0.005
Zn
<0.0001-28.7
0.52
<0.02-2.0
0.12
0.004-1.2
0.04
^Derived from data In Ml near et al., 1981.
2Chang and Page, 1983.
ATTENUATION OF TRACE METALS IN SOILS
In terms of land application of wastewater, the soil may be viewed
as a dynamic filter. It 1s a chemically and m1crob1olog1cally active
porous medium consisting of weathered minerals, organic residues, micro-
organisms, water and air. Passage of wastewater through the soil matrix
will induce a variety of reactions which are the basis for soils to reno-
vate wastewater.
Mechanisms responsible for removing constituents from wastewater
during land treatment depend on the physical characteristics of the im-
purities present. Straining and filtration are the the primary
-------
Page 110
CHANG AND PAGE
mechanisms for removal of suspended solids present in applied water. If
wastewater particles are larger than soil pores, particulates are
strained off at the soil-water interphase. High hydrualic loading and/or
high suspended solid concentrations may result in rapid accumulation of a
layer of finely divided particles at the soil surface and thereby re-
strict the infiltration of water. From an operational point of view,
straining to remove undesirable constituents during land treatment fre-
quently is undesirable when organic particles accumulate much faster than
they are biologically decomposed. For those suspended solids that are
not retained at the soil surface, retention by filtration at lower soil
depths is quite effective. As suspended particles travel with water
through the porous medium, they are trapped and brought into contact with
the surface of the soil solid phases by various physical and hydrodynamic
forces which control behavior of particles suspended in fluids (Ives,
1973). Suspended solids coming in contact with soil particles may then
be immobilized by surface adsorption. The effectiveness of filtration is
a function of suspended solid concentrations, the soil's mechanical char-
acteristics and the hydraulic loadings (Yao et al., 1971), Generally,
lower concentration, finer soil texture, slower flow velocity and longer
travel distance enhance suspended solids removal during filtration.
Since significant amounts of trace metals are present in wastewater and
their treated effleunt as finely divided suspended solids, there is
reason to believe that filtration is probably the most effective mecha-
nisms to attenuate trace metals during land treatment. In overland flow,
the majority of the applied water flows across the relatively impervious
slope in a thin sheet. Suspended solids are removed as water travels
through the vegetative mat. With the removal of suspended solids, the
concentrations of trace metals in the water applied should also be
reduced.
Trace metals also are present in wastewater in dissolved forms. The
physical reaction of straining and filtering would have little effect on
the removal of dissolved constituents during land treatment. If dis-
solved impurities are to be effectively retained by soil, chemical and
microbial reactions are required to immobilize them. Chemical reactions
that determine the forms and fate of trace metals in soil receiving
wastewater have been extensively reviewed (Lindsay , 1973; Chang and
Page, 1983). Trace metals present in the soil solution may enter the
stationary phase by exchanging with ions already on exchange sites or ad-
sorbing onto specific surfaces of amorphous soil constituents. If the
solution concentration of a trace metal element exceeds the solubility
product of solid phase compounds precipitation will take place. The
trace metal containing soil minerals may also dissolve when the trace
metal element in question becomes under-saturated in the solution phase.
Constituents dissolved in soil solution are also subject to chelation by
soluble organic matter, removal by plant, microbial uptake and leaching
by water movement. Under certain circumstances, a few elements such as
As, Se, Hg, etc., may volatilize. Recent advances in understanding soil
chemical equilibria have contributed significantly to our understanding
-------
Hydrologic Management: Trace Metals
Page 111
of the Interactions of various inorganic chemical constituents with the
soil matrix (Page et al_. ,1981). However, the rate and degree of ion ex-
change, specific absorption, precipitation, dissolution and organic che-
lation reactions depend on kinetic and thermodynamic factors 1n soils.
The shifting in soil pH and the redox potential are especially important
in defining the chemical reactions between trace metals and soils (Sims
and Patrick, 1978). Attempts have also been made to model the trace
metal equilibria in the soil solution based on thermodynamic association
constants and solubility products of various chemical reactions 1n soils
(Mattigod and Sposito, 1979). Ideally, the outcome of chemical equili-
brium should be coupled with the hydraulic aspects of the land treatment
to project trace metal solute movement In soils. Numerous studies on
chemistry of trace metals introduced Into soils through wastewater appli-
cation tend to Indicate strong Immobilization of trace metals 1n soils
(Lindsay, 1972). Since chemical equilibria occur in all soil systems,
although substantial attenuation occurs, complete removal of trace metals
during land treatment of wastewater is not likely to take place.
FATE OF TRACE METALS DURING LAND TREATMENT
In the soil environment, chemical reactions described 1n the pre-
vious section occur simultaneously. Because of the interacting nature of
these chemical pathways in soils, it is difficult to distinguish the
contribution of each chemical reaction in soils experimentally. To com-
plicate the problem even further, trace metal additions to soils during
land treatment usually are quite small. As a result, impacts of trace
metals to the waste-receiving soils and on the quality of finished water
are difficult to evaluate especially under short term experimental con-
ditions. Any adverse effect of land treatment on soil, crop or ground-
water most likely will only be detected from studying long-term waste-
water application sites. Through efforts by the U.S. Environmental
Protection Agency, long-term environmental effects of wastewater land
application sites have been extensively investigated 1n the past ten
vears.
-------
Page 112
CHANG AND PAGE
During the past 10 years, treatment performance of several large
scale slow rate wastewater land application treatment systems have been
studied (Seabrook, 1975; Hossner et al., 1978; Demlrijlan, 1980). Envir-
onmental impacts at many long-termKomestlc wastewater Irrigation sites
throughout the U.S. were Investigated (Benham-Blair and Associates, Inc.
and Engineering Enterprises, Inc., 1979a; Koerner and Haws, 1979a1
Overman, 1979; Stone and Rowland, 1980a; 1980b). Trace metal loadings
did not limit the land application of wastewater 1n any of the above
systems studied. Although metal contents of applied wastewater and hy-
draulic loading varied extensively, all studies reported significant re-
duction of trace metals by land treatment (Table 2).
Table 2. Trace metal behavior during slow-rate land treatment.*
Treatment Location
Max. „ ¦ i.*=u biiicii t LUC4 C 1 01
Contamin. Applied Muskegon, HI San Angelo, TI
Level 1n Wastewater EffT. tffl.
Element NIDWR2 Conc'n Cone'" Removal Conc'n Removal
— (mg.L"1) (mg-L'Tf(mg-L"1) (D (mg-L"1)(%}
Cd
Cr
Cu
Pb
Mn
Hg
Zn
0.01
0.05
1.0
0,05
0.05
0.002
5.0
0.004-0.14
0.02-0.7
0.02-3.4
0.05-1.3
0.11-0.14
0.002-0,05
0.03-83
MelDourne Aust..
mr.
Conc'n Removal
40
15
95
<0.004
<0.005
0.014
<0.005
0.102
>98
85
25
0.002
0.03
0.02
0.01
0.0004
0.04
T-from IHga arterites, 1980.
2 National Interim Drinking Water Regulations.
80
90
95
95
85
95
Regardless of the trace metal content .
effluents were consistently below !»,(«,,„ Influents, concentrations 1n
by the National Interim Primary DrlnH™ £°"tan,1nnat1°n levels permitted
removal efficiencies in land treatn^St ?80 Resu1atj0"s- s^ce the
total trace metal normally expected fn L ^ exceeded the fraction of
pended solid form, mechanisms other Present 1n wastewater 1n sus-
also have been active in attenuatfna trs™ strain1ng and filtration must
plication, no crop was adversely j1"! ' During wastewater ap-
relatively little increase 1n tra/J , y t?ce metaTs* There was
wastewater over those Irrigated uifh , uPt™e by plants recelvlna
(Table 3). The accumulation 0f trara *ater of non-wastewater origin
water 1s directly proportional tn inn"f « so*'s receiving waste-
metals added Into soils through siftw "J! s* Because amounts of trace
tlon to total volume of soils cma1f wastewater application in rela-
affected soils may not be signify' trace metal concentrations fn
adequate time, accumulation of trar« ,'evated for some time. Given
I" soils win become evident
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Hydrologic Management: Trace Metals
Page 113
Table 3. A comparison of chemical constituents In the plant tissue (an
unspecified grass) from sites irrigated and not Irrigated with
wastewater effluent for 17 years at Dickinson, North Dakota
(derived from data 1n Benham-Blair and Associates, Inc. and
Engineering Enterprises, Inc. 1979a).
Constituent
Control
Wastewater Irrigation
- - - -
- - yg g"l dry wt.
N
19
15
P
2.7
2.7
K
5.1
4.3
Na
1.2*
3.1
S
1.2
1.1
(no2+no3)-n
0.7
1.0
As
<0.001
<0.001
B
0.14
0.20
Cd
<0.005
<0.005
Cr
0.002*
0.005*
Cu
0.007
0.007
Pb
<0,005
<0.005
Zn
0.022*
0.037*
~Control and wastewater
level.
treated are
statistically different at the 0.05
(Bouwer and Chaney, 1974). However, almost all trace metals Introduced
through wastewater applications are deposited 1n the surface 20 cm
(Hossner et al., 1979). Obviously, soil's ability to retain trace metals
is not unTTmTted, The capacity for metal removal 1n soils 1s expected to
be equal to or better than retention of phosphorus. For a wastewater
with a typical trace metal content, 1t will take several hundred years
for a slow rate land treatment operation to exhaust the cation exchange
and specific adsorption capacity of a typical soil.
Rap1d-Inf11tration Treatment
In order for a land treatment site to receive large amounts of
wastewater, highly permeable soils and a fast draining aquifer are ne-
cessities. Large volumes of water draining rapidly through the soil pro-
file will also Influence treatment performance. Soils with acceptable
hydraulic properties usually do not possess high adsorption capacities.
Because of the high hydraulic loading, kinetics of chemical reactions 1n
soils may be critical 1n the degree of trace metal attenuation achiev-
able. Character1s1cally, rapid Infiltration systems are not suitable to
handle wastewater with a heavy pollutant load.
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Page 114
CHANG AND PAGE
Results obtained from studying rapid-infiltration systems in the U.S
demonstrated that effluents of satisfactory quality may be produced with
either primary effluents or secondary effluents as input water. Most
short duration operations {<5 years) showed effective immobilization of
trace metals by the soil matrix (Smith et aj_., 1979; Vaccaro et al.,
1979). However, when trace metal contents of renovated water at"several
long-term rapid-infiltration systems (>10 years) were compared with those
from control wells, concentrations of several trace metals in renovated
water were significantly elevated (Table 4). Elevated levels of iron and
manganese originating from indigeneous Fe and Mn oxides in soil were re-
duced under conditions created by wetting cycles. Higher concentrations
of other metals, such as As, Cd, Ni, and Zn, were also found in the re-
charged groundwater. Generally, the metal concentrations of the reno-
vated water did not appear to be significantly different from the water
applied (Benham-Blair and Assoclates,Inc. and Engineering Enterprises,
Inc. ei^al., 1979b; Koerner and Haws, 1979b; Leach et a^., 1980; Pound et
al., 1978J. Similar results also have been reported by other investiga^
tors {Bouwer et ah, 1974; Aulenbach, 1979). Although their extremely
low concentratTons 1n the water are not likely to interfere with the
beneficial use of the groundwater aquifer, the available data, neverthe-
less, demonstrates that trace metals may be transported into groundwater
aquifers through long-term rapid infiltration operations. Data from
rapid infiltration systems also show significant accumulation of trace
metals near the surface of the affected soil profile. At Whittier
Narrows (Los Angeles County, CA), secondary effluents have been used for
artificial groundwater recharge since 1963 at an annual average rate of
83 m yr~l. Sampling the recharge spreading basin in 1980 indicated
significant amounts of trace metals were deposited in the surface 60 cm
of the soil profile (Table 5). The average concentration of 4JN HNO
extractable metals in the surface 60 cm of soil, normalized to account
for different depth increments by assuming a uniform bulk density for
soil of 1.5 g cm"3, increases from 0.1, 38, 51, 32, 5.3, and 73 to 3.1,
128, 116, 112, 44, and 241 ug g"1, for Cd, Cr, Cu, Ni, Pb, and Zn respec-
tively. The removal of trace metals from the applied wastewater in the
upper 60 cm soil layer was likely due to the result of filtration of
suspended solids and compounds precipitated during water application.
More Importantly, the accumulation of trace metals 1n the soil profile
has elevated the concentration of soluble trace metals in the surface of
the affected soils (Table 6), enhancing the leaching of trace metals to
deeper soil strata.
Overland Flow System
Overland flow treatment systems have long been used to treat food
processing wastes. However, the effectiveness of these systems in
treating domestic wastewater was not demonstrated until recently (Thomas
et al., 1974; Overcash, 1978; Hall et ah, 1979; Hinrichs et al., 1980).
UespTte the popularity of land treatment in the past 10 years,"Tull scale
municipal treatment facilities using overland flow are not extensive.
-------
Table 4. Comparison of trace metal content in groundwater of long-term rapid-1nfiltrat1on systems with
their corresponding controls.1
Parameter2
Hoi lister, CA
Lake George, NY
Vineland, NJ
Milton, WI
Control 1
Renovated
Control Renovated
Control
Renovated
Control
Renovated
Preapp. Treatment
Primary
Secondary
Primary
Secondary
Operation Period(yr)
30
38
50
40
Applic. Area
(ha)
8,
.8
2.2
36
0.2
Hydraulic Load.(m*yr_i)
15,
.4
44.7
11
-21.4
11C
1-224
Daily Flow (L
*s-M
43,
.8
30.8
215
14.5
Depth of Groimdwater(m)
6.8-
-9.2
1.3-7.0
1
.0-3.5
2.
0-3.0
pH
7.8
7.7
6.6-7.8 6.5-7.4
5.2
6.6
7.7
7.5
EC (dS«m
-1) 1.148
1.828
-
0.064
0.468
0.677
1.379
BOD
3
13
1.2 0.8-3.0
1.1
65
18.0
36
As
<0.01
0.01
_ _
0.006
0.01
0.005
0.033
Fe
0.03
0.51
2*24 0,43-8.25
1.6
12.6
0.50
2.0
Hg
<0.001
0.001
-
0.001
0.001
0.001
0.001
Mn
0.01
0.62
-
0.11
0.13
0.10
0.29
Ni
0.039
0.16
-
0.10
<0.10
0.10
0.10
Pb
0.012
0.08
-
0.10
0.10
0.20
0.20
Se
<0.001
0.001
-
0.01
0.01
0.05
0.005
Zn
0.05
0.090
-
0.013
0.024
0.628
0.254
Ba
<0.07
0.15
.
-
-
-
-
Cd
<0.003
0.050
-
0.02
0.02
0.02
0.02
Co
<0.006
0.013
-
0.05
0.05
0.05
0.05
Cr
0.032
0.017
-
0.03
0.02
0.05
0.05
Cu
0.025
0.036
_
0.02
0.023
0.10
0.10
A1
—
—
-
1.8
0.50
1.0
1.0
1 From Leach et aU 1980.
2 Expressed in mg*L-1 except pH or otherwise indicated.
-------
Page 116
CHANG AND PAGE
Table 5. Accumulation of trace elements 1n soils used for groundwater
recharge (Whittier Narrows, Los Angeles, Cft).1
_ Concentration of Element In Soil fg"1)
(cm)
Cd
Cr
Cu
Ni
?b
RECHARGE
AREA2
0-5
2.3
88
69
71
61
5-15
5.6
215
128
145
79
15-30
3.4
111
117
128
34
30-60
2.2
95
86
84
21
60-90
0.9
46
42
44
6
90-120
0.3
27
31
37
5
120-180
0.2
31
37
45
6
CONTROL
AREA3
0-5
0.2
32
41
26
9
5-15
0.1
33
45
27
5
15-30
0.1
27
41
24
5
30-60
0.1
40
51
333
3
60-90
<0.1
14
19
13
1
90-120
<0.1
20
27
60
1
120-180
0.1
25
45
31
-
Tn
176
322
209
136
73
62
75
83
83
65
83
40
61
86
Table 6.
Concentrations
of trace elements in soil
saturation extracts
of soils used
for artificial groundwater recharge (Whittier
Narrows, Los Angeles
, CA).
Depth
Concentration of
Element in Soil Satu
ration
Extract(yq L"1)
(cm)
Cd
Cr
Cu
W
Zn
RECHARGE AREA*
0-5
1.4
11
222
115
34
5-15
1.2
22
210
88
26
15-30
0.2
24
119
56
20
30-60
<0.1
33
121
65
16
60-90
<0.1
18
93
56
17
90-120
<0.1
5
80
53
16
120-180
<0.1
5
69
40
20
CONTROL AREA3
0-5
1.4
2
<20
194
79
5-15
0.2
2
<20
181
73
15-30
0.2
2
<20
181
70
30-60
0.2
<2
<20
<25
70
60-90
0.2
<2
<20
<25
70
90-120
0.4
<2
<20
<25
68
120-180
0.1
<2
<20
<25
76
1 Derived from Chang and Page 1983.
2 Mean of 4 samples collected from recharge basfns which had received
secondary wastewater from 1963 through 1980.
3Results from one sampling location adjacent to the recharge basins.
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Hydrologic Management: Trace Metals
Page 117
For domestic wastewater, overland flow may be used to polish secon-
dary effluents or achieve secondary level treatment. In terms of treat-
ment performance, the overland flow land treatment systems used for the
latter case generally have out-performed conventional secondary treatment
1n publicly owned treatment works (Hall et al., 1979). In either case,
substantial nutrients and trace metals removaTs 1n addition to suspended
solids and BOO reductions are achieved.
Conceptually, process mechanisms of overland flow treatment systems
resemble a conventional attached growth biological treatment system minus
sludge withdrawal. Although performances of overland flow systems mea-
sured in terms of BOD and suspended sol Ids removal, may be Influenced by
water distribution methods, soil slope, soil temperatures, etc., and are
far from consistent, it has exhibited effective retention of trace
metals. The mass balance data from a pilot system at Utlca, Mississippi
show, for example, that less than 10% of the applied trace metals ap-
peared 1n the effluent (Table 7). As wastewater flows across the soil
surface, trace metals are adsorbed by organic solids deposited 1n the de-
composing layer and plant roots concentrating trace metals toward the
upper end of the soil slope. Although there 1s little operation data to
substantiate the author's claim, 1t 1s logical to expect that trace metal
deposited with organic solids at the soil surface are not as tightly
bound as those immobilized 1n the soil profile. Unless surface deposits
of overland flow systems are routinely removed, their capacities for
trace metal retention will sooner or later be exceeded.
Table 7. Distribution of trace metals in an overland flow treatment
system, Utlca, Mississippi.1
Percent of Total Applied
Element Effluent Veqetatlve Cover Sol 1
£d 175 77B 9T7T
Cu 4.0 14.5 81.5
N1 1.4 4.4 93.9
Zn 7J5 12^1 80.3
1 from Peters et al. 1980.
-------
Page 118
CHANG AND PAGE
CONCLUSIONS
1. Trace metals introduced into soils through land application may be
retained 1n the soil matrix by straining and filtration (for suspended
and colloidal solid forms) or by ion exchange and specific adsorption
mechanisms (for dissolved forms). Trace metals 1n dissolved forms may
also precipitate out of solution and subsequently be removed as suspended
solids.
2. Land treatment systems are customarily designed for optimum hydraulic
loading or removal of suspended solids and BOD. Reviewing operational
data of land treatment systems revealed that effective attenuation of
trace metals present 1n wastewater was also achieved. To date, trace
metals have not limited land treatment operations. However, trace metals
are accumulating in the surface of the affected soils under all modes of
land treatment.
3. For slow rate wastewater application, trace metal contents of efflu-
ents are reduced. Processes Involved 1n trace metal attenuation include
the physical mechanism of filtration and the chemical sorption by 1on
exchange and specific adsorption. Even after years of wastewater
spreading, crops did not exhibit any significant increase 1n trace metal
uptake. Under slow rate wastewater treatment, soils are expected to
possess an exceptionally large capacity to immobilize trace metals.
4. Results obtained from long-term operations demonstrated that trace
metals may be transported Into groundwater aquifers under hydraullcally
active rapid Infiltration systems. However, the adverse effect on the
quality of renovated water can be minimized by pre-appl 1 cation treatment.
In overland flow treatment, trace metals are deposited in the organic
layer near the soil surface and are less tightly bound than those Immobi-
lized In the soil matrix. Unless organic deposits of the overland flow
systems are removed routinely, their capacity for retaining trace metals
will sooner or later be exceeded.
5. To prevent long-term trace metal problems land treatment systems
source control and pre-applIcation treatment techniques should be Insti-
tuted to minimize metal concentration 1n wastewater applied.
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Hydrologic Management; Trace Metals
Page 119
REFERENCES
1* Aulenbach, D. B. 1979, Long-term recharge of trickling filter
effluent Into sand. U.S. Envtronmental Protectfon Agency.
EPA-600/2-79-068. 146 pp.
2. Benham-Blair and Associates, Inc., and Engineering Enterprises, Inc.
1979a. long-term effects of land application of domestic waste-
water: Dickinson, North Dakota slow rate Irrigation site. U.S.
Envlronmental Protection Agency. EPA-600/2-79-144.
3. Bertham-Blafr an
-------
Page 120
CHANG AND PAGE
12. Hathway, S. W. 1980. Sources of toxic compounds In household waste-
waters. U.S. Environmental Protection Agency. EPA-600/2-80-128.
84 pp.
13. Hinrichs, D. J., J. A. Falsst, 0. A. Pivettl and E. D. Schroeder.
1980. Assessment of current Information on overland flow treat-
ment of municipal wastewater. U.S. Environmental Protection
Agency EPA-430/9-80-002.
14. Hossner, L. R., Chun-Wei Kao, R. W. Weaver and J. A. Waggoner. 1978.
Sewage disposal on agricultural soils: Chemical and microbiolo-
gical Implications. Vol. 1: Chemical implications. U.S. Envi-
ronmental Protection Agency. EPA-600/2-78-131a. 119 pp.
15. Iskandar, I.K. 1978. History of land treatment of wastewater.
Proceedings, Symposium on Land Treatment of Waste Effluents.
Technical Report No. 48, Water Resources Research Center,
University of Maryland.pp. 6-11.
16. Ives, K. J. 1973. Filtration of water and wastewater. CRC
Critical Rev. Environ. Contr. 2:293-335.
17. Jewell, W. J. and B. L. Seabrook. 1979. A history of land applica-
tion as a treatment alternative. U.S. Environmental Protection
Agency. EPA 430/9-79-012. 83 pp.
18. Klein, L. A., M. Lang, N. Nash and S. L. Klrschner. 1974. Sources
of metals 1n New York City wastewater. J. Water Pollut. Control
Fed. 46:2653-2661.
19. Koerner, E. L. and D. A. Haws. 1979a. Long-term effects of land
application of domestic wastewater: Rosewell, New Mexclo slow
rate Irrigation site. U.S. Environmental Protection Agency.
E PA-600/2-79-047.
20. Koerner, E. L. and D. A. Haws. 1979b. Long-term effects of land
application of domestic wastewater: Vlneland, New Jersey rapid
infiltration site. U.S. Environmental Protection Agency.
EPA-600/2-79-072. 167 pp.
21. Leach, L. E., C. G. Enfield and C. C. Harlln, Jr. 1980. Summary
of long-term rapid infiltration system studies. U.S. Environ-
mental Protection Agency. EPA-600/2-80-165.
22. Levins, P., J. Adams, P. Brenner, S. Coons, G. Harris, C. Jones, K.
Thrun and A, Wechsler. 1979. Sources of toxic pollutants
found 1n Influents to sewage treatment plants. VI. Integrated
Interpretation. U.S. Environmental Protection Agency.
EPA-68-01-3857.
-------
Hydrologic Management1 Trace Metals Page 121
23. Lindsay, W. L. 1972. Inorganic phase equilibria of micronutrients
in soils. IN: Micronutrients in Agriculture. Soil Sci. Soc.
Am. Inc. Madison, Wisconsin, pp. 41-57.
24. Lindsay, W. L. 1973. Inorganic reactions of sewage sludge with
soil. IN: Recycling Municipal Sludges and Effluents.
National Association of State Universities and Land Grant
Colleges, Washington, D. C. pp.91-96.
25. Mattigod, S. V. and G. Sposito. 1979. Chemical modeling of trace
metal equilibria in contaminated soil solution using computer
program GEOCHEM. IN: (E. A. Jenne, ed.) Chemical Modeling in
Aqueous Systems. ACS Symposium Series No. 93, Amer. Chem.
Soc.
26. Minear, R. A., R. 0. Ball and R. L. Church. 1981. Data base for
influent heavy metals in publicly owned treatment works. U.S.
Environmental Agency, EPA-600/2-81-200. 273 pp.
27. Overcash, M. R, 1978. Implications of overland flow for municipal
waste management. J. Water Pollut. Control Fed. 50:2337-2347.
28. Overman, A. R. 1979. Wastewater irrigation at Tallahassee, FT.
U. S. Environmental Protection Agency. EPA-600/2-79-151. 320
PP.
29. Page, A. L., A. C. Chang, G. Sposito and S. Mattigod. 1981. Trace
elements in wastewater, their effects on plant growth and com-
position and behavior 1n soils. _In_: I. K. Iskandar (ed.)
Modeling Wastewater Renovation by Land Application. U.S. Arniy
Cold Regions Research and Engineering Laboratory, Monograph,
John Wiley & Sons, publisher, New York, NY, pp. 182-222.
30. Page, A. L. and A. C, Chang. 1981. Trace metal in soils and plants
receiving municipal Irrigation. IN: (F. M. D'ltM, J. A.
Martinez and M.A. Lambarri, eds.) Municipal Wastewater in
Agriculture. Academic Press, pp. 351-372.
31. Peters, R. E., C. R. Lee and 0. J. Bates. 1980. Field Investiga-
tions of overland flow treatment of municipal lagoon effluents.
U. S. Army Corps of Engineers Waterway Experiment Station.
Vicksburg, Mississippi.
32. Pound, C. E., R. W. Crites and J. V. Olson. 1978. Long-term
effects of land application of domestic wastewater: Hollister,
California rapid infiltration site. U.S. Environmental
Protection Agency. EPA-600/2-78-084. 150 pp.
33. Seabrook, B. L. 1975. Land application of wastewater in Australia.
U.S. Environmental Protection Agency. EPA-430/9-75-017.
-------
Page 122 CHANG AND PAGE
34. Sims, J. L. and W. H. Patrick. 1978. The distribution of micro-
nutrients cations 1n soil under conditions of varying redox
potential and pH. Soil Sci. Soc. Am. J. 42:258-262.
35. Smith, 0. G., K. D. Lindstedt and E. R. Bennett. 1979. Treatment
of secondary effluents by infiltration-percolation. U.S.
Environmental Protection Agency. EPA-600/2-79-174. 103 pp.
36. Stone, R. and J. Rowland. 1980a. Long-term effects of land appli-
cation of domestic wastewater: Mesa, Arizona irrigation site.
U.S. Environmental Protection Agency. EPA-600/2-80-061.
37. Stone, R. and J. Rowland. 1980b. Long-term effects of land appli-
cation of wastewater: Camarlllo, California irrigation site.
U.S. Environmental Protection Agency. EPA-600/2-80-080.
38. Thomas, R. E., K. Jackson and L. Penrod. 1974. Feasibility of
overland flow for treatment of raw domestic wastewater. U.S.
Environmental Protection Agency. EPA-660/2-74-087.
39. Uiga, A. and R. W. Crites. 1980. Relative health risks of acti-
vated sludge treatment and slow-rate land treatment. J. Water
Pollut, Control Fed. 52:2865-2874.
40. Vaccaro, R. F.t P. E. Kallio, B. H. Ketchum, W. B. Kerfoot, A. Mann,
P. L. Deese, C. Palmer, M. R. Dennett, P. C. L. Bowker, N.
Corwin and S. J. Manganini. 1979. Wastewater renovation and
retrieval on Cape Code. U. S. Environmental Protection Agency.
EPA-600/2-79-176.
41. Yao, K. M. Habibian and C. R. O'Melia. 1971. Water and wastewater
filtration: concept and application. Environ. Sc1. Tech.
5:1105-1112.
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FOREST SYSTEMS
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Page 125
THE ROLE OF FORESTS IN SLUDGE AND WASTEWATER UTILIZATION PROGRAMS
Dale W. Cole
Charles L, Henry
Peter Schiess
Robert J. Zasoski
College of Forest Resources
University of Washington
Seattle, Washington
Forested areas are receiving increased attention as potential sites
for the disposal and biological recycling of both wastewater and sludges
from municipal treatment facilities. The current sewage management
programs by the city of Bremerton in the state of Washington and by
Clayton County in Georgia exclusively use forested sites to effectively
arid economically reuse sewage treatment plant by-products (Reynolds and
Cole 1981, Snell et al. 1981). In both cases, the application rates are
designed to maintain a high standard of drainage water quality while also
enhancing the productivity of the forest crop. Similarly, municipal
sewage sludge from the greater Seattle area is now destined to be applied
to tree farms as a silvicultural tool to increase the productivity of
forest stands (Metro 1983). It is the purpose of this article to discuss
the underlying concepts that have given rise to this newly emerging
technology for incorporating forestry into a sludge and wastewater
utilization program.
There are a number of obvious reasons for considering forested sites
as potential candidates for the disposal and reuse of sewage from a
municipal treatment plant:
1. In many regions of the United States extensive acreages of
forest land are potentially available for such a program.
Forests occupy 40% of the landscape in the contiguous
forty-eight states.
2. Forests are typically located in the better drained sites and
not subject to the periodic flooding of alluvial agricultural
areas.
3. Many of the forests in the United States are markedly deficient
in major nutrients that are found in municipal sludge and
wastewater, especially nitrogen and phosphorus.
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Page 126
COLE, HENRY, SCHIESS AND ZASOSKI
A lack of adequate nutrition is the main factor limiting forest
productivity in this country.
4. Since forests are not food chain crops, many of the public
health concerns and land application regulations should not be
as critical as those associated with agricultural sites.
5. Forest soils theoretically have properties well suited to
receive sludge and wastewater additions, including a great deal
of organic carbon which will immobilize available nitrogen, a
high infiltration rate which should minimize the potential for
surface runoff, and a perennial root system which should allow
for year round uptake of available nutrients.
The application of these products in a forest environment has not
been without its critics and problems. It has been argued that such
additions are in conflict with traditional uses of the forest, especially
those involving recreation. For example, concerns over heavy metal
uptake by edible mushrooms and berries have been raised. It has also
been suggested that sewage additions could adversely affect the forest
wildlife, and through such wildlife, toxic substances might enter the
human food chain.
What might be regarded as more tangible concerns have also been
raised. One is that many forest sites are located on areas of excessive
slopes which could allow escapement of sludge particulates or dissolved
solids through surface water runoff. Another is the concern that tree
species in their natural setting generally take up far fewer nutrients
than agricultural crops, possibly resulting in more time for nutrient
transformation or escapement. Not all tree species respond significantly
to nutrient additions, and to convert a site to a more desirable species
could take a number of years. Most important, it has been pointed out
that there is much less experience and substantive research dealing with
forest applications than with agricultural applications, and therefore
the design of sludge use for a forest site is more speculative.
In order for forests to play a significant role in a land applica-
tion program, such questions and concerns must be addressed. Research
has been under way both in this country and elsewhere for well over a
decade examining the effects of applications in forested sites. Examples
of such work include Kardos and Sopper (1973) in Pennsylvania, Urie
(1973, 1979) and Harris and Urie (1983) in Michigan, Bialkiewicz (1978)
in Poland, Nutter et al. (1978) in Georgia, and Cole (1982) in
Washington. Not all the results from these studies have been favorable.
It is clear that excessive applications can result in detrimental
environmental effects such as significant nitrate leaching (Sopper and
Kerr 1978, Riekerk 1978, Vogt et al. 1981, Urie 1973, Brockway and Urie
-------
Forest Systems
Page 127
1983). Growth trials point to the wide range of responses that can be
expected from various tree species and stage of tree growth (Cole 1983,
Smith and Evans 1977, Koterba et al. 1979), some of which are far from
favorable. The fates of heavy metals and pathogens have not been as
extensively explored in forest sites as in agricultural ones, although
the initial results as reported by Zasoski (1981) and Edmonds (1979)
would indicate this issue is of lesser concern.
A major initial problem in establishing forest application sites was
the lack of adequate application equipment technology. Equipment that
had been developed for agricultural fields was generally not suitable for
the broken terrain of a forested site.
These and other problems have now been largely resolved, and fully
operational forest sites now receive sludge and wastewater additions.
The bases for such additions and the expected forest responses are
outlined below. While the results for this discussion have been largely
derived from our studies concerning both wastewater and sludge carried
out at Pack Forest (the research and demonstration forest of the College
of Forest Resources, University of Washington, located 75 miles south of
the campus in the foothills of the Cascade Mountains), the experiences
and results of other investigators are cited where appropriate.
WASTEWATER APPLICATION PROGRAM
In general, it is easier to design a wastewater application program
than an application program for either 425 or dewatered sludge.
Wastewater contains significantly less in the way of heavy metals or
pathogens than sludge. Such items are largely retained by the sludge in
the treatment plant separation process. Consequently the design of a
forest application site need only match the application rate to the
ability of a site to store and utilize the nutrients being added and to
hydraulically accept the irrigation rates. To develop some design
criteria for a forest wastewater application system, a series of field
experiments was undertaken at our Pack Forest site. Study plots were
located on well drained glacial outwash soil. In this program, both
young plantations of poplar and Douglas-fir and an established
Douglas-fir forest were irrigated with 5 cm/wk of wastewater from the
Metro treatment facility for the city of Seattle. To provide controls
and comparisons with other land application alternatives, barren (all
vegetation removed) and grass sites were also included in the
experimental design. Each site was subdivided so that one section
received wastewater while the remainder received an equal amount of water
pumped from the adjacent river. Irrigations were conducted weekly on a
year-round basis over a five-year period (1974-79).
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Page 128
COLE, HENRY. SCHIESS AND ZASOSKI
Consequently, each plot except for the 50-year-old Douglas-fir stand
received a total of over 12 meters (40 feet) of irrigation and
approximately 2000 kg/ha of total nitrogen. Movement of percolating
waters through the soil profile to a depth of 180 cm was carefully
monitored with both tension lysimeters and a large tank lysimeter system,
3.5 meters in diameter.
A number of important conclusions were derived from this study.
Phosphorus contained in wastewater was quickly and completely removed
from the soil solution by a sorption reaction on the soil colloidal
surfaces (Breuer et al. 1979). Thus phosphorus did not leach through
any of the plots, including the one maintained in a barren state.
Leaching of nitrogen showed a somewhat different pattern. As long as
the added nitrogen remained in ammonium form, little if any leaching was
apparent. But with the conversion of ammonium to nitrate, leaching
became rapid and extensive. On those plots with a vegetative cover this
loss of nitrogen was minimized through plant uptake or soil storage
(Table 1; Cole 1982).
Table 1. Fate of nitrogen applied as wastewater to plots at Pack Forest
from 1974 to 1979 (Schiess and Cole 1981).
Poplar Douglas-fir Grass Barren Douglas-fir
Forest
— (kilograms/hectare)
Input
2,171
1,811
2,217
2,286
1,333
Vegetation
272
0
2
accumulation
317
0
Harvest
930
621
627
0
0
Leaching j
Soil accumulation
253
437
271
1,252
120
671
481
1,319
1,034
" —
I Residual of input minus plant uptake and leaching loss.
Not determined.
Irrigation of wastewater resulted in a dramatic increase in biomass
production (Table 2). Average aboveground production on the poplar
plots irrigated with wastewater was 25 t/ha, approximately 7 times higher
than the river water control. The wastewater irrigation resulted in an
increase in aboveground production of nearly 4 times for the Douglas-fir
seedlings and 3.5 times for the grass plot over the irrigation with river
water.
-------
Forest Systems
Page '29
Table 1, Aboveground biomass production (t/ha) by young Douglas-fir
and poplar plantations and grass as a result of wastewater and
river water irrigation (Schiess ano Cole 1981).
Wastewater River Water
Tree
Grass
Total
Tree
Grass
Total
(tonnes/hectare)
Poplar
1576
8.5
8.0
16.5
1.0
1.6
2.6
197?
28.2
6.0
34.2
1.2
1.2
2.4
1978
14.8
10.1
24.9
l.B
2.1
3.9
1979
18.4
6.0
24.4
3.4
1.9
5.3
Douglas-fir
2.9
8,5
11.4
0.9
1.6
2.5
1977
4.4
8.4
12.8
1.6
0.8
2.4
1978
14.0
6.7
20.7
3.8
2.2
6.0
1979
12.8
3.4
16,4
3.6
1.3
4.9
Grass
1476
8.5
3.5
1977
9.1
0.9
1978
10.4
3.9
1979
10.2
From this research it was possible to calculate renovation capaci-
ties of the five plots over the five-year period of the experiment (Table
3). It is clear from these results that forests can effectively renovate
wastewater at applicatior rates normally used in agriculture. In this
case, however, applications were made over the entire year and not just
during t^ie growing season, as is typical in agricultural practices.
Results from the forest plots compared very favorably with results from
the plot with grass cover. Nitrate-N concentrations at 180 cm depth were
nearly always below 10 pprr EPA drinking water standards. Both the
forested site and poplar seedlings demonstrated excellent renovation
potential, with only 10ft nitrogen escapement below the rooting zone
during the five-year period of application. Escapement losses front grass
and Douglas-fir seedlings were only slightly higher and nitrate-K nearly
always remained within the 10 ppm concentration standard.
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Page 130
COLE, HENRY SCHIESS AND ZASOSKI
Table 3. The renovation and retention capabilities of a gravelly soil
for total nitrogen under wastewater irrigation applied to four
vegetation covers and a barren control (Schiess and Cole
1981).
Vegetation Cover
Year
Douglas-fir
D.-fir
Applied
Barren
Grass
Poplar
Seed!i ngs
Forest
(kilograms/hectare)
1975
428 (68%)
428 (96%)
428 (53%)
428 (89%)
«...
1976
403 (34%)
398 (76%)
392 (94%)
320 (84%)
384 (84%)
1977
456 (75%)
443 (77%)
438 (98%)
325 (74%)
402 (97%)
1978
449 (59%)
437 (96%)
440 (99%)
359 (76%)
350 (97%)
1979
550 (39%)
509 (93%)
473 (98%)
379 (54%)
253 (83%)
Average
457 (55%)
443 (88%)
434 (88%)
362 (76%)
333 (91%)
^Values are kg/ha nitrogen applied, with percent retained indicated in
parentheses.
It could be concluded from these studies that forested sites in
Washington can be used effectively for wastewater renovation. Since
forest response was very favorable, such applications have the potential
of providing a significant economic return to the forest owner. An
economic analysis was not made of this data, however, because of the
small size of plots and limited design of the experiment. But an
economic analysis was made in the case of sludge-treated plots and will
be discussed in the next section.
While these results cannot be directly applied to other areas, it
does appear from the literature (McKim 1978, Sopper and Kardos 1973,
Sopper and Kerr 1979) that forests in general are excellent sites for the
effective disposal of effluents from sewage treatment plants. The most
important criteria to keep in mind are: (1) tree species with a high
growth and nitrogen uptake potential should be used, (2) soil should be
at least moderately well drained so that saturation and poor aeration
conditions do not develop, and (3) year-round irrigation can be carried
out only where the climatic conditions allow. Irrigation during periods
of freezing could well cause physical damage to the forest.
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SLUDGE APPLICATION PROGRAM
As mentioned above, the design of a sludge application program is
somewhat more difficult and perhaps uncertain than design of a wastewater
program. This is partly because of the association of pathogens and
heavy metals with sludge and less with the effluent component of a
treatment plant discharge. In addition, the technology of applying
sludge, especially when it has been dewatered, is far more difficult than
that of wastewater. The biological and chemical reactions of sludge
within the soil are not as well understood. This affects the
predictability of potential heavy metals mobility and the rate of
nitrogen release from organic matter to available nitrogen forms.
Without careful management controls, sludge can be lost from an
application site through surface erosion. This is especially critical in
a forestry application where slopes tend to be steeper than those found
in agriculture.
A sludge application program designed for forestry must take these
considerations into account. To provide an informational base for
developing such an application program, research was initiated at the
Pack Forest site in 1973. The studies conducted at Pack Forest enabled
researchers to take advantage of the diverse soil conditions this site
has to offer. Study plots were located both on well drained glacial
outwash soil as well as shallow residual soils originating from andisitic
parent material. A detailed account of this decade of research is
available in the symposium proceedings "Municipal Sludge Application to
Pacific Northwest Forest Lands" (Bledsoe 1981) and the bulletin "Use of
Dewatered Sludge as an Amendment for Forest Growth" (Henry and Cole
1983). This research addressed most aspects of a sludge application
program in forestry, including:
1. Environmental soundness of applying sludge to forest areas.
The major focus of this research has been on nitrate leaching,
heavy metal uptake by the vegetative cover and leaching through
the soil profile, and residence time and distribution of
pathogens associated with sludge materials.
2. Long- and short-term growth response of various forest species
of the Pacific Northwest to these applications. Both newly
established plantations and existing forests have been studied
at Pack Forest.
3. Management alternatives, engineering problems, and general
economic costs and benefits of applying sludge to forest sites.
It is clear from the results of this research that sludge can be
used effectively to Increase forest productivity without causing
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COLE, HENRY, SCHIESS AND ZASOSKI
significant environmental problems. Some of the important findings
relevant to the use of sludge as a silvicultural tool in forestry are
discussed below.
Public Health and Environmental Considerations
The fate of heavy metals, pathogens, and nitrates associated with
sludge applications to these forested areas has been systematically
studied. Although it could be argued that forests are essentially
removed from the human food chain and such public health considerations
are unnecessary, it is also argued that people frequent such sites,
harvest food products from them, and obtain much of their drinking water
from drainages originating in forested areas. Consequently a number of
public health issues were considered as part of this overall research
effort.
The question of heavy metal uptake, toxicity, and leaching has been
addressed in a number of studies at the Pack Forest site. As a worst
case example, 18% dewatered sludge from the Metro treatment facility was
applied to a depth of 25 cm at four different sites. The vertical
migration of cadmium, copper, nickel, lead, and zinc was followed for a
period of two years. This study clearly demonstrated that there was only
a minimal migration of these metals into the underlying soil despite the
general acidic conditions. Nickel demonstrated the greatest mobility,
migrating to a depth of perhaps 50 cm at the site with the lowest pH
(approximately 4.5 in B horizon). For the remaining sites and heavy
metals, vertical migration was limited to the top 10-20 cm of soil
(Zasoski 1983). In general, it was found that in areas treated with
sludge, heavy metal accumulation by the native vegetation could be lower
than for crop species growing on sites with no sludge history (CAST
1980). It should be recognized, however, that significant differences in
accumulation between native species were evident (Zasoski 1981). In
addition, metal uptake from sludge-amended soils by conifer and deciduous
species has been evaluated in nursery beds and found to be relatively low
(Bledsoe and Zasoski 1981). Based on these observations, it appears that
heavy metal uptake by native vegetation and tree species is elevated by
sludge additions, but such increases are small arid phytotoxicities are
not evident.
Residence time and mobility of sludge-related pathogens have also
been followed in our forest sites. While most of these studies have
utilized fecal and total coliform bacteria as indicator organisms, virus
and other pathogenic organisms have also been studied to a more limited
extent. Residence time of fecal coliform in a 10 cm application of
sludge is less than two years following application to forest sites.
This residence time is further decreased if sludge has been applied to
recently harvested sites or applied during the summer months. There
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Forest Systems
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appears to be little evidence of any downward migration of the fecal
coliform in the soil. Soil samples taken directly beneath sites
receiving sludge have a very low fecal coliform count. In addition, this
elevated occurrence of fecal coliform in the soil is short-lived,
disappearing within six months. There has been no evidence of fecal
coliform in the groundwater table directly beneath treated areas (Edmonds
1979).
The loss of nitrogen from sludge-treated sites is far more difficult
to control. Although much of the nitrogen within sludge is in organic
and ammonium forms and thus not easily leached, it can be leached follow-
ing mineralization and nitrification. The rate of leaching is therefore
controlled by a series of processes not only including mineralization and
nitrification but also denitrification, volitilization, immobilization by
soil organisms, and uptake by the vegetation. In order to establish
application rates that will minimize losses through leaching and at the
same time promote tree growth, it is essential to have an understanding
of the rates and durations of the reactions listed above. Studies have
been initiated at Pack Forest to quantify these various nitrogen trans-
formation processes {Riekerk and Zasoski 1979, Vogt et al. 1981, Cole and
Henry 1983). From these studies it would appear that a single applica-
tion in excess of 40 dry t/ha could result in some nitrate leaching
during the first year following application.
Stability of Sludge
As discussed in the introduction, much of the forest land,
especially in the West, is located on relatively steep slopes. Since the
U.S. Environmental Protection Agency has defined slopes in excess of 12%
as "potentially unsuitable areas", much of our forest lands could be
classified as unsuited for sludge applications. Slope studies were
undertaken at Pack Forest to establish whether this limitation is applic-
able to forest conditions or should remain only an agricultural guide-
line. This research involved the application of sludge to existing
slopes and to a slab that could be tilted to any desired angle. De-
watered digested sludge (17% solids) was applied to these surfaces at
various depths ranging from 1 to 5 cm. It was demonstrated through this
research that sludge up to 5 cm deep could be safely applied to undis-
turbed forest floor surfaces on slopes in excess of 23%. Sludge depths
of 2.5 cm could be applied to surfaces of approximately 403S with only
minimal downward movement (Henry 1983). It was concluded from this re-
search that the slope guidelines developed for agricultural conditions
are not necessarily appropriate for use in forestry. A more reasonable
guideline in forestry would allow sludge applications of 2.5 cm (45
ton/ha) to slopes up to 30%.
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COLE. HENRY, SCHirSS AND 2ASOSKI
Application Alternatives
The technology developed to apply sludge to agricultural sites is
not easily transferable to forest sites. A forest application vehicle
must be able to negotiate sloped and broken terrain. Even more critical,
the vehicle must be able to deliver sludge into the forest, necessitating
a system capable of pumping sludge a distance of 30 to 50 meters through
the air. To serve this purpose, a cannon-mounted sludge application
vehicle was designed and built as part of the research program at Pack
Forest (Nichols 1980).
Without such a vehicle, sludge applications in forests would be
limited to cleared sites with the actual applications made prior to
planting. This option, extensively tested under a number of site
conditions, proved to be impractical (Wi1 bert and Archie 1981). Unless
intensive efforts are made to control unwanted weed species, high
seedling mortality and poor growth result. This is due primarily to the
excellent response of the unwanted plants to the sludge application,
resulting in excessive competition with the tree seedlings for both
moisture and space. In addition, the higher nutritional environment in
the sludge-treated areas can result in selective browsing by deer on tree
seedlings. Sludge-treated sites can also provide excellent habitats for
voles, which -- left uncontrolled -- will girdle the young trees.
Because of these many difficulties in plantation management
following a sludge application, it has been concluded from our program at
Pack Forest that applications in forestry should be limited to planta-
tions on natural stands where the trees are well established. We would
recommend that the trees be a minimum of 2 meters high before they
receive their first application. In this way they are well above brows-
ing activities by deer. More important, the increased productivity that
sludge provides a forest site will be reflected in the tree seedlings and
not the weeds.
If the sludge is pumped over the canopy of a young forest, care must
be exercised not to damage the foliage. The easiest way of accomplishing
this is to limit applications to the high rainfall periods and/or the
dormant stage of the growth cycle. In western Washington we recommend
such applications be limited to the winter months prior to the flush of
growth beginning in late April.
In well-established forests, sludge can be applied beneath the
canopy and thus there is no seasonal limitation. However, it is our
general conclusion from both the sludge application program and fertili-
zation with commercial chemical fertilizers, that younger stands are more
responsive. For Douglas-fir in the Pacific Northwest the most desirable
age for applying sludge seems to be between 10 and 30 years.
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Growth Response
From the point of view of the forest manager, the purpose of apply-
ing sludge to forested sites is to achieve a growth response. In
general, we have found most of our forest sites and many of our forest
species responsive to sludge applications. This experience parallels our
earlier results from the addition of chemical fertilizers. It should be
recognized, however, that not all species and sites have demonstrated a
response. This is partly caused by secondary factors such as weed
competition, deer browsing, and vole girdling, as previously discussed.
It also appears that some species and some sites have a better response
potential than others. This variable response is evident from our
program at Pack Forest, as discussed below.
Species trials. Twelve species have been tested for their growth
response potential at Pack Forest. Since these seedlings have now been
growing in sludge-treated areas for three to four years, growth and
mortality results can be viewed with some confidence (Table 4).
In general, an excellent response was noted for all species tested.
The most dramatic growth was for a hybrid cottoriwood (Populus trichocarpa
x P. deltoides): after four growing seasons the height now exceeds 6.5
meters^ In this trial the average height response for deciduous trees
exceeded that of conifers by nearly three tines. The average diameter
growth responses were nearly equal (Table 4).
Application over a plantation canopy. Growth response from over-
the-canopy applications is limited to only one year of observations.
Results, as one might expect, are highly variable in that a number of
site conditions and application periods were tested (Table 5). The
poorest response (a net decrease of 303S in height growth) was found on a
site where sludge had already been applied. The greatest response was
noted on a residual soil derived from an andesitic bedrock material.
Although we believe an over-the-canopy application can be successfully
carried out and has an important potential in a forest application
program, additional research is clearly needed before this can be
regarded as operational. Evidence so far indicates that young
plantations that are not well established should be avoided. One should
also avoid applying the sludge during the growing season, because foliage
will be damaged or at least rendered nonfunctional for photosynthesis
unless the sludge is washed off. From our initial observations, an over-
the-canopy application is more suited to a well established forest,
(perhaps 10-70 years old} rather than a newly established plantation.
Application to older forests. A very successful technique of
applying sludge to forests is to apply it below the canopy using our
sludge-application vehicle. The percent growth responses are not as
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COl.L', HfNHY SCHIl. SS AND 7ASOSKI
Table 4. Diameter and height growth response over control for various
tree species established in sites receiving approximately 10 cm
of sludge {160 dry t/ha).
Current
Height
D idmeter
Species
Age
Response
Response
(percent)
(percent)
Douglas-fir
4
64
150
Western hemlock
4
370
690
Sitka spruce
4
140
225
Western redcedar
4
65
115
Cottonwood
4
320
585
Hybrid cottonwood
4
590
895
Poplar
4
1,190
—
Redwood
3
575
1,035
Grand fir
3
20C
1,250
Sequoia
3
290
1,035
Basswood
3
200
125
Birch
3
900
690
All conifers
270
645
All deciduous
640
560
* Age since establishment
Table 5. First-year growth response for Douglas-fir receiving an over-
the-canopy sludge application (2 dry t/ha).
Site Plantation Age Soil Height Response Diameter Response
(percent) (percent)
Val 9 Glacial -8 9
XAA 6 Glacial -30 -18
Hugo 6 Residual 180 330
27 10 Glacial 10 60
M-S 5 Glacial 1 -2
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dramatic as those reported above in the species trial, simply due to the
size and age of the stands. But excellent responses have been noted for
Douglas-fir, the only species tested thus far in this way (Table 6). The
best responses were found on the lower site classes. This is consistent
with results from urea applications to commercial forest lands. In the
case of sludge, the growth responses are substantially larger than the 25
to 30 percent response obtained from urea fertilization (RFNRP Staff
1976).
Table 6. Average diameter growth response for Douglas-fir
over a four-year period at three sites located at
Pack Forest.
Treatment Diameter Growth Response
cm percent
59-year-old
stand, site IV:
Control
.13
SIudge
.24
85
Control, thinned
.40
Sludge, thinned
.60
50
53-year-old
stand, site II:
Control, thinned
.54
Sludge, thinned
.62
15
25 to 50-year-
•old stand, site V:
Control, thinned
.67
Sludge, thinned
1.17
75
Recommended application rates. The research on sludge applications
to forests has clearly demonstrated the potential of a substantial growth
response, as documented in the previous section. This research has also
shown that the application of sludge can result in nitrate leaching if
the uptake and storage potentials of the system are exceeded. Following
ttie format used for determining sludge applications in agriculture
(Sommers 1980), we have calculated application rates for forest
conditions (Table 7). It is clear from these calculations that an
application in excess of 2 cm can potentially result in a nitrate-N
leaching loss exceeding 10 ppm as measured below the rooting zone. This
-------
Table 7. Nitrogen transformations and utilization for various application rates--year 1
(conceptual model, not actual values) (Cole and Henry 1983).
Soil
Storage
Organic
Ammonia
Mineralized
Volatilized
Leached
Dry
Nitrogen
Nitrogen
Nitrogen
Nitrogen
Temporary
Long-term
Uptake
NO" -N
t/ha
cm
(kg/ha)
(kg/ha)
(kg/ha)
(kg/ha)
(kg/ha)
(kg/ha)
(kg/ha)
(kg/ha)
(ppm)
23
1.3
784
224
196
168
140
112
0
0
47
2.5
1,568
448
392
420
224
--
112
84
15
93
5.1
3,136
896
784
907
448
112
213
42
140
7.6
4,704
1,344
1,176
1,445
560
112
403
79
187
10.2
6,272
1,792
1,568
1,982
672
--
112
594
117
280
15.2
9,408
2,688
2,352
3,058
896
--
112
974
192
467
25.4
15,680
4,480
3,920
5,208
1,344
112
1,736
341
Assumptions in Table 7:
1. 18.At dewatered sludge; 3AX organic N, 0.9^ ammonia N.
2. Organic nitrogen mineralized 20% in year 1, 31 thereafter.
3. Ammonia volatilization = 50% of available nitrogen.
4. Temporary soil storage is available nitrogen in the sludge/soil layers.
5. Long-term soil storage is clearly present but not known at present and conservatively assumed = 0.
6. First-year uptake estimated at 2/3 of 168 kg/ha/yr rate.
7. Average nitrogen leaching concentration based on 114 cm total precipitation and 64 cm evapotranspiration.
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potential for loss has been verified in our research at Pack Forest (Cole
and Henry 1983). Limiting forest applications to less than 40 dry metric
tons/ha, and thus minimizing the potential for nitrate leaching, could at
the same time limit the growth response or duration of response the
forester might expect from a sludge application. It is clear that more
research is needed to meet the two critical objectives of limiting ni-
trate losses and maximizing growth responses. If it is decided in for-
estry that sites cannot receive sludge more often than perhaps every five
years, in all probability higher applications, resulting in temporary
leaching loss of nitrate, might be recommended in order to obtain the
desired growth response. It would appear from our current experience
that a 40 dry t/ha application will provide a growth response for at
least a five-year period. This rate of application will have only a
minimal potential of affecting nitrate concentrations in the groundwaters
and soil solutions of the application site, and thus will meet current
regulations.
RECOMMENDATIONS AND CONCLUSIONS
Forests of this country have been largely unused for the disposal
and reuse of municipal wastewaters and sludges. Research by the
University of Washington and other institutions suggests that such sites
represent a logical alternative to other options that have more tradi-
tionally been used by municipal sewage treatment agencies. The major
disadvantage is probably the lack of an adequate information base and
understanding such as is currently available in agriculture. Because of
this uncertainty, some municipalities have been reluctant to select
forests for this use. This is ironic in that the application of sludge
and wastewater to forests is a step removed from many public health
concerns.
In order for forests to become a viable alternative for land
application of sludge, the basic differences between forest and agricul-
tural sites will have to be recognized and accepted by regulatory
agencies. These include:
1. The pH of most forest soils is acid, typically below 5.5. This
has the potential of mobilizing heavy metals, especially those
associated with sludge. Although excessive uptake rates,
phytotoxicities, and leaching in forest soils have not been
found, the possibility exists and additional research is
recommended. The regulatory agencies will have to recognize
that forest soils by nature are acidic and cannot be
effectively changed by liming.
2. It is unlikely that a sludge-application program in forestry
will involve annual applications such as carried out in
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COLE, HENRY, SCHIESS AND ZASOSKI
agriculture. In all likelihood repeat applications every five
to ten years is far more probable. Consequently, these
applications will be somewhat higher (probably 80+ metric
tons/ha) than those usually recommended for agricultural
practices. These higher applications can result in an initial
flush of nitrate from the rooting zone.
3. Application rates cannot be limited to slopes of less than 8%,
as is recommended for agriculture. It has been demonstrated
that forest sites with slopes up to 30% can receive 80 dry
tons/ha of dewatered sludge without lateral movement. If
indeed a slope limitation as in agriculture is imposed on
forests, very few forest sites will be available.
Society will also have to recognize that forest areas incorporating
sludge cannot be used in some traditional ways because of the residence
period of pathogens and the uncertainty of the heavy metal issue. For
example, mushroom harvesting might have to be limited because mushrooms
tend to accumulate heavy metals.
Although no food chain problems have been found that originate in a
forest application site, unresolved issues remain regarding browsing by
game animals.
It is our conclusion, after ten years of research applying sludge to
forest sites, that greater use should be made of forests in land
application programs. Not only should it be possible to manage such
programs in a sound and environmentally safe way, but also forests can
dramatically increase in growth rates. Such advantages could especially
benefit very low-site land that currently does not support commercial
forestry.
LITERATURE CITED
Bialkiewicz, F. 1978. Lysimetric and Forest Studies on the Cleaning and
Productive Utilization of Municipal Sewage. Warsaw.
Bledsoe, C. S,, ed. 1981. Municipal Sludge Application to Pacific
Northwest Forest Lands. Inst. For. Resources Contrib. No. 41,
College of Forest Resources, Univ. Washington, Seattle. 155 p.
Bledsoe, C. S. and R. J. Zasoski. 1981. Seedling physiology of eight
tree species grown in sludge-amended soils. Pages 93-100 J_n C. S.
Bledsoe, ed., Municipal Sludge Application to Pacific Northwest
Forest Lands.
Breuer, D. W., D. W. Cole, and P. Schiess. 1979. Nitrogen trans-
formation and leaching associated with wastewater irrigation in
Douglas-fir, poplar, grass, and unvegetated systems. Pages
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Forest Systems
Page 141
19-33 in W. E. Sopper and S. N. Kerr, eds., Utilization of
Municipal Sewage Effluent and Sludge on Forest and Disturbed Land.
Brockway, D. G. and D. H. Urie. 1983. Determining sludge fertilization
rates for forests based on nitrate nitrogen in leachate and
groundwater. (In press). Journal of Environment Quality.
CAST. 1980. Effect of sewage sludge on the cadmium and zinc content of
crops. Council for Agr. Sci. and Technol. Rep. No. 85, Ames, Iowa.
Cole, D. W. 1983. Growth and mortality of sludge-treated forests and
forest plantations. Pages 18-28 in C. L. Henry and D. W. Cole,
eds., Use of Dewatered Sludge as an-Amendment for Forest Growth.
. 1982. Response of forest ecosystems to sludge and wastewater
applications--a case study in western Washington. Pages 274-291 jm
Symposium on Utilization of Municipal Wastewater and Sludge for
Land Reclamation and Biomass Production, September 16-18,
Pittsburgh, Pennsylvania.
Cole, D. W. and C. L. Henry. 1983. Leaching and uptake of nitrogen
applied as dewatered sludge. Pages 57-66 jm C. L. Henry and D. W.
Cole, eds., Use of Dewatered Sludge as an Amendment for Forest
Growth.
Edmonds, R. L. 1979. Microbiological characteristics of dewatered
sludge following application to forest soils and clearcut areas.
Pages 123-136 jjn W. E. Sopper and S. N. Kerr, eds., Utilization of
Municipal Sewage Effluent and Sludge on Forest and Disturbed Land.
Harris, A. R. and D. H. Urie. 1983. Changes in sandy forest soil under
northern hardwoods after 5 years of sewage effluent irrigation.
Soil Science Society of America Journal. Vol. 47. Pages 800-805.
Henry, C. L. 1983. Sludge stability, erosion, and runoff. Pages 76-81
in C. L. Henry and D. W. Cole, eds., Use of Dewatered Sludge as an
Amendment for Forest Growth.
Henry, C. L. and D. W. Cole, eds. 1983. Use of Dewatered Sludge as an
Amendment for Forest Growth. Vol. IV. Inst. For. Resources, Univ.
Washington. 110 p.
Kardos, L. T. and W. E. Sopper. 1973. Renovation of municipal waste-
water through land disposal by spray irrigation. Pages 148-163 in
W. E. Sopper and L. T. Kardos, eds., Recycling Treated Municipal
Wastewater and Sludge through Forest Cropland.
Koterba, M. T., J. W. Hornbeck and R. S. Pierce. 1979. Effects of
sludge applications on soil water solution and vegetation in a
northern hardwood stand. Journal of Environmental Quality. Vol. 8,
No. 1. Pages 72-78.
McKim, H. L., ed. 1978. Land Treatment of Wastewater. U.S. Army Corps
of Engineers, CRREL, Hanover, New Hampshire.
Metro. 1983. Pilchuck Tree Farm: Demonstration Sludge Application
Project Report. Municipality of Metropolitan Seattle. 150 p.
Nichols, C. G. 1980. Engineering aspects of dewatered sludge land ap-
plication to forest soils. M.S. Thesis, University of Washington,
Seattle. 84 p.
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cole:., hfnry, schifss and zasoski
Nutter, W., R. Schultz, and G. Brister. 1978. Land treatment of muni-
cipal wastewater on steep forest slopes in the humid southeast
United States. Pages 266-274 i_n Proceedings State of Knowledge in
Land Treatment of Wastewater. An International Symposium, August
1978, Hanover, New Hampshire.
Reynolds, 0. T. and 0. W. Cole. 1981. Sludge application to forest-
land—a viable alternative. Proceedings 4th Annual Madison
Conference of Applied Research and Practice on Municipal and
Industrial Wastes, September 28-30, 1981, University of Wisconsin
Extension.
RFNRP Staff. 1976. Regional Forest Nutrition Research Project:
Biennial Report, 1974-76. Inst. For. Resources Contrib, No. 25,
College of Forest Resources, Univ. Washington. 67 p.
Riekerk, H. 1978, The behavior cf nutrient elements added to a forest
soil with sewage sludge. Soil Sci. Soc. Am. J. 42:810-816.
Riekerk, H. and R. J, Zasoski. 1979. Effects of dewatered sludge
applications to a Douglas-fir forest soil on the soil, leachate, and
groundwater composition. Pages 35-45 j_n W. E. Sopper and S. N.
Kerr, eds., Utilization of Municipal Sewage Effluent and Sludge on
Forest and Disturbed Land.
Schiess, P. and D. W. Cole. 1981. Renovation of wastewater by forest
stands. Pages 131-147 Jjn C. S. Bledsoe, ed., Municipal Sludge
Application to Pacific Northwest Forest Lands.
Smith, W. H. and J. 0. Evans. 1977. Special opportunities and problems
in using forest soils for organic waste application. Pages 429-454
in Soils for Management of Organic Wastes and Waste Waters,
HA-CSSA-SSSA, Madison, Wisconsin.
Snell, T. D., G. L. Taylor, N. A. Wellons, and W. L. Nutter. 1981.
Clayton County case study on municipal water recycling. National
Water Supply Improvement Journal. January:3-13.
Sommers, L. E. 1980. Usage of sewage sludge in crop production.
Cooperative Extension Service, Purdue University, West Lafayette,
Indiana. (FERTILITY)AY-240.
Sopper, W. E. and L. I. Kardos, eds. 1973. Recycling Treated Municipal
Wastewater and Sludge through Forest and Cropland. Pennsylvania
State University Press, University Park.
Sopper, W. E. and S. N. Kerr, eds. 1979. Utilization of Municipal
Sewage Effluent and Sludge on Forest and Disturbed Land.
Pennsylvania State University Press, University Park. 537 p.
Sopper, W. E. and S. N. Kerr. 1978, Utilization of domestic wastewater
in forest ecosystems--The Pennsylvania State University Living
Filter Project. Pages 333-340 in Land Treatment of Wastewater.
Vol. I. U.S. Army Corps of "Tngineers, CRREL, Hanover, New
Hampshire.
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Forest Systems
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Urie, 0. H. 1979. Nutrient recylcling under forests treated with sewage
effluents and sludge in Michigan. Pages 7-17 Jjn W. E. Sopper and S.
N. Kerr, eds., Utilization of Municipal Sewage Effluent and Sludge
on Forest and Disturbed Land.
Urie, D. H. 1973. Phosphorus and nitrate levels in groundwater as
related to irrigation of Jack pine with sewage effluent. Pages
176-183 in W. E. Sopper and L. T. Kardos, eds., Recycling Treated
MunicipaT~Wastewater and Sludge through Forest and Cropland.
Vogt, K., R. L. Edmonds, and D. J. Vogt. 1981. Nitrate leaching in
soils after sludge application. Pages 59-66 jji C. S. Bledsoe, ed.,
Municipal Sludge Application to Pacific Northwest Forest Lands.
Wilbert, M. and S. G. Archie. 1981. Management of sludge-treated
plantations. Pages 101-103 jjn C. S. Bledsoe, ed., Municipal Sludge
Application to Pacific Northwest Forest Lands.
Zasoski, R. J. 1983. Fate of heavy metals contained in municipal sludge
following forest application. Pages 67-75 j_n C. L. Henry and D. W.
Cole, eds., Use of Dewatered Sludge as an Amendment for Forest
Growth.
1981. Heavy metal mobility in sludge-amended soils. Pages
'57-72 _in^ C. S. Bledsoe, ed., Municipal Sludge Application to Pacific
Northwest Forest Lands.
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PATHOGENS
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Page 147
PATHOGENS
Charles P. Gerba
Departments of Microbiology and
Nutrition and Food Science
University of Arizona
Tucson, AZ 85721
INTRODUCTION AND PURPOSE
As part of the 1973 conference on "Recycling Municipal Sludges and
Effluents on Land" (National Assoc. State Univ., 1973), a series of
workshops were held to identify what was known about municipal waste-
water effluent and sludge application to the land and what research was
needed for the safe and successful land application of such wastes. The
workshop on public health aspects addressed a number of issues and made
a list of major research needs. Sufficient data were felt lackinr in a
number of key areas, including the epidemiology of human populations,
development of capability of monitoring for pathogens, and the disper-
sion and survival of pathogens during land application. This report
will cover advances in understanding the last three topics.
The paucity of information on health problems associated with land
application of domestic wastes may reflect either the absence of a pro-
blem, lack of intensive surveillance, or the insensitivity of present
epidemiological tools to detect recurrent small-scale incidents of dis-
ease. Often the low fecal carriage rates of agents of infectious rlis-
ease and the low background of enteric disease in the United States has
been cited as further evidence that the potential of public health haz-
ard as a result of direct or indirect reuse of wastewater is minimal.
It should be realized, however, that levels of enteric disease in the
U.S. are low primarily because of nood sanitation, personal hygiene, and
a network of sanitary engineering works. As a result of this low expo-
sure to pathogens, the population at larne may have become highly sus-
ceptible to even small numbers of pathogens.
Waterborne outbreaks of disease are no longer on the decline in
this country. A total of 50 waterborne outbreaks occurred during 1980,
increasing the annual average of outbreaks to 39 for the five-year period
from 1976-1980. This represents more than 50% increase over the 1971-
1975 average of 24. The five-year averages have steadily increased from
an annual average of ten during 1951-1955. Before that period, the trend
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was declining (Lippy, 1981). It should be emphasized that waterbome
disease outbreaks, particularly in individual systems, are notoriously
underreported.
Given the difficulty of performing epidemiologic studies and inade-
quacy of waterborne disease reportina, evidence for potential health pro-
blems related with land application of wastewater will often rest on our
ability to assess the fate of human pathogens in the environment.
OCCURRENCE OF PATHOGENS IN RAW AND TREATED SEWAGE EFFLUENTS
A. Bacteria
Pathogenic microorganisms such as bacteria, viruses, protozoa, and
parasitic worms are almost always present in domestic sewage. The num-
ber and types of organisms present in sewage, however, varies from com-
munity to community depending upon urbanization, population density,
sanitary habits, season of the year, and rates of disease in the contri-
buting community (Hoadley and Goyal, 1976).
The most common bacterial pathogens associated with sewage are Sal -
monella, Shigella, Vibrio, and Campylobacter {Table 1). Salmonella oc-
cur frequently in sewage and are responsible for infecting up to 2 mil-
lion people every year. Bacillary dysentery is caused by Shigella spp.
Although Escherichia coli is considered a non-pathogenic organism, cer-
tain enteropathoqenic strains may cause diarrhea, particularly in travel-
ers. Campylobacter jejuni is a recently-recognized cause of acute gas-
troenteritis with diarrhea and is throught to be as prevalent as Salmo-
nella and Shi gel la. The first waterborne disease outbreak of Campylo-
bacterosis occurred in 1978 in Vermont and involved 3000 cases (Vogt et
al., 1982). Waterbome transmission of Yersina enterocolitica resulting
in yersiniosis, an acute gastroenteritis, has also been demonstrated
during the last decade (Eden et al., 1977).
The United States was free from Vibrio cholerae, the causative
aqent of cholera, from 1911 to 1972 (Kowal, 1982).Since 1973, however,
31 cases of cholera have been documented along the Gulf Coast. The
strains from all these cases appear essentially identical, suggesting
that the toxigenic V. cholerae 01 has persisted in that region for at
least eight years. Extra efforts should, therefore, be made to keep
tract of this potential problem.
The concentration of pathogenic bacteria will vary with the inci-
dence of disease within a community. Concentration of Salmonella typhi
in raw wastewater range from 600 to 106/100 ml (Crites and Uiga, 1979).
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Table 1. Bacteria and parasites in sewage and sludge
Group
Pathogen
Disease Caused
Bacteria Salmonella (1700 types) Typhoid, paratyphoid, salmonel-
Shigella (4 spp.)
Enteropathogenic
Escherichia coli
Yersinia enterocolitica
Campylobacter jejuni
Vibrio cholerae
Leptospira
1 os i s
Bacillary dysentery
Gastroenteritis
Gastroenteritis
Gastroenteritis
Cholera
Wei 1's disease
Protozoa Entamoeba histolytica
Giardia Lamb!ia
Balantidium coli
Amebic dysentery, liver abcess,
colonid ulceration
Diarrhea, malabsorption
Mild diarrhea, colonic ulcera-
tion
Helminths Ascaris lumbricoides Ascariasis
(Round worm)
Anc.yclostoma duodenale Anemia
(Hookworm)
Necator americanus Anemia
(Hookworm)
Taenia saginata Taeniasis
(Tapeworm)
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Little is currently known of the concentration of pathogens of emerging
significance such as Yersinia enterocolitica and Campylobacter jejuni.
B. Viruses
More than 110 different virus types may be present in raw sewage
(Table 2). The list of pathoqenic human enteric viruses has continued
to grow during the last decade. Rotaviruses are now recoonized as a
major cause of childhood gastroenteritis, sometimes resulting in dehydra-
tion and death of infants. Rotaviruses also cause diarrhea in adults
and three waterborne outbreaks have now been reported (Zamotin et a 1.,
1981; Sutmoller et al., 1982; Lycke et al., 1978).
The Norwalk viral agent has been demonstrated to be the cause of
numerous water- and food-borne outbreaks of epidemic gastroenteritis
(Kaplan et al., 1982; Gunn et al., 1982). Astroviruses, caliciviruses,
cornavirus-like particles, and new serotypes of Adenoviruses have been
found to be associated with human gastroenteritis. Other viral agents
capable of causing gastroentertis have been recognized but are less well
characterized. Laboratory methods are currently not available to study
many of these agents and they await further characterization.
The concentration of enteric viruses in raw sewage is thought to vary
widely depending on the incidence of disease within the community, time
of year, level of hygiene in the community, etc. Thus, the concentration
of viruses reported in sewage varies widely (Sattar, 1978). Concentra-
tions reported in the literature range from 0-463,500/1 iter. The highest
concentration reported in the U.S. was 42,000/liter (Ridinger et al.,
1982). It is generally felt that concentrations of enteric viruses and
other pathogens are lower in the United States than many developing
nations. Unfortunately, most of the previously published information is
concerned with the detection of enteroviruses and in some cases reovi-
ruses. We know little on the concentration of other viruses in domestic
wastes. Akin and Hoff (1978) have estimated that the average concentra-
tion of enteric viruses in raw sewage in the United States varies between
1,000 to 10,000 virus units/liter.
C. Protozoa and helminths
Little attention has been given to the presence of parasites in
wastewater because of the popular impression that the prevalence of para-
site Infection in the U.S. is low (Larkin et al., 1978). However, be-
cause of the increasing recognition of parasite infections 1n the U.S.,
the return of military personnel from countries with a high parasite
disease prevalence, and the existence of resistant stages of the orga-
nisms, a consideration of parasites is warranted (Kowal, 1982).
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Table 2. Human enteric viruses in sewage
Vi rus
Number
of
Types
Diseases Caused
Enteroviruses:
Poliovirus
Echovirus
Coxsackievi rus
Coxsackievirus
New enteroviruses
(Types 68-71)
Hepatitis Type I
(enterovirus
Norwalk virus
Calicivirus
Astrovirus
Reovirus
Rotavirus
Adenovi rus
72?)
3 Meninqitis, paralysis, fever
31 Meninqitis, diarrhea, rash, fever,
respiratory disease
23 Meningitis, herpanaina, fever,
respirator disease
6 Myocraditis, conqential heart anoma-
lies, pleurodynia, respiratory
disease, fever, rash, meninqitis
4 Meninqitis, encaphalitis, acute hemor-
rhaqic conjunctivities, fever,
respiratory disease
1 Infectious hepatitis
1 Diarrhea, vomiting, fever
1 Gastroenteritis
1 Gastroenteritis
3 Not clearly established
2 Diarrhea, vomiting
40 Respiratory disease, eye infections
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Of the common protozoa which may be found in wastewater only three
speices are of major significance for transmission of disease to humans
through wastewater: Entamoeba histolytica, Giarda lambia, and Ba1 anti-
dium coli (Table 1). All of these organisms are known to cause mild to
severe diarrhea. There has been a steady increase in the number of
waterbome outbreaks of giardiasis in the United States since 1971 (Craun,
1979). Growing recognition of this disease has been responsible for in-
creased surveillance, investigation, and reporting by U.S. public health
authorities. Investigations of disease outbreaks suggest that coliforms
may not be adequate indicators of these orqanisms in drinking waters
which receive only chlorination before distribution (Lippy, 1978). Dis-
infection studies have shown that Giardia cysts are considerably more re-
sistant to chlorine than indicator bacteria or even enteric viruses (Jar-
rol et al., 1980). Levels of Giardia cysts in feces from infected per-
sons may be as high as 1-5 x 106 cysts per gram and the cyst level in
domestic raw sewage has been estimated at about 104 cysts per liter.
Waterborne outbreaks of £. histolytica and EL coli are known to oc-
cur, but there is no recent evidence that waterborne transmission has
occurred. The last reported waterborne outbreak of E. histolytica in
the U.S. was in 1953.
Although helminth infections are still prevalent in the U.S. popula-
tion, the occurrence of disease due to these agents in the U.S. has been
extremely low during the last few decades. The presence and levels in
wastewater of any helminth eggs depend on the levels of disease in the
population. Foster and Engelbrecht (1973) suggested a value of 66 hel-
minth ova per liter of raw wastewater, and Larkin et al. (1978) cited
values of 15-27 Ascaris eggs/liter and 6-2 helminth eggs/liter in pri-
mary effluent.
PATHOGEN REMOVAL DURING SEWAGE AND SLUDGE TREATMENT
A. Sewage treatment
Feachem et al. (1980) reviewed the literature on pathogen removal
by various sewage treatment processes. Table 3 has been adapted from
his results. In interpreting this table, Feachem et al. (1980) warn
that "it is not necessary to dwell on trivial differences, as between
92.3% removal and 97.8% removal, but to look at orders of magnitude".
They further stated that to talk of percent removal is misleading be-
cause a 99® removal of pathogens from raw sewage containing 105 pathogens
per liter, will produce an effluent which still contains 103 pathogens
per liter. This level may still be of great public health concern, de-
pending on how the effluent is going to be used.
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Table 3. Percent removal of pathoaens by various sewaqe treatment
processes*
T reatment
Enteri c
vi ruses
Bacteria
Protozoan
cysts
Helminth
eags
1. Primary
Sedimentation
0-30
50-90
10-50
30-90
2. Trickling t
Filter
90-95
90-95
50-90
50-95
3. Activated +
Sludqe
90-99
90-99
50
50-99
4. Oxidation t
Ditch
90-99
90-99
50
50-99
5. Waste stabi-
1ization
ponds. Three
cells; with
-99.99
>99.99
100
100
> 25 days
retenti on
6. Septic Tanks
50
50-90
0
50-90
* Adapted from Feachem et al. (1981)
+ With sedimentation, sludge digestion, and sludqe drying
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As efficient as it may be, sewage treatment processes cannot be ex-
pected to remove/inactivate all of the pathogens present. Disinfection
of treated wastewater is, therefore, practiced to insure further inacti-
vation of microorganisms. In the United States, chlorination is practi-
cally the only process used for disinfection of wastewater. Unfortunate-
ly, however, there is a great variability in resistance to chlorine among
different microorganisms. It is generally agreed that bacteria are much
more susceptible to chlorine than are viruses and protozoan cysts. Also,
chlorine may be very effective against microorganisms cultivated in the
laboratory under artifical conditions, but it may not be as effective on
naturally occurring strains of bacteria and viruses.
Approximately 90-95% of the enteric bacteria in sewage are reported
to be removed by activated sludge process (Table 3). Coagulation with
alum or lime is considered to be generally efficient for virus removal.
In laboratory studies, 3-4 log reduction of viruses are common following
lime treatment at pH 11. In field studies, however, viruses were iso-
lated from lime sludge and lime-treated effluent (Sattar and Ramia, 1978).
Other tertiary treatments such as ferric chloride-polyelectrolyte floc-
culation, sand or granular filtration, reverse osmosis, and carbon ad-
sorption have been found to significantly reduce the level of pathogens.
Studies indicate that bacteria and viruses are not removed effective-
ly from wastewaters during primary treatment (Gerba, 1981); removal of
viruses during secondary treatment (active sludge) is dependent larqely
upon virus adsorption to solids. Since rotavirus adsorbs poorly to acti-
vated sludge floes it can be speculated that wastewater treatment pro-
cesses that are highly effective in the removal of enteroviruses may not
be as effective in removing rotaviruses and reoviruses. Even within the
enterovirus group, virus adsorption to activated sludge was found to be
both type- and strain-dependent (Gerba et al., 1978). It stands to rea-
son, therefore, that different viruses will have different removal char-
acteristics during activated sludge treatment.
We still know little about the effectiveness of these processes for
the removal of Hepatitis A and Norwalk agent or the bacterial pathogens,
Campylobacter jejuni and Yersinia enterocolitica.
Reported removals of protozoan cysts are usually less than those of
bacteria and viruses (Table 3). Wastewater stabilization ponds have been
reported to have high removals, but this may be due to their concentra-
tion in sludge rather than complete inactivation (Kowal, 1982).
Since helminth eggs are denser than water, conventional primary
treatment (sedimentation) is fairly efficient in their removal (Kowal,
1982). Again, wastewater stabilization ponds accomplish excellent degrees
of helminth egg removal. Stabilization ponds at a land treatment site in
San Angelo, TX, resulted in complete removal of helminths (Kowal, 1982).
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Again, sludge or pond sediments resulting from these processes will have
high densities of viable helminth eggs, and will require proper treat-
ment before utilization.
B. Sludge treatment
Development of new analytical methods for the detection of enteric
viruses in sludges has provided new information on the concentration of
viruses in sludges and the effectiveness of sludge treatment. Reported
concentration of enteric viruses (essentially enteroviruses and reovirus-
es) is shown in Table 4. It is now clear that naturally occurring en-
teric viruses can survive and be detected in aerobic and anaerobically
digested sludges, although removals may be significant during these pro-
cesses (Table 5). Detailed studies of the mechanisms of virus inactiva-
tion during sludge treatment (Ward and Ashley, 1977a, 1978) have shown
ammonia and detergents play a significant role. Drying and loss of
moisture from sludge can result in significant inactivation of viruses
(Ward and Ashley, 1977b). Virus decline is low when the sludge solids
is raised from 5 to 40%. However, there is a 4 to 5 logio decrease in
virus numbers when the final sludge solid percentage is above 90. De-
watering causes the release of viral RNA and inactivation appears to be
due to the dewatering process itself.
In sludge composting, sludge is mixed with other organic materials
such as wood chips or leaves and allowed to decompose for a period rang-
ing from 3-4 weeks. Aerobic conditions are maintained either by forcing
or pulling air into the compost pile or by regularly turninq the pile.
Composting^ being a thermophilic process with temperatures ranging from
60 C to 70 C under ideal conditions generally results in inactivation of
pathogenic microorganisms. Protozoan cysts, helminth eggs, pathogenic
bacteria are effectively inactivated during this process^ Experiments
with model viruses (bacterial virus f2) have revealed that a properly
operated windrow compost system may result in total virus inactivation
in approximately 50 days (Bitton, 1980). Enteric virus monitoring of a
windrow compost system has revealed their presence during the windrow
phase but none after the curing period (Bitton, 1980). Viruses and other
pathogens are inactivated much more rapidly by forced-aeration pile meth-
ods. A monitoring procedure has been developed for the Beltsville Aer-
ated-Pile method based upon achieving 55°C in the lowest temperature por-
tions of the pile for a period of 2.5 days to insure pathogen destruction
(Burge et al., 1981). This procedure along with monitoring for salmon-
el lae has been adopted by the health departments of several states and is
being considered by others as the criteria to be met by compostina opera-
tions for unrestricted release from a pathogen hazard standpoint {Person-
al communication, W.D. Burge, 1983).
Recent studies have also been conducted on the concentration of hel-
minths in domestic sludges in the U.S. (Table 6). Sionificant numbers of
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gerba
Table 4. Reported concentration of enteric viruses in sludnes
Type of Sludge
Concentration
Location
raw
mixed liquor
suspended solids
aerobically digested
lagooned sludge
applied to land
raw
dinested
lagooned
raw
anaerobic-mesophi1ic
raw
anaerobic-mesophi1ic
digesti on
aerobic-thermophilic
digestion
anaerobic high rate
digestion
anaerobi cal ly
digested lagoon
anaerobic digestion
raw
5-145 pfu/ml
5 TCID50/q
1.7 to 5.2 TCin50/g
0.02 to 4.6/q
6.9 to 215 pfu/g
0.2 to 17 pfu/o
1.2 pfu/g
17.9 TCID5q/100 ml
0.85 TCID5q/100 ml
40 to 1,419 pfu/g
6 to 210 pfu/g
10 to 65 pfu/n
1.1 to 17 pfu/g
1.2 pfu/g
5.0-6.7 pfu/g
141-1,060 pfu/100 ml
anaerobic-mesophilic 4-100 pfu/100 ml
aerobic-thermophilic 0-14 pfu/100 ml
anaerobic-mesophi1ic 0.8 pfu/ml
aerobic digestion
anaerobic digestion
14 to 260 TCID5Q/g
2 to 7 TCID5Q/g
Cincinnati
Florida
Hungary
England
Texas
Wisconsin
Florida
Re ference
Brasher and
Ward (1982)
Farrah et al
(1981a)
Turk et al.
(1980)
Palfi (1973)
fioddard et al.
(1981)
Saqik et al
(1980)
Kabrick et al
(1979)
Cliver (1975)
Farrah et al.
(1981b)
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Table 5. Report on removals of naturally occurring enteric viruses
during sludge treatment
Treatment
Reduction (%)
Reference
Anaerobi c-mesophi 1 i c
Thermophi1i c-aerobi c
Anaerobi c-mesophi1i c
Aerobi c-thermophilic
anaerobic-mesophilic
88 - 98.6
>99. 7
28 - 85
77%
952
Kabrick et al. (1979)
Goddard et al. (1981)
Palfi (1973)
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Table 6. Parasite concentration in primary and secondary sludge as
compared to treated sludge
Number of Viable and Non-viable
Eggs/kg Dry Weight of Sample
1 2
Parasite Type of Sludge Average Percent Viable Eggs
As can's spp.
Primary
&
Secondary
9,700
45
(human and pig
roundworm)
T reated
9,600
69
Trichuris
Primary
&
Secondary
800
50
trichiura (human
whipworm)
Treated
2,600
48
Trichuris vulpis
Primary
&
Secondary
600
90
(dog
whipworm)
Treated
700
64
Toxocara spp.
Primary
&
Secondary
1,200
88
(dog and cat
roundworm)
Treated
700
52
Primary and secondary sludqes include sludges from primary clarifica-
tion, Imhoff digestion, activated sludge, contact stabilization, and
extended aeration. Treated sludges include sludges from mesophilic
aerobic and anaerobic diqestion, vacuum filtration, centrifuaation,
lagoons and drying beds.
^ Numbers rounded off to nearest 100.
Modified from Reimers et al. (1981).
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these parasites may survive both aerobic arid anaerobic sludqe treatment.
As in the case of viruses, sludqe drying (i.e., loss of moisture) has a
great influence on the inactivation of parasites in sludges (Reimers et
al., 1981).
Sludge liming has been studied as a method of reducing pathogenic
microorganisms, but has been found to be unreliable in the complete in-
activation of viruses (Sattar and Westwood, 1979) and parasites (Reimers
et al., 1981).
Radiation processing of sludge by exposure to high-energy electrons
produced by an electron accelerator or radiation sources appears to be
highly effective against pathogenic microorganisms and helminths (Epp and
Metz, 1980).
MONITORING CAPABILITIES FOR ASSESSING PATHOGEN FATE AFTER LAND DISPOSAL
A great deal of progress was made in the last decade in the develop-
ment of methodology for detecting viruses in the environment. Reliable
methods are now available for the detection of enteroviruses in water,
sludge, soil, and plant material (Gerba and Goyal, 1982). We now have
the ability to judge the fate of many types of enteric viruses during the
land application of municipal wastewater and sludge. Further research is
needed on the development of methods for the isolation of more fastidious
viruses such as rotaviruses, Norwalk agents, hepatitis, etc. from the en-
vironment. Many of these agents are difficult to grow or cannot grow in
conventionally used tissue culture systems. But, it would appear that
once methods are available to grow these agents in the laboratory only
minor modification of current strategies for isolating of viruses would
be necessary.
Methods for isolation and quantitation of bacterial indicators such
as coliform and fecal coliform bacteria are used for assessing their fate
after land disposal of domestic wastes. There is a need for the develop-
ment of methods for the direct isolation of bacteria pathogens of emer-
ging significance such as Yersinia enterocolitica and Campylobacter
.jejuni.
PATHOGEN FATE DURING LAND APPLICATION
A. Soil and groundwater
The potential for the transmission of disease by contaminated ground
water in the United States is well recognized (Lippy, 1981). A total of
673 waterborne outbreaks affecting 150,268 persons was reported in the
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United States from 1946 to 1980 (Craum, 1979; Lippy, 1981). Of these,
295 (44%) outbreaks involving 65,173 cases were attributed to conta-
mination of groundwater. But thus far, no outbreaks have been attri-
buted to wastewater land application systems.
Currently, 20% of the total water consumed in the U.S. is drawn from
groundwater sources and it is estimated that this usage will increase to
33% in the year 2000 (Freeze and Cherry, 1979). According to Duboise et
al. (1979) over 60 million people in the U.S. are served by public water
supplies using groundwater, and about 54% of rural population and 21 of
the urban population obtain their water from individual wells. Since
groundwater is often used for human consumption without any treatment,
it is imperative to understand the fate of pathogenic microorganisms dur-
ing the land application of wastewater and sludge.
The fate of pathogenic bacteria and viruses in the subsurface will
be determined by their survival and their retention by soil particles.
Both survival and retention are now believed to be largely determined by
climate, nature of the soil, and nature of the microorganism. Climate
will control two important factors in determining viral and bacterial sur-
vival: temperature and rainfall. The survival of microorganisms is
greatly prolonqed at low temperature; below 4 C they can survive for
months or even years (Gerba et al., 1975). At higher temperatures inacti-
vation or die-off is fairly rapid. In the case oif bacteria, and probably
viruses, the die-off rate is approximately doubled with each 10°C rise in
temperature between 5°C and 30 C (Reddy et al., 1981). Above 30 C, tem-
perature is probably the dominant factor determining virus survival time.
Rainfall mobilizes previously retained bacteria and viruses and greatly
promotes their transport in groundwater. Several studies have shown that
the greatest degree of drinking water well contamination occurs after
periods of heavy rainfall (Dewalle et al., 1980; Lewis et al., 1980; Bar-
rel! and Rowland, 1979).
The nature of the soil will also play a major role in determining
survival and retention. Soil properties influence moisture-holding ca-
pacity, pH and organic matter - all of which will control the survival
of bacteria and virus in the soil. Other soil properties such as par-
ticle size, cation exchange capacity, and clay content will influence re-
tention. Resistance of microorganisms to environmental factors will vary
among different species as well as strains. Bacteria are believed to be
removed largely by filtration processes while adsorption is the major
factor controlling virus retention (Gerba et al., 1975).
The following sections are a summary of the recent state of know-
ledge on factors currently believed to influence microbial persistence
and transport in the subsurface.
-------
Table 7. Factors that influence the survival of bacteria and viruses in soil
Factor
Bacteria
Vi ruses
Temperature
pH
Cations
Dessication
and soil
moisture
Sunlight
Antagonism from
soil microflora
Organic matter
Longer survival at low temperature;
lonqer survival in winter than in summer.
Shorter survival time in acid
soils {pH 3-5) than in alka-
line soils.
Greater survival time in moist
soils and during times of high
rainfall. Survival time is
less in sandy soils with lower
waterholding capacity.
May indirectly affect virus survival
by controlling their adsorption to
soils.
May also indirectly influence virus
survival by increasing their adsorp-
tion to soil (viruses appear to sur-
vive better in the sorbed state).
One of the most proven detrimental
factors. Increased virus reduction
in drying soils.
May be detrimental at the soil surface.
Increased survival time in
sterile soil.
Increased survival and possible
rearowth when sufficient amounts
of organic matter are present.
No clear trend with regard to the
effect of soil microflora on viruses.
Unknown
Modified from Gerba and Goyal (1983).
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Table 8. Die-off rate constants (loq-,g/day~^) for enteric micro-
organisms in soil.*
No. of
Microorganisms
Ava.
Max.
Min.
Observations
Escherichia coli
0.92
6.39
0.15
26
Fecal coliforms
1.53
9.10
0.07
46
Fecal streptococci
0.37
3.87
0.05
34
Salmonella sp.
1.33
6.93
0.21
16
Shiaella sp.
0.68
0.62
0.74
3
Enteroviruses
0.10
0.16
0.04
4
* Modified from Reddy et al. (1981).
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Table 9. Reported die-off rate constants (day-^)
for viruses and bacteria in groundwater
Microorganism
Die-off rate
(log10/day_1)
Poliovirus 1
0.046
0.21
0.77
Coxsackievirus B3
0.19
Rotavirus SA-11
0.36
Coliphaae T7
0.15
Coliphaqe f2
1.42
0.39
Escherichia coli
0.32
0.36
0.16
Fecal streptococci
0.23
0.24
0.03
Salmonella typhi murium
0.13
0.22
From Bittori and Gerba (1983)
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Page 164
geres a
1. Bacteria: ftt the turn of the centuryv it was found that the
eating of raw vegetables grown on soil fertilized with raw sewatje result-
ed in outbreaks of typhoid fever. As a result, the survival of enteric
bacteria in soil systems has been extensively studied. There are several
major reviews on the survival of enteric bacteria in soil (Rudolfs et al.
1950; Sepp, 197V, Foster and Engelbrecht, 1973], Most enteric bacterial
pathogens die-cff very rapidly outside of the human gut, whereas indica-
tor bacteria such as Escherichia colj will persist for longer periods of
time. Survival times among~TiTfferent types of bacteria an
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Land disposal of digested sludges have indicated little impact of
bacterial contamination of groundwater, provided that the groundwater
table is not too high and the soil is well-drained (Zenz et at. 1976;
Liu, 1982).
2. Viruses: Virus survival in soil is not only important when
decisions must be made on how long a period of time must be allowed after
last application before permitting access to people and/or animals and
crop harvesting, but the longer viruses survive at the surface the great-
er the opportunity they have for being desorbed and moving down toward
the groundwater. Factors affecting virus survival are summarized in
Table 7. It is believed that most virus inactivation occurs in the top
few centimeters of soil where drying and radiation forces are maximal.
Hurst et al. (1980) concluded that temperature and adsorption to soil
appear to be the most important factors affecting virus survival. The
persistence of viruses and bacteria which.survive surface forces and en-
ter groundwater is not well studied. Limited information is available
on the die-off of enteric bacteria and viruses in groundwater. Table 9
summarizes the current state of knowledge on die-off rates in ground-
water. Enteric bacteria and viruses persist lenger in groundwater than
surface waters (Keswick et al., 1982). Kowal (1982) concluded that ap-
proximately one hundred days appears to be the maximum survival time of
enteric viruses in soil, unless subject to very low temperatures (4°C),
which prolong survival beyond this time.
Only limited information still exists on viruses in sludge soil mix-
tures. Damgaard-Larsen et al. (1977) reported that it took 23 weeks dur-
ing a normal Danish winter to inactivate 106 TCID50/g of coxsackievirus
B3. In wanner and more humid Florida, Farrah et al. (1981a) reported a
two log10 drop in the titer of indigenous viruses in sludge amended soils
within 9 days. In controlled experiments using added virus and columns
with cores of soil they found that 35 days were required for a 4-logio
reduction of poliovirus 1 during the hot and wet summers of northern
Florida. It appears that virus survival in sludge-amended soils is con-
trolled primarily by desiccation and soil temperature (Bitton et at.,
1981; Hurst and Gerba, 1979).
Adsorption is believed to be the major mechanism by which viral re-
moval occurs during the land application of wastewater effluents. Fac-
tors which may influence virus movement into groundwater are listed in
Table 10. Since adsorption is a surface phenomenon, soils with a high
surface area, i.e., those with a high clay content, would be expected to
have the greatest removal capabilities. Although the exact physical-
chemical reasons for virus adsorption are still incompletely understood,
it appears that adsorption is increased by high exchange capacity, sur-
face area, low pH, and increased cation concentration (Gerba and Lance,
1980). As the flow rate, or application rate, increases, virus removal_
declines (Wang et al., 1981). Certain organics, such as bumic and fulvic
acids (Bitton et al., 1976; Bixby and O'Brien, 1979) may compete with
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Table 10. Factors that may influence virus movement to nroundwater
Factor
Comments
Soil type
PH
Cations
Soluble
orqanics
Virus type
Flow rate
Fine-textured soils retain viruses more effec-
tively than light-textured soils. Iron oxides
increase the adsorptive capacity of soils. Muck
soils are generally poor adsorbents.
Generally, adsorption increases when pH decreases.
However, the reported trends are not clear-cut
due to complicating factors.
Adsorption increases in the presence of cations
(cations help reduce replusive forces on both
virus and soil particles). Rainwater may desorb
viruses from soil due to its low conductivity.
Generally compete with viruses for adsorption
sites. No significant competition at concentra-
tions found in wastewater effluents. Humic and
fulvic acid reduce virus adsorption to soils.
Adsorption to soils varies with virus type and
strain. Viruses may have different isoelectric
points.
The hiaher the flow rate, the lower virus adsorp-
tion to soils.
Saturated vs.
unsaturated
flow
Virus movement is
conditions.
less under unsaturated flow
*From Bitton and Gerba (1983)
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Palnogaris
Page 167
viruses for adsorption sites on soil particles, resulting in decreased
virus adsorotion or even elufcion of already adsorbed viruses. Little
differences have been found in virus removal between secondary or pri-
mary effluent (Gerba and Lance, 1978). These results suggest that ad-
sorption of virus and movement through soil is not affected by the high-
er organic content of primary effluent.
The degree of virus adsorption to soils has been found to differ
greatly among virus types, strains, and soils (Goyal and Gerba, 1979).
Differences in adsorption among strains of the same virus type may be
due to differences in configuration of proteins in the outer capsid of
the virus, which affects the net charqe on the virus, This affects the
electrostatic potential between virus and soil, which, in turn affects
the degree of interaction between the two particles. Thus, it appears
that no one virus can be used as the sole model for determining the ad-
sorptive behavior of viruses ta sails and that no single virus can be
used as the model for determining viral adsorptive capacity of all soil
types.
Moore et al. (1982) recently demonstrated that an inverse correla-
tion between virus adsorption ard substrate capacity for caticnic poly-
electrolyte adsorption exists. Thus, adsorption of polyelectrolyte may
be useful ir predicting the fate of viruses -during land aaplication af
sewage effluents and sludges.
Even though there have been no reports cf disease outbreaks associ-
ated with land treatment of sewage wastes> there are a growing number of
studies concerning the detection of viruses in groundwater after waste-
water application to land or direct groundwater recharge. These studies
are summarized in Table 11.
Wellings et al. (1974) first demonstrated viruses in the subsurface
after spray irrigation of secondary sewage effluent. The wastewater was
applied onto an Imolokee sand containing little or no silt or clay. Of
particular interest in this study was that viruses survived chlorinationj
sunlight, spraying, and percolation through 3-6 m of sandy soil; further-
more, after a period of heavy rains, a burst of viruses was detected in
samples that had previously been neqative. These studies demonstrated
that soil type, rainfall, and other factors can affect viral movement
into groundwater, and that viruses are capable of surviving long periods
which, when combined with the ability to move long distances laterally,
could lead to wide dispersal through an aquifer.
Vaughn and Landry (1977) and Vaughn et al, (1978) reported isolations
of viruses from four groundwater recharge sites, from a stormwater re-
charge basin, and from groundwater under a sanitary landfill in Hew York.
These sites have soils of coarse sand, fine gravel, and 1-2% silt. At
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Page 166 GERBA
Table 11. Isolation of viruses beneath land treatment sites.
Site Location
Type of
Maximum distance of
virus migration (mi
Sited
Virus Types
Depth
Horizontal
St. Petersburg, FL
S
Polio 1; coxsackie
B4; echo 7
5
-
Gainesville, FL
s
Coxsackie B4;
Polio 1, 2
3
7
Lubbock, TX
s
Coxsackie B3
30.5
-
Kerrville, TX
s
Ub
1.4
-
Muskegon, MI
s
U
10
-
San Angelo, TX
s
U
27.5
-
East Meadow, NY
R
Echo 12; U
11.4
3
Holbrook, NY
R
Echo 6, 21, 24, 25; U
6.1
45.7
Sayville, NY
R
U
2.4
3
Twelve Pines, NY
R
Polio 2; U
6.4
-
North Masaqequa, NY
R
Echo 11, 23:
Coxsackie A16
9.1
-
Babylon, NY
R
Coxsackie B3; U
22.8
408
Ft. Dvefl s, MA
R
U
28.9
183
Vineland, NJ
R
Polio; coxsackie
B3; echo
16.8
250
Lake George, NY
R
Phaae
45.7
400
Phoenix, AZ
R
Coxsackie B3
18.3
3
Dan Region, Israel
R
Polio 1, 2, 3
31-67
60-270
aR = rapid infiltration; S = slow rate infiltration
bU = unidentified
From Bitton and Gerba (1983)
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Pathogens
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the groundwater recharge sites, viruses were recovered at depths up to
11.4 m and at distances up to 45.7 m from the injection point of secon-
dary or tertiary chlorinated effluent. As much as 22-33% of the 100-
gal. samples at the four sites were positive for viruses, with concen-
trations of 1.3-10.6 PFU/gal. In order to reach the groundwater, vi-
ruses moved through 5.5-9 m of the overlying soil.
Moreover, at the Twelve Pines site, viruses were discovered in
groundwater under basins where effluent seeded with viruses was applied
at rates of 6-100 cm/h. The slower infiltration rates were more effec-
tive in removing the viruses, suggesting that site management is impor-
tant .
Schaub and Sorber (1977) reported on a study of viruses in around-
water under rapid infiltration cells at Ft. Devens, Mass. The soil con-
sisted of silty sand and gravel underlain by bedrock. The groundwater
contained viruses at depths of 29m and lateral distances of 183 m, with
concentrations of about 8.3% of the applied effluent.
At the Vineland, N.J., rapid infiltration site (Koerner and Haws,
1979) primary effluent was applied to Cohansey sand and coarse gravel.
Viruses were found at 16.8 m depths and up to 250 m lateral distances
in 19 or 40 samples. Total coliforms and fecal coliforms were consis-
tently at depths up to 6 m beneath the recharge basins. Total coli-
forms also occasionally occurred at qreater depths and downstrean. In
contrast, no fecal coliforms were found in samples taken below 9.1 m
and coliforms occurred only once in a shallow well 50 m down-qradient.
Thus, viruses penetrated deeper into the ground and moved longer dis-
tances than did the coliforms.
Viruses in groundwater at other recharge sites have been studied with
varying success. At the Flushing Meadows site near Phoenix, AZ (Gilbert
et al., 1976) it was found that a fine loainy sand over coarse sand and
gravel effectively removed viruses. Laboratory studies confirmed that
this soil was an excellent adsorber. No viruses were detected in any of
the samples of renovated water, even though levels of 158-475 PFU/mL
were detected in the effluent applied. However, collform organism were
detected in the renovated water, suaaesting that the removal mechanisms
must have been different for viruses and bacteria, and that viruses may
have been present but below the detection limit. Since this site is no
longer in existence, these findings cannot be confirmed. However, since
then, virus has been detected in a sample from an 18.3 m-deep well at a
nearby land application site. The isolate was identified as coxsackie-
virus B3.
At two land treatment sites where sewage is used to irrigate cropland,
both positive and negative virus isolations have been made (Goyal et al.,
1982; Koerner and Haws, 1979). At the Lubbock, TX, site, coxsackievirus
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B3 was isolated from a depth of 30.5 m; at Roswell, NM, no virus isolates
were detected in samples taken from 3-30 m depths. In the latter case,
irrigation is seasonal and intermittent, whereas application at the Lub-
bock site is continuous.
At an operational land application site in Kerrville, TX (Moore et
al., 1981) no viruses were detected in the monitoring wells at depths of
10.7-19.8 m even though viruses could be detected in 1.4 m-deep lysimet-
eters.
In one often-cited report (England et al., 1965) on the Santee pro-
ject, no viruses were detected in renovated water. This is not surpris-
ing, since the detection methods available at that time were not quanti-
tative. These negative results must therefore be considered highly ques-
tionable, as should the results obtained at the Whittier Narrows, CA
(McMichael and McKee, 1966) projects, which did not employ techniques
sensitive enough to detect low levels of virus. This reiterates the need
for careful evaluation of methods used in any report before negative con-
clusions are accepted.
In summary, human pathogenic viruses have been isolated from beneath
municipal wastewater land application sites practicing both rapid and
slow rate application and this should be taken into consideration when
locating such sites.
Studies with sludge amended soil indicate that viruses are not easily
eluted even after rainfall events, and pose little threat to groundwater
contamination (Damgaard-Larsen et al., 1977; Farrah et al., 1981). The
effectiveness of virus retention on soils durinq sludge application is
probably due to the capacity of the sludge solids to bind viruses in the
top of the soil profile (Bitton et al., 1978). Although Bitton et al.
(1978) pointed out that liquid sludges may contain unbound virus which
could penetrate further into the soil during application.
3. Parasites: Protozoan cysts are highly sensitive to drying and
are expected to only survive a few days in most soils. Entamoeba histol-
ytica has been reported to survive 18-24 hours in dry soil and 42-72
hours in moist soil (Kowal, 1982). Helminth eggs and larve, in contrast
to protozoan cysts, live for long periods of time when applied to land,
probably because soil is the transmission medium for which they have
evolved toward water transmission (Kowal, 1982). Thus, under favorable
conditions of moisture, temperature, and sunlight, Ascaris, Tjnchuris,
and Toxocara can remain viable and infective for several years (Little,
1980]T Hookworms can survive up to 6 months (Feachem et al,, 1980), and
Taenia a few days to seven months (Babayeva, 1966); other helminths sur-
vive for shorter periods.
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Pathogens
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Because of their large size protozoan and helminth post no threat as
groundwater contaminants.
B. Crops
1. Bacteria: The survival of bacteria on plants, particularly crops,
is especially important since these may be eaten raw by animals or humans,
may contaminate hands of workers touching them, or may contaminate equip-
ment contacting them. Such ingestion or contact would probably not re-
sult in an infective dose of a bacterial pathogen, but if contaminated
crops are brought into the kitchen in an unprocessed state they could re-
sult in the regrowth of pathogenic bacteria, e.g., Salmonella, in a food
material affording suitable moisture, nutrients, and temperature (Bryan,
1977).
Pathogens do not penetrate into vegetables or fruits unless their
skin is broken (Bryan, 1977; Rudolfs et al., 1950), and many of the same
factors affect bacterial survival on plants as those in soil particular-
ly sunlight and desiccation. The survival times of bacteria on subsur-
face crops, e.g., potatoes and beets, would be similar to those in soil.
The survival of enteric bacteria on crops Kas been extensively stud-
ied and reviewed (Bryan, 1977; Kowal, 1982). Reported survival times
for common bacterial pathogens range from less than one day to six weeks
(Kowal, 1982).
On the basis of field experiments with lettuce and radish irrigated
with municipal wastewater, Larkin et al. (1978) concluded that leafy
vegetables cannot be considered safe from Salmonella contamination until
the soil can be shown to be free of Salmonella. TRiy also noted that,
because of regrowth in soil and on leaf crops, total conforms and fecal
streptococci bore no relationship to Salmonella levels, and are unac-
ceptable indicators of fecal contamination*, they recommended using fecal
coliforms or Salmonella itself.
Thus, the consumption of subsurface and low-growing food crops, e.g.,
leafy vegetables and strawberries, harvested from an irrigated site with-
in about six months of last application, is likely to increase the risk
of disease transmission, because of contamination with soil and bacterial
survival in cracks, leaf folds, leaf axils, etc. Possible approaches to
avoid this problem are (1) use of the subsurface or covered drip irriga-
tion method for aerial crops, (2) growth of crops the harvested portion
of which does not contact the soil, e.g., grains and orchard crops, or
(3) growth of crops used for animal feed only, e.g., corn (maize), soy-
beans, or alfalfa. The last alternative 1s probably the most common and
most economic. In the situation where the harvested portion does not
contact the soil nor 1s within splash distance, stopping wastewater
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application a month prior to harvest would be prudent.
2. Viruses: On the surface of aerial crops virus survival would be
expected to be shorter than in soil because of the exposure to delete-
rious environmental effects, especially sunlight, high temperature, dry-
ing, and washing off by rainfall (Kowal, 1982). Reported survival time
of viruses on crops is similar to those of bacteria, and likewise ap-
pears to support a one-month waiting period after last wastewater appli-
cation before harvest.
The absorption of enteric viruses by plants is a theoretical possi-
bility. Murphy and Syverton (1958) found enterovirus to be adsorbed by
tomato plant roots grown in hydroponic culture under some conditions,
and in some cases to be translocated to the aerial parts. However, the
rapid adsorption of virus by soil particles under natural conditions may
make them unavailable for plant absorption, thereby indicating that
plants or plant fruits would be unlikely reservoirs or carriers of viral
pathogens. Using coliphage f2 Ward and Mahler (1982) found little virus
was translocated to distal plants of corn and bean plants unless the
roots were cut. The intact surfaces of vegetables are probably impene-
trable for viruses.
Because of the possible contamination of subsurface and low-growing
crops with soil, in which viruses have a longer survival time, about one
hundred days would probably be a safe waiting period.
3. Parasites: Because of their exposure to the air, desiccation,
and sunlight, protozoan cysts and helminth eggs deposited on plant sur-
faces would also be expected to die off rapidly. The fact that cysts
can survive long enough to get into the human food supply under poor man-
agement conditions is confirmed by the recent isolation of high levels
of Entamoeba histolytica, E. coli, Endolimas nana, and Giardia lamb!ia
on the wastewater-irrigated fruits and vegetables in Mexico City's market-
places (Kowal, 1982). Rudolfs et al. (1950) found contaminated tomatoes
and lettuce to be free from viable Entamoeba cysts within 3 days. They
concluded that field-grown crops "...consumed raw and subject to conta-
mination with cysts of E_. histolytica are considered safe in the temper-
ate zone one week after contamination has stopped and after two weeks
in wetter tropical regions".
Because of desiccation and exposure to sunlight, helminth eggs de-
posited on plant surfaces die off more rapidly. Thus, Rudolfs et al.
(1950) found Ascaris eggs, the longest-lived helminth egg, sprayed on
tomatoes and lettuce, to be completely degenerated after 27-35 days.
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Pathogens
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C. Aerosols
"I. Bacteria: Microbial aerosols are readily created when waste-
water is applied to the land by spray equipment. Their content of micro-
organisms depends upon the concentration in the waste water and the aero-
sol ization efficiency of the spray process, a function of nozzle size,
pressure, anqle of spray trajectory, angle of spray entry to the wind, im-
pact devices, etc. (Schaub et al., 1978). Aerosols represent a means by
which pathogens contaminate fomites such as clothing and equipment but
also a means of direct human infection through the respiratior route,
i.e., by inhalation.
When aerosols are generated, bacteria are subject to an immediate
"aerosol shock" or "impact factor" which may reduce their level by one
log within seconds (Schaub et al,, 1978). Their survival is subsequently
determined primarily by relative humidity and solar radiation (Teltsch
and Katzenelson, 1978). At low relative humidities rapid desiccation oc-
curs, resulting in rapid die-off (Sorber and Guter, 1975), although con-
centration of protective materials within the droplet may occur (Schaub
et al., 1978). Teltsch and Katzenelson (1978) have found bacterial sur-
vival at night up to ten times that during day time in Israel. High tem-
perature is another factor decreasing bacterial survival. While biolo-
gical aerosol decay is occurring, the rate of physical aersol decay, or
deposition, simultaneously affects the distance of dissemination of the
bacteria. This is influenced by wind speed, air turbulence, and local
topography, e.g., a windbreak of trees. Factors which effect survival
and dispersion of microorganisms in wastewater aerosols are shown in
Figure 1.
Because of low density of aerosolized bacteria normally emanating
from land treatment sites, high-volume samplers, e.g., 1 mVmin electro-
static precipitators, are often necessary for aersol analysis. Likewise,
because of the normally low denisty of pathogenic bacteria compared with
nonpathogens, most measurements of aerosol bacteria have utilized tradi-
tional indicator bacteria, e.g., standard plate count, total coliforms,
and fecal coliforms (Kowal, 1982). The measurements of Johnson et al.
(1978) have shown little correlation between densities of these indicator
bacteria and densities of the pathogens which they are intended to indi-
cate. This results in "extreme underestimation of pathogen levels,"
since the pathogens which they studied, I.e., Pseudomonas, Streptococcus,
and Clostridium perfrinqens, survived the aerosolization process much
better than did the Indicator bacteria. They suggest that fecal strep-
tococci might be a more appropriate indicator organism because of its
similar hardiness upon impact and viability to those of pathogens. Sim-
ilarly, Teltsch et al. (1980) measured densities of conforms, Salmon-
ella, and the enteroviruses in aerosols and wastewater at an Israeli land
treatment site, and from "...the ratios of salmonellae to conforms and
enteroviruses to coliforms in the air, as compared to these ratios in the
wastewater, it was concluded that the suitability of coliforms as an in-
dication of airborne contamination caused by spray irrlaatlon 1s question
able."
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Page 174
gerba
Figure 1. Factors which effect survival and dispersion of microorga-
nisms in wastewater aerosols.
RELATIVE
( sun y
usy.
WIND SPEED
FACTORS
WHICH EFFECT
SURVIVAL AND
DISPERSION OF
MICROORGANISMS
IN WASTEWATER
AEROSOLS
;TYPE OF$5£g%>
SPRAY EQUIPMENT
?l TEMPERATURE
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Pathogens
Page 175
The results of field studies suaqest that the aerosol bacteria are
usually detected at a maximum distance that is less than 400 m from the
spray site. Bausum et al. (1978) found that at 30 m 75% of the aerosoli-
zed particles fell in the respirable range.
The human exposure to aerosol bacteria at land treatment sites can
be roughly estimated from the data at Kibbutz Tzora, Israel where raw
wastewater is sprayed (Kowal, 1982). An adult male, engaged in lioht
work breathing at a rate of 1.2 m3/hr and exposed to 34 colifQrms/m3 (the
Kibbutz Tzora average) at 100 m downwind from a sprinkler, would inhale
approximately 41 coliforms per hour. Since the ratio of aerosolized Sal-
monella to coliforms is 1:105{Grunnet and Tramsen, 1974) the rate of in-
halation of Salmonella would be about 105-fold less, an extremely low
rate of bacterial exposure. More recent data from Kibbutz Tzora allows
a more accurate estimate of human exposure (Teltsch et al., 1980). Dur-
ing a period of time in 1977-78, when the wastewater total coliforms
were 2.4 x 106 to 1.4 x 107/100 ml and Salmonella was 0-60/100 ml, the
density of aerosol Salmonella at 40 m, the maximum distance found, was
0-0.054/m3, with a mean of 0.014/m3. This would result in an inhalation
rate of 0.017/hr at 40 m, higher than the previous estimate, but still an
extremely low rate of bacterial exposure.
2. Virus: Aerosols have been of concern as a potential route of
transmission of disease caused by enteric viruses because, as with bac-
teria, once they are inhaled they may be carried from the respiratory
tract by cilia into the oropharynx, and then swallowed into the gastro-
intestinal tract (Kowal, 1982).
The initial aerosol shock during the process of aerosolization may
result in a half log loss of virus level (Sorber, 1976). The subsequent
die-off, estimated to be about one log every 40 seconds (Sorber, 1976) is
determined primarily by solar radiation, temperature, and relative humi-
dity. Sorber (1976) has estimated that, under the least desirable meteo-
rological conditions studied, less than 200 meters would be required to
provide a reduction of three logs in aerosolized virus concentrations.
Very few measurements of aerosol viruses from the spraying of waste-
water have been reported in the literature. The spraying in Israel of 3-5
day detention time oxidation pond effluent, having a coliform density of
about 106/l00 ml, resulted in the detection of poliovirus, coxsackievirus,
and echovirus up to 100 m downwind (Shuval, 1978). To obtain quantitative
measurements of aerosol virus concentrations in air may require heroic
efforts. Johnson et al (1977) operated ten high-volume samplers (1 m3/
min electrostatic precipitators) for three-hour sample periods, at 50 m
downwind from the source, to measure the aerosol enteroviruses produced
by the spraying of unchlorinated aerated-effluent in Pleasanton, Cali-
fornia. Likewise, Teltsch et al. (1980) used a large-volume scrubber-
cyclone sampler to extract 27 + 11 m3 of air downwind from an irrigation
line spraying raw wastewater at Kabbutz Tzora, Israel.
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GERBA
The results obtained from these two studies are highly variable, but
it appears reasonable to make use of the Pleasanton aerosol virus density,
i.e., 0.014/m3, to make human exposure estimates, since (1) the Pleasan-
ton wastewater virus level is similar to that in U.S. wastewaters in gen-
eral, (2) the high Israeli wastewater virus levels are not typical of
those found in the U.S., and, in any case, a wastewater stabilization
pond would decrease these levels, and (3) the 0.14/m3 value found at 50 m
in Israel is based on only one sample, and does not appear to be repre-
sentative of the other values (Kowal, 1982).
From these data it can be calculated that an adult male, enqaqed in
light work, breathing at a rate of 1.2 m3/hour and exposed to 0.014 PFU/
m3 at 50 m downwind from a sprayer, would inhale approximately 0.13 PFU
of enterovirus during an 8-hour work day. This is probably an insigni-
ficant level of exposure. However, since the recovery of enteric viruses
from environmental samples is not perfectly efficient, isolation of vi-
ruses cannot yet be isolated on cell cultures, the actual exposure to en-
teric viruses may be as much as ten to a hundred times the reported level
(Teltsch et al.,1980). Thus it might be prudent to recommend a 100 m or
200 m minimum exposure distance of the general public to a land treatment
spray source (Kowal, 1982).
3. Parasites: Because of the large size of protozoan cysts and
helminth eggs compared with bacteria and viruses, it is extremely unlike-
ly that they will find their way into aerosols.
CONCLUSIONS
Kowal (1982) recently reviewed in detail microbial aspects of the
land treatment of wastewater. His conclusions and recommendations are
worth repeating here.
He concluded that "although untreated wastewater should never be
used for irrigation, the level of preapplication treatment required for
the protection of public health may be as little as properly-designed
sedimentation at land treatment sites with limited public access, where
crops are protected by appropriate hydrolgical studies and selection of
application rate Because of potential contamination of crops and in-
fection of animals, slow-rate irrigation and overland-flow systems should
have complete removal of helminth eggs."
"In situations with greater public access (e.g., water disposal on
golf courses), shorter waiting periods before grazing or harvest of crops
...or threat of groundwater contamination (e.g., shallow water table),
more extensive preapplication treatment may be required. This treatment
may consist of wastewater stabilization ponds, conventional treatment
unit processes, or even disinfection. The exact degree of pretreatment
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Pathogens
Page 177
required for these situation is site-specific, and recommendations should
be determined separately for each system."
Because of potential exposure to aerosolized viruses and bacteria
at land treatment sites where spray irrigation is practiced, it would be
prudent to limit public access to 100-200 m from the spray source. Ko-
wal recommended "suppression of aerosol formation by the use of downward
directed, low-pressure nozzles, ridqe-and-furrow irrigation, or drip ir-
rigation is recommended where these application techniques are feasible
....Aerial crops with little chance for contact with soil should not be
harvested for human consumption for at least one month after the last
wastewater application; subsurface and low-growing crops for human con-
sumption should not be grown at a land treatment site for at least six
months after last application. These waiting periods need not apply to
the growth of crops for animal feed, however."
Kowal (1982) concluded that "properly designed slow-rate land treat-
ment systems pose little threat of bacterial and viral contamination of
groundwater." Recent findings (Table 11) of viruses at considerable
depths indicate that further studies are needed before this conclusion
can be validated.
The threat of bacterial and viral contamination at rapid-infiltra-
tion sites does exist, especially if high groundwater tables are present,
and appropriate preapplication treatment or management techniques should
be instituted, e.g., intermittent application of wasterwater," but little
threat to groundwater contamination by microorganisms appears to exist
from sludge disposal.
RECOMMENDED RESEARCH
1. Development of models based upon virus and site characteristics
for predicting survival and transport of viruses in the soil that will
take into account as much phenomena as is presently known including long-
range movement as evidenced by the findings of viruses at considerable
depths and distances from wastewater land-application sites.
2. Studies of virus survival and movement in the soil designed to
test the validity of the above models.
3. Development of improved virus detection methodology since only
one-tenth to one-hundredth of the viruses in wastewater can at present
be detected.
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GERBA
4. Studies of the survival of viruses and protozoan cysts in stor-
age- and waste-stabilization ponds.
REFERENCES
Akin, W.D. and J.C. Hoff (1978) Human viruses in the aquatic environment:
a status report with emphasis on the EPA Research Proaram. Report
to Congress, EPA-570/9-78-006. USEPA, Cincinnati, Ohio.
Babayera, R.I. (1966) Survival of beef tapeworm oncospheres on the sur-
face of the soil in Samarkand. Med. Parazitiol. Parazit. Bolezen.
35:557-560.
Barrell, R.A.E. and M.G.M. Rowland (1979) The relationship between rain-
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QUESTIONS AND COMMENTS FROM THE FLOOR:
Gerald Berg, University of Cincinnati: Viruses are now being reco-
vered from deep wells under land application sites. Would you comment on
the efficiency of virus recovery techniques that have accomplished these
recoveries and upon the effectiveness of these techniques in recovering
hepatitis A virus, rotaviruses and Norwalk-type viruses from wastewater
effluents, groundwater, sludges and soils?
Charles P. Gerba: I think that's a good point, Jerry. One of the
things to remember when you show these data, the methods we have for
assessing viruses in water and various environmental samples are probably
no more than 30 to 50% efficient based largely on data obtained for the
enteroviruses. Methods are not currently available for the detection of
Norwalk agent and hepatitis A in water. These agents are a major cause
of waterborne viral illness. We also have no idea of how these viruses
behave in the subsurface to contaminate groundwater. We have a lot of
unanswered questions about these viruses.
Lee SommerBj Purdue University: Please address the fate and move-
ment of viruses and other pathogens following land application of munici-
pal sewage sludges.
Charles P. Gerba: I'm sorry I moved so fast I neglected to mention
that topic in my presentation. We covered that area in detail in the
manuscript. It would appear, based on the current evidence, the impact
on groundwater would be marginal based on the limited number of studies
that have been done. Viruses, at least, appear to be very effectively
immobilized on sludge solids. Bacteria and parasites being larger also
have little impact on the groundwater. Both laboratory studies and field
studies indicate that penetration of microorganisms in marginal land
application sites. In terms of survival time, at least on the data I've
seen, indicate that it depends a lot on where you are disposing the
sludge. Temperature and climate may play a rather significant role — at
least In the survival of the organism at the soil surface. Sufficient
waiting would be necessary to ensure inactivation of pathogen microorga-
nisms. Certainly, I wouldn't recommend disposing raw sludge on crops.
Merilyn B. Reeves, League of Women Voters: Yesterday I asked Mr.
Pound how much pretreatment is necessary for land treatment, particularly
in regard to the need for nutrient removal. In the paper he presented it
was noted "In general, the removal eficiency of overland, flow systems for
pathogenic organieme ie comparable to that of conventional secondary
treatment systems". However, on page 20 of the paper you just presented
CNorman] Kowal ie quoted as stating "although untreated wastewater should
never be used for irrigation, the level of preapplication treatment
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required for the protection of public health may be as little as properly
designed sedimentation".... "In situations with greater public access
...or threat of groundwater contamination... more extensive preapplica-
tion treatment may be required".
Since the level of pretreatment affects the cost and thus the accep-
tability of a land treatment facility, how much pretreatment do you
recommend for control of virus, pathogens, and other micoorganisms? Do
you believe land treatment should be considered as 'advanced' treatment,
an add-on for conventional treatment processes?
Charles P. Gerba: 1 think it is a very site specific problem. T
think I would have to agree with Kowal that the amount of treatment would
depend upon the actual intended reuse. It seems to me that you should
take advantage-- I think one of the problems in terms of pathogens-
people really (when they begin an evaluation of the problems of patho-
gens) they look at land treatment as a disposal method rather than a
treatment method. Based on studies that I have reviewed, I think in some
situations all that 1s needed 1s primary sedimentation before land dispo-
sal because you can get very high removal of the viruses from primary
wastewater during land disposal of wastewaster. I think any time that a
site is designed, we should try to take advantage of the site charac-
teristics and further reduce the pathogen load on the environment.
Removal during the infiltration of wastewater, at least in terms of viru-
ses, can be very effective and more effective than chlorine under the
proper conditions. 1 believe it is very site specific. We need to
establish on a more formal basis a method for assessing the extent of
pathogen removal at each site under consideration. In many cases we may
find that only primary treatment is needed. I don't think we should
chlorinate unless we really have to. We should take advantage of the
removal that we can achieve with land application. Now, 1f you are going
to use sewage for crop irrigating, the pretreatment requirements become
much greater because there is a greater chance of potential health risks.
So, there, we have to make an adjustment again based on site specific
characteristics. Specific to overland flow, at least in my literature
review, I couldn't find any data—the amount of data 1s so limited on
removal of pathogenic microorganisms—that I don't think an assessment
can be made at the current time of the efficiency of pathogen removal by
overland flow—at least from the published literature. I hope I answered
all your questions.
Cecil Lue-Hing, Research and Development, Metro Sanitary District of
Greater Chicago: Relative to the degree of treatment necessary or
desirable for land application of sewage sludget I would like to share my
knowledged of the Paris, France sewage farm with the lady from the League
of Women Voters. First the lady has asked the bottom-line question. How
much treatment ie necessary? Ie this option getting too expensive? The
Paris sewage treatment facility ie perhaps the second largest facility of
its king in the world - second only to Chicago's West-Southwest facility.
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GERBA
Since about 189?, the sewage from the Paris facility has been used to
fertilise and irrigate Vegetables such as cabbage, leek, celery, and
beans for sale in Paris. The only treatment given the sewage is primary
treatment (settling/sedimentation). The procedure used on the land is
flood irrigation.
Since 1974, the Paris authorities discovered that the nitrogen con-
tent of the sewage Was too low, so they added approximately 203% anaero-
bically digested sludge to increase the nitrogen content.
With regard to public health, I am not aware of any adverse dif-
ference in the health of the people of Paris (attributable to their con-
sumption of sewage-grown vegetables) compared to the health of the people
of Chicago. More recently, Dr. Coin of The Ministry of Health of Paris
has stated that after many years of search he has been unable to detect
any microorganisms on the sewage-grown vegetables attributable to sewage
irrigation.
One final comment (in my role ae researcher and contributor to
government policy) regarding research needs. In this decade, in this
century, we can always develop an impressive list of research needs;
similarly, fifty decades from now and in the next century. However, if
as researchers you cause the desire for additional information to incapa-
citate the making of public policy, along with land treatment, you too
will price yourselves out of the market.
Charles P, Gerba: I find additional comments like yours not
generally useful to me in making an assessment. Your comments are based
on personal observations and not controlled scientific studies, which 1s
necessary for an adequate assessment. I think we can list a long series
of personal experiences but we need to back those up by scientific evi-
dence. We have to be shown 1n carefully controlled studies that there
really are no differences. Such studies are very costly and will rarely
provide an absolute measure of risk. What we need to do 1s establish a
reasonable basis for making these assessments which can be modified in
the future. That's a challenge. There 1s always going to be a need for
more research. What we need to do as researchers 1s to provide the basis
on which we can make rational decisions at a reasonable cost.
Betty H. Olson, University of California, Irvine: Can the relative
sorptive capacity of soil be overwhelmed with continuous application of
wastewater or sludge on land, and therefore, allow more penetration?
Charles P. Gerba: Dr. [Clarence] Lance and I conducted studies to
determine if the ability of soils during continuous flooding with sewage
would be overwhelmed and virus penetration increased (Appl. Environ.
Microbiol. 32:520-526, 1976). In these experiments the capacity of the
soil to adsorb virus did not change. We though that this occurred
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because of inactivation of adsorbed virus allowing for the continual
replenishment of adsorption on the soil.
Betty H. Olson: Cannot chlorination just be applied to groundwater
and eliminate viruses?
Charles P. Gerba: The proper concentrations of chlorine can very
effectively inactivate any viruses present in groundwater. Although, it
should be recognized that viruses are more resistant to chlorination than
enteric bacterial pathogens.
Betty Olson: Bacterial detection techniques have recently improved.
Can one be sure that bacteria are not present or that they are just not
being detected?
Charles P. Gerba: It is possible that not all the enteric bacteria
present in groundwater are not detected. Being stressed, they may not be
detected on selective media commonly used for their isolation.
Betty Olson: Certainly volume and dilution can affect numbers of
bacteria detectable by traditional testing methods. How are volumes
tested for both viruses and bacteria in groundwater movement? What is the
rationale for determining volumes for bacterial sampling?
Charles P. Gerba: I do not know the rationale for determining volu-
mes for bacterial sampling, which are usually reported as numbers per 100
ml volume. For viruses volume sized ranging from 10-1000 liters have
been suggested. The large volume used for virus detection 1s based on
their low infective dose.
Harvey Luce, University of Connecticut: Is the movement of viruses
confined to soils with large pore systems (channels, chambers, joint pla-
ces, coarse textured soils, etc.) or does movement also occur in soils
with email pore systems?
Charles P. Gerba: I think the greatest movement of all bacteria and
viruses occurs in sandy soils. There have been a number of epidemiologi-
cal studies not associated with land treatment of sewage. The greatest
Incidence of diarrheal disease, for example, always occur during the
periods of heavy rainfall. Thus, movement of microorganisms through the
subsurface 1s greatly influenced by rainfall events. This movement
occurs as a slug or concentrated band of viruses because of the elutlon
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GFRBA
of previously adsorbed virus. We actually know less about the bacteria
in those slug-type movements than we do about virus. 1 think that the
area is an area that needs further investigation.
Virus removal by soil type varies greatly. Most of the studies have
been with sandy soils because it has been seen as being the greater
problem although some agricultural soils have been evaluated. Movement
of viruses is less in agricultural type soils than sandy soils.
Another thing that should be looked at Is the findings of Hark
Sobsey that shows the groundwater pH changes directly affected the move-
ment of viruses in subsurfaces. I am not sure if those are related to
rainfall tests or not. Maybe Mark could answer that question. Generally
the higher the pH, the greater the chance of isolating the virus in sub-
surface is going to be.
Mark Sobsey, University of North Carolina: The comment I would like
to make actually follows on the comments that were just node. Also
related to some of the other comments that have been made already and
that is, it ie probably unreasonable to expect land disposal and land
treatment site for wastewater sludge to either be the recipients of
materials that have already almost completely or completely disinfected
or in some other way made to void a pathogenic microorganism and it's
probably also unreasonable to expect such sites to be totally effective
in removing pathogenic microorganisms. So, we have to bear in mind that
it ie likely that some relatively low level of movement of pathogens nay
occur at a land disposal site. And, therefore, it behooves us to con-
sider the possible beneficial uses of that site and the other reasons for
which it is being developed. We can't think of it strictly in terms of
the impact of pathogenic microorganisms. Clearly what we would like to
do is keep the risk of pathogen context to the public to an acceptable
level and therefore we have to consider whether or not the water under-
lying that site is going to be withdrawn for some beneficial purpose such
as water supply subsequently, and if everybody considers that possibility
as water marginal levels of water treatment that is going to be utilised,
are We going to be growing crops on such sites that are going to be con-
sumed by people and animals and therefore, we have to tailor our desires,
I suppose, for pathogen reduction in these sites to other aspects. Ve
must have a management strategy that considers all of the possible uses
and intentions for such sites. The other thing that kind of concerns me
is that we can demonstrate and have demonstrated lower levels of patho-
gens in groundwaters we can demonstrate the presence of pathogens and
sludges applied to application sites or in the wastewater that ie
applied. But we don't have standards for such pathogens and we generally
rely on coliform bacteria or some other indicators of people pollution to
be the standards for drinking water or for other source of materials that
might be consumed by humans and we have very little information on the
relationships between whether the pathogen is an indicator bacteria or
other indicators nor are we fully aware of what those relationships even
ought to be. This again brings us back to the lack of information on the
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Pathogens
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epidemiology of these viruses and what contribution to the circulation of
the viruses and other pathogens in the population from something like the
land disposal sites we are willing to accept.
B. L. Carlile, Texas A A M University: One factor not discussed in
your position paper is the relationship between loading rates (hydraulic
and treatment efficiencies of land application systems. Slow rate land
treatment systems for agricultural utilization appears to be quite dif-
ferent from high rate disposal systems.
Charles P. Gerba: Laboratory studies with soil columns showed that
hydraulic loading rates are directly related to virus removal efficien-
cies. No comparative fields have been conducted to determine 1f removal
efficiencies of rapid infiltration and slow rate sites are different.
Viruses have been detected beneath both types of land treatment sites.
William Pounds, Pennsylvania Department of Environmental Resources:
Is there a reasonable, reliable test that can be conducted on a sludge to
determine the degree of treatment or pathogen removal, on a day-to-day
basis, before sludge is applied to the land?
Charles P. Gerba: Dr. [Wylle] Burge has suggested the use of f2
bacteriophage as an Indicator of pathogens 1n composted sludge {J. Water
Pollut. Control Fed. 53:1683-1690, 1981).
Ebba Lunda, Royal Veterinary and Agricultural University,
Copenhagen, Denmark: The percentage removals in various treatments ae
presented in Table 3 seems difficult to interpret. The -important
questions is not hens much you. remove in percentage, but how much remains
and if this residual ie a public health hazard. The load influences the
percentage removal and various systems function differently under dif-
ferent climatic and management conditions. Without qualifications such a
table ie misleading and should be deleted. That primary sedimentation
removes 0 percent of viruses cannot be correct when the concentration of
viruses in primary sludges is higher than in raw sewage, 10-100 fold
higher in my experience. Stabilization ponds can be very efficient, but
to give the general impression that they are better than activated sludge
treatment seems misleading.
George J. Jackson, Food and Drug Administration: Many methods for
the recovery of microorganisms from sewage sludge, soil or food are not
highly efficient. Results should be interpreted keeping "false nega-
tives" in mind.
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GERBA
Land application of wastewater and sludge may not only add pathogens
to the soil but, possibly, serve to select pathogenic strains of oppor-
tunistic parasites ("free living" protozoa like Naegleria already present
in the soil.
Flora Mae Veilings, Epidemiology Research Center, State of Florida:
In all of the presentations today, one is led to believe that pathogens
are of no aoneern. This bothers me but I am even more concerned over the
last speaker's statement that landspreading results in complete cleans-
ing. This may be true for some of the constituents in sewage and sludge
but it is not true of viruses. T can assure you that even secondary
effluents applied to soils composed mainly of sand results in viruses
percolating into the groundwater. This has been shown over and over
again. l%is is a real concern for Public Health and it must be ad-
dressed. I can assure you that federal regulations permitting this type
of landspreading of primary or secondary effluents will not he acceptable
to Florida.
Y. A. Demirjian, Muskegon County, Michigan: Who sampled and tested
for viruses at the Muskegon County wastewater facility for viruses?
Charles P. Gerba: Our laboratory conducted the study at Muskegon to
which I have referred, too. This Information will appear in an article
in the Journal of Water Research within the next year.
Scott Clark, University of Cincinnati Medical Center: My comment is
in response to Dr. Y. A. Demirjian's question on the apparent discrepancy
between Dr. Gerba's detection of virus at a depth of 10 m below the sur-
face at the Muskegon land application site and our failure to detect ani-
mal viruses in either air samples downwind of the pretreatment aeration
lagoons or in wastewater at the pump station Just prior to irrigation.
Detecting viruses in air samples is notoriously difficult. The lack of
detectable viruses in the wastewater prior to irrigation was most likely
due to differences in sample preparation methodology but also may been
due to differences in time of sample collection.
Gerald Stern, EPA, Cincinnati: In reference to using percent of log
reduction for pathogen inactivation, I wish to share some experiences
with you. We collected data on the pathogenic bacteria and viruses
reductions for about 3 years on mesophilic and thermophilic anaerobic
digestion from one plant. In trying to evaluate the data on a pathogen
density level, we found a large amount of variations. It wasn't until We
paired the data that consistent relationships of 2 log reduction of indi-
cators could be related to 1 log reduction of salmonella and viruses.
Trying to evaluate data of this type is difficult.
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Pathogens
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Barbara E. Moore, University of Texas: Directed to the previous
question from the floor: How do you explain not detecting virus in irri-
gation water, but finding them in subsurface water?
Viruses may be present in water at low concentrations. As pointed
out by Dr. Gerba, they are retained (adsorbed) within the soil profile.
Such retention is not synonomous with inactivation and a "concentration"
of viruses or bacteria may occur in the soil depending on numerous
environmental factors affecting organism viability. An elution event,
such as heavy rainfall can mobilize previously adsorbed viruses. If, as
an intermittant observer, one happends to be monitoring on such an occa-
sion, a large number of viruses could be recovered from subsurface water.
Another point which deserves consideration is that our ability to
detect viruses in water ie not 100 percent efficient. Viral recovery
from other matrices found in land treatment systems such as sludge and
soil is less efficient, however. One cannot assume that sampling a few
soil samples with negative results indicates a lack of viruses within the
soil profile.
Flora Mae Welling: I want to emphasise the statement made by
Barbara Moore. The adsorption of viruses is not synonmous with virus
inactivation. Viruses may adsorb and desorb over and over again without
the virus losing its infectivity. Thus, even though small numbers of
virions are applied they become concentrated in the upper few inches of
the soil by the adsorption process. When the pH is altered, perhaps by
heavy rainfall, then viruses are desorbed en mass and are forced to move
downward with the receding waters. If the groundwater is near the sur-
facej the viruses would quickly be entrained in the groundwater. If the
groundwater is at a very deep level, repeated adsorption and desorption
cycles may occur before the viruses reach the groundwater. Once
entrained in groundwaters we do not know how far they might travel.
Secondly, I think Bob Kadlac from Michigan did some overland flow studies
and I believe viruses were demonstrated in the lake into which the reno-
vated water drained.
A 8 for viruses in sludge, my laboratory demonstrated some 24 PFU of
virus in a few grams of "dried" sludge from a package treatment plant.
The sludge had been on the drying bed for 14 days under the hot Florida
gun.
And last, at a sludge disposal site no virus was observed over a
seventeen month period but on the 18th month Viruses were demonstrated at
a depth of 28 feet. Investigation of the area showed that a burrow pit
had been dug to the north-northwest of the site which apparently changed
the flow of the groundwater. Months later viruses were demonstrated in
water from the 58 foot deep companion well. This instance ie an example
of the difficulties involved in monitoring groundwater. We still have a
long way to go before we can devise the ideal monitoring system for
groundwater.
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SPECIFIC ORGANIC COMPOUNDS
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LAND TREATMENT OF MUNICIPAL EFFLUENT AND SLUDGE:
SPECIFIC ORGANIC COMPOUNDS
Michael R. Overcash, Professor
Department of Chemical Engineering
North Carolina State University
Raleigh, North Carolina 27650
ABSTRACT
The pathways and rates by which specific organic compounds are
assimilated 1n a municipal sludge or effluent land treatment system
have a reasonable, but not complete, data base. Use of these data 1s
essential to compare the generation of such chemicals to the soil
capacity for treating such organlcs. It appears that the rate of
certain specific organic priority pollutant applications to land 1s
nearly the same with agricultural sludge versus effluent land
applications. The mechanisms which are evaluated to assure
satisfactory assimilation can Include 1) volatilization, 2)
photodecomposltlon, 3) decomposition (chemical and microbial), 4)
adsorption, leaching and runoff, 5) plant response. Review of these
pathways 1s presented as generic mechanisms followed by illustrative
data, since the number of chemicals of concern (over 100) and the
magnitude of treatment mechanisms are very large. Summarizing these
discussions, 1t was concluded that 1) decomposition 1s prevalent for
most chemicals and at rates which appear to Indicate that satisfactory
assimilation 1s occurring; 2) crop uptake occurs at varying levels,
but such data remain Imprecise without some health-related
quantification; 3) for traditionally designed municipal sludge or
slow rate effluent application systems, leaching does not appear
significant as an environmental pathway for organlcs of land
treatment.
INTRODUCTION
The historical perspective regarding the specific organic
constituents 1n municipal effluents or sludges is somewhat varied.
Using the Proceedings of the Joint Conference on Recycling Municipal
Sludges and Effluents on Land (U.S. E.P.A., 1972) as a benchmark of
the municipal land treatment field, one would conclude that there had
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ovrHCASH
been minimal attention on these waste constituents. However^ one must
review the situation in 1972 for an interpretation of this lack of
attention.
In 1972 there was no focused list of organic compounds that had
been proposed to be of environmental concern. Thus only certain
organics were identified as possible concerns, namely the Aroclor
mixtures referred to broadly as polychlorlnated blphenyls (PCB).
These were mentioned 1n the chapters on municipal effluent and sludge
characterization and 1n the chapter on monitoring (Blakeslee, 1972).
Actual quantification of Aroclor mixture concentrations were given for
a number of municipal effluents and sludges 1n Michigan. Citations in
this benchmark Proceedings represented the level of focused attention
on specific organics 1n regard to municipal land application.
A different perspective of the concern and level of understanding
for organic compounds 1s obtained by evaluating the broader field of
the behavior of organic compounds In the terrestrial system (even at
the 1972 period). This broader field encompasses research interests
in pesticides and residues, other agricultural chemicals, soil
sterilization, response of chemical spills, organic fertilizers, and
fundamental Investigations of soil-plant behavior. With this broader
perspective, one concludes that there 1s a very large data base and a
substantial delineation of mechanisms operative for specific organic
compounds 1n soil-plant systems. This information began accumulating
1n early 1900 and the article by Buddin (1914) represents (even at
that early date) a sound understanding of germicidal effects of
organic chemicals on soils (some of which are now considered priority
pollutants). Thus the research into the behavior of toxic and
nontoxic organic compounds when applied to land has been continued as
a significant research area today. This contrasts with the low level
of attention given this area 1n relation to land treatment, circa
1972,
The magnitude and diversity of the organic compounds that have
been evaluated In the context of a terrestrial system was estimated
recently and put 1n catalogue form, called TERRETOX (Qvercash and
Sims, 1981). From an artlcle-by-artlcle search of 240 appropriate
journals for the period 1976-1981, over 4,000 organic compounds were
found (many non-pest1c1des). These citations contained one or more
evaluations of the following classes of terrestrial behavior of
specific organics: volatilization, photolysis, decomposition*
adsorption, plant uptake, phytotoxlclty. Thus there exists a
substantial (and to many, surprisingly large) data base from which to
begin evaluation of specific organic compounds as these might Impact
land application of municipal effluents and sludges.
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Specific Organic Compounds
Page 201
In 1976 the definition of organic compounds of environmental
concern changed from an amorphous collection containing a few highly
visible chemicals to a specific 11st of organlcs - the Consent Decree
Priority Pollutants. Prior to this date, attention on organlcs 1n
municipal wastes was restricted by the lack of knowledge about what
compounds were present or might be of concern. Thus attention or
research priority was limited 1n scope. With the priority pollutant
11st# whether complete or not# a program was undertaken to measure
these specific organlcs In municipal wastes# effluents and sludges
(Feller, 1980). These results are discussed 1n a later section. For
the organic chemical class, the Increased awareness of municipal
effluent and sludge concentrations of organic constituents has
stimulated recognition of the larger body of research Information
pertinent to understanding this facet of land application. Thus the
merging of Information from the terrestrial behavior of organic
compounds to land application of municipal sludge and effluents is
beginning. Given the extent of the former, 1t appears that there will
be significant transferable Information to allow estimation of
behavior, relative assimilation capacities, and critical levels for
specific organlcs. However, specific research on the organic priority
pollutants In the presence of the municipal sludge or effluent will
also be necessary as the basic understanding of the Individual
chemicals is obtained (experimentally or via the literature).
In the Inorganic field, such as heavy metals, 1t 1s possible to
discuss most of the species and pathways 1n the context of a review
article. The organic constituents, even 1f restricted to the priority
pollutants (probably not a suffuclent 11st) represent about 100
compounds as compared to 5-10 metal elements of concern. In addition#
these organic compounds vary widely 1n the pathways that are
significant to describe chemical fate and actually include more
mechanistic routes for assimilation than metal elements. This
magnitude and complexity of organic chemical information can be
presented as a complete description of the terrestrial behavior of a
single group of closely related compounds. Such reviews are lengthy
and examples are available (Overcash et al, 1982; Pal et al, 1980;
Overcash, 1981a; S1ms and Overcash, 1983). Since this area of
municipal waste concern 1s emerging, a broad overview 1s not possible
1n which all Information and details are provided. This posed a
dilemma for a state-of-the-art review of organic compounds, and so an
alternate approach became necessary. This approach 1s to describe# 1n
a generic fashion, the assimilative pathways for organic compounds 1n
terrestrial systems. Illustrations of Information are given. Then
the author provides a general estimate about the significance of
pathways relative to municipal wastes. The reader will thus have to
pursue 1n some detail specific compounds by use of published
literature. This 1s typical of the scattered yet substantial
information on organic chemicals 1n the terrestrial systems.
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Ovf-HCASH
WASTE CHARACTERISTICS
There has only recently been large scale sampling and analysis
for specific organic compounds 1n municipal raw waste, effluents, and
sludges. Concern with trlhalomethanes, with the priority pollutants,
and with public health effects have encouraged such analyses. In
general the Impact (1n terms of mass and type of chemical) of
Industrial discharges has not been separated from the typical domestic
or small town characterization and so domestic characteristics remain
an Important Information need. It remains difficult to predict the
concentrations of specific organlcs in municipal wastes.
Several studies of municipal waste characterization for specific
organlcs (not just priority pollutants) do exist primarily as basic
data with little interpretation. A comprehensive study was made on
the priority pollutants (U.S. E.P.A., 1982) and covered 60 separate
plants (publicly owned treatment works). These data are without much
Interpretation except as percent removal although the basic data were
published for the reader. Majetl (1981) published a review of
literature Information prior to the detailed EPA work and included
non-pr1or1ty pollutant organlcs. Recent Information from Michigan
(Jacobs and Zablk, 1983) further expands the characterization of the
specific organlcs present 1n municipal sludge.
The concentrations of organic compounds in municipal sludges and
effluents are at least as variable as those reported for metals
(Sommers, 1977). From the perspective of municipal effluent or sludge
land treatment this variation argues presently for direct analysis of
each particular waste. The reduced cost (30%-50% of 1980 prices) has
brought priority pollutant analyses within a more affordable range.
Table 1 1s derived from the lengthy characterization by U.S. E.P.A.
1n 1982.
The Issue of PCB concentration 1n municipal wastes remains
undefined. In the characterization by the U.S. E.P.A. (1982), the
most prevalent chlorinated blphenyl mixture was 1242, with an
occurrence frequency 1% for secondary effluent and less than 1% for
primary sludges. PC8-1254 occurred less than \% for both effluent and
primary sludge. This contrasts with the Michigan data of Blakeslee
(1972) 1n which PCB-1242 occurred 3% and PCB-1254 occurred 52% of the
time 1n municipal effluent. Certainly year of sampling and other
factors are Involved. If the U.S. E.P.A. (1982) data describe the
typical national occurrence, It may be that as an organic compound
group, PCB is less Important than a large number of other organic
chemicals of concern.
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Specific Organic Compounds
Page 203
Table 1. Summary of Municipal Secondary Effluent and Primary
Sludge Composition of Organic Priority Pollutants
Chemical Group
Two Compounds with
highest concentrations
(ppb on as 1s basis)
(average of 19 plants)
Range of
concentrations
reported (ppb
on as 1s basis)
SECONDARY EFFLUENT
Halogenated Al1phat1cs
Substituted Aromatlcs
Phthalate Acid Esters
Polynuclear Aromatlcs
Methylene Chloride (48)
Methyl Chloride (12)
Toluene (18)
Pentachlorophenol (2.1)
B1s (2-ethylhexyl)
phthalate (21)
D1 n-butyl
phthalate (3.6)
Phenanthrene (0.68)
Anthracene (0.68)
0.16 - 48
0.21 - 18
0.21 - 21
0.16 - 0.68
PRIMARY SLUDGE
Halogenated Allphatlcs
Substituted Aromatlcs
Vinyl chloride
Chloroethane
Toluene
Phenol
(3,600)
(1,500)
(1,900)
(320)
37 - 3,600
29 - 1,900
Phthalate Acid Esters
280 - 3,900
Polynuclear Aromatlcs
B1s (2-ethylhexyl)
phthalate (3,900)
Butyl benzyl
phthalate (3,900)
Phenanthrene
Anthracene
(410)
(410)
89 - 410
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OVERCASH
In the context of land treatment for municipal effluent and
primary sludge# the Impact of organic priority pollutants are
Illustrated 1n Table 2. For the highest organic compounds 1n each
waste type, the typical mass loadings are similar (1.4 kg/ha/yr for
bis (2 ethyhexyl) phthalate as sludge versus 0.63 kg/ha/yr for
methylene chloride as secondary effluent). These two compounds have
very different behavior pathways In terrestrial systems, illustrating
the difficulty 1n generalized statements. This similarity of organic
compound loading rates# with substantially different concentrations
reflects the complexity of other controlling parameters 1n sludge or
effluent applications to land.
ORGANIC COMPOUND ASSIMILATIVE PATHWAYS MUNICIPAL LAUfi TREATMENT
A specific organic compound undergoes a variety of chemical and
biological processes when applied to a soil or soil-vegetation system.
Although a lot of research has not been conducted to verify
preliminary observations# 1t 1s felt that the presence of the overall
organic and Inorganic fractions of a waste merely attenuates the
various pathways by which an organic species 1s treated 1n the
terrestrial system. Thus at this stage of development 1t remains
important to understand and quantify the assimilative pathways (from
whatever system was used to generate such data) and to project the
probable acceptable rates of land application for each organic
constituent of interest.
Volatll1zat1on
An organic compound Irrigated 1n a wastewater* surface spread
with a sludge# or Injected Into the soil will partition between the
gas and liquid phases to exert a vapor pressure. This vapor may be
rapidly lost as might occur with Irrigation# may be re-adsorbed 1f
present beneath the soil surface# or may exhibit any behavior 1n
between these two extremes. The conditions of soil and application
technique land application as well as the inherent organic compound
volatility are Important factors in quantifying how an organic
compound might be lost through volatilization. It must also be
remembered that volatile losses occur when municipal effluents are
treated and discharged to streams and when sludges are put 1n
landfills as well as when these wastes are managed by land treatment.
Volatilization literature exists for chemicals applied to soil
systems. The following represents a partial summary for the
Information on certain aromatlcs (Overcash and Pal# 1979).
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Specific Organic Compounds Page 205
Table 2. Annual organic chemical loadings* kg of compound/ha/yr
associated with traditional sludge and effluent
application rates.
For Primary Sludge For Secondary Effluent
at 500kg of N/ha/yr at 1 Inch/week
Methylene Chloride
0.016
0.63
B1s (2 Ethylhexyl
phthalate
1.4
0.28
To!uene
0.66
0.24
Phenol
0.11
0.02
Anthracene
0.14
0.009
D1-n-Butyl Phthalate
0.1
0.047
o-D1chlorobenzene
0.0035
0.01
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OVrRCASH
"Many aromatlcs such as benzene, toluene#
cyclohexane, benzoic acid and other substituted
benzene derivatives are volatile. A considerable
amount of these volatile aromatlcs can be lost
from the soil-plant system by evaporation at ambient
temperatures, depending on the wind speed and method
of application 1n the soil. Chlorinated benzene
derivatives are much less volatile and the vapor
pressure of chemicals like hexachlorobenzene
(1.2 x 10 mm Hg at 25°C) 1s so low that these
could be categorized as nonvolatile (Smelt 1976).
When applied 1n high doses, even the nonvolatlles
are lost by volatilization, which 1s encouraged by
high temperature, high wind velocities and surface
application. In a laboratory experiment, about
8055 of added qulntozene was lost from a treated
soil over a 10-month period when air flow was
continuously directed over a 1-cm soil layer. Of
this loss, 62% was accountable by volatilization.
Increasing the organic matter level of a soil tends
to decrease the volatilization of the hydrophobic
nonpolar aromatlcs. Incorporation of wastes Into
soil 1s a management option available to further
reduce volatilization losses."
The level of compound vapor pressure at which volatile losses are
known to be significant (Weber, 1982) 1s usually taken as 5 x 10"^ mm
Hg at 25°C. If one tries to identify vapor pressure characteristics
as a measure of whether volatile losses should be evaluated, this
threshold 1s probably a good first estimate. However, the adsorption
to organic matter and soils could greatly reduce such Initial
concerns. For example, the substantially volatile toluene 1s the
second most prevalent organic priority 1n municipal sludge even after
opportunities for volatile loss during aerobic treatment.
Photodecompos1t1on
A small percentage of a surface applied waste remains available
to exposure for solar radiation. Under these conditions the organic
compound can be degraded resulting 1n treatment of the parent organic
chemical via photolytlc mechanisms. Phenol1cs and polynuclear
aromatlcs are two groups that readily undergo such reactions.
Pathways for such losses have been delineated, but the significance of
such losses 1n municipal land treatment has not been evaluated as a
separate pathway. Usually photodecomposltlon 1s measured as a part of
the total decomposition by biologic and abiotic routes.
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Specific Organic Compounds
Page 207
Decomposition
This 1s a rather broad category of terrestrial pathways which
basically reflect the conversion of specific organic compounds (the
parent species) into metabolItes, chemical Intermediates, biological
material, and small molecules (primarily C02). Microbiological as
well as chemical reactions are usually acting simultaneously and, when
measured as loss of parent compound, are usually undifferentiated.
The decomposition pathway 1s probably the most Important facet of the
organic constituent behavior 1n municipal waste land treatment and
differentiates this research most clearly from that of metals or other
inorganics.
Chemical reactions (abiotic routes) are a part of the overall
measure of compound decomposition. Two typical reactions are
hydrolysis and neutralization of the parent organic species. While
these have been measured, 1t 1s not typical that these be
differentiated from the overall decomposition process, probably since
these chemical reactions leave the bulk of the parent structure still
Intact. Thus the separate quantification of abiotic reaction rates 1s
uncommon.
Microbial processes are the major focus 1n decomposition pathways
for organic compounds. An Initial consideration 1s whether a
particular organic compcound reduces microbial number or affects
enzymatic activity. The following description Illustrates these
effects.
"Phenols and qulnones Inhibit enzyme activity
1n soils, especially urease (Douglas and Bremmer,
1971, and Haselhoff, 1932) and catalase (Dolgova, 1975).
As the phenol concentration 1n polluted soils decreased
from 19.6 to 10.3 ppm, the catalase activity Increased
from 0.5 to 6.6 ml oxygen consumed 1n a 5-minute
exposure (Dolgova, 1975). In a control soil sample
from a nearby botanical garden, the catalase activity
was measured as 18.5 ml in a 5-m1nute exposure.
The Chernozem sand and clay soils from the least
polluted parts of an Industrial area were fumigated
with phegol 1n a hermetically sealed chamber using
160 mg/nr of phenol for 5 days. Phenol content of
the soil was determined after the fumigation* whereas
the catalase activity of the Chernozem* clay, and sand
soils were measured before and after the fumigation.
Catalase activity, expressed as ml 0_ after 5-m1nute
exposure, for Chernozem* clay, and sand were 17.3*
9.5 and 0.3, respectively, prior to fumigation with
phenol and declined to 13.3, 5.5 and 0.0 with fumiga-
tion, at soil levels of 104, 96 and 6.2 mg/kg phenol,
respectively. Dolgova (1975) also observed a decrease
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OVERCASH
1n activities of dehydrogenase, protease and urease
enzymes In the same soils receiving 20-50 kg/ha of
phenols as a result of coke Industry contamination.
The effectiveness of phenols and their derivatives
as germicidal agents 1s well known. The phenol index
has been used historically by pharmacists as a means of
comparison of germicidal quality (Coffman and Woodbrldge,
1974). Despite the sterilizing Influence, there are
certain microorganisms that can withstand relatively
high concentrations of phenol1cs.
Phenols exert an effect on soil microbial numbers
that 1s dependent on the soil concentration or amount
added. At low doses (0.01-0.1% of soil wt), the phenol
serves as an available substrate and there 1s a dramatic
Increase 1n microbial values. This response 1s similar
to that found with the addition to soil of other hydroxy
compounds. As the dose level 1s Increased (0.1-1.0% of
soil wt), an Increasingly strong inhibitory or sterilizing
effect 1s noted. At these levels, a partial sterilization
occurs 1n which there 1s a depression in microbial numbers
but not a complete die-off. After a period of time,
microbes adapt or phenol 1s lost through sorptlve 1nact1-
vatlon or volatilization and a regrowth of population
occurs. The milieu of available dead blomass 1s such
that mineralization and excess nitrogen for microbial
growth occur. The nonvolatile qulnones and hydroqulnones
exert a prolonged microbial effect at certain soil levels,
similar to the response described for phenols."
The microbial die-off effects of organic chemicals are quantified by:
1) The soil concentration of an organic species at which
significant Inhibition occurs, and
2) The length of time to re-establish average levels of
populatlons.
In general, the levels at which organic compounds exert adverse
microbial effects are much greater than one would expect to find with
municipal effluent or sludge land treatment. Exceptions certainly
exist, but these have not been Identified at this time. Even 1f
application led to Inhibitory microbial conditions, the net effect
would only be a lag period after which decomposition or other losses
would still be expected. For the case 1n which such a specific
organic was the controlling waste loading factor, this lag would be a
finite delay 1n successive waste applications rather than a constraint
which leads to no allowable application.
-------
Specific Organic Compounds
Page 209
Decomposition of specific organlcs 1s measured by four common
methods:
1. CO2 evolution
2. 02 consumption
3. dynamics of Intermediates or final products
4. loss of parent compound
Such experiments are not measuring the same phenomena 1n precisely the
same manner and so results do not always agree. The intricacies of
alternative techniques are not discussed here, but the reader must
note that differences exist.
From the course of extensive literature searches concerning the
decomposition of specific organlcs In the terrestrial environment# one
concludes that very few organic compounds can be said to be
non-degradable. This large decomposition potential of soil systems Is
not generally understood# but 1s significant In the national program
to treat organic priority pollutants. Conventional aerobic treatment
reviews 11st numerous organlcs as non-degradable. However# this
categorization most often should be Interpreted as applicable for the
relatively short residence times found 1n conventional processes (6
hours to 30 days). Given very long time periods typical 1n soil
systems, 1t appears that two classes of compounds could be regarded as
nondegradable based on present terrestrial research Informations
1) synthetic polymers manufactured for stability;
2) very Insoluble large molecules# e.g., 5-10
chlorinated blphenyls.
In both of these cases, the soil microorganisms appear to have the
potential to decompose the compounds (deam1nat1on, dehalogenatlon,
etc.) but simply cannot achieve the molecular level conditions
necessary for decomposition.
Decomposition rates (g/ha/d or ppm/day) are dependent on the
concentration of the organic species applied to the soil. This 1s
Illustrated 1n Figure 1 for polynuclear and heterocyclic aromatlcs.
Such relationships are first order and the measurement of the
decomposition rate or half life then becomes the essential data for
design. However, some compounds exhibit zero order decomposition
rates (anthraqulnone dyes, T1lch1n 1983) under the conditions studied.
Thus several reaction models and a large number of decomposition
reaction rate constants can be used to assess loading criteria and
behavior of specific organic compounds. The decomposition rate for
organlcs have been measured for so many classes and specific compounds
that a complete listing or rate quantification 1s difficult. Table 3
-------
Page 210
OVERCASH
10:
1 0
2 .
I 101
o>
\
o>
3
10° =
<
O
g io-H
UJ
a
UJ
h-
¦c
CHL
10"2 *
2 10"3 :
10"« :
*— ACENAPHTHENE
•— ACENAPHTHTLENE
*— ACRIDINE
*— ANTHRACENE
•— BENZ (•) ANTHRACENE
«— BENZO (b) FLUORANTHENE
*— BENZO(k)FLUORANTHENE
*— BENZO (.)PYRENE
2— CHRYSENE ^
y
y
e— D1BENZ(«.J)ACRID1NE
«— DIBENZ (•. h) ANTHRACENE
*— OIBENZOFURAN
B— OIBENZOTHIOPHENE
«— FLUORENE
*— FLUORANTHENE
NAPHTHALENE
— PHENANTHRENE
-•— PYRENE
10
-5
10
i i i iiiiii i i i iiiiii i
-1
i iiiiii
i i i iiiiii i i i iiiiii
10'
10
t
102 103 104 105
INITIAL CONCENTRATION (ug/g-dry wt.)
Figure 1. Deoaiqx>sitian of Folynuclear and Heterocyclic Aromatics
(Sims and Overcash 1983)
-------
Specific Organic Compounds
Page
Table 3. Illustrative Range of Decomposition Half Life
for Organic Compounds
Approximate
Compound Half-Life
Aminoanthroqulnone dyes
100-2,200d
Anthracene
110-180d
Benzo(a)pyrene
60-420d
D1 n-butylphthalate ester
80-180d
Non1on1c surfactants
300-600d
2,4 methyan1l1ne
1.5d
n-N1trosod1ethyl amine
40 d
Phenol
1.3d
Pyrocatechln
12 hrs
Cellulose
35d
Acetic Acid
5-8d
Hydroqulnone
12 hr
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OVE RCASH
contains a range organic decomposition half Hfe values to Illustrate
the assimilative capacity data for specific organlcs. At this time
verification of decomposition rates of specific compounds in the
presence of other municipal waste constituents 1s not widely
aval 1ab)e.
Adsorption, Leaching* and Runoff
Among the physical processes governing behavior of specific
organlcs 1n a municipal effluent or sludge land treatment system the
adsorptlon/leacMng phenomena represent a balanced relationship. The
attraction charge behavior between the organic species and either the
mineral or the organic soil phases results 1n a partitioning Into
adsorbed and solution states. This partitioning may occur Immediately
upon application to the soil or may be delayed until separation from
the waste medium occurs. Competing decomposition reactions can vary
the actual amount of a given organic compound that resides on the
soil/waste phase or in the soil-mater solution.
The adsorption or partitioning processes occur within vary short
distances from the waste application location (molecular or soil pore
slie distances). In contrast, the occurrence of a soil-water matrix
hydraulic potential (for example, from a rain event), migration of
soil-water along appropriate gradients can cause transport of organlcs
1n the soil solution phase. This leaching can be viewed as
theoretically capable of moving a dissolved organic (I.e., all
organlcs) to any location receiving that soil water. That Is* at
least one molecule could be leached. As a practical matter, leaching
of organlcs Is Insignificant If 1) the municipal effluent or sludge
land treatment occurs at normal application rates, 2) a reasonable
drainage and cyclic establishment of sustained aerobic soil conditions
occur, and 3) groundwater remains deeper than 1-2 feet from the soil
surface. That 1s, for most usual municipal land application
situations, leaching or soil migration of specific organlcs does not
appear to be significant or detectable. Rapid Infiltration systems
(with requisite sandy or gravel conditions) and overland flow systems
are possible exceptions to this limited leaching behavior.
Organic compounds present at or near the soil surface (whether
adsorbed or 1n the soil-water solution) can also be transported 1n
rainfall runoff. The mechanisms and the algorithms to estimate the
magnitude 1n runoff of organic compounds are available in existing
non-point source models and research related to pesticides (Don1g1an,
1976; Frere, I975j Overcash, 1983). Some modification to account
for the organic sludge phase would be necessary to establish the
runoff Impact of organic priority pollutants. The reader should
utilize this extensive non-point source Information to assess the
runoff pathway.
-------
Specific Organic Compounds
Page 213
In a practical sense* the runoff of specific organlcs as a part
of municipal waste land treatment would need to be evaluated to see 1f
any critical levels could occur. Then the control measures would be
to use the best management practices approach that has been
established to manage non-point source pollution from all land uses.
These practices are usually adopted anyway as a means of controlling
erosion, as recommended agricultural practices, or 1n the course of
permit approval for such land treatment systems.
The broad category of organic species behavior encompassing
adsorption, leaching, and runoff, as a consideration 1n municipal
waste land treatment design, 1s generally a secondary facet. The
considerations of decomposition and plant response are generally more
important. Observations of the various transport pathways under
normal conditions of land treatment design have also not identified
leaching or runoff as major considerations, or at least not
unmanageable with sound design and operation.
Plant Response
The final pathway describing the terrestrial behavior of specific
organic compound centers on the interaction with vegetation. This
vegetation may be continuously present (e.g., forest, grasses) or may
be planted and harvested 1n cycles (e.g., corn, soybeans). An organic
compound Impacts vegetation 1n two broad ways:
1) At low concentrations, the compound partitioned
Into the soil water solution Is available for uptake
by the vegetation root system;
2) At high concentrations, a phytotoxlc response occurs.
The magnitude of these plant responses 1s dependent upon both the
organic chemical and the vegetative species. As with decomposition
rates, there are substantial direct and Indirect Information to
evaluate the plant response to numerous organic compounds.
Phytotox1c1ty can occur when the foliar portion of vegetation 1s
exposed to an organic compound or when the root system contacts an
organic compound. The applied concentrations (1n municipal effluent
or sludge) at which phytotoxlclty occurs 1s typically different for
foliar versus root contact. In the latter pathway the competing
adsorption and decomposition phenomena allow greater tolerance to
elevated concentrations of organic compounds. As an example, Figure 2
compares the critical levels of the organic priority pollutant 2,4
dlnltro phenol to produce growth reduction (Overcash et al, 1982).
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Page 214
OVFRCASH
IOO
90
80
70
. 60
^ 50
40
30
20
FOLIAR
—(at 2 weeks)
10 -
SOIL INCORPORATED
J I I L
1
I
J L
1.
10 20 30 40 50 60 70 80 90 100
SOIL CONCENTRATION, ppm
FIGURE 2. Foliar versus soil impact of 2,4 dinitro phenol
on corn in Lakeland sand.
(Overcash et al, 1982)
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Specific Organic Compounds
Page 215
As a converse to the phytotoxlclty caused by organic compounds,
many of these same compounds actually stimulate plant growth when
present at low concentrations 1n the soil. That 1s, the chemical acts
like a herbicide, insecticide or growth hormone when applied 1n small
amounts. An example organic compound group that Illustrates this
stimulatory effect at low soil concentrations is nonlonlc surfactants,
Figure 3. At high levels, the phytotoxlc response 1s seen, Table 4.
Figure 4 depicts the generalized plant growth behavior to applied
organic species. Depending on the compound, there are different
degrees of low level stimulation and varying critical soil
concentration at which phytotoxlclty occurs.
In municipal wastewater and sludge land application, the plant
response to organlcs present appears to be below the critical
phytotoxlc regime. No reported municipal cases of organic chemical
Impact on crop yields were found. Furthermore, preliminary
calculations of anticipated soil loadings compared to critical soil
concentration of some specific organic compounds (known from other
research studies) indicates that plant phytotoxlclty 1s not likely.
The second broad impact on vegetation from specific organic
compounds 1s the uptake from the soil-water solution. This 1s a
complex process that can Involve transfer Into the roots,
translocation to upper portion of the vegetation, decomposition
intraplant, and even migration back to the roots and soil (as growth
conditions 1n the vegetation change). Most frequently, data are
available on the measured concentrations of a specific organic 1n the
vegetation (sometimes differentiated by parts) as related to the
concentration found 1n the soil. Examples of these data for two
compounds are given 1n Table 5. In a review of a number of organic
compounds and the uptake by various vegetative species, there does not
appear to be any precise predictive mechanism for determining plant
levels at this time. With very low detection limits, most organlcs
can be taken Into plant roots or tissues; however, with simultaneous
decomposition and adsorption, the Issue of uptake remains
quantitatively unclear. In the absence of other soil processes (e.g.,
1n hydroponlc culture), there does appear to be an uptake preference
for cat1on1c>non1on1c>an1on1c. Since mineral soil adsorption operates
with a similar preference (cat1on1c>non1on1c>an1on1c), the actual
response of vegetation concentration 1s quite soil- and
chemical-specif 1c.
Once 1n the vegetation, an organic compound can be degraded as
Illustrated by the following discussion for nltrosamlnes.
"A detailed study of the plant concentration with
time (Dressel 1973, 1976) was conducted. The two
nltrosamlnes studied were found to accumulate to a
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PACHAPPA SANDY LOAM IDYL.WILD SOIL 6LEND0RA SOIL
¦ SOIL PENETRANT
¦ WATER-IN
E3 AQUA GRO
1000 8000 2QP00 900 BOOO ZQpOO 1000 8000 2QPOO
APPLIED SURFACTANT CONCENTRATION, ppm
FIGURE 3. Relative top weight of barley grown in soils receiving
various applications of nonionic surfactants (Valoras
et al, 1976)
-------
Specific Organic Compounds
Page 217
Table 4. Summary of critical phytotoxlc levels for surfactants
(Overcash and Pal, 1979)
Surfactant
Critical Soil Level (kg/ha)
Yield <80JB of Control
Three catlonlcs
Water-In (nonlonlc)
Aqua Gro (nonlonlc)
Soil Penetrant (nonlonlc)
Three anionics
>10
50 <>250
500 <>1,000
50 <>250
15 <>25
1,000 <>3,000
25 <>50
"15
"50
<300
Pachappa si
Glendora
Pachappa si
Idylwlld
Glendora
Pachappa si
Idylwlld
Glendora
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Page 218
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ui
CRITIC At
LEVEL
CRITICAL
LEVEL
CRITICAL
LEVEL
AMOUNT OF APPLIED CHEMICAL SPECIES
/ kg toil
FIGURE 4. Illustrative stimulation and phytotoxic response of
organic chemicals applied to soils.
-------
Specific Organic Compounds
Page 219
Table 5. Soil and Crop Levels of Benzene Hexachlorlde and Quintozene
Crop
Soil Level
(ppm)
Crop:So1l Ratio
(Average Range)
Benzene Hexachlorlde
Radish
Parsley
Watercress
Potato
Carrot
Sugar beet
Head lettuce
Grass
Quintozene
Potato
Carrot
Sugar beet
Head lettuce
Grass
0.05-5
0.02-2
0.5-50
0.03-0.4
0.05-5.0
0.02-0.44
0.02-0.41
0.02-0.41
0.5-1.9
0.02-0.2
0.02-0.2
0.07-0.14
Same
Same
0.001-0.03
Same
1.5-3.2
0.02-0.16
0.12-0.34
0.44-6.3
0.44-6.3
20-69
0.43-2.0
Same
Same
Roots
(leaves)
(heads)
(at 67 days)
(at 81 days)
(roots)
(0-5 cm tops)
(>5cm tops)
(roots 1-yr-old)
(>5 cm tops)
(whole plant)
(67 days)
(81 days)
(roots)
(0-5 cm tops)
(>5 cm tops)
(0.09-2.9)
2.6 (0.5-4.6)2
0.12 (0.04-0.18)Z
0.72 (0.5-1.2)
1.9 (1.0-2.8)
0.39 (0.23-0.48>f
0.24 (0.05-0.37)3
0.087 (0.03-0.15)3
0.23 (0.16-0.31
9.9 (5.1-16.0)5
3.6 (1.8-5.8)5
5.2 (2.7-9.0)3
1.7 (1.4-2.4)
0.28 (0.23-0.31)
26 {23-29)3
0.09
0.11 (0.03-0.25)3
19 (10-27)3
<0.03 (0.01-0t07)
11.0 (5.3-21)f
4.4 (1.4-6.0)5
0.44 (0.34-0.54)
3.8 (1.5-5.5)'
2.2 (0.2-1.2)
0.03 (0.01-0.03)
References:
\ Wallnofer et al. (1975)
J Hafner (1975)
3 Smelt (1976)
* Casanova and Dubroca (1972)
® Dejonckheere et al. (1975)
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OVERCASH
maximum value at 4-5 days after application and then
to decrease to background value within 12 days (Figure
5). The author postulated that an evapotransplration
pathway was responsible for the loss from plants, but
the experiment could not discern the relative magnitude
of evapotransplration and metabolic losses. Sander et
al (1975) also found that plant-absorbed nltrosamlne
disappeared with time for Lep1d1um sativum (garden
pepper cress). A final corroboration of the uptake
and disappearance of nltrosamlnes from lettuce was
performed with dimethylnltrosamlne (Dean-Raymond and
Alexander, 1976). A peak concentration appeared to
occur at 2 days after application with 150-fold
reduction after 15 days.
A total of 21 organic compounds have been found to undergo such losses
from vegetation. The extent to which organic compounds of
environmental concern (e.g., priority pollutants) exhibit this dynamic
Intraplant behavior cannot be determined at this time.
IMPLICATIONS RELATED TO THE PRESENT UNDERSTANDING OF ORGANIC COMPOUNDS
IN MUNICIPAL WASTE LAND TREATMENT SYSTEMS
The detailed research and field Investigations necessary to
document the land treatment behavior of specific organlcs has only
just begun. However, 1t 1s Important to build upon extensive existing
Information regarding organic species 1n the terrestrial system. It
1s also possible to look ahead to establish what some of the more
critical research needs might be as well as to put 1n perspective the
relative Importance of this area of municipal land treatment research.
This perspective, as presented here, 1s that of the author and was not
developed as a concensus of others concerned with municipal effluent
or sludge land application systems.
One should compare the situation of specific organic compounds
with that of heavy metals 1n municipal waste land treatment. Metals
accumulate 1n the soil system after undergoing a series of reactions
(adsorption, precipitation, chelation) that reduce the availability of
metals to vegetation. Since very little of a metal, which 1s 1n the
soil, Is translocated Into a plant, exceeding acceptable soil levels
would require a very long time to reclaim such a site. That 1s,
exceeding the levels at which vegetation parts are above food metal
limits or at which phytotoxlclty occurs leads to a loss reversible
terrestrial condition than found with organlcs.
-------
Specific Organic Compounds
Page 221
DIME THYLNITROS AMINE
400
CC
Ul
3O0
z
o
° 200
100
WTROSAMINE DETECTED
IN SOIL
. - IN PLANT
UETHYLNITROSAMINE
r-i.> i
12 I 4
LENGTH OF STUDY, DAYS
FIGURE 5. Intraplant loss of nitrosamines (Overcash and Pal, 1979).
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Page 222
OVERCASH
Organic compounds ("toxic" or other species) are characterized as
decomposing. I.e., the amount of a chemical 1s reduced with time after
an application to the terrestrial system. Thus the relationship to
vegetation uptake, runoff, microbial effects Is constantly changing
toward a lower Impact as time after application Increases. In a
sense, any excess, whether as a single dose or accumulated from
repeated applications, would be self-correcting In a relatively short
period after closure. This conclusion presupposes the typical
conditions of municipal sludge and effluent land application. The
decomposition half life for most organic compounds 1s less than one
year. Other organlcs (described previously) with extremely long life
are relatively Inert or Insoluble, factors which lead to a low
environmental impact. Thus excess metal loading can be much more
difficult to correct than a similar excess with organic compounds.
The observations of vegetation uptake of organlcs must also be
put Into perspective. First, there 1s very little Information on
vegetation levels at which Impact on the human diet would be of
concern. Thus the absolute concentrations 1n vegetation uptake cannot
be Interpreted as to whether any changes 1n design criteria are
needed. Second, even 1f organic compound concentrations were of
concern 1n vegetation 1t would be a short-term consideration. That
1s, 1f the vegetation 1s not harvested but 1s Incorporated Into the
soil, then the organic compound is subject to further decomposition as
the plant material 1s mineralized. Thus the soil levels would
approach background conditions after one or two crop cycles and the
organic compound would be successfully treated.
Municipal effluent land application Is an alternative to stream
discharge. This 1s an environmental trade-off between the stream
receiver and the terrestrial system. On a general basis, the
bloaccumulatlon ratio for an organic compound 1n soil Is low 1n
comparison to that found 1n an aqueous system. The microbial density
and time of contact are very much greater for an organic placed 1n the
terrestrial environment. Thus on a heuristic basis (since the level
of organlcs 1s fixed by the waste type, municipal effluent) the land
treatment of organlcs appears to have certain Inherent advantages.
For a municipal sludge, an alternative to land application 1s
often a landfill. These storage fadlltes are known to have
conditions that cause leaching of substances, Including organic
constituents. In contrast* migration of organlcs to groundwater from
municipal sludge land application systems has not been reported for
reasonably designed systems. Thus since municipal sludge must be
managed with some technique, land application has certain Inherent
advantages. These technology comparisons for land application of both
municipal sludge and effluent are developed not as all Inclusive, but
to emphasize that:
-------
Specific Organic Compounds
Page 223
1) municipal wastes must be managed and so one or more
alternatives must be selected;
2) use of the terrestrial system for treatment has a
number of important advantages for environmental
protection.
Discussion of specific organic compounds 1n relation to municipal
land application 1s often centered on "toxic" organlcs. Caution 1s
needed with this concept. Often the connotation of toxic has been
developed from the response of aquatic systems. The toxicity Is very
much reduced, of a different character, or non-existent when the
receiver system 1s Instead a terrestrial system. In addition, since
the somewhat more direct Impact (through stream-based drinking water)
of stream discharge has a greater human health potential, the
terrestrial approach (often with no direct human consumption of crops)
may offer a reduced likelihood of toxicity for organic compounds. The
direct animal consumption of municipal sludge organlcs 1s not covered
herein as such effects are primarily 1n the area of public health.
RESEARCH NEEDS
The Information most useful 1n improving the understanding of the
Impact of organic compounds 1n municipal effluent and sludge land
treatment were developed from the perspective described above as the
available data 1n 1983. These needs have been limited to a relatively
few of higher general priority. Many other meaningful research
objectives can certainly be developed as Individuals explore this area
of land treatment technology.
1) An established algorithm 1s needed to develop the
relationship between the concentration of an organic
compound 1n vegetation and the annual human intake
or burden that represents. Then the level of concern
from a health perspective can be established and linked
to observations of plant uptake. Without these
relationships, the research data on the behavior of
organic constituents 1n municipal land treatment systems
have only limited use.
2) Since the dominant terrestrial pathway for many organlcs
Is decomposition, the rates of loss from actual sludges
or effluents applied to land must be measured to verify
or correct available data on pure compounds.
3) A review of organic priority pollutants 1s needed to
compare with detailed analysis of organlcs (by mass
spectrometer techniques) found 1n municipal effluents
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Page 224
OVERCASH
and sludges. This comparison should Identify any major
organic species that might be of environmental concern*
but not presently Included 1n the priority pollutant lists.
-------
Specific Organic Compounds
Page 225
REFERENCES
1. Blakeslee, P. A. "Monitoring Considerations for Municipal
Wastewater Effluent and Sludge Application to Land." 1n.
U.S. E.P.A. Proceedings of the joint Conference on
Recycling Municipal Sludes and Effluents on Land, Nat'l.
Assn. State Univ. and Land-Grand Colleges# OuPont Circle,
Washington, D.C. 20036 (1972).
2. Buddln, W. "Partial Sterilization of Soil by Volatile and
Nonvolatile Antiseptics," J. Agric. Sc1. 6:417-451 (1914).
3. Casanova, M.» and J. Dubroca. "Residues of Pentachloro-
nltrobenzene and its Impurity Hexachlorobenzene in Soils
and Lettuce," Academle d'Agrlc. de France, 12: 990-998
(1972).*
4. Coffman, L. M., and D. D. Woodbrldge. "Effects of Gamma
Radiation on Aqueous Solutions of Phenol," Bull. Environ.
Contam. Toxicol. 11(5): 461-466 (1974).
5. Dean-Raymond, D., and M. Alexander. "Plant Uptake and
Leaching of Dimethylnltrosamlne," Nature 262C5567: 344-346
(1976).
6. Dejonckheere, W., W. Steurbaut and R. H. K1ps. "Residues
of Qulntozene, Hexachlorobenzene, Dlchloran, and
Pentachloroanll1ne 1n Soil and Lettuce," Bull. Environ.
Contam. Toxicol. 13:720-729 (1975).*
7. Dolgova, L. G. "Biochemical Activity of Polluted Soil,"
Pochvovendenl, 4:113-118 (1975).
8. Donlgan, A. S.» Jr., and N. H. Crawford. Modeling Pesticides
and Nutrients on Agricultural Lands. EPA-600/2-76-043.
332 pp. (1976).
9. Douglas, L. A., and J. M. Bremner. "A Rapid Method of
Evaluating Different Compounds as Inhibitors of Urease
Activity In Soils," Soil B1ol. Blochem. 3(4):309-316
(1971).
10. Dressel, J. "Uber das Vorkommen von N1trosam1nen 1n
pflanzlfchem Material." Landwlrt. Forsch. Sanderh.
28:273-279 (1973).
11. Dressel, J., "Relationship Between Nitrate, Nitrite and
Nltrosamlnes 1n Plants and Soil," dual. plant. PI. Fds.
Hum. Nutr. 25(3/4):381-390 (1976).
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OVERCASH
12. Feller, H.» "Fate of Priority Pollutants 1n Publicity Owned
Treatment Works," EPA 440/1-80-301, Effl. Guidelines D1v.
U.S. E.P.A., Washington, D.C. 180 pp. (1980).
13. Frere, M. H.» C. A. Onstad, and H. N. Holtan. "An
Agricultural Chemical Transport ModelUSDA ARS-H-3.
U.S. Govt. Printing Office. 54 pp. (1975).
14. Hafner, V. M. "Hexachlorbevzolruckstande 1n Gemuse - bedlngt
durch Aufnahme des Hexachl orokenzols aus dem Boden,"
Gesunde Pflanzen 27(3):37-48 (1975).*
15. Haselhoff, E. "GrundzHg der Rauchschadenkunde. Anlextung
fur Prufung und berurtellungder Elnwlrkung Von Rauchabgangen
auf Boden und Pflanze," Berlin (1932).
16. Jacobs, L. W. and M. T. Zablk. "Organic Chemicals 1n
Michigan Sewage Sludges." Department of Crop& Soil
Sciences and Pesticide Research Center, Michigan State
University, East Lansing, MI (1983).
17. Majetlc, V. A. and C. S. Clark. "Health Risks of Organlcs 1n
Land Application," J. Env. Eng. Dlv., ASCE 107, EE2:339-357
(1981).
18. Overcash, M. R. and S1ms, R. C. "TERRET0X: Catalogue of
Terrestrial Response to Organic Chemicals Literature,"
Dept. of Chem. Eng., N.C.S.U., Raleigh, NC (1981).
19. Overcash, M. R., J. B. Weber, and M. L. Miles. "Behavior of
Organic Priority Pollutants 1n the Terrestrial System:
D1-n-butyl Phthalate Ester, Toluene, and 2,4
D1n1trophenolWater Resources Research Institute of
North Carolina, Report 171, 94 pp. (1982)
20. Overcash, M. R. "Decomposition of Toxic and Nontoxic Organic
Compounds 1n Soils, Ann Arbor Publishers, Ann Arbor, MI,
485 pp. (1981a).
21. Overcash, M. R. and D. Pal. "Design of Land Treatment for
Industrial Wastes, Theory and Practice," Ann Arbor Science
Publishers, Ann Arbor, MI, 684 pp. (1979).
22. Overcash, M. R.» R. Khaleel, K. R. Reddy and P. W. Westerman,
"Non-po1nt Source Model: Watershed Inputs from Lahd Areas
Receiving Animal Wastes," U.S. E.P.A. report, 1n review,
(1983).
23. Pal, D., J. B. Weber and M. R. Overcash. "Fate of Polychlor-
Inated B1-phenyls (PCBs) 1n Soil-Plant Systems," Residue
Review, 74:45-98 (1980).
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Specific Organic Compounds
Page 227
24. Sander, J., M. Ladensteln, J. LaBar and F. Schwelnskerg.
"In: n-N1troso Compounds 1n the Environment#" P. Bogovskl
and E. A. Walker, Eds. Lyon, France: Intl. Agency for
Research on Cancer, 205-210 (1975).
25. S1ms, R. C. and M. R. Overcash. "Fate of Polynuclear
Aromatic Compounds (PNAs) 1n Soil-Plant Systems,"
Residue Review, 1n Press (1983).
26. Smelt, J. H. "Behavior of Qulntozene and Hexachlorbenzene 1n
the Soil and Their Absorption 1n Crops," Gewasbeschermung
7(3):49-58 (1976).*
27. Sommers, L. E. "Chemical Composition of Sewage Sludges and
Analysis of Their Potential Use as Fertilizers," Journal
of Env. dual. 6(2):225-232 (1977).
28. T1lch1n, M. J. "Land Treatment of Textile Dyeing
Wastewaters, M.S. Thesis, B1ol. and Agr. Eng. Dept.,
North Carolina State Univ. (1983).
29. U.S. Environmental Protection Agency. "Proceedings of the
Joint Conference on Recycling Municipal Sludges and
Effluents on Land," Nat'l Assn. State Unlver. and
Land-Grant Colleges, 1 DuPont Circle, Washington, DC
20036 (1972).
30. U.S. Environmental Protection Agency. "Fate of Priority
Pollutants 1n Publicly Owned Treatment Works," EPA
440/1-82-303, Eff1. Guidelines, WH-552, Washington DC
20460 (1982).
31. Valoras, N.» J. Letey and J, Osborn. "Nonlonlc Surfactant-
Son Interaction Effects on Barley Growth," Argon, J.
68(4):591-595 (1976).
32. Wallnofer, P., M. Ronlger and G. Englehardt. "Fate of
Xenob1ot1c Chlorinated Hydrocarbons (HCB and PCBs) 1n
Plants and Soils," Ze1t. Pflanzen. Pflanzenschutz
82(2):11-100 (1975).*
33. Weber, J. "Personal Communication from Pesticide Research,"
Weed Science Department, North Carolina State Univ. (1982).
*For translated version of this article, see Overcash, M. R.
"Decomposition of Toxic and Nontoxic Organic Compounds 1n Soil,"
Ann Arbor Science Publishers, Ann Arbor, MI, 48S p. (1981).
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Page 228
OVERCASH
QUESTIONS AND COMMENTS FROM THE FLOOR:
Dr. Michael Connor, Harvard School of Public Health: Animxl uptake
of organic compounds can be an important route in the assessment of the
risks of these compounds to humans. There have been instances where cods
grazing on sludge-amended lands have developed levels of PCBs in their
milk above FDA action levels. I hope that the final position paper
includes a discussion of this pathway.
Michael Overcash: Unfortunately, the final paper will not address
the direct animal consumption. This is an area primarily of health
effects related to specific organic chemicals and not precisely answered
at this time.
Stephen B. Smith, Black and Veatah, Denver, CO: I feel that an
important item has been missed in the presentation and discussion of your
paper and the previous paper on pathogens. This entails that most of the
treatment plants have a discharge to a stream and this stream, in turn,
is used for a water supply downstream, often in a very short distance.
The stream provides an excellent means of transportation for the patho-
gens and organic compounds.
Therefore, I would submit to you that land application, as a pro-
cess, is a substantially better choice than the direct discharge to a
stream of these pathogens or organics.
Michael Overcash: This is an Important and difficult concept since
complex risk assessments are needed. 1 think your conclusion regarding
land treatment advantages would probably remain correct.
Jack L. Cooper, National Food Processor$ Association: In plant
uptake, what part of the plant ie analyzed, the edible or non-edible? Is
there a tendency for the plant to exclude the organics from the edible
portions?
Michael Overcash: For some compounds this is certainly true.
Dr. Merry L. Morris, New Jersey Dept. of Environmental Protection:
Can you suggest a potential surrogate for soil monitoring of organics
degradation from sites at which high levels of organics nay be present,
such as at spill clean-up sites?
Michael Overcash: No.
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Specific Organic Compounds
Page 229
Harvey Luce, University of Connecticut: Researchers at Cornell
University in a recent communication recommend against all applications
of municipal sewage sludges to farm land because of "health risks from
toxic organic chemicals. Would you like to comment on this?
Michael Overcash: I believe the total evidence will indicate that
land treatment is a superior alternative for sludge since sludges must be
managed by some technique. Given that choices must be made Oft which
alternatives to use for sludge, I find that 1 disagree with those
researchers at Cornell who oppose the prudent use of land treatment.
William Pounds, Pennsylvania Department of Environmental Resources:
Rather than run a priority pollutants analysis on all sludge samples,
have you looked at using an indicator parameter, for example TOX? If you
exceed a certain level in this parameter, then it would be recommended
that a more detailed analysis for organics could be conducted.
Michael Overcash: From our experience I can suggest no surrogate
nor do I have any reason to believe that such a surrogate will be readily
found.
Richard J. Bull, Toxicology and Microbiology Division, EPA,
Cincinnati: Chemicals associated with the specific matrix with which we
are dealing are those that we have to be concerned about in order to
assess risks attributable to that matrix. The 'priority pollutant' list
was drawn up primarily from a perception of important industrial pollu-
tants not because they were the major constituents of municipal sludge.
A second complication is that determination of chemicals in municipal
sludge has been conditioned by and limited to those for which we have
analytical techniques. For example, we have been slAidying the extent to
which removal of mutagenic activity from municipal wastewater correlates
with removal of the priority pollutants. Secondary treatment of
wastewater was seen to remove priority pollutants present by more than
97%. On the other hand, removal of indirect mutagenic activity measured
in the Ames assay was leas than 5% in one case and less them 40% in
another. This simply shows that behavior of the priority pollutants in
the wastewater treatment plant is in no way related to the removal of one
type of biological activity considered important in evaluation of human
health hanarde. It seems -reasonably obvious that an effort is needed to
specifically identify those chemicals that possees toxiaologieal proper-
ties over which we have concern in sludge. Then we need to document the
extent to which they can actually impact health and the extent to which
they would present themeelvee in terms of a human exposure via the food
chain, drinking water, and other routes•
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OVERCASH
Michael Overcash: I have emphasized on a number of previous occa-
sions and in this conference paper that 1t 1s unlikely that the priority
pollutants will long represent the minimum limit of our interest in orga-
nics found in wastes.
Robert B. Dean, Lun-Dean Environmental Co., Copenhagen, Denmark:
The objectives of "no permanent degradation" is useful for research but
does not always correspond to what society is willing to accept. One
example of non-degradable organic substance that is regularly applied at
loads of kilotons per hectare is asphalt which permanently degrades the
soil. The only useful plants which can be raised on such land are indus-
trial plants or factories.
Michael Overcash: Interesting observation, but 1n all cases we
should start with the non-degradation criterion and be sure we know
beforehand why we have chosen to relax this standard for terrestrial
systems.
Michael Plewa, University of Illinois: The use of the Ames test can
identify the presence of mutagens in sludge. However, higher organism
such as plant assays in maize and Tradescantia can detect types of gene-
tic damage not measured in the Ames test. Also, it is important to note
that plants can be used as in situ or in laboratory monitors to evaluate
the mutagenicity of a sludge over time as well as the mutagenic potency
of different sludges. One final note, information exists in the litera-
ture that plants can activate some promutagens [i.e., dimethylnitrosa-
mine, benso(a)pyrene, and 2-aminofluorene] into the ultimate mutagenic
agent. Thus, some agents nay be taken up from sludges by plants and con-
verted into mutagens.
Phillip K. Hopke, University of Illinois: We have compared mutage-
nicity of S sludges using a battery of tester organisms. In the prin-
cipally domestic sludge, we found low levels of activity in the extracts
using Ames TAS8, and TA100t but did not see effects in higher eukaryotie
species. Only in the more industrialized sludges did we see mutagenetio
or aytogenic effects in the higher eukaryotes. One municipal sludge and
effluent were extremely toxic. This plant directly receives effluent
from a major chemical manufacturing plant and clearly municipal sludges
can be every bit as noxious as direct industrial treatment effluents. A
wide range of possible contamination levels must be considered.
Michael Overcash: In comment to Drs. Plewa and Hopke, 1 share with
you the complexity of Interpreting mutagen tests for sludges. Our
experience 1s that these tests are less than precise 1n determining the
actual mass loss of mutagens and hence, exposure. Thus, caution 1s now
needed.
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Specific Organic Compounds
Page 231
George Brands, US-FDA, Washington, DC: 1, Heed to oonsider uptake
of organies by (a) animate on pasture, (b) plante [and people, and in
food arope] through foliar absorption and adsorption and translocation.
Michael Overcash: We refer you to the conference question of Or.
Connor.
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METALS
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Page 235
UTILIZATION OF MUNICIPAL WASTEWATER AND SLUDGE ON LAND -- METALS
Terry J. Logan and Rufus L. Chaney
Agronomy Department
Ohio State University, Columbus, OH
and
USDA-ARS, Beltsville, MO
INTRODUCTION
The 1972 amendments to the Water Quality Act, which would spur the
construction of advanced wastewater treatment facilities and greatly
increase the production of municipal sewage sludge in the U.S. were one
year old when university researchers, representatives of the Federal
agencies and others met at the University of Illinois to develop a
coordinated program for research on application of sewage sludge to
land. Individual workgroups identified research needs and priorities on
a number of questions, including metals. The dramatic increase in
research on land application of sewage sludge in the following decade
has helped to provide answers to some of these questions, while, at the
same time, raising new issues and identifying new problems. In that
same period, Federal, State and local agencies have attempted to
formulate guidelines and regulations for the safe utilization and
disposal of sewage sludges on land.
The purpose of this paper is to examine the various issues
regarding the transmission of sludge-borne metals through the
soil/piant/water system and its impact on livestock and human health.
This paper is not intended as a comprehensive literature review of
metals, a task beyond the scope of this report. It will examine,
however, advancements made in the last ten years in our knowledge of the
fate of sludge-borne metals when applied to land, and will also discuss
the evolution of a regulatory approach to protect the food chain from
toxic levels of metals. The reader who comes to this subject with
little or no previous background is encouraged to consult a number of
excellent reviews which have appeared 1n the last decade (Sommers, 1980;
CAST 1976, 1980; Chaney 1980, 1983a, 1983b; Chaney and Giordano, 1977;
Page, 1974; Baker and Chesnin, 1976; Leeper, 1978; Ryan et al., 1982;
Walsh et al., 1976).
This paper will examine the transmission of metals from their
sources, through the sludge treatment process, into the soil and through
the plant and animal systems (Figure 1). Major issues listed in 1973
will be addressed and new research problems Identified In 1983 will also
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Page 236
LOGAN AND CHANEY
Pathways
Topics
He^uUitory Aingrooch
Metuls and their sources
Treatment process
Prelreutrnent
MetaJ removal
Metul chemistry of sludges
Metul binding (.'opacity of sludges
Sludge anaJy^i*
Metals to he regulated
(lute of metal addition to soil
Annual vs cumulative additions
"Clean sludge"
Soil
Biota
Uptuke and bioaccumulHtion
Metal effect* on soil biota
Other metal sources
Sol) metal-bindmg capacity
Melal reversion in soils
Kunoff and leaching
Background metal levels
Soil characterization:
pll, CUC, OMt Fo, A1 oxides
Site selection
Water quality for
livestock and man
Drinking water fttanrtards
Metal uptake^ metal bioavailability
Roto effects; competitive metal uptake
Metal restrictions for food-chain
crop&, dedicated site management
Translocation] inter and Intra
species variation, phytotoxicity
Food chain contamination
FDA "safe limits"
Metal interactions in absorption
Direct ingestion
Dedicated site management
Livestock
Metal accumulation In organs
Deficiency versus toxicity
Man
Dietary levels; metal interactions
in absorption
Direct ingestion
Human health effects
FDA "safe levels"
Figure 1. Schematic of the biogeochemical
discussed in this paper.
trace element system as
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Metals
Page 237
be discussed. Present and potential reoulatory approaches will also be
identified.
METALS IN SLUDGE
Metals of Concern
The 1973 Conference workshop group on Toxic Chemicals identified
the following elements as being of primary concern because of either
phytotoxicity or potential hazards to animals and man: Cd, Pb, Hg, As,
Se, Zn, Cu, and Ni and indicated that, of these, Cd, Pb, Hg, As, Se and
Zn should receive the highest priority because of their potential to
contaminate the animal and human food chain. At the same conference,
Chaney (1973) identified Cd, Cu and Zn as posing the greatest threat to
animal and human health through plant accumulation.
The Council for Agricultural Science and Technology (CAST, 1976)
identified Cd, Cu, Ni, Zn and Mo as the elements with the greatest
potential to accumulate in plants and pose a hazard to plants, animals
and humans. Lead, Hg, As, Se were not considered hazardous because
"they either have low solubility in slightly acid or neutral, well-
aerated soils or, as with Se, are present in such small amounts that the
concentration is low in soils." In addition, B was not considered
hazardous in non-irrigated regions, but could be phytotoxic to sensitive
crops at hot-water soluble concentrations > 1 mg/kg soil. Molybdenum
was included in the 1976 CAST report because the authors felt that "Mo
may accumulate in plants at concentrations sufficient to cause
molybdenosis in ruminant animals without prior warning from plant
behavior." By 1977, cadmium was receiving considerable attention as a
food chain contaminant, because of the extensive work by Japanese and
European scientists (Ryan et al., 1982) and the growing awareness that
Cd could readily accumulate in crops at concentrations which could
increase the dietary intake of the metal without causing crop
phytotoxicity. In 1979, the Federal government (EPA, 1979a) published
interim final regulations for the control of Cd erftry into the food
chain via land application of sewage sludges. These regulations will be
discussed in more detail later in the paper, but they dramatically
increased the focus on Cd and decreased the attention being paid to
potential problems from metal phytotoxicity.
By 1980, Chaney had introduced the term "Soil-Plant Barrier" in
assessing the risks to the plant-animal-human system from toxic
elements. Chaney (1983b) states that the "Barrier" protects the food
chain when one or more of the following processes limit trace element
transmission: 1) insolubility in the soil prevents uptake, 2)
immobility of an element in fibrous roots prevents translocation to
edible plant tissues or 3) phytotoxicity of the element occurs at
concentrations of the element in edible plant tissues below that
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Page 238
LOGAN AND CHANEY
injurious to animals. Chaney (1983b) lists Cd, Se and Mo as elements
which can escape the "Soil-Plant Barrier" and adds Be and Co as metals
which may also escape the "Barrier" but are primarily added to soil in
industrial wastes. As discussed later, the "Soil-Plant Barrier" can be
circumvented when animals directly ingest soil, sludge or vegetation on
which soil or sludge particles adhere.
Other Metal Sources
Although widespread application of sewage sludges to land may
provide the most ubiquitous source of metal additions to soil, other
sources can pose local problems. These include trace amounts of Cd in
phosphate fertilizers (Mulla et al., 1980; Williams and David 1973,
1976), contaminated soils in the vicinity of smelters (Hutchinson and
Whitby, 1974; Lagerwerff and Brower 1974), mine tailings (Benson et al.,
1981; Robinson et al., 1947) localized high natural concentrations of
specific metals (Lund et al., 1981), and metal-containing pesticides
such as lead arsenate. While these may have local significance, their
impact on the total metal burden to man is probably low. In many cases,
food chain crops are not grown in the vicinity of these sources, and
phytotoxicity greatly reduces the economic viability of these areas for
crop production.
Amounts
By 1973, results of extensive monitoring of metals in sludges were
available from the U.S., Canada and Europe. Large variations in the
concentrations of metals were found. The distributions were skewed
towards high concentrations (Dean and Smith, 1973) and arithmetic means
overestimated the average metal concentrations of most municiDal
sludges. Dean and Smith (1973) and, more recently, Sommers (1977) have
suggested using median metal concentrations as measures of averaae
contents of municipal sludges, and median values could represent
reasonably attainable background levels in sludges after pretreatment to
remove known s0ur^s* Table 1 gives median concentrations of the major
metals found , hJudges (Chaney, 1983b). These values are similar to
values reported by Paae (1974) for treatment plants in the U.S., Canada
and Europe. (1974) also reported that metal concentrations in
sludge were re v^ly unaffected by the sludge process used.
m*ta/he 197trft?^nre"Ce a"endees agreed that Pretreatment could reduce
metal concentrations in sludges, but there was no agreement as to the
level to concentrations could be reduced< *» the
drains and ga a ized plumbing were expected to maintain fairly hiqh
SS onTiJTstlcs0!^.1"6;;''. «P«1«lly In soft water are
difficult to obtain since many treatment slants
have only recently begun to routinely analyze sludge for metals (Forster
-------
Table 1. Ranges and median concentrations of trace elements in dry digested sewage sludges (Chaney,
1983b).
Reported Range
Element Minimum Maximum Median
mg/kg dry sludge
As
1.1
230
10
Cd
1
3,410
10
Co
11.3
2,490
30
Cu
84
17,000
800
Cr
10
99,000
500
F
80
33,500
260
Fe
1000
154,000
17,000
«g
0.6
56
6
Mn
32
9,870
260
Mo
0.1
214
4
Ni
2
5,300
80
Pb
13
26,000
500
Sn
2.6
329
14
Se
1.7
17.2
5
Zn
101
49,000
1,700
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Page 240
LOGAN AND CHANEY
et al., 1981). However, examination of individual pretreatment programs
reveal that metal concentrations can be drastically reduced. A
pretreatment program at the City of Defiance, Ohio sewage treatment
plant greatly reduced Cd and Ni levels in its sludge (Miller and Logan,
1979). Concentrations after pretreatment were similar to median values
reported by Sommers (1977) for cities in the North Central U.S. Other
U.S. cities have achieved median metal sludges through pretreatment.
Forms and Bioavailability
Speakers at the Conference did not address the question of
forms of metals in sew. kludges, and a search of the literature prior
to that time reveals vei j little research on the subject. Dean and
Smith (1973) in their paper from the Conference state that "...organic
matter in sludge complexes heavy metals...," but this is the only
reference made to the metal chemistry of sludges. Surprisingly,
characterization of metal forms in sludges was not identified by the
conferees as a research need. A year later, Page (1974) reported that
"as far as the author is concerned, no data are available on the
chemical forms of trace elements which occur in sewage sludges." As
recently as 1977, Chaney and Giordano (1977) indicated that "the
chemical species of the individual metals present is not known."
Since that time, however, there has been considerable progress in
the characterization of metal forms in sludges. Fractionation is one
method of characterization. Gould and Genetelli (1975) used elutriation
and filtration to separate sludge into four fractions: particulate,
supracolloidal, colloidal and soluble. More than 90% of the metals were
in the particulate fraction (> 100 mm diameter). Hayes and Theis (1978)
developed a fractionation scheme which employed elutriation and
filtration as well as acid and EDTA extraction of the particulates to
give the following fractions: soluble, precipitated (insoluble),
intracellular, and extracellular (adsorbed to the sludge biomass).
These two schemes are primarily physical and do not characterize the
chemical forms of the metals in sludge. Stover et al. (1976) presented
a fractionation scheme which partitioned metals into: exchangeable,
adsorbed, organically bound, carbonate and residual. The residual
fraction was uncharacterized, but would include such metal solid-phases
as sulfide and phosphate. Silviera and Sommers (1977) sequentially
extracted soil with 1M KNOt, 0.005M DTPA and 1M HNO3 and found that
metal extracted was generally proportional to the total content of the
metal in the sludge. Distributions between the fractions for a given
metal varied between sludges. In general, nitric acid extracted 50%
of the metal. Holtzclaw et al. (1978) extracted highly organic sludge-
soil mixtures from sewage lagoons with 0.5N NaOH and fractionated the
extracted metals into humic acid, fulvie acid and precipitable
fractions. Iron, Al and Zn were generally associated with the
precipitable fraction, while most of the copper was in the humic acid
fraction. Cadmium and Zn were in the precipitable and fulvic add
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Metals
Page 241
fractions. The authors concluded from these results that Cd, Ni arid Zn
would tend to be more mobile in soil than Cu.
The bioavailability of sludge-borne metals will depend on those
processes operating within the sludge which control metal activity in
solution and the competing processes operating in the soil. Sludges are
a sink as well as a source of metal, and some sludges may retain metals
much more strongly than others. As Corey et al. (1981) have pointed
out, the specific metal sorption capacity of a sludge may exceed the
soil's affinity for the metal, and the bioavailability of the metal will
be determined by the chemical characteristics of the sludge rather than
the soil. If this is so, the present regulatory approach which
considers only the total amount of metal added to soil and the soil's
untreated background metal-binding capacity (e.g. cation exchange
capacity) may overlook the role of the sludge itself in controlling the
bioavailability of sludge-applied metals.
Several important processes are believed to operate in the sludge
system to control solution metal activity. These include solid-phase
equilibria, adsorption-desorption, chelation and oxidation-reduction.
Attempts to characterize solid phase equilibria have assumed the
presence of discrete metal forms such as CdS, Pb phosphates, etc.;
however, Corey et al. (1981) and Corey (1981) have indicated that many
trace metals may be coprecipitated with the major metal cations in
sludge (Fe, Al, Ca) during the sewage treatment process. Predicting the
solubilities of minor constituents of solid solutions are difficult.
Studying the exchange reactions of metal cations on sludge is limited
because of the present inability to accurately predict or measure free
ion activities and because of the analytical problems associated with
working at the very low solution concentrations found in sludge systems.
Hendrickson and Corey (1981) have shown that, at low solution
activities, trace metals are specifically adsorbed with respect to
cations which have much higher solution activities, such as Ca or Mg.
In addition, organically complexed dissolved metals interfere with the
use of solid phase equilibria models.
Understanding the complexities of the sludge-metal system will
require further basic research, but this understanding is critical to
explaining the changes with time in metal bioavailability which occur
when sludge-borne metals are added to soil.
SLUDGE-BORNE METAL INTERACTIONS IN SOIL
Reaction Processes in Soil
Most microelements (with the exception of boron) are strongly
retained by soil and their concentrations in the soil solution are very
low. In the Conference Proceedings, Lindsay (1973) pointed out that
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Page 242
LOGAN AND CHANEY
much of the work on soil-metal reactions has been empirical with very
few basic studies to examine the precipitation reactions of metals in
soils. Lindsay felt that, although the exact reaction products of Zn,
Cd, Cu and Ni that precipitate in soils were not known, they likely
involved substitution in crystalline minerals and amorphous precipitates
as well as forming possible discrete silicate compounds; further,
adsorption could control metal availability.
Ellis and Knezek (1972) concluded that, in addition to cation
exchange, metals are specifically adsorbed to functional groups on soil
mineral surfaces. Adsorption rather than precipitation was thought to
be an important control on ionic activity at the low metal ion
activities normally found in soils, except at pH's above neutrality.
Soil organic matter was considered a strong sink for some metals such as
Cu and Zn, while the formation of soluble metal-organic complexes
reduced free ion activities and metal adsorption by reactive soil
surfaces. Leeper (1972) drew similar conclusions after extensive review
of metal reactions in soils.
Page (1974) also concluded that sorption reactions predominated for
metals added to soils; however, for sludge-borne metals, the metal solid
phases existing in sludges may be more stable than the reaction products
in soils. He also noted that boron would not be retained by soil since
it exists as undissociated boric acid at the pH's normally encountered.
Chaney and Giordano (1977) reported that the relative importance of
various metal-soil reactions in reducing plant-available metal levels
was not clear, and that no research existed on the effects of several
metals added simultaneously. The CAST Report (1980) indicated that
"adsorption is the predominant mechanism of trace metal removal from
dilute solutions by clay minerals, metal oxides, and organic matter, and
by whole soils." The report also indicated a strong pH-dependence of
soil adsorption-desorption processes involving Cd and Zn, with pH
affecting not only the metal species in solution but also the charge on
the soil surface. Cadmium and Zn could exist in soils as discrete
precipitates, coprecipitates with iron or aluminum oxides or alkaline
earth carbonates, and species bound to soil organic matter (CAST, 1980).
Corey et al. (1981) suggest that adsorption on mineral surfaces is
probably the dominant process controlling metal activities in soil
solutions and that a competitive Langmuir isotherm can describe the
relationship (Harter and Baker, 1977). They felt that trace metals are
primarily specifically adsorbed because the selectivity of adsorption of
trace metals is on the order of 103 to 106 over ions like Ca2+ and Mg2+.
Because of the very low activities of metals in soil solution compared
to the activities of more abundant cations {e.g. Ca, Mg, K), metals must
be specifically adsorbed if they are to occupy a large percentage of the
adsorption sites.
Corey et al. (1981) also concluded that, when metals are added with
sludge, solution metal activities would be controlled by adsorption to
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Metals
Page 243
soil mineral surfaces as long as the amount of metal added did not
exceed the capacity of specific adsorption sites in the soil. In this
region, metal activity should increase linearly with sludge metal
addition. At high sludge application rates, metal binding sites on the
sludge would control metal solubility, and further sludge additions
would not increase metal activities. If this is true, the metal
chemistry of a particular sludge which is applied to soil at high rates
may be as important in controlling metal uptake by plants as the metal
binding characteristics of the soil or the total amount of metal
applied. This may be significant in the USEPA approach to regulating
metal additions to soil, as discussed later. The considerations of
Corey et al. (1981) also indicate that the ratio of metal to specific
sorption capacity should be important in controlling metal ion activity.
Metal Reversion in Soils
Chaney (1973) in the Conference Proceedings reported that "metals
revert with time to chemical forms less available to plants." He gave
the example of fertilizer Zn reversion which had been shown to be quite
rapid. He indicated that the processes involved were poorly understood
but were most rapid in calcareous soils.
Chaney and Giordano (1977) attributed the term "reversion" to
Leeper (1972) and cited several cases of reversion of Cu, Zn, Fe and Mn
when added to soil as fertilizer salts or chelates. Chaney and Giordano
(1977) also reported that "in nearly every study on the effect of
incubation on the extractabi1ity of microelements added as sludge or
refuse compost, a continuing decline in extractabi1ity is observed."
The CAST (1980) Report carefully examined the data on residual
availability of Cd and Zn to crops after termination of sludge
application. The authors concluded that the residual effects were
indeterminate. Although there was some evidence that bioavailability of
the metals may remain constant or decrease over a period of years at a
constant pH, they felt that soluble metal concentrations would increase
if pH decreased.
It appears that, if metal reversion in soil does occur, the effects
are small and/or slow, and can be reversed by increasing soil acidity.
The lack of strong reversion processes in soil, especially for Cd (Lloyd
et al., 1981), implies that land used for food-chain crops which has
received large doses of sludge-borne metals must be managed for the
forseeable future to minimize metal uptake by crops. Further research
is needed on the long-term changes of sludge-metal forms in the soil,
and the effects of such factors as sludge-metal chemistry, soil chemical
environment and sludge organic matter decomposition on metal
availability to plants. The "time bomb" effect whereby sludge-applied
metals become more available over time (at constant pH) suggested by
Beckett and Davis (1979) has not been supported by research results.
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LOGAN AND CHANEY
Soil pH, Organic Matter Content and Cation Exchange Capacity Effects on
Soil Metal Binding Capacity
Chaney (1973) identified pH, cation exchange capacity (CEC) and
organic matter {OM) content as soil factors controlling metal toxicity
to plants. Soil pH might be more important than the amount of metal
added. Soil OM served as a source of CEC for metal cations and also
formed chelates with the metals, especially Cu and Ni. Chaney pointed
out that, at low soil pH's, chelation would decrease metal availability
to plants, but, at least in the case of Zn, chelation increased
availability at high soil pH's. He stated that CEC was important in
binding all cations, and "a soil with a high CEC is inherently safer for
disposal of sludge and effluent than a soil with low CEC." The
Conference Workshop Group 8 (Plant Response-Toxic Chemicals) felt that
research on empirical correlations of the toxicity of metals with soil
parameters, including CEC and pH was needed.
Soil pH: Soil pH is the parameter most consistently identified
in the literature as controlling metal availability. With the exception
of Mo and Se, all microelements are more labile at low pH, due to
hydrolysis of hydroxide species (Ellis and Knezek, 1972) and the
solubility of other solid phase minerals such as carbonates and
phosphate. Low pH also lowers the adsorption of metals to pH-dependent
specific adsorption sites on mineral surfaces (H+ is a competitive
cation), and lowers the CEC of soil OM.
Sludge additions to neutral or slightly acid soil tend to decrease
pH somewhat depending on CaC03 equivalent content of the sludge
(hardwater; lime in dewatering). Nitrification of sludge NH3, oxidation
of organic matter and sulfur containing organic compounds in sludge, and
oxidation of sulfides in anaerobic sludges all increase soil acidity,
while the high buffer capacity of sludge organic matter tends to
ameliorate these effects. Sludge additions tend to decrease the pH of
calcareous soils somewhat (CAST, 1980). At normal rates of sludge
addition (no greater than the nitrogen requirement of maize), the soil
buffer capacity and soil pH will determine the pH of the soil-sludge
mixture. The CAST Report (1980) concluded that the ability of
calcareous soils to maintain high soil pH with sludge additions greatly
reduced the risk to the food-chain from Cd and Zn uptake by crops for
crops grown on these soils.
Chaney et al. (1978a) limed acid soils that had not received sludge
for four years and found that Cd uptake was reduced. Liming also
appears to reduce the availability of native soil metals (Sommers,
1980).
The soil pH level considered to be effective in reducing metal
uptake by plants seems to be >^3.5 (Chaney, 1973; CAST, 1976; CAST, 1980)
and is required by USEPA (EPA, 1979a) for sludge applied to land for the
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Metals
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production of food-chain crops. This pH level is usually attributed to
Chumbley (1971) who developed guidelines in England for the control of
phytotoxic levels of Zn, Cu and Ni in soils. However, there is no
indication from the work of Chumbley and others that there is any
specific basis for selecting this pH other than observed effects on
metal uptake (CAST, 1980).
Solid-phase equilibria of the metals in soil may provide evidence
for the effect of pH on metal solubility (Lindsay, 1979) but that
analysis has not been done, and is complicated by not knowing if the
solid phases controlling metal solubility are sludge derived or are soil
minerals. Also, activities of organometal1ic complexes are not as
affected by pH as are free ion activities. There is no evidence from
recent research that pH 6.5 is not an effective control for metal uptake
by crops, and, except for acid soils strongly buffered by Al, this pH
level is easily attained and maintained by periodic liming. On more
acid soils, as found in unglaciated regions of the eastern U.S., raising
pH to near 6.5 is difficult and expensive. Once attained, this pH can
be maintained with lime additions every two to three years.
Cation exchange capacity: With the exception of As, Se, Mo and
B, the elements of concern are all cations and, as such, are attracted
by electrostatic forces to the predominant negative charges on soil
minerals and organic matter. Ellis and Knezek (1972) pointed out that
the metal cations, in addition to cation exchange, are specifically
adsorbed by covalent bonds to functional groups on clay surfaces. They
also reviewed early work (Bower and Truog, 1941; DeMumbrum and Jackson,
1957; Hodgson, 1963) which showed that hydrolysis of aquo groups
coordinated to the metals significantly affect their adsorption by
soiIs.
Most authors (Chaney, 1973; Haghiri, 1574; Latterell et al., 1976;
CAST, 1976 and 1980) recognize cation exchange capacity (CEC) as one of
the soil properties which are related to soil retention of metals.
Leeper (1972) was the first to suggest that soil CEC be used as an index
of the amount of metal (Cu, Ni, Zn) which could be safely added to soil
without causing phytotoxicity. The North Central Regional Research
Committee on Land Application of Sewage Sludges (NC-118) (EPA, 1980)
proposed in 1974 that medium textured soils in the region could safely
accept cumulative amounts of Cd, Ni, Cu, Zn, and Pb based on their
relative phytoxicities (in the case of Ni, Cu, Zn) and risk of food
chain contamination (Cd, Pb) as well as their relative uptake by crops.
In 1976 the Committee expanded the guidelines on cumulative metal
additions. Soils were arbitrarily divided into three groups by CEC
(< 5, 5-15, > 15 meq/lOOg soil) with cumulative additions as given in
Table 2. (The Ni levels were later raised to be the same as for Cu).
Even though no research showed a direct link between Cd uptake by
plants and CEC, the Committee felt that CEC was a readily and routinely
measured soil property that directly related to the ability of a soil to
-------
Table 2. Cumulative metal additions in soil.
Cumulative Metal Additions (lbs/acre)
<5 meq/lOOg 5-15 meq/100g >15 meq/lOOg
Cd
5
10
20
Ni
50
100
200
Cu
125
250
500
Zn
250
500
1000
Pb
500
1000
2000
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Metals
Page 247
minimize Cd solubility. The Committee also recognized that the effects
of CEC are compounded by the specific soprtion characteristics of so11
organic matter, Fe, Mn and A1 oxides. Organic matter binds metals by
chelation as well as by cation attraction. Iron, Mn, and Al oxides can
specifically adsorb metals yet do not have sufficient net negative
charge to bind metals by cation exchange. Increasing pH will increase
CEC of organic matter and other soil minerals with pH-dependent charge,
but an Increase in metal retention may also be due to decreased solubi-
lity of the metals adsorbed to solid phase minerals.
The CAST Report (1980) stated that "..CEC is best viewed as a
general, but imperfect, indicator of the soil components that limit the
solubility of Cd and Zn (i.e., organic matter, clays, and hydrous oxides
of iron, aluminum and manganese) instead of a specific factor in the
availability of these metals."
Corey et al. (1981) determined relative selectivity coefficients of
Cd with Zn, Cu, Ni and Fe for EDTA, and solid phase and soluble
complexes in a soil which had received 320 mt/ha of sludge. Selectivity
coefficients were similar for the three types of metal complexes and,
even at the relatively high metal levels in the soil, there was still
considerable selectivity for the different metals. This indicates that
these specific sorption sites are much different than the cation
exchange sites suggested by Bittell and Miller (1974) and Cavallaro and
McBride (1978). Corey et al. (1981), however, do not distinguish
between sludge and soil sites in their system.
Further research is needed to clarify the role of specific versus
non-specific metal absorption, and to determine the nature, persistence
and relative importance of sludge versus soil metal-binding sites.
Soil organic matter: Soil 0M can bind metals through cation
exchange and through the formation of organometallic complexes
(Mortensen, 1963; Hodgson, 1963; Schnitzer, 1969). On the other hand,
soluble metal-organic complexes can reduce sorption of metals and
increase their availability (Stevenson and Ardakani, 1972). Soluble
chelates and complexes allow faster diffusion from soil solid phases to
plant roots (Lindsay, 1974). Stevenson and Ardakani (1972) reviewed the
relative stabilities of metal-organic complexes of the trace nutrients
and found at pH 5 that they were in the order: Cu > Pb > Fe > Ni >
Mn > Co > Zn. More recent work (Mahler et al., 1980) has shown that
only a small percentage of Cd found in solutions from sludge amended
soil is organically complexed.
It has only been in the last six or seven years that researchers
have begun to characterize the role of sludge and soil organic matter in
metal complexation and retention. Sposito and co-workers (Holtzclaw
et al., 1976, 1978) extracted the humic and fulvic acid fractions of
sewage sludges and found that metals differ in their distribution in
these fractions. Other workers (Davis and Leckie, 1978; Newton et al.,
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LOGAN AND CHANEY
1976; Elliott and Huang, 1979; Chubin and Street, 1981; Elliott and
Denneny, 1982) have studied the effects of organic complexing ligands on
the adsorption of metals by soils and minerals. Ligands such as EDTA
which form strong metal complexes reduced metal adsorption while other
organic ligands had less effect. Adsorption of the ligand itself can
also affect metal adsorption.
While it is clear that both sludge and soil derived organic matter
can affect metal retention in soil and, therefore, metal uptake by
plants, this area remains poorly understood. Microbial biomass may also
bind metals (Kurek et al., 1982). Because of its highly complex nature,
advances in the knowledge of metal-organic matter reactions have been
slow. Recent developments in analytical methodologies should provide
needed new information on the chemistry of organometal1ic complexes and
their role in the retention and bioavailability of metals in soil.
Extraction Procedures for Measuring Bioavailability of Sludge Borne
Metals
Melsted (1973) in his Conference paper stated that "from past
experience, and the inability to establish uniform soil testing methods
for the determination of available essential heavy metals like zinc and
copper under a wide range of soil conditions, the likelihood of
developing standard methods of analyses for the toxic elements are
rather remote." Melsted suggested that, although methods of soil
analysis for available forms of some metals had been developed on a
regional basis, procedures for other metals can only be developed when
their available chemical forms are known. Workshop Group No. 8
identified an immediate need to develop laboratory diagnostic techniques
for measurements of available toxic metals in soils.
Cox and Kamprath (1972) discussed tests that were based on four
types of nutrient pools: (1) water soluble, (2) exchangeable, (3)
adsorbed, chelated or complexed and (4) minerals. Soluble
concentrations of the micronutrient metals (and other metals) are very
low in soils, and water extraction has been of little value as an
extractant for metals. However, hot water-extractable B has long been
used as an index of boron availability to crops (Wear, 1965).
Exchangeable Zn and Mn have been successfully correlated with plant
uptake (Cox and Kamprath, 1972), but the exchangeable levels of most
metals in soil are low. Cox and Kamprath (1972) felt that metal release
from soil minerals would contribute very little to plant uptake from
highly weathered soils, but could be an important source in arid and
semi-arid environments.
The most routinely used soil test procedure for available metals is
DTPA-TEA extraction (Lindsay and Norvell, 1978) which is primarily used
for Zn, Cu, Fe and Mn. In recent years it has also been used to extract
other metals (Bingham et al., 1975; Kelling et al., 1977, Street et al,,
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Metals
Page 249
1977). Korcak and Fanning (1978) compared DTPA with double acid (0.05N
HC1 + 0.025^N H2SO4) for extracting Cd, Cu, Ni and Zn applied to soil at
pH 5.6 and 6.5 as inorganic salts or in sewage sludge. The two
procedures were highly correlated with each other, but the DTPA
procedure was more sensitive to reduced solubilities of Zn and Cu at the
higher pH. Neither procedure correlated well with plant uptake when the
metal was applied with sludge, although correlations were improved when
the data for the two pH regimes were separated. The DTPA-TEA method is
sometimes replaced by an ammonium bicarbonate-DTPA test which allows
multielement analysis by plasma spectrometry (Soltanpour and Schwab,
1977).
Baker and his coworkers at Pennsylvania State University (Baker and
Amacher, 1981; Baker, 1980; Baker et al., 1976) have developed a
quantity/intensity method of soil testing for nutrients and trace
metals. DTPA is equilibrated with soil metals and interpretations
based on both the labile pool of metal able to equilibrate with DTPA
(quantity) as well as the free ion activity (intensity) are made. Baker
and Amacher (1981) give high, normal and low quantity and intensity
levels for Al, Pb, Ni and Cd.
Haq et al. (1980) examined the ability of nine extractants to
predict metal uptake by swiss chard from 46 Ontario soils with varying
degrees of metal contamination. No one extractant successfully
predicted uptake of Cd, Ni, Cu or Zn, but several of them, including
DTPA and ammonium acetate gave satisfactory results when combined in the
regression equation with other soil properties such as pH, OM and CEC.
More recently, workers have attempted to characterize Cd in soil
solution by saturation extraction or extraction with 0.1M Ca(NO3)2
(Corey et al., 1981; Lampert et al., 1982). Mahler et al. (F982) found
that saturation extract Cd correlated with Cd concentration in lettuce,
chard, tomato and corn, but the relationships were different for
calcareous and acid soils. The calcareous soils had more extractable Cd
than the acid soils, but the difference was not reflected in plant
uptake. This may have resulted from use of Cd S04~amended sludge, as
other studies did not find this pH effect on Cd solubility. Corey
et al. (1981) suggest that saturation extracts or electrolyte extraction
may be more sensitive to changes in the soil-sludge chemical environment
than more rigorous extractions, but the results of Mahler et al. (1982)
indicate that factors other than solution concentration may affect metal
uptake by plants.
As identified at the 1973 Conference, reliable soil test procedures
for the determination of available metals in soil need to be developed.
However, to date no such test or tests are available, and it is likely
that no one test or tests will be applicable to all metals on all soils.
Further research should emphasize regional development of soil test
procedures for specific metals and crops.
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LOGAN AND CHANEY
Movement of Sludge Borne Metals by Runoff and Leaching
Workshop Group 8 identified as a long term research needs a trace
element inventory which would include "leakage from the soil-root zone"
and "erosion from surface soils into lakes and streams." Only a very
small fraction of trace metals in soils is soluble. Page (1974)
reported that concentrations of the metal cations in neutral soil are
usually < 0.05 mg/ml, and, in the pH range common to soils (5-8.5),
soluble metal concentrations do not exceed 0.25 mg/ml. Thus, metal
cations do not leach readily from soil. However, under conditions of
heavy applications of sludge and low soil pH, there have been reports of
metal movement to depths up to several meters. Lund et al. (1976) found
increased levels of Cr, Cu and Zn to a depth of 2m beneath a sludge
drying bed that had been used for more than 20 years, while elevated Ni
and Cd concentrations were detected at 3.5m. Kirkham (1975) found
movement of Cd, Cu, Ni and Zn to a depth of 61cm below a 3-year old
sludge lagoon. Hinesly et al. (1972) and Boswell (1975) found movement
of metals to depths up to 45 cm with heavy applications of sludge (135-
158 mt/ha) to agricultural land. Emmerich et al. (1982) studied the
movement of sludge-applied metals to soils in a column study and found
no movement of metals had occurrred from the 476 mt/ha sludge
application after leaching with 5m of water over a 25-month period.
Although soil pH's were in the range 5.2-8.0 prior to sludge
application, nitrification of sludge nitrogen greatly lowered pH in the
soil zone below the sludge.
At annual sludge application rate < 15 mt/ha which are recommended
for efficient crop removal of sludge-nitrogen, leaching of metals should
pose little threat to groundwater resources for all but those sludges
with very high metal levels.
Because of the strong retention of metals by soils, loss of metals
by erosion and runoff transport of sediments should pose a greater
threat to water supplies than leaching. This would be particularly true
in instances of heavy applications of sludge to land adjacent to water
bodies. However, no research reports indicate that this occurs (Dowdy
et al., 1980). Even if some erosion and transport of soil containing
sludge-applied metals occurs, the low solubility of the metals will
result in very low metal levels in the stream or lake water. Proper
site selection and sludge application management should be adequate to
protect our water resources from metal contamination from surface runoff
and erosion.
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Metals
Page 251
METAL UPTAKE BY PLANTS
Introduction
Uptake of sludge-borne metals by plants is important for three
basic reasons. First, plants require several micronutrient elements for
normal growth; sludge can serve as a Zn, Cu, or Fe fertilizer. Second,
if excessive amounts of some elements are absorbed by plants, reduced
yield or plant death can result; sludge Zn, Cu, and Ni have caused
phytotoxicity when poorly managed. Third, plant uptake of some
microelements is the primary route for them to cause food-chain risk.
In 1973, little was known about plant uptake or phytotoxicity of
sludge-borne metals (Chaney, 1973). Results from excessive application
of microelement fertilizers or pesticides, or on soils developed over
metal-rich geologic anomalies provided nearly all the field data. Poor
sludge practices in the United Kingdom provided evidence that sludge
metals could cause phytotoxicity (Chaney and Giordano, 1977).
Much has been learned about metal uptake by plants in the last
decade. However, our knowledge remains incomplete — especially on
phytotoxicity, and on basic chemistry of metals in sludge-amended soils.
Many of the examples reviewed in this section will deal with Cd, partly
because of the human health implications of Cd, resulting in much
research on this metal.
Sludges as Microelement Fertilizers
Chaney and Giordano (1977) summarized results from studies of using
sludge to correct micronutrient deficiencies, and noted that "It seems
reasonable that wastes which are otherwise safe for use on cropland
could be applied to satisfy N or P requirements, and the waste could
simultaneously correct any Zn, Cu, etc., deficiencies." Since that
time, McClaslin and O'Connor (1982) have shown that sludge could also
correct Fe deficiency of sorghum in New Mexico soils. Irradiated raw
sludges were more effective than digested sludge, perhaps indicating
that reduction of soil iron in inert crystalline ferric oxides to form
the more plant available hydrous ferric oxide contributes to Fe
availability along with sludge organic matter-bound and chelated Fe.
At this time, sludge has been experimentally shown to correct Zn,
Cu, and Fe deficiencies. Boron, Mn, and Mo in sludge are seldom at high
enough concentrations to serve as fertilizers in the field. Composted
sludge provided all required microelements for horticultural potting
media (Chaney et al., 1980).
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LOGAN AND ChANEY
Phytotoxicity
Excessive heavy metal absorption can kill a plant, or allow normal
environmental stresses to kill the plant. Of the elements commonly
present in municipal sludge, Zn, Cu, Ni, and Mn are likely to cause
phytotoxicity with improper management of soil pH or cumulative metal
application. In a few industrially polluted sludges, Co could also
cause phytotoxicity. Sludge Mn is not generally a cause of toxicity,
but soil Mn can become more available due to sludge use, and Zn plus Mn
phytotoxicity can occur in strongly acidic soils (White et al., 1979b).
Excessive Cu, Ni, or Co usually cause injury of plant roots, and
inhibit translocation of Fe from roots to shoots; then phytotoxicity is
expressed as yellow (chlorotic) young leaves which is metal-induced
Fe-deficiency. Zinc and Mn are translocated more freely to the leaves;
although Zn and Mn can injure roots and induce Fe-chlorosis in some
species, their toxicity is usually manifested through injury of older
leaves and reduction of plant growth through interference with
biological processes (Foy et al., 1978). Some refuse composts are rich
enough in B to injure sensitive crops when applied at high rates (Purves
and Mackenzie, 1974; Sanderson, 1980).
Potential phytotoxicity is affected strongly by soil pH, other soil
properties, crop species and cultivar, sludge metal concentration, and
climatic factors. Soil pH, sludge application rate, and crop strongly
affect phytotoxicity (Table 3). Most vegetable crops and legumes
(dicots) are relatively sensitive to high levels of sludge metals in
acidic soils.
Although soil 0M or CEC are important in toxicity of added metal
salts (White and Chaney, 1980), there is little evidence of the
importance of these properties for sludge-applied metals (CAST, 1980).
Sludge metal sorption properties can dominate over soil properties in
controlling metal uptake (Corey et al., 1981). This could result from
sludge organic matter, hydrous Fe oxide, and/or phosphate. Webber
et al. (1981b) found that sludge Cu could not cause phytotoxicity unless
the sludge contained appreciably over 1000 mg Cu/kg. High metal
concentrations are also implicated in the studies by Williams (1980) and
Marks et al. (1980) where sludges rich in Zn, Cu, or Ni caused severe
yield reductions in vegetable crops when soil pH was low.
Most commonly, sludge metal phytotoxicity is observed only with low
soil pH (Marks et al., 1980; Chaney et al., 1978a). Lutrick et al.
(1982) applied a low-metal liquid digested sludge to an acidic
fine-textured soil in Florida. At high cumulative sludge rates
(300 mt/ha; over 700 kg Zn/ha.), soil pH declined substantially due to
oxidation of sludge N and S, reaching pH 4.6. Soybean suffered Zn + Mn
phytotoxicity; seedling leaves contained as high as 1190 mg Zn/kg and
725 mg Mn/kg. Toxicity was easily corrected by liming. In a field
study with a low metal sludge the soil at pH 6.2 and 5.4, received
-------
Table 3. Relative sensitivity of crops to sludge-applied heavy metals (Chariey and Hundemann,
unpublished).*
Very Sensitivet
Sens itivet
Tolerant§
Very Tolerant#
chard
mustard
cauliflower
corn
lettuce
kale
cucumber
sudangrass
redbeet
spinach
zucchini squash
smooth bromegrass
carrot
broccoli
'Merlin' red fescue
turnip
radish
flatpea
peanut
tomato
marigold
oat
ladino clover
orchardgrass
alsike clover
zigzag, Red, Kura and
crimson clover
Japanese bromegrass
crownvetch
alfalfa
switchgrass
'Arc' alfalfa
Korean lespedeza
red top
white sweetclover
sericea lespedeza
buffelgrass
yellow sweetclover
blue lupin
tall fescue
birdsfoot trefoil
red fescue
weeping lovegrass
hairy vetch
Kentucky bluegrass
Lehman lovegrass
soybean
deertongue
snapbean
Timothy
colonial bentgrass
perennial ryegrass
creeping bentgrass
* Sassafras sandy loam amended with a highly stabilized and leached digested sludge containing 5300 mg
Zn, 2400 mg Cu, 320 mg Ni, 390 mg Mn, and 23 mg Cd/kg dry sludge. At 5% sludge, maximum cumulative
recommended applications of Zn and Cu are made.
t Injured at 10% of a high metal sludge at pH 6.5 and at pH 5.5.
t Injured at 10% of a high metal sludge at pH 5.5, but not at pH 6.5.
§ Injured at 25% high metal sludge at pH 5.5, but not at pH 6.5, and not at 10% sludge at pH 5.5 or
6.5.
# Not injured even at 25% sludge, pH 5.5.
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LOGAN AND CHANEY
298 kg Zri/ha at 224 mt/ha of applied sludge. Romaine lettuce contained
only 67 and 225 mg Zn/kg at the respective pH levels (Chaney et al.,
1982).
Crops differ remarkably in metal uptake, and in tolerance of soil
metals (Table 3). Crops differ somewhat in tolerance of foliar Zn, Ni,
and Cu, and substantially in tolerance of foliar Cd (Bingham, 1979).
Mahler et al. (1978) and Baxter et al. (1974) noted that Zn or Cd in
leaves associated with 25% yield reduction of lettuce (Cd) or chard (Cd,
Zn) varied with soil pH; higher foliar metal levels were tolerated in
acid soils.
Further, crops differ in relative toxicity of soil Zn, Cu, and Ni,
and soil pH affects the relative toxicity coefficients for added soil
metals (Mitchell et al., 1978). Beckett and coworkers have studied
relative toxicity and additivity of metal toxicity (Beckett and Davis,
1978; Beckett and Davis, 1979), although they focused only on foliar
metal levels. Most of their conclusions are based on nutrient solution
or sand culture studies using soluble metal salts, which may
underestimate tolerance of foliar metals. They concluded that Zn and Cu
are largely antagonistic rather than additive. Metal additivity did not
occur until 0.5 to 0.67 of the "upper critical" foliar concentration was
reached. They concluded that the Zn (equivalent) equation of Chumbley
(1971) seriously underestimated safe sludge loadings because it presumed
total additivity. Mitchell et al. (1978) came to a similar conclusion
because the equation's relative toxicity coefficients for Zn, Cu and Ni
(1:2:8) were higher than observed in a metal interaction/additivity
study with wheat and lettuce. They also reported that excessive metals
could interact by competing for sorption sites in the soil. Added Cu or
Zn increased Mi in soil solution and Ni uptake by crops and hence Ni
phytotoxicity.
Knowledge of tolerance of foliar metal concentrations has
progressed, although agreement among researchers is incomplete
(Table 4). Some differences occur because chelated Fe in nutrient
solution is sorbed differently by monocots and dicots. Oavis and
Beckett (1978) found barley tolerated only 200 mg/kg foliar Zn in sand
culture (upper critical level), while Boawn and Rasmussen (1971) found
small grains tolerated 500 mg/kg foliar Zn when grown in soil {25% yield
reduction). White et al. (1979a) found tolerance to 400-600 mg/kg
foliar Zn among soybean cultivars.
Common Errors in Study of Toxic Element Uptake by Plants
Researchers have noted several major errors in experimental methods
(CAST, 1980). First, the source of metals added may strongly affect the
result, and second, the location in which the experiment is conducted
(field vs. pot studies) may affect the results. Potential problems in
nutrient solution vs soil studies were noted above.
-------
Table 4. Different estimates of foliar metal concentrations associated with appreciable yield
reduction due to single element metal toxicity.
Davis et al. (1978)
Melsted Chaney et al. Davis & Beckett (1978)
Element (1973) (1978a) Beckett & Davis, (1977)
25% YR* "Critical" 10% YR
mg/kg dry leaves
Zn
300
500
200
290
Cu
15
20-40
20
20
Ni
3
50-100
11
26
Cd
3
varies
8
15
Mn
300
500
_ -
* Denotes yield reduction
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LOGAN AND CHANEY
The first error is usually called the "salt vs sludge" error. When
metals are added as soluble metal salts (sulfate, chloride, nitrate),
they nearly always cause greater plant uptake and toxicity than when
applied in sludge. Metals in digested sludges should be much nearer to
equilibrium with sludge organic matter, with sparingly soluble inorganic
compounds, or occluded in CaC03 or other minerals (Corey et al., 1981).
Bloomfield and McGrath (1982) recently reported that a significant
difference remains even when metals are incubated with sludge after
digestion. Davis and Carlton-Smith (1981) reported results from adding
metals to raw sewage to subsequently obtain digested sludges with
desired compositions. Uptake of Cd and Zn by radish was similar for the
prepared sludges and sludges obtained from sewage treatment plants.
Sludge contains organic matter and hydrous Fe and Mn oxides, both
of which increase the specific metal sorption capacity of the soil
(Soon, 1981; Garcia-Miragaya and Page, 1978) and reduce plant
availability of Cd (Singh, 1981). Further, metal salts lower the pH of
the soil by displacing adsorbed H+; few authors have corrected soil pH
to the level of the control. Alternatively, soluble metal acetates
raise the soil pH as the acetate is oxidized; metal oxides or carbonates
also raise pH. Adding equimolar mixtures of N1SO4 and Ni(Acetate)?
caused little change in soil pH even at very high Ni applications which
lowered pH over 1.5 units when applied as NiSO4 (Chaney and Leech,
unpublished). Many authors have reported the salt-sludge difference
(e.g. Dijkshoorn et al., 1981). In light of research summarized in this
paper, it is inappropriate to purport that metal salt additions simulate
sludge metal additions.
The second error 1s generally called the "greenhouse vs^ field"
error. Greenhouse and growth chamber studies offer greater manageabi-
lity and reproducibility and lower cost than field studies (and do not
suffer from foraging wildlife). However, crop Zn, Cd, and Mn are
Increased 1.5 to 5 fold over field studies with the same soil, sludge,
and crop (deVlres and Tiller, 1978; deVrles, 1980). Davis (1981a) also
found higher uptake of Cu 1n outside and greenhouse pots than 1n the
field. This appears to result from 1) use of NH.-N fertilizers which
lowers soil pH more 1n pots than 1n the field; 2) higher soluble salt
levels 1n pots than field due to smaller soil volume for required fer-
tilizer salts; 3) confinement of plant roots to the small volume of
treated soil 1n pots, and 4) abnormal watering pattern and relative
humidity 1n greenhouse pot studies. The smaller the pot, the greater
the error. Another common error 1n pot studies 1s inadequate supply of
fertilizer nutrients to obtain maximum growth rates (Terman, 1974).
The pH of the soil immediately adjacent to plant roots (the
rhizocyUnder) is especially important in plant uptake of microelements.
When roots absorb NH4-N, the pH of the rhizocylinder soil declines, and
when the roots absorb NO3-N, the pH rises, and thus, the form of N
absorbed by the root has a strong influence on metal cation uptake
(Barber, 1974). In the field, most crop N is absorbed from the soil as
NO3-N; this would raise rhizocylinder pH (Nye, 1981). Use of NH4-N
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fertilizers also causes the pH of the bulk soil to decline since H+ is
generated when NH4-N is oxidized to NO3-N (Jolley and Pierre, 1977).
When metals are added as a constituent of sludge, plant uptake
depends on time since application. Rapid breakdown of organic matter
{especially at higher sludge rates) supplies organic ligands and NH4-N,
both of which facilitate metal diffusion and uptake (Barber, 1974;
Lindsay, 1974; Wallace et al.» 1977). Radish absorbed very high levels
of Cu and Zn and suffered phytotoxicity when grown on freshly sludge-
amended and heated (37 C) soils (Sheaffer et al., 1981); five crop years
later, soil temperature had almost no effect on metal uptake, and
healthy crops resulted (Chaney et al., unpublished) (Table 5). The
higher soluble salts in pot studies or high rates of recent sludge
additions can increase soluble metals by forming complexes (CI) or ion
pairs (SO4) with metals, thereby increasing metal diffusion and uptake
(Bingham, 1980).
Thus, although pot studies in greenhouse and growth chamber allow
the control of experimental variables needed to characterize details of
the soil-plant interactions of metals, most researchers agree that
regulations must be based upon field research. First year results, and
annual sludge rate in excess of crop N requirements cause errors even in
the field. Further, the error due to study of high metal concentration
sludges discussed earlier precludes obtaining results applicable to use
of low metal sludges in agriculture.
Plant Differences in Metal Uptake and Translocation
Plant factors: Crop plants differ widely in uptake of an
element, all other factors held constant (Chaney and Giordano, 1977;
Sommers, 1980; Peterson and Alloway, 1979). Growing on the same
sludge-amended soil, spinach may contain 10 times more Zn than tall
fescue, orchardgrass 15 times more Ni than corn, and chard 5 times more
Cu than tall fescue. A recent report by Davis and Carlton-Smith (1980)
shows relative concentration of Zn, Cu, Ni, Cd, Pb in foliage and edible
parts of 28 species grown in 10 kg pots of soil from two long term
sludge farms. This report is the widest published comparison of metal
uptake by crops from metal rich soils.
Differences in elemental concentrations in plants may result in:
differential 1on uptake by roots, soil-plant interactions and
differences in root distribution in the soil with depth.
Factors affecting microelement translocation: After a
microelement enters the root cells, its translocation to shoots 1s
controlled by metal and plant characteristics. Root cell sap contains
high levels of organic acids and amino acids which can chelate many
metals. Membrane surfaces and proteins contain functional groups which
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Table 5. Effect of soil temperature and time after sludge application on metal concentration in
radish leaves (Morella, Chaney, Decker, and Sheaffer, unpublished; Sheaffer et al., 1981).
First Crop Year Sixth Crop Year
iludge
Rate
mt/ha
Soil
PH
Metals
in Radish
Leaves
Soil
PH
Metals
in Radish
Leaves
Zn
Cu
nig/kg dry
Cd
Zn
Cu
mg/kg dry
Cd
Ambient (22 C)
0
5.3
64e*
9.8ef
1.0a
6.7
35e
5.1e
0.8ab
56
6.0
295de
16.6de
1.1a
6.5
95cd
7.6cd
0.6b
112
6.2
663bc
36.1b
1.8a
6.1
152b
9.0c
1.0a
Heated (35 C)
0
5.6
86e
6.8f
2.1a
6.7
27e
4.3e
0.5b
56
6.0
490cd
26.9c
2.8a
6.5
51e
6.9d
0.5b
112
5.9
1070a
59.9a
2.6a
6.3
108cd
10.7b
0.8ab
~Means followed by the same letter in the same column are not significantly different from each other
(p = 0.05).
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can chelate some metals. Thus, a metal can be trapped in the roots if
chelates formed in the root cells sap can not be transported into the
xylem. Xylem is the system of non-living tubes in plants in which water
and nutrients are translocated from roots to shoots. Most metals
reaching the xylem are pumped into it by specialized cells. These
cells, and chelates formed in the root cytoplasm, control whether a
plant translocates a metal. Jarvis et al. (1976) noted wide variation
among species in percent of absorbed Cd which was translocated to
shoots; species ranged from 10-to-90% translocated. Crops often called
Cd "accumulators" translocated a high percentage of absorbed Cd.
Generally, Zn, Cd, Mn, B, Se, and Mo are easily translocated
because they are weakly chelated. Copper, Ni, and Co are more strongly
chelated; a much smaller portion of the absorbed Cu is translocated to
shoots than of Zn. Pb, Cr, and Hg are so strongly held in the root
cells that very little is translocated to the shoots of crop plants.
Research has characterized chelation of Fe, Ni, Cu, Co, Zn, and Cd in
xylem sap, but only Fe citrate has been unequivocally identified
(Tiffin, 1977; Foy et al., 1978; White et al., 1981; Cataldo et al.,
1981). Amino acids control translocation of Ni and Cu in crop plants
(Tiffin, 1977; Cataldo et al., 1978). Citrate probably chelates Zn and
Cd in xylem sap (White et al., 1981; Chino and Baba, 1981), although
Cataldo et al., (1981) concluded that plant-absorbed Cd appeared in
non-citrate complexes.
Transport to storage organs: Many crops form storage or
reproductive organs (edible roots or tubers; fruits; seed) which are
used as food or feed rather than the whole plant shoot. Crops differ
widely in botanical type of storage organ formed, and in translocation
of microelements into the organ as it forms. The stored fat, protein,
and starch come from sugars and amino acids via phloem from foliar
photosynthesis. Some species have close control on composition of their
storage organs (maize; beans; potatoes; fruits), while storage organs of
other crops are readily increased in microelements when the leaves are
increased (wheat, oat, rice, soybeans; root crops) (CAST, 1980).
Interactions among metals may occur not only during root uptake, and
translocation to shoots, but also during transport to edible tissues
(Chaney et al., 1976). Although vegetable crop transplants grown in
media containing sludge compost may have increased Cd levels, Cd did not
increase in the edible portions of mature crops (Sterret et al., 1983).
A further source of difference among crops can be expressed as a
result of food processing. When many grains are processed into
"refined" flour products, the starchy endosperm is separated from the
mineral and fiber rich bran. Metals 1n rice, wheat, and corn refined
products are substantially lower than 1n whole grain products, although
there is increasing consumption of whole grain foods over more refined
products (Hinesly et al., 1979b; Chino, 1981; Kitagishi and Obata,
1981). However, oat groats contain the bulk of metals in oat grain
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LOGAN AND CHANEY
(Kirleis et al., 1981), and soybean cotyledons and normal soy protein
products are as high in Cd as the whole grain (Braude et al., 1980).
Cultivar Differences in Metal Uptake
The potential for breeding crop cultivars with reduced metal
concentrations or greater metal tolerance was noted in the 1973 Work
Group 8 report. Some very promising results were reported by Hinesly
et al. (1978; 1982) for differences in Cd and Zn uptake among maize
inbreds and maize hybrids. Bache et al. (1981) found smaller
differences in Cd in foliage or grain of maize cultivars adapted to
New York. These results indicate that Cd-excluder cultivars are
available for use on dedicated sludge farms. Some of the early
misunderstandings about crop uptake of Cd resulted from these
appreciable differences in Cd uptake among maize cultivars used by
several researchers (CAST, 1980).
Soybeans, however, differ much less than corn in relative Cd and Zn
uptake and tolerance (Boggess et al., 1978; White et al., 1979a).
Although lettuce cultivars differ in Cd and Pb uptake, the range is
small (CAST, 1980). Whether these smaller differences result from the
smaller genetic base of adapted soybean and lettuce cultivars, or other
differences between these crops is unknown.
Harris et al. (1981) recently reported on studies of differences in
metal uptake among six potato cultivars (3 early, 3 main crop) when they
were grown on an old sludge farm. The soil (pH 6.6) contained 1811 mg
Zn/kg, 19.6 mg Cd/kg, 752 mg Cu/kg; these metal concentrations exceed
median levels in sludges. Yet the washed, unpeeled potato tubers
contained only normal Cd levels (mean = 0.28 mg/kg dry), and did not
differ significantly among cultivars.
Wheat cultivars also differ in Cd transport to grain. Substantial
differences were found among types of wheat on soils containing
background Cd levels (Meyer et al., 1982). Durum types were much higher
in grain Cd (140 mg/kg) than soft red spring, soft red winter, hard red
spring, or white wheats (44 mg/kg). Durum wheats are a different
species (tetraploid) than other wheats (hexaploid). Grain Cd was not
significantly correlated with soil Cd, although low soil pH gave
slightly higher grain Cd for the non-durum samples.
Andersson and Pettersson (1981) reported a small range for grain Cd
among wheat cultivars grown in Sweden, Hinesly (T. D. Hinesly, Dept.
Agronomy, Univ. Illinois, personal communication) examined Cd in grain
of nine soft red winter wheat cultivars grown on pH 5.5 sludge-amended
strip mine soils (34 mg Cd/kg). Cultivars did not vary significantly in
grain Cd (with a range of 2.4-to 3.4 mg/kg and a mean of 3.0 mg/kg).
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Role of Sludge-borne Metal Sorption Capacity
A number of alternative explanations have been suggested during the
last decade for the apparently different effects of sludge-applied Cd on
crop uptake of Cd. These include: 1) that repeated additions are
different than single additions, also stated as annual additions of
sludge Cd cause different Cd uptake than cumulative additions; 2) that
sludge-borne Cd has either some or no persistent effect on crop Cd; and
3) that Cd salts, high Cd sludges and low Cd sludges have unequal
effects on crop Cd. These are important differences since they would
affect the regulatory strategy needed to protect humans from excessive
dietary Cd (Ryan et al., 1982). Recent re-analyses of the data on which
these different explanations are based have led to an underlying
mechanism or model which addresses these difficult questions.
At the 1980 meeting of the W-124 Regional Research Committee, Corey
introduced the concept that sludge is richer than soils not only in Cd,
but also in Cd-specific sorption sites. These specific sorption sites
sorb Cd on the order of 10® times more strongly than they bind Ca (Corey
et al., 1981). He reasoned that, as sludge application rate increases,
Cd activity will initially increase in the sludge-soil mixtures. The
increase should be nearly linear at low sludge rates, as the soil
Cd-specific sorption sites become progressively saturated. At still
higher sludge rates, the soil Cd-sorption sites become saturated, and
equilibrium Cd activity is now controlled by the ratio of Cd in sludge
to Cd-sorption sites in the sludge. Futher increase in sludge Cd
application would produce little or no further increase in Cd activity.
Soil pH would affect Cd activity regardless of the source of the
Cd-sorption sites. These concepts are discussed in Corey et al. (1981),
and are strongly supported by field results with sewage sludge on
several Wisconsin soils (Fujii, 1983).
The implications of this model include 1) Cd is adsorbed (hence
labile), rather than precipitated as an inorganic compound in soils;
2) Cd activity in soil-sludge mixtures will be affected by sludge Cd
concentration; 3) the concentration of Cd in crops may be a linear
function of sludge-applied Cd only at low sludge additions, and 4)
relative crop availability of an increment in soil Cd will depend on the
history of sludge application for the soil. The CAST (1980) report
concluded that these were indeed the characteristics of sludge amended
soils.
Street et al. (1977) found that activity of Cd in soils was below
that controlled by the least soluble inorganic Cd compounds for nearly
all soils. Thus, they concluded that sorption controlled Cd activity.
Further, Lloyd et al. (1981) reported that the Cd in soils of long-term
sludge farms was nearly 10056 labile.
Sludge applied Cd, as well as other Cd sources, remain available
for plant uptake for many years in acidic soils. Studies of crops grown
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LOGAN AND CHANEY
on long-term sludge farms indicate crops can absorb increased amounts of
Cd for at least as long as 20 years after the last sludge application
(Chaney and Hornick, in CAST, 1980; Mahler and Ryan, 1982; Kirkham,
1975; Chaney et al., 1977; LaConde et al.} 1979; Richardson, 1980;
Chumbley and Unwin, 1982; Davis and Carlton-Smith, 1980). Cd is also
persistent from phosphate fertilizers (Williams and David, 1973), from
mine waste contaminated soils (Davies and Ginnever, 1979; Takijima and
Katsumi, 1973), and in very old naturally Cd enriched soils (geochemical
anomalies) such as the at least 50,000 year old California soils
described by Burau (1980) and Lund et al. (1981), and the old New York
peat bog described by Cannon (1955) and Cannon and Anderson (1971).
The annual vs cumulative effect of Cd may now be explained by the
work of Mahler and Ryan (1982) who found that historic sludge
applications caused a persistent increase in Cd sorption capacity, hence
decrease in Cd uptake by crops. The slope of Cd concentration in chard
or corn leaves vs newly added sludge or salt Cd was strongly reduced in
previously sludged soil compared to the control non-sludged soils. It
appears that organic (Soon, 1981) and inorganic (Singh, 1981) materials
in sludge can provide the specific Cd sorption sites. This information
indicates that the "time bomb" (Beckett and Oavis, 1979) effect
predicted to occur after sludge organic matter is stabilized in soil has
no basis.
Further, Dowdy et al. (1981) deduced a new method to evaluate the
separate contribution of annual and cumulative applied Cd. Since annual
Cd is a part of the true cumulative Cd, these dependent variables are
co-variant; by using Cd applied up to the year before the present crop
(lag cumulative Cd) they could use multiple regression analysis. Their
study showed that cumulative Cd dominated over the effect of annual Cd
on Cd uptake to corn ear leaf or silage. Note that the presence of
organic and inorganic (salts, NHt) ligands in freshly sludged soils can
contribute to the apparent "annual" Cd effect.
Sludge Cd concentration has a strong effect on potential Cd levels
in plants grown in acid soils many years after the sludge has been
applied (Chaney et al., 1982}. Using orthogonal contrasts, they found
that, in addition to linear Cd rate and soil pH, quadratic Cd rate also
significantly affected Cd uptake by lettuce. The curves for lettuce Cd
vs sludge-applied Cd were not linear, but had much lower slopes after
the first sludge Cd increment. This effect was clear for sludges with
13 mg Cd/kg or 200 mg Cd/kg, but was especially important for the lower
Cd sludge. Using slopes for plant Cd vs soil Cd from experiments with
high Cd sludges, Cd salts, or Cd-salt amended sludges should no longer
be acceptable in estimating risk from recommended practices with low Cd
sludges.
Many scientists have argued that farmers should accept only low Cd
sludges because the cumulative applied sludge benefit is inversely
related to sludge Cd concentration. The above research indicates that
equal Cd applied in low or high Cd concentration sludges will cause
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Metals
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unequal effects on Cd in crops. In many studies, experimental results
were confounded by the factors discussed. In order to apply higher Cd
rates, high Cd sludges were needed. Usually, experiments showing high
Cd uptake used high Cd rates, high Cd concentration sludges, and high
Cd:Zn ratio sludges.
Many experiments using low Cd, low Cd/Zn sludges have found low Cd
in plants (Dowdy and Larson, 1975; Dowdy et al., 1978; Chaney et al.,
1978a, 1982; Schauer et al., 1980; Harris et al., 1981; Giordano et al.,
1979; Zwarich and Hills, 1982; deVries and Tiller, 1978; Sommers, 1980;
Webber et al., 1981a; Chang et al., 1982; Lutrick et al., 1982; Sheaffer
et al., 1981; Anderson and Nilsson, 1976; Gestring and Jarrell, 1982).
The effect of sludge metal concentration is also seen for other
elements. Sludge Cu concentration greatly affected Cu uptake and
phytotoxicity from equal Cu applications (hence unequal sludge
applications) (Gupta and Haeni 1981). This finding supports earlier
indications that potential phytotoxicity of sludge Zn, Cu, and Ni is
related not only to metal application rate, but also to sludge metal
concentration (Webber et al., 1981b; Marks et al., 1980). As expected,
sludge-applied Zn, Cu, and Ni persist in their plant availability, at
least in acid soils (Berrow and Burridge, 1981; Chaney et al., 1982;
Marks et al., 1980; Williams, 1980).
Metal Interactions Affecting Cd Level in Crops
Besides phytotoxic interactions, interactions affecting Cd
concentration in edible plant tissues are also very important. In 1973,
Chaney suggested that limitation of Cd:Zn ratio in sludges could limit
crop Cd to acceptable small increases or Zn toxicity would result. He
initially based this on the parallel increase of Cd and Zn in crops as
sludge rate increases or soil pH declines, and on already known
interactions of Cd and Zn in animals.
For vegetable crops, this interaction now appears to satisfy the
claims of Chaney (1973; 1980). Chaney and Lloyd (unpublished) amended
Sassafras si with Cd and Zn sulfates and added CaC03 as needed to
maintain equal soil pH. Romaine lettuce was grown for 6 weeks, and
analyzed (Table 6). Lettuce yield was substantially reduced at
400-to-500 mg Zn/kg in leaf tissue. At intermediate Zn levels, added Zn
reduced crop Cd concentration, and crop Zn concentration was reduced by
added Cd. However, the Cd concentration in healthy edible young lettuce
leaves (those grown after transplanting) was constrained to about
4 mg/kg by either 1) Zn phytotoxicity, or 2) remaining within the
recommended 1.0% Cd:Zn ratio (1.5% maximum on private cropland).
Related experiments were conducted by Hortenstine (1980) with
lettuce and radish and Webber (1980) with lettuce, with similar results,
although soil pH varied with treatments. Often small additions of Zn
-------
Table 6. Soluble salts of Cd and Zn added to Sassfras si and resultant Cd and Zn contents in lettuce
grown in soil at pH 5.8 (Chaney and Lloyd, unpublished).*
Added Cd Added Soil Zn (mq/kq)
(mg/kg) 0 30 60 90 120 150
mg Cd/kg dry young leaves
0 1.15 0.60 1.16 1.16+ 0.37+ 1.07+
0.75 8.14 5.68 4.21 4.55 4.63+ 4.95+
1.5 18.5 7.75 7.60 9.41 7.88+ 8.69+
3.0 25.2 15.2 15.0 19.3 17.2 21.4+
mg Zn/kg dry total shoots —
0 30 165 262 401+ 508+ 615+
0.75 31 154 240 312 425+ 842+
1.5 31 128 205 320 478+ 672+
3.0 37 102 185 293 406 522+
* Means of 3 replications.
+ Denotes phytotoxicity, yield reduced 355J or more from maximum.
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increase Cd movement to shoots, while higher Zn reduced foliar Cd
(Haghiri, 1974). Chaney et al. (1976) confirmed Haghiri's findings with
soybean foliage, but found that Cd movement to soybean grain was
strongly inhibited by increased Zn. Grain Cd:leaf Cd ratio fell from
over 1 to less than 0.1 as soil Zn increased. Unfortunately, monocots
do not appear to follow this pattern (oats - Chaney and White,
unpublished; wheat - Bingham et al., 1979; rice - Bingham et al., 1980).
However, movement of Cd to grain of monocots is not very great under
present EPA (1979a) regulations. The greater tolerance of monocots to
Zn in acidic soils could theoretically allow small grains with 2-5 mg/kg
Cd; however, dicots in rotation would indicate the pH mismanagement by
phytotoxicity and lead to limestone application.
Although the above research was conducted with metal salts, or
metal salt-amended sewage sludge, the parallel increase of Cd and Zn is
apparent in several research studies in which low metal sludges were
applied to acid soils. For foliar Cd to exceed a few mg/kg, plant Zn
approaches phytotoxic levels, (Chaney et al., 1978a, 1978b, 1982;
Zwarich and Mills, 1982; Gestring and Jarrell, 1982; Dowdy and Larson,
1975). The Cd:Zn ratio limitation was meant to add additional
protection under the conditions where soil pH was poorly managed. The
EPA (1979a) regulations adequately restrict metals in vegetable crops in
soil at pH 6.5 or above.
METAL ACCUMULATIONS BY ANIMALS AND THEIR EFFECTS
Pathways for Transfer of Metal to the Food-chain
Sludges are applied to land in many fashions. These management
options allow substantially different amounts of sludge-borne metals to
enter the food-chain, by different routes. High exposure can come
through ingestion of sludge-covered forage by livestock, while mixing
sludge into the soil uses reactions in soils and properties of plants to
largely prevent exposure.
Sludge adherence to forage crops: Spray-applied liquid sludges
form a thin film covering crop foliage and, if not removed immediately
by rainfall or irrigation, dry and adhere strongly (Chaney and Lloyd,
1979; Jones et al., 1979; Bertrand et al., 1981). Sludge adherence is
directly related to solids content of the applied sludges, and to sludge
application rate. Growth of crop biomass dilutes the sludge percentage
in harvested forage.
Digested sewage sludge has adhered to all crops studied, although
crops do differ in relative adherence due to differences in structure
and growth habits. Adherence is easily characterized because levels of
many elements (Cu, Pb, Cr, Fe) in/on sludge-contaminated forages are
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LOGAN AND CHANEY
much greater than levels ordinarily possible by uptake-translocation by
plants. Many reports on uptake of microelements from surface-applied
sludges have presumed uptake when sludge adherence fully explains the
observations.
Another possible route of entry to food-chain is through farm
equipment. Dalgarno and Mills (1975) reported that baled hay was
enriched in Cu above levels found in/on the sampled forage crop. They
presumed that the baling equipment lifted high Cu swine manure from the
soil surface (or possibly the thatch layer). This route is poorly
demonstrated. Silage can also contain soil, and the soil can interfere
with microelement availability (Lamand, 1979).
When increased levels of microelements in forage indicate sludge
adherence, all constituents present in the sludge contaminate the
forage. Not only microelements, but also macroelements, pathogens
(Brown et al., 1980) and toxic organic compounds (Fitzgerald, 1978) are
increased.
Ingestion of sludge-amended soil or sludge from the soil surface:
Grazing animals consume soil as part of the normal grazing process.
This was noted initially during study of the excessive wear of teeth of
sheep and cattle. Using soil Ti (not appreciably absorbed by plants) as
an indicator/tracer on soil in feces, Healy et al. (1974) found that wet
weather and excessive stocking rates caused forages to be trampled into
the soil and increase soil adherence and ingestion. Although soil is
normally only 1-2% of sheep's diet, soil could reach 24% in worst cases.
Mayland et al. (1977) reported that cattle grazing dryland-grown
crested wheat grass consumed considerable quantities of soil. Because
the cattle ate the plants complete with soil-laden roots, the ingested
diet contained 20% soil. Fries (1982) recently reviewed soil ingestion
by dairy cattle. Under good management, soil seldom exceeds 3% of dry
diet.
Sewage sludge or composted sludge can be ingested from the soil
surface. Decker et al. (1980) estimated that cattle grazing tall fescue
pastures fertilized with sludge compost consumed 3.2% (1977) and 1.0%
(1978) compost (of dry diet) based on fecal analysis. Compost did not
adhere to the plant but lay on the soil surface.
Soil/sludge ingestion can also expose humans to applied
microelements. Some children and adults deliberately consume soil in a
practice called "pica." If the soil is rich in Pb (over
500-1000 mg/kg), individuals may absorb excessive Pb (Wedeen et al.,
1978; She!lshear, et al., 1975; NRC, 1980a). Children also
inadvertantly ingest soil and dust due to hand-to-mouth play activities,
and mouthing of toys, etc. (Sayre et al., 1974; Baker et al., 1977;
Roels et al., 1980; Hammond et al., 1980).
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Soil or sludge ingestion can be an important process allowing entry
of sludge-borne metals into the food-chain particularly when the element
is poorly absorbed by plants (soil level exceeds plant level). For some
elements (Zn, Cd, Mn, Se), plant levels often exceed soil levels and
plant uptake is the more important route. However, soil ingestion is a
potential route for allowing excessive exposure to Pb, Fe, Cu, F, As,
Hg, Co, Mo and Se if these elements are present at high levels in
surface soil (e.g. Thornton and Abrahams, 1981). Further, soil
ingestion can interfere with availability to animals of microelements in
feedstuffs (Suttle et al., 1975).
Research has shown that applying sludge to recently mowed or grazed
fields, and waiting to allow the crop to grow and dilute the adhering
sludge, can keep the sludge to 3-5% of dry forage. These practices,
coupled with use of sludges low in metals and toxic organics, protects
the health of livestock and safety of animal food products. Subsurface
injection of sludge removes this food-chain pathway, and is clearly the
best management practice for sludge application to forages/pastures.
Plant uptake of metals from soils: Some elements are easily
absorbed and translocated to food-chain plant tissues (e.g. Zn, Cd, Mn,
Mo, Se, B), while others are not readily transported. The poorly
translocated elements are strongly precipitated or bound in the soil, or
are retained in plant fibrous roots, and are not translocated to plant
foliage in injurious amounts even when soils are greatly enriched (e.g.
Fe, Pb, Hg, Al, Ti, Cr3+, Ag, Au, Sn, Si, Zr). Even though an element
may be easily or relatively easily absorbed and translocated to foliage,
phototoxicity may limit plant levels of the element to levels safe for
animals (e.g. Zn, Cu, Ni, Mn, As, B).
These concepts were developed over many years by many scientists.
Several reviews are very helpful (Underwood, 1977; Allaway, 1977; Reid
and Horvath, 1980; Ammerman et al., 1977; Chaney, 1980, 1983b). Chaney
introduced the term "Soil-Plant Barrier" to describe these concepts when
considering sludge-soil-plant-animal relationships of microelements.
Historically, plant absorbed residues of Se and Mo have caused localized
poisoning of livestock. Direct ingestion of soil or sludge circumvents
the protections of the soil-plant barrier. Many elements are so
insoluble or non-toxic that animal health is not affected even if
ingested soil or waste contains the element (e.g. Cr3+, Zr, Ti, Si, Al,
Sn). However, direct ingestion of soil or sludge rich in some elements
(e.g. Cu, F, Zn, Pb, Fe, As, Co, Hg) allows risk to livestock when risk
would have been insignificant if the sludge were mixed with the surface
soil (0-15 cm).
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LOGAN AND CHANEY
Metal Interactions in Animals
During the last decade, many studies were conducted to determine
whether direct ingestion of sludges or high Cu manures would allow
microelements to injure livestock. Researchers fed levels of
waste-borne Cu, Zn, etc., high enough to severely poison animals based
on research in which single metal salts were added to diets.
Evaluation of the potential risk to animals of sludge-applied
microelements is very complex. Animal species differ in tolerance.
Tolerance is influenced by age, with younger animals generally more
sensitive. Total and relative element concentration is affected by crop
species and cultivar, plant age, soil pH, soil organic matter, soil
temperature, and other factors. Sludges differ in levels of elements
and ratios among elements which interact in the animal. Particular
toxic elements interact with other elements in the diet, often
inversely. Because these interactions are often the basis for observed
toxicity, interactions are very important in assessing risk of
sludge-applied microelements.
Chaney (1983b), has provided a detailed discussion of exposure,
interactions which affect risk, etc., for the principal metals in
municipal sewage sludge (see summary in Table 7). Interactions are
especially important in allowing or preventing toxicity of ingested Cu,
Mo, Fe, Zn and Cd.
"Domestic" low metal sewage sludge contains a mixture of
potentially toxic elements. When sludge is ingested, increased dietary
Zn is balanced by normal or high levels of Cu and Fe. Increased Cu is
balanced by Fe and Zn which reduce Cu toxicity in ruminants. Although
many thought high Cu swine manure would poison Cu-sensitive sheep based
on "toxicology" studies, manure Cu has not poisoned sheep in feeding or
grazing studies (Bremner, 1981; Poole, 1981). Sewage sludge ingestion
has not even caused Cu accumulation in liver of cattle fed sludge
(Kienholz, 1980; Edds et al., 1980; Smith et al., 1979; Decker et al.,
1980) unless sludge Cu was high (Baxter et al., 1980; 1982). Low Cu,
high Fe sludge allowed Fe-induced Cu-deficiency in cattle grazing tall
fescue pastures (Decker et al., 1980).
Accumulation by Animal Organs
Animals have homeostasis mechanisms for most elements (Underwood,
1977). High dietary Zn, Cu, Mn, Ni and Fe increase intestinal and liver
concentrations of the element, but have little effect on other tissues.
When feeding of the enriched diet ceases, tissue levels return to
normal. Lead can build up in bone and kidney in forms slowly released.
Inorganic Hg can build up in liver, and organic Hg in fat deposits and
nerve tissue in forms slowly released. Fluorine can build up in bone as
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Table 7. Maximum tolerable levels of dietary minerals for domestic livestock in comparison with
levels in forages.
"Soil- Level in Plant Foliage* Maximum Levels Chronically Toleratedt
Plant Normal Phytotoxic Cattle Sheep Swine Chicken
Element Barrier" — mg/kg dry foliage -- mg/kg dry diet
As, inorganic
Yes
0.01-1
3-10
50
50
50
50
B
Yes
7-75
75
150
(150)
(150)
(150)
Cdf
Fails
0.1-1
5-700
0.5
0.5
0.5
0.
Cr3+, oxides
Yes
0.1-1
20
(3000)
(3000)
(3000)
3000
Co
Fail?
0.01-0.3
25-100
10
10
10
10
Cu
Yes
3-20
25-40
100
25
250
300
F
Yes?
1-5
—
40
60
150
200
Fe
Yes
30-300
—
1000
500
3000
1000
Mn
7
15-150
400-2000
1000
1000
400
2000
Mo
Fails
0.1-3.0
100
10
10
20
100
Ni
Yes
0.1-5
50-100
50
(50)
(100)
(300)
Pbf
Yes
2-5
30
30
30
30
Se
Fails
0.1-2
100
(2)
(2)
2
2
V
Yes?
0.1-1
10
50
50
(10)
10
Zn
Yes
15-150
500-1500
500
300
1000
1000
* Based on literature summarized in Chaney (1983b).
t Based on NRC (1980b). Continuous long-term feeding of minerals at the maximum tolerable levels
may cause adverse effects. Levels in parentheses were derived by interspecific extrapolation by
NRC.
+ Maximum levels tolerated based on human food residue consideration.
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LOGAN AND CHANEY
fluoroapitite, a form slowly released. Cadmium can accumulate in liver
and kidney in the form of metallothionein; Cd has the longest biological
half-life of the elements of concern in sludge (about 20 years in
humans).
Potential Effects of Sludge-borne Cadmium in the Food-chain
In 1973, relatively little was known about Cd in food and risk to
humans. The occurrence of Cd-disease in Japan had just been announced.
Toxicologists still thought hypertension could be caused by Cd. Food
specialists thought daily Cd intake was nearly at the safe maximum level
based on meager knowledge of Cd toxicology and poor analytical data.
Research on Cd risk has been especially intense because of these
fears, and from this work, a much more complete understanding of Cd risk
has developed.
Cd exposure and health effects: Cadmium is an unusual and
difficult case for evaluation of risk to the food chain. In contrast to
other elements, Cd has a long biological half-life in humans—generally
considered 20 years. Absorbed Cd is bound to a low molecular weight
protein to form metallothionein which is accumulated and retained in the
kidney for a long period. High metallothionein-Cd in the kidney can
lead to adverse health effects in the kidney.
Over a lifetime, chronic food chain Cd exposure can cause different
health problems than those experienced from acute exposure. Long-lived
animals (e.g., humans) are at greater risk o7~~this chronic exposure
health effect than are short-lived animals (wildlife; domestic animals).
Accumulation of Cd in organ meats (liver, kidney) was the basis for
suggesting a low dietary Cd tolerance in domestic animals rather than a
direct health effect to the animals (NRC, 1980b).
The potential risk of excess soil Cd to humans has been clearly
documented. Adverse health effects resulted from prolonged consumption
of foods grown locally on Cd enriched soils (Tsuchiya, 1978; Friberg
et al., 1974; Hammons et al., 1978; Kobayashi, 1978; Nogawa, 1978). A
large number of Japanese farmers suffered Cd health effects after
long-term ingestion of Cd-enriched rice grown in paddies polluted by Zn-
and Pb-mining wastes or Zn-, Pb-, and Cu-smelter emissions in at least
7 different areas of Japan (Kobayashi, 1978; Takijima and Katsumi, 1973;
Shigematsu et al., 1979; Kjellstrom et al., 1977; Kojima et al., 1979;
Saito et al., 1977; Nogawa, 1978; Nogawa and Ishizaki, 1979; Nogawa
et al., 1975; 1978; 1980; 1981). The farm families consumed their own
rice due to cultural factors and tax policy. Rice Cd concentration and
number of years exposure were both strongly related to the incidence
rate of Cd health effects. A smelter enriched area in Belgium may have
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caused Cd-induced renal disease (Roels et al., 1981a) although route for
exposure and increased kidney Cd have not yet been demonstrated.
The name "itai-itai" disease (translated as ouch-ouch disease) came
from expressions of pain by women suffering repeated bone fractures due
to Cd-induced osteomalacia. Although the osteomalacia brought attention
to this environmental Cd disease, severe osteomalacia does not
frequently result in humans ingesting excessive Cd; osteomalacia appears
to result in Cd-exposed individuals only when dietary Ca is low. Renal
proximal tubular dysfunction (Fanconi syndrome) is the first health
effect of excessive chronic Cd exposure. The renal disease had high
incidence in areas where Cd exposure was increased, and showed a
dose-response relationship with Cd exposure (expressed as "Cd level in
rice-times-years ingested"). All individuals with advanced itai-itai
disease had severe proteinuria, a characteristic of the kidney disease.
Renal disease subsequently proceeded to mild osteomalacia in some
European workers who ceased exposure when the kidney disease was
identified (Kazantzis, 1979). However, this aspect of Cd disease is
poorly understood. Sub-clinical osteomalacia is found in many of the
Japanese farmers who experience renal disease but not "itai-itai"
disease (Mukawa et al., 1980).
Renal tubular dysfunction (Fanconi syndrome) resulting from Cd
ingestion is quite different from classic kidney failure. Fanconi
syndrome seldom proceeds to kidney failure requiring dialysis.
Kjellstrom (1978) indicated that Fanconi syndrome (low molecular weight
proteinuria, glucosuria, aminoaciduria, phosphaturia) is the first Cd
health effect; if Cd-exposure (rate-times-duration) is increased, kidney
stones and osteomalacia/osteoporosis may result. Kjellstrom et al.
(1979) found greater mortality (shorter life span) in Cd exposed
workers. Nogawa et al. (1981) found significantly greater mortality
risk in farmers with proteinuria. Neither hypertension nor prostate
cancer incidence are increased even when proteinuria is severe (Friberg
et al., 1974; Doyle, 1977; Hammons et al., 1978; Tsuchiya, 1978; Ryan
et al., 1982; Commission of the European Communities (CEC), 1978;
Kjellstrom and Nordberg, 1978; Kjellstrom et al., 1979; Lauwreys et al.,
1980; Nogawa, 1978; Nogawa et al., 1981; Shigematsu et al., 1979).
Although Kopp et al. (1982) claimed that hypertension in Cd-fed rats
indicated risk to humans at current dietary exposure levels, the dose
rates they fed expressed on the basis of 70 kg adults (700-1400 yg/day)
are high enough to have caused Fanconi syndrome. Although laboratory
studies with rats and other animals have shown that anemia, enteropathy,
and teratogenesis (due to Cd-induced Zn or Cu deficiency in the fetus)
can result from ingested Cd, these are very unlikely with practical
diets or with crops fertilized with low Cd sludges.
A number of researchers and groups have attempted to clarify the
dose-effect and dose-response relationships for Cd (CEC, 1978; Friberg
et al., 1974; Kjellstrom and Nordberg, 1978; Ryan et al., 1982;
Tsuchiya, 1978). The first sign of renal tubular dysfunction (increased
excretion of Bg-microglobulin or retinol binding protein, a specific
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LOGAN AND CHANEY
proteinuria characteristic of Cd injury) is generally agreed to occur at
about 200 mg Cd/kg wet kidney cortex. Some research indicates that the
critical kidney cortex Cd level may be as high as 300 mg/kg (Roels
et al., 1981b; Ellis et al., 1981), but 200 mg/kg is the level generally
accepted for use in risk analysis. Individuals may vary about this
population estimate.
Kjellstrom and Nordberg (1978) developed a sophisticated
multicompartments! dose-effect model for Cd metabolism in humans: "This
present model predicted that a daily intake corresponding to 440 yg at
age 50 would give 200 mg Cd/kg of (wet) kidney cortex at age 45-50."
These results were obtained by assuming a high, constant Cd
concentration per unit calories, and that calorie (hence Cd) ingestion
varied with age in the manner of the average diet of the Swedish
population. The "best fit" equation calculated a 4.8% lifetime average
absorption of dietary Cd, 440 yg Cd/day at age 50, and a 12 year
biological half-life for Cd to achieve the 200 mg Cd/kg wet kidney
cortex at age 45-50.
Other researchers have used different ways to express Cd-exposure
information, thus complicating interpretation of results from these many
sources. In the U.S., the Food and Drug Administration (FDA) has
measured food Cd concentrations and average Cd ingestion (FDA, 1977).
Food consumption was based on USDA's 1965 dietary intake survey but
adjusted to a "balanced" diet; FDA, USDA, and EPA agreed to use a food
consumption model based on teenage males (highest food consuming group)
in a pesticide residue survey program, Thus, for the same food supply,
a mean food Cd ingestion of 39 yg/day from FDA corresponds to about
23 ug/day intake at age 50 in Kjellstrom and Nordberg's (1978) model.
Their model reflected 3430 kcal/day for Swedish teenage males vs.
2045 kcal/day for 50-year-old Swedish individuals (Fig. 4.32 and 4.34 in
Friberg et al., 1974). Thus, the critical 440 yg Cd/day ingestion rate
for 50-year-old individuals in Kjellstrom and Nordberg's (1978) model
corresponds to approximately 738 yg Cd/day ingestion in U.S. teenage
male diets. The present average exposure is only 5.2% of the critical
exposure (23 vs 440 or 39 vs 738).
Chaney (1983b) and Ryan et al. (1982) discuss difficulties in
interpreting dose-response relationships for dietary Cd. Individuals
vary widely in self-selected diet and dietary Cd (Yost et al., 1980), in
Cd absorption rate (Flanagan et al., 1978; McLellan et al., 1978), and
in sensitivity to absorbed Cd. These phenomena are generally assumed to
vary in a log-normal fashion in a population. Kjellstrom (1978)
extended the 440 yg/day model "critical" level to a population by
arbitrarily using a geometric standard deviation of 2.35 based on
studies of Cd in autopsy tissues (see Ryan et al., 1982 for details).
However, Kjellstrom's (1978) model would require greater than 100%
absorption of dietary Cd by the most sensitive individuals (see Figure 1
in Chaney, 1980). The highest Cd absorption rate observed for humans is
25% reported by Flanagan et al. (1978) for a woman with mild anemia; Fe
stress strongly increases Cd absorption. Several researchers (Chaney,
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Page 273
1980; Ryan et a!., 1982) argued that it was unreasonable to extrapolate
the 440 yg Cd/day "Average Human" model result to an assumed maximum
sensitivity group with greater lifetime percent absorption of Cd than
ever observed in humans. Further, individuals are unlikely to be in
this greatest risk group for their whole lifetime.
Thorough analysis of the Cd injury of Japanese farmers conducted
during the last decade appears now to support only a dietary threshold
type dose-response curve. For any individual to be injured, sufficient
Cd must have accumulated in the kidney to induce proteinuria. Although
individuals vary in retention of dietary Cd, and in kidney Cd associated
with initial low-molecular-weight proteinuria (LMW-proteinuria), much Cd
must be consumed to reach this condition. Food Cd must exceed some
level before the most sensitive individuals experience LMW-proteinuria.
The Japanese data indicate that, for individuals over 70 years of
age, incidence of LMW-proteinuria was not significantly increased until
rice Cd exceeded 0.40 mg/kg. For individuals 50-60 years of age,
incidence of LMW-proteinuria was not significantly increased until rice
Cd exceeded 0.60 mg/kg. Individuals are presumed to have eaten 300 g
rice/day; thus acceptable exposure was 300 x 0.4 = 120 yg Cd/day for
persons over 70 years old, and 300 x 0.6 = 180 yg Cd/day for 50-60 year
old's. The standard Japanese is considered to weigh 53 kg (Kjellstrom,
1978), while the standard Westerner is considered to weigh 70 kg.
Adjusting for this difference, the first significant observation of
LMW-proteinuria in U.S. citizens should require 238 yg Cd/day for a
50 year model, or 158 yg Cd/day for a 70 year model. These analyses
disregarded Cd exposure from smoking which would have increased daily
intake above that from rice. Thus, the log-normal extrapolation appears
inappropriate compared to the threshold model (Ryan et al., 1982).
Ryan et al. (1982) concluded that a 200 yg/day (150 yg/day after
protecting smokers) threshold model (based on average lifetime daily Cd
intake) of individuals was more appropriate for dose-response
considerations, as did the CEC (1978) workgroup. This value corresponds
to about 14,1% lifetime Cd absorption rate for the most sensitive
individuals 14.8(440/150)].
Cd bioavailability: Cadmium absorption by animals is strongly
influenced by other dietary factors (Fox, 1976, 1979; Fox et al., 1978,
1979; Jacobs etal., 1978a, 1978b, 1983; Flanagan et al., 1978;, Welch
et al., 1978; Welch and House, 1980; Kostlal et al., 1979; Cousins,
1979; Kobayashl, 1978; Washko and Cousins, 1977). Iron status of the
animal appears to be the most important control of percent absorption of
Cd and many individuals ingest low Fe during at least part of their
life. Zinc status of the animal and dietary Zn level is the next most
important factor, followed by dietary Ca. Protein and fiber in the diet
and age of animal also influence Cd retention. These factors should
allow a greater percent absorption rate for women than men. Women as a
group showed greater Cd absorption (Flanagan et al., 1978), and women's
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LOGAN AND CHANEY
kidney Cd exceeds men's in autopsy kidney studies, as did women's
susceptibility to excessive dietary Cd in Japan.
Dietary interactions can thus influence bioavailability of Cd.
Leafy and root vegetables which are enriched in Cd may also be a good
dietary supply of Zn, Fe, and Ca. Leafy vegetables have been shown to
provide bioavailable Fe and Zn (Welch et al., 1977, 1978; Van Campen and
Welch, 1980; Wien et al., 1975). Chaney (1980) suggested that leafy and
root vegetables grown on soils enriched in Cd from being fertilized by
low Cd, low Cd:Zn sewage sludges comprise a separate risk scenario. In
this case, consuming sufficient food Cd to pose a risk to individuals
susceptible because of poor nutrition would result in increased dietary
Fe, Zn, arid Ca, thereby shifting the individuals to a less susceptible
population group who do not suffer from poor nutrition.
Feeding studies have been conducted with sludge and with crops
grown on sludge-fertilized soil. Ingestion of sludge Cd has been
evaluated in ruminant and monogastric animals with most work done with
cattle. When sludges with high Cd and high Cd:Zn were fed, kidney Cd
was significantly increased (Kienholz, 1980; Baxter et al., 1980; 1982;
Hansen and Hinesly, 1979; Hinesly et al., 1976, 1979a; Edds et al.,
1980; Fitzgerald, 1980; Lisk et al., 1982; Johnson et al., 1981).
However, when sludges with lower Cd and low Cd:Zn were fed, kidney Cd
was not significantly increased (Decker et al., 1980; Kienholz et al.,
1979; Kienholz, 1980; Baxter et al., 1980; Bertrand et al., 1981; Edds
et al., 1980; Smith et al., 1979). Sludge Cd was less bioavailable to
swine than equal Cd added as CdCl2 (Osuna et al., 1979; Edds et al.,
1980). Food products of animals are unchanged in Cd except for liver
and kidney (e.g., Sharma et al., 1979). Kienholz (1980) noted that
dietary interactions could avoid even this impact of sludge Cd. Thus,
risk analysis for ingested sludge Cd requires evaluation of several
factors other than dietary Cd concentration.
As noted above, the Cd-injured Japanese farmers were deficient in
several nutrients (Ca, Zn). Rice was the source of nearly all the
increased dietary Cd. Although the soils contained both Cd and Zn (at
Cd:Zn about 1:100) from mining wastes, the rice was increased in Cd but
not Zn. Rice grain grown under flooded culture contained only 20-25 mg
Zn/kg while rice Cd rose from normal levels of 0.05 mg/kg to over
2 mg/kg (page 237 in Tsuchiya, 1978); polished rice is very low in Ca
and Zn.
Similarly, risk analyses for ingestion of Cd in foods grown on
Cd-enriched soils requires careful evaluation of factors other than Cd.
Far too little research has been conducted to characterize
bioavailability of food Cd. Further, very little of the completed
research conforms with the experimental designs which Fox et al. (1978,
1979) and Fox (1976) indicated were needed to allow interpretation of
data. Dietary Cd level should correspond to the range of nutritional
relevance to humans. Cadmium enriched foods should be fed in the state
ordinarily ingested by humans (e.g., fresh leafy vegetables).
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Nutritional status of the experimental diet should be adequate for all
known essential factors or varied as part of the experiment. The
feeding period should be of sufficient length to allow nutritional
status of animals to be under control of experimental diet for the bulk
of the experimental period. Several animal species should be studied.
Bioavailability of Cd in a food or a sludge-grown food can only be
determined experimentally.
The bioavailability of Cd may also be influenced by the chemical
species of Cd present in crops. Several studies have reported the
existence of an inducible protein which can bind Cd in plants (Bartolf
et al., 1980; Weigel and Jager, 1980; Wagner and Trotter, 1982;
Casterline and Barnett, 1982). Unfortunately, these studies used
phytotoxic levels of Cd in their research. It is possible that high
levels of Zn or other metals might also affect the chemical species of
Cd in edible plant portions. Thus, research is needed on potential
shifts in chemical species of Cd in sludge fertilized crops and its
effect on Cd bioavailability, if any.
Cd in tobacco: Tobacco is an especially high risk crop in terms
of potential for Cd effects on humans. Among all crops studied to date,
tobacco accumulates more Cd per unit soil Cd than any other (Chaney
et al., 1978a; Maclean, 1976; Davis and Carlton-Smith, 1980). In many
areas, tobacco is normally grown on strongly acid soils to prevent crop
loss from root diseases. This soil pH management leads to maximum Cd
uptake under normal crop production conditions. In contrast, most other
crops are best grown at pH 6.5 to 7. Tobacco is normally high in Cd
compared to leaves of other crop plants, and high leaf Cd levels in some
production areas are being studied (Frank et al., 1977; Westcott and
Spincer, 1974). When tobacco is grown on acidic sewage sludge-amended
soils, crop Cd levels can be increased from 1 to as high as 44 mg Cd/kg
in dry leaves (Chaney et al., 1978a) with only 1 mg/kg soil Cd.
Gutenmann et al. (1982) applied 19 kg sludge Cd/ha and found tobacco Cd
increased from 3.2 to 67.4 mg/kg.
Cadmium in tobacco 1s an important source of Cd for humans.
Individuals who smoke one pack of cigarettes per day have about 50%
higher Cd in kidney cortex than non-smokers (Lewis et al., 1972; Elinder
et al., 1976). About 15% (5-2531} of cigarette Cd enters the mainstream
smoke (Szadkowski et al., 1969; Menden et al., 1972; Westcott and
Spincer, 1974). Filters can remove much of this Cd and reduce Cd
exposure of smokers (Westcott and Spincer, 1974; Franzke et al., 1977).
Based on the potential of sludge-applied Cd to increase risk of chronic
kidney disease in smokers if sludge were applied to tobacco cropland,
EPA (1979a) regulated and discouraged this practice. Some tobacco
growing states have even prohibited sludge applications on land suited
for tobacco production.
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LOGAN AND CHANEY
Models for limits on Cd application: Several food crops are of
especial importance to evaluating Cd-risk for humans. While grains
supply much Cd to individuals in the general population {Braude et al.,
1975; Jelinek and Braude, 1978; Ryan et al., 1982), individuals are
extremely unlikely to grow a significant portion of their food grains.
Rather, individuals are likely to grow leafy and root vegetables, legume
vegetables, garden fruits, and potatoes. If the Cd:Zn ratio of an
acidic Cd-enriched garden soil is high, edible crop tissues of leafy,
root, and legume vegetables, garden fruits, and potatoes can be greatly
increased in Cd concentration with no injury to the crop and provide
excessive bioavailable Cd. If the Cd:Zn ratio of an acidic Cd-enriched
garden soil is low (< 0.01), these crops are not greatly increased in Cd
when Zn phytotoxicvEy limits crop yield, (see data for lettuce in
Table 5), and bioavailable Cd would be only slightly increased. The
difference in risk from low Cd:Zn and hilgh Cd:Zn gardens is due to:
1) Zn-phytotoxicity at low pH in the law Cd:Zn garden causing the
gardener to add limestone which reduces crop Cd or have little yield
(hence, reduced exposure), 2) interactions, between Cd and Zn in plant
uptake and translocation to edible plant tissues (Chaney et al., 1976;
Chaney and Hornick, 1978); and 3) interactions in the diet which
influence Cd bioavailability.
It is much more difficult to evaluate Cd bioavailability from foods
grown on waste-amended soils than from Cd-amended purified diets.
Freeze-dried lettuce and chard grown on acidic soils amended with
domestic sludge were fed at a high percentage of diet to mice or guinea
pigs (Chaney et al., 1978b, 1978c). Although dietary Cd was increased
by up to 5-fold by lettuce or chard grown on acidic, domestic
sludge-amended soil, kidney Cd was not increased. Bertrand et al.
(1980) found similar results for forage. In other studies with high Cd
and/or higher Cd:Zn sludges, feeding sludge-grown crops has caused
increased kidney Cd (Chaney et al., 1978b; Miller and Boswell, 1979;
Heffron et al., 1980; Lisk et al., 1982; Telford et al., 1982; Williams
et al., 1978; Hinesly et al., 1976, 1979).
A recent paper by Boyd et al. (1982) shows another difficulty of
assessing risk of sludge-applied Cd. They applied 8.6 kg Cd/ha in one
112 mt/ha application (violated 5 kg Cd/ha and 0.5 kg Cd/ha/yr limits of
EPA, 1979a). However, snapbean and squash showed small increases in
tissue Cd, and Cd in rat kideys was equal to that in the control, or
lower (Table 8). Sludge-fertilized cabbage and redbeets were six times
higher in Cd than control crops, yet kidney Cd was increased less than
two-fold. Thus, sludge Cd had little effect on kidney Cd when vegetable
crops were grown, even though Cd regulations (annual and cumulative Cd
for acid soils) and recommendations (sludge Cd < 25 mg/g and Cd/Zn <
0.015) were exceeded. Two other cabbage feeding studies failed to meeT
"Environmental Toxicology" standards (cabbage grown on 1.2 m deep pile
of high Cd sludge, and fed at 3035 of diet to rats or 45£ of diets to
sheep); reported kidney Cd increases are thus irrelevant to sludge risk
analysis (Haschek et al., 1979; Bablsh et al., 1979). Clearly, more
sludge-soil-plant-animal studies are needed to characterize the
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Table 8. Cadmium and zinc in edible crop tissue and kidney of rats fed four control and
sludge-fertilized crops for 84 days (Boyd et al. 1982).
Crop Analyses Kidney Analyses
Crop
Cd,
C*
mq/kq dr^
Zn,
C
mq/kq dry
S
Cd, mq/kq dry
C S
Zn,
C
mq/kq dry
S
Beans
0.1
0.1
30
34
3.4
1.1
89
90
Squash
0.2
0.3
15
54
4.9
3.8
100
86
Cabbage
0.2
1.3
17
93
7.1
9.7
80
103
Redbeets
0.5
3.2
27
125
5.4
12.6
83
95
* C and S denote control and sludged, respectively. Applied 112 dry rat/ha of sludge containing 77 mg
Cd/kg and 3477 mg Zn/kg, applying 8.6 kg Cd/ha.
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LOGAN AND CHANEY
bioavailability of Cd in crops grown on waste-amended soils. It seems
very likely that factors besides background soil pH, and annual and
cumulative Cd application will eventually have to be considered in
setting allowed Cd loadings on cropland (EPA, 1979a; Chaney et al.,
1980a).
Much of the potential risk from Cd in waste-amended soils has now
come under regulation in the U.S., although these regulations do not
have to be enforced until September, 1984. The highest risk case,
application of sludges to gardens as fertilizers or soil conditioners,
has not yet been regulated (Comptroller General, 1978; Chaney et al.,
1980b). Further, pretreatment of Cd-bearing industrial wastes,
segregation of waste streams, and avoidance of Cd use for non-critical
applications offer great opportunity to avoid all Cd health effects
(Dage et al., 1979; Gurnham et al., 1979).
In the process of developing Federal regulations for land
application of sewage sludge (EPA, 1979a), EPA prepared a "worst
practical case" scenario relating sludge-applied soil Cd to potential
for kidney dysfunction to protect the higher risk sensitive individuals
(EPA, 1979b). The worst case which may occur appears to be the "acid
garden" case. Although grain crops can absorb Cd, individuals in the
U.S. do not grow their own food grain on acidic, Cd-enriched soils.
Similarly, consumption of liver and kidney enriched in Cd from sludge
utilization is a minor source of dietary Cd. This approach protects
individuals with soils least able to keep Cd from reaching their foods.
Thus, the "acid garden" scenario was used. It presumed that 1) the
soil contains the fully allowed Cd application, 5 kg/ha; 2) the soil is
continuously acidic, about pH 5.5; 3) the gardener obtains 50% of his
annual supply of garden vegetables from the acidic, sludge-amended soil,
including potatoes, leafy, root, and legume vegetables, and garden
fruits; 4) the individual eats these amounts of garden vegetables for
50 years from the acidic sludge-amended garden; and 5) the individual is
part of the sensitive-to-cadmium portion of the population. Further,
EPA used a normal Cd ingestion value of 39 yg/day, a value selected from
the range of annual estimates (28-51 yg/day during 1970-1979) of daily
dietary intake of Cd obtained in FDA's Total Diet Studies. The 39 yg
Cd/day for the teenage diet model was subtracted from the 71 yg/day WHO-
FAO (1972) provisional daily Cd ingestion to obtain a maximum allowed
increase due to sludge use. The WHO-FAO tolerable intake is for
population average adult exposure. Fecal analysis indicates that U. S.
adults ingest about 20 yg/day (Kowal et al., 1979), and adjustment of
the teenage diet to adult diet gives a similar estimate of 23 yg/day.
Thus, this part of the EPA (1979a) rule offered another safety factor.
Based on new dietary consumption research findings, FDA has recently
revised the methods used to estimate consumption of contaminants in US
diets (Pennington, 1983). Individual foods are analyzed (to avoid
detection limit questions on food composites). Thus, dietary Cd
ingestion can be estimated for 8 age-sex groups rather than only teen-
age males.
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It appears now that several assumptions of EPA's "acid garden"
scenario may provide excessive protection at least for "Domestic"
sludges. First, individuals who grow 50% of their garden vegetables
have such a large time and work investment in their gardens that they
learn about the effects of acid soils on yield of vegetable crops, and
carefully manage soil pH at 6.5 to 7. Second, presuming that a low Cd,
low Cd:Zn ratio sludge supplied the soil Cd, and that soil pH declines
slowly due to fertilizer use, phytotoxicity in sensitive crops will
cause a "50£ gardener" to learn about soil pH management and interrupt
the necessary 50 year "acid garden" exposure. Third, vegetables supply
microelements which counteract Zn, Fe, and Ca deficiencies; these
deficiencies are the identified basis for sensitive individuals. Thus,
consumption of the vegetables which comprise the minimal Cd risk to
sensitive individuals in the EPA scenario (71 yg/day) may push them out
of the sensitive population. Recall that increased Cd in "domestic"
sludge-grown chard and lettuce did not increase kidney Cd (Chaney
et al., 1978b, 1978c). Alternatively, the presence of higher levels of
other elements may have simply changed Cd speciation in foods to a form
with lower bioavailability. In their discussion of Cd dose-response
models, Ryan et al., (1982) concluded that U.S. sensitive individuals
are protected at the 150 yg Cd/day level of exposure (150-20 =
130 yg/day vs 71-39 = 32 yg/day). Alternatively, the FAO-WHO 71 yg
Cd/day value for adult diets may need to be adjusted from adult diet to
teenage diet if the 39 yg/day result is to be used (=119 yg/day, with
119-39 = 80 yg/day increase tolerable in teenage diet model).
Further, the slope of the crop Cd vs soil Cd relationship varies
with sludge Cd concentration (Chaney et al., 1982); low Cd sludges give
appreciably lower slope (hence lower potential exposure at 5 kg Cd/ha
regulated cumulative maximum Cd). The slopes for crop uptake from low
Cd sludges are much lower than the slopes used in risk estimates (see
EPA, 1979b; Ryan et al., 1982). High rates of low Cd sludges had little
or no effect on Cd in major garden vegetable crops (Dowdy and Larson,
1975; Dowdy et al., 1978; Chaney et al., 1982; Harris et al., 1981).
Some scientists have expressed a concern that the safety factor for
dietary Cd is small (e.g. Jelinek and Braude, 1978). The review
presented here, and Ryan et al. (1982) indicate that the safety factor
is larger than previously believed. We believe that this new
information should be used to demonstrate the existence of a larger
safety factor when low Cd domestic sludges are utilized, rather than to
support higher limits for Cd application on cropland. It remains clear
that high Cd, high Cd/Zn sludges do not enjoy the Improved safety factor
shown for "Domestic" sludge. The larger safety factor should reduce
public fear of recommended quality sludges, since it provides greater
protection of sensitive individuals who select diets with higher than
average Cd content. As a result of these newer understandings, and in
response to concerns expressed by the food industry, the regulatory and
advisory agencies developed a policy statement on utilization of low Cd
sewage sludge on cropland for production of fruits and vegetables (EPA-
FDA-USDA, 1981).
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LOGAN AMD CHANEY
In summary, the "Soil-Plant Barrier" does not protect the food
chain from excessive Cd. Unregulated application of Cd-bearing wastes
can cause health effects in humans. Cadmium is not easily kept out of
food crops; conversion of treated land to gardens is a worst case
scenario upon which regulations to limit Cd applications were based
(EPA,, 1979a]. Recent research on gardens polluted with Cd by mining
wastes or smelter emissions support the view that gardens can provide
much Cd in locally grown foods to the family maintaining the garden for
many years (Davies and Ginnever, 1979; Chaney et al., 1980,
unpublished). Some aspects of the Cd-waste-soil-olant-animal food chain
are not well established, and research is needed to avoid unnecessarily
restrictive limits in the regulations. Recent research indicates a
substantial difference in potential risk from Cd in high Cd sludges vs.
low Cd, low Cd/Zn sludges, and that for the "Domestic" sludge case, the
safety factor for dietary Cd is much larger than previously believed.
The larger safety factor conclusion rests on: 1) Sensitive individuals
are protected at 150-200 yg Cd/day; 2) adult U.S. diets contain about
20 ug Cd/day; 3) Zn phytotoxicity can sharply limit maximum achievable
crop Cd levels; 4) Cd in crops grown on soils amended with low Cd, low
Cd/Zn sludges has very low bioavailablity; and 5) crop uptake of Cd per
unit soil Cd is much lower for low Cd sludges.
Potential Effects of Other Sludge-borne Elements on the Food-chain
A few elements besides Cd have been of high interest or concern
regarding risks from sludge utilization, and are considered briefly
here. Other elements are not discussed here because they are low in
sludges (As) or high levels are tolerated by animals (Cr3+, Al, Sn).
The discussion of "Soil-Plant Barrier" above indicates that only a few
elements merit the concerns expressed in 1973. Further, the special low
risk case resulting from utilization of recommended quality sludges
(Chaney, 1980) substantially alters the potential for risk from many
elements in sludge.
Cobalt: Excessive dietary Co can cause tonicity in ruminant
animals, while monogastric animals are more tolerant (NRC, 1980b).
Diets with over 10 mg Co/kg (as soluble salts) have injured cattle and
sheep.
Unfortunately, plants tolerate higher levels of foliar Co than
ruminants tolerate in their diets. Most plants show symptoms or
substantially reduced yield at 50-100 mg Co/kg 1n foliage (Chaney,
1983b). However, no feeding studies have been conducted with
plant-absorbed Co. Sludges are normally low in Co (Sterrett and Lester,
1981), and there 1s little reason for concern about sludge Co unless the
sludge 1s high in Co.
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Copper: Phytotoxicity due to excessive soil Cu occurs in most
plants at 25-40 mg Cu/kg (Walsh et al., 1972). Copper toxicity in
sensitive sheep and cattle occurs at 25-100 mg Cu/kg iri the diet (as
soluble Cu salts). However, increased dietary Zn, Cd, Fe, or Mo would
counteract added Cu (Bremner, 1979, 1981).
Crops have to be grown on acidic soils quite high in sludge to
contain 25-40 mg Cu/kg. For the "Domestic" sludge case, these plants
would have increased Zn which would prevent any toxicity due to the
small possible increase in plant Cu. Similarly, ingested sludge and
high Cu manures have caused no Cu toxicity problems even though dietary
Cu reached 50 mg/kg (Bremner, 1981; Poole, 1981).
Fluorine: Fluorine is normally low in plants because F is
precipitated and/or sorbed strongly in soils. Sludges are normally low
in F; 80% of sludges surveyed contained lower than 450 mg/kg. However,
a few sludges are very high in F, with the highest reported 3.35% F
(Chaney, 1983b). Davis (1980) found that this high F sludge could
temporarily cause increased F uptake by ryegrass. However, others have
not found increased F in sludge fertilized plants.
Direct ingestion of sludge circumvents the "Soil-Plant Barrier".
Kienholz et al. (1979) found increased bone F in cattle fed sludge with
normal F concentration.
Iron: Tron is normally restricted to 40-300 mg/kg dry foliage by
plant and soil properties. Fertilizing with sludges, even sludges very
rich in Fe, does not increase Fe appreciably above normal levels. Soil
on contaminated forages often provides more total Fe than forage crops.
Although animals tolerate increased ferric iron, 1000 mg/kg ferrous
Fe added to forage diets reduced liver Cu in sheep and cattle. On low
Cu diets, Fe can induce Cu-deficiency (NRC, 1980b). Fe-toxicity was
observed in cattle grazing tall fescue pastures sprayed with a digested
sludge containing 11% Fe (Decker et al., 1980). Sludges lower in Fe and
sludge composts (ferric Fe) did not cause Fe-toxicity. When digested
sludges are surface-applied to pastures, sludge Fe concentration should
be analyzed. Sludges over about 4% Fe have caused Fe-induced
Cu-deficiency; these observations were probably related to the crop,
method of grazing, and low sludge Cu concentration (Chaney, 1983b).
Lead: Sludge applied Pb has been found to not increase plant Pb
unless sludge Pb concentration is extremely high (Chaney, 1983a, b).
Often, sludge application reduced plant Pb even though soil Pb
increased. This has been observed in all soil types, and for all crops
studied — grains, fruits, tuber and edible root, and even leafy
vegetables. The reduced uptake may result from sludge-increased soil Pb
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LOGAN AND CHANEY
sorption capacity, or phosphate which reduced Pb translocation within
plants.
Although sludge-applied Pb, mixed in the soil, appears to comprise
no potential risk in any scenarios presently used by regulatory
agencies, new information is now available on risk to children ingesting
moderately high levels of Pb. Classic Pb poisoning of children can
cause an encephalitis which often leads to severe retardation.
Ingestion of Pb-paint contaminated soils has caused excessive blood Pb
in children with pica for soil. Recently, a neurobehavioral impairment
(lower 10 and school achievement, and problem classroom behavior) was
found to increase with Pb concentration in deciduous teeth (Needleman et
al., 1979, 1980; Winneke et a 1., 1981). Thus, higher than normal Pb
ingestion may be undesirable in children. Because some sludges may be
surface applied as lawn fertilizers or mulches, their Pb concentration
and its bioavailability may be important. Sludge Fe, P, Ca, and organic
matter would reduce Pb absorption. It appears that "Domestic" sludges
comprise no risk to livestock, or to human adults through plant uptake
or soil ingestion (Chaney, 1983b). Research is needed to determine
whether ingestion of small amounts of sludges low in Pb adds to Pb risk
of infants and children.
Mercury: Mercury is noted for the food-chain poisoning resulting
from methyl mercury accumulation by aquatic organisms. However, the
terrestrial ecosystem is quite different than the aquatic. Mercury is
bound so strongly in soil and in plant fibrous roots that uptake by
plants is not the limiting factor. Some volatilization of Hg vapor can
occur when soils are rich in Hg.
Sludge Hg appears to be important in two sludge utilization cases.
First, direct ingestion of sludge rich in Hg will increase liver Hg
(Kienholz, 1980). Second, if sludges are used in the composts for
mushroom production, mushrooms can exceed 0.5 mg Hg/kg fresh weight, the
level regulated in fish. Domsch et al. (1976) found excessive Hg in
mushrooms grown on refuse-sludge compost. Frank et al. (1974) found
even some horse manure is high enough in Hg to cause excessive mushroom
Hg. Mushroom species vary widely in Hg and methyl-Hg accumulation
(Stijve and Roschnik, 1974).
In research on production of mushrooms on composts including
composted municipal refuse (Schisler and Grable, 1976), the excessive Hg
accumulation observed by Domsch et al. (1976) was confirmed. Further,
the Hg availability to mushrooms from refuse compost appears to be
greater than that in traditional mushroom composts (L. C. Schisler,
Pennsylvania State University, personal communication). Thus, sludge
compost should not be used in mushroom production until research shows
that Hg levels in the mushrooms will not exceed levels regulated by FDA.
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Molybdenum: Excessive plant Mo can poison ruminant animals, but
not monogastric animals under an enriched garden scenario. The ingested
molybdate is converted to tetrathio-molybdate which can form an
insoluble and unavailable compound with Cu. This causes a severe
Mo-induced Cu-deficiency, a practical problem in sheep and cattle in
many nations. Plants tolerate quite high levels of Mo without causing
symptoms or substantial yield reduction. If forages contain 5-10 mg
Mo/kg, such that the Cu:Mo ratio falls below two, induced Cu deficiency
can occur. In contrast to metal cations, anionic molybdate uptake by
plants is increased as soil pH is raised. Most excessive plant Mo
problems occur on calcareous soils.
Sewage sludges are very seldom high in Mo. Williams and Gogna
(1981) reported Mo uptake by white clover and ryegrass grown on alkaline
soil amended with sludges low {5 mg/kg) or high {103 mg/kg) in Mo, or
with equal amount of molybdate. The high Mo sludge caused high Mo
uptake by white clover; sludge Mo availability was approximately equal
to that of molybdate. The low Mo sludge caused no appreciable change in
plant Mo. Davis (1981b) reported Mo and Cu uptake by forage crops on
soil from a sludge farm (515 mg Cu/kg and 6.0 mg Mo/kg). Clovers and
brassica forages had unfavorable Cu:Mo ratios. He also reported the
expected soil pH effect on Mo uptake from soils amended with a Mo-rich
sludge. Based on these findings, sludges to be applied to neutral pH or
calcareous soils for forage production should be analyzed for Mo to
protect ruminant animals.
Nickel: Nickel represents elements for which phytotoxicity
completely protects the food chain. Ruminants tolerate at least 50 mg
Ni/kg (NRC, 1980b), while forage crops show visual symptoms of toxicity
at 50-100 mg/kg. Cattle suffered no effects from forage diets with
250 mg Ni/kg as NiCO3, while soluble Ni salts caused the animals to
reduce food consumption. Alexander et al. (1979) reported no toxicity
or Ni bioaccumulation in meadow voles fed soybean grain containing 30 mg
Ni/kg, about the highest level possible without severe yield reduction.
Selenium: Although plant absorbed Se has poisoned livestock in
several areas of the Western U.S. (Kubota and Allaway, 1972),
sludge-borne Se has not been shown to cause excessive plant or animal Se
(Kienholz, 1980). Fly ash can cause excessive Se uptake if poorly
disposed, or correct Se deficiency in livestock if used wisely
(Gutenmann et al., 1979). Annual monitoring of sludge for Se can
identify sludges with potentially excessive Se. Uptake of Se is favored
on alkaline soils, or soils where Se-accumulator crops leave residues of
seleno-amino acids.
Zinc: Excessive dietary Zn (300-1000 mg/kg) can injure ruminant
animals by inducing Cu-deficiency (NRC, 1980b). Sheep with low dietary
Cu were injured when dietary Zn exceeded 300 mg/g (Campbell and Mills,
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LOGAN AND CHANEY
1979). Smelter Zn pollution injures horses, which are sensitive to
excess. Gunson et al. (1982) reported erosion of cartilage in joints, a
manifestation of severe Cu-deficiency (Bremner and Campbell, 1980).
However, Zn causes appreciable and/or visible injury to plants when
foliar Zn is 500 mg/kg (see plant uptake section). Sludge risk
scenarios include strongly acid soils. Although high Zn sludges may be
equivalent to Zn salts in risk scenarios, "Domestic" sludges apply Cu
and other nutrients. Acid soil-grown forage crops would not be low in
Cu or Fe; further, forage crops are not Zn-accumulators. Thus,
livestock are protected from excess crop Zn problems when the Zn is
supplied by "Domestic" sludges. Sludge ingestion studies have found no
Zn toxicity problems, likely due to the rich Cu and Fe supply in sludge.
It is conceivable that ingestion of high Zn, low Cu sludges could lead
to induced Cu deficiency in ruminants.
The "acid garden" scenario for Cd could be applied to Zn. Because
leafy vegetables comprise such a small part of human diets, and because
Zn is much lower in seeds, fruits, and edible roots than leaves,
gardeners would be protected. Actually, many humans consume low dietary
Zn, and increased crop Zn could be beneficial.
REGULATORY STRATEGIES FOR METAL CONTROL
Metals to be Regulated
The USEPA (EPA, 1979a) has only regulated the application of
cadmium to land in sewage sludge and other wastes. Other metals which
have been identified as potentially phytotoxic or food-chain
contaminants (Cd, Pb, Hg, As, Se, Zn, Cu, Ni, Mo) have not been
regulated at the Federal level. Many states have considered Pb, Zn, Cu,
Ni, Hg, and even Cr. Cadmium has received regulatory attention because
of the relative ease with which it is taken up by crops, and because of
the relatively small difference between current dietary Cd intake and
the presumed safe intake level (Ryan et al., 1982).
Although there appears to be little present justification for
general regulation of metals other than Zn, Cu, Ni and Pb, Chaney
(1983b) lists several which should require attention in the form of
further research or sludge monitoring programs. These are sludge borne
metals which can escape the "Soil-Plant Barrier" (Se, Mo) or are added
to soils in industrial wastes (Be, Co), or may cause animal health
problems when sludge is ingested (above metals plus F and As).
Regulations may be required in some instances to prevent direct
ingestion of sludge or soil which has received sludge. Many states
regulate Zn, Cu, and Ni application to reduce risk of phytotoxicity.
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Metals
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Metal Levels in Sludges
One regulatory approach to the control of potential problems from
metals in sludges is to restrict the land application of sludges which
have metal concentrations in excess of prescribed levels. This approach
is relatively easy to monitor, and has the advantage of encouraging
sludge pretreatment by individual treatment plants. The levels of
individual metals that constitute a "safe" sludge is, and has been, a
topic of considerable debate. Chaney (1973) suggested that a sludge
that would be appropriate for land application should not exceed the
following metal concentrations:
Chaney (1973) Chaney & Giordano (1977)
mg/kg dry weight
Zn 2000 2500
Pb 1000 1000
Cu 800 1000
Ni 100 200
B 100
Hg 15 10
Cd 0.5% of Zn 25 (1.5% of Cd)
Chaney felt that these levels were reasonably attainable. Note that, at
0.5% of the 2000 mg/kg maximum Zn concentration, the maximum Cd content
would be 10 mg/kg. Chaney and Giordano (1977) subsequently suggested
maximum levels of metals in domestic sludge (shown above).
Doty et al. (1978) presented the following recommended maximum
concentrations for Pennsylvania sludges which they attribute to Baker
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LOGAN AND CHANEY
and Chaney {no reference given), and which are designed to allow safe
annual sludge applications at a rate of 22.4 mt/ha:
Although these are suggested maximum concentrations, Pennsylvania
does not regulate metal levels in sludges. Japan regulates maximum
sludge Cd, Hg, and As levels at 5, 2, and 50 mg/kg (Ishikawa and Dodo,
1982). The ranges of maximum allowable concentrations in European and
Canadian sludges for As, Cd, Cr, Cu, Hg, Mo, Ni, Pb, Se and Zn are 10-
75, 10-40, 200-1,200, 500-3,000, 5-25, 20-40, 100-500, 300-2,000, 14-40
and 1,850-10,000 mg/kg, respectively (M. D. Webber, Dept. of
Environment, Burlington, Ontario, personal communication).
At the present time, metal levels in sludges are not regulated by
USEPA except that sludges which contain < 2 mg Cd/kg dry weight are
exempt from current regulations on pH control. Many states (e.g. PA,
MD, VA, NY, CN) regulate maximum sludge metal concentrations.
Early in 1980, USEPA released in pre-proposal draft form rules that
would constitute a comprehensive federal sludge management policy
(Newkumet, 1980). The approach proposed by USEPA was to establish
maximum concentrations of cadmium and lead in sludge for various uses.
Sludge fertilizers for unrestricted use would have a fixed nitrogen to
cadmium ratio which would limit increases in soil Cd over a 25-year
period to 0.5-2.5 mg/kg. A restricted use category for sludge
fertilizers (non-food chain uses) would allow a lower N:Cd ratio.
Similar ratios of N:Pb would limit Pb accumulation in the top one
centimeter of soil over a 25-year period to 250-1000 mg/kg. Sludge
products to be used as soil conditioners for unrestricted use could
contain 2.5-10 mg Cd/kg and 150-1000 mg Pb/kg if the material also had a
Cd:Zn ratio < 1.5% and contained at least 10% CaC03 equivalent by
weight. Restricted soil conditioning sludge products could have
10-25 mg Cd/kg and 250-1000 mg Pb/kg.
These proposals have generated considerable discussion since they
were first proposed. Although EPA has revised their draft in light of
newer information, the agency has not proposed them for public comment.
This approach offers significant incentives to treatment plants to
improve the quality of their sludges, and opens the door to more
widespread sale and distribution of sludge products. On the other hand,
mg/kg dry weight
Cd
Cu
Cr
Pb
Hg
Ni
Zn
50
1000
1000
1000
10
200
2000
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Metals
Page 287
there is some concern about the ability of plants in large cities to
reduce metal levels to background levels to the point where they can
meet the proposed concentrations. In addition, more recent information
on the dietary intake of Cd (Ryan et al., 1982) and the risks associated
with other metals should be evaluated before establishing final rules on
metal concentrations in sludge products.
Annual and/or Cumulative Metal Loadings
The current regulatory approach in the United States and many other
countries is to restrict the cumulative and annual application of metal
to soil, in the U.S., Cd is the only metal that is currently regulated,
but it is likely that the same approach would be appropriate for other
potentially toxic metals which accumulate in soil. The W-124 (formerly
NC-118) Regional Research Committee (EPA, 1980) reviewed the development
of guidelines for metal loadings as follows:
1. Chumbley (1971) was one of the first to propose limiting metal
accumulations in soil. He proposed a maximum accumulation of 560
kg/ha of Zn equivalent, where Zn equivalent = Zn + 2 Cu + 8 Ni.
The coefficients of the equation reflect the relative
phytotoxicities of the three metals.
2. Leeper (1972) suggested combining the Zn equivalent approach with
CEC and proposed a maximum Zn equivalent accumulation of 5% of the
CEC.
3. In 1974, USEPA published a draft technical bulletin which proposed
to increase the allowable Zn equivalent to 10% of CEC and decrease
the relative phytotoxicity of Ni with respect to Zn from 8 to 4.
In addition, they proposed that the Cd:Zn ratio not exceed 1:100.
The Cd:Zn ratio had been proposed by Chaney (1973) as a means of
preventing excessive Cd uptake since Zn would become phytotoxic
before Cd had accumulated to excessive levels.
4. In the same year, an NC-118 subcommittee met to review the proposed
USEPA guidelines and suggested that: (1) the Zn equivalent
approach implied more knowledge about the relative phytotoxicities
of Zn, Cu and Ni than actually existed; (2) Cd and Pb additions to
soil should also be controlled due to human health concerns; (3)
the annual rate of Cd application should not exceed 2.24 kg/ha (2
pounds/acre) (based on field data from Wisconsin which showed
slight increases in grain Cd at 4.48 kg/ha annual rate but not at
2.24 kg/ha); (4) the cumulative Cd application should not exceed
11.2 kg/ha. This was based on the notion that, after five years at
the maximum annual application rate of 2.24 kg/ha, the accumulation
would still be within the range encountered for natural mineral
soils (Allaway, 1968). It was felt that, after five years, there
would be further research data to give a more accurate value; (5)
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LOGAN AND CHANEY
allowable accumulations of Pb, Ni, Zn and Cu should reflect current
knowledge of their relative phytotoxicities. Based on these
criteria, NC-118 suggested the following maximum accumulations for
medium textured soils in the North Central region of the U.S.,
assuming that soil pH would be 6.5:
lbs/ac
kg/ha
Pb
1000
1120
Zn
500
560
Cu
250
280
Ni
100
112
Cd
10
11.2
These were intended to be 1ifetime accumulations.
5. In 1976, the NC-118 Committee, at the request of USDA, modified
their guidelines to distinguish between fine, medium and coarse
textured soils (Table 2). In addition, the allowable Ni addition
was increased to the same level as Cu. These guidelines or
regulations have been adopted by many state regulatory agencies.
6. In 1978, EPA reprinted the North Central Research Publication No.
235 which included the revised Ni levels (Knezek and Miller, 1978).
7. In 1979 (EPA, 1979a) U5EPA published final, interim final and
proposed regulations for land application of sewage sludges. Cd
was the only metal addressed, and the section of the rules (interim
final) that apply to metals can be summarized as follows:
1) The annual Cd application will not exceed 0.5 kg/ha for
tobacco, leafy vegetables or root crops grown for human
consumption.
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Metals
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2) For other food-chain crops, the annual Cd application rate will
not exceed:
kg/ha
Present to June 30, 1984 2.0
July 1, 1984 to Dec. 31, 1986 1.25
After Jan. 1, 1987 0.5
3) The cumulative Cd application to soils used for the production
of food-chain crops will not exceed those given in Table 9.
4) No maximum annual and cumulative Cd applications are specified,
but the only food-chain crop produced is animal feed, the pH of
the soil/sludge mixture is 6.5 wherever crops are grown, there
is a facility plan which demonstrates how the animal feed will
be used to preclude its ingestion by humans, and future
property owners are notified that the land has received Cd
applications and should not be used for food-chain crops.
(This "dedicated site" approach will be discussed later).
The phased reduction of the annual Cd application rate of 2.0 kg/ha
originally proposed by NC-118 in 1974 (actually 2.0 pounds/acre) was
justified by USEPA as being necessary for the long-term protection of
the nation's food-chain, and the phased-in reductions would provide the
necessary lead time for treatment plants to develop their pretreatment
programs. The CAST Report (1980) concluded that, while there was a
clear positive relationship between the total amount of Cd applied and
Cd uptake at a given pH, there were no clear-cut differences betwen
annual versus cumulative additions. This follows from previous
discussion in this paper which indicated that previous Cd additions did
not rapidly revert to less available forms. There appears, then, to be
little justification for required annual Cd application rates < 2.0
kg/ha as long as the cumulative provisions are followed. However, lower
Cd sludges allow much greater sludge benefit to be applied at the
desired cumulative Cd limit. British scientists conclude that the
original Zn (equivalent) limitations were for extractable metals. Using
extractable:total ratios for the EDTA and acetic acid extracts used in
the UK, Williams (1982) indicated that British total soil metal
restrictions would be similar to the NC-118/USDA values.
Soil pH and CEC
Soil pH: Chumbley (1971) suggested that soil pH should be > 6.5
to reduce phytotoxicity of Zn, Cu and Ni. In 1974, NC-118 (USEPA, T980)
-------
~D
03
(D
CD
Table 9. Maximum cumulative Cd applications to soil (EPA, 1979a).
Maximum Cumulative Application (kg/ha)
CEC Background Background* Background
(meq/100 g) >pH 6.5 pH <6.5 pH <6.5
<5 5 5 5
5-15 10 10 5
>15 20 20 5
*Soil/sludge pH is 6.5 whenever food-chain crops are grown.
o
o
>
>
z
o
o
X
>
z
m
<
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Metals
Page 291
proposed that soil pH should be 6.5 at the time of sludge application
and maintained at > 6.2 after application. The 1976 CAST Report
recommended that soiTpH be maintained at 6.5.
In the current USEPA regulations {EPA, 1979a), the soi1/sludqe
mixture pH at the time of application must be _> 6.5 wherever food-chain
crops are grown. The regulations provide for lower cumulative Cd limits
(5 kg/ha) for soils whose background pH is < 6.5 and the soil/sludge pH
will not be 6.5 at some time after sludge application. This provision
is particularly important for those soils, primarily in the unglaciated
regions of the eastern, southeastern and northwestern U.S., that have
high lime requirements to reach pH 6.5.
Soil pH is the factor which has most consistently been shown (CAST,
1980) to affect Cd uptake of crops at a given level of Cd in the soil.
Soil acidity is regularly neutralized by liming in normal farming
operations, and pH 6.5 is close to the optimum for most crops and for
those soil processes which lead to improved crop growth. A few crops
are grown in strongly acidic soils (< 5.5) to prevent plant diseases
(some potato and tobacco cultivars).
CEC: The current USEPA regulations (EPA, 1979a) on cumulative Cd
additions distinguish between these CEC classes: < 5, 5-15 and > 15
meq/100 g soil. The W-124 Regional Research Committee (EPA, 1980) and
the 1980 CAST Committee (many of the W-124 members also served on the
CAST Committee) reviewed the existing data on the effects of CEC on Cd
uptake by plants and concluded that it was difficult to establish a
direct link between CEC and metal uptake because most studies were
confounded by pH and soil organic matter content. The Committees felt,
however, that CEC reflected a number of the soil properties which result
in metal retention and decreased plant uptake. In addition, CEC is a
routinely measured soil parameter and familiar to agriculturists.
Several problems were identified, however, with the use of CEC to
regulate Cd accumulation by crops: (1) on calcareous soils, Cd uptake
appears to be insensitive to changes in CEC, (2) effects of CEC on
uptake of other metals (e.g. Ni, Cu, Zn) may not hold for Cd, and (3)
the CEC relationship may be most valid for soils with a mixture of
organic matter, aluminosilicate clay minerals and Fe, A1 and Mn oxides,
but may not hold for soils dominated by any one of these constituents.
Future research should concentrate on the effects of soil minerals,
organic matter and pH on metal uptake and regulations should be refined
to reflect advances, as they occur, in our knowledge of the soil-metal
system.
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l-OGAN AND CHANEY
Sludge Characteristics
The regulatory approach used in the U.S. and many other countries
is to restrict metal applications to soil regardless of sludge
characteristics and sludge metal bioavailability. But recent work
(Corey et al., 1981) would indicate that the bioavailability of a metal
can vary depending on the chemistry of the sludge, and that, in some
cases, the metal-binding capacity of the sludge may be as, or more,
important than soil characteristics in determining metal uptake by
crops.
Research should focus on developing extraction procedures,
adsorption isotherms or other methods of determining the metal retention
capacity of different sludges which might, in the future, provide the
means to regulate sludge-metal additions to soil on the basis of sludge
as well as soil characteristics.
Background Metal Levels in Soils
Extensive information on background levels of metals in
uncontaminated soils has been developed in recent years (Allaway, 1968;
Page, 1974; Baker and Chesnin 1976; Pierce et al., 1982; Logan and
Miller, 1983). A survey of metal levels of uncontaminated soils in the
U.S. is presently being conducted by the Soil Conservation Service
(USDA-USEPA-USFDA cooperative study). These data will provide a basis
for comparison with soil tests from sites which are known to have
received, or are suspected of having received metal additions in the
past. As land application of sludges and other wastes which contain
metals increases, the need to monitor prior applications also increases,
especially if there has been inadequate documentaion of previous metal
additions. At the present time, most of the available data is on total
metal content of soil, and research indicates (CAST, 1980) that total
metal content of soil gives reasonable correlations with metal uptake by
crops when other factors, such as pH, are constant. In the future,
however, new soil test procedures may be sufficiently accurate to
measure available metal levels in soils, and provide a better indication
of metal uptake than total metal content of soil.
Food-chain Versus Non Food-chain Plants
The current USEPA regulations are designed to prevent excessive
uptake of metals by food-chain crops. These include crops ingested
directly by humans such as fruits, vegetables (and includes tobacco) and
grains, as well as crops which are primarily fed through livestock.
Land used to grow tobacco, leafy vegetables and root crops grown for
human consumption (EPA, 1979a) can receive no more than 0.5 kg/ha/yr
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compared to the phased reduction of the annual rate for other crops from
2 down to 0.5 kg/ha by 1987. The cumulative metal accumulations are the
same for all food-chain crops, however, based on the acidic garden
scenario. While there are no restrictions on the accumulation of metals
in soil for growth of non food-chain species, there is an implicit
understanding in the regulations that prior accumulations of metal while
non food-chain species were grown would apply to food-chain crops if
there was a planned land use change to crop production.
There does not appear to be any new research since the promulgation
of the 1979 regulations that would indicate that they are ineffective in
controlling excessive Cd uptake. Of greater concern, is the lack of
monitoring of small users of sludge products (the home gardener) who is
likely unaware of the metals content of the product he is using and of
the health risks associated with excessive metal ingestion. This
problem was considered by USEPA (Newkumet, 1980) in their proposed
regulations for the sale and distribution of sludge products, and it
appears that this is the only manageable approach to controlling the
commercial dissemination of sludge-borne metals into the human
environment.
FDA "Safe" Limits
An alternative method of controlling metal uptake by the food-chain
is to establish maximum concentrations of metals in crops and livestock
that would be "safe." Chaney (1973) in his Conference paper raised the
possibility of establishing permissible Cd contents of foods in the
marketplace. The difficulties of doing this, however, are many. A
"safe" limit can only be established for a particular crop or food in
terms of its contribution to the total diet, the transmission of the
metal from the crop or food into humans, and the existing and maximum
allowable metal burden in the diet (based on full toxicological
understanding). The Food and Drug Administration (FDA) has not been
able to establish "safe" limits in crops and foods even for a single
metal, cadmium, which has received enormous attention in recent years
(Ryan et al., 1982). FDA presently has limits on Hg in fish and Pb in
canned milk and baby formulas.
Even if the dietary scenarios can be established, setting a metal
concentration limit in crops is difficult. Crops differ greatly in
their uptake of metals, translocation of the metals from roots to
shoots, and in relative transport of metals into fruits, tubers, and
grains (Chaney and Hornick, 1978; Chaney, 1983b). There are also
significant differences among cultivars of the same crop species {CAST,
1980).
Using the "safe" limit approach would also entail extensive crop
monitoring, and it is not clear at this time how a nationwide monitoring
program would be run or enforced or could be afforded. Interpretation
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LOGAN AND CHANEY
of a crop monitoring program will require some knowledge of the
background levels of metals in major crops. Presently, USDA-USEPA-FDA
are conducting a nationwide survey of metals in crops grown on
uncontaminated soils. The complete data will not be available for
another year or so, but some of the preliminary results have been
reported for wheat (Meyer et al., 1982). These results will be
invaluable in determining the variability in metal content of crops, and
may help to determine if the "safe" level approach is a viable
regulatory alternative.
Intensive (dedicated site) Versus Extensive (low application rate)
Strategies
The 1979 USEPA regulations provide for two approaches to land
application of sewage sludges (EPA, 1979a). The first approach controls
the annual and cumulative Cd additions to cropland and is designed to
regulate sludge applications at rates which allow for efficient crop
utilization of sludge nitrogen. This is usually < 15 dry mt/ha. This
extensive approach will result in a slow accumulation of metals on a
significant portion of agricultural land in the U.S. (Logan, 1983). As
reviewed in this paper, these levels may cause no practical change in Cd
in crops, at least for low Cd sludges (Chaney et al. 1983b). At crop
utilization rates, 0-5-40% of the available cropland in a state may be
required for land disposal of all POTVI digested sludges (USDA, 1978).
Critics of this approach will argue that it is potentially dangerous to
allow even low level contamination of such a large percentage of our
food-producing resource. On the other hand, increases in our knowledge
of food-chain effects of specific metals will hopefully keep pace with
the slow rate of metal addition to land with this approach. This
conclusion should be tempered, however, by the realization that chronic
levels of toxic metals in the human diet may take decades to exhibit
recognizable disease symptoms.
The second approach proposed by USEPA (EPA, 1979a) involved higher
applications of sludges to land at "closely controlled facilities."
This would permit greater metal additions than in the previous approach,
but management would control the disposition of food-chain crops and
would monitor surface and groundwater to prevent their contamination.
This approach is currently used, to various degrees, by many POTW's
(Forster et al., 1981), although, in many cases, there is inadequate
monitoring of crops, soil and water. This "dedicated site" approach is
favored by those who feel that contamination under controlled conditions
of a small part of our food-producing soil resource 1s less of a long-
term risk than a strategy of more extensive landspreading (Logan, 1983).
Regardless of the relative merits of these two approaches, it is
difficult in practice to define "dedicated site" management systems.
Forster et al. (1981) surveyed Ohio POTW's and found that several had
been spreading sludge on the same land for many years. In some cases
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this was POTW-owned land, but in other instances neighboring farmland
was used. There was little indication from the survey that the 1979
USEPA regulations for "dedicated sites" was being followed.
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LOGAN AND CHANEY
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QUESTIONS AND COMMENTS FROM THE FLOOR:
George L. Braude, FDA, Washington, DC: Where risks are not amenable
to precise definition (such as for cadmium), we should err on the aide of
caution. EPA suet spent 33 million to buy a toon and correct a mistake.
SO year8 from now, can we taxpayers be sure not to have to buy metal con-
taminated land - ae new information is developed about plant uptake,
toxicology, etc.?
Terry J. Logan: Firstly, there are significant differences between
dioxin contamination, the toxic compound Involved in your example, and
heavy metals, such as cadmium. We know a lot more about the health
effects of cadmium and Its transmission through various pathways than we
do about the toxic organics. Secondly, we are looking at chronic, and
not acute, toxicity with cadmium when we consider health risks. And
thirdly, the federal regulations on cadmium accumulation in the food
chain are viewed by many as being conservative. I do not foresee any new
information which could radically change our understanding of health
risks from cadmium.
James 0. Evans, USDA Forest Service, Washington, DC: Differences in
the fate of metals in sludge when applied to land surface versus being
incorporated in the soil itself have been Dell established by the speaker
and others. Perhaps, our chief concern on a short-term basis should be
with the metals in sludge on soil, whereas on a long-term basis our chief
interest might be with the soil organic fraction and the soil itself
assuming that sludge assimilation eventually occurs. My question ist
approximately how long might it be before this assimilation occurs?
Terry J. Logan: We have Indicated in our paper that sludge metal-
binding capacity may be important in determining metal bioavailability
when sludges are land-applied. Although sufficient long-term field stu-
dies do not exist to answer your question, the available evidence indica-
tes that there is no drastic change (increase or decrease) In bioavail-
ability of metals applied to soil in sludges. This could mean that the
sludge-metal solid phases are sufficiently stable in soil to prevent
significant change in bioavailability, or that the bioavailabilities of
sludge-metal forms are similar to metal forms 1n soil.
Frank M. D'ltri, Michigan State University: Little mention has been
made with respect to the role of redox potential in determining the spe-
aiation of heavy metals in wastewater, digestor sludges and sludges
applied to the land. For example, under reducing conditions, methylated
tin compounds will undergo transmethylation reaction with inorganic mer-
cury to produce methylmercury.
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Terry J. Logan: There fs always the possibility of forming various
reduced species of metals in wastewater and sludges, particularly anaero-
bically digested sludges. However, the soil environment is almost always
aerobic, especially in the long term, and reduced metal species are
quickly oxidized once sludge is applied to soil.
Rufus Chaney: Normal sludges have not caused increased mercury or
tin. Volatilization of sludge-mercury has not been observed.
Harvey Luce, University of Connecticut: Recent^reeearch^ indicates
that certain soils have the capacity to oxidise Cr+ to Ci. Should
this knowledge increase concern as to the potential of groundwater con-
tamination by sludges that are high in Cr?
Rufus Chaney: There is a difference between chromium oxidation
potential in artificial laboratory test systems, and finding oxidation in
the environment. High Cr sludges may be found to eventually allow some
Cr oxidation, but sewage sludges with several thousand ppm have not been
found to cause increased chromate 1n groundwater.
Charles F. Jelinek, Food and Drug Administration: Cadmium is cer~
tainly the primary metal of concern, but we should not disregard lead.
Because of the adverse effects of trace levels of lead on infante and
young children, the lead levels in food eaten by infante and pregnant
women need to be controlled. Even though lead is not taken up by plants
through the root system, it can enter 'the food and feed chain if sludge
is applied to the land by spraying. Because of these factors controls
for lead as well as cadmium should be established.
Richard Thomas> National Coordinator, Innovative /Alt emotive Tech-
nology Program, EPA, Construction Grants Programs, Washington, DC: I
want to make some observations as an oldtimer with 20 years in research
who is now responsible for the alternative technology part of the federal
grants program to improve publicly owned treatment works (P01V).
1. Congress has shorn increasing confidence in land treatment with
each revision of law since 1972 and shows no inclination to
change their thinking.
2. Implementing these laws has led to building over 1,000 new land
treatment systems since 1973 and I expect to see even move new
systems in the next 10 years.
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3.
4.
LOGAN AND CHANEY
Ae one who must make recommendations on guidance I am here to
find out if our present guidance ie (1) too conservative and
hence costly, (2) adequate and needing only fine tuning, or (3)
too risky and hence subjecting the public to unacceptable riske*
This morning I have heard that the major research efforts of the
last 10 years have not identified any detectable risk but thie
is still not a positive indication that present design guidance
is conservative, adequate, or risky.
I hope that the workshop eeesione produce something more defini-
tive and useful ae the output from 10 years of research.
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AN OVERVIEW OF PUBLIC HEALTH EFFECTS
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AN OVERVIEW OF PUBLIC HEALTH EFFECTS
Norman E. Kowal
Toxicology and Microbiology Division
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
INTRODUCTION
The legislative mandate for the greater use of land application of
municipal wastewater and sludge 1s found in the Clean Water Act of 1977
(PL 95-217), Title II (Grants for Construction of Treatment Works),
Section 201, which states that the:
Administrator shall encourage waste treatment management
which results in the construction of revenue producing
facilities providing for (1) the recycling of potential
sewage pollutants through the production of agriculture,
silviculture, or aqua-culture products, or any combination
thereof...
Moreover, the Act requires that a construction grant not be made unless:
...the grant applicant has satisfactorily demonstrated to
the Administrator that Innovative and alternative wastewater
treatment processes and techniques which provide for the re-
claiming and reuse of water, otherwise eliminate the
discharge of pollutants, and utilize recycling techniques,
land treatment, new or Improved methods of waste treatment
management for municipal and Industrial waste (discharged
into municipal systems) and the confined disposal of pollu-
tants, so that pollutants will not migrate to cause water or
other environmental pollution, have been fully studied and
evaluated by the applicant taking Into account section
201(d) of this Act and taking Into account and allowing to
the extent practicable the more efficient use of energy and
resources.
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KOWAL
The two most important mechanisms in the U.S. for the recycling
of municipal sewage are land treatment of wastewater and land applica-
tion of sludge. There are three types of land treatment systems 1n
general use: slow rate {or "irrigation"), rapid infiltration (or
"infiltration-percolation"), and overland flow. Many of the examples
of "land treatment" systems in the U.S. utilize wastewater treated by
conventional means up to tertiary level (secondary in the case of
overland flow). The objectives of these systems are usually to pro-
duce clean irrigation water (e.g., for golf course application) or
highly treated water for groundwater recharge. From a wastewater
treatment point of view, land application in these systems is a form
of tertiary treatment or effluent "polishing," rather than true land
treatment. In land treatment systems raw wastewater is given a mini-
mum preapplication treatment, or "pretreatment," e.g., by a stabiliza-
tion pond, before being applied to the land, and the land itself is
the site of the major portion of the wastewater treatment.
Land application of sludge consists of the low-rate application
(compared with a purely disposal operation) to agricultural, forest,
or reclaimed land of municipal wastewater sludge which has been
"stabilized" in some way, e.g., anaerobic digestion or composting.
That land application of sludge is an Important and probably growing
practice in the U.S. is indicated by the results of a recent survey of
1008 publicly owned treatment works, account for over 2 million dry
metric tons per day of sludge (Peirce and Bailey 1982). The survey
found 17% of the total sludge to be utilized in large scale food-chain
landspreading, 12% in large scale non-food-chain landspreading, and
21% in distribution and marketing systems (much of which probably ends
up In gardens and lawns).
With the application to land of large volumes of wastewater and
sludge, it is evident that considerable potential for adverse health
effects exists. The major health concerns with land treatment of
wastewater and land application of sludge are somewhat different.
Thus, the potential exposure of humans through the routes of aerosols
and groundwater is frequently emphasized with wastewater, and through
the food chain with sludge. Nevertheless, the agents, or pollutants,
of concern from a health effects viewpoint are almost the same 1n
waste-water and sludge, so that a unified approach to the public
health effects of land application of both is reasonable and con-
venient.
It is the purpose of this report to briefly examine the potential
health effects of land application of wastewater and sludge, and to
provide an appraisal of these effects. The agents of concern can be
divided Into the two broad categories of pathogens and toxic substan-
ces. The pathogens Include bacteria (e.g., Salmonella and Shigella),
viruses {i.e., enteroviruses, hepatitis virus, adenoviruses,
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rotoviruses, and Norwalk-like agents), protozoa (e.g., Entamoeba and
Giardi a), and helminths (or worms, e.g., Ascaris, Trichuris, and
Toxocara). The toxic substances include organics, trace elements (or
heavy metals, e.g., cadmium and lead), nitrates, and sodium. Nitrates
and sodium are usually not viewed as "toxic" substances, but are here so
considered because of their potential hematological and long-term car-
diovascular effects when present in water supplies at high levels.
These agents form the basis of the main sections of this report. The
major health effects of these agents are listed in Figure 1.
BACTERIA
The pathogenic bacteria of major concern in wastewater and sludge
are listed in Table 1. All have symptomless infections and humart
carrier states, and many have important nonhuman reservoirs as well.
The pathogenic bacteria of minor concern are listed in Table 2; this
list is perforce somewhat arbitrary since almost any bacterium can
become an opportunistic pathogen under appropriate circumstances, e.g.,
in the immunologically compromised or in the debilitated. Recent
reviews of pathogens in wastewater include those by Benarde (1973),
Burge and Marsh (1978), Elliott and Ellis (1977), Kristensen and Bonde
(1977), and Menzies (1977).
Table 1. Pathogenic bacteria of major concern.
Name
Nonhuman reservoir
Cattle, dogs, cats, poultry
Domestic and wild mammals, rats
Domestic and wild mammals,
birds, turtles
Campylobacter jejuni
Escherichia con (pathogenic strains)
Leptospira spp.
Salmonella paratyphi (A,B,C)*
Salmonella typhi
Salmonella" spp.
Shi gel la sotjnel, S^. flexneri,
S. boydii, S. dysenteriae
"Vibrio cholerae
Yersinia enterocolitica, Y_.
pseudotuberculosis Wild and domestic birds and
mammals
*Correct nomenclature: Salmonella paratyphi A, S. schottmuellerfS.~
hi rschfeldi i, respectively.
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Agent (Pollutant)
Health Effect
Pathogens-
Toxic
Substances-
"Eacterla
Vi ruses
Protozoa
Helminths
Urganics
Trace Elements
Nitrates
Sodium
-Infection, Disease
-Hypersensitivity
-Acute Toxicity
-Mutagenesis and
Carcinogenesis
-Teratogenesis
-Other Chronic Effects
(cardiovascular,
Immunological,
hematological,
neurological, etc.)
Figure 1. Major health effects of pollutants.
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Table 2. Pathogenic bacteria of minor concern.
Aer onion as spp.
licllus cereus
Brucella spp.
Citrobacter spp.
CIostrldlum perfrlngens
ng(
TT
Coxiella burneti
Enterobacter spp.
Erysipelotrix rFusiopathlae
FranciseTTa tularensls
Klebsiella spp.
Legionella pneumophila
Listeria monocytogenes
Mycobacterium tuberculosis
M. spp.
Proteus spp.
Pseudomonas aeruginosa
~ Serratia spp.
Staphylococcus aureus
Streptococcus spp.
Campylobacter jejuni (formerly £. fetus subsp. jejuni) 1s a
recently-recognized cause of acute gastroenteritis with diarrhea. It
Is now thought to be as prevalent as the commonly recognized enteric
bacteria Salmonella and Shigella, having been isolated from the stools
of 4-856 of patients with diarrhea (MMWR 1979).
Pathogenic strains of the common intestinal bacterium Escherichia
co1i are of three types--enterotoxigenic enteropathogenlc, and entero-
invaslve (WHO Scientific Working Group 1980). All produce acute
diarrhea, but by different mechanisms. Fatality rates may range up to
40% in newborns. Outbreaks occasionally occur in nurseries and insti-
tutions, and the disease is common among travelers to developing
countries.
Leptospira spp. are bacteria excreted 1n the urine of domestic
and wild animals, and enter municipal wastewater primarily from the
urine of Infected rats Inhabiting sewers. Leptospirosis 1s a group of
diseases caused by the bacteria, and may manifest Itself through
fever, headache, chills, severe malaise, vomiting, muscular aches, and
conjunctivitis, and occasionally meningitis, jaundice, renal Insuf-
ficiency, hemolytic anemia, and skin and mucous membrane hemorrhage.
Fatality 1s low, but increases with age, and may reach 20* or more 1n
patients with jaundice and kidney damage (Benenson 1975). In the
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U.S., 498 cases were reported in 1974—78 {Martone and Kaufmann 1980).
Direct transmission from humans is rare, with most infection resulting
from contact with the urine of infected animals, e.g., by swimmers,
outdoor workers, sewer workers, and those in contact with animals.
Salmonella paratyphi (A, B, C) causes paratyphoid fever, a
generalized enteric infection, often acute, with fever, spleen
enlargement, diarrhea, and lymphoid tissue Involvement. Fatality rate
is low, and many mild attacks exhibit only fever or transient
diarrhea. Para-typho1d fever is infrequent in the U.S. (Benenson
1975).
Salmonella typhi causes typhoid fever, a systemic disease with a
fatality rate oT T~0% untreated or 2-3% treated by antibiotics
(Benenson 1975). It occurs sporadically in the U.S., where 647 cases
were reported in 1979 (MMWR 1980a), but is more common in the deve-
loping countries.
Salmonella spp., including over 1000 serotypes, cause salmonello-
sis, an acute gastroenteritis characterized by abdominal pain,
diarrhea, nausea, vomiting, and fever. Death is uncommon except in
the very young, very old, or debilitated (Benenson 1975). In 1979,
30,476 cases were reported to the Center for Disease Control (CDC)
(MMWR 1980a).
Shigella sonnei, S. flexneri, S.- boydii, and S. dysenteriae
cause shigellosis, or "Bacillary dysentery, an acute enteritis pri-
marily Involving the colon, producing diarrhea, fever, vomiting,
cramps, and tenesmus. There is negligible mortality associated with
shigellosis (Butler et al., 1977). In 1979, 15,265 cases were
reported to CDC (MMWR T980F).
Vibrio cholerae causes cholera, an acute enteritis characterized
by sudden onset, profuse watery stools, vomiting, and rapid dehydra-
tion, acidosis, and circulatory collapse. Fatality rates are about
50% untreated, but less than li treated (Benenson 1975). Cholera 1s
rare 1n the U.S., there being no reported cases between 1911 and 1972,
although one case occurred 1n 1973 in Texas and 11 1n 1978 in
Louisiana (Blake et al- 1980).
Yersinia enterocolitis and Y. pseudotuberculosis cause yer-
sinlosls, an acute gastroenteritis and/or mesenteric lymphadenitis,
with diarrhea, abdominal pain, and numerous other symptoms. Death Is
un-common. Yers1nios1s occurs only sporadically 1n the U.S., and 1s
transmitted from either infected animals or humans.
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Most bacteria of concern fn wastewater get there from human
feces, although a few, such as Leptospira, enter through urine. The
contribution from wash water, or "grey water," is probably relatively
insignificant, except as it may contain opportunistic pathogens. The
presence and levels in wastewater and sludge of any of the pathogens
listed in Tables 1 and 2 depend, of course, on the levels of infection
in the contributing population.
Bacteria: Potential Exposure
The human exposure to aerosol bacteria at land treatment sites
can be roughly estimated from the data at Kibbutz Tzora, Israel, where
raw wastewater was sprayed (Katzenelson and Teltch T976), thus
yielding higher bacterial levels than those found at Deer Creek, Ft.
Huachuca, or Pleasanton, where treated wastewater was sprayed. Thus,
an adult male, engaged in light work, breathing at a rate of l,2m3/hr,
and exposed to 34 coliforms/m3 (the Kibbutz Tzora average) at 100 m
downwind from a sprinkler, would inhale approximately 41 conforms per
hour. Since the ratio of aerosolized Salmonella to coliforms 1s 1:105
(Grunnet and Tramsen 1974) the rate of inhalation of Salmonella would
be about 105-fold less, an extremely low rate of bacterial exposure.
More recent data from Kibbutz Tzora allows a more accurate estimate of
human exposure (Teltsch et al_. 1980). During a period of time in
1 977-78, when the wastewater total conforms were 2.4 x 106 to 1.4 x
107/100 ml and Salmonella was 0-60/100 ml, the density of aerosol
Salmonella at 40 m, the maximum distance found, was 0-0.054 m3, with a
mean of 0.014/m3. This would result fn an inhalation rate of 0.017/hr
at 40 m, higher than the previous estimate, but still an extremely low
rate of bacterial exposure (cf- the infective dose discussion below).
Harding et al. (1981) have studied the production of microbial aero-
sols by FFTeTand application of liquid municipal sludge at three sites
using tank-truck application and three sites using high-volume spray
guns. Very low bacterial aerosol levels were found at the tank-truck
sites, but elevated levels of fecal conforms, fecal streptococci, and
mycobacteria were found at the spray sites.
Survival times of bacteria on crops have been summarized by Bryan
(1977), Sepp (1971), Feachem et al_. (1978), Rudolfs et aK (1951a),
and Larkin (1978a).
The survival of bacteria on plants, particularly crops, 1s espe-
cially important since these may be eaten raw by animals or humans,
may contaminate hands of workers touching them, or may contaminate
equipment contacting them. Such ingestion or contact would probably
not result 1n an infective dose of a bacterial pathogen, but 1f con-
taminated crops are brought Into the kitchen 1n an unprocessed state
they could result 1n the regrowth of pathogenic bacteria, e.g.,
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Salmonella, in a food material affording suitable moisture, nutrients,
Jn3~temperature (Bryan, 1977). It should be kept in mind that many
bacteria on plants, as well as soil, are not contaminants from human
beings. For example, Klebsiella spp., Enterobacter spp., Serratla
spp., and Pseudomonas aeruginosa are believed to be part of the
natural flora of vegetables (Remington and Schimpff 1981).
Thus, the consumption of subsurface and low-growing food crops,
e.g., leafy vegetables and strawberries, harvested from an application
site within about six months of last application, is likely to
increase the risk of disease transmission, because of contamination
with soil and bacterial survival in cracks, leaf folds, leaf axils,
etc. Possible approaches to avoid this problem are (1) use of the
subsurface or covered drip irrigation method for aerial crops
(Sadovski et al., 1978a, 1978b), (2) growth of crops the harvested
portion of whfcFi does not contact the soil, e.g., grains and orchard
crops, or (3) growth of crops used for animal feed only, e.g., corn
(maize), soybeans, or alfalfa. The last alternative 1s probably the
most common and most economic. In the situation where the harvested
portion does not contact the soil nor is within splash distance,
stopping application a month prior to harvest would be prudent.
Although properly designed slow-rate land treatment systems pro-
bably pose little bacterial threat to groundwater, considerable threat
exists at rapid-Infiltration sites where the water table 1s shallow,
particularly if the soil 1s porous. Over 60 million people 1n the
United States are served by public water supplies using groundwater,
and about 54 percent of the rural population and 2 percent of the
urban population obtain their water from 1nd1vdual wells (Dubolse et
al., 1979). Thus, it 1s Imperative that land treatment systems do not
result 1n the transmission of disease through groundwater. This Is
not to Imply that groundwater 1n the U.S. 1s now pristine. Almost
half of the waterborne disease outbreaks 1n the U.S. between 1971 and
1977 were caused by contaminated groundwater (Craun, 1979), and a
recent examination of individual groundwater supplies 1n a rural
neighborhood of Oregon (Lamka et aj_., 1980) showed more than one-third
to be fecally contaminated. Sut, thus far, no disease outbreaks have
been attributed to wastewater land treatment systems (Gerba and Lance,
1980).
Land application of sludge probably poses less of a bacterial
threat to groundwater. Thus, L1u (1982) 1n Canada has found that
after 4 years of heavy sludge application sewage bacteria were Inca-
pable of moving through the soli columns tested, and over 90% of the
surviving sludge bacteria were still detained 1n the top 20 cm layer
of soil. He concluded that there was little possibility of bacterial
contamination of groundwater by the practice of sludge farmland appli-
cation, provided that the water table was not too high and the soil
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An Overview of Public Health Effects
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was well-drained. Similar results have been found in leachate experi-
ments in South Africa (Nell et al., 1981).
Bacteria: Effects on Animals
The disease hazards to farm animals from land application of
sludge have been reviewed by Argent et aj_. (1 977) and Carrington
(1978). The major bacterial concerns wTth respect to animals grazing
at land application sites are Salmonella infections and bovine tuber-
culosis (Mycobacterium bovis and M. tuberculosis); both can be passed
on to man.
That the transmission of salmonellosis to cattle grazing at land
application sites is at least possible was demonstrated by Taylor and
Burrows (1971), who showed that calves grazing pastures, to which 106
Salmonella dubTin organisms/ml of slurry had been applied, became in-
fected. Ro infection occurred when the rate was decreased to 103/ml,
suggesting that Salmonella may only be of concern when high con-
centrations are present. At the San Angelo, Texas, slow-rate land
treatment site, although Salmonella was isolated from the soil and the
seepage creeks, the proportion of cattle grazing the pastures that
were shedding Sal mope11 a in their manure was not unusually high
(Weaver et^ al., 1978). Feacham et^ al. (1978) concluded that there 1s
no clear evTcfence that cattle grazecTat land treatment sites are more
at risk from salmonellosis than other cattle, probably because the
required infectious doses are high and Salmonella infections are
transmitted among cattle 1n many other ways. CTn the basis of
Salmonella measurements 1n wastewater and sludge 1n England, Jones et
al., (1980) concluded that a four-week waiting period would prevent
salmonellosis in grazing animals.
Argent et_ al. (1981) have examined the Salmonella content of
sludges treated Tn~ several ways, applied raw sludge (11 Salmonella/100
ml) to a field at the rate of 44.8 m3/ha, and confined 10 lambs to the
field for 2 months. None of the lambs became infected, as measured by
feces, rumen, and tissue samples, and clinical symptoms. Ayanwale et
al. (1980) raised goats on corn silage grown on sludge-amended lancTT
and found no Salmonella infections In spite of the presence of
Salmonella 1n the sludge, supporting the position that the potential
public health hazard resulting from the use of sludge as fertilizer
when properly treated has so far proven not to be a threat.
Nevertheless the significance of Salmonella 1n land applied sludge 1s
an Issue yet to be settled. Evidence in Switzerland from studies of
carrier rates and serotypes 1n cattle grazed on sludge-treated
pastures has indicated a positive association and a cycle of Infection
from man to sludge to animals to man. Experience 1n the Netherlands
1s similar, but there 1s no evidence of such a link 1n the United
Kingdom, despite the compulsory reporting of incidents (WHO 1981).
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Several investigations on tuberculosis Infection of cattle
grazing on wastewater-1rr1gated land have been performed In Germany,
with the conclusion that if application is stopped 14 days before
pasturing, there is no danger that grazing cattle will contract bovine
tuberculosis (Sepp, 1971).
Other possible bacterial concerns with respect to animals grazing
at land treatment sites are Leptospi ra (causing leptosoirosls),
Bruce! la (causing brucellosis), an<3 Eaci 11 us anthraci s (causing
anthrax. Wastewater, however, probably contains insignificant numbers
of these pathogens, and plays a negligible role in the transmission of
these diseases (Feachem et a_l_., 1978).
Bacteria: Infective Dose and Risk of Infection
Upon being deposited on or in a human body a pathogen may be
destroyed by purely physical factors, e.g., desiccation or decomposi-
tion. Before 1t can cause an infection, and eventually disease, it
must then overcome the body's natural defenses. In the first interac-
tion with the host, whether in the lungs, in the gastrointestinal
tract, or other site, the pathogen encounters nonspecific Immunologic
responses, i.e., inflammation and phagocytosis. Phagocytosis is
carried out primarily by neutrophils or polymorphonuclear leukocytes
1n the blood, and by mononuclear phagocytes, i.e., the monocytes 1n
the blood and macrophages in the tissues (e.g., alveolar macrophages
in the lungs). Later interactions with the host result in specific
Immunologic responses, i.e., humoral immunity via the B-lymphocytes,
and cell-mediated Immunity via the T-lymphocytes (Bellanti, 1976).
With these barriers to overcome 1t 1s understandable that an
infection resulting from inoculation by a few bacterial cells is a
most unlikely occurrence; usually large numbers are necessary. Some
representative oral infection dose data for enteric bacteria, based
upon numerous studies using non-uniform techniques, are presented 1n
Table 3 (adapted from Bryan, 1977).
Although the terms, "infective dose," "minimal fnfectious dose,"
etc., are used in the literature, 1t 1s obvious from Table 3 that
these are misnomers, and that we are really dealing with dose-response
relationships, where the dose 1s the number of cells to which the
human is exposed, and the response Is lack of Infection, Infection
without illness, and Infection with Illness (1n an Increasing propor-
tion of the test subjects). The response 1s affected by many factors,
making 1t highly variable. Some of the most important factors are
briefly discussed below.
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Table 3. Infective dose to man of enteric bacteria.
No
Infection
Infections
Percent of volunteers
or no
without
developing illness
Bacterium
11lness
11lness
1-25 26-50 51-75 76-100
Clostridium
perfri ngens
Escherichia col 1
0124:K72:H-
0148:H28
0111:B4
Several strains
10**
IO10
io^-io6
108
108
106
108
109
106-109
io8 io8-ini°
io9
io10
ioi°
Salmonella typhi
TyZW
Zermat vi
Most strains
S. newport
37 bare?11y
1TT anatum
"57 meleagridis
T7 derby
T7 pullorum
103
lO^-lO6
io^-io6
105-106
10M09
Shigella
dysenteri ae
S. flexneri
Streptococcus
faecal i s
var. liquefaclens 108
Vibrio cholerae
RaffCO -buffered 10
Unbuffered 10M010
103
108
105 105-108
10^
105
105
105-108
106
IO6
106
106
107 107-108
107
109
103-108 104-106
lOMO11
108-109
109-1010
10-102 io2-io4 in3 io4
ioMo4 io3-io9 io6-io8
109 io10
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1. The site of exposure determines what types of defense mechanisms
are available, e.g., alveolar macrophages and leukocytes 1n the
lungs, and acidity and digestive enzymes in the stomach. The
effect of acidity 1s clearly shown by the cholera (Vibrio cholerae)
data in Table 3, where buffering reduced the infective dose by
about a thousandfold. Direct Inoculation Into the bloodstream
results in the fewest barriers being presented to the pathogen;
Hellman et al. (1976) found 10 tuleremia organisms injected to be
comparable" To 108 by mouth.
2. Previous exposure to a given pathogen often produces varying
degrees of immunity to that pathogen, through the induction of
specific immune responses. A study in Bangladesh showed that
repeated ingestion of small inocula (lO^lO1* organisms) of Vibrio
cholerae produced subclinical or mild diarrhea infection followed
by specific antibody production. For this reason the peak Inci-
dence of endemic cholera occurs in the one to four-year old age
group, and decreases with age thereafter as immunity develops
(Levine, 1980).
3. Other host factors, such as age and general health, also affect
the disease response. Infants, elderly persons (Gardner, 1980),
malnourished people, those with concomitant illness, and people
taking antiinflammatory, cytotoxic, and immunosuppressant drugs
would be more susceptible to pathogens. An example of human
variability (possibly genetic) is the following response of men
orally challenged with several different doses of Salmonella
typhi (Hornlck et £l_. 1970):
Twenty-eight percent of the men came down with typhoid fever
after 105 organisms, while five percent were still resistant to
109 organisms, four orders of magnitude as many.
4. The number of organisms that must be swallowed for intestinal
colonization (subclinical infection), and consequent risk of cli-
nical disease, to be established is affected by treatment with
antibiotics (Remington and Schlmpff 1981). Due to Its normal
content of anaerobic bacteria and their products, the gut can
resist colonization when an oral dose of about 106 organisms 1s
given. Once resistance 1s reduced by systemic or oral anti-
biotics, the dose required to induce colonization is only ten to
100 organisms.
S. tvphl
T0^~
105
107
109
Number of
Percent developing
typhoid fever
T
28
50
95
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5. The timing of the exposure to pathogens, e.g., as a single expo-
sure or an exposure over a long period of time, would be expected
to affect the response.
6. Finally, as illustrated by Escherichia coli and Salmonella typhi
in Table 3, the virulence, or pathogenicity, of bacteria varies
among strains. Thus, three different strains of Shi gel 1 a
flexneri have been found to have infective doses of 101U or
higher, 105-108, and 180 organisms (NRC, 1977).
The risk of infection is probably greatest for Salmonella spp.
and Shi gel la spp., because they are the most common bacterial patho-
gens in municipal wastewater. The infective dose for Salmonella 1s
high (105-108 organisms) but this dose might be reached on a con-
taminated foodstuff under conditions that allow multiplication. A
recent review of experimentally-induced salmonellosis and salmonello-
sis outbreaks, however, has resulted in the conclusion that the infec-
tive dose for Salmonella may well be below 103 organisms {Blaser and
Newman, 1982). On the other hand the infective dose for Shi gel!a is
low—as few as 10 to 100 organisms. "Because of this miniscule inocu-
lum it 1s rather simple for shigellae to spread by contact without
Interposition of a vehicle such as food, water or milk to amplify the
infectious dose" (Keusch, 1979).
Consequently, it would be prudent for humans to maintain a mlni-
num amount of contact with an active land application site, and to
rely on "time" to reduce the bacterial survival, as discussed earlier,
when growing crops for human consumption.
Bacteria: Epidemiology
A number of epidemiological reports have attested to the fact
that transmission of enteric disease can occur when untreated
wastewater 1s used in the cultivation of crops to be eaten raw
(Geldreich and Bordner, 1971; Hoadley and Goyal, 1976; and Sepp,
1971). Salmonellosis has been traced to the consumption of
wastewater-irr1gated celery, watercress, watermelon, lettuce, cabbage,
endive, salad vegetables, and fruits; shigellosis to wastewater-
1 rrigated pastureland; and cholera to wastewater-1rr1gated vegetables
in Israel.
Perhaps the largest epidemiological study of the health effects
of land treatment was a retrospective study of 77 kibbutzim
(agricultural cooperative settlements) 1n Israel practicing slow-rate
land treatment with nondlslnfected oxidation pond effluent, and 130
control kibbutzim (Katzenelson et ajk, 1976). The incidence of
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typhoid fever, salmonellosis, shigellosis, and Infectious hepatitis
was 2-4 times higher 1n the land-treatment kibbutzim than the
controls. The study, however, did not rule out a number of pathways
of infection other than aerosols, e.g., direct contact via clothing or
bodies of sewage irrigation workers, and there were problems with the
data reporting methods. Consequently, it 1s generally felt that no
conclusive findings may be based on the report, and the study has been
repeated, correcting for the deficits of the original study (Shuval
and Fattal, 1980). The final report of the revised study (Shuval et
al, 1983) did not confirm the extreme differences found 1n the 197£
report, although a small significant excess risk of total enteric
disease was found during effluent Irrigation periods. None of the
findings provided direct support for the hypothesis that the main
pathway of pathogens transmissions was aerosolized effluent resulting
from sprinkler irrigation.
Other epidemiological reports on the health effects of land
application have been more superficial. Examination of the workers on
sewer farms in Berlin and Memmingen in Germany has not shown them to
have a higher rate of infectious diseases or worm Infestation than the
rest of the population (Sepp, 1971). At land treatment sites near
Paris, grain for cattle, beef cattle, and vegetables (e.g., beans,
onions, and celeriac) are raised (Dean, 1978). The vegetables are
checked for Salmonella, with none having been found, and no disease
has been traced to the farms. During a cholera outbreak, no cholera
bacteria were found on the vegetables. At Werrlbee Farm 1n Melbourne,
Australia, there has never been a reported epidemic or outbreak of
disease among employees or residents, although no precautions other
than normal hygiene practices have been taken, and the general health
of employees and residents is no different from that of the community
1n general (Croxford, 1978).
Although these retrospective studies are reassuring, a better
measure of the health effects of land application will come from well-
planned prospective epidemiological studies. Two such studies, on
land treatment, are currently underway--at Lubbock, Texas, and 1n
Israel. A third study, on land application of sludge, 1s currently
underway in Ohio. The results of these three projects may well modify
the conclusions and recommendations of this report in the future.
VIRUSES
Transmission of viruses by feces 1s the second most frequent
means of spread of common viral Infections, the first being the
respiratory route. Transmission by urine has not been established as
being of epidemiological or clinical Importance, although some viru-
ses, e.g., cytomegalovirus and measles, are excreted through this
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route. The gastrointestinal tract 1s an Important portal of entry of
viruses into the body, again second to the respiratory tract (Evans,
1976).
The human enteric viruses that may be present in wastewater and
sludge are listed in Table 4 (Melnick et al_., 1978; Holmes, 1979).
These are referred to as the enteric viruses and new members are
constantly being identified. Since no viruses are normal inhabitants
of the gastrointestinal tract and none of these have a major reservoir
other than man (with the likely exception of rotaviruses), all may be
regarded as pathogens, although most can produce asymptomatic Infec-
tions.
Table 4. Human wastewater viruses.
Enterovi ruses
Pol i ovi rus
Coxsackievirus A
Coxsackievirus B
Echovi rus
New Enterovirus
Hepatitus A Virus
Rotavirus ("Duovirus", "Reovirus-11ke Agent")
Norwalk-Like Agents (Norwalk, Hawaii, Montgomery County,
etc.)
Adenovi rus
Reovirus
Papovavi rus
Astrovi rus
Ca11c1vi rus
Coronavlrus-L1ke Particles
Upon entry Into the alimentary tract, 1f not Inactivated by the
hydrochloric acid, bile acids, salts, and enzymes, enteroviruses,
hepatitis A virus, rotavirus, adenovirus, and reovlrus may multiply
within the gut. The multiplication and shedding of adenovirus and
reovlrus here has not been shown to be of major epidemiological Impor-
tance 1n their transmission (Evans, 1976). The rotavirus often produ-
ces diarrhea in children, but the local multiplication of entero-
viruses and (possibly) hepatitis A virus 1n cells lining the area
rarely produces local symptoms, I.e., diarrhea, vomiting, and abdomi-
nal pain. Most enterovirus infections, even with the more virulent
types, cause few or no clinical symptoms. Occasionally, after con-
tinued multiplication In the lymphoid tissue of the pharynx and gut,
viremla may occur, i.e., virus enters the blood stream, leading to
further virus proliferation 1n the cells of the reticuloendothelial
system, and finally to Involvement of the major target organs—the
central nervous system, inyocardlum, and skin for the enteroviruses,
and the liver for hepatitis A virus (Melnick et aiK, 1979; Evans,
1976).
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Pol iovi ruses cause pol iortiyeli11 s , an acute disease which may
consist simply of fever, or progress to aseptic meningitis or flaccid
paralysis (slight muscle weakness to complete paralysis caused by
destruction of motor neurons in the spinal cord). Polio 1s rare in
the United States, but may be fairly common In unimmunlzed populations
in the rest of the world. No reliable evidence of spread by
wastewater exists (Benenson, 1975).
Coxsackieviruses may cause aseptic meningitis, herpangina, epi-
demic myalgia, myocarditis, pericarditis, pneumonia, rashes, common
colds, congenital heart anomalies, fever, hepatitis, and Infantile
diarrhea.
Echoviruses may cause aseptic meningitis, paralysis, encephali-
tis, fever, rashes, common colds, epidemic myalgia, pericarditis,
myocarditis, and diarrhea.
The new enteroviruses may cause pneumonia, bronchiolitis, acute
hemorrhagic conjunctivitis, aseptic meningitis, encephalitis, and
hand-foot-and-mouth disease. The prevalence of the diseases caused by
the coxsackieviruses, echoviruses, and new enteroviruses is poorly
known, but 7075 cases were reported to the Center for Disease Control
(CDC) in the years 1 971 -75 (Morens et a 1 ., 1979). These enteroviruses
are practically ubiquitous in the woTTd, and may spread rapidly 1n
silent (asymptomatic) or overt epidemics, especially in late summer
and early fall in temperate regions. Because of their antigenic inex-
perience, children are the major targe't of enterovirus infections, and
serve as the main vehicle for their spread. Most of these Infections
are asymptomatic, and natural immunity 1s acquired with increasing
age. The poorer the sanitary conditions, the more rapidly immunity
develops, so that 90% of the children living under poor hygienic cir-
cumstances may be immune to the prevailing enteroviruses (of the
approximately 70 types known) by the age of 5. As sanitary conditions
improve, the proportion of nonimmunized 1n the population Increases,
and infection becomes more common 1n older age groups, where symp-
tomatic disease 1s more likely and 1s more serious (Melnlck et a 1. t
1 979; Benenson, 1975). Thus, decreasing the human exposure "To ~£Vie
common enteric viruses through the water and food route has its disad-
vantages, as well as advantages.
Hepatitis A virus causes infectious hepatitis, which may range
from an inapparent infection (especially 1n children) to fulminating
hepatitis with jaundice. Recovery with no sequelae 1s normal.
Approximately 40,000-50,000 cases are reported annually in the U.S.
About half the U.S. population has antibodies to hepatitis A virus,
and the epidemiological pattern is similar to that of enteroviruses,
with childhood Infection common and asymptomatic (Dubolse et al.,
1979). ~
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Rotavirus causes acute gastroenteritis with severe diarrhea,
sometimes resulting in dehydration and death in Infants. It may be
the most important cause of acute gastroenteritis in Infants and young
children, especially during winter (Konno et al., 1978), but also may
strike older children and adults (Holmes, r§7§77
Norwalk-like agents include the Norwalk, Hawaii, Montgomery
County, Ditchling, W, and cockle viruses, and cause epidemic gastroen-
teritis with diarrhea, vomiting, abdominal pain, headache, and rnyalgia
or malaise. The illness 1s generally mild and self-limited (Kapikian
et al., 1979). These agents have been associated with sporadic
outbreaks 1n school children and adults (Holmes, 1979).
Adenoviruses are primarily causes of respiratory and eye infec-
tion, transmitted by the respiratory route, but several strains are
now believed to be important causes of sporadic gastroenteritis 1n
young children (Richmond et aj_., 1979; Kapikian et^ aK, 1979).
Reoviruses have been isolated from the feces of patients with
numerous diseases, but no clear etiological relationship has yet been
established. It may be that reovirus infection 1n humans 1s common,
but associated with either mild or no clinical manifestations (Rosen
1979).
Papovaviruses have been found in urine, and may be associated
with progressive multifocal leukoencephalopathy (PML), but are poorly
understood (Warren, 1979).
Astrovlruses, cal1c1viruses, and coronavlrus-11ke particles may
be associated with human gastroenteritis, producing diarrhea, but are
also poorly understood (Holmes, 1979; Kapikian et a[., 1979).
Viruses: Potential Exposure
Aerosols have been of concern as a potential route of
transmission of disease caused by enteric viruses because, as with
bacteria, once they are inhaled they may be carried from the respira-
tory tract by c111 a Into the oropharynx, and then swallowed Into the
gastrointestinal tract. Some enteroviruses may also multiply in the
respiratory tract Itself (Evans, 1976). Another reason for concern 1s
the theoretically possible transmission of respiratory viruses through
wastewater aerosols. On the basis of actual viral sampling of
wastewater, however, Johnson et al. (1980) concluded that the likeli-
hood of finding respiratory vfruses 1n treated wastewater 1s very
small.
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KOWAL
The level of enteric viruses 1n aerosols at land treatment sites
is strongly dependent on the degree of pretreatment of the wastewater.
Thus, at the Muskegon County (Michigan) Wastewater Management System,
where large lagoons are used, no animal viruses were detected in air
samples collected at the spray irrigation area (Clark et , 1981).
On the basis of data obtained at the Pleasanton, CaTTfornia, land
treatment site (Johnson et £l_., 1980), 1t can be calculated that an
adult male, engaged in IfgFit work, breathing at a rate of 1.2 m3/hour
and exposed to 0.014 PFU/m3 at 50 m downwind from a sprayer, would
inhale approximately 0.13 PFU of enterovirus during and 8-hour work
day. This is probably an insignificant level of exposure. However,
since the recovery of enteric viruses from environmental samples Is
not perfectly efficient, isolation of viruses increases as more cell
culture types are used, and some enteric viruses cannot yet be iso-
lated on cell cultures, the actual exposure to enteric viruses may be
as much as ten to a hundred times the reported level (Teltsch et al.,
1980). Thus, it might be prudent to recommend a 100 m or 200 m mTni-
mum exposure distance of the general public to a land treatment spray
source.
The concentration of viruses in aerosols at liquid sludge spray-
appHcation sites has been examined by Hardi ng et (1981). On a
special virus run, 1470 m3 of air was sampled and no human enteric
viruses were detected from the pooled sample. This converts to a con-
centration of less than 0.0016 PFU/m3 of air, and the implication is
that aerosolization of viruses in liquid sludge does not present a
significant health risk.
Regrowth of viruses on crops and food 1s not a problem, the way
it is with bacteria, but the crop route of exposure 1s still of con-
cern. Much of the literature on survival time of viruses on crops has
been summarized by Feachem et aj_. (1978). The data are similar to
those for bacteria, and likewise appear to support a one-month waiting
period after last application before harvest.
Because of the possible contamination of subsurface and low-
growing crops with soil, in which viruses have a longer survival time,
about one hundred days would probably be a safe waiting period. As
with bacteria, this period could be shortened by (1) the use of sub-
surface or covered drip irrigation (Sadovski et al., 1978a; 1978b),
(2) the growth of crops the harvested portion ~oT "wfiich does not con-
tact the soil, or (3) the growth of crops used for animal feed only.
At a site where (2) and (3) were practiced, the Roswell, New Mexico,
slow-rate land treatment site where secondary effluent has been
applied by ridge-and-furrow irrigation for 33 years, no enteroviruses
were found on or In the leaf and grain portions of corn (Koerner and
Haws, 1979).
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Once enteric viruses get into groundwater, they can survive for
long periods of time, 2 to 188 days having been reported in the
litera-ture (Akin et^ al_., 1971), and probably migrate for long distan-
ces (Keswick and Gerba, 1980). Low temperatures prolong survival, but
the factors affecting survival in groundwater are poorly understood.
It might be possible, for example, that entry of viruses into the
groundwater would be tolerable if sufficient underground detention
tine could be provided before movement of the groundwater to wells or
streams (Lance and Gerba, 1978). Until these factors are well-
understood, it would be prudent to assume that groundwater underlying
coarse sandy or gravelly soils, and in the vicinity of rapid-
infiltration land treatment sites or septic tank-leaching field
systems, is contaminated with viruses. Groundwater drawn from such
sources for use as potable water supplies should be disinfected; this
advice is consistent with that of the World Health Organization
Scientific Group on Human Viruses in Water, Wastewater and Soil (WHO,
1979).
With reference to viruses in soil and groundwater at land treat-
ment sites Gerba and Lance (1980) have concluded:
Although the presence of viruses 1n groundwater has
been demonstrated, it would appear that with proper site
selection and management the presence of viruses could be
minimized or eliminated. The key is to define the processes
involved 1n the survival and transport of pathogens in
groundwater. With proper design, land treatment could be
used as an effective method - for reducing the number of
pathogens in wastewater. With the proper soil type, viruses
and bacteria can be reduced to levels as effective as
chlorlnatlon as currently practiced, after the travel of
wastewater through only a few centimeters of soil.
The problem of viruses in groundwater Is still not settled,
however, as evidenced by the far more cautious view taken by Welllngs
(1982). There appears to be little reliable information on viruses
getting Into groundwater beneath sludge application sites, although one
would expect the threat to be low.
An unusual route of exposure to viruses as a result of land appli-
cation is through mosquitoes. Zaim and Newson (1980) studied the
effects of wastewater spray irrigation on indigenous mosquito popula-
tions In Michigan agricultural and forested land. Mosquito populations
remained negligible in the farmed portion of the site, but a dramatic
increase occurred 1n the species diversity in the wooded portions. Most
of the species found bred outside the sprayed area, but three Culex spe-
cies, including potential transmitters of St. Louis encephal1t1s, bred
in pools and ponds in the most heavily sprayed area. Other species,
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KOWAL
from outside the sprayed area, are vectors of dog heartworm and
California encephalitis. The authors concluded that spray irrigation of
wastewater enhances the potential for pest and disease transmission in
the vicinity of such sites.
Viruses: Effects on Animals
Human polioviruses, coxsackieviruses, echoviruses, and reoviruses
have been recovered from, or found to produce infection in, at least six
species of animals--dogs, cats, swine, cattle, horses, and goats
(Metcalf, 1976). Dogs and cats were found to be involved in a majority
of instances, probably because of their intimate association with man in
the household. The present state of information on virus transmission
in animals and man does not appear to allow an evaluation of the effect
of land application on animal infections or the role of animals as
reservoirs of human disease (Metcalf, 1976).
Polley (1979) noted that, under experimental conditions, rota-
viruses of human origin have infected pigs, calves, and lambs, but
concluded that in Canada their transmission to livestock via effluent
irrigation was a slight and unproven risk.
Viruses: Infective Dose, Risk of Infection, and Epidemiology
In contrast with bacteria, where large numbers of cells are
usually necessary to produce an infection, a few virus particles are
currently thought to be able to produce an Infection under favorable
conditions. The most Important studies on the oral Infective dose of
enteric viruses 1n humans are summarized in Table 5 (modified from
National Research Council, 1977). The results are highly variable, and
may reflect differences 1n experimental conditions as well as states of
the hosts. The recent data do suggest, however, that the Infective dose
of enteroviruses to man 1s low, possibly of the order of 10 virus par-
ticles or less. The same factors discussed earlier, that affect bac-
teria also affect the virus dose-response relationship.
Since a potential route of exposure to viruses at land application
sites 1s aerosols, 1t 1s of great Importance to compare the Infective
dose through the respiratory route with that through the Ingestion
route. Couch et al. (1965) and Gerone et a_1_. (1966) reported the human
Inhalation infective dose of coxsackievirus A21 to be <18 TCD which
1s comparable with the oral Infective dose of the enteroviruses.
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An Overview of Public Health Effects Page 349
Table 5. Oral infective dose to man of enteric viruses.
™ Percent
Vi rus Subjects Dose* Infected Reference
Vacci ne
Infants
0.2 PFU**
0
Koprowskl 1956
poliovirus
2 PFU
67
20 PFU
100
105*5
50
Gelfand et al_. 1960
107*5
100
106*5
60
Krugman et al. 1961
107*5
75
5.
5xl06 PFU
89
Holgiun et ajk 1962
103*5
29
Lepow et 1962
104-5
46
1Q5-5
57
l03-5
68
Warren et aU 1964
105-5
79
Premature
1
30
Katz and Plotkln 1967
Infants
2.5
33
10
67
Infants
7-52+
1
Miner et £l_. 1981
24-63
10
55-93
50
Echovlrus 12
Young
10 PFU
18
Schfff et al. (personal
Adults
100 PFU
67
communicatTon) 1980
* Tissue culture dose 50% (TCD ) unless Indicated
**Plaque-Form1ng Unit 50
t95% Confidence Units
Theoretically, a single virus particle Is capable of establishing
Infection both 1n a cell 1n culture and in a mammalian host (Westwood
and Sattar, 1976). If this were to be the case, extreme care should be
taken to avoid human exposure to enteric viruses through aerosols or
crops grown on land application sites. On the other hand, the concept
that a single virus particle often constitutes an Infective dose 1n the
real world has been argued against (Lennette, 1976) on the basis of the
oral pollovacdne studies, nonImmunologic barriers, human immunologic
responses, and probabilistic factors.
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Viruses do not regrow on foods or other environmental media, as
bacteria sometimes do. Therefore, the risk of infection is completely
dependent upon being exposed to an infective dose (which may be very
low) in the material applied. In any event, as is the case with bac-
teria, it would seem prudent for humans to maintain a minimum amount of
contact with an active land application site, and to rely on the viral
survival data discussed earlier for limiting the hazard from crops grown
for human consumption on wastewater- or sludge-amended soils.
Fecally-polluted vegetable-garden irrigation water in Brazil has
been found to contain polioviruses and coxsackieviruses, and has been
associated with earlier epidemics (Christovao et aK, 1967a; 1967b). At
the Muskegon land treatment site spray irrigation workers did not have
increased illness or virus isolation rates (Clark et , 1981). Nor
did they, with a minor exception, have increased prevalence of infection
by hepatitis A, poliovirus (1, 2, 3), coxsackievirus (B2, B5), or echo-
virus (7, 11), as measured by serology. The exception was a high anti-
body titer to coxsackievirus B5 in the spray nozzle cleaners, a group
with presumably high exposure to wastewater. Some virologists, however,
feel that current epidemiological techniques are probably not suf-
ficiently sensitive to detect the low levels of viral disease
transmlss1 on that might occur from a modern land application site
(Melnick, 1978; WHO, 1979).
PROTOZOA
The protozoa and helminths (or worms) are often grouped together
under the term, "parasites," although in reality all the pathogens are
biologically parasites. Little attention has been given to the presence
of parasites in wastewater, and their potential for contaminating food
crops in the United States, probably because of the popular impression
that the prevalence of parasite infection in the U.S. is minimal (Larkln
et aH_., 1978b). However, because of the increasing recognition of para-
sTteTinfectlons in the U.S., the return of military personnel and trave-
lers from abroad, the level of recent immigration and food Imports from
countries with a high parasitic disease prevalence, and the existence of
resistant stages of the organisms, a consideration of parasites 1s
warranted.
The most common protozoa which may be found 1n wastewater are
listed 1n Table 6. Of these, only three species are of major signifi-
cance for transmission of disease to humans through wastewater:
Entamoeba histolytica, G1ard1a lamblla, and Balantidlum coll. Toxo-
plasma gondii also causes slgnlfleant human disease, but the wastewater
route 1s probably not of Importance. Elmeria spp. are often identified
1n human fecal samples, but are considered to be spurious parasites,
entering the gastrointestinal tract from Ingested fish.
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Table 6, Types of protozoa in wastewater.
Name
Protozoan Class
Nonhuman Reservoir
Human Pathogens
Entamoeba histolytica
Giardia Iambiia
Balantidium coli
Toxoplasma gondi i
Pi entamoeba fragfl is
Isospora belli
I. hominis
Human Commensals
Ameba
Flagellate
Ciliate
Sporozoan (Coccidia)
Ameba
Sporozoan (Coccidia)
Sporozoan (Coccidia)
Domestic and wild mammals
Beavers, dogs, sheep
Pigs, other mammals
Cats
Endolimax nana
Entamoeba" col i
lodamoeba butschlii
Ameba
Animal Pathogens
Eimeria spp.
Entamoeba spp.
Giardia Tpp.
Isospora spp.
Sporozoan (Coccidia)
Ameba
Flagellate
Sporozoan (Coccidia)
Fish, birds, mammals
Rodents, etc.
Dogs, cats, wild mammals
Dogs, cats
Entamoeba histolytica causes amebiasis, or amebic dysentery, an
acute enteritis, whose symptoms may range from mild abdominal discomfort
with diarrhea to fulminating dysentery with fever, chills, and bloody
and mucoid diarrhea. Most infections are asymptomatic, but 1n severe
cases dissemination may occur, producing liver, lung, or brain
abscesses, and death may result. Amebiasis is rare 1n the U.S.
(Krogstad et al_., 1978), and 1s transmitted by cysts contaminating water
or food.
Giardia lamb!1a causes giardiasis, an often asymptomatic Infection
of the small intestine, which may be associated with chronic diarrhea,
malabsorption of fats, steatorrhea, abdominal cramps, bloating, fatigue,
and weight loss. The carrier rate in different areas of the U.S. may
range between 1.5 and 20% (Benenson, 1975), and 1t Is transmitted by
cysts contaminating water or food, and by person-to-person contact
(Osterholm et al., 1981).
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Balantidium coli causes balantidiasis, a disease of the colon,
characterized by diarrhea or dysentery. Infections are often asymp-
tomatic, and the incidence of disease in man is very low {Benenson,
1975). Balantidiasis is s transmitted by cysts contaminating water,
particularly from swine.
Toxoplasma gondii causes toxoplasmosis, a systemic disease which
rarely gives rise to clinical illness, but which can damage the fetus 1f
infection, and subsequent congenital transmission, occurs during
pregnancy. Approximately 50% of the population of the U.S. is thought
to be infected (Krick and Remington, 1978), but the infection is pro-
bably transmitted by oocysts in cat feces or the consumption of cyst-
contaminated, inadequately-cooked meat of infected animals (Teutsch et
al., 1979), rather than through wastewater.
The active stage of protozoans in the intestinal tract of infected
Individuals is the trophozoite. The trophozoites, after a period of
reproduction, may round up to form precysts, which secrete tough membra-
nes to become environmentally-resistant cysts, in which form they are
excreted in the feces (Brown, 1969).
The types and levels of protozoan cysts actually present in
wastewater depend on the levels of disease in the contributing human
population, and the degree of animal contribution to the system.
Protozoa: Potential Exposure
Because of the large size of protozoan cysts and helminth eggs,
compared with bacteria and viruses, 1t is unlikely that they will find
their way Into either aerosols or groundwater at land application sites.
Because of their exposure to the air, protozoan cysts deposited on
plant surfaces would be expected to die off rapidly. The fact that
cysts can survive long enough to get Into the human food supply under
poor management conditions 1s confirmed by the recent isolation of high
levels of Entamoeba histolytica, E. coll, Endollmax nana, and Glardia
Iambi 1a on the wastewater-1rrigated fruits and vegetables 1n Mexico
City's marketplaces (Tay et al., 1980). Rudolfs et al. (1951b) found
contaminated tomatoes andletTiice to be free from vTatSTe Entamoeba pre-
sence of organic matter 1n the form of fecal suspensions. They
concluded that field-grown crops "... consumed raw and subject to con-
tamination with cysts of E_. histolytica are considered safe 1n the tem-
perate zone one week after contamlnation has stopped and after two weeks
1n wetter tropical regions."
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Therefore, 1f the recommendations, based on bacteria, for har-
vesting human food crops are followed, 1t is unlikely that any public
health risk will ensue.
Protozoa: Health Effects
Although it would be theoretically possible for protozoan diseases
to be transmitted through animals at a land application site, little
relevent information on the subject appears to exist. However, in view
of the survival times, the four week waiting period before the resump-
tion of grazing, recommended on the basis of bacteria, should prevent
any problem from developing.
Human infections with Giardia 1amblia and the nonpathogenic
Entamoeba coli have been produced with ten cysts administered in a gela-
t1n capsule (Rendtorff 1954a; 1954b). Infections have been produced
with single cysts of Entamoeba coli, and there is no biological reason
why single cysts of Glardla would not also be Infectious (Rendtorff,
1979). This is probably true for E. histolytica as well (Beaver et al.,
1956). The pathogenicity of protozoa is highly variable among sFraTns,
and human responses likewise are variable. Thus, many infections are
asymptomat ic.
Because of the low Infective doses of protozoan cysts, it would be
prudent for humans to maintain a minimum amount of contact with an
active land application site. However, if the recommended waiting
periods for crop harvest are followed, the risk of infection should be
minimal, because of the cysts' sensitivity to drying.
A few epidemiological reports have linked the transmission of ame-
biasis to vegetables irrigated with raw wastewater or fertilized with
night soil (Bryan, 1977; Gelreich and Bordner, 1971).
HELMINTHS
The pathogenic helminths whose eggs are of major concern In
wastewater and sludge are listed in Table 7. They are taxonomlcally
divided into the nematodes, or roundworms, and cestodes, or tapeworms.
The trematodes, or flukes, are not Included since they require aquatic
conditions and Intermediate hosts, usually snails, to complete their
life cycles, and thus are unlikely to be of concern at land treatment
sites. Some common helminths, pathogenic to domestic or wild animals,
but not to humans, are listed 1n Table 8 (after Relmers et^al., 1980),
since their eggs are likely to be Identified In wastewater."Several of
the human pathogens listed 1n Table 7, e.g., Toxocara spp., are actually
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Page 354 kowal
animal parasites, rather than human parasites, infesting man only Inci-
dentally, and not completing their life cycle in man.
Table 7. Pathogenic helminths of major concern in wastewater.
Nonhuman
Pathogen
Common Name
Di sease
Reservoi r
NEMATODES (Roundworms)
Enterobius
P1nworm
Enteroblasis
vermicuiaris
Ascaris
Roundworm
Ascariasis
lumbrlcoides
A. suum
Swine roundworm
Ascariasis
Pig*
Ari churls
Whi pworm
Tri churi asis
tri chiura
Necator
Hookworm
Necatoriasis
americanus
Ancylostoma
Hookworm
Ancylostomlasis
duodenale
A. braziliense
Cat hookworm
Cutaneous larva migrans
Cat,
dog*
A. canlnum
Dog hookworm
Cutaneous larva migrans
Dog*
Strongyl oi des
Threadworm
Strongyloidiasis
Dog
stercoralis
Toxocara canis
Dog roundworm
Visceral larva migrans
Dog*
T. cati
Cat roundworm
Visceral larva migrans
Cat*
CESTODES (Tapeworms)
Taenia
Beef tapeworm
Taeniasis
sagi nata**
T. solium
Pork tapeworm
Taeniasis, Cysticercosis
Hym'enolepls
Dwarf tapeworm
Taeniasis
Rat,
mouse
nana
EchTnococcus
Dog tapeworm
Unilocular hydatid disease Dog*
granulosus
E. multilocularis
Alveolar hydatid disease
Dog,
fox,
cat*
* Definitive host; man only incidentally Infested
**Eggs not infective for man
Enteroblus vermlcularls, the plnworm, causes itching and discomfort
1n the perl ana 1 area, particularly at night when the female lays her
eggs on the skin. A 1972 estimate of the prevalence of pinworm Infec-
tions irt the U.S. was 42 million (Warren, 1974). Although it is by far
the most common helminth Infection, the eggs are not usually found 1n
feces, are spread by direct transfer, and live only for a few days.
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Table 8. Animal-pathogenic helminths in wastewater.
"Pathogen"
Definitive Host
Trichuris suis Pig
T. vu1p is Dog
Toxascaris leonina* Dog, cat
flscari rii a galli Poultry
HeterakisT cjaTTTnae Poultry
Trichosomoides eras si cauda Rat
AnatTTchosoroa buccalis Opossum
(Truzia americana Opossum
Capillaria hepatica Rat
TT. gastrica Rat
"C. spp. Poultry,
TTymenolepis di mi nut a Rat
H. Spp. Birds
Taenia pisiformis Cat
T^ydatTgera taeni a'eformi s Dog
MacracantTTorhynchus hi rufdi naceous Pi g
wild birds, wild mammals
*Toxascaris leonfna may produce visceral larva migrans 1n experimental
animals, but its role in human disease is undefined (Quinn et al.
1980).
Ascaris lumbricoides, the large roundworm, produces numerous eggs,
which require 1-3 weeks for embryonation. After the embryonated eggs
are Ingested, they hatch in the intest'lne, enter the Intestinal wall,
migrate through the circulatory system to the lungs, enter the alveoli,
and migrate up to the pharynx. During their passage through the lungs
they may produce ascaris pneumonitis, or Loeffler's syndrome, consisting
of coughing, chest pain, shortness of breath, fever, and eosinophilia,
which can be especially severe in children. The larval worms are then
swallowed, to complete their maturation 1n the small Intestine, where
small numbers of worms usually produce no symptoms. Large numbers of
worms may cause digestive and nutritional disturbances, abdominal pain,
vomiting, restlessness, and disturbed sleep, or, occasionally, intesti-
nal obstruction. Oeath due to migration of adult worms into the liver,
gall bladder, peritoneal cavity, or appendix occurs infrequently. The
prevalence of ascariasis 1n the U.S. was estimated to be about 4 million
in 1972 (Warren, 1974).
Ascaris suum, the swine roundworm, may produce Loeffler's syndrome,
but probably does not complete Its life cycle in man (Phi lis et al.,
1972).
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Trichuris trichiura, the human whipworm, lives in the large
intestine with the anterior portion of its body threaded superficially
through the mucosa. Eggs are passed in the feces, and develop to the
infective stage after about four weeks in the soil (Reimers et al.,
1980), and direct infections of the cecum and proximal colon result Trom
the ingestion of infective eggs. Light infections are often asymp-
tomatic, but heavy infections may cause intermittent abdominal pain,
bloody stools, diarrhea, anemia, loss of weight, or rectal prolapse in
very heavy infections. Human infections with T^. suis, the swine whip-
worm, and T. vulpis, the dog whipworm, have been reported, but are
uncommon (Reimers et a]_., 1980). The prevalence of trichuriasis in the
U.S. was estimated to be about 2.2 million in 1 972 (Warren, 1974).
Reimers et^ al. (1980) have found Ascaris, Trichuris, and Toxocara to be
the most frequently recovered helminth eggs in municipal wastewater
sludge in southeastern United States,
Necator americanus and Ancylostoma duodenale, the human hookworms,
live in the small intestine attached to the intestinal wall. Eggs are
passed in the feces, and develop to the infective stage in 7-10 days in
warm, moist soil. Larvae penetrate bare skin, usually of the foot
(although flncylostoma may also be acquired by the oral route), pass
through the lymphatics and blood stream to the lungs, enter the alveoli,
migrate up the pharynx, are swallowed, and reach the small intestine.
During lung migration, a pneumonitis, similar to that produced by
Ascaris, may occur (Benenson, 1975). Light infections usually result in
few clinical effects, but heavy infections may result in iron-deficiency
anemia (because of the secreted anticoagulant causing bleeding at the
site of attachment) and debility, especially in children and pregnant
women. The prevalence of hookworm in the U.S. (usually due to Necator)
was estimated to be about 700,000 in 1972 (Warren, 1974).
Ancylostoma brazillense and A. canlnum, the cat and dog hookworms,
do not live in the human intestinal tract. Larvae from eggs in cat and
dog feces penetrate bare skin, particularly feet and legs on beaches,
and burrow aimlessly intracutaneously, producing "cutaneous larva
migrans" or "creeping eruption." After several weeks or months the
larva dies without completing Its life cycle.
Strongyloses stercoral 1s, the threadworm, lives in the mucosa of
the upper small Tntestlne. Tggs hatch within the intestine, and rein-
fection may occur, but usually noninfectlve larvae pass out in the
feces. The larva in the soil may develop Into an Infective stage or a
free-Hv1ng adult, which can produce Infective larvae. The infective
larvae penetrate the skin, usually of the foot, and complete their life
cycle similarly to hookworms. Intestinal symptoms Include abdominal
pain, nausea, weight loss, vomiting, diarrhea, weakness, and constipa-
tion. Massive infection and autolnfectlon may lead to wasting and death
1n patients receiving immunosuppressive medication (Benenson, 1975).
The prevalence of strongyloidiasis 1n the U.S. was estimated to be about
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An Overview of Public Health Fffects
Page 357
400,000 in 1972 (Warren, 1974). Dog feces is another source of thread-
worm larvae.
Toxocara canls and T. cat1, the dog and cat roundworms, do not live
in the human Intestinal tract. When eggs from animal feces are Ingested
by man, particularly children, the larvae hatch tn the intestine and
enter the intestinal wall, similarly to Ascaris. However, since
Toxocara cannot complete Its life cycle, the larvae do not migrate to
the pharynx, but instead wander aimlessly through the tissues, producing
"visceral larva migrans," until they die 1n several months to a year.
The disease may cause fever, appetite loss, cough, asthmatic episodes,
abdominal discomfort, muscle aches, or neurological symptoms, and may be
particularly serious 1f the liver, lungs, eyes (often resulting 1n
blindness), brain, heart, or kidneys become Involved (Flennes, 1978).
The infection rate of _T. canls 1s more tharf 50% in puppies and about 20%
in older dogs in the U.S. {Gunt>y, 1979), and Toxocara is one of the most
common helminth eggs In wastewater sludge (Reimers et al., 1980).
Taenia saglnata and T. solium, the beef and pork tapeworms, live In
the intestinal tract, where €Fey may cause nervousness, Insomnia,
anorexia, loss of weight, abdominal pain, and digestive disturbances, or
be asymptomatic. The infection arises from eating incompletely cooked
meat (of the Intermediate host) containing the larval stage of the
tapeworm, the cysticercus, however, rather than from a wastewater-
contaminated material. Man serves as the definitive host, harboring the
self-fertile adult. The eggs (contained in proglottlds) are passed 1n
the feces, ingested by cattle and pigs (the Intermediate hosts), hatch,
and the larvae migrate Into tissues, where they develop to the cysticer-
cus stage. The hazard, then, Is principally to livestock grazing on
land-treatment sites. The major direct hazard to man 1s the possibility
of his acting as the intermediate host. While Taenia saglnata eggs are
not infective for man, those of T. sol 1 urn are infective for man, in
which they can produce cysticercl, Cyst1cercos1s can present serious
symptoms when the larvae localize In the ear, eye, central nervous
system, or heart. Taenlasls with Taenia solium 1s rare 1n the U.S. and
with T. saglnata is only occasionally foumH However, human Infections
with Itiese tapeworms are fairly common in some other areas of the world.
Hymenolepis nana, the dwarf tapeworm, lives in the human intestinal
tract, where 1t may be asymptomatic or produce the same symptoms as
Taenia. Infective eggs are released, and Internal autolnfectlon may
occur, or more usually, eggs may be passed 1n the feces. No Inter-
mediate host 1s required, and upon Ingestion, eggs develop into adults
In the Intestinal tract. The prevalence of Infection in southern U.S.
1s 0.3 to 2.9 percent, mostly among children under 15.
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Echinococcus granulosus and E. multilocularis, two dog tapeworms,
do not live 1n the human intestinal tract. Dogs and other carnivores
are their definitive hosts. Eggs in animal feces are usually ingested
bv an herbivore, in which they hatch Into larval forms, which migrate
into tissues, where they develop into hydatid cysts. When the herbivore
is eaten by a carnivore the cysts develop into adult tapeworms in the
carnivore's intestinal tract. If man Ingests an egg, he can play the
role of the herbivore, just as in cysticercosls. A hydatid cyst can
develop in the liver, lungs, or other organs, where serious symptoms can
be produced as the cyst grows in size or ruptures. The disease 1s rare
in the U.S., but has been reported from the western states, Alaska, and
Canada, particularly where dogs are used to herd grazing animals, and
where dogs are fed animal offal.
The presence and levels 1n wastewater of any of these helminth eggs
or of those from animal feces (Ancylostoma, Toxocara, and Echinococcus),
depend on the levels of disease in the contributing population, and the
degree of animal contribution to the system. Since helminth eggs are
denser than water, most will settle to the bottom during a sedimentation
unit process, and primary effluent should have fairly low densities of
eggs. As a consequence, sludge will have high densities of viable
helminth eggs, and will require either proper treatment before land
application, or use under conditions that minimize exposure.
Helminths: Potential Exposure
As with protozoa, the large size of helminth eggs makes 1t unlikely
that they will find their way Into either aerosols or groundwater at
land application sites.
Helminth eggs and larvae, 1n contrast to protozoan cysts, live for
long periods of time when applied to the land, probably because soil Is
the transmission medium for which they have evolved, while protozoa have
evolved toward water transmission. Thus, under favorable conditions of
moisture, temperature, and sunlight, Ascaris, Trichurls, and Toxocara
can remain viable and Infective for several years Jlittlej 1980).
Hookworms can survive up to six months (Feachem et al., 1978), and
Taenia a few days to seven months (Babayeva, 1966); a£fie"r~helm1 nths sur-
vlve for shorter periods.
Because of desiccation and exposure to sunlight, helmfnth eggs
deposited on plant surfaces die off more rapidly. Thus, Rudolfs et al.
(1951c) found Ascaris eggs, the longest-lived helminth egg, sprayetTon
tomatoes and lettuce, to be completely degenerated after 27-35 days.
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Aft Overview of Public Health Effects
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At rap1d-inf1ltratlon land treatment sites there should be little
risk to public health from helminths, as long as the site 1s dedicated
to rapid infiltration. However, because of the growth of crops and pre-
sence of people at sTow-rate, overland flow, and sludge application
sites, and the longevity of helminth eggs, it might be advisable to
select a preapplication treatment method which will completely remove or
inactivate helminth eggs. From a less conservative point of view,
Fitzgerald (1979) reviewed the potential Impact on public health of
parasites 1n soil/sludge systems, concluding that the proper utilization
of wastewater sludge did not pose any great threat to the health of
society through actual transmission of pathogens that might be present
1n sludge.
Helminths: Effects on Animals
The most serious threat to cattle at land application sites is the
beef tapeworm, Taenia saginata (Feachem et^ aj_., 1978; WHO, 1981). The
increased incidence of cystlcercosls 1n cattle results 1n economic
losses (because of condemnation of carcasses), as well as Increased
Incidence of disease 1n man. The application of wastewater sludge to
pastures has resulted in outbreaks of cystlcercosls 1n grazing cattle in
England (Macpherson et^al., 1978, 1979), but wastewater land treatment
sites at San Angelo, "Texas (Weaver et al., 1978), and Melbourne,
Australia (Croxford, 1978; McPherson, 1D75]", have resulted 1n no in-
crease of cysticercosls in grazing cattle.
Nevertheless, because of the longevity of helminth eggs 1n the
soil, and the fact that cattle consume considerable quantities of soil
as they graze 1t, 1t would be prudent to select a pretreatment method
which will completely remove helminth eggs at land application sites
where cattle are allowed to graze. Arundel and Adolph (1980) have
suggested that stabilization ponds remove Taenia saginata quite effi-
ciently. They found no cystlcercosls 1n cattle grazed on pasture Irri-
gated with effluent from lagoonlng, compared with a 3.3% infection rate
from trickling filter effluent, 9.0-12.5% from activated sludge
effluent, and 30.0% from raw sewage.
Helminths: Infective Dose, Risk of Infection, and Epidemiology
Single eggs of helminths are Infectious to man, although since the
symptoms of helminth Infections are dose-related, many light Infections
are asymptomatic. However, Ascarls infection may sensitize Individuals
so that the passage of a single larval stage through the lungs may
result 1n allergic symptoms, I.e., asthma and urticaria (MUller, 1953).
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Because of the Tow infective doses of helminth eggs, and their
longevity, it would be prudent for humans to maintain a minimum amount
of contact with an active or inactive land application site, unless the
wastewater or sludge has been pretreated to remove or inactivate
helminths.
A few epidemiological reports have linked the transmission of
Ascaris and hookworm to the use of night soil on gardens and small farms
in Europe and the Orient (Geldreich and Bordner, 1971).
PATHOGENS: CONCLUSIONS AND RESEARCH NEEDS
The level of preapplication treatment required for the protection
of public health may be as little as properly-designed sedimentation at
land treatment sites with limited public access, where crops are pro-
tected by appropriate crop choice and waiting periods, and groundwater
is protected by appropriate hydrological studies and selection of appli-
cation rate. Where protection of groundwater cannot be assured,
wastewater stabilization ponds should be considered for virus removal.
Because of potential contamination of crops and infection of animals,
complete removal of helminth eggs should be considered for slow-rate
Irrigation and sludge application sites. These relatively simple pre-
treatment requirements would be appropriate for many land treatment
systems in the United States, e.g., for many slow-rate sites where crops
for animal feed are grown. Pretreatment elimination of helminths from
sludge is less simple, however.
This appraisal assumes only a minimum level of preapplication
treatment for wastewater, i.e., properly-designed sedimentation. In
situations with greater public access (e.g., water disposal on golf
courses), shorter waiting periods before grazing or harvest of crops
{e.g., agriculture in arid areas), or threat of groundwater con-
tamination (e.g., shallow water table), more extensive preapplication
treatment may be required. This treatment may consist of wastewater
stabfllzatton ponds, conventional treatment unit processes, or even
disinfection. The exact degree of pretreatment required for these
situations Is site-specific, and recommendations should be determined
separately for each system.
Because of the potential exposure to aerosolized viruses at land
treatment sites, 1t would be prudent to limit public access to 100-200 m
from a spray source. At this distance bacteria are also unlikely to
pose a significant risk. Human exposure to pathogenic protozoa or
helminth eggs through aerosols 1s unlikely.
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An Overview of Public Health Effects
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Suppression of aerosol formation by the use of downward-directed,
low-pressure nozzles, rldge-and-furrow irrigation, or drip irrigation is
recommended where these application techniques are feasible. An impor-
tant research need in this area 1s the comparison of the respiratory
infective dose of enteric viruses with the oral infective dose.
The survival times of pathogens on soil and plants are summarized
as follows. Since pathogens survive for a much longer time on soil than
plants, the tentatively recommended waiting periods before harvest are
based upon probable contamination with soil. What is a safe waiting
period before crop harvest for human consumption 1s really an unsettled
issue, and represents an important research need.
Soil Plants
Pathogens
Absolute
Maximum
Common
Maximum
Absolute
Maximum
Common
Maximum
Bacterl a
1 year
2 months
6 months
1 month
VI ruses
6 months
3 months
2 months
1 month
Protozoa
10 days
2 days
5 days
2 days
Helminths
7 years
2 years
5 months
1 month
Aerial crops with little chance for contact with soil should not be
harvested for human consumption for at least one month after the last
wastewater or sludge application; subsurface and low-growing crops for
human consumption should not be grown at a land application site for at
least six months after last application. These waiting periods need not
apply to the growth of crops for animal feed, however.
Properly designed slow-rate land treatment and sludge application
sites probably pose little threat of bacterial or viral contamination of
groundwater.
Considerable threat of bacterial contamination exists, however, at
rapid-infiltration sites where the water table 1s shallow, particularly
if the soil is porous. Likewise, considerable potential for viral con-
tamination of groundwater exists at rap1d-1nf1ltrat1on sites, and
appropriate preappl1 cation treatment or management techniques should be
instituted, e.g., Intermittent application of wastewater. Until then,
groundwater drawn for use as potable water supplies should be disin-
fected. The factors controlling the passage of viruses through the soil
Into the groundwater, especially at rapid Infiltration sites, 1s an
important research area.
Human exposure to pathogenic protozoa or helminths through ground-
water 1s unlikely.
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There appears to be little danger of bacterial, viral, or protozoal
disease to animals grazing at land treatment sites if grazing does not
resume until four weeks after application. The risk to animal health
from pathogens in sludge also is probably small (Yeager, 1980), but the
issue is not settled. Removal of helminth eggs during preapplication
treatment of wastewater should eliminate the potential of disease from
those long-lived parasites, but the need for complete 1nact1vation of
helminths in sludge before land application is a research issue.
Because of the possibility of picking up an infection, 1t would be
wise for humans to maintain a minimum amount of contact with an active
land application site.
Epidemiological studies to date suggest little effect of land
treatment on disease incidence. However, well planned and Implemented
prospective studies have not been completed, and many questions on the
public health consequences of land application of wastewater and sludge
remain (Larkin, 1982).
Research needs include the role of animals at land application
sites in transmitting human diseases to animals or man off-site.
Moreover, well-planned and funded prospective acute disease epidemiolo-
gical studies at land treatment and sludge application sites involving a
large number of exposed people should be completed.
ORGANICS
The potential health effects of toxic organic compounds are n\yr1ad.
Systems affected range from the dermatological to the nervous to the
subcellular, and effects produced range from rash to motor dysfunction
to cancer. The degree of toxicity of organic compounds varies widely,
from essentially harmless (e.g., most carbohydrates) to moderately toxic
(e.g., most alcohols) to extremely toxic (e.g., dioxins).
A glance at the current edition of the Merck Index will reveal that
the number of organic compounds described thus far is almost unfatho-
mable. Almost any of these may appear 1n wastewater, depending upon its
sources. Thus the discussion below must perforce be rather general, and
the presence of any particular toxic organic in high concentration in
wastewater or sludge may require a site-specific evaluation of potential
health effects.
Most common organlcs 1n domestic wastewater derive from feces,
urine, paper products, food wastes, detergents, and skin excretions and
contaminants (from bathing). In medium-strength sewage (700 ppm total
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An Overview ol Public Health Effects
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solids content) organics make up about 75% of the suspended solids and
about 40% of the filterable solids (colloidal and dissolved), consisting
primarily of proteins (40-60?,), carbohydrates (25-50%), and fats and
oils (10%) (Metcalf and Eddy, 1972). After secondary treatment the more
refractory and hi gh-tnolecular weight organics predominate, e.g., fulvic
acid, humic acid, and hymathomelanic acid (Chang and Page, 1978). In
general, however, the chemical nature of domestic wastewater remains
poorly characterized.
Although most of the organics found in domestic wastewater are pro-
bably harmless in a land application context, it has recently been found
that fecal material itself commonly contains mutagens. Thus there 1s
evidence that one of the causes of colorectal cancer 1s the presence of
carcinogens or co-carcinogens produced by the bacterial degradation 1n
the gut of bile acids or cholesterol (Thornton, 1981). The mutagenicity
of feces can be increased by anaerobic Incubation and by the presence of
bile and bile acids (Van Tassell et aU, 1982), and is lower in vege-
tarians than non-vegetarians (KuhnTein et al., 1981). High levels of
chromosome-breaking mutagenic activity have~a1so been found in the feces
of animals--dog, otter, gull, cow, horse, sheep, chicken, and goose
(Stich et al., 1980). The chemical nature of the fecal mutagens 1s
unknown. IrTthe case of the latter animal mutagens, evidence suggests
that at least part of the mutagenic action Is due to hydrogen peroxide
and the ensuing radicals which can be formed during oxidation of many
organlc compounds.
Ten domestic and industrial secondary effluents in Illinois were
recently examined for mutagenicity by Johnston et al. (1982) with the
results that all 10 effluents assayed showed significant mutagenicity.
Mutagenic activity per unit volume of effluent varied over a 4,500-fold
range, and toxicity varied over a 120-fold range. Selective extraction
of whole effluents appeared to unmask mutagenic activity, probably by
separating mutagens and substances that interfere with the mutagen
assay. In several effluents there was evidence of several mutagenic
compounds present, and it appeared that the mutagens were predominantly
nonpolar, neutral compounds. There was no obvious influence of disin-
fection by chlorlnation on the effluent mutagenicity, in spite of the
fact that one would expect many mutagens to be formed by the action of
chlorine on humic substances and other organics found 1n wastewater.
Mutagenicity likewise has been observed in urban sludge (Hopke et
aU, 1982). ~
The major contributors of toxic organics to municipal wastewaters
are usually assumed to be Industrial discharges. However, household
wastewater discharge may represent an important contributor since many
consumer products in daily use contain toxic substances. A recent study
(Hathaway, 1980) Identified consumer products containing toxic compounds
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on EPA's list of 129 priority pollutants, which may eventually end up 1n
wastewaters. The most frequently used products are cleaning agents and
cosmetics, containing solvents and heavy metals as main ingredients.
Next are deoderizers and disinfectants, containing naphthalene, phenol,
and chlorophenols. Discarded into wastewater infrequently, but in large
volumes, are pesticides, laundry products, paint products, polishes, and
preservatives. The organic priority pollutants most frequently used and
discharged into domestic wastewater were predicted to be the following:
benzene naphthalene
phenol toluene
2,4,6-trichlorophenol d1ethylphthalate
2-chlorophenol dlmethylphthalate
1,2-dichlorobenzene trlchloroethylene
1,4-dichlorobenzene aldrin
1,1,l-tr1chloroethane dieldrin
Thus many of the toxic organlcs, including mutagens (or potential
carcinogens), to be found in wastewater and sludge come from within our
own homes or even within our own bodies. This should be kept in mind
when evaluating the public health effects of land application. The
broad range of concentrations of toxic organics detected 1n municipal
wastewaters and sludges (e.g., in the recent surveys of DeWalle et al.
(1981) and Feller (1980), however, suggests that wastewater or sTulJge
applied to land should be regularly monitored for toxic organlcs. This
measure 1s emphasized by the occasional discharge of toxic substances
Into municipal wastewater systems with resulting medical effects 1n
treatment plant workers, such as the recent hexachlorocyclopentadlene
episode 1n Louisville, Kentucky (Komi nsky et aj_,, 19R0).
ORGANICS: Potential Exposure and Health Effects
While most of the nonvolatile organlcs 1n wastewater at a land
treatment site would be expected to enter the soil, much of the volatile
organics would probably be released to the air. The fraction entering
the air would depend, of course, upon the processes, detention time, and
application rates used at a particular facility. Although some of the
volatile organlcs (and nonvolatile organlcs) may be released 1n the form
of true aerosols, most would be expected to be released as gases by eva-
poration (volatilization).
At the Muskegon slow-rate land treatment system, the behavior of
four of the most common toxic organlcs has been studied (Clark et a 1.,
1981): trichloroethane, trlchloroethylene, tetrachloroethylene, and
chloroform (trichloromethane). Air stripping 1n the aerated lagoons was
shown to be significant for these compounds. The maximum concentrations
1n air, together with the associated wastewater concentrations, of these
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An Overview of Pubi.c Health Effects
Page 365
compounds immediately downwind from the aerated lagoons and spray Irri-
gation rigs are shown 1n Table 9. All of these air concentrations are
well below the 8-hour occupational standards of 45,000 pg/m3, 535,000
pg/m3, 670,000 yg/m3, and 50,000 ug/m3, respectively (ACHH, 1979).
Table 9. Air and wastewater concentrations at Muskegon Land Treatment
System
Aerated Lagoons Spray Irrigation Rigs
Wastewater
Ai r
Wastewater
A1 r
(ug/i)
(v»g/m3)
(ug/i)
Trichloroethane
ND*
90
3
2.7
TMchloroethylene
118
73
68
9.3
Tetrachloroethylene
8.9
46
40
8.6
Chloroform
480
202
ND
*ND = not detected (<0.1 yg/1)
Comparison of the wastewater concentrations in Table 9 with the
maximum values found 1n recent surveys of municipal wastewaters (DeWalle
et^al., 1981; Feiler, 1980) suggests that an increase of three orders of
magnTtude over the Muskegon values 1s the maximum that would ever be
likely to occur. Even such an Increase would probably still result 1n
acceptable air concentrations.
Organic compounds in wastewater may be volatilized, Immobilized by
adsorption, or transported through the soil column, possibly to reach
the groundwater. Adsorbed organlcs may be subsequently chemically or
photochemically degraded, mlcroblally decomposed, or desorbed. In view
of the multitudinous variety of organic compounds existing, 1t 1s dif-
ficult to generalize about their biodegradatlon in soil. It appears,
however, that most organlcs do become mlcroblally decomposed 1n the
soil, at least to some extent. This 1s especially true of naturally-
occurring compounds, or those resembling them, because of the eons of
evolution that have developed microbial enzyme systems to do the job.
The more structurally complex the molecule Is, e.g., condensed rings or
dense branching, and more halogenated 1t 1s, the more difficult 1s
biodegradatlon.
It has recently been found that 1t might be possible for car-
cinogenic and teratogenic nitrosamines to be formed from secondary and
tertiary amines at land treatment sites. Thus, Thomas and Alexander
(1981) have shown that dlmethyl ami ne and trimethyl amine can be formed in
municipal wastewater from naturally-occurring precursors. D1methylam1ne
may then go on to be mlcroblally nltrosated, forming N-n1trosodimethyl-
amlne, a process which can occur under conditions resembling land
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treatment of wastewater (Greene et al.f 1981). Whether this actually
occurs under field conditions, resulting 1n a threat to groundwater, 1s
unknown.
Data on the transport of organics to groundwater have been pre-
sented by Bouwer and Rice (1978) and Tomson et al. (1981) for rapid
infiltration sites, and by Jenkins and Palazzo~[l§FI) and Demlrjlan et
al. (1981) for slow rate sites. From these data it is evident thaF
toxic organics can be transported to groundwater below land treatment
sites, although the degree can be controlled by the level of preapplica-
tion treatment and application rate as well as choice of effluent and
site characteristics. This certainly is cause for concern, but 1t
should be kept 1n mind that groundwater is not the pristine substance It
was once thought to be (Burmaster, 1982). The synthetic organic com-
pounds most commonly found in groundwater in the U.S., deriving pri-
marily from industrial wastes, are (Environmental Health Letter 21(6):7.
1982):
Some biodegradation of organics occurs in groundwater (Gerba and
McNabb, 1981), but it 1s difficult to avoid the conclusion that once
toxic organics get into the groundwater they will remain there for a
long time.
At the low concentrations found 1n the soil at land application
sites, very few organic compounds are likely to be toxic to plants.
These plants, although not injured themselves, may accumulate organics
that may be toxic to the animals to which they are fed or to humans who
use them as food, either directly or through animal products. The
sparse data that exist thus far, e.g., that at Muskegon (Demlrjlan et
al., 1981), however, suggest that plant uptake may be of little slgnlfT^
cance. Under certain s1te-spec1f1c conditions, however, high con-
centrations of particular organics In the wastewater or sludge may cause
problems. For example, PCBs 1n cabbage grown on sludge-amended soil
have probably cat; 'd degenerative changes In liver and thyroid of sheep
(Klenholz, 1980), and one can extrapolate a similar phenomenon to a land
treatment site.
Hansen et al. (1976) studied young swine fed for 56 days on corn
grown on slulfije^TertlUzed land. It was essentially a negative study:
electroencephalograms, electrocardiograms, clinical chemistry, and
tri chloroethylene
tetrachloroethylene
carbon tetrachloride
1,1,1-trichloroethane
1,2-dichloroethane
vinyl chloride
methylene chloride
benzene
chlorobenzene
dichlorobenzene
tri chlorobenzene
l,l-d1chloroethylene
c1s-l,2-d1chloroethylene
trans-1,2-dichloroethylene
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An Overview of Pubic Hoallh F"!f(>cts
Page 367
histopathology were all normal. However, they observed elevated levels
of hepatic microsomal mixed function oxidase (MFO) activity in the swine
fed sludge-fertilized corn. Associated with this were non-statistically
significant increased Hver weights. Other liver enzymes (alkaline
phosphatase and lactate dehydrogenase) were normal. This increased MFO
activity may be caused bv toxic organics, metals, or be of no signifi-
cance, but the authors concluded that further study should be performed
before such grain can be recommended as the major dietary component for
animals over long periods.
Similar results were found by Telford et al. (1982), who examined
sheep fed silage corn grown on soil amended-wftfi municipal sludge at a
high rate (224 t/ha). The sheep had significantly higher hepatic micro-
somal p-nitroanisole O-demethylase activity than controls, but no muta-
genic responses for animal feed or feces, and no histopathologlcal
effects. In contrast, the same research group (Lisk et £l_., 1982) found
no hepatic microsomal MFO response In swine fed corn grown on high-rate
sludge-amended soil. Liver:body weight ratios, corn, feces, and urine
mutagenicity, and histopathology were also unremarkable, suggesting
absence or low levels of organic toxicants in the corn.
Studies at New Mexico State University (Smith, 1982), involving
feeding of sludges to rats, sheep, and cattle, indicate no hazard from
toxicants, based on uptake, MFO activity, and histopathology.
A more serious route of exposure by animals to toxic organics is
the soil Itself. Most grazing animals Ingest a certain amount of soil
together with their food plants. Thus dairy cows may Ingest 100-500 kg
of soil per year, with an average of about 200-300 kg/hr; expressed 1n
other terms, dairy cows may consume soil up to 14% of dry matter Intake
when available forage is low and no supplemental feed is used (Kienholz,
1980; Fries, 1980), Lipophilic organics present 1n the soil may con-
centrate in animal fat. For example, feeding experiments with PC8s
indicate that the steady-state milk fat concentratlons are about five
times the diet concentrations, which could result 1n milk fat levels of
0.7 ppm for each 1 ppm of PCBs fn surface soil (Fries, 1980}. Body fat
levels would be expected to be similar. In a study of the pasture
application of wastewater sludge with a high textile Industry component,
deHaan (1977) found 1,2 ppm of dleldrln (almost 19 times the acceptable
level 1n The Netherlands) In the milk of grazing cows.
Turning to humans, Baker et al., (1980) described the metabolic
consequences of exposure to hTgh levels of PCBs from contaminated
wastewater sludge used as a soil amendment 1n Bloomlngton, Indiana. No
skin or systemic symptoms were noted, and of the hematologic, hepatic,
and renal functions measured, only serum triglyceride levels increased,
suggesting altered lipid metabolism. Serum PCB levels were normal.
Naylor and Loehr (1982) have recently performed a detailed toxlcologlcal
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KOWAL
analysis of the potential human health risks of the consumption of
sludge-contaminated soils and crops associated with organic priority
pollutants. They concluded that land application of sludge 1s not
likely to result 1n the ingestion of amounts of organic priority pollu-
tants exceeding the acceptable daily dose.
At the Whlttier Narrows groundwater recharge project, secondary and
tertiary effluent has been infiltrated into the Montebello Forebay area
of Los Angeles County since 1962 (Nellor (it aK, 19R2), resulting in
long-term average exposures to humans of up to 11% reclaimed water in
groundwater. Monitoring and epidemiological studies demonstrated that
the recharge operation has not resulted in any adverse impact on the
area's groundwater or the health of the population drinking the water.
Organlcs: Conclusions and Research Needs
The tremendous number of organic compounds possibly present in
wastewater and sludge, together with their myriad health effects and
poorly understood behavior in the environment, represent a considerable
potential for adverse health effects. Most of these can probably be
prevented by simple design and monitoring measures; this, of course,
would not be true 1n the case of high discharges of particular chemi-
cals.
Although removal rates of organlcs-from wastewater by aerosoliza-
tion and volatilization are high, exposure through this route 1s unli-
kely to present any significant health effect.
Toxic organics can enter the groundwater, particularly at rapid
infiltration sites, and the application and soil factors controlling
this transport, together with the factors governing their movement and
decomposition within groundwater, are significant research needs.
The levels of toxic organics likely to be present 1n soils at land
application sites will probably result in extremely low levels In above-
ground portions of plants, but levels 1n roots, tubers, and bulbs may
present a health hazard. The feeding of land application site-grown
plants to animals Is unlikely to pose a health problem, but grazing ani-
mals may accumulate significant levels of toxic organics. The issue of
accumulation of organics from the soil by plants and animals
(particularly into milk), and into the human food supply, 1s poorly
understood, and more research is required.
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Ad Overview of Public Health Effects
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TRACE ELEMENTS
The trace elements (including the "heavy metals") of public health
concern in wastewater and sludge, i.e., those for which primary drinking
water standards (U.S. EPA, 1977) exist (but excluding silver- since its
effect is largely cosmetic), are:
Of these, cadmium, lead, and mercury are usually regarded as of most
concern, and barium of minor concern. Chromium and selenium are essen-
tial elements 1n man; arsenic and cadmium have been tentatively shown to
be essential to experimental animals, and thus may be essential to man
as well (National Research Council, 1980). Secondary drinking water
standards (U.S. EPA, 1979), i.e., those related to aesthetic quality,
also exist for copper, Iron, manganese, and zinc. These latter ele-
ments, as well as all other trace elements, are toxic 1f Ingested or
Inhaled at high levels for long periods (Underwood, 1977), but this fact
does not warrant considering them 1n the land application context, where
low levels are expected.
Arsenic 1s popularly known as an acute poison, but chronic human
exposure to low doses, as might be expected for all trace elements as a
result of land application, may cause weakness, prostration, muscular
aching, skin and mucosal changes, peripheral neuropathy, and linear
pigmentation 1n the fingernails. Chronic arsenic Intoxication may
result 1n headache, drowsiness, confusion, and convulsions (Underwood,
1977). Epidemiological evidence has Implicated arsenic as a carcinogen,
but there 1s little evidence that arsenic compounds are carcinogenic in
experimental animals (Sunderman, 1977). Even with high concentrations
1n soil, however, plants rarely take up enough of the element to con-
stitute a risk to human health (Underwood, 1977; Council for
Agricultural Science and Technology, 1976).
Barium has a low degree of toxicity by the oral route. Because of
its effect of intensely stimulating smooth, striated, and cardiac muscle
1n acute exposure, however, 1t may have cardiovascular effects 1n low
doses, but this has not thus far been demonstrated (Brennlman et al.,
1979).
Primary Drinking Water Standards
M/1_)
0.05
1.0
0.010
0.05
0.05
0.002
0.01
Arsenic (As)
Barium (Ba)
Cadmium (Cd)
Chromium (Cr)
Lead (Pb)
Mercury (Hg)
Selenium (Se)
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Cadmium is widely regarded as the trace element of most concern
from a human health effect viewpoint in the land application of sludge,
and this status probably carries over into the land treatment of
wastewater as well. The critical health effect of chronic environmental
exposure via ingestion is renal tubular damage due to accumulation of
cadmium in the kidney. The initial consequence of this damage is the
loss of low molecular weight serum proteins in the urine, followed by
loss of other proteins, glucose, amino acids, calcium, and phosphate.
This kidney damage is often irreversible and constitutes a significant
adverse health effect (Ryan et al., 1982). There is evidence that the
absorption and/or toxicity of-ca"3mium are antagonized by zinc, selenium,
iron, and calcium (Sandstead, 1977). The carcinogenicity of cadmium 1s
controversial; the epidemiological evidence is tenuous, and the experi-
mental evidence is conflicting (Ryan et aj[., 1982).
Chromium is much more toxic in its hexavalent form than its triva-
lent form, its predominant state in wastewater and soil. Chronic and
exposure in experimental animals has been associated with growth
depression, and liver and kidney damage (Underwood, 1977). Hexavalent
chromium causes respiratory cancer upon chronic exposure to chromate
dust (Sundermann, 1977). Most crops absorb relatively little chromium
from the soil (Council for Agricultural Science and Technology, 1976).
Lead chronic toxicity is characterized by neurological defects,
renal tubular dysfunction, and anemia. Damage to the central nervous
system is common, especially in children, who have low lead tolerance,
resulting in physical brain damage, behavioral problems, Intellectual
Impairment, and hyperactivity. At soil pH above 5.5 and high labile
phosphorus content, common conditions at a land application site, little
movement of lead from the soil into plant tops and seed would be
expected (Council for Agricultural Science and Technology, 1976;
Stewart, 1979).
Mercury 1n low levels can result In neurological symptoms such as
tremors, vertigo, irritability, and depression, as well as salivation,
stomatitis, and diarrhea. Mercury can enter plants through the roots
and appears to be readily translocated throughout the plant (Council for
Agricultural Science and Technology, 1976), although there 1s some
contrary evidence (Stewart, 1979).
Selenium exposure 1n its chronic form 1s associated with dental
carles, jaundice, sk 1 n eruptions, chronic arthritis, abnormal flnger-
and toenails, and subcutaneous edema. It has also been found to have an
Inhibitory effect against several types of cancer (F1shbe1n, 1977).
Selenium 1s readily taken up by plants and passed onto animals, and has
caused toxicity in livestock in h1gh-selen1um soils (Council for
Agricultural Science and Technology, 1976; Underwood, 1977).
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An Overview ot Public Health Effects
Page 371
Comparison of the ranges of levels of trace elements in untreated
municipal wastewater in the U.S. (U.S. EPA, 1981; Feller, 1980) with
recommended irrigation water quality criteria (NAS-NAE, 1972) suggests
that the trace elements in wastewater most likely to violate agri-
cultural irrigation criteria are cadmium and chromium. The high levels
of these two elements found in certain municipal wastewaters are
doubtlessly due to industrial sources, for example, electroplating
operations. Since chromium is poorly absorbed from the soil by crops,
cadmium is probably the element of most public health concern.
Trace Elements: Potential Exposure
Cadmium 1s probably the element most likely to restrict the use of
wastewater or sludge 1n land application where crops are grown for human
consumption. In the case of crops not for human consumption, other ele-
ments may be limiting, for example, molybdenum because of its toxicity
to livestock, and nickel because of its phytotoxlcity (Page and Chang,
1981).
Trace elements, of course, are conservative materials, in contrast
to pathogens and organlcs, which may become Inactivated and decomposed.
Thus, one would expect cadmium to build up in the soil at a land appli-
cation site. Our major hope, from a health effects point of view, 1s
that 1t will become immobilized 1n the soil, and be less available for
plant uptake as time passes. There is some suggestion of this In
Hlnesly's data (Hlnesly et al., 1979) on cadmium content of corn grain
and leaves, grown during ancTafter the termination of wastewater sludge
application. The Issues of cadmium uptake by plants often annual vs.
cumulative application limits, and the effect of discontinuing applica-
tion remain unsettled, however (Ryan et aK, 1982).
Exposure of humans to trace elements through groundwater appears
unlikely at slow-rate land treatment sites. At slow-rate sites both 1n
New Hampshire (Jenkins and Palazzo, 1981) and Texas (Hossner et al.,
1978) trace elements in the wastewater became stabilized near tTfe sur-
face.
Rap1d-1nf1ltrat1on sites, in contrast, appear to present some
threat to groundwater. After 30 years of primary wastewater infiltra-
tion at the HolHster, California, site, concentrations 1n shallow
groundwater of cadmium (0.028 mg/1) and lead (0.09 mg/1) were above
drinking water standards, but arsenic, barium, chromium, mercury, and
selenium were below (Pound et al., 1978).
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KOWAi
Sludge application sites may tie up trace elements similarly to
slow rate treatment sites. Leachate from sludge-applied land in South
Africa regularly had cadmium concentrations below the drinking water
standard of 10 ug/1 (Nell et al., 1981).
Trace Elements: Accumulation in Animals
The examination of trace elements in cattle grazed on sludge-
amended pastures has revealed raised levels in liver and kidney, but not
in muscle tissue (Bertrand et al., 1981a). No increases were seen when
cattle were fed siudge-amen3e3~so11-grown forage sorghum {Bertrand et
al., 1981b). Trace element levels and disease conditions of cattlt
grazing on land reclaimed by Chicago sludge have been observed by
Fitzgerald (1978) for four years; it was concluded that little risk to
man or animals is associated with land application of anaerobically
digested wastewater sludge. Experience at Werlbee Farm in Melbourne,
Australia, where cattle are grazed on wastewater-1rrigated pastures, has
shown higher organ levels of cadmium and chromium than in farm cattle
grazed on non-irrigated pastures, but comparable to non-farm cattle
(Table 10). Organ levels of lead, however, did not increase, in spite
of increases in both soil and pasture plants.
Table 10. Toxic trace element concentrations in cattle liver and kidney
at Werribee Farm (ug/g dried tissue) (after Croxford, 1978)
Cadmfum
Chromium
Lead
Cattle Liver
Non-Farm
0.76
0.0B
0.5
Farm: Non-Irrigated
0.17
0.05
0.93
Farm: Irrigated
0.38
0.07
1.12
Cattle Kidney
Non-Farm
3.32
0.06
0.32
Farm: Non-Irrigated
1.24
0.05
2.24
Farm: Irrigated
2.07
0.07
1.41
Since trace elements accumulate 1n very small quantities In animal
muscle tissue, there is probably little concern about non-visceral meats
in the marketplace. Liver and kidneys of animals do, however, accumu-
late high levels of cadmium, just as they do in man, so that these meats
may be of concern to those people consuming large quantities of them.
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An Ovorviow ol Public Hoalth FHects
Page 373
Trace Elements: Human Accumulation of Cadmium and Health Effects
The significance of this concern with cadmium getting Into the
human food chain depends upon the cadmium levels presently existing in
human food, the total dietary intake of cadmium, and the potential
increase in cadmium levels in human food due to land application.
(Drinking water and ambient air contribute relatively little to total
daily cadmium intake (Pahren et aj_., 1979).)
The cadmium levels presently existing in human food can be esti-
mated, at least for the U.S., by data from the U.S. Food and Drug
Administration's Compliance Program ("market-basket survey"). These
levels, together with the calculated normal dietary intake and vege-
tarian dietary Intake of cadmium, are summarized 1n Table 11. It
should be noted that root and leafy vegetables have the highest con-
centrations of cadmium. More accurate estimates of cadmium (and other
trace element) concentrations 1n crops grown 1n the U.S., together with
concentrations in the soils 1n which they are growing, will be
available from a survey jointly supported by the U.S. EPA, U.S. FDA,
and U.S. Department of Agriculture. In this survey 6,000 crop samples
and 18,000 soil samples are being analyzed over a 4-year period, and
the results should be available in 1983.
The present total dietary intake of cadmium was estimated above to
be about 28 pg/day. Other estimates based on the market basket method
have resulted in higher values: 26-61 yg/day in 15-20-year-old U.S.
males, by the U.S. FDA, and 52 ug/day in Canadians (Klrkpatrick and
Coffin, 1977).
A more direct, and potentially more accurate, method of estimating
dietary intake of cadmium 1s by measuring the cadmium content of human
feces. This method 1s feasible because the absorption of cadmium from
the gut is low--rarely more than 10%, and usually 4-6%--and the excre-
tion of cadmium into the gut 1s also very low. A recent study, using
existing fecal cadmium data in Chicago and Dallas, and estimating dally
feces production, resulted 1n a final estimate of the average dally
Intake of cadmium 1n food for U.S. inhabitants of 13-16 yg/day (Kowal
et al., 1979). (Since the ingestion rate of the teenage male Is often
usetTln discussion of cadmium Intake, values of 24 pg/day, 19 ug/day,
and 18 yg/day for 10-19-year-old males from Chicago 1974, Chicago 1976,
and Dallas, respectlvely, were estimated.)
This estimate of the average dally intake of cadmium 1n food can
be compared with other estimates by the fecal analysis method, where
the dally feces production of each Individual was measured rather than
estimated. In Sweden rates of 16 pg/day 1n nonsmokers and 19 vg/day in
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KOWAL
Table 11. Cadmium concentration 1n foods and calculated dietary intake
(from Ryan et aU, 1982)
Food Classes
ppb Cda
Normal Diet
g/day ug Cd/day
Vegetari
g/day m
an D1etc
g Cd/day
Dairy products
5.7
549
3.1
584
3.3
Meat, fish, poultry
15.3
204
3.1
-
-
Grain and cereal products
23.2
331
7.7
203
4.7
Potatoes
48.0
138
6.6
43
2.1
Leafy vegetables
40.5
42
1.7
252
10.2
Legume vegetables
6.2
51
0.3
166
1.0
Root vegetables
32.3
25
0.8
Garden fruits
14.7
69
1.0
Fruits
3.0
173
0.5
284
0.8
Oils, fats, shortenings
15.3
56
0.9
107
1.6
Sugars and adjuncts
10.0
65
0.7
110
1.1
Beverages
3.0
534
1.6
600
1.8
2,237
28.0
2,349
26.6
aFrom FDA Compliance Program Evaluation 1974 Total Diet Studies
bAdjusted on a caloric basis from FDA 1974 Total Diet Studies to represent the
normal diet which compares with the adult lacto-ovo-vegetarlan diet.
cLoma Linda lacto-ovo-vegetarian diet. Based on response of 183 southern
Callfornians in a food frequency questionnaire by the Department of
B1ostatist1cs and Epidemiology, Loma Linda University School of Health,
1978. Leafy vegetables class Includes root vegetable and garden fruit
classes from normal diet.
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An Overview ol Puolir. Health Eltects
Page 375
smokers (former and present) have been reported (see Kowal et al.,
1 979, for references). The increased rate for smokers was partly
attributed to their increased food Intake. Nine ug/day fecal cadmium
has been measured in Sweden, compared with a value of 10 ug/day
measured by the total diet collection method. In Germany 31 pg/day has
been measured, compared with 48 ug/day measured by the market basket
method. In Japan, where cadmium levels in food are higher, the fecal
analysis method has resulted in several estimates ranging from 24
ug/day to 84 ug/day.
It has generally been concluded that ingestion of
200-350 Cd/day over a 50-year exposure period 1s a
reasonable estimate for individuals (excluding smokers and
occupationally exposed) within the population to reach the
critical renal concentration (200 pg Cd/g wet weight 1n
the renal cortex) associated with the Initiation of pro-
teinuria. This Ingestion limit assumes background expo-
sure levels of air and no exposure from smoking* If these
exposures are increased, then the suggested Ingestion
limit must be correspondingly reduced. Smoking one pack
of cigarettes/day will reduce the limit by about 25
yg/day. Again, these exposures are assumed to occur over
a 50-year exposure period and, 1n the case of cigarettes,
since many smokers start as teenagers, this addition would
be relevant for much (30 to 35 years) of the 50-year
exposure period. Therefore, smokers must be considered as
being at Increased risk. (Ryan et al., 198?)
The issue of cadmium In tobacco Is particularly significant since it has
been recently found that growing tobacco on soils, amended with munici-
pal sludges at very high rates (224 t/ha) can result 1n a 30-fold
Increase in the cadmium content of cigarette smoke (Gutenmann, et al.,
1982),
Thus present levels of total dietary Intake of cadmium for most
people appear to be fairly safe. However, in view of human variability
in sensitivity and the variability In food supply, these levels probably
should not be allowed to rise greatly.
It 1s of interest to note that increased consumption by individuals
of those leafy and root vegetable crops highest 1n cadmium, and of organ
meats as well, would increase the dietary iron Intake. Since Iron-
sufficient humans absorb only about 2.3% of dietary cadmium compared to
an average absorption of 4.6% (1n the generally iron-deficient American
population) (Flanagan et al^., 1978), the increased iron intake would
tend to correct for theTncreased cadmium intake.
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KOWAL
Trace Elements: Conclusions and Research Needs
It seems reasonable to conclude that cadmium is the only trace ele-
ment likely to be of health concern to humans as a result of land appli-
cation of wastewater or sludge, with the exposure being through food
plants or organ meats. Groundwater is unlikely to represent a threat
except at rapid infiltration sites.
The potential Increase in cadmium levels in human food due to land
application of wastewater or sludge is still an unsettled question.
Almost all the relevant research on the subject has been done with the
land application of wastewater sludge, but, in spite of the high
cadmium-application rates associated with this practice, insufficient
time has elapsed to allow many firm conclusions to be drawn. It is
clear, however, that increased cadmium in the soil results in increased
cadmium in the plants grown in that soil, the degree of increase being a
function of cadmium amendment, plant species and cultlvar, soil pH,
organic matter, and time since application (Ryan et a_L, 19R2). Some
are optimistic. Thus, Davis and Coker (1980) made an extensive review
of cadmium in agriculture, particularly the potential transfer of cad-
mium from wastewater sludge Into the human food chain. It was concluded
that when sludge Is applied to farmland in accordance with current prac-
tice, the hazard attributable to possible effects of the cadmium in the
sludge on crops, animals, or the human food chain, is negligible. The
degree of risk to man, of course, is dependent upon the amount of the
food supply affected and the diet selection of the individual.
The most significant research needs in the area of trace elements
continues to be the development of an understanding of the factors
controlling the uptake of trace elements by plant crops at land
application sites, their entry Into the human food supply, and their
effect on a variable human population. Assessments of the risk of expo-
sure to lead and mercury should be performed, similar to that recently
done for cadmium (Ryan et^ al_., 1982).
NITRATES
Nitrogenous wastes are important constituents of municipal wastewa-
ters, consisting of (1) proteins and other nitrogenous organlcs from
feces, food wastes, etc., (2) urea from urine, and (3) their breakdown
products. Bacteria rapidly decompose most forms of organic nitrogen to
ammonium (or ammonia) 1n wastewater or soil. Under aerobic conditions
ammonium is oxidized by bacteria (Nltrosomonas) to nitrite, and the
nitrite rapidly oxidized by bacteria (Nltrobacter) to nitrate; the two-
step process 1s called "nitrification." Under anaerobic conditions, and
in the presence of organic matter, bacteria can use nitrate as a source
of oxygen, and convert nitrate to molecular nitrogen, which escapes to
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An Overv nw ot Public Health Effects
Page 377
the atmosphere; this is called "denitriflcation." Both aquatic and
terrestrial plants can use ammonium and nitrate as a nitrogen source.
Inorganic nitrogen Is normally quite innocuous from a human health
point of view, although high ammonia levels can present an aesthetic
problem. The major health concern is that infants, less than about
three months of age and consuming large quantities of high-nitrate
drinking water through prepared formula, have a high risk of developing
methemoglobinemia. The incompletely developed capacity to secrete
gastric acid in the Infant allows the gastric pH to rise sufficiently to
encourage the growth of bacteria which reduce nitrate to nitrite in the
upper gastrointestinal tract. The nitrite is absorbed into the
bloodstream, and oxidizes the ferrous Iron 1n hemoglobin to the ferric
state, 1n which form It 1s Incapable of carrying oxygen. Fetal hemoglo-
bin (HbF), 50-85t of total hemoglobin at birth, is particularly suscep-
tible to this transformation to methemoglobin. Methemoglobin is
normally present 1n the erythrocytes of adults at a concentration of
about T% of total hemoglobin, being formed by numerous agents, but kept
to a low level by the methemoglobin reductase enzyme system. This
enzyme system is normally not completely developed in young Infants. At
a methemoglobin concentration of about 5-10% of total hemoglobin the
body's oxygen deficit results 1n clinically-detectable cyanosis. As a
result of epidem1ologlcal and clinical studies (Shuval and Gruener,
1977; Craun et al., 1981; Fraser and Chllvers, 1981) a primary drinking
water standa~F3 "of 10 mg/1 of nitrate-nitrogen (i.e., nitrate expressed
as N) has been established (U.S. EPA, 1977) to prevent this condition
from developing.
Besides methemoglobinemia, there Is also seme concern about nitra-
tes resulting in the formation of carcinogenic N-nitroso compounds in
the gut, but this phenomenon probably involves higher concentrations
than the 10 mg/1 water standard (Fraser et aj^., 1980; Fraser and
Chllvers, 1981).
The relevance of land application, of course, centers on the possi-
bility of highly soluble nitrates reaching groundwater which may be used
as a potable water supply. In land treatment, the threat again 1s most
likely at rapld-inflltratlon sites. In the case of land application of
sludge, there would probably be minimal threat If the sludge were
applied at nitrogen rates, but higher rates or application outside of
seasons of nitrogen uptake might be a hazard.
It should be kept frr mind that land application sites are not the
only source of nitrate in groundwater. Many groundwaters are naturally
high 1n nitrates and 1n urban areas on-site absorption fields and lawn
fertilizers have been shown to be sources of nitrates in groundwaters
(Porter, 1980).
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KOWAL
In conclusion, land application systems, particularly rapid-
infiltration land treatment, threaten to raise the nitrate concentration
in their underlying groundwater above the drinking water standard of 10
mg/1 as N. This can be prevented, however, by proper siting and manage-
ment practices, e.g., using high C:N ratio wastewater, matching loading
rate to crop uptake, and optimizing the flooding-drylng regime. These
management practices and the agronomic factors controlling the entrance
of nitrates into groundwater are Important research needs.
SODIUM
Sodium may enter the groundwater beneath land application sites,
just as nitrogen does. For example, at the Wroclaw, Poland, sewage
farm, an untreated wastewater sodium content of 83-115 mg/1 was
reflected In a groundwater content of 90-144 mg/1 (Cebula and Kutera,
1978). This level may be compared with the sodium content of U.S.
drinking waters, 58% of which have 0-20 mg/1, and only 14% of which have
over 100 mg/1 (White et £l_., 1967). A primary drinking water standard
for sodium has not been established (U.S. EPA, 1977).
The health significance of these raised levels 1n groundwater, and
thus potentially in drinking water, 1s unclear, particularly since
drinking water sodium is a small portion of total dietary Intake (2-8
g/day). That a decreased Intake of sodium can reduce blood pressure 1n
subjects with mild hypertension has been shown by several clinical
studies, e.g., Beard et al. (1982), but the overall significance of
restricted sodium consumption to preventing hypertension in the general
public has been recently challenged (Kolata, 1982; Boffey, 1982; Puska
ert £]_., 1983). Similarly, the evidence that high sodium consumption
causes hypertension is tenuous. However, increased groundwater sodium
concentrations beneath land treatment sites should be kept in mind as a
possible future health concern.
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An OvelA/iew of Public Health Effects
Page 379
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waters: A revTew of their occurrence and survival. In: Virus
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Griffin, ed.), 59-74. University of Illinois, Urbana-Champalgn,
Illinois.
2. Argent, V. A., et aj_. 1977. Animal disease hazards of sludge dispo-
sal to land:Uccurrence of pathogenic organisms. Water Pollut.
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3. Argent, V.A., et aK 1981. Animal disease hazards of sewage-sludge
disposal toHand: Effects of sludge treatment on Salmonellae.
Water Pollut. Cont. 80:537-540.
4. Arundel, J. H. and A. 0. Adolph. 1980. Preliminary observations
on the removal of Taenia saginata eggs from sewage using various
treatment processes"! Austral. Vet. J. 56:492-495.
5. Ayanwale, L. F., et^ £]_. 1980. Investigation of Salmonella infection
1n goats fed corn silage grown on land fertilized with sewage
sludge. Appl. Environ. Microbiol. 40:285-286.
6. Babayeva, R. I. 1966. Survival of beef tapeworm oncospheres on the
surface of the soil 1n Samarkand. Med. Parazitiol. Parazlt.
Bolezn. 35:557-560,
7. Baker, E. J., Jr., et al. 1980. Metabolic consequences of exposure
to poTychlorinate3"ETphenyls (PCB) 1n sewage sludge. Amer. J.
Epidemiol. 112:553-563.
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143. Remington, J.S., and S. C. ScMmpff. 1981. Please don't eat the
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144. Rendtorff, R. C. 1954a. The experimental transmission of human
Intestinal protozoan parasites. I. Endamoeba col 1 cysts given
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146. Rendtorff, R. C. 1979. The experimental transmission of G1ard1a
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147. Richmond, S. J,, et al_. 1979. An outbreak of gastroenteritis
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An Overview of Public Health FMects
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149. Rudolfs, W., et aj_. 1951a. Contamination of vegetables grown in
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150. Rudolfs, W., et al. 1951b. Contamination of vegetables grown in
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151. Rudolfs, W., et al. 1951c. Contamination of vegetables grown 1n
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152. Ryan, J. A., H. R. Pahren, and J. B. Lucas. 1982. Controlling
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160. Smith, G. S. 1982. Health risks of organlcs 1n land application.
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QUESTIONS AND COMMENTS FROM THE FLOOR:
William Davis, City of Long Beach: 1. Has any of the research and
study over the past 10 years identified a specifia instance of a public
health problem caused by land application of sludge in any form? 2.
Has any of the research and study over the past 10 years identified a
specific instance of a public health problem caused by land application
of wastewater in any form?
Norman Kowal: To our knowledge, no.
C. Richard Dorn, Ohio State University: I can add some information
based upon preliminary analysis of data collected in the Ohio Farm
Bureau-Ohio State University project studying health effects of municipal
sewage sludge on farm land. We have not observed any specific episode of
human illness that appeared to be associated with sludge application on
4? sludge-receiving farms in the study. Furthermore, the illness rates
on these farms were no higher than the illness rates on 46 control fartns.
In the laboratory of my project colleague, Dr. Abramo Ottolenghit and in
my laboratory, we have examined the sludge applied and human and animal
feces samples from sludge and control farms for Salmonella. We isolated
Salmonella from the sludge, people, and animals (both from sludge and
control farms). However, there was no difference in the frequency of
isolation from sludge and control farms. In addition, these types of the
Salmonella isolates did not match nor was there any apparent temporal
association with sludge applications and isolates of Salmonella on the
sludge receiving-farms. It must be emphasized that we were using low
application rates of 2-6 dry tons per acre. Br. Kowal, in regard to the
conflicting negative and positive observations of association between
Salmonella in sludge applied to farm land in various European
countriesand infections by the same Salmonella serotype in animals, do
you have any information about the sludge application rates used in the
various countries and could this explain the conflicting observations?
Norman Kowal: I am familiar with the conflict, but have seen no
data on application rates.
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WORKSHOP FINDINGS
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Page 399
WORKSHOP FINDINGS
Political and Institutional Constraints
William Davis, Moderator
Richard White, Co-Moderator
Lee Christensen, Secretary
Hunter Follett, Co-Secretary
Participants: Henry H. Benjes, Jr., James Butler, Charles M. Cameron,
Jr., Leon Chesnisn, Michael Conti, David Cooper, Jack L.
Cooper, Roger Dean, Lynn Forster, Henry Hyde, Cecil
Lue-Hing, Robert Manson, Robert H. Miller, Merry L.
Morris, Lois New, Robert C. Polta, William F. Pounds,
Merilyn Reeves, B. R. Sabey, Charles M. Smith, Douglas
Southgate, Charles Spooner
"Unless political and institutional constraints on the land applica-
tion of effluents and sludges are recognized, identified, and
resolved, these projects will likely fail, regardless of their tech-
nical, scientific and economic feasibility."
This conclusion of the 1973 Joint Conference on Recycling Municipal
Sludges and Effluents on Land provided the starting point for the work-
shop discussion of political and Institutional constraints. Goals of the
workshop were to review progress to date and identify need for future
action. Three fundamental questions were posed as the departure point
for discussion: (a) How has research helped in reducing constraints? (b)
Is information getting to those who must resolve constraints? (c) Can
unqualified assurance be provided that a specific project will not cause
harm to human health or environment?
Discussion was spirited and yielded the following generalizations:
1. Research conducted over the last 10 years has created a reservoir of
professional expertise and information upon which to base state and local
guidelines and for Identification and the resolution concerns on the
basis of fact. Research has also provided general guidance for land
application programs by identification of design and operational
constraints.
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DAVIS AND WHITE
2. Information 1s generally flowing to members of the professional com-
munity. However, there is need to provide information to the public in
an understandable form so the public may have a basis for considering the
technical and scientific information that is presented.
3. Good management practices are a prerequisite in order to give assur-
ances that, for a given situation, 1andspreading of effluents and sludges
can be accomplished safely with minimal risk and attendant benefits.
4. Unqualified assurances of no risk cannot be provided. Such assuran-
ces won't be believed and represent an expectation that is not matched in
other facets of society. Care should be taken to avoid being placed 1n
the position of being asked to provide such assurances. Well designed
programs to develop acceptance and avoid situations which generate anta-
gonism among participants are extremely important in this regard.
FEDERAL REGULATIONS
The general consensus of the workshop participants was that federal
regulations should "force" the evaluation of all reasonable alternatives
for management of effluents and sludges. Such regulations should also
provide for public notification of noncompliance with regulatory require-
ments and good management practices.
Federal regulations should provide guidance and be flexible but
should not specify the design of a 1andspreading system. Federal regula-
tions must not preclude the ability of states and local agencies to com-
bine their unique social, economic, political, and physical factors in a
way that 1s environmentally and technically sound and socially accep-
table.
Minimum Standards
It was the consensus of the workshop that minimum standards are
needed for the key health parameters. Minimum standards provide an Inde-
pendent benchmark for Incorporation of necessary safeguards In projects
and assurance that projects are safe for human health. Federal standards
should, however, not preclude state Initiatives towards more stringent
standards.
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Report Institutional Constraints
Page 401
The question of who should set minimal health standards was not
resolved. Considerable discussion of this issue centered around two
positions:
1. Federal regulations should contain minimal standards since some sta-
tes are unwilling or Incapable of setting such standards.
2. Standard setting should be delegated to state or local authorities
within a broadly stated federal policy.
KEYS TO ACCEPTANCE
Acceptance of landspreading of effluents can best be achieved
through well designed programs based upon education, communication, and
planning. Elements of such a program are:
1. Independent Resource Personnel: Involvement of resource personnel
that are not directly responsible for the project development process.
For example, this could include university personnel from the subject
matter areas of agriculture, engineering, forestry, economics, etc.
Involvement of farm organizations, farm advisors, and local health offi-
cials should also be considered.
2. Early and Continuing Public Involvement 1n Decision Haklng: Public
access to the decision making process 1s critical to development of
public acceptance of a specific landspreading program. Such access must
occur before decisions are made rather than after. In this regard, alter-
natives should be solicited and evaluated with interested and targeted
audiences such as municipal officials, farmers receiving sludge, applica-
tion site neighbors and consumers. Provisions must be made for feedback
of the decision making so that the public may know how their comments
have been considered.
3. Education: Efforts should be made to Inform and educate all affected
groups—for example, neighbors to the project site, the Intended receiver
or user of the effluent or sludge, consumers such as food processors, and
municipalities as the generators of the material. Regulatory agencies
need to improve understanding of the limits and freedoms of action.
Public agencies need to Improve their ability to market their services
and products by better understanding the needs and desires of the par-
ticipants in the project.
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DAVIS AND WHITE
4. Good Media Program: Print, radio, and television media are available
for use in communication and education programs. However, without proper
care, adverse media coverage may result. Early involvement and education
of the media regarding the issues involved and specifics of a project are
recommended. Understanding and accommodating the scheduling and time
information requirements of the media should also help to avoid adverse
press. Also, as in the case of any communication, honesty of information
and full disclosure are essential.
5. Involve Local Elected Officials and Opinion Leaders: Early involve-
ment of local elected officials and key community leaders is vital to
acceptance. Such persons should not learn of a landspreading proposal
from the press or third parties but from those with the best information
-- generally the project proponents and their resource personnel. It is
important to understand these constituencies which local elected offi-
cials represent so that their concerns may be addressed in the develop-
ment of a project. Also, timing of proposals during election campaigns
are likely to generate modest levels of support or strong opposition from
local elected officials and community leaders.
6. Communication: Careful attention to communication of information in a
forthright and honest manner 1s critical. Efforts at technology transfer
need to be improved so that information is provided in a manner which 1s
usable by the public and farm community.
7. Financing: Federal financial support of research should be con-
tinued. Adequate funding of demonstration programs 1n conjunction with
specific land application programs are an important aid 1n securing
acceptance at the local level. Federal support of the USDA Cooperative
Extension Service (CES) should be continued at levels which enable the
CES to assist municipalities and the agricultural communities 1n deve-
loping and implementing land application programs. In view of the
intense competition for the federal dollar, local and state means for
financing research and implementation need to be developed. User fees
collected by municipalities and revenue from sale of effluent or sludge
products are possible revenue sources which should be explored.
INFORMATION AND RESEARCH NEEDS
Land application of wastewater and sludge has expanded over the past
ten years due to regulatory, technological, and economic forces.
Research has helped 1n the development of guidelines and provided a basis
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Report. Institutional Constraints
Page 403
for direction of specific land application programs. There are, however,
several areas requiring additional information and research. Following
is a summary of such needs identified through workshop discussion. No
priority rating is assigned to the following items:
1. Many municipalities are operating successful land application pro-
grams. Summaries of these "case studies" should be written and widely
distributed. Design criteria, management criteria, problems and their
solutions as well as an evaluation of the public relations and educa-
tional program(s) used should be included.
2. Lines of communication between university personnel, e.g., agri-
cultural research and extension, and municipalities should be opened or
expanded to enable university personnel to act as a resource for educa-
tional and public relations programs.
3. There 1s a need for a federal Interagency task force to continue to
address the question of the land application of sewage sludge. The
interagency task force should include at least the following: EPA, USDA,
USA Corps of Engineers.
4. Develop risk assessment methodology for comparison of alternatives.
Factors to be considered should include size of city, treatment pro-
cesses, regional uniquenesses such as soils and climate, predominant
agricultural land uses, etc.
5. Continue to research the fate of pathogens and organlcs associated
with land application of wastewater and sludge. This Information 1s
needed to confirm past decisions and to reduce conservatism in design
which should lower costs.
6. Public acceptance of land application programs depends 1n part on the
public's perception of the Impacts of such programs on land values.
There is an Involved need to evaluate the "conventional concepts" 1n
public acceptance programs to see if in fact they contribute to or hinder
acceptance.
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DAVIS AND WHITE
QUESTIONS AND COMMENTS FROM THE FLOOR:
Curt Schmidt, SCS Engineers: I'd like to compliment Bill on a very
fine presentation and ask him why in the world hie group specifically
said that no design manual wae required. I certainly agree that it is
presumptious to put out the design manual for large communities euch as
Lob Angeles, New York, and bo forth but those of ue who are involved in
putting a design manual together now, feel that one will be helpful to
meet the needs of the smaller size community. I would like you to com-
ment on that, please.
William Davis: The context of that statement was 1n the area of
regulations, mandatory requirements, things which will ultimately get
into the Federal Register. Whatever is published as regulation in the
Register, no matter whether it is called guidelines, tend to become regu-
lations. There is need for guidance. The Federal Register, however, is
not the place to put a design manual. There is need for guidance and
design manuals apart from the regulatory process.
Dr. Richard White, Ohio State University: Let me add a few comments
to Mr. Davis's. My understanding of the reason for not requiring an ex-
tensive design manual is that it is a backlash to the design manual that
is in the process or has come out on the subject of hazardous waste. In
that context, it should not be a "federal design manual" which just sits
on the shelf. This isn't saying that there should not be design cri-
teria. The need for a design manual is probably more on the state level
which would be more realistic for a region as opposed to a national
design manual that would try to be all encompassing and then really not
be functional.
William Davis: It comes out of the concern for flexibility and a
desire to have flexibility to accommodate the local and specific cir-
cumstances. Are there any other questions?
Steve Campbell, BI0GR0 Systems of Annapolis, Maryland: It appears
that success of land application programs is directly proportional to
involvement of universities - especially extension branches. How does
one generate interest and support of the University?
William Davis: One of the findings of the workshop was that the
Involvement of universities, extension services, etc., 1s Important. We
did note that 1n some cases, because of budgetary constraints and lack of
Interest, personnel, some universities aren't responsive.
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Report: Inst tutorial Constraints
Page 405
Dr. Richard White, Ohio State University: In part, I think one of
the keys to getting university personnel involved ie to identify an indi-
vidual who has an interest with regard to the land application of sludge-
-whether it be an engineer or a soil scientist or agronomist. One would
need to cultivate a relationship with that individual because there are
so many pressures and priorities. Rarely will you get something coming
damn from the top, that is to say from a Dean or a Director. I think the
key would be to begin more with a "grassroots" individual who recognizee
the importance and ia witling to put some time on the problem. I think
one key would be—and we discussed it last night—that whether from a
municipal source or from a private contractor if some dollars are put up
to support a graduate student for a year or two it will develop interest
on the part of faculty members quicker than anything else. And it could
be a snail amount—-to pay for the support of one graduate student.
Willi am Davis: Hunter Follett would you care to comment on your
efforts to obtain support along the lines suggested?
Hunter Follett, Colorado State University: I think the example that
Bill wants me to comment about ie the cooperative research project bet~
ween Colorado State University and the Littleton/Englewood Wastewater
Treatment Plant. The treatment plant is supporting a demonstration-
researah project relative to the application of sludge to dryland wheat.
They are providing financial support far a graduate student and to carry
on a research program. This support will be continued for four years and
is to be renewed on an annual basis. We have started at two different
locations, and are experimenting with the land application of sludge to
dryland wheat plots using the same techniques, the same equipment, and
the same truck that they uee to deliver the sludge to the fields. We
have put some experimental plots out in that area where they are actually
applying the sludge to land. We plan to collect information to develop a
research base and to develop an educational program to assist the munici-
pality. We can then uee the information to gain support from the farmers
in that area. I think this his been a successful approach to getting
financial support from a municipality for this type of work.
William Davis: This is probably something I went over very lightly.
It is important to have a piece of ground somewhere nearby where the
activity Is actually being done on a demonstration basis and where data
and information are being gathered that are applicable to the project
area.
Hunter Follett: I should mention that we have cooperation from the
company that is applying the sludge, the county agent, the farmer and the
wastewater treatment plant. Therefore, thie has been a Joint effort from
several different organizations.
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DAVIS AND WHITE
A* L. Page, University of California: If I may, it appears that
there may be a deficiency in the avenues of communication between the
various muncipalitiee and various colleges and universities in the local
area. Possibly this is something that could be greatly improved through
some mechanism associated with institutional constraints and we nay want
to include that as an item which would deserve some very serious con-
sideration.
Kenneth Doteon, EPA, Cincinnati: Involvement of farm organisations
can encourage state university, College of Agriculture staff to be in-
volved in educational as well as research programs concerning sludge use
on land. Please clarify what is meant by conservatism of regulations
pertaining to organics and pathogens associated with land treatment of
wastewater and/or sludge. Is the conservatism alluded to based on an
estimation of the ability of a chemical to produce an adverse health
effect or does it arise from the models used to estimate the exposure of
man to these agents?
Willi am Davis: Let me give the context as we now see 1t. In the
programs that are going on now, decisions are being made as to what to do
relative to concerns Involving pathogens and trace organics. There was a
feeling that the data base could be Improved. Not in modeling efforts
but in the information going to the field. When the decision is made to
do a project you can only work with whatever data that 1s there. There
1s a tendency to build In safety factors on top of whatever the research
Indicates and designers tend to back farther away if the data base is
weak. What is being addressed here 1s not a particular model but the
situation where people that are dealing with the problem 1n the field in
terms of putting projects in and building conservatism into their
design.
William Pounds, Pennsylvania Department of Environmental Resources:
Not necessarily would I respond totally to that question but I think what
we tried to do in Pennsylvania is to use management technology for
farming sites and include certain requirements that limit the amount of
sludge you are allowed to apply to land, limit sludges to those that are
digested or lime stabilized, require incorporation of sludge within cer-
tain time periods, eta. In addition to this, we also require that no
cattle be grazed for a period of two months on pasture where sludge has
been applied. In establishing this program we are not just "shooting
from the hip", but were using the beet available technology at the time.
What I would like to see is support for the statements I have heard from
Lee Sommers, and yesterday from Michael Overcash, which indicated that
apparently We made the right decision. On occasion, we have made judg-
ments sometimes "by the seat of our pants", but always based on the best
available research, and from what I have heard the last two days,
apparently we made the correct decisions. I think the statement can be
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Report. Institutional Constraints
Page 407
made that if a site ie property selected and managed with limited appli-
cations of sludge, there is a minimum impact from organics. That state-
ment was made, but not strongly reinforced. I think from the quorum such
as we have at this workshop, we can make such a statement in the summary.
It would go a long way in helping us in terms of institutional and atti-
tudinzl constraints.
Jack Cooper, Director, Environmental Affairs, National Food Proces-
sors Association: On the subject of political and institutional con-
straints, our association has a policy on the use of municipal sewage
sludge in the production of foods for human consumption. The association
represents about S00 companies that pack processed-prepared fruits, vege-
tables, meats, soups, baby foods, fish and specialty products, including
canned, frozen, dehydrated, pickled and other preserved food items. The
Association provides extensive technical support to its members through
its three laboratories located in Washington, D.C, Berkeley, California,
and Seattle, Washington.
In 1981, the NFPA Agricultural and Environmental Committees reviewed
the fact that increasing volumes of sewage sludge were being applied to
croplands and that crops for human consumption Were being grown in sewage
sludge-amended soils. These committees also reviewed available federal
regulations and guidance. In November 1981, the NFPA Board of Directors
adopted the following policy statement:
The National Food Processors Association (NFPA) recognizes that the
application of sewage sludges generated by publicly owned treatment
works (POTWs) to croplands can be a beneficial use when the proper
conditions exist and the sludges have been determined to be safe for
the use intended. The NFPA, however, has serious concern that
sludges produced by POTWs may contain heavy metals, human pathogens,
and toxic compounds which could have potential health effects on the
consumers of foods produced on lands to which such sludges have been
applied. This potential risk to public health has not been ade-
quately evaluated. Therefore, NFPA cannot endorse the application
of municipal sludge to land that may or will be used in the produc-
tion of foods for human consumption until the questions regarding
its safety for such use are resolved. Therefore, NFPA urges the
EPA, USDA, and FDA to establish an interagency task force to develop
definitive policies and regulations which identify the specific con-
ditions under which municipal sludges can be safely applied to land
on which foods for human consumption will be produced. Furthermore,
NFPA recommends that the interagency task force seek the advice and
counsel of NFPA and other groups representing agriculture, indus-
trial, and public interests in the development of appropriate poli-
cies and regulations.
In late 1982, NFPA sent to each of its members a letter providing a
copy of the EPA 1979 regulations, the EPA/FDA/USDA policy statement,
and background information. The letter advised each company to
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DAVIS AND WHITE
review the subject with their own legal counsel. While the Associa-
tion's position doesn't endorse sludge use in crop production, it
certainly doesn't prohibit it. It is up to each company to
establish whatever restrictions, if any, that it feels are in its
best interest.
Unfortunately there are, and probably always will be, unresolved
public health concerns about sewage sludge use in crop Production
that will prevent NFPA from changing its basic policy. However, on
a eite-by-site, aaee-by-case basis, if our individual members are
brought into the decisionmaking process sufficiently early so that
they can draw their own conclusions about the safety of an indivi-
dual operation, and make recommendations for change, were necessary,
local resistance from this source may be overcome.
I am encouraged today, where I have heard over and over again the
statment that "well managed" projects will not harm public health or
the environment.
Dale Baker, Pennsylvania State University and also Chairman of the
Northeast Regional Task Force: It is extremely important that we have
concerted efforts among experiment station personnel, regulatory people
and operations people in the management of sewage sludge and effluent on
land. The Directors of the Northeast experiment stations recognized that
when they authorised our Task Force to develop a document on Criteria and
Recommendations for Land Application of Sludges in the Northeast. The
Northeast Regional document in itself is part of an experiment. It is
one way of getting the scientists to make a concerted effort to reach
agreement on what is possible in the land application of sludges under
different situations. Maybe, at least it's leaked back to me, some
people consider the Northeast document to be extremely conservative. It
is, however, sornewhat HbeTvCl with respect to eludge use for land recla-
mation and land disposal of sludges at dediaated sites. This experiment,
in the end, may point to the direction that all other regions will want
to take. I am very proud of the fact that we have had people that are
very conservative and who have very real concerns about the use of sludge
on land working with others who have had experience with eludge on land.
It has been a reixirding experience to get those people together eduoar-
tors and researchers) to develop a document that has about 30 authors
from 14 states involved. The experiment station record will in the end
have to take oredit for allowing the group to come up with the document.
The nain objective is the development of an operational program for every
state in the northeast. If we can encourage uniformity among states, I
believe it will be beneficial. It will maximiae the utilisation of
sludges on land because uniform recommendations let everyone know where
they stand. No project appears to be an exception, and that is not true
if you don't have a oonaerted effort. I can't speak for the Experiment
Station Directors, but the document is near completion; the experiment is
in plaoe and I am happy with the result a.
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Engineering Sy&teme
Raymond Loehr, Moderator
Sherwood Reed, Co-Moderator
Takashi Asano, Secretary
James Parr, Co-Secretary
Participants: J. W. Biggar, Patrick L. Burke, Stephen Campbell, C. E.
Clapp, Donald Deemer, H. A. Elliott, Eliot Epstein, Joseph
Farrell, Ronald F. Follett, Craig G. Hebberd, Frank
Humenik, Richard Johnson, C. James Martel, James
Patterson, Charles Pound, William Rosenkranz, Curtis
Schmidt, E. D. Smith, J. L. Smith, Robert G, Smith,
Stephen B. Smith, George Tchobanoglous, Dale H.
Vanderholm, Jack L. Witherow
INTRODUCTION
The 1972 Amendments to the Federal Water Pollution Conrol Act {PL
92-500) provided the requirement and the incentives to utilize land
application of municipal wastewater and sludges. The 1973 workshop
defined the research needs for implementation of these concepts.
In the decade since 1973 several thousand systems 1n the United
States are now used to apply wastewater to land in a controlled and
managed manner; 1n the next decade at least another 1000 systems are
expected to be designed and Installed. Also, there are many systems
applying sludge to the land. In 1978, 1t was estimated that at least 1.0
million dry tons of sludge were being applied to U.S. land or about 25%
of the total sludge requiring disposal. The use of land treatment
systems 1s expected to increase as a result of ever-improving research
and from the experience gained 1n operating existing systems.
The research and development efforts of the past decade have
clearly established land treatment as a viable cost effective technology
using both wastewater and sludge. Now that adequate information 1s
available, the engineering profession routinely consider the concepts of
land treatment during design and planning stages with a high level of
confidence that the required performance goals can be achieved.
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LOEHR AND REED
Similarly, sound management and operational procedures for land
treatment systems have grown steadily, and 1s regularly translated Into
improved environmentally sound and cost-effective land treatment systems.
In use in all climates and geographical regions land treatment offers a
level of dependibllity not found in alternative wastewater treatment and
sludge management systems. The safety factor inherent 1n land treatment
system design provide a reserve capacity to accommodate minor design
problems, as well as changes in sludge or wastewater characteristics.
Waste treatment, rather than optimum crop production, is the pri-
mary goal of land treatment systems, i.e., to treat wastewaters and
manage sludges in a manner that insures compliance with all environmental
requirements and regulations.
The participants in this workshop came to a consensus about needs
presented in the overview paper, Engineering and Economics (Pound, Crites
and Griffes). This summary focuses on the major needs and recommen-
dations that relate to improved and cost-effective design of land treat-
ment systems. The overview paper was consulted to identify other more
detailed needs and recommendations pertinent to specific Interests and
situations. Two important areas covered by the overview were:
(a) the application of sludge to disturbed lands and the
application of wastewater and sludge to forest land
were promising alternatives that deserved further
attention and evaluation.
(b) the design of land treatment systems should Include
adequate sediment and erosion control measures.
Although significant advances in design knowledge have been made
since the 1973 workshop, progress is needed to make land treatment
systems more effective and less costly.
ASSESSMENT OF ACCOMPLISHMENTS SINCE 1973
There has been considerable progress with regard to the engi-
neering design of land treatment and sludge application systems in the
past decade. Based upon the experience gained 1n this period, the
following conclusions can be made:
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Report Engineering Syslems
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1. Land treatment 1s a component 1n a total treatment system and 1s not
just a disposal process. Recognition must be made of the pollutant remo-
vals that occur in the soil-plant ecosystem since It is an integral part
of the total treatment system. Such recognition encompasses: (a)
rational engineering design that Includes appropriate credit for pollu-
tant removal in the soil-plant ecosystem, and (b) the development of a
least cost waste management system.
2. Experience since 1973 has shown that when land treatment systems are
properly designed and operated, the reliability and treatment performance
of these systems 1s equal to or better than that of conventional waste-
water treatment systems.
3. Experience has shown that when sites for the land application of
sludge are properly designed and managed, reliability and performance Is
equal to or better than that of other sludge management systems.
4. The state-of-ttie-art engineering design of land treatment systems
developed since 1973, 1s adequate to meet the designated water quality
crlteri a.
NEEDS AND RECOMMENDATIONS
Much useful information has been obtained during the past decade to
resolve problems faced by the engineering community in the planning and
design of wastewater treatment and sludge management systems. There con-
tinues to be a need for additional information to improve and optimize
land based wastewater treatment and sludge management systems to meet
specific performance goals.
High Priority
1. A major emphasis should be placed on post-construction performance
evaluations and cost documentation of existing land treatment systems.
The original design criteria should be evaluated 1n terms of actual per-
formance of the existing systems. Modification of the design criteria
should be made where appropriate.
A common protocol should be developed for post-construction perfor-
mance evaluations. The evaluation should assess: (a) the adequacy of the
hydraulic application rates, (b) the transformations and fate of nitro-
gen, phosphorus, organics, and metals, (c) the adequacy of existing
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LOtHR AND REED
monitoring requirements, (d) the actual cost of land treatment system
components, and (e) changes in the land value of adjacent property.
These evaluations will identify: (a) an improved cost data base, (b)
more appropriate monitoring requirements, and (c) improved design and
operational criteria.
2. Design criteria for application of wastewater and sludges to forest
ecosystems are needed. Forest lands have great potential to receive and
accommodate wastewaters and sludges for soil improvement as well as for
nutrient and water utilization by forest species. However, a limiting
factor appears to be the lack of reliable and economical application
methods. Information also should be obtained on appropriate organic and
metal loading rates and their impact on the chemical and physical proper-
ties of forest soils.
3. (a) Management techniques for optimum total nitrogen removal in the
field for wastewater and sludge applications should be developed.
(b) The understanding and modeling of nitrogen and phosphorus trans-
formations and removals, Including nitrogen mineralization rates, espe-
cially 1n field situations, should be Improved. The development of
improved and simple modeling techniques for estimating the rate and ex-
tent of nitrogen and phosphorus transformations and removal is desirable.
Better management and modeling techniques would improve the design of
less costly land treatment systems.
4. The heavy metal loading criteria should be reassessed. This re-
assessment is especially needed for western soils and for long-term
loadings. Present criteria are considered by many to be conservative.
Less conservative criteria could greatly improve the cost relationships
of land treatment systems.
Land application of wastewater effluents and sludges can be limited
by overly restrictive and unrealistic criteria which may effectively
exclude land application from consideration as a viable option and may
lead to the adoption of less environmentally acceptable alternatives.
5. Specific research needs Include: (a) determining the transformation
and fate of trace organlcs fn land application and treatment systems, (b)
evaluation of overland flow systems 1n cold climates.
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Page 413
QUESTIONS AND COMMMENTS FROM THE FLOOR:
7. A. Demirijian, Muskegon, Michigan: Have you given aoneideration
to the energy aspects of the design since land treatment systems can have
a high energy requirement? Have you given aoneideration for energy
conservation?
Raymond Loehr: The energy aspects were discussed and included 1n
the needs and recommendations in an implicit rather than explicit manner.
The energy concerns were included as part of the post-construction eva-
luation. It was expected that such evaluations would Identify the energy
demands at the land treatment sites and to try to quantify them.
Raymond F, Shipp, Pennsylvania State University: I am curious to
know what the discussion was relative to the amount of pretreatment con-
sidered desirable for the different systems. Should disinfection be con-
sidered a requirement or not?
Raymond Loehr: This point was addressed by pointing out what the
group felt about pretreatment requirements. These requirements are site
specific and are related to the wastewater characteristics and objective
of the system. Let's assume that the objective 1s to meet drinking water
quality criteria. The approach would be to look at the site specific
soil situations and see what removal takes place 1n the soil. With sandy
soil you might have completely different pre-appl1cation needs than with
clayey soils. The question does not revolve about the need for disinfec-
tion but about how to meet the objectives and avoid adverse Impacts to
the system components and equipment. The group discussion focused on
whether there was adequate technical knowledge of how to develop a design
given whatever the standards that were to be met.
To specifically answer your question, the discussion indicated that
there 1s adequate disinfection technology that could be used where 1t 1s
needed. The group did not get Into the discussion of whether disinfec-
tion was needed prior land application but whether the adequate disinfec-
tion technology was available. If adequate bacterial removals occurred
1n the soil, disinfection should not be needed prior to land treatment.
Michael Connor, Harvard School of Public Health: I have two
questions. 1. In the statement of goals to achieve groundwater quality
standards, is the distinction between meting drinking water standards
and not affecting ambient water quality? For instance, many agricultural
areas have ambient nitrate levels which do not meet drinking water stan-
dards 2. The public health workshop expressed concern over the potential
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LOEHR AND REED
of rapid infiltration systems to leach organise and metals into ground-
water. Did the workshop address the levele of pre-treatment necessary
for rapid infiltration systems?
Raymond Loehr: There was some discussion related to the first
question. The ambient water quality discussion related more to drier,
arid climates where there might be groundwater which had high dissolved
solids. There would be little logic in achieving drinking water quality
from a land treatment system if it is likely that the water will not to
be used for that purpose, or if it had to be treated before it could be
used for drinking water.
The discussion also related to the technology to minimize excess
nitrogen in the water that reached the groundwater or the system boun-
dary. Identification of the system boundary may require further defini-
tion. However, the discussion indicated that 1n general there was
probably adequate information on how to design land treatment systems so
that the water that passed the system boundaries did not have excess
nitrogen.
Michael Connor: The second question related to pretreatment require-
ments. There was concern expressed in the health group on rapid
infiltration systems and the potential for organics in such systems to
leaah to groundwater. Did your group discuss this point?
Raymond Loehr: We discussed that point but again 1t was in the con-
text mentioned earlier, i.e., whether or not there was adequate tech-
nology to protect the quality of the ultimate water use. If with rapid
infiltration, there was significant movement of organics, there are tech-
nologies that could be used to minimize such problems. PreappHcation
technologies would be one approach.
A. L. Page, University of California: Hay, could you elaborate
briefly on the discussion associated with the research recommendation
relative to heavy metal loading and the comment you made that such
loadings rray be conservative with respect to the current guidelines and
regulations.
Raymond Loehr: Our group continues to be guided by those who have
spent considerable time evaluating the whole question of the heavy metals
1n the land, their reversibility, their uptake, and their fate. The item
the group discussed was as stated earlier, based on the existing systems,
concern that the heavy metal loading criteria might be too conservative,
especially for some of the metals. If the metal criteria currently used
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Report: Engineering Systems
Page 415
were conservative arid were to be changed, land treatment systems could be
more cost effective. We did not get Into any detailed discussion as to
whether they were or were not conservative, feeling that this topic would
be discussed by other groups. Our discussion was a recognition of the
fact there was a constraint on the system which did affect the cost
effectiveness of the system and that if there were changes to relieve
that constraint, such changes would have an impact on the cost effec-
tiveness of the system. Hence, a reassessment might be in order.
William Davie, the City of Long Beach: That raises a question: In
the last 10 years, we have conducted a lot of research and lot of data
has indicated that adjustment of the regulations might improve the cost
effectiveness of land application programs. Does the research conducted
provide the basis to adjust the regulation?
Raymond Loehr: I'm the wrong one to answer that question. I assume
that this could be addressed by the group will be discussing the heavy
metal question this morning? Who is that?
A. L. Page: That would be Lee Sommere.
William Davis: The thought that occurred to me as a result of
listening to some of the comments was that perhaps the cost effectiveness
of these land application programs could be improved with some adjustment
in the regulations. This leads me to the question—Has the research of
the last 10 years provided the information that can be used to adjust or
improve the regulations so we can improve the cost effectiveness and
expand the capabilities of land application programs?
Lee Sommers, Purdue University: From the standpoint of trace
metale?
William Davis: Yes, as well as chlorinated hydrocarbons, and
nitrates*
Lee Sommers: In our group, we were totally concerned with sludge
management practices in relation to crop production• We basically felt
that there is sufficient information available to manage inputs of trace
elements from sludge and effluents such that crop productivity would be
maintained or improved and surface and groundwater would be protected
from contamination. Although the current guidelines for trace element
inputs that exist in different regions of the country do protect plants
as far as yield are concerned, there was a general feeling that metal
limits may be overly conservative. Howevert we don't really have the
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L.OFHR and reed
information available right now to say how high limits could be without
sacrificing crop production. This we identified as our overall research
needs. We did not address the human health issue which is really the
direct reason for the regulations on cadmium.
William Davis: You did not address the human health question?
Lee Sommers: We did not, because other workshop groups were con-
cerned with the health effects.
William Davis: Could the moderator of the session which addressed
health effects of Cd comment in terms of the adequacy of existing regula-
tions, i.e., too conservative, too liberal?
A. L. 'Page: We have a workshop on organias and inorganics in rela-
tion to public health. Would Herbert Pahren, the moderator of this
group, care to comment?
Herbert Pahren, EPA, Cincinnati: This will be covered in our
report. I'd prefer to address it at that time.
Merilyn B. Reeves, League of Women Voters: In the recommendation
that land treatment be considered a component of total effluent treatment
was there discussion of how such a recommendation affects the cost effec-
tiveness and competitiveness of land treatment over conventional
treatment?
Raymond Loehr: The discussion did revolve around that particular
point. But not as If land treatment was an add-on process. The key to
decisions about preapplication treatment goes back to the question of the
goal that 1s to be achieved. If a new system is being developed, you
have the opportunity to start, with the raw wastewater and find a system
to accomplish that goal and Include land treatment as a major component
of that system. If the system 1s 1n place and it 1s to be upgraded, land
treatment might be an add-on. However, the basic question is how does
land treatment help meet the pollution control or water quality objec-
tives. Land treatment should not be considered only as an add-on com-
ponent to do some polishing. Land treatment can be a major component of
the entire treatment system and can accomplish considerable pollutant
removal. The consensus of the group was that there 1s a lot of the tech-
nology which could be Integrated with the land treatment component to
achieve the goals Identified earlier.
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Report: Engineering Systems
Page 417
Donald Deemer, ERM, Inc., West Chester, PA: Let me also try to
address that question. Emphasis Das placed on the fact that land treat-
ment is an important part of the total treatment system. If it is not so
considered, i.e., if it is considered strictly as a disposal method, then
the economics became prohibitive. The emphasis should be on the fact
that the soil is a key component of the treatment system. The soil-plant
system can treat the wastewater and the sludge. The system design and
the review by the regulatory agency should reflect this fact. Under sueh
conditions, land treatment can be shown to be cost effective when com-
pared to conventional treatment systems. If land treatment is considered
only as a disposal method that has to be proceeded by a conventional
secondary treatment system, then land treatment rarely is competitive.
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Management Considerations in Effluent Uee
P. F. Pratt, Moderator
W. E. Sopper, Co-Moderator
Richard Thomas, Secretary
Lowell Leach, Co-Secretary
Participants: Donald D. Adrian, David Arlail, Charles R. Berry, Francis
Broadbent, Ronald Crltes, Y. A. Demir1j1an, Frank M.
D'ltrl, Harvey Doner, A. Erlckson, Norman Evans, Herbert
D. Grover, I. K. Iskandar, B. D. Knezek, C. R. Lee,
Harvey Luce, L. J. Lund, Dale Nichols, Wade Nutter, Betty
H. Olson, Antonio Palazzo, Albert T. Wallace, Joel
Webster,Flora Mae Weillngs
INTRODUCTION
This 1983 workshop was not restricted to management; design and
application both crucial to successful land treatment systems, were also
examined and discussed.
Besides assessing progress in wastewater and sludge processing on
land since the 1973 workshop, the 1983 workshop identified those areas
needing continued research. In many areas of concern in 1973, the 1983
conference deemed that sufficient information and data had been generated
and made widely available 1n the last decade. Further work in these
areas were assigned a low priority as a research need; although 1t 1s
recognized that continuing experience in the field will add to the avail-
able Information and data. Other areas of the three systems considered
by this workshop were assigned "medium" or "high" priorities according to
the workshop consensus.
For slow rate systems, the workshop concluded that adequate Infor-
mation was available for (1) crop selection, crop response, and crop
management, (2) erosion control, (3) effluent loading rates, (4) reten-
tion of heavy metals, suspended solids and phosphorus, (5) decomposition
of organic materials 1n effluents, and (6) quality criteria for inorga-
nic materials in effluents used for Irrigating crops.
For rapid infiltration systems, the workshop group agreed that there
was adequate information on (1) characterization of soils, (2) retention
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PRATT AND SOPPER
of suspended solids, (3) reduction in BOD, and (4) heavy metals.
Although site selection procedures were not considered to be completely
adequate, many mistakes with site selection were not considered to be due
to lack of information or methodology, but rather improper application of
methods and/or inadequate sampling in three dimensions.
For overland flow systems the workshop agreed that there was suf-
ficient information on (1) site selection, (2) soils and landscapes, (3)
fate of nitrogen, (4) loading rates, (5) erosion control, (6) adapted
vegetative cover, and (7) heavy metals.
A general research recommendation, equally applicable to both slow
rate and rapid infiltration systems, was that systems models be verified
by field data to help maximize the efficiency of system management and
operation. Also, the need for increased transfer of technology and for
training of managers/operators of land treatment systems still exists.
Specific research needs in all three systems are characterized below.
SLOW RATE SYSTEMS
High Priority
1. Risk assessment of potential pathogenic organism problems related to
land treatment systems as opposed to other methods of treating and dis-
posing municipal wastewater. If land treatment systems are used, a know-
ledge of how pathogens, particularly viruses, are transported 1n the soil
and groundwater and what factors affect survival time 1s essential. A
second need 1s determining the relative risk of transmission of respira-
tory viruses through wastewater aerosols compared to the relative risks
associated with other alternatives of wastewater disposal such as direct
discharge into lakes and streams.
2. Comprehensive studies of ecosystem dynamics: a. Site aging and
wastewater renovation efficacy. Most land treatment systems are designed
for a life of 20 or 30 years. As a cropland or forest land site ages,
Information 1s needed on how 1t changes 1n renovation efficiency. Most
land treatment systems 1n the U.S. are new and little long-term data are
available. The occurrence of significant changes In renovation effi-
ciency, over time may necessitate changes 1n the way that a system 1s
utilized.
b. Ecosystem collapse and recovery: In Improperly operated land
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Heport: Effluent Use
Page 421
treatment systems, the potent"fal exists for ecosystem collapse as a
result of overloading the biological system with excessive amounts of
wastewater. Ecosystem collapse is defined as the state in which the eco-
system can no longer satisfactorily remove nitrogen and other pollutants
1n the wastewater. Few land treatment systems have supplemental areas
large enough to be used should ecosystem collapse occur. Information,
therefore, is needed concerning ways to accelerate ecosystem recovery and
recovery time. In forest ecosystems, because of their continued recycl-
ing of nutrients and the less frequent removal of applied nutrients are
compared to annual crop harvests in agronomic systems, such information
is critical.
c. Study of on-site ecosystem effects: Comprehensive studies of the
effects of wastewater irrigation on the entire ecosystem should include
effects on primary and secondary productivity and on movement and distri-
bution of elements throughout the entire soi1-plant-animal complex.
Information on forest ecosystem stability is also needed.
d. Study of off-site effects: Identifying the effects of land
treatment systems on neighboring ecosystems must include a determination
of which elements are being transported and their subsequent effects on
neighboring human and natural ecosystems.
3. Study of nitrogen management 1n forest systems: Because there are
only a few forest slow rate systems in the U.S., there 1s a paucity of
Information available on nitrogen management. Unlike cropland systems
which have an annual removal of nutrients In crop harvest, forest systems
continuously recycle nutrients, often over the system's entire life.
There 1s a need to develop successful management techniques to control
nitrogen transformations (mineralization and Immobilization, nitrifica-
tion, and denltrlflcation) and cycling.
4. Prediction of nitrogen concentrations In groundwater leaving the land
treatment system: To refine and improve current methods being used for
predicting average concentrations of nitrogen in the groundwater leaving
a wastewater treatment site, there fs a need for both additional data and
the development of either better models or field verification and refine-
ment of existing models.
Medium Priority
1. Study of forest ecosystem responses to wastewater irrigation: More
Information 1s needed for the effects of wastewater Irrigation on the
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PRATT AND SOPPER
various major U.S. forest types as a function of the type soil, geology,
and climatic conditions. Such investigations might include tree growth,
blomass production, physical and anatomical properties, forest floor
accumulation and decomposition, physical and chemical changes in soil
properties, seedling reproduction, mortality, soil Invertebrates, and
microbial communities.
Low Priority
1. Study of trace organic*: There Is a need for more information on
trace organlcs in municipal wastewater and their ultimate fate on land
treatment systems. Generally, the concentrations of organic compounds in
municipal effluents will be low and have little effect on the design and
management of slow-rate systems.
2. Study of water infiltration and transmlsslvlty: There is a need for
better field techniques to determine the Infiltration and percolation of
wastewater at potential land treatment sites. Such Information 1s criti-
cal to the design of the system in terms of hydraulic loading and water
budgets.
RAPID INFILTRATION SYSTEMS
High Priority
1. Risk assessment for land treatment systems compared to that of alter-
native systems for the treatment and disposal of municipal wastewater.
For the successful application of land treatment systems, a knowledge of
the flux of pathogens, particularly viruses in the soil and groundwater,
must be developed for a comparison by risk assessment methodology with
alternate disposal and/or treatment systems.
2. Determination of the fate of trace organlcs: Because of the speed of
water flow through the soil 1n rapid infiltration systems, trace organics
having relatively slow decomposition rates are likely to move with the
wastewater streams Into aquifers or Into surface waters. The establish-
ment of decomposition rates for various organlcs and the relative flux of
organlcs versus that of water would help explain potential trace element
problems and help evaluate the suitability of effluents for rapid
Infiltration systems dependent upon the specific trace organlcs present.
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Report: Effluenl Use
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Medium Priority
]. Management of land surfaces devoted to rapid Infiltration: Applied
research dealing with management of vegetative cover, wetting arid drying
cycles, disposal of surface accumulations of organic materials and culti-
vation operations can develop techniques for improving the efficiency of
these systems.
2. Prediction and verification of hydraulics and loading rates: There is
a need to improve the procedures and techniques for site selection In-
cluding such factors as an evaluation of the water flux properties of the
soils, the underlying geological strata, and the path that reclaimed
water must follow.
3. Hanagement for nutrient removal: Field research is needed to learn
the fate of nitrogen as it 1s affected by management factors such as the
wetting and drying cycles of various soils. Retention of phosphorus
depends on soil sorption capacity and properties of the effluents that
are not completely understood and integrated into a model of phosphorus
retention.
OVERLAND FLOW SYSTEMS
High Priori ty
1. Efficiency to remove algal suspended solids: More Information 1s
needed on the efficiency of overland flow systems to remove suspended
solids after pond pretreatment and under various flow rates. Such stu-
dies should also Include Investigation of the accumulation and decompo-
sition of these solids on the soil surface.
2. Pre-treatment requirements: Investigation 1s needed to clarify the
degree of pretreatment necessary for overland flow systems; to determine
the minimum treatment needed for efficient operation of such systems; and
to learn what additional treatment 1s needed to control odors.
3. Effects of site agtng and restoration of sites after cessation of
operations: Most of the U.S. overland flow systems are experimental.
Information 1s needed on the length of time such systems will satisfac-
torily operate, and what action must be taken whert the operation ceases
and the site is converted to other uses.
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PRATT AND SOPPFR
Medium Priority
1. Efficiency of systems to remove phosphorus: Most overland flow sys-
tems inefficiently remove phosphorus and most of it is removed through
surface soil contact followed by translocation. Methods must be deve-
loped to increase phosphorus removal, e.g., by the addition of alum to
the raw wastewater stream.
2. Study of the fate of trace organics: More information is needed on
trace organics and their ultimate fate in overland flow systems. Concen-
trations of trace organics can be expected to be higher 1n these systems
than in slow rate systems, and, they may require special management prac-
tices.
3. Study of pathogen retention and movement: There is a need to study
the pathogen retention and fate of pathogenic organisms in the overland
flow system, particularly in regard to harvesting the cover vegetation
and its disposal or use. Information is also needed relative to pathogen
retention at these sites and their post-operation land use.
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COMMENTS AND QUESTIONS FROM THE FLOOR:
Robert Smith, University of Califormia, Davis: You mentioned remo-
val of suspended solide ae the high priority item fov overland flow
systems* Is this specific to algal solide? Can you elaborate on that?
Parker Pratt: One of the general papers indicated that removal of
algae was not very efficient and the workshop felt that some research
should be done relative to the removal of algae via overland flow
systems.
Robert Smith: So your specific comment concerned algae—not
suspended solids in general.
Parker Pratt: Yes, specifically the removal of algae.
A. L. Page: Parker, for the benefit of the group that may not be
familiar uith how slow rate systems, rapid infiltration systems, and
overland flow systems operate relative to the intent of developing these
systems, could you elaborate on these systems in terms of the operation
and how they are used.
Parker Pratt: I'll give my concepts and then Richard Thomas can
correct me, if necessary. In the slow rate system, the Idea Is to grow
crops where the water application is near what we would use in irrigated
agriculture in the west. The Input is slow enough so that the soil is
sufficiently aerated for crops to grow, yet fast enough to dispose of/or
treat the amount of wastewater required. A few meters of water applica-
tion are involved 1n the operation. In the west, sometimes as high as 4
to 5 meters of water are used, but the norm Is only one or two meters.
In rapid Infiltrations systems the volume 1s 30-40 meters of water
per year or more. In overland flow systems water 1s Introduced at the
top of a run. The water flow is through a grass, plant canopy or slope
and transmission time 1s half an hour; during this time phosphrous 1s
removed, there is a modification, denltriftcation and oxidation of sus-
pended solids. At the end of the flow water 1s channelled into a pond or
to an additional treatment system. So, overland flow Is part of a
system, not the end of the system,
Richard Thomas, EPA, Washington: I Want to add a clarifying addi-
tion on overland flow. Basically, it can be a complete treatment system•
It is a designated use of a specific land area for wastewater treatment.
It is a treat and discharge system so it is comparable to any treatment
and discharge system.
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Page 427
Management Considerations in Sludge Use
Lee E. Sommers, Moderator
V, V. VoTk, Secretary
Lee W. Jacobs, Co-Secretary
Participants: Dwight C. Baier, Robert Bastian, Thomas E. Bates, D. R.
Bouldin, A. Lloyd Brown, B. L. Carlile, G. K. Dotson, R.
H. Dowdy, Dennis Draman, Grace A. Draman, James 0. Evans,
Anne E. Giblin, Paul Giordano, Donna J. Griffin, Phil
Hegeman, P. A. Helmke, Charles Henry, Thomas D. Hinesly,
Wesley Jarrell, Lyle Jarrett, Y. Kanehiro, Robert F.
Keefer, L. D. King, Paul Koenlg, Shlou Kuo, D. R. Linden,
Peter S, Hachno, Milton W. Meyer, Raymond 0. Miller,
George A. O'Connor, Daniel O'Neill, A. L. Page, James
Perry, Warren Sahs, Eileen M. Seaker, Robert C. Smith,
Stanley M. Smith, J. J. Street, Dean H. Urie, Gary G. Van
Riper, J. Vlamis, D. E. Williams, Ralph Young, Susan Young
INTRODUCTION
Primarily, sludge management was discussed with respect to plant
nutrients, trace metals, organics, and systems management. Emphasis was
on cropland, but because of slightly different research needs, subsec-
tions on forest lands and disturbed soils were developed. Human health
considerations associated with the use of sewage sludge were not
discussed.
In the decade since 1973, significant advances have been made 1n
defining the benefits and the problems associated with use of sewage
sludge on cropland. Excellent yields of high quality crops can be ob-
tained when sewage sludge is substituted for conventional fertilizer
materials. Guidelines are now available to permit the environmentally
safe use of most sewage sludges on agricultural land. Improved manage-
ment practices have enhanced public acceptance and Increased percentage
of sludge utilized on cropland.
Although utilization of sludge in forest lands 1s a relatively new
alternative, existing research and development projects Indicate sludge
treatment of forests Improves forest production while maintaining
environmental quality. Because forest lands produce non-food chain
crops, sewage sludge management is relatively straightforward. On the
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SOMMERS
other hand, long-term crop cycles, slope, soil depth, and application
techniques may require development of special guidelines.
Sewage sludge is also successfully being used to reclaim disturbed
land. Less information is available on the effects of sewage sludge on
disturbed lands than its effects on cropland. Most studies show that the
proper utilization of sludge in land reclamation at application rates
higher than those used for agricultural land, will not cause degradation
of soil, groundwater, or vegetation quality. In fact, sludge application
improves the environmental quality.
GENERAL DISCUSSION
Nitrogen
In the past 10 years, significant advances have been made in utili-
zation of sewage sludge as a source of nitrogen in agricultural cropping
systems. Application of sewage sludge to cropland does not pose an in-
creased threat to nitrate contamination of groundwater, provided that the
amount of plant-available nitrogen (N) added to soils 1n sewage sludge
does not exceed the N fertilizer recommendation for the crop grown.
Existing research data can be used to determine the plant-available N
content of sewage sludge, i.e., a portion of the inorganic and organic N.
Current estimates can be used for ammonia volatilization following sur-
face applications of sludge and for organic N mineralization rates.
Methodology is available to advance our knowledge of N transformations in
soi1-sludge-plant systems.
Phosphorus
The application of sewage sludges to cropland at rates consistent
with nitrogen fertilizer recommendations will probably result 1n phos-
phorus (P) additions in excess of those needed for crop growth. Such
excessive additions in sewage sludges are of concern due to the potential
for P entry into natural waters resulting in eutrophlcation. Phosphorus
leaching is not a problem In the majority of mineral soils with possible
exceptions being organic or selected sandy soils. Reduced plant growth
due to excessive soil P is not a serious problem. Established soil test-
ing procedures can be used to monitor available P accumulation in sewage
sludge-treated soils. To minimize P problems, sewage sludge applications
can be based on the P rather than N fertilizer recommendation for the
crop grown.
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Trace Metals
Trace elements, such as Cu, Zn, Mo, and Fe, present in sewage sludge
that is added to agricultural soils at agronomic rates, can alleviate
micronutrient deficiencies in plants. An increase in plant trace metal
content following sewage sludge application can also reduce the need for
supplements of the above trace elements, plus Se, in animal rations. In
general, current guidelines for the cumulative application of Cu, Zn, and
Ni are safe but should be refined to reflect regional soil differences.
Many current guidelines use soil cation exchange capacity (CEC) to
limit metal (Zn, Cu, and Ni) additions to soils. However, the CEC may
not be the most appropriate soil parameter to use in all regions of the
U.S. Specific soil properties (i.e., texture, organic matter, iron
oxides) are important and should be considered when limits for cumulative
metal additions to soils are established. Total cumulative application
of trace elements should be based on both the amount added in sewage
sludge and the available metal content 1n the soil prior to any sludge
application.
The majority of sludges do not contain excessive levels of Se or Mo.
Some trace elements (Se and Mo), however, may be assimilated by plants
grown on sewage sludge-treated soils at levels sufficiently high to cause
animal health problems. Sufficient quantities of elements, such as Cu,
Se, and Pb, may be ingested by livestock while grazing plants grown on
sewage sludge-treated soil and thereby cause animal health problems.
Livestock consume fair quantities of soil while grazing.
Organics
Concentrations of the majority of synthetic organic chemicals 1n
sewage sludges are generally low. Most organics added to soils fn sewage
sludges will be decomposed within one growing season, with the exception
of recalcitrant compounds (e.g., PCB's). Current federal regulations for
polychlorlnated blphe'nyl compounds in sewage sludges are adequate to pro-
tect animal health.
Management
Recommendations for sludge application rates are based on periodic
analysis of plant nutrients and trace metals in the sewage sludge.
Currently, insufficient information exists to Integrate organics into the
design of systems for sludge utilization on agricultural croplands.
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SOMMFRS
No groundwater monitoring for nitrate is needed where the plant-
available N in sewage sludge does not exceed the fertilizer N recommen-
dations for the crop grown.
Good soil and water conservation practices should be utilized at all
sludge application sites to minimize erosion losses and surface runoff,
and thereby reduce the potential non-point source water pollution.
RESEARCH NEEDS FOR SEWAGE SLUDGE USE IN AGRICULTURAL CROPLAND
High Priority
1. Establish phytotoxic limits of Cu, Zn, and Ni applied 1n sewage
sludge and evaluate residual plant availability of metals following ter-
mination of sludge applications. Emphasis should be placed on regional
soil differences (clay type, iron and aluminum oxides), and management
practices, (crop grown, pH).
2. Develop models to predict and further refine estimates of N behavior
1n sewage sludge-treated soils, with emphasis on ammonia volatilization,
organic N mineralization, and denltrlflcatlon.
Intermediate Priority
1. Investigate the fate of organic chemicals in sewage sludge applied
to soils with respect to (a) decomposition and mobility 1n soils, and (b)
potential accumulation In plants and animals. Methods to study the fate
of organlcs need to be developed.
2. Identify metal reactions between the soil-plant Interface to deter-
mine metal avallabllty to plants and animals. Establish thermodynamic
properties of the system 1n addition to empirical observations.
3. Evaluate soil tests, perhaps on a regional basis or as a function of
specific soil properties, to relate soil metal levels to plant uptake or
phytotoxlclty. Existing soils tests are applicable for detection of
trace metal deficiencies rather than phytotoxldtles.
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Report: Sludge Use
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Low Priority
1. Determine effects of sewage sludge on specific microbiological pro-
cesses In soils and plants such as legume Inoculation, plant disease, and
nutrient transformation.
RESEARCH NEEDS FOR SEWAGE SLUDGE USE ON FOREST LANDS
High Priorlty
1. Quantitatively determine N cycling In forest lands so valfd criteria
can be developed for sludge utilization.
2, Develop sewage sludge application and management techniques Including
metal limits, surface runoff leachate quality, and other site selection
criteria.
Low Pri ority
1. Evaluate metal effects on the forest ecosystem. Including the flora
and fauna.
2. Study the long-term response of trees to sewage sludge.
3, Determine the effects of sludge use on physical properties of wood.
RESEARCH NEEDS FOR SEWAGE SLUDGE USE ON DISTURBED LANDS
High Priority
1. Determine types of sewage sludges and optimum rates of application
for establishment of permanent and self-maintaining vegetative cover on
drastically disturbed land.
2. Determine the responsiveness of plant species to relatively high
loading rates of sewage sludge as well as their tolerance to the adverse
conditions of disturbed land. In selected regions, the response of
native plant species to sewage sludge 1s needed.
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SOMMERS
Low Priority
1. Develop better management techniques for land reclamation with sewage
sludge, e.g., depth and method of incorporation into soils, methods of
establishing woody species 1n conjunction with grass-legume cover and
monitoring approaches.
2. Determine the effects of sludge incorporation on soil formation pro-
cesses 1n barren soil materials, the rate of re-1nvas1on by microorga-
nisms and Invertebrates, the longevity of the newly formed soil system,
and the development of plant root systems.
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Page 433
QUESTIONS MD COMMENTS FROM THE FLOOR:
Donald S. Aulenbaehj, Reneeelaer Polytechnic Institute: Vas the
lim-b of PCB's in sludge for land disposal ID ppm or 10 ppb?
Lee Sommers: We developed a general statement concerning the PCB
limitations for the U.S. EPA regulations published 1 rt 1979. This regula-
tion states that sludges containing >10 rag PCB/kg sludge (i.e., 10 ppm)
must be incorporated into the soil rather than surface applied.
Donald Aulenbaeh: That i& adequate, we shouldn't put very etriat
limits on PCS'# in sludge until ise have more positive proof that PCB 'e
are ^harmful to our health.
Lee Swtmers: Fortunately, the majority of recent sludge cowpDSiliw)
surveys indicate that most sludges contain significantly <10 mg PCB/lcg.
Leon Cheenin, University of Nebraska: What level of nine applied ae
kludge was aonei&ered to be tcxic? Researah at the Panhcndle Experiment
Station at Mitchell, Jfebnska indicated that 1230 lbs/acre cf Zn banded
as sine sulfate on irrigated corn was not toxia-
Lee Sommers: We tried to address general issues In our workshop,
there was rrct sufficient tine to address items such as specific limits on
metals. With r&spect to specific limits, I refer you to Individual mem-
bers of our group and also to regulations or guidelines that have been
developed In states or regions of the United States. Most workshop mem-
bers expressed a belief that metal limits should be related to regional
differences in soil characteristics. Other studies will support your
conclusion.
Date Sakert Pennsylvania State University; Monitoring requirements
for disturbed lands need to be refined and related to desirable sludge
rates and properties. The future nee of the eite should relate to
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SOMMERS
Suaan Young, INCOG, Tulea, OK: (1) Did your group discuss a total
management program, including pre-collection system treatment (industrial
pre-treat), and/or bulking all sludges that we cannot now land apply, and
other sludge disposal options. Do you have any recommendations for these
non-agricultural management aspects? (2) Did the group address non-mined
disturbed lands (construction areas, elope stabilisation, oil field/brine
damaged lands) ? Were application methodologies, rates, or special
problems discussed? Are there any recommendations for further efforts in
this area? Are there recommendations to take in the problems for dis-
turbed/marginallands (low pH, high salts, shallow soils, etc.)?
Lee Sonmiers: Part 1. We only addressed land application of "accept-
table" sludges. Pretreatment programs and other sludge disposal options
were not discussed. Part 2. A fairly small number of people were con-
cerned with disturbed lands. If anybody 1n our group would like to
respond to this question, please feel free to do so. The research needs
stated were for disturbed lands in general.
Lee Jacobs, Michigan State University: Suggestions on research
needs for disturbed lands would be welcomed.
Gerald Stern, WPA Cincinnati: In the management workshop - was
sludge disposal on dedicated land sites considered?
Lee Sommers: No. We mainly discussed systems where sewage sludge
1s used as part of an agronomic fertilization program. In general, when-
ever sludge 1s applied in excess of agronomic rates, more extensive moni-
toring such as nitrate In groundwater and metals in crops are needed.
Specific management practices needed on a dedicated site were not
discussed.
Stephen B. Smith, Black & Veatch, Denver, CO: Lee, you made a com-
ment to the effect that we need to establish species of plants for
disturbed land reclamation. This may be the case for several parts of
the country, however, this is not the case for the Colorado and Wyoming
area. The Mine Land Reclamation Board of Colorado, and the Land Quality
Division of Wyoming Department of Environmental Quality dictate the plant
species that have to be used. Therefore, the issue becomes how well will
these plants germinate and grow an eludge-amended soils, and whether or
not they can sustain the vegetation into the future. I would submit to
you that a research need exists to determine the effects of sludge appli-
cation an these native semi-arid species for use in the western United
States.
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Page 435
Lee Sommers: We appreciate your comment.
Terry Logan, Ohio State University: Should the same metal accumula~
tion criteria be used for disturbed land and agricultural land? This
question relates to currently disturbed land that is reclaimed through
sludge applications and then, at some point in the future, is used for
agricultural crop production.
Lee Sommers: This 1s a very Important consideration. Unfortu-
nately, the management group had insufficient time to address this topic.
Melvin Webber, Environment Canada, Burlington, Ontario: {1J Did the
group concerned with sludge management consider defining maximum per-
missible heavy metal contents in sludge for agricultural use? (2) Would
the chairman of the sludge management group elaborate on the groups'
discussion concerning soil CSC in relation to heavy metal loadings? (3)
Did the sludge management group define the heavy metal contents of a
median sludge? I realize that Logan and Chaney in their paper presented
at this conference define median sludge, but does the group agree with
their definition?
Lee Sommers: Part 1: There was basic agreement that we definitely
minimize problems by applying low metal or low organic sludges, i.e., the
"median sludges" that have been discussed in several of the papers at
this workshop. We did not specifically address upper limits for sludge
constituents such as metals. The general consensus of the group was that
current metal guidelines are appropriate 1n the future. That 1s, we
should limit the amount of metal added to a soil rather than limiting the
metal concentration in the sludge. We did not try to evaluate specific
limits for metal additions to soils.
Melvin Webber: In this regard, I might add that most other
countries, who have guidelines for sludge use in agriculturet have
defined maximum permissible heavy metal contents of agriculturally accep-
table sludges. However, considerable Variation exists in the maximum
acceptable levels for sludge constituents. Using sine as an example, the
maximum for different nations -varies from 2,000 mg/kg to 10,000 mg/kg.
Lee Sommers: As a general comment, some data suggest that less
metal uptake by plants occurs with low metal sludge than with high metal
sludge, when both are applied at rates to add equal amounts of a metal to
soil. Perhaps, a combination of the two approaches 1s needed.
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SOMMERS
Part 2 - The majority of workshop participants Indicated that soil
properties are important relative to limits for total metal additions to
soils. Cation exchange capacity was originally selected for use in set-
ting limits because (a) it is an easily measured soil parameter, and (b)
it is positively correlated with the soil components (i.e., organic mat-
ter, iron oxides, and clay) that tend to minimize the solubility and
plant availability of metals in soils. It was never intended to imply
that metals added to soils in sludges are retained through a cation ex-
change mechanism, Metals added to soils in sludges are essentially 100%
insoluble and are not present as exchangeable cations. It is now recog-
nized that the CEC approach fails in some regions of the U.S. Soil tex-
ture may be more appropriate 1n some areas. The CEC does not have any
relationship whatsoever to potential metal problems in calcareous soils.
The CEC approach was developed in the mid-70's for the north central re-
gion of the U.S. where organic matter is the major contributor to cation
exchange. It is now realized that pH Is more important than CEC in con-
trolling metal uptake by plants in all regions of the U.S.
Part 3 - It was my impression that our group was in agreement with
the definition of a median sludge proposed by Logan and Chaney in this
workshop. The group did not formally adopt the Logan and Chaney defini-
tion.
Harvey Luce, University of Connecticut: Did your group consider
site criteria, site evaluation, site selection as a consideration to
sludge management use?
Lee Sommers: The Items discussed relative to site management would
include soil pH control and practices to minimize surface runoff and soil
erosion so sludge materials would not be transported to surface waters.
We did not discuss specific limits on slope.
Harvey Luce: I was thinking site selection, especially as it rela-
tes to forest lands, These sites may have steep elopes or soils that are
shallow to bedrock. If we are going to apply sludge to forest lands, it
will be applied to sites that have one or more of these less than ideal
conditions. This area appears to be a major research need.
Lee Sommers: One of our highest research needs was additional In-
formation on site selection and management practices for sludge use 1n
forests. We support your statements.
Jack Cooper, national Food Processors Association; Did your group
address the need for records on such things as: site locations where
sludge was applied, and soil CEC data? Did you discuss the need for
these data to be available to the public? Did you discuss the assignment
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Report: Sludge Use
Page 437
of responsibilities to make sure that all parties accomplish their
assigned tasks? Did you discuss whether there should be a mechanism
available to assign responsibilities?
Lee Sommers: The general feeling of our group was that records must
be compiled and maintained to comply with current guidelines and regula-
tions on cumulative additions of metals to soils. Records must be
available to determine if a metal limit is being approached. Vie did not
discuss liability.
A. L> Pagej University of California, Riverside: I believe the
question relates to the need to "keep records where sludge hae been
applied and the need to keep records of the composition of the sludge
applied there. Any efforts along thoee lime?
Lee Sommers: Since the guidelines currently used in most states are
based on cumulative metal additions, records on sludge composition and
sludge application rates at different sites must be kept.
Lee Jacobs, Michigan State University: Since philosophies are dif-
ferent between regions and approaches to technical matters (e.g., fer-
tiliser recommendations for crops) are different between states, it ie
difficult to develop a national statement on sludge management. We felt
that regional concerns and regional differences in soils are best handled
by individual states. Record-keeping probably ie needed in all regions
of the U.S. because of the need for lirftits on total metal loadings.
Lee Sommers: In general, the group feels that we know how to manage
the sludge utilization systems for cropland and that we are fine tuning
the basic approach. The basic approach is the same from Maryland to
California, but specific number may vary.
Dale E. Baker, Pennsylvania State University, Chairman, NE Work
Group: For the management group, I would urge you to consider problems
and solutions on a regional basis. Soils are different, people con-
straints are different, and the requirements in relation to total or
available land change. For example, in the northeast a permit may
involve a 20 acre field, compared utith up to 2,000 acres at other loca-
tions. The geochemistry effects must receive more emphaeie.
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Page 439
Public Health and Risk Assessment: Pathogens
Elmer Akin,
Wylle Burge,
Bernard Sagik,
Moderator
Secretary
Co-Secretary
Parttcipants: Donald Aulenbach, Gerald Berg, Scott Clark, Robert C.
Cooper, D. J. D'Alessio, C. R. Dorn, Samuel R. Farrah,
Jane Forste, Paul Fitzgerald, Charles Gerba, Thomas L.
Gleason, III, Charles Hagedorn, Tom Holm-Hansen, George
Jackson, Barbara Ann Kerdolff, M. Dale Uttle, Ebba Lund,
Gordon A. McFeters, Barbara Moore, Robert Northrop, R. T.
O'Brien, Mark Sobsey, Charles Sorber, Gerald Stern,
Richard Ward, Willis Whitfield, William Yanko
The Pathogen workshop participants support the concept of land ap-
plication of domestic wastes. With proper management and reasonable
safety allowances based on sound research data, we believe that land ap-
plication can be a safe, beneficial, and acceptable disposal alternative.
However, three potential routes of exposure to pathogens 1n wastes ap-
plied to land are recognized, I.e., (1) direct contact with waste-amended
soils, (2) aerosols from spray application, and (3) ingestion of con-
taminated surface-runoff water and groundwater.
Currently, there are no known outbreaks of Infectious disease attri-
butable to land application of wastes. This Is not to say that no cases
of Illness have occurred. Disease produced by a common source exposure
are not typically obvious by observation. Systematic study by epide-
miological investigation is generally required to "prove" the occurrence
of a common source outbreak and to identify the likely source.
The documentation of sporadic cases of illness from a common source
environmental exposure is a different question and no satisfactory Inves-
tigative approach 1s available to obtain these incidence data. Therefore
the documentation and quantitation of health risks from the three poten-
tial routes of exposure 1n domestic wastes applied to soil 1s beyond the
current state-of-the-art.
Efforts to gain these data were obviously the objective of research
needs identified by the 1973 workshop participants. The participants at
the 1983 workshop believe that the current needs generally remain the
same as those Identified by the 1973 workshop with perhaps different
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AKIN
priorities arid emphases. This is not to say that nothing has been
accomplished in the past 10 years. On the contrary, much has been accom-
plished. Major epidemiological studies have been or are now being con-
ducted to determine the microbial health hazards of wastewater spray irri-
gation and sludge application. Major Improvements in monitoring methods,
especially in the virus area, have been achieved. These methods, applied
to field studies, have documented significant migration of pathogens In
the soil subsurface and groundwater. Data generated during the decade
since the 1973 workshop have provided a scientific basis for developing
sludge disposal criteria at the federal level.
The considerable progress achieved will allow a more rapid rate of
progress in monitoring for the occurrence of pathogens in a wide variety
of environmental media, i.e., water, wastewater, sludge, and soil.
Emphasis can now be placed on quality control and quality assurance
aspects, on standardization of methodologies and on a general improvement
in the comparability of data from one study to another. From these deve-
lopments, the data generated will likely produce more definitive trends
in predicting microbial behavior 1n the environment. Compared to 1973
capability, a more accurate indication of "what is out there" and "how
many" in terms of treatment effectiveness and pathogen transport can more
readily be determined.
In terms of current detection capability, the sludge disposal cri-
teria (Federal Register, September 13, 1979) is considered adequate to
protect the public health from infectious disease via this transmission
route. Perhaps the most likely attack on these criteria will be from the
standpoint that they are overly restrictive. Data must be generated that
will give guidance to any consideration for the relaxation of these cri-
teria.
Participants in this workshop believe that considerable research
Information 1s now available to conclude that site specific criteria and
management guidances are warranted. Meteorological and soil-type varia-
tions yield significant differences 1n microbial survival and behavior
when applied to land via domestic wastes.
Epidemiological studies were given a top priority research need by
the 1973 workshop participants. Important studies have been conducted
and the results are becoming available for making generalized hazard-
assessment decisions. It Is believed that the epidemiological approach
to determining microbial health hazards from land application has been
adequately applied to those exposure circumstances where statistical ana-
lysis of data can be applied. Some studies directed to high exposure
populations (worst case situations) may still be appropriate. However,
this workshop does not believe that epidemiological studies remain as the
highest research need.
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Report: Pathogens
Page 441
Workshop participants believe that major resource allocations should
focus on work that would allow a more accurate prediction of pathogen
exposure and illness outcome through modeling approaches. The influence
of specific actions, e.g., various levels of pretreatment, on the level
of risk could be evaluated and may Indicate more cost-effective treatment
/disposal options.
In order for this approach to be meaningful and to avoid the erro-
neous conclusion drawn from faulty modeling exercises, the following spe-
cific research needs are identified by the workshop in order of priority
per microbiology discipline:
RESEARCH HEEDS
Bacteriology
1. Determine survival and regrowth of established human pathogens (e.g.,
Salmonella) and newly recognized waterborne pathogens (e.g., Campylo-
bacter, Terslna) 1n sludge and in soils amended with sludge and waste-
water.
2. Improve methods for detection, enumeration, and assessment of viru-
lence of these pathogens 1n sludge and wastewater*
3. Determine effectiveness and mechanism of action of treatment pro-
cesses 1n reducing pathogens 1n sludge and wastewater.
4. Determine relevance of existing Indicator organisms as Indicators of
the presence of new pathogens.
5. Identify factors and determine survival and translocation of patho-
gens and indicator organisms 1n sludge-amended soils under different
Infiltration rates and 1n different soils.
Epidemiology
1. Conduct comprehensive studies of "worst case" exposed populations,
e.g., sewage plant workers and families. Determine occurrence of proto-
zoan, helminthic, bacterial and viral infections with a focus on
gastrointestinal illness.
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AKIN
2. Conduct studies of compost-site workers for occurrence of Aspergillus
fumlgatus Infections.
3. Determine infectious dose of pathogens, especially differentiation of
respiratory and 1ngest1ve routes.
Parasitology
1. Determine pathological effects of repeated low level Ascarls Infec-
tions.
2. Determine virulence of swine vs. human Ascarls and Importance of
cross-1nfect1v1ty 1n alternate hosts.
3. Determine potential pathological significance of Naeglerla and simi-
lar organisms In waste-treated soils.
4. Determine Important factors affecting survival of Ascarls ova 1n
sludge-treated soil and develop die-off curves under various meteorolog-
Ical conditions.
V1rology
1. Conduct site monitoring studies of survlal and movement of viruses
applied to land under wide ranges of climatic, hydrologlc and waste con-
ditions. Quality assurance of field data should be given high priority.
2. Determine effectiveness of sewage treatment processes before land
application, especially disinfection, for virus reduction to acceptable
low levels.
3. Develop design and operational criteria, e.g., loading rates, hydro-
logy, soil characteristics, groundwater use, and crops grown, for land
application systems with respect to viruses.
4. Develop methods to detect those enteric viruses that are known to
cause human Illness from fecally-contam1rated water and wastes but are
presently difficult to cultivate or as yet not cultlvatable, e.g.,
Hepatltus A virus, Norwalk-type viruses, and rotaviruses.
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Report: Pathogens
Page 443
5. Develop methods of high and defined efficiency {quality assurance)
for the more easily cultivate enteric viruses 1n wastewater, sludges,
soil, and groundwater associated with land application systems.
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AKIN
QUESTIONS AND COMMENTS FROM THE FLOOR:
Charles A. Sorber, University of Texas; I eat in on that group and
I want to say that your summary of the consensus was excellent. I don't
think anybody is going to argue with your summary, but I know you inad-
vertently missed one of the items that I think is important as you ran
down through the slides. Perhaps Woody could put that Virology Section
elide up.... Note that item dealt with development of criteria based
on what we have learned in the last 10 years and I think that this ie
particularly important to this group. You might want to go over that
particular topic. You just ran by it inadvertently, Elmer.
Elmer Akin: I'm sorry, I did miss that. Again, I think a major con-
cern here, and I would like the virology group spokesman to comment on
this is that there is a need for site-specific criteria. Dr. Wellings,
from the State of Florida, Dr. Vaughan from Long Island and investigators
from other places that have sandy soils, have produced a fair amount of
data on the movement of agents through that type of soil and it is the
specificity of these data that needs to be taken into consideration. I
would like for the virology group to comment on that further.
Anne Giblin, Woods Hole Oceanographic Institution: Some studies in
a marine environment have shown that bacteria isolated from sewage
dumping areas have a higher incidence of antibiotic resistance than bac-
teria from other areas. Do you think this is a problem?
Elmer Akin: I didn't hear you very well. A higher Incidence of
antibiotic resistant bacteria? What source?
Ann Giblin: Yes, from sewage dumping areas.
Elmer Akin: I think it 1s becoming very well documented that sewage
does provide a medium for the transfer of plasmid-medlated antibiotic
resistance. It 1s somewhat debated among bacteriologists what the real
significance of this observation 1s, 1t perhaps has been ongoing for a
long time. Since antibiotics were introduced 1n this country, physicians
have used them freely to treat most everything Infectious. I don't know
the health significance of this observation. We didn't really address
that in our group. Anybody want to respond?
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Bernard Sagik, Drexel University: Reluctantly. At the 1981 Plasmid
Conference in Santo Domingo, the issue arose. Natural levels of anti~
biotia resistance, particularly in South and Central America and third
world countries, was even greater than among the isolates that were seen
in the United States and that was pretty darned high, as most of you
know. Out of that came a statement by the group, circulated very widely
at the time by all persons at the Santo Domingo Conference, urging
research workers and physicians to begin to be cognisant of the potential
health risk of letting all of these organisms, and the potential for
plasmid exchange, loose in the environment. The concern was not because
of the "bugs" as much as because of the loss of effectiveness of anti-
biotics which physicians had depended on for almost 30 years. More
recently, Stuart Levy started a group which is soliciting support for
control of and conservative use of antibiotics. You may even see Public
Health and Preventive Medicine mike a come back from this.
Elmer Akin: Just one quick comment. I suppose we can have some
confidence that even though the transfer of antibiotic resistance does
not occur, we still have disinfectants that don't recognize this
resistance.
Lee Sommers, Purdue University: Did your group address relative
risks? Currently, wastewater treatment plants are discharging effluents
directly into rivers and other surface waters that nay serve as drinking
water supplies. What is the relative risk of having a few virus perco-
lating into a groundwater from a wastewater utilisation site as opposed
to putting all viruses directly into the surface water?
Elmer Akin: We talked about 1t, and we've talked 1t before. In
fact we almost started at that point because the discussion of every
meeting of microbiologists, particularly virologists, comes down to this
point. How do we determine relative risk and how do we obtain the evi-
dence that 1s really needed to prove or disprove a health hazard from
these agents 1n the environment. We basically have two approaches: epi-
demiological Investigation and some type of modeling based on agent
transport and Infective dose data. That's a more Indirect approach to the
question. The epidemiology approach does have limitations. It 1s dif-
ficult to separate risks at low levels of common-source exposure to
microorganisms for the background risk from all other exposure routes. I
don't know that I can go much farther 1n responding to your question
other than to say that microbiologists would like for you out there to
agree that if we show that the agents are commonly present 1n the
environment, distant from pollution sources that this Indicates some
level of risk. The risk may be acceptable but the data should not be
swept under the carpet. The more agents that are out there, and we are
finding more because our methods now are better, the greater the risk to
some degree--some undetermined degree. The more the environment becomes
"saturated" with organisms the greater the possiblity of exposure. The
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acceptabi 1 ity of risk is a subjective question--1 don't know if we can
approach it through objective research studies. At least, we haven't
done a very good job of it to this point.
Herbert Pahren, EPA, Cincinnati: Elmer, I would like to point out
that several years ago, Met calf and Eddy made an attempt to determine the
relative risk and perhaps either Crites or Pound are those in the room, I
believe, might want to comment on the results of their study on that
question.
Ron Crites, George Nolte and Associates: What we did wae to compare
the relative risks from activated sludge with stream discharge to a slow
rate land treatment system. Dr. Bob Cooper wae involved in the analysis
with us. Hie conclusion Dae that in terms of pathogens, the relative
risk of exposure for the public is about the same from these two systems.
Charles Gerba, University of Arizona: You made a comment that epi-
demiological studies on plant workers, which you considered the worse
case, would give ue an idea of nek to the general public. I really
can't agree with that because I am wot aware of wastewater operators and
sludge operators eating or drinking wastewater and sludge. I would con-
sider direct ingestion the worse case example of what we are trying to
protect the public from. I don't think we have evidence to indicate that
the results from those studies can be used to indicate the risk to the
general public. What it does tell us is the risks to the plant workers.
T believe they are aware of potential hazards they are working with but 1
don't think we can make that type of statement or use the evidence to
indicate risk to the general public.
Elmer Akin: Scott, you are surely going to respond to that.
Scott Clark, UC Ohio (Kettering Laboratory, Cincinnati): I think
there are ways where the exposure is comparable. There are several stu-
dies besides ours that have shewn am increased risk of illneee in waste-
water workers as -indicated by excess gastrointestinal illneee such ae
diarrhea. Now, some of this disease could be due to the hy genus habits
at the plant or in the collection system—lack of good wash rooms, lunch
roome, etc. Workers could be, in effect, eating some of the wastes
attached to contaminated food, or by smoking. Airborne aerosols and dust
in some of the wastewater and sludge treatment environments that T have
seen are at high enough concentrations to literally amount to "eating"
the waste. We thought that this population was the worse case in many
respects. There is difficulty in doing the studies at land application
sites where the exposure isn't usually as great. Although, we heard last
night from Bob Northrop that seme of the families in the farm studies,
where the kids get on the field right after they are spraying, did
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experience some illness. So, maybe there are some possibilities for
further study there. There have been several studies recently, one in
flew York city and one each in France and Germany, that do show an excess
of infections from the parasites>
Elmer Akin: Your understanding that we're talking about where we
may find a worse case situation. We don't always know what the worst
case situation 1s and Chuck takes exception to the fact that sewage
treatment plant workers are a worse case example for those living around
a sewage treatment plant or drinking water that might come from jch land
application sites. You know, Chuck, that 1s an open question to some
degree.
Jack Cooper, national Food Processors Association: I have a comment
or perhaps a question concerning the relative risk of viruses discharged
into surface water versus those that may get into groundwater. When sur-
face water ie used as drinking water it goes through a filtration and
chlorination system before it is drunk whereas groundwater often is used
straight out of the ground without any treatment whatsoever and ie con-
sidered to be very clean good water. I'm not sure that you are equating
apples with apples here—you've got apples and oranges.
Elmer Akin: Well, that's true to some degree. 1 think perhaps we
are moving tn the direction of less confidence that groundwater is micro-
biological ly safe. The data that some of the virologists are generating
indicate that viruses do move through certain soil types further than we
had anticipated and that perhaps groundwaters are in some jeopardy from
surface microbe contamination. This concern is addressed several ways.
One 1s to try to Identify sole source drinking water aquifers and not
allow any contamination or at least be more restrictive 1n potential risk
of contaminating those aquifers and another is to concede that some
groundwater sources are contaminated and anyone drinking water out of
those are advised to treat that water—at least disinfection. I think if
our group had to prioritize, groundwater contamination is perhaps one of
the greatest areas of research need and perhaps the greatest potential
health risk from land application of wastewater.
Paul Fitzgerald, University of Illinois: Near the end of our
session last night, we had a lively discussion about what does risk
really mean. I think this might be an interesting area to bring up to
this general group. Does risk imply "disease" in itself or does risk
simply imply "infection" with any particular organism. It seems to me
that this is a point that needs to be further defined. It has been
kicked around for a long time, trying to decide what risk asessement is.
If we don't have a definition of what risk really implies, I don't see
how we can ever come up with an idea of determining what -risk assessment
is. I would kind of like to hear some comments from the general group.
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Elmer Akin: Anyone care to address that? Paul, I'm not sure you're
going to get comments.
Herbert Pahven, EPA, Cincinnati: I'll make a comment. In my brief-
case I brought along a memo from Elizabeth Anderson, the Director of the
Office of Health and Environmental Assessment, Research and Development,
Environmental Protection Agency in Washington, entitled "Suggested
Definitions for Risk Assessment and Related Terms" that includes a defi-
nition of health risk assessment in lay terms. It might be of value.
Health risk assessment: Risk assessment may be used to determine (1)
the likelihood that an environmental agent may cause human disease
(e.g., potential to cause human cancer), and (S) on the assumption
the agent causes a particular disease, the magnitude of the likely
impact on public health in quantitative terms, given current and
projected exposure levels.
I don't know whether that helps, Paul or not•
Elmer Akin: I'll just make one comment on that. I think that at
times we've been criticized for doing epidemiological studies for which
the endpoint is infection rather than Illness. Some would say, so what.
Are infections really risk? Is that really documenting a concern to
health? I think this endpoint gives the epidemiologists and microbiolo-
gists perhaps a more objective way of looking at risks. Because the
infection rate 1s going to be higher then the Illness rate, we are more
likely to find a result. When we obtain these data we can likely corre-
late the ratio of infection to illness, e.g., one illness to 100 infec-
tions. Infection data are available for many of the agents. Perhaps the
Infection itself is not the risk but it allows us to project the Illness
risk in a more objective manner.
Cecil Lue-Hing: Metro Sanitary District, Chicago: First, I must
thank the workshop participants for at least listening to my comments of
yesterday. I would like to stress, however, that it was never my inten-
tion to put down the research, the researchers, or particularly those
involved in microbiological research. I do represent a constituency that
has always supported research. Particularly, I have, if you will, served
as your envoy in places like Washington, D.C., appeared before groups
such as the Appropriations Committee, and tried forcefully to encourage
Congress to put more money into research. I hope that I can continue to
do that. The caution that I would like to urge, is this: in today's
environment, we're in a tremendous competition for funding. In any cor-
porate budget any item appearing under research gets severe scrutiny.
There is a perception being developed, perhaps more so in the consti-
tuents that I represent, that we may not be getting much benefit from the
research we are paying for. It would be helpful for the people I repre-
sent who are payers of all sorts of bills to know that we are facing some
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Page 449
problems. It would be especially beneficial if the research could serve
as medium to improve the conditions under Which we are operating. Parti-
cularly, in keeping the environment protected, perhaps at a lower cost.
If as researchers we are unable to do that, the perception will grow that
perhaps we should not invest more in research because if we are as pro-
tected now as we can ever be, how much more protection can research offer
us. If the perception further develops, it could very well be that the
influential part of the constituency, that researchers need for their
support, may view additional requests for research bluntly as self-
serving. I hope we never get that far. And I hope that I can still
serve as an envoy of my constituency to continue to support it. I intend
to do that as long as I'm permitted to do so. I do believe strongly in
the need for research both long-term and near-term, The difficult part
about research is justification. And unfortunately, that is the area in
which most of you are focused. Ve need help from you the researchers, to
continue to support you, and I hope you can understand that and hope you
can take these comments seriously.
Elmer Akin: Thank you, Cecil. I knew you would have to respond to
my comment, and I was afraid you had left the room since you weren't the
first to the microphone. I do appreciate your position and I know that a
lot of sludge 1s generated every day in Chicago and your organization
must dispose of 1t and you want to do so in a safe manner. Microbiolo-
gists have gone on record here as saying that we support the land appli-
cation of wastes and we feel that 1t can be done appropriately. I think
I can say quite confidently that we aren't here to undermine or create
artlflcal risk but realizing that there is a large amount of waste and
that controlled managerial design activities are not perfect 1n all
cases. We feel the obligation of stating what needs to be done to pro-
tect the public's health from microbiological contamination and also
state that we have not had perfect tools to find out. This last decade
has seen tremendous progress 1n giving us some of those tools. We aren't
there yet but I believe 1n the next decade, Cecil, there will be a lot
more usable data coming forth. The data may very well be on the side of
relaxing some of these regulations, but we want to believe that we have
the support of other Interested parties to allow us to continue that work
and candidly, I don't know that we felt we were hearing that here. The
Idea that all the answers are not In seems to be somewhat of a common
belief, now. This may sound like a real self-serving statement but and I
don't mean 1t to be that. Man's relationship with microorganisms is a
very dynamic one--1t changes constantly because both are living, evolving
beings. We find microbiological agents a problem today that were not a
problem 10-20 years ago. Giardia Iambila was almost considered as normal
flora 1n this country 20 years ago~ Now we know 1t causes a major water-
borne disease problem, giardiasis. Now we are concerned about the water-
borne transmission of that d1sease--not only 1n the outbreak setting but
the background level as well. We will never be done with research on the
relationship between man and microorganisms and I would hope that there
1s not the perception that one day all answers will be 1n and that micro-
biological research will no longer be needed. The evolution of
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AKIN
relationships between these two life forms means that we will continually
need to study those interactions if we are to protect the public health.
Bernard Sagik, Drexel University: I certainly endorse that state-
ment, Elmer and I would like to state very briefly something that Dr.
Lue-Hing brought out. When Cecil said that some of the questions raised
10 yrs. ago are long-term problems,and we are still asking them, I think
perhaps he has forgotten that 10 and 12 years ago tie did not know, in
many oases, how to isolate viruses from the environment. When they were
first isolated and reported at meetings, people said, how do you even
know that they're viruses. How do you knou that they're not toxic agents
on those sell sheets; can you pass them; can you identify them? We've,
aome a long way since that point. There were questions as to whether you
could ever find viruses percolating through the soil because everyone
told us that that didn't happen. I think we accept the fact that it does
happen now. The questions that Cecil has raised are legitimate but T
don't think it is the duty of the person doing the research necessarily
to lower the cost.
Cecil Lue-Hing: I understand where researchers comes from, and I
hope you never misunderstand the statements I used in reference to
lowering the cost or making the bureaucratic burden any lees. This is a
perview of another group. For example, if by lowering the cost you
interpret that to mean making the regulations more workable that is not
your job. I am not here to ask you to do that. What I am here to ask
you to do is condense the work of the last 10 years and objectively and
honestly say to us did you learn anything and if you did, does it give us
an opportunity to revisit some of the decisions you have made, some of
which may have gotten into the regulations. The issue of regulations is
not your concern, and for Cod's sake don't interpret my comments to mean
that. I am asking you to look at your data and tell us if your findings
indicate to you that the risks are there, or is there need for change,
revisiting, re-evaluation, that's all. The end result of that is not
your concern. You continue to do the science.
Elmer Akin: Cecil, I can clearly say that the last 10 year have
produced certain progress in our capability to study that question. I
don't know that it has helped us to determine the risk if you mean by
that, can we give you a number or give you some tangible risk evaluation.
Hopefully that will come, but 1t 1s going to be very difficult, to really
pull a number out of the air or even perhaps to develop a standard. Take
virus exposure as an example. To say that that exposure below a number
1s safe, and exposure above that number represents considerable risk for
a large percent of the population 1s a difficult concept. I will ask you
to bear with us. I think we are generating some very valuable data on, If
nothing else, occurrence of organisms in the environment.
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Mark Sobsey, University of North Carolina: I would like to respond
to this recent dialogue and to the desire by gome for the microbiologists
to try and summarise the work of the last 10 years or so and to put that
into some context that will then allow others, perhaps, to make further
decisions and judgments. I think one of the reasons that we are not able
to do that there are several reasons some of whiah have already been men-
tioned, is that at least with respect to viruses, the ones that appear to
be the most important in terms of environmental transmission of disease,
are viruses such as hepatitis A, the florwalk type of viruses and possibly
rotaviruses that we did not even have the capability to work with 10
years ago. We couldn't even do serological work with them in the context
of environmental studies. We are still not able to cultivate some of
these viruses and can cultivate hepatitis A and rotaviruses only with
great difficulty. So, these are the viruses for which we need informa-
tion with respect to their transport, movement, in land application
systems and in other environmental areas. That's why I think we, in
part, made the research recommendations that additional studies need to
be done, many of which are along the same tines that we have been trying
to do over the last 10 years or so. The studies must be done with these
important viruses and we cannot necessarily presume that their behavior
is going to be the same in the environment as the other viruses that we
have been studying for the last 10 years. It has become quite clear that
the other virsues that we have studied the ones that we have been using
ae models, are apparently not the most important one in terms of disease
transmission from environmental sources.
William Davis, City of Long Beach: I'm certainly no expert on
virus, but I have a question. Is it not the general consensus of this
group that the lack of information is not sufficiently large that we
should oppose land application of municipal effluents and sludges but
rather that we should move ahead in spite of your fears and concerns?
Elmer Akin: I think that was njy original statement—that we do feel
with current knowledge there is no reason we cannot go ahead with land
application.
William Davie: That is a very important statement.
Elmer Akin: That was really the reason for our opening statement
because we do feel strongly that there's no reason not to go ahead with
land application, from a microbiological standpoint. There have to be
caveats of course, such as the application of good management practices
and the continuation of research to better quantitate and Identify the
risks. We don't know quite what the risks are. We feel that they are
perhaps minimal but they have not been quantltated and I think we need to
determine what they are.
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AKIN
William Davie: I think that'e the point that when you are a user of
this information and having to deal with it, those fundamentals aren't
getting out.
Suean Young, INCOG, Tulea, Oklahoma: I think we ought to have some
follow-up on this. Again, I'm a user for the information. I need com-
parative risk assessments to explain things in the matter of what is the
risk of exposure to viruses via land application of waste as compared to
a child's exposure to virus in the classroom. We need that kind of in-
formation. It is not necessarily a research need, but it is a need we
definitely have.
Elmer Akin: We could take a vote but I think most mlcroblologists-
epidemiologists feel pretty confident in stating that the risk 1s greater
in the classroom. We do feel that person-to-person transmission is a
major route of transmission in this country. Does that mean that we
aren't concerned about the other route? I don't think so. We talked
about this 1n our session and I'll be very brief. Let's say arbitrarily
that 90% of infectious disease transmission 1s from person-to-person, and
only 10% from environmental exposure. What then. Do we Ignore that 10%,
or do we try to minimize that further? I don't think the American people
are ready to accept that level of risk if it Is controllable. Certainly
they are not in regard to drinking water. They want their drinking water
to be "risk free" or as close to it as can be obtained within reasonable
economic constraints, I think that is the key word, "reasonable".
That's what we work out 1n sessions like this, and 1n state legislatures,
I suppose.
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Publia Health and Risk Aeaeeement: Organise and Inorganiea
Herbert Pahren, Moderator
Delbert Hemphill, Co-Moderator
James Ryan, Secretary
Mary Beth Klrkham, Co-Secretary
Participants: D. C. Adrlano, Dale E. Baker, Thomas B1ck, Garfield N.
Biddle, George Braude, Richard Bull, Rufus Chaney, Michael
Connor, R. B. Dean, Gregory Dlachenko, W. R. Dunlop, Gayle
E. Edmlsten, Michael Flynn, Ernest C. Foulkes, George
Fries, David Graveland, Philip Hopke, Robert Horvath,
Charles F. Jelinek, Roma P. Jenkins, Norman Kowal, Terry
J. Logan, John Meier, Raymond W. Miller, L. M. Naylor,
Michael Overcash, Magnus Plscator, Michael Plewa, Raymond
F. Shlpp, James E. Smith Jr., Richard T. Sprague, Robert
Swartz, M. A. Tabatabal, Wade Talbot, John M. Walker, M,
D. Webber
In 1973 there was little discussion on the Impact of human health or
organic and Inorganic contaminants in municipal wastewater and sludge
when applied to land. Shortly thereafter, the health Impact was recog-
nized and various applied research studies were carried out at an acce-
lerated pace.
The state of knowledge today 1s such that there no longer are
serious gaps 1n knowledge. Research still required may be considered
fine tuning the Information presently at hand.
Three position papers relating to this subject, I.e., An Ove-rvimi of
Publia Health Effects, Speoifio Organic Compounds, and Metale accurately
summarize what we know today. This Information 1s of great value to the
designer of land treatment systems and the regulator.
Key points developed in this workshop may be summarized as follows:
1. At annual application rates of less than 15 Mt/ha, of sludge of
median composition where a reasonable drainage and cyclic establishment
of sustained aerobic soil conditions occur* and groundwater remains
deeper than 0.3 to 0.7 Meters from the soil surface, leaching of metals
and organlcs should pose little threat to groundwater resources.
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PAHRfN AND HE MPHILI
However, adjustments may be necessary because of site specific con-
ditions. Concerns were the lack of detailed information on the com-
position of the sludge and the fate of these materials. Similar concerns
were expressed for effluents.
2. It was the consensus that wastewaters should not be chlorinated prior
to high rate application to land, since precursors to halogenated orga-
nlcs may be present.
3. The factors that affect the migration of organlcs through various
soils and decomposition 1n groundwater are research needs.
4. There appears to be no health effects associated with surface water
contamination 1f runoff Is controlled.
5. It was the consensus that additional epidemiological studies with
exposure of high risk groups to cadmium need not be Initiated until the
present studies have been completed.
6. It was the strong recommendation of the group that an International
panel should re-evaluate the 1972 recommendations of the WHO/FAO on
limits for cadmium Intake 1n view of the substantially better data base
today.
7. Except for cadmium and lead, metals are not expected to create a
human health problem 1n sludge-amended soils. The direct deposition of
lead on plants should be evaluated for passage through the food chain.
8. There was a concern by some over accurate information on present
dietary exposure to cadmium. However, 1t was brought out that FDA is
pursuing a better definition of dietary intake.
9. There was need for more research on how various nutritional factors,
including other metals, influence the absorption of cadmium.
10. There was concern over the use of sludge containing high levels of
lead on garden soil due to the potential pica problem. However, no spe-
cific research recommendation was made.
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Report. Organios and Inorganics
Page 455
11. Research Is needed for the Impact of several elements in sludge on
grazing animals. The principal elements of concern were Co, Mo, F, and
Se.
12. It was agreed that additional studies on the Impacts of organlcs on
the food chain through the animal-human pathway were not necessary for
the near future.
13. More research 1s needed on the passage of organlcs through the plant-
human pathway, Including development of better methodology and bloassay
systems. Concern is not limited to priority pollutants.
14. Research 1s needed on the use of treated wastewaters and sludges for
aquaculture purposes. Levels of organlcs and inorganics in ponds and the
uptake by fishes are initial concerns.
15. There was general agreement among workshop participants and a recom-
mendation that the U.S. EPA re-evaluate Its September 13, 1979 regula-
tions on the limits for cadmium contained 1n solid waste applied to land.
The data base today is substantially better than that used at the time
the regulations were promulgated.
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PAHREN AND HEMPHILL
QUESTIONS AND COMMENTS FROM THE FLOOR:
William Davis, City of Long Beach: There seems to me to be a con-
sensus that much hae been learned from the research over the last 10
years and what I thought I heard said here wae that the information deve-
loped, at least by Herb, would justify a re-evaluation of existing regu-
lations that now exist which govern the land application of effluents and
sludges? Is that the general consensus I hear?
Herbert Pahren: We specifically referred to re-evaluation of the
WHO/FAO guidelines that was one of the many considerations 1n developing
regulations. In your comment you used the term regulations. The WHO/FAO
numbers are not regulations per se. Our view 1s that whenever guidelines
or regulations, are established for the public to follow, they should not
be set 1n concrete, but from time to time they should be re-evaluated.
William Davie: As I look at the September 1979 criteria, for
example, my recollection is that those were based in large measure on
much of the concepts that you alluded to from WHO. Isn't it reasonable
to conclude that if the basic concepts are now needing to be re-
evaluated, so should not the regulations?
Herbert Pahren: As a good principle, yes.
A. L. Page: It might be advisable that this question be directed to
each of the moderators. It might be helpful in terms of the proceedings
of this particular session.
William Davie: The comment seems to me to be grouped into two cate-
gories. One is what is the impact on the farmers - phytotoxicity? The
other is on the health side of it, particularly the point just made
related to the cadmium issue and the metals issue.
Herbert Pahren: I might point out Bill, that the Issue came up
during our deliberations and 1t was the feeling that the workshop members
did not want to be 1n a position to develop new regulations yesterday
afternoon and last night, but they did agree on the principle that as new
information 1s developed, 1t makes good sense to re-evaluate the guideli-
nes and criteria we have.
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William Davis: We knew that 10 years ago and, the other thing I
would agree wholeheartedly with, it is beyond the scope of this group to
define the new regulations but I think is well within the scope of this
group to comment on the current regulations and the need to look at those
existing regulations in the light of what has been learned in the past 10
years. That is something that is well within and should be, otherwise,
the question again comes up, why continue it?
A. L. Page: Comments from other moderators on this question?
I. E. Sommers, Purdue University: (Representing the sludge group):
I think it was the consensus of the sludge management group that the
sludge regulations need to be re-evaluated. However, this is still a
regional consideration because of soil differences and cropping patterns,
availability of different management practices, and so forth. But I
think the group basically felt that though there probably should be a
national standard that should be set but it should be based on regional
differences, and it does need to be re-evaluated.
Raymond Loehr, Cornell University,(representing the Engineering
group): It is always hard to speak for a group, but from the discussion
yesterday, I believe that our group would endorse that last comment. It
is a natural extension of one of the recommendations I discussed earlier,
the re-assessment of the heavy metal loading criteria.
Herbert Pahren: As one member of the panel pointed out, It Is a
matter of how much of a factor of safety one should select in setting
these criteria. Some people want to cut 1t quite thin and others want to
be very conservative and use a very high safety factor. It's a matter of
where the line is drawn.
A. L. Page: Parker, would you care to comment on the diaoussion
which transpired in the workshop which you moderated?
Parker F. Pratt, University of California, Riverside, (representing
the Effluent group): The workshop I moderated did not discuss this
question directly, but I am sure if we polled them, they would agree that
any time there is new information related to guidelines or standards,
whether they be regional, state, or federal we should have a re-
evaluation.
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Page 458
PAHREN AND HEMPHILL
(Question by A. L. Page restated for Elmer Akin, [representing the
Pathogens group] temporarily out of the room): In light of the data that
we have developed over the past 10 years is there a need at this par-
ticular time to re-assess or re-evaluate the criteria which govern the
land application of municipal effluents and sludges. Correct me if I am
wrong, Bill.
William Davis: I used the term regulations not criteria.
Elmer Akin: I am aware of only one regulation and that pertains to
the land application of sludge only. It is premature to re-evaluate it
now because the results of some major studies are pending. If, however,
new informatin indicates that regulations can safely be relaxed, then I
think the change should be made. I am quite confident the pathogen
workshop participants would agree although this specific question was not
put to them.
A. L. Page: Dick Thomas, were you going to make a comment?
Richard Thomas, EPA, Washington: From the standpoint of the land
treatment of effluents, the only fixed regulation pertains to the protec-
tion of groundwater.
Robert Dean, Environmental Science and Technology, Copenhagen,
Denmark: As a member of this group on metals, I think that we should put
into the final document something out of the position papers by Logan and
Chaney, and the base paper published by Ryan et_ at., that some of our
original assumptions on cadmium were probably conservative, by a factor
which has been variously estimated of between 3 and 10. I do think we
should hear back again from people who presented or who worked on these
position papers, and I think it should go into the document. I do feel
personally, that we were overly cautious on cadmium and that the cadmium
limits turned out to be right at the cutting edge which decided whether
or not land application was going to be economical. We perhaps have
thrown out possible applications that would have been the best way to go
if we had a little more information, flow we've got the information, and
I'd like to see it used.
Charles Jelinek, FDA, Washington, D.C.: I am going to comment an
what Bob Dean just said, but that wasn't why I came up here originally.
I think we ought to recommend reassessment by an international body of
acceptable daily dietary intake of cadmium in light of additional infor-
mation that has been developed on toxicity of cadmium. I would agree
with that. I definitely don't agree that there is enough information in
to show that we've been too conservative. Indeed, there are gape in
knowledge in toxicity, and it might even be that when this international
body reassesses it they might even come up with a lower acceptable
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Report: Organics and Inorganics
Page 459
dietary intake. I don't think we can pre-Judge them at all. Now, in
light of conservatism, I am speaking now as a member of the Bureau of
Foods, of the Food and Drug Administration, we're always going to be con-
servative when it comes to deciding what level of a given toxicant we can
tolerate in our food supply. We would be remiss in our duties if we were
not conservative. We would also be remiss if we are too conservative.
So it gets around to a question of what safety factor do you allow. And
I would point out to people here that in the case of cadmium in general,
we can be more liberal -in the safety factor that we allow than we do in
the case of food additives. The reason being, that cadmium is a natural-
ly occurring toxicant; it is harder to control and therefore, we have
gone with lower safety factors than we would in judging food additives.
Finally, I'd like to point out that I don't think we want to disregard
safety factors too much. All we have to do is think of what happened in
the Hyatt Hotel in Kansas City.
A. I. Page: In the way of attempting to rap up this particular
issue, I sense that there is a general agreement amongst the moderators
and among the group as a whole, that the time is right to re-evaluate and
I believe that this can go as a recommendation from this particular
workshop.
William Davis: Comments were made about existing regulations, rela-
tive to cadmium, were overly conservative, Was there a consensus about
the conservatism?
A. L. Page: I don't believe it would be productive in this large a
group to tend to either defend the current regulations ae they pertain to
cadmium or to suggest what they should be, if those in effect are not
adequate.
William Davis: That was not the question. The question was, is it
the consensus of the group regarding the degrees of freedom, the conser-
vatism that is in those regulations, is it open for re-evaluation - ie it
too much, too little?
A. t. Page: I think the group agrees that this ie open to evaluation
but I don't think we should be presumptive relative to what the outcome
will be.
Thomas Gleason, EPA, Washington, DC: I would just like to say there
is an interagency group that is working on the consideration of re-eval-
uation of the regulationst and that the proceedings of this conference
will play an important role in that accomplishment. As to whether thei*8
ie an over-conservative viewpoint from a toxicological viewpoint, going
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Page 460
PAHREN AND HEMPHILL
from a safety factor of 4 down to 1, how low can you go? I think we can
adequately justify the safety factor.
Richard Bullt EPA, Cincinnati: I want to reinforce what Herb just
said, in the sense that I think that in the data that's been presented to
us in the past few days, there is no real indication that there is a
problem with health risks associated with organise and associated with
sludge application. But one thing I wanted to point out, and it get's
back to some of the comments on cadmium, is that most of the conclusions
that were arrived at were not arrived at by considerations of the health
effects of the individual compounds. They were really going from that
data which was available primarily from that offered by Mike Overcaeh in
terms of how much of that material is likely to get into a situation
where man was going to be exposed. We really did not deal in any case
with the intrinsic health effects of the individual compounds. And that
is the reason, even in the case of cadmium for which we did discuss the
recommendation of WHO, I don't think this was the proper body to come to
gripe with that particular issue at all. Insofar as whether it's more
conservative or less conservative, I just didn't see the cadmium experts.
It was not something that could have been voted on in this particular
situation.
Dale Baker, Pennsylvania State University: Under statement Hi,
there is a very serious omission, and that refers to 15 mt/ha of median
composition of sludges. The intent was that sludges of median com-
position has to be entered in there because IS mt/ha of any sludge would
not he safe. #11 you have some non-metals listed in there as metals,
like Se and F.
Herbert Pahren: OK, I'll make the adjustment.
Philip Hopke and Michael Plewa, University of Illinois: We feel
compelled to add some additional comments after listening to your report
on the workshop session in which we participated. It is our feeling that
the issues discussed regarding organic contaminants were not fully repre-
sented in the 8ummary report. Michael Overcaeh and others besides our-
selves have raised unanswered questions regarding persistence, transloca-
tion, metabolism, sequestering, and biological effects. For example, the
sludge-animal-human food chain results as described by the FDA looked at
a very small portion of the spectrum of compounds that may be present in
sludge. The examination of only PCB's and pesticides is hardly exhaus-
tive. We can make some estimates of the uptake of lipophilic compounds
into fat or milk through octanol/water partition coefficients but there
is much yet to be learned as the health effects of such accumulated
materials for many, many possible species.
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Report. Organics and Inorganics
Page 461
The development of much move information about the fate of organic
contaminants in eoile, theiv ability to be incorporated in the food chain
should be a high priority area of research during the next few years.
Although it has been shown by Kirk Brown that some waste materials can
decompose rather rapidly, other materials particularly polyhalogenated or
multiple-branch compounds may have quite long lifetimes. It should be
remembered that the dioxin contamination of Times Beach, MO, soils were
not considered to be a problem in 1975 since it was felt that dioxin
would rapidly decompose in the soil. Let us not make the same mistake
with other contaminants in sludges or effluents.
We believe strongly that the direct biological activity of the
sludge, particularly as expressed in whole plants such as our lea mays
wx-locus mutagenicity test, have potential ecological impacts that have
not been considered. In addition, such tests indicate the potential for
sludge-grown plants to act as a vector for introducing mutagens into the
human food chain. It has been shorn that plants can take up a compound,
(e.g., atraaine), and metabolize it into a stable, extractable mutagen.
Thus, plants can act to induce or enhance the biological effects of trace
contaminants. Ae we understand it, there are groups who are raising the
mutagenicity of sludge as an issue in land application. There is a
published report of increased mutagenic activity in the urine of male
Fischer rate fed beets grown in sludge-treated soils. The interpretation
of these results are difficult because we do not know if any of the
internal tissues of the -rats have shown any effects. It would seem to us
that in important research objective should then be evaluating the trans-
port and fate of mutagens in the sludge and from those results, iden-
tifying the level of risk potential to the general public. Our work on
the mutagenicity of various sludges indicates a substantial range of
biological activity is found in different municipal sludges. Ve believe
that it would be very simple to develop a good set of biological indica-
tor organisms that could be grown in a demonstration plot before large
scale operations with a given sludge are begun.
In summary, we believe that the potential for human health effects
from trace organic contaminants in sludge and effluents were substan-
tially underestimated in the report than was made to the closing workshop
sessions and we urge that more emphasis be given to organics ae research
needs. Ve believe that the organics may well come to play as an impor-
tant role in determining the suitability of sludges and effluents for
land treatment and that further research now will result in fewer
problems being discovered later.
-------
APPENDIX
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Planning Committees
Page 465
I. Organization and Planning Committees
Chairperson: Thomas L. Gleason, III, EPA-ORD, Washington, DC
Vice-Chairpersons: James E. Smith, Jr., EPA-CERI, Cincinnati, OH
A. L. Page, University of California, Riverside
Planning and Organization:
James E. Smith, Jr.
EPA-CERI, Cincinnati, OH
Robert Tonetti
EPA-OSW, Washington, DC
Michael Flynn
EPA-OSW, Washington, DC
Rufus Chaney
USDA-ARS, Beltsville, MD
George Braude
FDA-BF, Washington, DC
Charles Fogg
USDA-SCS, Washington, DC
Richard Phillips
SCS liasion to EPA, USDA, Washington, DC
Richard Gilbert
USDA-SCS, Washington, DC
Edward H. Bryan
NSF-WREE/CEE, Washington, DC
Robert Bastian
EPA-OWPO, Washington, DC
David Kleffman
EPA-OHR, Washington, DC
Sherwood Reed
USA/CRREL, Hanover, NH
James E. Parr
USDA-ARS, Beltsville, MD
Wylie Burge
USDA-ARS, Beltsville, MD
Clarence Lance
USDA-ARS, Beltsville, MD
Bruce Mintz
EPA-OWPO, Washington, DC
Charles Spooner
EPA-OW, Washington, DC
John M. Walker
EPA-OWPO, Washington, DC
Glenn J. Hawkins
OCE-U.S. Arn\y, Washington, DC
Wade Talbot
EPA-OHR, Washington, DC
Robert H. Kayser
EPA-0TS/0TI, Washington, DC
James 0. Evans
USDA-vFS, Washington, DC
Albert L. Page
U. of California, Riverside, CA
Bala Krlshnan
EPA-ORD, Washington, DC
Thomas L. Gleason, III
EPA-ORD, Washington, DC
David Zenz
Metro Sanitation Dist., Chicago, IL
Laural Kosaoka
EPA-OSW, Washington, DC
Lee E. Sommers
Purdue University, W. Lafayette, IN
Robert H. Miller
North Carolina State U., Raleigh, NC
Hunter Follett
Colorado State U., Ft. Collins, CO
Herbert Wiser
A0D-0EET/0RD, Washington, DC
Merna Herd
AAA-OW, Washington, DC
Michael Cook
OD-OSW, Washington, DC
Cecil Lue-K1ng
Metro Sanitation D1st., Chicago, IL
G. K. Dotson
EPA-MERL, Cincinnati, OH
Fredrick Swader
USDA-Extens1on Service, Washington, DC
I. K. Iskandar
USA/CRREL, Hanover, NH
W. Rosenkranz
EPA-ORD, Washington, DC
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Workshop Participants
Page 467
II. Workshop Participants
Workshop on Utilization of Municipal Wastewater and Sludge on Land
Dr. Donald D. Adrian
Department of Civil Engineering
Colorado State University
Fort Collins, CO 80521
Dr. D. C. Adriano
Savannah River Ecology Laboratory
P. 0. Drawer E
Aiken, SC 29801
Dr. Elmer Akin
U.S. EPA, HERL
25 St. Clair Street
Cincinnati, OH 45268
Mr. David Ariall
U.S. EPA - Region VI
345 Courtland Street NE
Atlanta, GA 30308
Dr. Takashi Asano
Office of Water Recycling
State Water Resources Control Board
P. 0. Box 100
Sacramento, CA 95801
Dr. Donald Aulenbach
Dept. Chem. 8 Environ. Engineering
Rensselaer Polytechnic Institute
Troy, NY 12181
Mr. Dwlght C. Baler
Baler Agronomy, Inc.
Route 2, Box 605
Woodland, CA 95695
Dr. Dale E. Baker
Department of Agronorny
119 Tyson Building
Pennsylvania State University
University Park, PA 16802
Dr. Robert Bastian
U.S. EPA
OWPO-WH547
401 "M" Street SW
Washington, DC 20460
Dr. Thomas E. Bates
Dept. of Land Resource Science
University of Guelph
Guelph, Ontario NIG 2W1
CANADA
Mr. Henry H. Benjes, Jr.
CWC
1777 South Harrison, Suite 310
Denver, CO 80210
Dr. Gerald Berg
U.S. EPA
453 Beachtree Drive
Cincinnati, OH 45224
Dr. Charles R. Berry
U. S. Forest Service
Forestry Science Laboratory
Carlton St
Athens, GA 30602
Mr. Thomas B1ck
National Wildlife Federation
1412 16th Street NW
Washington, DC 20036
Dr. Garfield N. Biddle
Acting Chief, Contaminants and
Natural Toxicants Evaluation Branch
FDA Bureau of Foods (HFF-159)
Washington, DC 20204
Dr. J. W. Blggar
Department of LAWR
University of California
Davis, CA 95616
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Page 468
Dr. D. R. Bouldin
Department of Agronomy
Cornell University
Ithaca, NY 14853
Mr. James Butler
ENERCO Environmental, Inc.
4410 Steele Street
Denver, CO 80216
Dr. George Braude
U.S. FDA
200 "C" Street SW
HFF-424
Washington, DC 20204
Dr. Francis Broadbent
Department of LAWR
University of California
Davis, CA 95616
Dr. A. Lloyd Brown
Department of LAWR
University of California
Davis, CA 95616
Dr. K. W. Brown
Dept. of Soil & Crop Sciences
Texas A&M University
College Station, TX 77843
Mr. Charles M. Cameron,Jr.
Temple, Rarker and Sloane Assoc.
33 Hayden Street
Lexington, MA 02173
Mr. Stephen Campbell
BI0-GR0 SYSTEMS,INC.
P. 0. Box 209
Annapolis, MD 21404
Dr. B. L. Carlile
Texas ASM University
P. 0. Box 2677
College Station, TX 77843
Dr. Rufus Chaney
USDA-ARS-NER
Room 101, Bldg. 008
BARC-WEST
Beltsville, MD 20705
Dr. Richard Bull
Director, Toxi. & Micro. Division
U.S. EPA-HERL
25 St. Clair Street
Cincinnati, OH 45268
Dr. Wylie Burge
USDA-SEA-ARS
Biological Waste Management X
Organic Resources Laboratory
Beltsville, MD 20705
Mr. Patrick L. Burke
Montgomery Engineers
2255 Ygnaclo Valley Road
Suite C
Walnut Creek, CA 94598
Dr. A. C. Chang
Dept. of Soil & Environmental Sciences
University of California
Riverside, CA 92521
Dr. Leon Chesnin
Department of Agrononiy
University of Nebraska
Lincoln, NE 68503
Dr. Lee A. Chrtstensen
Dept. of Agricultural Economics
Room 312 Conner Hall
University of Georgia
Athens, GA 30602
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Workshop Participants
Page 469
Dr. C. E. Clapp
USDA-ARS
University of Minnesota
St. Paul, MN 55108
Dr. Scott Clark
Institute of Environmental Health
Kettering Laboratory
3223 Eden Avenue
Cincinnati, OH 45267
Dr. Michael Connor
IPH
Harvard School of Public Health
665 Huntington Avenue
Boston, MA 02115
Or. Michael Contl
Office of Toxic Integration
U.S. EPA (TS-777)
401 "M" Street SW
Washington, DC 20460
Mr. David Cooper
Agronomy Department
University of Missouri
21 Mumford Hall
Columbia, M0 65211
Mr. Jack L. Cooper
National Food Processors Association
1133 20th Street NW
Washington, DC 20036
Dr. Robert C. Cooper
University of California
School of Public Health
GI01
Berkeley, CA 94720
Dr. Richard B. Corey
Department of Soil Sciences
University of Wisconsin
1525 Observatory Drive
Madison, WI 53706
Dr. Ronald Crltes
George S. Nolte and Associates
1700 "L" Street
Sacramento, CA 95814
Dr. D. J. D'Alessfo
Dept. of Preventive Medicine
University of Wisconsin
465 Henry Hall
Madison, WI 53706
Mr. William Davis
Manager, Solid Waste Program
Dept. of Public Works
333 W. Ocean Blvd.
Long Beach, CA 90802
Dr. R. B. Dean
Consultant
Environmental Science 8 Technology
Dronnlngensgade 9
1420 Copenhagen K DENMARK
Mr. Roger Dean
U.S. EPA-Region VIII
Water Division
1860 Lincoln Street
Denver, CO 80295
Mr. Donald Deemer
E.R.M. Inc.
999 West Chester P1ke
P. 0. Box 357
West Chester, PA 19380
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Page 470
Dr. Y. A. Demirijlan Mr. Dennis Draman
Manager, Wastewater Management Systems Environmental Waste Disposal, Inc.
County of Muskegon P. 0. Box 100
8301 White Road Stuart, IA 50250
Muskegon, MI 49442
Dr. Gregory Diachenko
U.S. FDA
200 "C" Street SW
HFF-424
Washington, DC 20204
Dr. Frank M. D1Itri
Institute of Water Research
Natural Resources Building
Michigan State University
East Lansing, MI 48824
Dr. Max Dodson
U.S. EPA-Region VIII
Water Division
1860 Lincoln Street
Denver, CO 80295
Dr. Harvey Doner
University of California
Berkeley, CA 94720
Dr. C. R. Dorn
Dept. Veterinary Preventive Medicine
Ohio State University
1900 Coffey Road
Columbus, OH 43085
Mrs. Grace A. Draman
Environmental Waste Disposal, Inc.
P. 0. Box 100
Stuart, IA 50250
Mr. W. R. Dunlop
BIO-GRO SYSTEMS,INC.
P. 0. Box 209
Annapolis, MD 21404
Ms. Gayle E. Edmlsten
MINTECH, Inc.
4236 S. 76th E. Avenue
Tulsa, OK 74145
Dr. H. A. Elliott
Department of Agricultural Engineering
University of Delaware
Newark, DE 19711
Dr. Eliot Epstein
E & A Environmental Consultants
1613 Central Street
P. 0. Box 372
Stoughton, MA 02072
Dr. A. Erlckson
Dept. of Crop & Soil Science
Michigan State University
East Lansing, MI 48824
Mr. G. K. Dotson
Wastewater Research Division
U.S. EPA-MERL
25 St. Clair Street Dr. James 0. Evans
Cincinnati, OH 45268 U.S.D.A,- Forest Service
P. 0. Box 2417, Room 808, RP-E
Washington, DC 20013
Dr. R. H. Dowdy
USDA-ARS
331 Soil Science Building
University of Minnesota
St. Paul, MN 55108
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Workshop Participants
Page 471
Dr. Norman Evans
Colorado Water Resource Institute
Room 203, Administration
Colorado State University
Fort Collins, CO 80523
Dr. Samuel R. Farrah
Dept. Microbiology 4 Cell Science
University of Florida
Gainesville, FL 32611
Dr. Joseph Farrell
MERL
U.S. EPA
26 West St. Clair Street
Cincinnati, OH 45268
Dr. Michael P. Flynn
U.S. EPA (WH-564)
401 "M" Street SW
Washington, DC 20460
Dr. Hunter Follett
Agrlcultrual Experiment Station
Colorado State University
Fort Collins, CO 80523
Dr. Ronald F. Follett
1824 Busch Court
Fort Collins, CO 80523
Ms, Jane Forste
BI0-6R0 SYSTEMS,INC.
P. 0. Box 209
Annapolis, MD 21404
Dr. Lynn Forster
Dept. of Agricultural Economics
and Rural Sociology
Ohio State University
2120 Fyffe Road
Columbus, OH 43210
Dr. Ernest C. Foulkes
Dept. of Environmental Health(#56)
Univ. of Cincinnati Medical Center
3223 Eden Avenue
Cincinnati, OH 45267
Dr. George Fries
U.S.D.A.
BARC
Beltsvllle, MD 20705
Dr. Paul Fitzgerald
Dept. of Pathoblology
University of Illinois
Urbana, IL 61801
Dr. Charles Gerba
Dept. of Nutrition & Food Science
University of Arizona
Tucson, AZ 85721
Dr. Anne E. G1bl1n
Woods Hole Oceanographlc Institution
Woods Hole, MA 02543
Dr. Paul Giordano
Soils & Fertilizer Research Branch
Tennessee Valley Authority
Muscle Shoals, AL 35660
Mr. Gary Girollmon
Colorado Dept. of Health
Water Quality Control Division
4210 E. 11th Avenue
Denver, CO 80220
Mr. Thomas L. Gleason, III
U.S. EPA RD-681
401 "M" Street SW
Washington, DC 20460
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Page 472
Ms. Donna J. Griffin
MINTECH, Inc.
4236 S. 76th E. Avenue
Tulsa, OK 74145
Dr. Herbert 0. Grover
Ecosystems Research Center
Cornell University
Corson Hall
Ithaca, NY 148534
Dr. David Graveland
Alberta Environment
Cousins Building, S.S.I
Lethbridge, Alberta, CANADA
T1J 4B3
Dr. Charles Hagedorn
Department of Agronomy
Mississippi State University
Mississippi State, MS 39762
Mr. Craig G. Hebberd
Sellards * Grlgg, Inc.
143 Union Blvd., Suite 280
Lakewood, CO 80228
Mr. Phil Hegeman
Colorado Department of Health
Water Quality Control Division
4210 East 11th Avenue
Denver, CO 80220
Thomas J. Helnemann
CH2M Hill
5995 S. Syracuse
Denver, CO
Dr. P. A. Helmke
Department of Soil Science
University of Wisconsin
1525 Observatory Drive
Madison, WI 53706
Dr. Delbert D. Hemphill
Envlronmental Trace Substances
Research Center
University of Missouri
Columbia, M0 65211
Mr. Charles Henry
College of Forest Research, AR-10
University of Washington
Seattle. WA 98195
Dr. Thomas D. Hinesly
Dept. of Agronomy
University of Illinois
Urbana, IL 61801
Mr. Tom Holm-Hansen
Sandia National Laboratory
Organization 9453
P. 0. Box 5800
Albequerque, NM 87185
Dr. Philip Hopke
Env1ronmental Research Annex
University of IIlinols
1005 W. Western
Urbana, IL 61801
Mr. Robert Horvath
Los Angeles County
Sant1tat1on Districts
P. 0. Box 4998
Whittier, CA 90607
Dr. Frank Humenlk
Dept. of Agricultural Engineering
North Carolina State University
Raleigh, NC 27650
Mr. Henry Hyde
Waste & Water International
5850 Shell mound Street
Suite 100
Emeryville, CA 94608
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Workshop Participants
Page 473
Dr. I. K. Iskandar
Earth Sciences Branch
USA/CRREL
Hanover, NH 03755
Dr. Y. KaneMro
Dept. of Agronomy & Soil Science
University of Hawaii
Honolulu, HI 96822
Dr. George Jackson
U.S. FDA HFF-234
Div. of Microbiology Administration
200 "C" Street SW
Washington, D.C., 20204
Dr. Robert F. Keefer
Div. of Plant and Soil Sciences
West Virginia State University
Morgantown, WV 26506
Dr. L. W. Jacobs
Dept. of Crop & Soil Sciences
Michigan State University
East Lansing, MI 48824
Ms. Barbara Ann Kerdolff
U.S. EPA
26 W. St. Clair Street
Cincinnati, OH 45268
Dr. Wesley Jarrell
Dept. of Soil 4 Environmental
University of California
Riverside, CA 92521
Dr. L. D. King
Department of Soil Science
Sciences North Carolina State University
Raleigh, NC 27650
Mr. Lyle Jarrett N
BI0-GR0 SYSTEMS,INC.
P. 0. Box 209
Annapolis, MD 21404
Dr. Charles F. Jellnek
U.S. FDA
200 "C" Street SW
Washington, DC 20204
Mr. Roma P. Jenkins
1829 Ella Street
Jefferson City, MO 65101
Dr. Mary Beth Klrkham
Evapotransplration Lab
Kansas State University
Manhattan, KS 66506
Dr. B. D. Knezek
Dept. of Crop A Soil Sclei
Michigan State University
East Lansing, MI 48824
Mr. Paul Koenlg
Agronomy Department
University of Missouri
21 Mumford Hall
Columbia, MO 65211
Mr. Richard Johnson
Wright Water Engineers
P. 0. Box 219
Glenwood Springs, CO 81602
Dr. Norman Kowal
U.S. EPA
HERL
25 St. Clair Street
Cincinnati, OH 45268
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Page 474
Dr. Shiou Kuo
Washington State University
Western Washington Res. Ext. Center
Puyallup, WA 98371
Mr. Lowell E. Leach
Robert S. Kerr Environ. Research Lab
U.S. EPA
P. 0. Box 1198
Ada, OK 74820
Dr. C. R. Lee
USAE-WES
P. 0. Box 631
Vlcksburg, MS 39180
Dr. D. R. Linden
USDA-ARS
331 Soil Science Building
University of Minnesota
St. Paul, MN 55108
Dr. M. Dale Little
School of Public Health
Tulane Un1ver1sty
1430 Tulane Avenue
New Orleans, LA 70112
Dr. Raymond Loehr
Dept. of Agricultural Engineering
Cornell University
Ithaca, NY 14853
Dr. Terry J. Logan
Department of Agronomy
Ohio State University
Columbus, OH 43210
Dr. Harvey Luce
Dept. of Plant Science
University of Connecticut
Storrs, CT 06268
Dr. Cecil Lue-Hing
Research & Development
Metro. Sanitary Dist. Greater Chicago
100 East Erie Street
Chicago, IL 60611
Dr. Ebba Lund
Royal Veterinary & Agricultural Univ.
Bulous Vej 13
Copenhagen DENMARK
Dr. L. J. Lund
Dept. of Soil & Environmental Science
University of California
Riverside, CA 92521
Mr. Peter S. Machno
Sludge Program Manager
METRO
821 Second Avenue
Seattle, WA 98119
Mr. Robert Manson
Ohio EPA
1035 Devlac Grove Drive
Bowling Green, OH 43402
Mr. Sam Maphls
Briscoe Maphls, Inc.
5378 Sterling Drive
Boulder, CO 80301
Dr. C. James Martel
Earth Sciences Branch
USA/CRREL
Hanover, NH 03755
Dr. Gordon A. McFeters
Department of Microbiology
Montana State University
Bozeman, MT 59717
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Workshop Participants
Page 475
Dr. John Meier
U.S. EPA
HERL
25 St. Clair Street
Cincinnati, OH 45268
Dr. Milton W. Meyer
U.S. Soil Conservation Service
P. 0. Box 2890
Washington, DC 20013
Dr. Robert H. Miller
Department of Soil Science
North Carolina State University
Raleigh, NC 27650
Dr. Raymond J. Miller
Dean, College of Agriculture
University of Idaho
Moscow, ID 83843
Dr. Raymond W. Miller
Dept. of Soil Science & Blometeorology
Utah State University
Logan, UT 84322
Dr. Barbara Moore
University of Texas
Environmental Health Engineering
Cockrell Hall 8.7
Austin, TX 78712
Dr. Merry L. Morris
New Jersey DEP
Groundwater Discharge Permits
CN029, 1474 Prospect Street
Trenton, NJ 08536
Dr. L. M. Naylor
Dept. of Engineering
Cornell University
Ithaca, NY 14653
Ms. Lois New
New York DEC
Division of Solid Waste
50 Wolf Road
Albany, NY 12233
Dr. Dale Nichols
North Central Forest Exper. Station
Forestry Sciences Laboratory
1831 Highway 169E
Grand Rapids, MN 55744
Dr. Robert Northrop
University of Illinois at Chicago
P. 0. Box 6998
Chicago, IL 606R0
Dr. Wade Nutter
School of Forest Resources
University of Georgia
Athens, GA 30602
Dr. R. T. O'Brien
Department of Biology
New Mexico State University
Las Cruces, NM 88003
Dr. George A. O'Connor
Dept. of Crop & Soil Science
New Mexico State University
Las Cruces, NM 88003
Dr. Betty H. Olson
Program in Social Ecology
424C Computer Science Building
University of California
Irvine, CA 92717
Mr. Daniel O'Neill
Division of Water Quality
Michigan Dept. of Natural Resources
P. 0. Box 30028
Lansing, MI 48909
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Page 476
Dr. Michael Overcash
Dept. of Engineering
North Carolina State University
Raleigh, NC 27650
Dr. A. L. Page
Dept. of Soil 4 Environmental Sciences
University of California
Riverside, CA 92521
Dr. Herbert Pahren
U.S. EPA
MERL
Cincinnati, OH 45268
Dr. Antonio Palazzo
Earth Sciences Branch
USA/CRREL
Hanover, NH 03755
Dr. James Parr
USDA-ARS
Building 007
Room 124 BARC-WEST
Beltsville, MD 20705
Mr. James Patterson
National Park Service
1000 Ohio Drive
Washington, DC 20242
Mr. James Perry
S <5 L Fertilizer Inc.
8636 Yawberg
Whitehouse, OH 43571
Dr. Magnus Plscator
Center for Environmental Epidemiology
Graduate School of Public Health
University of Pittsburgh
Pittsburgh, PA 15261
Dr. Michael Plewa
Environmental Research Annex
University of Illinois
1005 W. Western
Urbana, IL 61801
Mr. Robert C. Polta
Metropolitan Waste Control Commission
350 Metro Square Building
St. Paul, MN 55101
Dr. Charles Pound
Metcalf & Eddy, Inc.
1011 E. Touhy, Suite 300
DesPlaines, IL 60018
Mr. W1111am F. Pounds
Bureau of Solid Waste Management
Division of Operations
P. 0. Box 2063
Harrisburg, PA 17120
Dr. Parker F. Pratt
Cha1rman
Dept. of Soil & Environmental Sciences
University of California
Riverside, CA 92521
Dr. Sherwood Reed
U.S. Army
CRREL
72 Lyme Road
Hanover, NH 03755
Ms. Merllyn Reeves
League of Women Voters Education Fund
Natural Resources Dept.
16506 Forest Mill Court
Laurel, MD 20707
Dr. William Rosenkranz
U.S. EPA-RD
401 "M" Street SW
Washington, DC 20460
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Workshop Participants
Page 477
Dr. James Ryan
Ultimate Disposal Section
U.S. EPA
MERL
Cincinnati, OH 45268
Dr. B. R. Sabey
Department of Agronomy
Colorado State University
Fort Collins, CO 80523
Dr. Bernard Sagik
Drexel University
32nd and Chestnut Streets
Philadelphia, PA 19104
Dr. Warren Sahs
Department of Agronomy
University of Nebraska
Lincoln, NE 68503
Mr. Curtis Schmidt
SCS Engineers
4014 Long Beach Blvd.
Long Beach, CA 90807
Dr. Eileen M. Seaker
Land & Water Research Institute
Pennsylvania State University
University Park, PA 16802
Dr. Raymond F. Shlpp
Department of Agronomy
Room 106 Agricultural Admin. Bldg,
Pennsylvania State University
University Park, PA 16802
Dr. Charles M. Smith
USDA-CSRS
14th and Independence Ave., SW
Room 6424 South
Washington, DC 20250
Mr. Douglas W. Smith
Temple, Barker and Sloane Assoc.
33 Hayden Avenue
Lexington, MA 02173
Dr. E. D. Smith
R.R. 3
NO. 124
Champaign, IL 61820
Dr. James E. Smith Jr.
U.S. EPA-CERI
25 St. Clair Street
Cincinnati, OH 45268
Dr. J. L. Smith
Dept. of Agricultural Engineering
University of Wyoming
University Station, P. 0. 8ox 3354
Larramie, WY 62071
Mr. Robert C. Smith
City of Columbus
Division of Sewers and Drains
90 W. Broad Street
Columbus, OH 43215
Dr. Robert G. Smith
Dept. of C1v1l Engineering
University of California
Davis, CA 95616
Mr. Stephen B. Smith
Black and Veatch
12075 East 45th Avenue
Denver, CO 80239
Dr. Stanley M. Smith
U.S. EPA-Reg1on VIII
Water Division
1860 Lincoln Street
Denver, CO 80295
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Page 478
Dr. Mark Sobsey
Dept. of Env1ron.Sciences S Engineer.
University of North Carolina
Chapel Hill, NC 27514
Dr. L. E. Sommers
Department of Agronomy
Purdue University
Life Sciences Building
West Lafayette, IN 47907
Dr. William E. Sopper
Land & Water Research Institute
Pennsylvania State University
University Park, PA 16802
Dr. Charles Sorber
ECJ 10.316
University of Texas, Austin
Austin, TX 78712
Dr. Douglas Southgate
Dept. of Agrl. Economics A Rural Soc.
The Ohio State University
2120 Fyffe Road
Columbus, OH 43210
Dr. Charles Spooner
U.S. EPA
OW WH-556
401 "M" Street SW
Washington, DC 20460
Mr. Richard T. Sprague
985 Ithaca Drive
Boulder, CO 80303
Dr. Gerald Stern
U.S. EPA
25 St. Clair Street
Cincinnati, OH 45268
Or. 0. J. Street
Department of Soil Science
University of Florida
Gainesville, FL 32611
Mr. Robert Swartz
METRO
821 Second Avenue
Seattle, WA 98119
Dr. M. A. Tabatabal
Department of Agronorny
Iowa State University
Ames, IA 50011
Dr, Wade Talbot
U.S. EPA
RD 6-683
401 "M" Street SW
Washington, DC 20460
Dr. George Tchobanoglous
Dept. of C1v1l Engineering
University of California
Walker Hall
Davis, CA 95616
Mr. Richard Thomas
U.S. EPA
0WP0 WH-547
401 "M" Street SW
Washington, DC 20460
Dr. Dean H. Ur1e
USDA-Forest Service
North Central Forest Exper. Station
1407 S. Harrison Road
East Lansing, MI 48823
Dr. Gary G. Van Riper
AMAX Inc.
1707 Cole Boulevard
Golden, CO 80401
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Workshop Participants
Page 479
Dr. J. Vlamls
Dept. of Soil & Plant Biology
University of California
Berkeley, CA 94720
Dr. Dale H. Vanderholm
Agricultural Experiment Station
University of Illinois
1301 West Gregory Drive
Urbana, 1L 61801
Dr. V. V. Volk
Department of Soil Science
Oregon State University
CorvalUs, OR 97331
Mr. Gerard Voss
Dept. of Agronomy
Colorado State University
Fort Collins, CO 80523
Dr. John M. Walker
U.S. EPA
OWPO-WH-547
401 "M" Street NW
Washington, DC 20460
Dr. Albert T. Wallace
University of Idaho
Moscow, ID 83843
Dr. Richard Ward
Christ Hospital
Institute of Medical Research
2141 Auburn Avenue
Cincinnati, OH 45219
Dr. M. D. Webber
Environment Canada
Burlington, Ontario
CANADA L7R 4A6
Mr. Joel Webster
U.S. EPA-Reg1on VIII, Water Division
1860 Lincoln Street
Denver, CO 80295
Dr. Flora Mae Weillngs
Epidemiology Research Center
State of Florida
400 West Buffalo Avenue
Tampa, FL 33614
Dr. Richard White
Cooperative Extension Service
The Ohio State University
Columbus, OH 43210
Mr. Willis Whitfield
Sandla National Laboratory
Organization 9453
P. 0. Box 5800
Albequerque, NM 87185
Dr. D. E. Williams
Dept. of Plant & Soil Biology
University of California
Berkeley, CA 94720
Mr. Jack L. Wltherow
Robert S. Kerr Environ. Research Lab
U.S. EPA
P. 0. Box 1198
Ada, OK 74820
Mr. William Yanko
Los Angeles County Sant1tat1on Dlst.
P. 0. Box 4998
Whittler, CA 90607
Dr. Ralph Young
Dept. of Plant, Soil, S Water Science
University of Nevada
Reno, NV 89557
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Page 480
Ms. Susan Young
INCOG
707 S. Houston
Tulsa, OK 74127
Dr. David R. Zenz
Coordinator of Research
Metro. Sanitary D1st. Greater Chicago
5915 West Pershing Road
Chicago, IL 60650
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