United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/9-79-023a
August 1979 >/ ,
t.i
vvEPA
Research and Development
Municipal Solid
Waste: Land
Disposal
Proceedings of the
Fifth Annual
Research Symposium
Do not remove. This document
ihould be retained in the EPA
Region 5 Library Collection.
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are.
1. Environmental Health Effects Research
2 Environmental Protection Technology
3 Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8 "Special" Reports
9 Miscellaneous Reports
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/9-79-023a
August 1979
MUNICIPAL SOLID WASTE: LAND DISPOSAL
Proceedings of the Fifth Annual Research Symposium
at Orlando, Florida, March 26, 27, and 28, 1979
Cosponsored by the University of Central Florida
and the Solid and Hazardous Waste Research Division
U.S. Environmental Protection Agency
Edited by:
Martin P. Wanielista
and
James S. Taylor
Department of Civil Engineering and Environmental Sciences
University of Central Florida
Orlando, Florida 32816
Grant No. 806198
Project Officers
Robert E. Landreth
Norbert B. Schomaker
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
These Proceedings have been reviewed by the
U.S. Environmental Protection Agency and ap-
proved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the U.S. Environmen-
tal Protection Agency, nor does mention of
trade names or commercial products constitute
endorsement or recommendation for use.
n
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FOREWORD
The Environmental Protection Agency was created because of increasing public
and governmental concern about the dangers of pollution to the health and welfare
of the American people. Noxious air, foul water, and spoiled land are tragic
testimony to the deterioration of our natural environment. The complexity of the
environment and the interplay between its components require a concentrated and
integrated attack on the problem.
Research and development is the first necessary step in problem solution;
it involves defining the problem, measuring its impact, and searching for solu-
tions. The Municipal Environmental Research Laboratory develops new and improved
technology and systems to prevent, treat, and manage wastewater and the solid
and hazardous waste pollutant discharges from municipal and community sources;
to preserve and treat public drinking water supplies; and to minimize the adverse
economic, social, health and aesthetic effects of pollution. This publication
is one of the products of that research -- a vital communications link between
the researcher and the user community.
The Proceedings present research aimed at minimizing the impact of land
disposal of solid and hazardous wastes. Solutions to specific problems are sug-
gested.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
m
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PREFACE
These Proceedings are intended to disseminate up-to-date information on
extramural research projects dealing with the disposal of solid and hazardous
wastes. These projects are funded by the Solid and Hazardous Waste Research
Division (SHWRD) of the U.S. Environmental Protection Agency, Municipal Environ-
mental Research Laboratory in Cincinnati, Ohio. Selected papers from work of
other organizations were included in the symposium to identify closely-related
work not included in the SHWRD program.
The papers in these Proceedings are arranged as they were presented at
the symposium. There were two concurrent programs, one primarily for land
disposal and the other primarily for resource recovery. Each program had
multiple sessions. There was an introductory session. Each of the five ses-
sions includes papers dealing with major areas of interest for those involved
in solid and hazardous waste management and research. Each program, land dis-
posal and resource recovery,is printed in a separate volume.
The papers are printed here basically as received from the symposium au-
thors. They do not necessarily reflect the policies and opinions of the U.S.
Environmental Protection Agency or the University of Central Florida. Hope-
fully, these Proceedings will prove useful and beneficial to the scientific
and engineering community as a current reference on land disposal and resource
recovery.
IV
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ABSTRACT
The fifth SHWRD research symposium on land disposal and resource recovery of munici-
pal solid waste was held at Orlando, Florida on March 26, 27, and 28, 1979. The purposes
of the symposium were (1) to provide a forum for a state-of-the-art review and discussion
of ongoing and recently completed research projects dealing with the management of solid
wastes; (2) to bring together prople concerned with municipal solid waste management who
can benefit from an exchange of ideas and information; and (3) to provide an arena for
the peer review of SHWRD's overall research approach. These proceedings are a compilation
of the papers presented by the symposium speakers. They are arranged in order of presenta-
tion. Volume I, Land Disposal, covered four primary technical areas: Pollutant Identifi-
cation; Environmental Assessment; Control Technology; and Pollutant Transport. Volume II,
Resource Recovery, covered five primary technical areas: Evaluation of Equipment, Unit
Operations, and Processes; Economics and Impediments; Systems Analysis and Special Studies;
Utilization of Recovered Materials; and Environmental Impacts of Resource Recovery.
This report was submitted in fulfillment of Research Grant No. 806198 by the University
of Central Florida under the sponsorship of the U.S. Environmental Protection Agency. This
report covers the period from October 1978 to July 1979, and work was completed as of July
1979.
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CONTENTS
Page
Disclaimer ^
Foreword ^1'
Preface iv
Abstract v
Contents vii
SESSION I: POLLUTANT INDENTIFICATION
Effect of Moisture Regines and Temperature on MSW Stabilization
Edward S. K. Chi an, Georgia Institute of Technology
Foppe B. DeWalle, University of Washington 32
Leachate and Gas Production Under Controlled Moisture Conditions
James J. Walsh, SCS Engineers
Riley N. Kinman, University of Cincinnati 41
Gas Production in Sanitary Landfill Simulators
T. E. Myers, J. C. Duke, Jr., P. G. Malone, D. W. Thompson,
U. S. Army Engineer Waterways Experiment Station 58
Leachate Production From Landfilled Municipal Waste - Boone County Field Site
Richard J. Wigh, Regional Services Corporation
Dirk R. Brunner, USEPA 74
Influence of MSW Processing on Gas and Leachate Production
Robert L. Hentrich, Jr., Joseph T. Swartzbaugh, James A. Thomas,
Systems Technology Corporation 98
Pathogen Content of Landfill Leachate
P. V. Scarpino and J. A. Donnelly
Department of Civil and Environmental Engineering
University of Cincinnati
D. Brunner, U. S. Environmental Protection Agency , 138
Vll
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Gas and Leachate: Summary
Vijay P. Patel, Robert L. Hoye, Richard 0. Toftner,
PEDCo Environmental, Inc 168
SESSION II: ENVIRONMENTAL ASSESSMENT
Analytical Methods Evaluation for Applicability in Leachate Analysis
Foppe B. DeWalle, Theo Y. Zeisig, University of Washington
Edward S. K. Chian, Georgia Institute of Technology 176
Development of the Proposed Definition of Hazardous Waste
David Friedman, U. S. Environmental Protection Agency 186
Vegetation Growth in Landfill Environs
Edward F. Gilman, Franklin B. Flower, Ida A. Leone, John J. Arthur,
Cook College, Rutgers University 192
Effects of Particle Size on Landfilled Solid Waste: Cold Climate Studies
Dave Hechler, Thomas, Dean, & Hoskins, Inc 209
Assessment of Municipal Solid Waste Disposal in Saline/Marshland
Environments
Michael S. Klein and Kenneth A. MacGregor, Management of Resources
and the Environment 224
SESSION III: CONTROL TECHNOLOGY
Soil Cover for Controlling Leachate from Solid Waste
Richard J. Lutton, Geotechnical Laboratory
U. S. Army Engineer Waterways Experiment Station 234
Liner Materials Exposed to MSW Landfill Leachate
H. E. Haxo, Jr., Matrecon, Inc 241
Forecasting Production of Landfill Leachate
Dirk R. Brunner, U. S. Environmental Protection Agency ' 268
Pilot-Scale Investigations of Accelerated Landfill Stabilization with
Leachate Recycle
Frederick G. Pohland, David E. Shank, Ronald E. Benson, Herbert H. Timmerman,
School of Engineering, Georgia Institute of Technology 283
Leachate Treatment Schemes - Research Approach
Donald S. Mavinic, Ph.D., P. Eng. Associate Professor of Civil Engineering
University of British Columbia 296
Leachate Treatment Demonstration
Bernard J. Stoll, U. S. Environmental Protection Agency 313
Remedial Action Alternatives for Municipal Solid Waste Landfill Sites
William W. Beck, Jr., A.W. Martin Associates, Inc., 324
Remedial Action Activities for Army Creek Landfill
David C. Clark, P.E., New Castle County D. P. W 343
vm
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SESSION IV: POLLUTANT TRANSPORT
Predicting Movement of Selected Metals in Soils: Application to
Disposal Problems
W. H. Fuller, A. Amoozegar-Fard, G. E. Carter, The University of Arizona 358
Environmental Impact of Alternative Methods of Landfill ing on Surface
Water and Ground Water
Grover H. Emrich, William W. Beck, Jr., A. W. Martin Associates, Inc 375
Predicting Landfill Gas Movements in Soil and Evaluating Control Systems
Charles A. Moore, Department of Civil Engineering, Ohio State University 386
Gas Migration and Modeling
T. W. Constable, G. J. Farquhar, B. N. Clement, University of Waterloo 396
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PROGRAMS IN LAND DISPOSAL AND RESOURCE RECOVERY AND CONSERVATION
John H. Skinner
Director, Land Disposal Division
Office of Solid Waste
U.S. Environmental Protection Agency
Washington, D.C.
ABSTRACT
This paper describes EPA's programs in land disposal and resource
recovery and conservation. The programs are authorized by the Resource
Conservation and Recovery Act (RCRA) of 1976, which also authorizes the
hazardous waste programs carried out by the Agency. RCRA is implemented by
EPA's Office of Solid Waste. The land disposal and resource recovery
and conservation programs include:
1. development of regulations and guidelines,
2. technology demonstrations and evaluations,
3. studies and information development, and
4. technical and financial assistance.
The basic purpose and objectives of these activities are summarized and
expected accomplishments and milestones for the next year are presented.
INTRODUCTION
Programs of the U.S. Environ-
mental Protection Agency, Office of
Solid Waste (OSW) are carried
out under the authority of the
Resource Conservation and Recovery
Act of 1976 (RCRA). The basic
objectives of this Act are to pro-
mote the application of improved
solid waste management in order to
protect public health and the envi-
ronment and to conserve valuable
material and energy resources.
Based on the requirements and pri-
orities in the Act, OSW has devel-
oped programs in these areas:
1. hazardous waste management,
2. land disposal, and
3. resource recovery and
conservation.
Since the subjects of this Symposium
are land disposal and resource re-
covery, this paper will focus only
on those activities. First, speci-
fic projects on land disposal and
resource recovery will be discussed,
followed by a discussion of the
technical and financial assistance
available to help build State and
local government programs.
LAND DISPOSAL
Land disposal activities can be
grouped into two categories:
1. development of regulations
and guidelines, and
2. technology demonstrations
and technical information.
Regulations and Guidelines
The keystone to the disposal
provisions of RCRA are the Criteria
for Classification of Solid Waste
Disposal Facilities (the Disposal
Criteria) called for by Section 4004
of the Act. The Disposal Criteria
will establish national standards
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for solid waste disposal by dis-
tinguishing facilities that pose no
reasonable probability of adverse
effects on health or the environ-
ment. Facilities not complying with
these criteria are termed "open
dumps" and are prohibited by the
Act. The Disposal Criteria were
published in proposed form in the
Federal Register on February 6,
1978. Final promulgation is
expected in mid-1979.
Section 4005 of RCRA requires
EPA to publish an inventory of all
disposal facilities in the United
States that are open dumps, i.e.
facilities that do not comply with
the Disposal Criteria. Any facil-
ity found to be an open dump must be
closed or upgraded according to a
State-established compliance
schedule. Financial assistance will
be provided to State solid waste
programs to evaluate facilities for
purposes of the open dump inventory.
A site classification manual is
being developed which will provide a
practical interpretation of the
Disposal Criteria and will be useful
to the States in evaluating facili-
ties for purposes of the open dump
inventory. Also another manual
is being developed describing pro-
cedures and techniques for closing
or upgrading open dumps.
RCRA calls for publication of
the open-dump inventory one year
after final promulgation of the
Disposal Criteria. However, due to
the large number of facilities to
be evaluated and the complexity of
such evaluations, the inventory will
be published in annual installments.
An arrangement has been made with
the Bureau of Census to handle the
data processing and actual inventory
publication.
For the most part the Disposal
Criteria do not specify particular
technologies or operational
approaches but instead establish
performance levels as necessary to
protect public health and the
environment. This was done to allow
different technologies and oper-
ations to be used as the local
situation dictated and to provide
opportunity for new and innovative
approaches. However, RCRA does call
upon EPA to provide guidance on
technologies.
Section 1008 directs the Agency
to develop and publish suggested
guidelines that provide a technical
and economic description of various
solid waste management practices
(including operating practices).
One such guideline describing the
practice of landfilling is under
development at this time. This
guideline will discuss design and
operation of a landfill in order to
protect public health and the envi-
ronment and will recommend practices
for leachate control, gas migration
control and groundwater monitoring.
A working draft of the Landfill
Guideline was circulated last year
and a proposed version should be
published in the Federal Register
for public comment by March of 1979.
Other guidelines to be devel-
oped in the future will cover land-
farming of solid waste and surface
impoundment disposal. In addition,
preparatory work is underway to
develop guidelines on the manage-
ment of two special waste categor-
ies: coal-fired electric utility
wastes and mining wastes. In
cooperation with the Office of
Research and Development programs
are being initiated to evaluate
facilities that dispose of fly ash,
bottom ash, and scrubber sludge
from coal-fired utilities and
wastes from metals and phosphate
mining and beneficiation processes
and uranium mining. Thirty to
forty facilities will be evaluated
over a period of two years in order
to assess practices for managing
such wastes.
Finally a guideline is being
developed for the disposal and
utilization of wastewater treatment
plant sludge under the combined
authorities of RCRA and Section 405
of the Clean Water Act. This
guideline will discuss practices
for landfilling sewage sludge, use
of sludge as a soil conditioner on
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agricultural lands, thermal pro-
cessing of sludge for energy
recovery, and sludge composting
or heat drying to produce a bulk or
bagged product. These guidelines
will be proposed in mid-1979 with
final promulgation expected in 1980.
Section 405 of the Clean Water
Act requires compliance with such
guidelines by operators of public-
ly owned wastewater treatment works
and it is expected that these
guidelines will be administered
through the National Pollution
Discharge Elimination System permit
process.
Technology Demonstrations and
Technical Information
The Office of Solid Waste
has several projects underway to
demonstrate and evaluate improved
techniques for disposing of solid
waste on land.
In Tullytown, Pennsylvania,
leachate from an asphalt-lined
landfill is collected and treated
by a number of physical and bio-
logical methods. The leachate
treatment plant has been operating
for several years and a number of
EPA reports have described its
operation. The final project
report was received in early 1979
and should be publicly available
shortly. The treated leachate is
discharged to a nearby river in
conformance with standards estab-
lished by the State.
In 1979, full-scale operation
of another leachate treatment
facility in Enfield, Connecticut
is expected to begin. This facil-
ity, based upon research conducted
by the EPA, Office of Research and
Development and the University of
Illinois, uses an anaerobic filter
to treat leachate. One of the
features of this system is the low
volume of sludge produced. The
final report on this project is
expected in mid-1980.
A full-scale lined landfill
demonstration is underway in
Lycoming County, Pennsylvania.
After several years in development,
a landfill employing a PVC liner
to collect leachate began to re-
ceive wastes in early 1978. A
report will be available in 1979
covering among other things, pro-
cedures for installing a liner
sheet covering a large area. Two
other lined landfill demonstrations
in Northern Tier, Pennsylvania are
expected to start in 1979.
In Bangor, Maine the Office of
Solid Waste is participating with
the City in demonstrating a pro-
cess for composting sewage sludge.
This project is based upon the
aerated-pile process for composting
sludge developed by the U.S.
Department of Agriculture in Belts-
ville, Maryland. This demonstra-
tion represents the first on-line
application of this process in a
small community. It has proven
very successful and composted
sewage sludge has been sold and
used as a soil conditioner for
over a year. An interim report
was published in 1977 and a final
report is due in 1979.
In Mountain View, California a
very innovative project involving
the recovery of methane from a
landfill is underway. In a joint
effort involving the City, the
Pacific Gas and Electric Company
and EPA, methane gas is pumped from
a landfill, cleaned up, and injec-
ted into a nearby pipeline supply-
ing gas to residential users.
This project not only prevents the
safety problems that could result
from the migration of gas from the
landfill, but also recovers and
utilizes a valuable resource. The
facility has been operational for
nearly a year, interim reports are
available, and a final report is
expected in mid-1979.
The Office of Solid Waste also
prepares a number of technical re-
ports on various subjects pertain-
ing to land disposal. One such
report that was very well received
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was a procedures manual for moni-
toring leachate and groundwater
around disposal facilities. We also
have an ongoing effort to monitor
groundwater at a number of disposal
sites both to improve monitoring
techniques and gain a better
understanding of leachate and
groundwater interaction. Other
technical reports under development
include an assessment of methods to
prevent and control migration of
toxic or explosive gases at disposal
sites and an evaluation of pro-
cedures to prevent hazards to
aircraft from birds attracted to
disposal facilities.
The Office of Solid Waste
also participates in the review
and evaluation of the wide range
of research and development pro-
jects in the land disposal area
conducted by the Office of
Research and Development and
described in other papers at this
Symposium.
RESOURCE RECOVERY AND CONSERVATION
Resource recovery and conser-
vation activities will be grouped
into three categories for
discussion:
1. activities of the Resource
Conservation Committee
2. guidelines for Federal
agencies, and
3. demonstrations, evalua-
tions and studies.
Resource Conservation Committee
The Resource Conservation
Committee was established by
Section 8002 (j) of the Act. It is
a Cabinet-level committee chaired by
the Deputy Administrator of EPA and
supported by OSW staff. The
Committee is required to conduct "a
full and complete investigation and
study of all aspects of the econo-
mic, social, and environmental
consequences of resource conserva-
tion." To obtain public input for
these studies, the Committee held
several hearings on beverage con-
tainer deposits, solid waste dis-
posal charges, the effect of
existing Federal tax and transpor-
tation policies on the use of virgin
and secondary materials, recycling
and resource recovery subsidies,
deposits or bounties on durable
goods, local user fees, litter
taxes, severance taxes, and product
regulation.
The first resource conservation
issue taken up by the Committee was
beverage container deposits. In its
January 1978 report to the President
and Congress, the Committee pre-
sented a recommended design for
beverage container deposit legisla-
tion. The Committee did not recom-
mend that such legislation be
passed, however; a decision on this
issue was. postponed until further
analyses were completed.
In its July 1978 report to the
President and Congress, the Commit-
tee submitted preliminary analyses
of solid waste disposal charges.
Work is continuing on beverage con-
tainer deposits and solid waste
disposal charges and the results of
these and other analyses will be
presented in the Committee's final
report along with recommendations.
This report is scheduled for com-
pletion in March 1979.
Guidelines for Federal Agencies
On April 23, 1976, EPA issued
Guidelines for Source Separation
for Materials Recovery. These
guidelines require the recovery of
highgrade paper, newsprint, and
corrugated boxes from Federal
facilities. As a- result, 175,000
Federal employees in 135 Federal
facilities are participating in the
paper recycling programs. It is
expected that another 100,000
employees will be in the program
by October 1979. OSW has worked
with the General Services Admini-
stration in establishing contract
procedures for the sale of the
paper and in developing an educa-
tional program for training
Federal employees in procedures for
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recycling office paper. To date,
over 2,000 tons of paper have been
recycled under the guidelines with
a return to the Federal Treasury of
over $125,000. In addition, at
least 15 States and hundreds of
local governments have adopted the
guidelines.
On September 21, 1976, EPA
issued Guidelines for Beverage
Containers. These guidelines
require that a refundable 5-cent
deposit be placed on all containers
for beer and soft drinks sold at
Federal facilities. The deposit is
intended to encourage the return of
containers for either refilling or
recycling. The Department of
Defense concluded a test of the
guidelines at 10 military bases in
June 1978 and will submit its plans
based on this test in early 1979.
The General Services Administration
also conducted a test of the guide-
lines in 8 of its 10 regions. To
date, 13 Federal agencies are
implementing the guidelines. The
OSW monitors agency compliance with
the guidelines and provides assist-
ance upon request.
On September 21, 1978, EPA
issued Resource Recovery Facilities
Guidelines. These guidelines
contain requirements and recommended
procedures for Federal agencies re-
garding establishment and use of
resource recovery facilities. To
date, some degree of implementation
has been reported by Federal agen-
cies in nine metropolitan areas.
Procurement Guidelines are
currently being developed under
Section 6002 of RCRA. All agencies
procuring with Federal funds
(including State and local govern-
ments, grantees, and contractors as
well as Federal agencies) must
"procure items composed of the
highest percentage of recovered
materials practicable." The guide-
lines for recommended procurement
practices will contain information
regarding suppliers, demand, price,
delivery time, performance, and
certification techniques.
OSW is now gathering data on
products purchased by the govern-
ment that may have high potential
in the use of waste materials.
Studies include:
1) The use of fly ash and
blast furnace slag in cement and
concrete. 2) The use of wastepaper
in insulation and board; waste
rubber in asphalt pavements; and
waste glass in bricks, asphalt, and
concrete. 3) The use of wastepaper
and other secondary fibrous mate-
rials in paper products and 4) The
use of composted sewage sludge used
as a soil conditioner and low-grade
fertilizer.
The first guideline, scheduled
to be proposed in April 1979, will
be on the use of fly ash and blast
furnace slag in cement and concrete.
Demonstrations, Evaluations and
Studies
The OSW is involved in the
demonstration and evaluation of the
technical, economic and environ-
mental performance of a number of
resource recovery systems.
Two of the early demonstration
projects developed technologies
that are being replicated in a
number of communities. The first,
in Franklin, Ohio, determined the
feasibility of using the wet-
pulping method of separating mixed
municipal solid waste into organic
and inorganic fractions. Follow-on
applications of this technology
will use the organic fraction of
the solid waste as a fuel.
The second demonstration, in
St. Louis, Missouri, developed the
technology of recovering a portion
of the organic fraction of the
mixed municipal waste stream for
use as a supplement to coal in
large boilers. This technology is
being replicated in 10 locations.
An extension of this concept that
includes utilization of sewage
sludge is being demonstrated under
a grant to the State of Delaware.
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Two systems for recovering
energy from mixed municipal solid
waste through pyrolysis were
demonstrated in Baltimore, Maryland,
and San Diego County, California.
The Baltimore plant, which produces
steam by combusting the pyrolysis
gases, has had numerous mechanical
and air pollution problems and is
presently undergoing an extensive
modification program. After the
modifications are completed, it is
anticipated that the process will
run in an economically and environ-
mentally sound manner. The San
Diego project also experienced
difficulties and is currently not
in operation. Although it is
doubtful that either of these
systems will be replicated in toto,
much was learned concerning the
pyrolysis of solid waste, and this
information should prove useful to
others considering this process.
Six projects to develop source
separation systems are now nearing
completion. Projects in Marblehead
and Somerville, Massachusetts, were
started three years ago to deter-
mine the feasibility of separate
collection techniques to recover
several materials from municipal
waste streams. These two programs
have shown that it is possible to
recover between 25 and 30 percent
of the residential waste stream in
suburban communities. Approximately
15 to 20 other multimaterial collec-
tion programs have begun in the New
England area as a result of the
increased municipal and industry
interest created by the Marblehead/
Somerville projects. A final re-
port presenting the results of this
project will be issued in 1979.
Four projects were started two
years ago on: multimaterial col-
lection through private contract;
multimaterial collection from
apartment buildings; source sepa-
ration and materials marketing for
low-density rural areas; and the
use of handicapped laborers for
processing materials. Final reports
will be issued in 1979.
In addition to EPA-supported
demonstrations of resource recovery
systems, OSW is also conducting
evaluations of other commercial-
scale resource recovery facilities:
refuse-derived fuel plants in Lane
County, Oregon, and Chicago,
Illinois; small modular incinera-
tors with heat recovery; waterwall
combustion units in Europe; a plant
for codisposal of sewage sludge and
municipal solid waste in Duluth;
and a pyrolysis system in Frankfort,
Germany. Evaluations of system
components such as air classifiers
and shredders are also underway.
In cooperation with the Office
of Research and Development, OSW is
conducting studies on resource
recovery as required by section
8002 of the Act on the subjects of:
1) compatibility of source sepa-
ration and mixed waste recovery,
2) small-scale technology, 3) re-
search priorities for resource
recovery and 4) tire, glass and
plastics recovery.
FINANCIAL AND TECHNICAL ASSISTANCE
TO STATE AND LOCAL GOVERNMENTS
The Resource Conservation and
Recovery Act places the primary
responsibility of improving solid
waste management on State and local
governments. The Act provides for
a number of financial and technical
assistance programs for assisting
in that effort.
Financial assistance is avail-
able to develop and implement
comprehensive State solid waste
management plans under Subtitle D
of the Act. Guidelines to assist
in the development and implemen-
tation of State solid waste manage-
ment plans were published in pro-
posed form in August 1978 and will
be finalized in June 1979. These
plans should provide for (1)
regulatory programs for environ-
mentally sound disposal of all
other solid wastes, (2) State
programs to encourage resource
recovery and conservation, and
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(3) planning for necessary disposal
and recovery facilities. In fiscal
year 1979, $11.2 million was avail-
able for these purposes.
A new financial assistance
program resulting from the
President's Urban Policy Message
will help communities to adequately
assess the feasibility of resource
recovery projects and obtain suffi-
cient consultation and staff for
the preparatory steps in implemen-
tation. This program is scheduled
to begin in fiscal year 1979 and
$15 million has been appropriated
for the first year. Urban areas
will be eligible for assistance for
"front-end" steps preceding actual
design and construction of resource
recovery projects. This includes
not only mixed waste resource
recovery processing plants but also
projects involving source separation
(i.e., separation at the place of
generation) of waste materials for
recycling. Eligibility for funding
is not limited to large cities, but
a major portion of the funds will
probably go to jurisdictions of at
least 50,000 population. The aid
will go primarily to agencies with
clear responsibility for implemen-
tation as designated in the State
planning process under Subtitle D.
The first set of applications were
received in December 1978 and
awards are expected to be made in
March or April 1979.
The Act also provides for
technical assistance through the
Technical Assistance Panels Program.
Each EPA regional office has avail-
able a panel of expert consultants
capable of assisting in all areas
of solid waste management. Grants
have been provided to a number of
public interest groups to make State
and local government officials
available to provide assistance as
well. These panels are available
to provide technical assistance
free of charge to State and local
governments and Federal agencies
upon request. Twenty percent of the
funds appropriated under the general
authorization of the Act are used
for this purpose.
The OSW has developed a seminar
series directed mainly at municipal
officials. A first set of seminars
presented alternatives and major
issues in the implementation of
resource recovery. In 1978 the
seminar was conducted in six cities;
approximately 1,000 people attended.
The seminar program will continue
into 1979 and will be expanded to
cover other solid waste management
issues as well.
The Resource Conservation and
Recovery Act provides an opportu-
nity for significant advancements
in solid waste management nation-
wide. The regulations and guide-
lines provide momentum and impetus
for improved practices. Technology
demonstrations, evaluations and
studies will help provide necessary
technical, economic and environ-
mental performance information so
that better decisions can be made.
Financial and technical assistance
programs will provide additional
resources to State and local govern-
ments responsible for implementa-
tion. The Office of Solid Waste
programs in these three areas are
an attempt to provide a balanced
approach to this nationwide effort.
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USEPA REGION 4 SOLID WASTE MANAGEMENT ACTIVITIES
Elmer G. Cleveland
U.S. Environmental Protection Agency
345 Court!and Street
Atlanta, Georgia 30308
In the beginning -- in this instance
the late 1960s -- solid waste management
in Region 4 was at best completely inade-
quate even by standards prevailing at that
time. Before getting into an update on
regional solid waste management activities
we must look at our beginning.
Prior to the passage of the Solid
Waste Disposal Act of 1965, there did not
exist an identifiable state solid waste
program in the region. A survey of land
disposal sites in the late 1960s indicated
over 2500 dumps and fewer than 30 sanitary
landfills which could meet the very loose
requirements that prevailed at that time.
By 1971, total state solid waste program
positions were 42.
State solid waste laws were enacted,
viable programs established, regulations
promulgated, and state plans developed.
Inspection and technical assistance
programs were put into action.
By 1977, over 1000 land disposals met
or exceeded the minimum requirements to be
termed a sanitary landfill and permitted
or approved by the state programs. State
program personnel now exceeds 225 with
increases scheduled to take on the addi-
tional duties associated with hazardous
waste and resource recovery.
While maintaining the successful level
of solid waste management attained, a
combined federal, state and local govern-
mental effort is underway to correct and
eliminate existing and potential environ-
mental hazards from old disposal practices.
New and environmentally sound hazardous
waste processing and disposal facilities
are being designed and constructed.
Some are now in operation.
Resource recovery facilities are in
operation, under construction, and being
planned. Under the President's Urban
Policy, which provides financial assis-
tance for Resource Recovery Project
Development, more than thirty applications
requesting over $3.5 million in Federal
assistance were received from this region.
The Department of Energy has solid waste
demonstration projects in Alabama, Florida
and Georgia.
EPA funding of state solid waste
programs in Fiscal Year 1979 will exceed
four million dollars. Technical assis-
tance through Section 2003 of the
Resource Conservation and Recovery Act
has been delivered to more than 30 local
governments at an approximate cost of
$200,000. This was provided at no cost
to the clients, i.e. local governments.
In the 1980s, we expect to achieve a
level of solid waste management, hazardous
waste control and resource recovery that
should meet our immediate needs and set
examples for the rest of the Country.
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CURRENT RESEARCH ON LAND DISPOSAL OF MUNICIPAL SOLID WASTES
Norbert B. Schomaker
U.S. Environmental Protection Agency
26 West St. Clair Street
Cincinnati, Ohio 45268
ABSTRACT
The Solid and Hazardous Waste Research Division (SHWRD), Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency, in Cincinnati, Ohio, has re-
sponsibility for research in the areas of municipal solid and hazardous waste management,
including both disposal and processing. This research is being directed towards new and
improved systems of municipal solid and hazardous waste management, development of tech-
nology, determination of environmental effects, and collection of data necessary for the
establishment of disposal and processing guidelines.
Division activities in the area of municipal solid waste research have related to
storage, collection, transport, processing, resource recovery, and disposal. Recent
emphasis on energy has resulted in an expansion of the waste-as-fuels program.
The current municipal solid waste diposal research program has been divided into
three general areas: (1) Pollutant Predictions for Current Landfill Techniques, (2)
Alternatives to Current Landfill Disposal Techniques, and (3) Remedial Action for Min-
imizing Pollutants from Unacceptable Sites.
The research activities currently funded under these three general areas have been
classified into seven categories shown below:
1. Waste Characterization/Decomposition
2. Pollutant Transport
3. Pollutant Control/Treatment
4. Co-disposal
5. Environmental Assessment
6. Remedial Action
7. Landfill Alternatives
INTRODUCTION
Increasing amounts of waste residuals
are being directed to the land for disposal
in landfills. At the same time, there is
increasing evidence of environmental damage
resulting from improper operation. The
burden of operating landfills and coping
with any resulting damages falls most
heavily on municipalities and other local
government agencies. Their problems are
complex, involving legislation, economics,
and public attitudes as well as technology,
additionally, comprehensive information on
landfilling techniques and protection of
the local environment is not readily
available.
Current estimates indicate that 144
million tons (as generated with moisture)
of municipal wastes and 260 million tons
(dry) of industrial wastes are disposed of
to the land. It is projected that approxi-
mately 197 million tons of municipal solid
wastes will be generated in the United
States in 1990. A survey of national solid
waste management practices conducted in
1968 by the Federal government through
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cognizent state agencies indicated less
than 6 percent of 6000 land disposal sites
surveyed could be considered sanitary
landfills, based on very modest criteria
not including a re-evaluation of ground-
water pollution. More recent surveys (in
1975 and 1977) indicated a 25 percent in-
crease over a 2-year period in the number
of disposal sites considered to be sanitary
landfills (5740 of 15,821 sites in 1976).
The total number of municipal solid waste
disposal sites (18,500 sites in 1977) ap-
pears to have increased greatly since 1968,
but this can be explained, in part of better
record keeping by state agencies and/or
that environmental enactments have both
severely restricted refuse disposal by
burning or dumping at sea and greatly in-
creased the amount of solid waste gener-
ated as residues from air and water
cleaning operations. The most pernicious
effect of unsound disposal is the con-
tamination of groundwater by leachate;
about half of the United States domestic
water supply is from groundwater. Ground-
water contamination is usually discovered
long after the damage is done and too late
for corrective measures.
The municipal waste disposal program
initiated by SHWRD was designed to docu-
ment and evaluate the potential adverse
environmental and public health effects
that could result from application of
waste disposal methods without proper
precautions for leachate and gas manage-
ment. The information thus obtained will
provide the necessary data for the estab-
lishment of guidelines for communities
to develop economical and environmentally
safe municipal waste disposal management
systems.
Specifically, in the area of landfill
disposal techniques, a comprehensive data
base on the characteristics of municipal
and hazardous wastes will be developed to
assess pollutants within a waste residual,
pollutant release from waste residuals in
the form of leachates and gas, decomposi-
tion rates under varying moisture regimes,
the migration and attenuation of pollu-
tants, and the resultant environmental
damages. In addition, liner materials,
both natural and synthetic, and chemical
stabilization techniques for controlling
leachate movement will be investigated
along with treatment of the collected
leachates. Research efforts will be con-
ducted primarily through laboratory and
pilot studies with some field testing of
laboratory-based results.
In the area of alternative land dis-
posal methods, technical and environmental
data will be obtained to provide a basis
for logical engineering decisions on viable
environmentally sound methods other than
landfill trench method.
In the area of remedial action for
preventing pollutant generation from un-
acceptable landfill sites, engineering
feasibility and design plans will be de-
veloped and tested in field verification
studies.
This research strategy, encompassing
state-of-the-art documents, laboratory
analysis, bench and pilot studies, and
full-scale field verification studies, is
at various stages of implementation, but
over the next 5 years the research reports
developed will be compiled as criteria
and guidance documents for user communi-
ties. Also, the waste disposal research
program will develop and compile a re-
search criteria data base for use in the
development of guidelines and standards
for waste residual disposal to the land
as mandated by the recently enacted
legislation entitled "Resource Conser-
vation and Recovery Act of 1976" (RCRA).
WASTE CHARACTERIZATION/DECOMPOSITION
Studies in this area involve collect-
ing composition data on municipal and
hazardous wastes from individual waste
residuals and landfill disposal sites.
Sampling techniques, analytical methods/
procedures, and waste compatibility and
waste decomposition information will be
developed for implementing better disposal
practices and waste management.
The objectives of this research
activity are to (1) quantify the gas and
leachate production from current best-
practice, sanitary landfill ing and (2)
modify the landfill method to reduce the
environmental impact of gas and leachate
production in a positive and predictable
manner. These objectives are to be
achieved by construction and long-term
monitoring of typical and simulated land-
fill cells and investigation, development,
and optimization of those factors that
control gas and leachate production.
Results are expected only after long-term
10
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monitoring, due to the extremely slow
reaction rates.
Several previous reviews of these
efforts have been presented. See
Schomaker, N.B. and Roulier, M.H., Cur-
rent EPA Research Activities in Solid
Waste Management: Management of Gas
and Leachate in Landfills: Proceedings
of the Third Annual Municipal Solid Waste
Research Symposium, University of Missouri,
EPA-600/9-77-026; and Schomaker, N.B.,
Current Research on Land Disposal of Hazar-
dous Wastes: Land Disposal of Hazardous
Wastes - Proceedings of the Fourth Annual
Research Symposium, EPA-600/9-78-016.
Standard Analytical Techniques
Analysis of the contaminants within a
waste leachate sample is difficult due to
interfering agents. Existing instrumenta-
tion functions well in the analysis of
simple mixtures at low concentrations but
interference problems can be encountered
for complex mixtures at high concentrations
(1 percent by weight and greater). In this
range the sample cannot always be analyzed
directly and commonly must be diluted and/
or analyzed by the method of standard
additions. Options are the development of
standard procedures for diluting and
accounting for errors introduced thereby
or the development of instrumentation
capable of accurate, direct measurements at
high concentrations in the presence of po-
tential multiple interferences. Existing
USEPA procedures for water and wastewaters
are often not applicable. Analytical pro-
cedures are being developed on an as-needed
basis as part of the SHWRD projects. How-
ever, most of this work is specific to the
wastes being studied and separate efforts
were required to insure that more general
procedures/equipment would be developed.
A compilation of analytical techniques1*
used for contaminant analysis has been
published in a report entitled Compilation
of Methodology Used for Measuring Pollu-
tion Parameters of Sanitary Landfill
Leachates, EPA-600/3-75-011 , October 1975,
and SHWRD is currently conducting a
collaborative testing study on leachate
analyses. In this study, leachate samples
were sent to 51 laboratories for analysis
*Superscript numbers refer to the project
officers, listed immediately following
this paper, who can be contacted for
additional information.
of specific parameters. The results ob-
tained have provided information on detec-
tion limits and precision for contaminants
in leachate, using currently accepted
methods developed for water and wastewater.
A second effort^ that has been re-
cently initiated will determine which
sampling and preservation techniques
should be accepted as standards for
groundwater sampling. Other objectives
of the study are to determine if current
sampling methods produce samples repre-
sentative of water contained in the
aquifer being monitored and if ground-
water samples collected in the field can
be treated on location or if laboratory
treatment is required. Six landfill
monitoring wells will be studied using
four different pumping techniques and
thirteen different sample preservation
procedures.
A third efforts recently initiated, is
an in-house activity to determine the capa-
bility of existing analytical procedures to
quantitate priority pollutants in various
waste landfill leachates. Preliminary
efforts will obtain leachates from four
landfill sites, two municipal solid wastes
and two hazardous waste sites, to determine
specific priority pollutants. Data will be
analyzed to resolve analytical methodology
applicable to leachate samples.
Standard Leaching Tests
In studying the potential environ-
mental impact of contaminants, a standard
leaching test is needed to assess con-
taminant release from a waste. Such a
test must provide information on the
initial release of contaminants from a
waste contacted not only by water but
also by other solvents that could be
introduced in disposal. Additionally,
such a test must provide some estimate
of the behavior of the waste under ex-
tended leaching. Experience from ongoing
SHWRD projects indicates that some wastes
may initially release only small amounts
of contaminants, but, under extended
leaching, will release much higher con-
centrations. Such leaching behavior has
an impact on disposal regulation and on
management of a disposal site, and in-
formation on this behavior must be ob-
tained and used in classifying a waste.
The Office of Solid Waste (OSW) has
funded the Industrial Environmental
11
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Research Laboratory (IERL), USEPA project^
to examine this background area and
develop procedures for determining whether
a waste contains a significant level of
toxic contaminants and whether a waste
will release such contaminants under a
variety of leaching conditions.
Validation of a Standard Leaching
Test (SLT) is an effort currently under-
way, funded in part by SHWRD-2 The pas-
sage of the RCRA on October 21, 1976, im-
posing time restraints, necessitated de-
veloping an Interim Standard Leaching Test
(ISLT). Existing leaching tests were
evaluated for those elements that were of
special benefit to the development of an
SLT. This information has been published
in a report entitled Compilation and
Evaluation of Leaching Test Methods, EPA-
600/2-78-095, May 1978. Three candidate
SLT's were chosen for further testing.
This additional effort is being published
in two reports entitled Comparison of Three
Wastes Leaching Tests, Executive Summary
EPA-600/8-79-001 and the Background Data
Report. Also, an Environmental Research
Brief^ dedicated to the rapid dissemination
of information relative to the solid waste
"Extraction Procedure" (EP) portion of
Section 3001 of RCRA is being published.
A second effort^ identified as the
"Extraction Procedure" (EP) test will es-
tablish a data base on toxicity of leachates
from solid wastes and establish recommended
toxicity test protocols in order to estab-
lish criteria defining acute and/or chronic
hazardous wastes. Work has been initiated
on four waste categories: municipal refuse,
Chicago sewage sludge, arsenic sludge and
power industry residuals.
Waste Leachability
The characteristics of leachates from
municipal refuse and mixtures of municipal
refuse and selected industrial and munici-
pal sludges are being studied in several
different projects. Leaching study re-
sults^ for 437 tons of municipal refuse
are being compared to results of leaching
from 117-ton and 3-ton experimental land-
fills located at the Boone County Field
Site (BCFS) of USEPA. This effort is being
published in an interim report entitled,
Boone County Field Site Report: Test Cells
2A, 2B, 2C, 2D. The viral and bacterial
efforts at BCFS have been reported in the
News of Environmental Research in Cincin-
nati , "Survival of Fecal Coliforms and Fecal
Streptococci in a Sanitary Landfill" (April
12, 1974) and "Poliovirus and Bacterial
Indicators of Fecal Pollution in Landfill
Leachates" (January 31, 1975). More infor-
mation can be obtained from the Boone County
Field Site Interim Report.
A strong effort performed under con-
tract at the Center Hill Facility of USEPA,
involves comparing the characteristics of
leachates obtained from 3-ton experimental
landfills containing municipal refuse and
selected sludges of municipal and indus-
tiral origin. The effort is being published
in a report entitled Pilot Scale Evaluation
of Sanitary Landfilled Municipal and
Industrial Wastes.
A third effort currently going on will
determine the health and environmental
significance's of the persistence of fecal
streptococci found in landfilled municipal
refuse. One phase of the study will verify
microbial analytical methods and determine
the presence of study organisms in a vari-
ety of leachates. The second phase will
study the relationship between the extent
of waste decomposition and the microbial
population dynamics.
Waste Decomposition
Waste decomposition data are being
obtained from several ongoing efforts.
One study^ is a modification of the land-
fill method to accelerate waste decomposi-
tion in a predictable manner. This study
was successfully performed on a labora-
tory scale and a report entitled
Sanitary Landfill Stabilization with
Leachate Recycle and Residual Treatment,
EPA-600/2-75-043, October 1973, has been
published. Leachate recirculation with
pH control results in waste decomposition
in a time period as short as 6 months.
Field application will probably yield a 1-
or 2-year decomposition period due to an-
ticipated leachate distribution problems.
A second effort^ involves the eluci-
dation of the role of moisture regime
(different net infiltration conditions).
This study is being performed on a labora-
tory scale. It will yield valuable infor-
mation with respect to the kinetics of
waste decomposition, including CH4 volumes
and production rates. Temperature, den-
sity and moisture all appear to affect
12
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gas volumes produced.
A third effort^ involves the effect of
different waste processing techniques on
gas and leachate production and duration
during waste decomposition. Raw refuse,
shredded refuse, and baled refuse are being
investigated in a simulated landfill en-
vironment. Interim results of this effort
have been previously discussed at the
Engineering Foundation and ASCE Conference:
Land Application of Residual Materials,
held in Easton, Maryland, September 26 to
October 1, 1976, as "A Study of Gas and
Leachate Production from Baled and Shredded
Municipal Solid Wastes." This effort is
being published in an EPA report entitled
Effect of Processing on MSW Decomposition.
POLLUTANT TRANSPORT
Pollutant transport studies consider
the release of pollutants in liquid and
gaseous forms from various municipal and
hazardous wastes and the subsequent move-
ment and fate of these pollutants in soils
adjacent to disposal sites. Although the
potential for damage in general can be
demonstrated, migration patterns of con-
taminants and consequent damages that
would result from unrestricted landfilling
at specific sites cannot be accurately
predicted. The ability to predict must
be developed in order to justify the
requirement for changes in the design and
operation of disposal sites, particularly
for any restriction of co-disposal of mun-
icipal and industrial waste. Both labora-
tory and field verification studies at
selected sites are being performed to
assess the potential for groundwater
contamination. The studies will provide
the information required to (1) select
land disposal sites that will naturally
limit release of pollutants to the air
and water and (2) make rational assess-
ments of the need for and cost-benefit
aspects of leachate and gas control
technology.
The overall objective of this re-
search activity is to develop procedures
for using soil as a predictable attenu-
ation medium for pollutants. Not all
pollutants are attenuated by soil, and, in
some cases, the process is one of delay so
that the pollutant is diluted in other
parts of the environment. Consequently,
a significant number of the research
projects funded by SHWRD are focused on
understanding the process and predicting
the extent of migration of contaminants
(chiefly heavy metals) from land disposal
sites.
These pollutant migration studies are
being performed simultaneously in the areas
of hazardous wastes and municipal refuse.
Several previous discussions of these
efforts have been presented. See Roulier,
M.H., Attenuation of Leachate Pollutants by
Soils, presented at the Management of Gas
and Leachate in Landfills: Proceedings of
the Third Annual Municipal Solid Waste
Research Symposium, March 14-16, 1977,
University of Missouri.
Bibliography and State of the Art
A bibliographyS is being published for
distribution by NTIS only. This document
entitled Transport and Transformation of
Hazardous Substances in Soil: A Bibliography
is the result of a search of literature for
1970 through 1974 and includes information
on the transport, transformation, and soil
retention of arsenic, asbestos, beryllium,
cadmium, chromium, copper, cyanide, lead,
mercury, selqnium, zinc, halogenated hydro-
carbons, pesticides, and other hazardous
substances. The bibliography has been
divided into two volumes to facilitate its
use; the pesticides citations have been
placed in a separate volume. The biblio-
graphy is being published through NTIS only
because most of the information has been
included in the report Movement of Selected
Metals, Asbestos, and Cyanide in Soils:
Applications to Waste Disposal Problems
described below.
A state-of-the-art document^ on mi-
gration through soil of potentially hazar-
dous pollutants contained in leachates
from waste materials has been published,
Movement of Selected Metals, Asbestos,
and Cyanide in Soils: Applications to
Waste Disposal Problems. EPA-600/2-77-022,
April 1977. The document presents a
critical review of the literature perti-
nent to biological, chemical, and physical
reactions, and mechanisms of attenuation
Cdecrease in the maximum concentration for
some fixed time as distance traveled) of
the selected elements arsenic, beryllium,
cadmium, chromium, copper, iron, mercury,
lead, selenium, and zinc, together with
asbestos and cyanide, in soil systems.
13
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Controlled Lab Studies
The initial effort5 examined the
factors that attenuate contaminants (limit
contaminant transport) in leachate from
municipal solid waste landfills. Although
work was strongly oriented towards problems
of disposal of strictly municipal wastes,
the impact of co-disposal of municipal and
hazardous wastes were also considered. The
project studied contaminants normally
present in leachates from municipal solid
waste landfills and with contaminants that
are introduced or increased in concentra-
tion by co-disposal of hazardous wastes.
These contaminants are: arsenic, beryllium,
cadmium, chromium, copper, cyanide, iron,
mercury, lead, nickel, selenium, vanadium,
and zinc. The general approach was to pass
municipal leachate through columns of well
characterized whole soils maintained in a
saturated anaerobic state. The typical
municipal refuse leachate was spiked with
high concentrations of metal salts to
achieve a nominal concentration of 100
mg/1. The most significant factors in
contaminant removal were then inferred
from correlation of observed migration
rates and known soil and contaminant
characteristics. This effort contributed
to the development of a computer simulation
model for predicting trace element attenu-
ation in soils. Modeling efforts to date
have been hindered by the complexity of
soil-leachate chemistry. The results of
this effort have been released in a final
report entitled, Investigation of Landfill
Leachate Pollutant Attenuation by Soils,
EPA-600/2-78-158, August 1978.
The second effort5 in this area
studied the removal of contaminants from
landfill leachates by soil clay minerals.
Columns were packed with mixtures of
quartz sand and nearly pure clay minerals.
The leaching fluid consisted of typical
municipal refuse leachate without metal
salt additives. The general approach to
this effort was similar to that described
in the preceding effort except that (1)
both sterilized and unsterilized leachates
were utilized to examine the effect of
microbial activity on hydraulic con-
ductivity and (2) extensive batch studies
of the sorption of metals from leachate
by clay minerals were conducted. Final
results of this effort have been reported
in a publication entitled, Attenuation of
Pollutants in Municipal Landfill Leachate
by Clay Minerals, EPA-600/2-78-157,
August 1978.
The third effort4 relates to modeling
movement in soil of the landfill gases,
carbon dioxide and methane. The modeling
movement has been verified under labora-
tory conditions. This effort has not
focused on the impact of gases on ground-
water, but considers groundwater as a sink
for carbon dioxide. Results evaluate the
efficiency of vertical chimney vents,
barriers, and forced convection systems.
A fourth effort5 relates to the use
of large-scale, hydrologic simulation
modeling as one method of predicting con-
taminant movement at disposal sites. The
two-dimensional model that was used suc-
cessfully to study a chromium contamina-
tion problem is being developed into a
three-dimensional model and will be
tested on a well-monitored landfill
where contaminant movement has already
taken place. Although this type of model
presently needs a substantial amount of
input data, it appears promising for de-
termining contaminant transport properties
of field soils and, eventually, predicting
contaminant movement using a limited
amount of data.
A fifth effort5 is using an existing
mathematical model for solute movement in
soil to develop a simplified empirical
method for predicting metal movement in
soil . It is intended that this method be
oriented toward a larger number of users
than the large-scale model described above.
The approach is to measure metal movement
rates in a number of well-character!'zed
soils from throughout the U.S. and then to
use this information with the Lapidus-
Amundson model to predict long term move-
ment rates. The correlation of these rates
with soil and leachate properties is the
basis for the predictive method which will
hopefully, not require the use of a computer.
Field Verification
Limited field verification is being
conducted. The initial efforts to date
has consisted of installing monitoring
wells and coring soil samples adjacent to
three municipal landfill sites to identify
contaminants and determine their distri-
bution in the soil and groundwater beneath
the landfill site. The sites represent
varying geologic conditions, recharge
rates, and age, ranging from a site
14
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closed for 15 years to a site currently
operating. Individual site characteristics
were identified, and sample analyses neces-
sary to determine the primary pollutant
levels in the waste soils and groundwater
were determined. Validation of waste
Teachability and pollutant migration poten-
tial are expressed in the final report,
Chemical and Physical Effects of Municipal
Landfills on Underlying Soils and Ground-
water. EPA-600/2-78-096, May 1978.
A second effort^ has been recently
awarded for a limited field verification of
a model developed for EPA for pre-
dicting movement of landfill gases in soil.
The field study will compare observed and
predicted distances that methane has moved
from three municipal solid waste landfills
and will also compare observed and pre-
dicted efficiencies of various gas migration
control systems (trenches, wells, barriers,
etc.). If the model is found to provide
reasonably accurate predictions, it will be
used (in a later effort) to develop design
charts for predicting the extent of methane
migration from landfills and for developing
design charts for methane control systems.
POLLUTANT CONTROL
Pollutant control studies are needed
because experience and case studies have
shown that some soils will not protect
groundwater from contaminants. Even sites
with "good soils" may have to be improved
to protect against subsurface pollution.
The overall objective of the pollutant
control studies is to lessen the impact
of pollution from waste disposal sites by
technology that minimizes, contains, or
eliminates pollutant release and leaching
from waste residuals disposed of to the
land.
The pollutant control studies are
determining the ability of in-situ soils
and natural soil processes to attenuate
leachate contaminants as the leachate mi-
grates through the soil from landfill
sites. The studies are also determining
how various synthetic and admixed materi-
als may be utilized as liners to contain
and prevent leachates from migrating from
landfill sites.
Natural Soil Processes
The treatment by natural soil pro-
cesses of pollutants from hazardous waste
and municipal refuse disposal sites is
being performed in the controlled lab
studies previously discussed in the section
on pollutant transport.
Moisture Infiltration Control
The initial effort*" involves the iden-
tification of the functional requirements
of cover soil and the ability of the various
soil types to meet these requirements. Of
primary interest is the minimization of
moisture infiltration through landfill
cover soils. Other criteria associated with
landfill cover soils, i.e., infiltration,
gas venting, vegetation, soil erosion,
rodent burrowing trafficability will also be
identified. The characteristics of the
various soil types are reviewed individually
and in combination with other soil types to
determine the most suitable type of cover
material for use in meeting the desired
functional requirements for a given disposal
site. The interim EPA report, Selection
and Design of Cover for Solid Waste Disposal
has been reviewed by selected groups in the
user community. Field verification of the
concepts described in this effort are being
pursued.
Li ners/Membranes/Admi xtures
The liner/membrane/admixture tech-
nology6 is being studied to evaluate suit-
ability for eliminating or reducing leach-
ate from landfill sites of municipal or
industrial hazardous wastes. Basically,
the test program will evaluate, in a land-
fill environment, the chemical resistance
and durability of the liner materials over
12-, 24-, and 36-month exposure periods to
leachates derived from industrial wastes,
SOx wastes, and municipal solid wastes.
Acidic, basic, and neutral solutions will
be utilized to generate industrial waste
leachates.
The initial effort for liner materials
being investigated under the municipal solid
wastes program include six admixed materials
and six flexible membranes. The admixed
materials are:
- 2 asphalt concretes, varying in
permeability
- 1 soil asphalt
- 2 asphalt membranes, one based on an
emulsified asphalt and the other on
15
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catalytically-blown asphalt
- 1 soil cement
The six flexible membranes are:
- Butyl rubber
- Ethylene propylene rubber (EPDM)
- Chlorinated polyethylene (CPE)
- Chlorosulfonated polyethylene (HYPALON)
- Polyethylene (PE)
- Polyvinyl chloride (PVC)
The results of the 1-year exposure have been
discussed in a report entitled Evaluation
of Liner Materials Exposed to Leachate-
Second Interim Report EPA-600/Z-76-255.
Setpember 1976. The exposure of these
liner materials has been extended to a 52
month period. Data on gas migration, water
permeability (as in soils), osmotic, and
finger print analysis is being collected
for individual polymeric materials. The
latest exposure results are being published
in a report entitled Liner Materials Ex-
posed to Leachate - Third Interim Report,
EPA-600/2-79-038.
A second effort5 relates primarily to
the identification and description of waste
disposal sites and holding ponds which have
utilized an impermeable lining material.
Also, three potential excavation techniques
for liner recovery operations are described
and discussed. This effort has been pub-
lished in a report entitled Liners for
Sanitary Landfills and Chemical and Hazar-
dous Waste Disposal Sites, EPA-600/9-78-005,
May 1978.
POLLUTANT TREATMENT
The pollutant treatment studies re-
late to the collected leachate that is
physically, chemically, or biologically
treated prior to discharge from the land-
fill site. Also, recirculation and spray
irrigation concepts are considered to be
potential treatment schemes. The overall
objective of the pollutant treatment
studies is to develop technology that
treats the landfill leachate once it has
been collected and contained at the land-
fill site.
Physical-Chemical Treatment
Various physical-chemical treatment
schemes4 were investigated in the labora-
tory. Physical-chemical treatments con-
sisted of chemical precipitation, acti-
vated carbon adsorption, and reverse
osmosis. The activated carbon was quite
effective in removing refractory organics
in the effluent of biological units. The
most promising treatment scheme, an anaer-
obic lagoon followed by aerobic polishing,
was selected for pilot plant evaluation.'
the results of this initial effort have
been reported by Ho, S., Boyle, W. C., and
Ham, R. K., "Chemical Treatment of
Leachates from Sanitary Landfills," JWCF.
Vol. 46, No. 7, July 1, 1974, pp. 1776-
1791.
A second effort4 on the physical -
chemical treatment schemes was an expan-
sion of the initial precipitation,
activated carbon, and reverse osmosis, but
also in ion exchange, adsorption and
chemical oxidation. The results of this
effort have been reported in the Evalua-
tion of Leachate Treatment: Volume I -
Characterization of Leachate, EPA-600/2-
77-186a. September 1977 or Evaluation of
Leachate Treatment: Volume II - Biological
Evaluation of Leachate Treatment. EPA-600/
2-77-186b, November 1977.
A third effort^ involved a laboratory
evaluation of various materials that could
be utilized as retardant materials to min-
imize migration of trace elements pollutants
in landfill leachates. This investigation
involves the use of landfill leachates
spiked with trace elements and passed
through columns of disturbed retardant ma-
terials under anaerobic conditions at con-
trolled flow rates. The following materials
have been investigated: agricultural lime-
stone, hydrous oxides of Fe (ferrous sulfate
mine waste), certain organic wastes, and soil
sealants. Information to date is not suf-
ficient to design a .lining to "treat" a given
amount of leachate. Though effective in re-
tardation, hydrous iron oxides may create
additional problems due to the release of
reduced iron. Flux dependent pollutant re-
tardation does not appear to be significant
enough to warrant substantial work of flow
rate control .
16
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Biological Treatment
Various unit processes for biological
treatment of leachate^ have been investi-
gated in the laboratory. The results of
this initial effort have been reported in
publications previously stated under
"Physical-Chemical Treatment". A second
effort^ has investigated the process
kinetics, the nature of the organic frac-
tion of leachate, and the degree of treat-
ment that may be obtainable using conven-
tional wastewater treatment methods. The
biological methods evaluated were the
anaerobic filter, the aerated lagoon, and
combined treatment of activated sludge and
municipal sewage. Biological units were
operated successfully without prior removal
of the metals that were present in high
concentrations. The results of this
effort have been reported in the Evalu-
ation of Leachate Treatment: Volume I -
Characterization of Leachate, EPA-600/2-
77-186a, September 1977 or Evaluation of
Leachate Treatment: Volume II - Biological
Evaluation of Leachate Treatment, EPA-600/
2-77-186b, November 1977.
Recirculation
Recycling of leachate4 is being in-
vestigated to determine the beneficial
aspects of recirculation as a means of
leachate control and accelerated landfill
stabilization. Recommended design,
operation, and control methods applica-
ble to conventional sanitary landfill
practice will be developed. This effort
was discussed earlier under the "Waste
Decomposition" section, and the published
report is mentioned in that section. The
objective of the initial effort4 currently
ongoing concerning recirculation is to
confirm laboratory studies of the leachate
recycle concept and to explain mass flux
of gas and leachate components. Parti-
cular attention is given to the effect of
evapotranspiration on the rates and quan-
tities of leachate. An assessment of the
cost/benefits of the recycle concept in
accordance with daily operation/implemen-
tation including economic and technical
feasibility, is being prepared.
Spray Irrigation
Spray irrigation4 of leachate has
been investigated as a low-cost, on-site
treatment scheme. Optimum leachate
loading rates and removal efficiencies
for organic and inorganic constituents
are being determined for two soil types.
The technique appears to be sensitive to
moisture stresses (drought).
CO-DISPOSAL
In an effort to assess the impact of
co-disposal, the disposal of industrial
waste materials with municipal solid
waste, a project utilizing large scale
experimental landfill test cells was
undertaken. Concern has been voiced
that the addition of industrial waste
may result in the occurrence of various
toxic elements in leachates and thereby
pose a threat to potable groundwater
supplies. Because the environmental
effects from landfill ing result from not
only the soluble and slowly soluble ma-
terials placed in the landfill but also
the products of chemical and microbiologi-
cal transformations, these transformations
should be a consideration in management of
a landfill to the extent that they can be
predicted or influenced by disposal
operations.
Presently, little is known on what
effect adding industrial waste has on the
decomposition process and the quantity of
gases and leachate produced during decom-
position. There is a strong concern that
addition of industrial wastes, particular-
ly those high in heavy metals, will result
in elevated metal concentrations in the
leachates and potentially, in potable
groundwater supplies. Advocates of co-
disposal of sludges and municipal waste
believe the presence of organics in the
landfill will immobilize heavy metals.
They also believe the presence of such
sludges may accelerate the decomposition
process and shorten the time required for
biological stabilization of the refuse.
Because of the high moisture content and,
commonly, the high pH and alkalinity of
these sludges, periodic analyses of the
leachates in this study for trace and
heavy metals is expected to provide data
to allow rational evaluation of the prac-
tice of co-disposal. The over-activity
is to evaluate and develop a predictable
formulation for the transformation
process.
The initial effort4 involves a study
of the factors influencing (1) the rate of
decomposition of solid waste in a sanitary
landfill, (2) the quantity and quality of
17
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gas and leachate produced during decomposi-
tion, and (3) the effect of admixing indus-
trial sludges and sewage sludge with muni-
cipal refuse. A combination of municipal
solid wate and various solid and semi-solid
industrial wastes was added to several
field lysimeters. All material flows were
measured and characterized for the continu-
ing study and related to leachate quality
and quantity, gas production, and microbial
activity.
The industrial wastes investigated
were: petroleum sludge, battery produc-
tion waste, electroplating waste, inorganic
pigment sludge, chlorine production brine
sludge, and a solvent-based paint sludge.
Also, municipal digested primary sewage
sludge dewatered to approximately 20 per-
cent solids was utilized at three
different ratios. The results of this
initial effort have been reported by
Streng, D. R., "The Effects of Industrial
Sludges on Landfill Leachate and Gas,"
Proceedings - National Conference on
Disposal of Residues on Land, September
1976, pp. 69-76. The updated results of
this effort are being published in a report
entitled Pilot Scale Evaluation of Sanitary
Landfilled Municipal and Industrial Hastes.
A second effort5 to assess the po-
tential effects of co-disposal involves
the leaching of industrial wastes with
municipal landfill leachate as well as
water. Leachate from a municipal solid
waste (MSW) landfill was used to extract the
five industrial wastes and to study movement
of their components in the soil columns.
MSW leachate dissolved much greater amounts
of substances from the wastes and apparently
increased the mobility of these substances
in the soil columns relative to the dissolu-
tion and mobility observed when deionized
water was used as a leaching solution. The
municipal landfill leachate is a highly
odorous material containing many organic
acids and is strongly buffered at a pH of
about 5. Consequently, it has proved to be
a very effective solvent. A sequential
batch leaching and soil adsorption procedure
has been developed that provides information
comparable to that from soil column studies
but in a much shorter time.
A third effort^ involves a study of the
effects of co-disposing of chemically stabi-
lized sludges in a municipal refuse landfill.
The stability, weatherability, pollutant
Teachability, and leaching rate of raw and
fixed sludges will be determined. Test re-
sults show that fixing can cause significant
changes in the properties of sludge, that
fixed sludges are similar to soil, soil-
cement, or low strength concrete, and that
properties are process dependent.
ENVIRONMENTAL ASSESSMENT
The environmental effects of waste dis-
posal to the land need to be determined in
relation to the management and disposal
practices for municipal solid wastes. In
an effort to assess the impact of these
practices, several studies have been initi-
ated. The overall objective is to develop
predictive procedures for forecasting adverse
environmental effects from land disposal
activities and to provide user documents for
implementing field practices for those
methods that eliminate or minimize adverse
effects.
The initial effort? involves deter-
mining the effects of application of com-
posted municipal wastes and sewage sludge
on selected soils and plants of croplands.
Multiple applications of composted muni-
cipal refuse totaling 900 metric tons per
hectare have resulted in satisfactory
crop growth with only a moderate increase
of some heavy metals in plant tissues.
Very little downward movement of heavy
metals was observed under conditions of
heavy leaching in greenhouse or natural
outdoor conditions. The effort has been
published in a USEPA report entitled
Effect of Land Disposal Applications of
Municipal Hastes on Crop Fields and
Heavy Metal Uptake, EPA-600/2-77-014,
April 1977.
A second effort^ involves a deter-
mination or evaluation of vegetation kills
and growth problems associated with land-
fill gas migration as evaluated by mail
survey and on-site investigations. Addi-
tional investigations are being performed
to determine control measures for reducing
vegetation losses, and experimental plot
observations should determine those vege-
tation species most conducive to landfill
environs. The results of this initial
effort have been reported in Study of
Vegetative Problems Associated with
Refuse Landfills, EPA-600/2-78-094,
May 1978.
A third effort^ in this area involves
the screening of woody species for adapta-
18
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bility to landfill conditions of assessment
of planting techniques for exclusion of
landfill gases from root zones. Trees
found to be unsuitable for landfill condi-
tions will be replaced with other poten-
tially adaptable species to obtain addi-
tional tolerance information. The study
will also assess the value of mycorrhizal
fungi in reducing tolerance of trees to
landfill conditions.
A fourth effort has been initiated
to study the operational and asthetic
effects of milled refuse particle size in
a landfill operated without daily cover.
The overall objective of this research is
to establish acceptable parameters for the
operation and maintenance of milled refuse
landfills in order to minimize detrimental
environmental effects. Specific variables
to be evaluated are: the effect of wind
velocities and direction on the movement
of landfill ing material; the amount of
differential settlement associated with
particle size variations; the initial den-
sity in each test cell and subsequent den-
sity with relation to time and consolida-
tion within the cell and the presence or
absence of surface crusting; qualitative
evaluation of nuisance organisms, wild-
life, and the type and amount of plant
growth; and some evaluation of odors and
background conditions potentially respon-
sible for noticeable odors.
A fifth effort2 compares the impact
on ground and surface waters of alternate
types of landfills: mill fill, balefill,
hill fill, strip mine fill, and permitted
sanitary landfill. The effort will in-
clude studies of groundwater, surface
waters, in-situ soil conditions, hydrogeo-
logy, and water mass balance at each site.
REMEDIAL ACTION
An ongoing study by OSW has identified
incidents of well contamination due to
waste disposal sites. Seventy-five to 85
percent of all sites investigated are con-
taminating ground or surface waters. In
order to determine the best practical tech-
nology and economical corrective measures
to remedy these landfill leachate and gas
pollution problems, a research effort has
been initiated? to provide local munici-
palities and users with the data necessary
to make sound judgments on the selection
of viable, in-situ, remedial procedures
and to give them an indication of the cost
that would be associated with such a pro-
ject. This research effort is being pur-
sued at a municipal refuse landfill site
at Windham, Connecticut. The site was
selected from a candidate site list of 17
which took into account appropriate site
selection criteria. This effort consists
of three phases. Phase I will be an engi-
neering feasibility study that will deter-
mine on a site specific basis the best
practicable technology to be applied from
existing neutralization or confinement tech-
niques. Phase II will determine the effec-
tiveness, by actual field verification, of
the recommendations/first phase study.
Phase III will provide a site remedial
guide to local municipalities and users.
The engineering feasibility study has been
completed and a report entitled Guidance
Manual for Minimizing Pollution from Waste
Disposal Sites, EPA-600/2-78-142, August
1978 has been published. This guidance
document emphasizes remedial schemes or
techniques for pollution containment. The
remedial schemes discussed in this document
are:
- Surface Water Control
o surface sealing
o revegetation
- Groundwater Control
o bentonite slurry-trench cutoff
wall
o grout curtain
o sheet piling cutoff wall
o bottom seal ing
Plume Management
o extraction
o injection
o leachate handling
- Chemical Immobilization
o chemical fixation
o chemical injection
" Excavation and Reburial
The scheme currently being considered
for the Connecticut MSW site is a surface
sealing technique which could be followed
by a leachate extraction scheme if required.
A second effort2 involved the sponsor-
ship of a conference of nationally recognized
authorities in the area of Solid Waste Dis-
posal to discuss alternative remedial proce-
dures that could be implemented at the Army
Creek Landfill in New Castle County, Dela-
ware, This three day "Round Table Discus-
sion on Army Creek" was held on November
16-18, 1977. It is planned that discussion
and the consensus of this meeting is to be
19
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published in a proceedings document.
LANDFILL ALTERNATIVES/LAND CULTIVATION
Municipal solid wastes are primarily
deposited in standard sanitary landfills
or incinerated. Because of concern for
environmental impact and economics, other
landfill alternatives have been proposed.
For SHWRD purposes, the alternatives cur-
rently being considered are: (1) deep well
injection, (2) underground mines, (3) land
cultivation, and (4) saline/marshland en-
vironments. The deep well injection and
underground mine alternatives are strictly
orientated towards hazardous wastes and as
such will not be discussed in this sym-
posium or its proceedings. The remaining
two alternatives are, however, orientated
towards municipal waste. In order to
assess the feasibility and beneficial
aspects of spreading and admixing municipal
refuse into the soil, an initial effort6
involves land cultivation and the prepara-
tion of a state-of-the-art document.
Available data indicate that application
of shredded municipal refuse or compost to
marginal or drastically disturbed land im-
proves soil structure and fertility, thus
making revegetation possible. It appears
that the environmental pollution caused by
land cultivation is minimal as compared to
that for landfills, primarily due to mainte-
nance of aerobic conditions and the lower
concentration of waste per unit area of
land. Technical and economic assessment
efforts will follow. Results of this study
were presented in reports entitled, Land
Cultivation of Industrial Wastes and Muni-
cipal Solid Wastes: State-of-the-Art Study,
Volume I - Technical Summary and Literature
Survey, EPA-600/12-78-140a, August 1978
Land Cultivation of Industrial and Municipal
Solid Wastes: State-of-the-Art Study,
Volume II - Field Investigation and Case
Studies. EPA-600/2-78-140b, August 1978.
A second effort^ involves documenting
the disposal of municipal solid wastes in
saline/marshlands. The purpose of this
study is to obtain a document detailing
the present environmental and economic
status of municipal solid waste disposal
into specific saline environments and com-
piling state regulations and policies in
effect for those states bordering saline
waters. Information was obtained by a
questionnaire and over 141 instances of
MSW disposal in coastal saline environments
have been identified in 17 states. Seventy-
seven (or more) have monitoring data
available.
ECONOMIC ANALYSIS
An initial effort^ is being planned to
evaluate the relative importance of the vari-
ous factors affecting the cost of sanitary
landfill ing of solid waste and to provide a
method for evaluating the cost of combina-
tions of waste processing and sanitary land-
filling. This will identify the least cost
disposal alternative under local conditions.
It is intended to provide useful information
to local decision-makers and municipal solid
waste managers in planning and operating
their sanitary landfill operations. The
need for this information is especially
critical in view of the guidelines to be
developed under Subtitle A of the RCRA of
1976.
CONCLUSION
The laboratory and field research pro-
ject efforts discussed here reflect the
overall SHWRD effort in municipal solid
waste disposal research. The projects will
be discussed in detail in the following
papers. More information about a specific
project or study can be obtained by contact-
ing the project officer referenced in the
text. Inquiries can also be directed to
the Director, Solid and Hazardous Waste
Research Division, Municipal Environmental
Research Laboratory, U.S. Environmental
Protection Agency, 26 West St. Clair Street,
Cincinnati, Ohio 45268. Information will be
provided with the understanding that it is
from research in progress and that con-
clusions may change as techniques are im-
proved and more complete data become
available.
PROJECT OFFICERS
1. Mr. Richard A. Carnes, Municipal En-
vironmental Research Laboratory, U.S.
Environmental Protection Agency,
26 West St. Clair Street, Cincinnati,
Ohio 45268. 513/684-7871.
2. Mr. Donald E. Sanning, Municipal En-
vironmental Research Laboratory, U.S.
Environmental Protection Agency,
26 W. St. Clair Street, Cincinnati,
Ohio 45268 513/684-7871.
3. Mr. Michael Gruenfeld, Industrial En-
vironmental Research Laboratory, U.S.
Environmental Protection Agency,
Edison, New Jersey 08817
201/321-6625.
20
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Mr. Dirk R. Brunner, Municipal Envi-
ronmental Research Laboratory, U.S.
Environmental Protection Agency,
26 West St. Clair Street, Cincinnati,
Ohio 45268. 513/684-7871.
Dr. Mike H. Roulier, Municipal Envi-
ronmental Research Laboratory, U.S.
Environmental Protection Agency
26 West St. Clair Street, Cincinnati
Ohio 45268. 513/684-7871
Mr. Robert E. Landreth, Municipal En-
vironmental Research Laboratory, U.S.
Environmental Protection Agency,
26 West St. Clair Street, Cincinnati,
Ohio 45268. 513/684-7871.
Mr. Carlton C. Wiles, Municipal Envi-
ronmental Research Laboratory, U.S.
Environmental Protection Agency,
26 West St. Clair Street, Cincinnati,
Ohio 45268. 513/684-7881.
Mr. Oscar W. Albrecht, Municipal Envi-
ronmental Research Laboratory, U.S.
Environmental Protection Agency
26 West St. Clair Street, Cincinnati,
Ohio 45268. 513/684-7881.
21
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SOLID WASTE DISPOSAL RESEARCH ACTIVITIES
OF THE FEDERAL GOVERNMENT IN CANADA
H. Mooij, P. Eng.
Waste Management Branch
Environmental Impact Control Directorate
Environmental Protection Service
Environment Canada
Ottawa, Ontario
K1A 1C8
ABSTRACT
In Canada the Federal government's role is principally to develop solid waste
management technology, to generate and evaluate technical solid waste management
information, and to develop new or improved guidelines or codes of good practice
relating to various waste management aspects. These activities are conducted on a
national basis for the benefit of the industry and regulatory agencies.
Solid waste research activities in Canada are being undertaken primarily at the
federal government level. Current research activities, relating to land disposal in
particular, are underway in each of the following study areas: landfill leachate '
research; municipal waste disposal site selection; landfill field investigations:
co-disposal studies; landfill gas research; and the NATO/CCMS landfill project. This
paper describes Environment Canada's current research projects in these areas of
interest.
INTRODUCTION
Solid waste research activities in
Canada are being undertaken mainly at the
federal level of government, but also at
the provincial government level, in order
to come to grips with the problems facing
both the private sector and the regulatory
agencies. Some provincial governments are
actively contracting out basic research
studies or undertaking similar in-house
investigations, although most others are
simply studying localized problems of
disposal or local potentials for resource
and evergy conservation. The bulk of the
research effort in Canada is undertaken by
the federal Departmentof the Environment
(Environment Canada).
The Waste Management Branch of Environ-
ment Canada is very active in the resource
conservation and the municipal and industrial
waste management areas of responsibility.
However, the constraints of this presenta-
tion to be the activities of our Branch
relating to the disposal of wastes onto
land.
These activities will be briefly
described under the following headings:
1. landfill leachate research;
22
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2. municipal waste disposal site
selection;
3. landfill field
investigations;
4. co-disposal studies;
5. landfill gas research; and,
6. the NATO/CCMS landfill
project.
LANDFILL LEACHATE RESEARCH
Leachate Production
Although a significant amount of re-
search work has been accomplished to date
on the subject of leachate generation, or
production, at municipal solid waste land-
fills, there are still many basic questions
left unanswered about the actual process
of leaching. Leachate production is
generally an estimated variable, and never
really measured directly at a landfill
site.
The ability to predict leachate quan-
tity and quality is probably the most
necessary feature required for the design
of leachate control systems, including
natural attenuation and leachate treatment
systems. All landfill leachate control
systems design work relies heavily on an
accurate input function describing the
leaching behavior of the landfill. An
estimate is only as good as the "rule-of-
thumb" used, and therefore, we have in-
itiated an attempt to develop a simple
waste leaching model at the University of
British Columbia in Vancouver.
A good quantative, descriptive and pre-
dictive model of the leaching of solid
waste landfills and of the mechanisms
associated with the leaching process may
be important to assess the environmental
impact of leachate on receiving waters;
to aid in the design of any required
leachate treatment facilities; to provide
estimates of the material inputs into an
underlying groundwater system as a first
step in determining leachate concentration
there: and, to assess the likely effects
of co-disposal of various liquid and/or
semi-solid wastes with municipal solid
waste in landfills. For the initial stages
of this work a model was chosen which assumes
a simple physical process to describe the
leaching. The initial model assumes flow-
through of infiltrating water and a mass
transfer of soluble materials from the
solid phase to the liquid phase due to a
concentration difference driving force, as
well as connection within the liquid phase.
The model has been tested for the simple
case of plug flow starting constant rate
or infiltration, insignificant moisture in
the refuse, and a uniform distribution of
leachable materials.
This model provided leachate concen-
trations as a function of time. The cal-
culations require values for the refuse
depth, the rate of infiltration, refuse
field capacity, and three empirically de-
termined parameters. The model has been
fitted to data from solid waste lysimeter
experiments for six contaminant curves and
a range of operating conditions. The
calculated curves and corresponding data
curves generally showed a good correlation
when the empirical parameters were suitably
adjusted.
The model is currently being further
modified to provide both the quantity and
quality of leachate as a function of time,
and for various patterns of infiltration
and fluid flow. Other variables being
tested are various landfill operational
parameters. A final report on the initial
work should be available within the next
few months. Leachate Control and Treatment
Infiltration into disposed refuse results
in the production of leachate which is
recognized to be potentially hazardous to
the environment. There are a significant
number of documented case histories which
show that the uncontrolled migration of
23
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leachate from improperly located waste
disposal sites can result in extensive
groundwater and/or surface water pollution.
These case histories have been used to
demonstrate the need for the design of
leachate control and treatment systems at
waste disposal sites.
There is a growing trend in regulatory
agencies insisting on some degree of
leachate control including collection and
treatment. This trend is disconcerting in
that many leachate control systems have not
been proven technically, while others have
simply been designed to expedite the app-
rovals process. Furthermore, some systems
may be failing because of inadequate design
or improper installation, whereas others
are being over-designed without due regard
to the cost-effectiveness of the systems.
Rarely has the environmental benefit and
the complete cost and benefit of such a
system been evaluated.
Landfill designers, researchers, and
regulatory agencies have become concerned
with problems relating to proper selection,
design, and operation of leachate control
and treatment systems. There is a recog-
nized need to develop practical criteria
for the design and operation of such
leachate management systems.
In response to this need, the Waste
Management Branch and its contractors
sponsored two international round-table
discussions on the topics of leachate
control, held in Vancouver, and leachate
treatment, held in Halifax.
The session on leachate control con-
sidered the topics of natural and engineered
controls to minimize leachate production,
collect leachate on-site, recirculate
leachate, and rectify leachate migration
problems through aquifer manipulation as
a control procedure. A report is being
prepared on the recommended procedures for
leachate control based on a concensus by
technical experts from the U.S. and Canada.
The purpose of the leachate treatment
session was to discuss and document current
treatment concepts, practices, and meth-
odologies.
Attendees at this session included
recognized treatment experts from Canada,
the U. S., Germany and Norway. A report
is being prepared to document the dis-
cussion on the need for and the factors
affecting leachate treatment; the treatment
of leachate in the natural hydrogeologic
environment; biological treatment systems
physical-chemical treatment systems; and,
the concensus of expert opinion expressed
at the session.
With regards to in-situ attenuation,
it was recognized that there is a difficulty
in designing for the use of the natural
setting as an attenuation and/or treatment
system, and although it was agreed that
the assimilative capacity of the hydro-
geologic environment for leachate contam-
inants is quite significant, ground water
contamination will usually result.
The concern, therefore, must be with
the degree of contamination which will be
allowed, and whether such contamination
actually constitutes pollution.
It was recognized that all constructed
treatment systems require, prior to design,
the setting of an effluent quality standard.
Similarly, if the hydrogeologic environment
is to be designed to accept a leachate
loading, water quality standards at a
finite distance downgradient from the base
of the disposal area must be established.
Most commonly, the maintenance of drinking
water standards has been used as a criterion
for leachate discharge in the hydrogeologic
environment.
A realistic leachate discharge ob-
jective would be that leachate must not
impair a reasonable, legitimate, present
or potential off-site groundwater use.
The principal problem which makes it
difficult to define an effluent standard
for the discharge of leachate to the
hydrogeologic environment, is that in
general, the hydrogeologic environment
cannot be improved to allow for an up-
grading of the standard if necessary. At
the treatment facility, such an upgrading
can readily be facilitated.
24
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It could be argued that all landfill
designs, where leachate is discharged to
the hydrogeologic environment, should be
equipped with contingency plans which are
designed to control the discharge of
leachate to this environment should it be
required. If a contingency plan can
successfully be implemented, a setting of
design standards could be readily done.
With respect to engineered treatment
systems, it was agreed that current
processes can produce effluent liquids
virtually free of contaminants, notwith-
standing the high costs involved. How-
ever, at the same time, rather than being
destroyed or converted to a less objection-
able form, the contaminants are either
retained in a highly concentrated residual
stream Or transferred to another mpdiun>,
both of which require disposal.
this symposium by Dr. Don Mavinic of their
Civil Engineering Department.
Leachate Toxicity
At the third annual research symposium
in St. Louis, I briefly mentioned our work
in developing a rapid leachate toxicity
testing procedure. The procedure, using
rainbow trout fingerlings in stoppered
BOD bottles, proved satisfactory for many
test situations.
Most treatment processes have as their
objective, the production of a high quality
effluent liquid without regard for the
residual stream. Since landfills are
frequently the last step in disposal,
simply transferring leachate contaminants
from one form to another for disposal
"elsewhere" was not considered to be a
satisfactory solution to a leachate problem.
Many solid waste disposal systems are
not presently in a position to finance
"best available technology".
Consequently, it is hoped that, for
cases where leachate treatment is clearly
deemed necessary, it will be done accord-
ing to the "most practicable technology"
after consideration of all relevant factors
has been completed. This should be based
on realistic assessment of the potential
of, and expectations for, the disposal
area, be it a surface or a groundwater
system, and the resources at hand to solve
the problem.
Reports on both the control and treat-
ment sessions will be available soon.
Extensive research into leachate
treatment has been underway for the last
few years at the University of British
Columbia, and an in-depth reporting of
this program will be presented later in
Toxicity has often been suggested as a
valuable indicator parameter in surface
waters monitoring programs. However,
standard bioassay procedures are expensive
and generally require large volumes of eff-
luent, and may take up to three days per
sample The rapid toxicity procedure was
developed to overcome these problems,
and it was demonstrated to be a less ex-
pensive, valuable in-situ monitoring
procedure.
A final report on the set-up and use
of the procedure has been pubished.
Our continuing interest in leachate
toxicity led us to develo^ an even simpler
test using Daphnia, and an attempt to
attribute leachate toxicity to concentrations
of specific leachate contaminants. In
addition, work was done to determine p
effects on toxicity, and to assess the
effects of landfill operating variables
such as rainfall, sludge additions, and
elapsed time since disposal, on leachate
toxicity.
Equations were developed by statis-
tical regression analyses of the experimen-
tal data to relate toxicity to contaminant
concentrations. It was found that the
relationship between toxicity and contam-
inant concentrations can best be expressed
25
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in terms of the un-ionized ammonia con-
centrations as well as the concentration
of zinc in the case with the Daphnia test,
or the copper concentrations in the case
with fish tests.
Furthermore, it was reported that the
adjustment of p" in test procedures can
dramatically reduce the toxicity of a
given sample.
A final report is in preparation.
from landfill gas migration problems.
Other criteria also apply.
A pass-fail test is used for each
criteria. Failure to pass any of the
criteria would render the site unsuitable
without special site engineering.
From a public protection point of view,
the major criteria of importance in add-
ition to environmental and health criteria
are aesthetics, traffic, land use designa-
tions and site completion. The operation
and management criteria ensure the selection
of the most operable and cost-effective
location.
MUNICIPAL WASTE DISPOSAL SITE SELECTION
The procedure is based partially on
a variety of procedures documented to date,
and should prove to be a simple, yet effec-
tive decision tool for decision makers in
small communities.
Accepting that landfilling will be a
requirement for many years to come, it is
necessary that technology required to
locate and manage these sites be developed
to a high degree.
The procedure should be finally avail-
able within the next few months.
Over the past year we have been con-
tinuing our development of a selection
procedure for locating suitable landfill
sites which could be used to service small
communities. The procedure will be a
simple, yet comprehensive attempt to pro-
vide a small community with a decision
making process which will assist them in
locating the most suitable site from an
environmental, a public protection, and an
operation and management point of view,
without having to rely on outside exper-
tise. A "cook book" approach is being
used in preparing a final report on the
procedure.
The selection procedure works as
follows. Potential sites are evaluated
against environmental protection criteria,
including distance requirements to property
boundaries based on acceptable attenuation
distances within the local soil environ-
ment, distance requirements to downgradient
water wells, and distance requirements to
ensure protection of nearby dwellings
LANDFILL FIELD INVESTIGATIONS
Although a great deal of research has
already been devoted to landfill technology
the long and inconclusive arguments between
experts over the acceptability of particular
sites clearly points to the need for add-
itional basic technical information. These
arguments are most often prevalent at
public meetings or regulatory hearings
where frequently neither side of the argu-
ment can be adequately supported by firm
technical information.
In spite of the large amount of research
which has already been conducted, problems
arise as a result of the difficulty in
showing the applicability of laboratory
26
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data to field conditions and in the
difficulty in studying the processes
directly in the heterogeneous hydro-
geologic environments of the real world.
Because a large amount of detailed
information has already been gathered at
the C.F.B. Borden landfill, as reported in
previous years, this site offered us an
excellent opportunity for further
investigating both the applicability of
laboratory data for making field
predictions and for the field
investigation of contaminant migration
and attenuation processes.
Several activities have been undertaken,
and will be continuing, at this landfill
site. One such activity includes the
further definition of the physical hydro-
geology by supplementing information from
our past studies with some continuous
core sample analysis for detailed strati-
graphy, point dilution testing for direct
velocity measurements, single well response
tests for determining in-situ K values,
and field dispersivity measurements.
Other activities at the site have
included the geochemical surveying of the
contaminant plume through field measure-
ments of Eh, pH, DO and specific conductance
taken on samples extracted from multi-
level sampling devices.
A comprehensive modeling exercise
completes the long list of activities
being undertaken at the Borden landfill.
The development of a calibrated flow model
is being followed by a simulation of the
distribution of a non-reactive solute,
namely chloride, and then a reactive
species. Lastly, the effects of transient
flow conditions will be examined .
One important aspect of this modeling
exercise is to determine a suitable input
function for the contaminant release from
the landfill itself. In the absence of
historical data from the site, a successful
leaching model such as the one being de-
veloped at the University of British
Columbia may provide necessary information.
If modeling is to have a place at all
in our future work, such as has been
suggested by Weston in their report to
EPA on "Pollution Prediction Techniques
for Waste Disposal Siting", then the
Borden work should be the "proof of the
pudding".
Trace metal-oxide coating studies are
also being undertaken to determine the
contribution to contaminant levels in the
downgradient soils due to the release of
trace metals from soil oxide coatings
being dissolved under reducing conditions.
Studies have shown that the bulk of the
trace element contect of contaminated ground
water may be derived not from the waste
material itself, but from the natural
manganese and ferric oxide coatings on the
surrounding material through which the
leachate moves. Another part of the field
studies consists of the evaluation of the
degree on anaerobic decomposition of
leachate organics migrating through saturated
soils under anaerobic conditions. Initial
results have shown a COD reduction of 86%
after 1.5 meters of travel and a TOG re-
duction over the same distance of 90%.
CO-DISPOSAL STUDIES
Septic Tank Sludge and Municipal Refuse
Our previous research project, on the
effect of adding septic tank pumpings to
refuse has been completed. The general
finding of this research was that the
addition of septic tank pumpings, in
sufficient quantity, significantly re-
duced the mass of contaminants discharged,
and particularly heavy metals, when com-
pared with a control containing no pumpings.
This effect, attributed largely to bio-
logical activity, was reduced when rain-
fall rates were increased from 15 in (381 mm)
27
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to 45 in (1143 mm) per year. Increased
gas production and a greater initial per-
centage of methane gas combined with re-
duced contaminant mass discharges at the
high septic tank pumping loading rates
made this technique look promising from
both an environmental and an energy re-
covery viewpoint. Before proceeding
with a large scale operation, however, it
was felt necessary to determine whether
or not the tie up of metals was permanent
or simply transient in nature.
Metal Sludges and Municipal Refuse
Having -fenonstrated the beneficial
effects of adding untreated biological
sludge to landfills in terms of achieving
metal tie-ups, we decided to undertake
further work to determine whether or not
these previously found beneficial effects
would apply when industrial sludges were
added to the refuse as well.
It was decided, therefore, to con-
tinue to apply water to the existing 9
lysimeters at the rates which had been
previously used, and to analyze gas and
leachates on a continuing monthly basis.
Rainfall --applications and leachate
collection have been continued since the
termination of the original contract, and
with only three exceptions, all leachate
contaminant concentrations have continued
to decrease. The exceptions are one tank
which showed increase in colour but no
other increases; another tank showed an
anamalous steady increase in iron
concentration; and yet another showed an
initial increase in iron concentration
but then a drop to the previous low level.
Generally, pH HAS INCREASED.
Concentrations or metals such as cadmiun
and lead decreased to below detection
limits for most tanks.
A series of thirteen lysimeters were
constructed using 12 inch diameter PVC
pipe. Flat bottoms were welded to each. A
specially designed sealed tops were con-
structed. The necessary additions of
septic tank sludge and an arsenic contain-
ing waste and an electro-plating sludge
were each determined based on past co-
disposal experience.
The tanks were filled and put into
operation in August 1978. Results to
date are still being analyzed, and the
study will continue into 1981.
There is presently no indication
that desorption of contaminants is occurr-
ing. However, a continued increase in
gas production in some tanks shows that
biological activity is continuing, and if
biological activity is the mechanism which
is causing metal tie-ups, this indicates
that desorption may not occur for some
time yet, if at all.
A final report should be available
this summer, 1979.
LANDFILL GAS RESEARCH
Gas Production and Migration
The objective of our gas production
and migration study is to provide infor-
mation about gas composition, pressure,
and production in landfills. Such infor-
mation is essential for both an analysis
of gas migration into adjacent soils and an
assessment of gas recovery potentials at
landfill sites. This study, to be
discussed in detail later in this program
by Dr. Grahame Farquhar of the University
of Waterloo, will also involve the use of
field data in the calibration of a
28
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previously developed gas transport model.
The calibrated model will be used to
display variations in gas migration
patterns and to evaluate various gas
control and recovery schemes.
The completed St. Thomas Landfill
Site is divided into two sections. The
section under study was in operation
from 1967 to 1978. This section is com-
prised of approximately 24 acres of refuse
with an average depth of 40 feet. The
gas production wells, the gas monitoring
and pressure probes, and the various
greenhouse facilities.
Gas Recovery and Utilization
Although it is being recognized that a
municipal solid waste landfill may be a
significant energy source, it is clearly
not feasible to tap smaller sites in
remote locations for low BTU content gas
supplies for consumption elsewhere.
Unfortunately, there is usually no nearby
gas distribution system available. Even
if a pipeline could be found next to every
small site, the economics of cleaning the
gas to pipeline quality could be prohibitive.
Our study addresses the possibility of
extracting landfill gases year round at
any site and using these gases for an
on-site energy supply. One market which
could readily benefit in Canada from such
a readily available supply is the energy
intensive greenhouse industry, which
presently faces fuel costs of up to
$30,000 per year per greenhouse acre.
The gas production well consists of
a 36 inch augered bore hole, logged as
1 foot of fill, 28 feet of refuse and 3
feet of native soil. A 6 inch diameter
PVC pipe with an attached 8 feet of
stainless steel well screen (50 slot)
was placed in the centre of the augered
hole. The hole was then backfilled with
pea gravel, with gas pressure and mon-
itoring probes"inserted at various depths.
The top ot the gas production well was
closed using 1 1/2 feet of 36 inch
diameter concrete tile. Bentonite was
placed around the tile and a concrete
plug was used at the surface. A con-
crete cap is placed on top of the concrete
tile.
A rubber adapter is being used to
connect the pipe leading from the gas pump
to the concrete cap, so as to allow pump-
ing directly off the gravel pack to permit
an assessment of the feasibility of
pumping off such an inexpensive gravel
pack without having to install gas ex-
traction well hardware. After completion
of pumping from the gravel pack, 6 inch
PVC pipe will be connected directly to
the gas line feeding from the gas pump.
California studies have suggested
that the best economics lie in the direct
use of processing and refining. Our 10
month study is intended to demonstrate
the use of the collected gas to supply
the energy requirements of a small green-
house throughout the year. It is planned
to grow tomatoes in this greenhouse situ-
ated on a completed site in St. Thomas,
Ontario.
The gas recovery system extracts the
gas from the production well, passes the
gas through a water knock-out drum and
either pumps the gas to a furnace within
the greenhouse or exhausts the gas to the
atmosphere.
The control on the gas system will be a
pressure release valve. The pump will run
continuously at a set flow rate, and if
the pressure goes up in the line, the
pressure release valve will allow gases
to exit to the air. When the furnace is
29
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not in operation, all the gas will be re-
leased to the air.
NATO/CCMS LANDFILL PROJECT
A forced air furnace has been adapted
to utilize methane gas. A back-up electric
furnace will be installed in case of
system failure, to prevent crop damage
due to frost.
A total of 46 gas monitoring and
pressure probes were installed. In addition,
3 gas monitoring and pressure probes were
installed below the greenhouse liner to
monitor for gases coming from the fill
underneath the greenhouse.
The complete system is currently
in operation, and methane concentration
and pressure distributions within the
landfill, changing as a result of varying
pumping rates, are being monitored.
A major international effort is
underway among the member countries of
NATO, including the U. S. and Canada.
The purpose of the pilot project is to
study hazardous wastes management, and
one part of this project is a landfill
study being supported by the U. S.,
Canada, Norway, the U. K., the Netherlands,
and the Federal Republic of Germany.
The purpose of the landfilling study is
to assess the role of landfilling in
hazardous waste disposal. As Chairman
of this sub-project for the next three
years, I will be reporting on our de-
liberations and coordinating input from
the various landfill research programs being
undertaken by each participating
country. All submissions will be used
to prepare a final project report to
NATO.
The study will be completed in
August, 1979 and a final report should
be available shortly thereafter.
The results of our work should have
a significant impact on policy planning
within the member countries.
One of the tapics to be addressed
will be the co-disposal of industrial and
municipal refuse. Member countries at
present appear to have opposing view
points on the merits of co-disposal, and
the resolution of this issue, if at all
possible on the basis of research re-
sults, should prove to be a most inter-
esting challenge.
Another very important aspect of
our joint international undertaking is
the expressed desire by some member countries
to pursue future research efforts on a
cooperative basis and to establish a
formal information exchange.
In accordance with this spirit of
developing cooperative international
efforts, we have already initiated a
coordination with the Solid and Hazardous
Waste Research Division of EPA of our
respective landfill gas research studies,
in the hope that we can mutually benefit
from each other's work from the outset,
and avoid costly duplication. It may
even be possible to directly tie into
similar German studies now getting
30
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underway. The benefits of such an inter-
national coordination of efforts will
obviously accrue to us all.
The landfill sub-project will be
completed in late 1980.
31
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EFFECT OF MOISTURE REGIMES AND
TEMPERATURE ON MSW STABILIZATION
Edward S. K. Chian
Georgia Institute of Technology
Atlanta, Georgia 30332
and
Foppe B. DeWalle
University of Washington
Seattle, Washington 98195
ABSTRACT
The production rate and the composition of gases released during anaerobic degrada-
tion of solid waste in laboratory-simulated landfills were measured. The major gases
observed were C02, H~ and CH,. The moisture content, which -was found to be the most
important variable affecting the rate of gas production, must be above 75%, based on the
dry weight of solid wastes, but below 100%, or field capacity, to maximize gas production
while holding the generation of leachate to an acceptable minimum. The initiation of
methane generation is strongly influenced by the pH and buffer conditions of the solid
waste moisture.
INTRODUCTION
Landfills are considered to be the
ultimate sites for disposal of solid
wastes. A stabilized, well-engineered
and well managed landfill, such as an
approved sanitary landfill, is usually
much more environmentally acceptable than
a poorly designed, inappropriately opera-
ted and unstabilized one. In fact, under
the new solid waste law (Pl-94-580),'
wastes, residues and hazardous materials
cannot be disposed of in other than
approved sanitary landfills. After the
solid wastes are placed in the sanitary
landfills, some impairment of environ-
mental quality, however, can result from
the release of explosive gases produced
by decomposing refuse and the movement of
leachate generated by rainwater infil-
trating the solid wastes. One way to
minimize such insult to the environ-
ment is to accelerate the process of
stabilization of solid wastes and to
recovery by-product of value, e.g., the
methane gas.
A number of studies has concluded
that it is technically feasible to
recover methane from anaerobically decom-
posing solid waste in landfills (1-6).
Augenstein et al. (7) have shown improve-
ment of converting shredded solid wastes
to fuel gas by employing finely divided
calcium carbonate as a pH buffer. The
rate and amount of gas produced, however,
are uncertain, as is the influence of
environmental factors such as moisture
content, density, waste particle size,
temperature, exposure to air and buffer
conditions. Because systematic testing
is best accomplished" on a laboratory scale,
the bench-scale study described here was
initiated to evaluate the effects of these
factors. Shredded municipal solid waste
was placed in sealed containers, and the
production and composition of the gene-
rated gases were measured. The
32
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characteristics of generated leachates were
also determined during the transient-state
of adding simulated rainfall.
MATERIALS AND METHODS
Eighteen 208-liter (55-gallon) steel
containers of the type shown in Figure 1
were used in the laboratory simulation.
Each drum was lined with 10 polyethylene
bags of 0.15-mm thickness. A cushion of
construction sand was placed between the
drum floor and the plastic liner, with a
gradual slope to a height of about 8 cm at
the periphery of the drum to funnel leachate
towards a central drain. A 15-cm layer of
class A gravel was placed inside the liner
to provide for collection of the leachate
and screening of the drain. Two fittings
were installed on the top of each drum.
One was used to apply water to the solid
waste and the second allowed for the col-
lection of gases and provided access for
the thermocouple wires. The drain installed
at the bottom of the container was used to
collect the leachate.
Figure 1. Cross-Section of Solid Waste
Container
The containers were filled with from
55.0 to 80.5 kg (dry weight) of shredded
solid waste. They were then sealed and
maintained under different environmental
conditions. Seventeen of the containers
were located in an insulated and air-
conditioned room maintained at an average
temperature of 17 C (62 F). One was located
in an adjacent room maintained at an aver-
age temperature of 26 C (79 F).
The solid waste was obtained from the
City Solid Waste Reduction Plant in Madison,
Wisconsin. It had been collected by muni-
cipal employees in wards 6, 7, 13, and 15
on Thursday, January 15, 1976. In ward 6,
located in downtown Madison, the values of
the homes were generally less than $10,000.
Ward 7, also located in downtown Madison,
is composed largely of old homes in the
$20,000 range, many of which are occupied
by students. Wards 13 and 19 are both in
suburban areas with homes in the $50,000
and $30,000 ranges, respectively• The
solid waste is collected once a week and is
brought to the reduction plant where it is
milled by a Tollemache mill and shredded to
a nominal size of 0.7 to 2.5 cm.
The gas produced in the test cells was
collected with Mariotte flasks consisting
of two bottles, one of which was placed at
a higher level than the other and filled
with water (Figure 1). As the gas was pro-
duced, it flowed into the upper bottle,
displacing water into the lower bottle. The
volume of gas produced was determined by
measuring the change in water levels. Gases
were collected intermittently rather than
continuously, and the drums were kept com-
pletely sealed except for brief periods dur-
ing gas measurement.
Simulated rainfall was being applied
after the initial phase of studies on
steady-state moisture content. During the
transient-state testing, a buffering sub-
stance, NaHC03, at a concentration of 25.5
g/£ was added to one of the test cells to
observe its effect on both the rate of gas
production and the stimulation of methane
formation.
33
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RESULTS AND DISCUSSION
The initial data collected in the pre-
sent study have been presented previously
by Chian et al. (8) and DeWalle et al. (9) .
All containers produced gas, the amount
varying between 0.09 and 6.0 £/kg dry
weight, as shown in Figure 2. Details of
the experimental conditions were given in
the aforementioned articles (8,9).
The effect of the different environ-
mental variables can be deduced from the
data in Figure 2. The largest amount of
gas was produced in con-
tainers 6, 13, and 14, all of which were
maintained at the highest moisture content,
i.e., 99%, based on the dry weight of solid
wastes. Substantially lower quantities
were produced at 60% and 36% moisture. The
size of the solid waste is probably the
second most important factor, as shown by
the gas production from cells 4, 15, and
18. The moisture content of these three
cells was maintained at 78%, but the cells
contained waste of different sizes. Cell
18 contained 12.5-cm solid waste, and cell
4 contained 25-cm waste, whereas all other
cells (including cell 15) contained 2.5-
cm waste. Increasing the density of the
solid waste tends to decrease the gas pro-
duction (cell 12 and 16, Figure 2), possi-
bly because of a decrease in the effective
surface area exposed to enzymatic hydro-
lysis. Temperature is shown to be the
environmental variable having the least
effect on gas production (cell 1, 9, 7 and
11, Figure 2).
While the gas production data for
the containers clearly showed the effects
of the environmental factors, significant
variability was found among individual con-
tainers maintained under identical condi-
tions. The highest gas-production rate at
the 36% moisture content, for example was
265% of the average value, while the lowest
rate was 14% of the average. At higher
moisture contents the variability was less;
the highest rate at 99% moisture was 113%
of the average, and the lowest rate was 88%
of the average. The small variation in the
rates at 99% moisture is probably a result
of the homogeneous distribution of moisture
within the drums.
Figure 2. Cumulative Gas Production of the
Enclosed Solid as Affected by
Different Variables During Steady-
State Testing
The results in Figure 2 further indi-
cate that in cells having high gas-production
rates, the gas is produced first at a high
rate and then at a reduced rate which is a
factor of 20 to 40 less than the initial
rate. The high initial rates, which were
sustained for up to 40 days, indicate that
a major amount of the gas-producing solid
waste fraction is readily and rapidly
degradable, probably at zero-order rates.
The shape of the other cumulative gas pro-
duction curves generally do not show this
stepwise pattern. Instead, they resemble
more closely a parabolic function, possibly
34
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reflecting first-order reaction rates.
Gas analysis showed that the N. initi-
ally present at 79% was rapidly replaced by
CO-. The most rapid N displacement was
observed in the containers with the highest
moisture contents, reflecting the C0? "bloom"
often observed in landfills (10). After
approximately 50 days, hydrogen was found
in the gas phase from 8 of the 15 sealed
containers (9). The amount of hydrogen
peaked after approximately 100 days and
gradually decreased thereafter. Only one of
the containers filled with large waste
particles (cell 4) has produced methane
during the initial phase study with con-
stant moisture content. The methane, which
constituted 50% of the gas volume, appeared
immediately in the container rather than
following the typical sequence in which
methane generation follows the CO,, bloom
(10). The gas composition data therefore
indicate that at the time of the most recent
measurement most of the containers had just
completed the acid hydrolysis phase charac-
terized by CO„ and H. generation. Methane
fermentation apparently did not start in
most containers within the initial one-
year period.
As the moisture content was found to be
the most important variable during the
initial 400-day monitoring period, this
parameter was studied in greater detail
during the following 500-day period. Six
of the 15 containers received simulated
rainfall at a rate of 25 to 50 cm/year to
simulate transient-state conditions, as
opposed to the steady-state conditions main-
tained during the first period. The
resulting data are plotted in Figure 3,
with day 0 representing the end of the
first 400-day period and the beginning of
the transient—state testing.
The results presented in Figure 3 show
that the greatest gas production occurred
in the containers that were brought to a
99% moisture content at the beginning of
the first period (cells 6, 13 and 14).
Addition of 25 cm/year of simulated rain-
fall to cells 13 and 14 immediately pro-
duced leachate, as the 99% moisture content
Figure 3. Cumulative Gas Production of the
Enclosed Solid Waste During
Subsequent Transient-State Testing
was approaching field capacity. Adding a
buffering substance, 25.5 g/H of NaHCO.,,
to cell 13 approximately doubled the rate
of gas production increasing it to 7 m£/kg/
day as compared to the value of 3.5 m£/kg/
day observed before adding the simulated
rainfall and buffer. Cell 14 received the
same amount of rainfall as cell 13 but, in
addition, it received recirculated leachate
to simulate conditions in a solid-waste
landfill which uses leachate recirculation.
The leachate collected at the bottom of
cell 14 was sprayed on top of a simulated
landfill cover to allow a portion of the
leachate to evaporate. The leachate that
35
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drained through the simulated cover was then
mixed with the simulated rainfall and added
to the top of cell 14. The addition of
leachate and rainwater to the solid waste
resulted in a decrease in gas production,
i.e., it remained at a low level of approxi-
mately 1 m£/kg/day. At 200 days after the
start of the transient period the gas pro-
duction was gradually increasing. Control
cell 6, which was always maintained at a
99% moisture content, continued to produce
gas at a rate between that of cell 13 and
14 and showed a gradually decreasing rate.
The gas produced in the first 300 days
by all three of these high-moisture Con-
tainers is primarily carbon dioxide. How-
ever, cell 13 (the container receiving the
buffer) started producing traces of methane
in addition to carbon dioxide. However,
after 360 days the composition of methane
in gas produced from cell 13 increased to
62%. Although the pH of the leachate
collected from cell 13 was similar to that
from cell 14, i.e., 5.5, the pH of solid
wastes at the upper portion of these drums
might be quite different. The fact that
high methane concentration was produced
after a long period of 360 days of tansient-
state addition of buffered simulated rain-
fall indicates a sufficiently large amount
of buffer is required to initiate methane
fermentation.
Lesser quantities of gas were produced
in the four-cells in which the solid waste
was initially maintained at 36% moisture
(Figure 3). Addition of simulated rainfall
at a rate of 25 cm/year was observed to
generate leachate at the bottom of cell 12,
containing high-density solid waste (485
kg/m dry density), after a 145-day period,
of cell 1 after 200 days, and of cell 2
after 247 days. Cell 9, which received
rainfall at 50 cm/year, produced leachate
after a 120-day period. The pH of leachates
produced varied between 5.5 to 5.6 whereas
the CODs were all slightly exceeding 100,000
mg/£. The gas production in these cells
generally started to increase before the
solid waste had reached field capacity and
before the leachate started to break through,
indicating that a mositure content less
than the field capacity is sufficient to
produce increased gas production.
Before rainfall was added to cell 12,
the container had ceased to produce any
gas. Adding simulated rainfall caused gas
production to resume after a 70-day "accli-
mation" period, indicating that the addition
of water is capable of initiating gas gene-
ration. A similar observation can be made
about the gas production in cells 1, 2 and
9. It is interesting to note that cell 9,
which received the greatest amount of rain-
fall, did not produce twice as much gas as
the containers receiving 25 cm/year, possi-
bly indicating that the initial moisture
content has a greater effect than the amount
of moisture added at a later date. However,
gas production from cell 2 and 12 (Figure 3)
started increasing after 360 days of trans-
ient-state addition of 25 cm/year of simu-
lated rainfall. The results of gas analysis
showed that the oxygen concentrations in
gases produced from cell 2 and 12 were
respectively 11% and 13% with the balance
being carbon dioxide. This indicated a
possible leak of air into these cells
although apparent leaks of these drums were
not detectable. Inspite of this, additional
research will be necessary to determine the
relative importance of the initial moisture
adjustment as compared to a gradual mositure
increase.
The effects of environmental variables
such as moisture content, temperature, size,
density, and exposure to air, as evaluated
in the present study, were compared with
similar variables tested in other studies.
The importance of moisture content in gas
production, for example, is confirmed by
the results of other studies (10, 11, 12).
As shown in Figure 4, those results may
indicate that a logarithmically increasing
gas production can be realized by a linear
increase in moisture content. The plotted
rates of the present study represent those
volumes produced during the initial 20 to
50-day monitoring period when the highest
36
-------
Figure 4. Effect of Moisture Content on the
Rate of Solid Waste Gas Produc-
tion as Noted in Different Studies
rates were observed. The values given here,
therefore, tend to be higher than those
from other studies.
In the present study, methane was
detected only in the container with the
large solid waste (cell 4) and in the con-
tainer receiving buffer (cell 13). Using
shredded solid waste fractions, Merz (12)
observed a maximum CH, content of only
0.9 percent despite the fact that a wide
range of moisture contents were tested.
Even in the large solid waste container,
Rovers and Farquhar (10) noted a methane
content of only 2.8 percent. Ramaswamy
(13), however, often noted stable methane
fermentation as soon as 40 days after
initiation of the tests. Careful examina-
tion of his data shows that methane fermen-
tation does not start until the pH of the
solid waste moisture increases beyond 5.0.
The fact that methane fermentation was found
only in that study may well be a result of
the waste's high food content, which would
have resulted in the release of sufficient
amounts of ammonia during the degradation
of the amino acids to counteract the pH
decrease resulting from the release of free
volatile fatty acids generated during the
acid hydrolysis. The generation of methane
in the container with the large solid waste
may be a result of the relatively slow
release of the volatile fatty acids, pre-
venting the inhibition of the methane-
generating bacteria.
Augenstein et al. (7) observed a high
yield of methane gas, 128 &/kg dry weight,
using unstirred reactors for digestion to
fuel gas of shredded municipal solid waste
and wastewater sludge at a solid content of
48%. This is equivalent to 105% moisture
content on dry solid basis. The high yield
of methane gas production was, however,
accomplished by employing finely divided
calcium carbonate as a pH buffer. This
collaborates with our results obtained with
the addition of buffered simulated rainfall
(cell 13). The fact that methane yield
from cell 13 obtained from this study is
only a small fraction of what observed by
Augenstein et al. (7) indicates that pH
and buffer conditions play a key role in the
initiation of methane production. The
concentration of free volatile fatty acids
in leachate would also seem to play a role
in methane production from the simulated
landfills.
The results in Figure 5 clearly indi-
cate that an increasing moisture content
results in a larger percentage of methane
in the gas phase and a higher rate of
methane generation. However, in several
studies discussed earlier, no methane was
observed at the highest moisture content.
Thus, the way in which the moisture inter-
acts with the solid waste may determine
whether methane generation will or will not
commence. It would therefore seem beneficial
to add buffering substances such as dewatered
37
-------
E = activation energy
R = gas content
The magnitude of the results shown in
Figure 6 indicate that the rate of gas
production, which parallels the hydrolysis
of cellulose, is chemically controlled and
not diffusion limited above a moisture
content of about 75%, i.e., at an activation
energy higher than 10 Kcal/g mole. Sub-
stantially increased rates of gas production
are also at moisture contents greater than
75%. Moisture contents above 100% are not
recommended because leachate will start to
appear in the bottom of the landfill and may
contaminate groundwater.
Figure 5. Effect of Moisture Content on
Percentage of Methane and
Hydrogen in the Gas Produced
by Enclosed Solid Waste
anaerobic digester sludge, industrial alka-
line sludge, spetic tank pumpings, or lime
sludges to initiate methane generation.
Using the temperature data obtained
in the present study and those from Rama-
swamy (13), it is possible to calculate
the activation energy of the reaction,
defined as:
In
where
kl'k2
= E/R
= reaction constants at
temperature T.. and T
Figure 6. Effect of Moisture Content on
Activation Energy of Solid Waste
Placed at Different Temperatures
38
-------
It should be realized that the gene-
ration of gas occurs only under anaerobic
conditions; aerobic degradation of solid
waste does not produce a large amount of gas
because of the synthesis of biomass. It
is also known that methane bacteria are
obligate anaerobic, and exposure to oxygen
will inhibit their action. This fact is
clearly illustrated by data generated by
Stone (14), who measured gas composition
in leaky containers filled with solid waste
and sludge mixtures. The data in Figure 7
indicate that the methane content of the
gas phase decreases with respect to the
carbon dioxide content when the percentage
of nitrogen in the gas phase increases to
80%; i.e., when it becomes equal to the
atmospheric content of this element.
CONCLUSIONS
The present study measured the rate
and composition of gases released during
anaerobic degradation of solid waste. The
major gases observed were CO^. H , and CH
Methane was produced in the container with
the large waste particles and in the cell
receiving buffering substances. The mois-
ture content was the most important vari-
able influencing the rate of gas production.
It is recommended that landfills to be used
for gas production be maintained at a mois-
ture content above 75% but below 100%, or
field capacity, to maximize gas production
while holding the generation of leachate to
an acceptable minimum, thereby preventing
groundwater contamination. If landfills
are to be used for methane production, co-
disposal of refuse with buffering materials
such as digested sludge, softening sludge,
industrial alkaline sludge etc., and main-
taining anaerobic conditions are recommended.
Figure 7. Effect of Nitrogen Content on
the Ratio of Methane to Carbon
Dioxide
REFERENCES
1. Schuler, R. E. "Energy Recovery at
the Landfill," paper presented at the
llth Annual Seminar on Governmental
Refuse Collection and Disposal Associa-
tion, Santa Cruz, CA, 21 pp. (1973).
2. Colona, R. A. Solid Waste Management,
19_, 90 (1976).
3. Hekimian, K. K. ej: a_l. "Methane Gas
Recovery from Sanitary Landfills in
Southern California," Proc. Greater
Los Angeles Area Energy Sym. Calif.
May 16, 1976. West Period Co.
North Hollywood, Calif., 2_, 9 (1976).
4. Mandeville, R. T. "Fuel Gas from
Landfill," Clean Fuels from Biomass,
Orlando, Fla., Jan. 27-30, 1976,
Inst. of Gas Technol., Chicago, 197
(1976).
5. Blanchet, M. J. "Recovery of Methane
due from North Carolina Landfill,"
Oil and Gas Jour., 7b_, 46, 83 (1976).
39
-------
6. Chemberlen, T. L. "Design of Landfill 14. Stone, R. "Disposal of Sewage Sludge
Gas Receiving Facilities," Proc. Amer. into a Sanitary Landfill," U.S.
Gas Assoc. Conf., Boston, Mass., May 24- Environmental Protection Agency,
26, 1976, Paper 76-D-17 (1976). Solid Waste Management Series SW-71D
(1974).
7. Augenstein, D. C. et al. "fuel Gas
Recovery from Controlled Landfilling
of Municipal Wastes,". Resource
Recovery Conser., _2, 2, 103 (1976).
8. Chian, E. S. K., et al. "Effect of
Moisture Regimen and Other Factors
on Municipal Solid Waste Stabilization,"
in Management of Gas and Leachate in
Landfills, ed., S. K. Banerji, U. S.
Environmental Protection Agency, Re-
search and Development Reports EPA
600/9-77-026, Cincinnati, OH 45268
(1977).
9. DeWalle, F. B., Chian, E. S. K.
and Hammerberg, E. "Gas Production
from Solid Wastes in Landfills,"
Jour. Environ. Engineer. Div., ASCE,
104. EE3, 415 (1978).
10. Rovers, F. A. and Farquhar, G. J.
"Infiltration and Landfill Behavior,"
Jour. Environ. Engineer. Div., ASCE,
99_, 671 (1973).
11. Merz, R. C. and Stone, R. "Special
Studies of a Sanitary Landfill,"
U.S. Public Health Service, Bureau of
Solid Waste Management Report EPA-
SW 8R6-70 (1968).
12. Merz, R. C. "Investigation to
Determine the Quantity and Quality
of Gases Produced During Refuse
Decomposition," University of Southern
California to State Water Quality Con-
trol Board, Sacramento, CA (1964).
13. Ramaswamy, J. N. "Nutritional Effects
on Acid and Gas Production in Sanitary
Landfills," Ph.D. Thesis, Department
of Civil Engineering, West Virginia
University, Morgantown, WV (1970).
40
-------
LEACHATE AND GAS PRODUCTION UNDER CONTROLLED MOISTURE CONDITIONS
James J. Walsh
SCS Engineers
Florence, Kentucky
Riley N. Kinman
University of Cincinnati
Cincinnati, Ohio
ABSTRACT
In late 1974, a study was initiated to simulate various types of landfills. The in-
tent of this program was to determine the effects on landfill behavior of varying moisture
infiltration rates, adding pH buffering compounds, prewetting the wastes, varying ambient
temperatures, and codisposing refuse with sewage sludge and various industrial wastes. A
total of 19 landfill simulators were initially constructed. Each was loaded with approxi-
mately 3.2 metric tons of municipal refuse. Twelve were surcharged with small quantities
of various industrial wastes and other materials. Maintenance, operation and monitoring
of these landfill simulators was then begun. Water additions are made on all cells on a
prescribed schedule. Gas and leachate are collected, quantified and analyzed. Refuse,
soil and air temperatures and refuse settlement are recorded.
This paper addresses data derived from the municipal solid waste only test cells over
approximately a 4-year period from November 1974 to August 1978. Test cell moisture
balances are quantified and evaluated. Mass releases of various contaminants in leachate
are plotted and scrutinized. Landfill gases are also addressed in terms of their compo-
nents and total quantities.
INTRODUCTION
Under the Resource Conservation and
Recovery Act of 1976 (RCRA), an inventory
of all solid waste disposal sites is to be
made across the nation. In addition, all
sites identified by the inventory must be
classified as either a "sanitary landfill"
or an "open dump". Sites found to be in
compliance with the Classification Criteria
for Solid Waste Disposal Sites^1' (and thus
posing no significant threat to human
health or the environment) will be classi-
fied as sanitary landfills. Sites found to
be in non-compliance with the criteria will
be classified as open dumps. Open dumps
must be either closed immediately or up-
graded as necessary to mitigate the hazard
identified by the inventory. The closure
and upgrading procedures required will de-
pend in large measure on the degree and
status of the hazard. That is, if the haz-
ard is large and yet to be fully exercised
expensive confinement and/or waste removal
procedures may be dictated. If the hazard
is large but most of the damage is already
done, money would be better directed to-
ward clean-up than confinement and/or
removal. Lastly, if the hazard is small,
the site may be simply closed and funds
used elsewhere.
A framework to assist in these deci-
sions needs to be established. From
numerous previous studies, data for such a
framework has been generated on the decom-
position processes in landfills and the
release of contaminants from landfills into
the environment. However, many of these
efforts have had relatively short-lived
monitoring terms. In addition, the varia-
bility and unknowns of initial conditions
among such studies, have made comparisons of
data and compilation of large data bases
difficult and often impossible.
This project was motivated by the need
for such a data base. The broad objective
of the program was to study solid waste de-
composition and contaminant release at
various types of landfills. Specific
objectives are to determine:
1. The effect of different water
infiltrations on solid waste
decomposition.
41
-------
2. The effect of sewage sludge addi-
tions on solid waste decomposition.
3. The effect of pH buffer addition
on solid waste decomposition.
4. The effect of six selected indus-
trial sludge additions on solid
waste decomposition.
5. The effect of initial water addi-
tion on solid waste decomposition.
6. The survivability of poliovirus in
landfills.
7. The effect of different air and
soil ambient temperatures on solid
waste decomposition.
8. The ability to duplicate monitor-
ing data from two test cells con-
structed and operated under simi-
lar conditions.
TEST CELL CONSTRUCTION
The experimental test facility for
this project is located at the U.S. Environ-
mental Protection Agency's Center Hill
Laboratory in Cincinnati, Ohio. A total of
19 test cells were constructed for this
effort in November 1974 and April 1975.
Fifteen of these are located outdoors and
below the ground surface. These exterior
test cells are arranged in a horseshoe
alignment as shown in Figure 1. The re-
maining 4 cells are located inside the high
bay area of the Center Hill Laboratory and
are above ground resting on the concrete
slab.
Individual test cells consist of steel
tubes 1.83 m in diameter, 3.66 m high and
4.76 mm thick. Steel sidewalls were coated
with coal tar epoxy as a moisture seal.
The outside test cells were placed on con-
crete slabs in a excavated area. Soil was
then backfilled around the sidewalls to
within 0.3 m of the top of the cell.
Several layers of fiberglass cloth were
placed inside at the base of these cells
and extended 0.3 m up the sidewall to pro-
vide a watertight and gas tight seal. The
interior test cells were placed atop steel
bases welded into place.
Provisions for leachate drainage were
installed for all cells. Exterior cells
had a small depression in the concrete slab
and connective piping to a leachate collec-
tion well. This well serves as a central
leachate collection point for all exterior
cells. It is also used as a groundwater
drawdown to prevent pressure and infiltra-
tion of groundwater into the test cells.
Interior cells are mounted on concrete
blocks and leachate drains are attached be-
low the cell bottoms.
The test cells were then readied for
waste loading. To minimize the exposure
time and more closely simulate actual land-
fill conditions all test cells were com-
pletely loaded and covered within 7 days in
each loading period. First, a 15.2 cm
thick layer of silica gravel was applied at
the bottom of each cell. This serves as a
reservoir for leachate and prevents refuse
from clogging the drain. Silica gravel was
EXTERIOR TEST CELLS
INTERIOR TEST CELLS
INSTRUMENTATION
BUILDING
©000©
*— 0
©
©
0
LEACHATE
COLLECTION
WELL
BUILDING WALL'
Figure 1. Test Cell Location Plan
42
-------
selected to prevent any chemical reaction
with collected leachate. Refuse was then
delivered to the site and added in eight
0.3-m thick increments or lifts. Each lift
was compacted with a wrecking ball to a
density of approximately 270 kg/m^. Sludges
and other materials added to selected cells
were applied to the top of each lift (ex-
cept the first) in proportionate amounts.
No additives were applied to the first lift
to avoid any premature leaching of moisture,
Temperature probes were installed atop the
second, fourth and sixth lifts in each cell.
Gas probes were installed atop the second
and sixth lifts.
At completion of waste loading a 0.3-m
thick layer of silty clay cover soil was
applied atop the waste. An additional 0.3-m
thick layer of pea gravel was placed atop
the cover soil, and a gas probe and water
distribution ring installed in the gravel.
A settlement indicator was affixed to the
top of the gravel and mounted inside a
sight glass through the steel lid on each
cell. This lid is bolted down to the test
cell and caulked to provide an airtight
seal. A cross-section of a typical test
cell is shown in Figure 2.
-SETTLEMENT INDICATOR
SIGHT TUBE
^WATER INPUT CONNECTOR
&«P-R
PROBE
NNECTOR
GAS PROBE -
TEMPERATURE PROBE
J_
6AS PROBE
TEMPERATURE PROBE
-03m PEA GRAVEL
0 3 IB SILTY CLAY
- 2.4 m MUNICIPAL REFUSE
0 15m SILICA GRAVEL
-CONCRETE SLAB
LEACHATE DRAIN
WASTE CHARACTERIZATION
As mentioned previously, sludges and
other materials were added to selected
cells. These additives are identified in
Table 1 along with other pertinent initial
loading conditions such as weight and mois-
ture contents. The intent of these addi-
tions was to allow an investigation of what
effects codisposing these materials with
municipal refuse would have on solid waste
decomposition. More specifically, this
arrangement provided test cells which ful-
filled the earlier objectives as follows:
1. Different water infiltration
rates : Test Cells 1 , 2, 3 and 4
Test
2. Sewage sludge additions:
Cells 5, 6 and 7
3. pH buffer addition: Test Cell 8
4. Six selected industrial sludge
additions: Test Cells 9, 19, 12,
13, 14 and 17
Initial water addition:
5.
Test
Cell 11
Figure 2. Cross-section of Typical Test Cell
6. Survivability of poliovirus: Test
Cell 15
7. Different ambient air and soil
temperatures: Test Cells 2 and 16
8. Duplication of monitoring data:
Test Cells 16, 18 and 19
Before loading, all solid waste for each
lift in each cell was weighed and sorted.
Eleven sort categories were used and the
average composition in each cell was then
computed. A summary of the solid waste com-
position of each cell is shown in Table 2.
In addition to categorization, two samples
were extracted from each lift. An 11.4 kg
sample was used for moisture content deter-
mination; these were then averaged over each
cell to determine the moisture contents
shown in Table 1. An 18.2 kg sample was
used for chemical analysis; results were
computed for each sort category. A sample
composited according to average sort cate-
gories in all cells was also chemically
analyzed (see Table 3).
OPERATION AND MONITORING
To more closely simulate actual infield
environmental conditions, all test cells ere
operated in accordance with a strict monthly
schedule. First, gas systems on each cell
are controlled by top positions. As shown
in Table 1, tops may be (1) permanently
open as for Test Cells 9, 10, 12, 13
43
-------
TABLE 1. TEST CELL LOADING AND OPERATION
Cell Number
Refuse
wet weight (kg)
moisture content (1 of ww)
initial moisture (1 )
dry weight (kg)
Additive
type
wet weight (kg)
moisture content (% of ww)
initial moisture (1)
dry weight (kg)
Solid Waste Total
wet weight (kg)
moisture content (% of ww)
initial moisture (1 )
dry weight (kg)
Top Type
open
open/closed
closed
Annual Infiltration
mm
1
1
3025
35
1056
1969
-
__
--
--
-
3025
35
1056
1969
X
203.2
533.30
2 '
2989
35
1043
1946
-
__
--
—
-
2989
35
1043
1946
X
406'! 4
1067.01
3
3007
35
1049
1958
--
-_
.-
—
-
3007
35
1049
1958
X
• 609.6
1602.95
4
3002
35
1048
1954
-
_-
--
--
-
3002
35
1048
1954
X
812.8
2135.87
5
3001
35
1047
1955
sewage
sludge
68
88
60
8
3069
36
1107
1963
X
406.4
1067.01
6
2919
35
1019
1900
sewage
si udge
204
88
179
25
3123
38
1198
1925
X
406.4
1067.01
7
2964
35
1034
1930
sewage
sludge
680
88
598
82
3644
45
1632
2012
X
406.4
1067.01
8
2994
35
1045
1949
CaC03
90.7
10
9
82
3084 7
34
1054
2031
X
406.4
1067.01
9
3001
32
966
2035
petroleum
si udge
1518
79
1199
319
4519
48
2165
2354
X
406.4
1067.01
10
2998
32
965
2033
battery
waste
1291
89
1153
138
4289
49
2118
2171
X
406.4
1067.01
11
2924
35
1020
1094
H20
1243.2
100
1293
0
4217.2
55
2313
1904
X
406.4
1067.01
12
3048
35
1064
1984
electro-
plating
waste
1190.4
80
946
244
4238.4
47
2010
2228
X
406.4
1067.01
13
3006
35
1049
1957
inorgamc
pi gment
waste
1420.6
51
728
693
4426.6
40
1777
2650
X
406 4
1067.01
14
3015
35
1052
1963
chlorine
prod.
brine
sludge
2038.7
24
491
1548
5053.7
31
1543
3511
X
406.4
.067.01
15
1010
32
969
2041
pol io-
vi rus
--
--
-
-
3010
32
966
2041
X
406.4
1067.01
16
2996
35
1046
1950
--
--
--
--
--
2996
35
1046
1950
X
406.4
1067.01
17
2998
34
1046
1972
solvent
based
paint
si udge
1604.0
25
1206
1206
4602
31
1444
3158
X
406.4
1067.01
18
3000
32
966
2034
--
--
--
--
--
3000
32
966
2034
X
406.4
1067 01
19
3012
32
970
2042
--
--
--
--
--
3012
32
970
2042
X
406.4
1067 01
-------
TABLE 2. REFUSE COMPOSITION IN TEST CELLS
(2)
Test
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
ia
19
Avg.
Std.
dev.
Food
9.5
6.3
11.0
5.9
11.3
6.1
5.3
6.6
7.6
11.2
8.7
8.2
6.3
9.0
12.7
7.3
6.0
6.2
8.5
8.1
2.2
Garden
13.8
21.5
30.2
22.6
16.6
25.9
20.3
11.1
17.0
8.2
16.2
9.5
20.7
11.1
8.1
16.3
15.6
9.8
11.9
15.7
5.3
Plastic.
rubber
37.1 6.2 5.0
41.5 5.4 4.5
34.9 8.3 3.3
37.8 6.4 4.1
41.2 6.9 8.0
36.5 5.4 1.3
43.6 6.4 3.4
53.1 8.3 3.9
41.3 11.9 2.1
44 0 6.1 4.0
39.8 5.5 5.6
46.5 5.3 2.7
39 1 5.7 4.4
37.1 6.8 5.6
42.4 7.3 3.5
41.8 10.1 3.8
45.7 5.3 6.0
48.3 6.1 3.3
43.2 7.5 2.7
41.8 6.9 4.1
4.5 1.8 1.5
Ash,
rock and
D p s Fines
1.4 12.2 9.3 3.3 2.5 4.0
2.2 8.5 9.9 3.3 1.2 3.5
.3 8.6 5.9 3.4 2.3 2.4
2.0 5.9 8.8 1.4 3.2 3.5
1.1 8.0 7.0 1.6 1.8 2.9
l.« 8.1 9.4 3.5 1.5 3.0
1.7 9.0 6.4 2.9 2.4 2.8
1.1 5.8 6.4 1.6 1.6 1.7
1.9 8.9 5.3 2.8 .9 2.1
4.4 8.8 7.2 4.7 2.9 3.3
1.6 8.4 9.0 2.0 2.4 3.4
1.2 7.7 8.8 6.1 1.5 4.2
1.4 8.3 7.8 1.8 3.7 2.9
1.5 9.9 8.2 4.1 4.8 4.1
2.9 7.1 7.9 4.3 2.8 3.6
.8 8.9 6.0 1.3 2.7 2.8
1.4 7.7 6.6 2.7 1.6 2.8
3.9 9.3 8.4 3.0 2.9 3.4
1.9 7.4 10.0 1.9 3.0 3.6
1.8 8.3 7.8 2.9 2.4 3.2
1.0 1.4 1.4 1.3 1.0 .66
Percent by wet weight
TABLE 3. REFUSE CHEMICAL ANALYSIS
(3)
Component
CODS
TKN
Total Phosphate
Llplds
Ash
Crude finer
Total carbon
Inorganic carbon
Organic carbon
Sugar as Sucrose
Starch
Asbestos
Arsenictt
Seleniumtt
Mercurytt
Leadtt
BeryHiumtt
Cadmiumtt
Irontt
Zinctt
Chromiumtt
Manganesett
Potassiumtt
Magneslumtt
Calciumt+
Sodiumtt
Coppertt
Nickeltt
folsture
MoistureM
Composition
CompositionHH
Paper
0.804
0.028
0.048
2.47
92.0
21.7
58.0
4.30
53.7
<0.1
3.40
NA1
<0.1
MA
NA
NA
NA
0.36
375
50.0
8.2
13.1
11.2
160
77.5
9.70
4.5
15.7
56.7
35.20
42.6
41.62
Garden
0.815
0.171
3.14
3.04
36.5
16.6
14.4
4.66
9.74
1.71
7.42
NA
NA
NA
NA
NA
NA
NA
330
106
1.1
194
0.135*
4175
0.830*
185
9.34
15.7
156.4
56.91
10.7
15.77
Metal
0.492
0.022
2.79
0.420
4.85
0.235
4.80
3.40
1.40
<0.1
<0.1
NA
<0.1
NA
NA
NA
NA
20.9
625*
175
15.3
870
1.00
80.5
<0.25
37.0
0.221*
115
8.80
6.18
12.2
8.21
Class
0.011
0.140
0.049
1.54
2.25
0.040
0.750
0.220
0.530
<0.1
<0.1
NA
10.2
NA
NA
NA
NA
2.7
3220
9.75
1.1
15.7
2.70
472
16.2
60.0
2.54
19.0
2.00
1.65
12.2
7.83
Food
0.754
3.09
10.4
13.8
41.6
10.5
19.5
2.58
17.0
6.08
8.57
NA
NA
NA
NA
NA
NA
NA
505
59.0
1.3
12.2
0.162*
377
0.465*
804
8.58
12.5
216.5
70.07
3.6
7.56
Plastics,
rubber,
leather
2.14
1.25
1.40
5.02
182
21.5
15.8
5.75
10.1
<0.1
3.42
NA
NA
NA
NA
NA
NA
1.8S§
444
118
2.0
12.1
98.7
289
912
143
12.4
32.0
57.04
49.27
8.7
10.91
Finest
0.935
0.131
1.97
4.85
49.5
6.39
16.4
4.30
12.1
1.18
7.20
NA
1.2
NA
NA
NA
NA
4.2
0.392*
322
13.1
115
135
1.02*
2.11*
400
35.8
33.2
123
49.36
2.9
3.58
Ash,
rocks,
dirt
0.040
0.119
4.48
1.52
19.6
5.85
13.4
7.80
5.60
<0.1
6.40
NA
3.6
NA
NA
NA
NA
4.5
0.340
181
10.1
177
555
2.63*
4.08*
0.209*
32.6
10.1
30.79
18.52
3.2
3.36
Diapers
0.720
0.138
2.65
2.26
96.0
13.7
44.5
0.740
43.8
<0.1
<0.1
NA
<0.1
NA
NA
NA
NA
0.25
99.0
343
0.5
5.90
750
279
360
0.110*
4.14
3.36
133
66.28
1.3
2.47
Wood
0.503
0.228
0.103
1.00
77.9
20.8
51.0
0.380
50.7
<0.1
0.78
NA
<0.1
NA
NA
NA
NA
1.6
0.378
59.4
1.1
50.0
90.0
253
590
572
38.2
27.0
21.43
17.10
2.6
1.99
Composite
0.520
0.247
2.32
2.84
25.8
11.3
24.8
3.08
21.8
3.50
16.2
-------
and 14; (2) permanently sealed closed as
for Test Cells 3, 4, 16, 17, 18 and 19; or
(3) opened and closed in accordance with a
monthly schedule as for Test Cells 1, 2, 5,
6, 7, 8, 11 and 15. The schedule of open/
closed gas systems is shown in Table 4.
These gas systems are closed only during
selected months to simulate temporary in-
field conditions of frozen or saturated
ground cover.
Physical data recording, sampling and
analysis are performed in accordance with
the schedule in Table 5. To summarize this
schedule, gas volumes, refuse temperatures
and refuse settlements are recorded regular-
ly. Gas samples are collected each month
and analyzed via a gas chromatograph for
five major constituents. Leachate samples
are collected each month, their volumes re-
corded, and representative samples prepared.
Total
TABLE 4. MONTHLY CELL OPERATION SCHEDULE
Gas System Schedule
Infiltration Schedule
Amount per month (liters)
Position on Open/
Month Closed Cell Tops
January
February
March
April
May
June
July
August
September
October
November
December
Open
Open
Closed
Closed
Open
Closed
Closed
Open
Closed
Open
Closed
Closed
Type per
Month
None
Low
High
High
High
Low
None
Hone
None
L.OW
Low
Low
203.2 mm
Annual Rate
0
48.52
96.90
96.90
96.90
48.52
0
0
0
48.52
48.52
48.52
406.4
Annual Rate
0
96.90
194.17
194.17
194.17
96.90
0
0
0
96.90
96,90
96.90
609.6
Annual Rate
0
145.72
291.45
291.45
291.45
145.72
0
0
0
145.72
145.72
145.72
812.8
Annual Rate
0
194.17
388.34
388.34
388.34
194.17
0
0
0
194.17
194.17
194.17
533.30
1067.01
1602.95
2135.87
Secondly, water is applied to each test
cell in accordance with the annual infiltra-
tion rates listed in Table 1. As shown,
with the exception of Test Cells 1, 3 and 4,
all test cells receive an annual water
application of approximately 400 mm. Test
Cells 1, 3 and 4 receive annual applica-
tions of approximately 200, 600 and 800 mm,
respectively. In this way, the goal of
varying the moisture regimen is realized in
Test Cells 1, 2, 3 and 4 (with 200, 400,
600 and 800 mm of infiltration, respective-
ly). Water is applied in accordance with
the schedule shown in Table 4. As shown,
an attempt has been made to duplicate in-
field conditions. Specifically, high appli-
cations are made in the normally rainy
months of March, April and May. No appli-
cations are made in the normally dry months
of January, July, August and September.
Low applications are made in the remaining
months.
Monthly samples are then analyzed for 22
parameters. An additional 12 parameters
are determined quarterly and 7 parameters
semi-annually. All analyses are performed
at the Center Hill Laboratory using facili-
ties and equipment used exclusively for
this project. Strict quality assurance pro-
gram procedures are utilized to ensure the
validity of sampling results. Analytical
data derived from the project is punched
onto computer cards and entered into the
memory banks of an EPA in-house computer.
This computational facility can then be
used for plotting project data as an aid in
evaluating results.
MOISTURE BALANCE EVALUATION
Previous papers on this project have
addressed the behavior of the test cells
which have been surcharged with industrial
sludges and other additive materials. It is
46
-------
TABLE 5. DATA RECORDING, SAMPLING AND ANALYTICAL SCHEDULE
SAMPLE
Gas
Soil/
Refuse
Leachate
ANALYSIS
CHu
CO 2
H2
02
H2
Vol ume
Temperature
Temperature
Settlement
TOC
COD
Total Solids
Total Volatile Solids
PH
ORP
Specific Conductance
Alkalinity
TKN
ortho-POn
Fe
Cd
S"
Cl
Hg
V
Be
Se
CN
Phenol
As
Cr6
Cu
Pb
Ni
Zn
Asbestos
Sn
Ti
Total POi,
Organic Acids C2 to C&
Fecal Col i form
Fecal Streptococci
Cr total
As
Phenol
Be
Ti
B
V
Sb
TEST CELL
All
All
All
All
All
16, 17, 18, 19
1 - 15
16, 17, 18, 19
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
2, 4, 10, 13
2, 4, 9, 10, 12, 13, 14
2, 4 9, 12, 13
2, 4 10, 13
2, 4 5, 6, 7, 9
2, 4 14
2, 4 9, 13
All
All
All
All
2, 4, 5, 6, 7, 13, 14
All
2, 4, 14
All
All
All
All
All
All
All
All
All
All
All
All
FREQUENCY
Monthly
Monthly
Monthly
Monthly
Monthly
Daily
Biweekly
Daily
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly -
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Semi-annually
Semi-annual ly
Semi -annual ly
Semi -annually
Semi -annually
Semi-annual ly
Semi -annually
the intent of this paper to concentrate on
the behavior of the municipal solid waste
only test cells.
First, the moisture balance of Test
Cells 1, 2 and 4 will be considered. As
stated previously, these test cells were
established to evaluate the effect of a
varied rainfall regimen. They receive 200,
400 and 800 mm of annual infiltration, re-
spectively. Figures 3, 4 and 5 have been
included to demonstrate the cumulative quan-
tities of moisture added and leached from
each cell. These figures could also be use-
ful in serving as design charts. For a
given annual infiltration of 200, 400 or
800 mm, the total moisture added (in I/kg)
at any point in time can be identified from
the upper line on each chart. The total
moisture leached (also in I/kg) can be iden-
tified from the lower line on each chart.
Several things need to be kept in mind when
using these charts. First, these charts
are based on a 2.4 m deep landfill. For
the same infiltration rate, greater depths
of fill would require an appropriate down-
ward adjustment to both the moisture added
and the moisture leached. Second, the
annual rates of 200, 400 and 800 mm are for
infiltration, not precipitation. Precipita-
tion is greater than infiltration; runoff
and evapotranspiration must be subtracted
from precipitation to yield infiltration.
Some observations can be made from
Figures 3, 4 and 5. First, it is obvious
that the cumulative amount of moisture
leached is considerably less than the mois-
ture added for any point in time. This is
due to the ability of refuse to retain a
certain quantity of moisture. Generally, if
the initial moisture of the refuse plus the
47
-------
ANNUAL INFILTRATION ~ 200 fc
MOISTURE ADDED -
MOISTURE LEACHED %
5137 6850 856.2 10279
TIME IDAYS SINCE CELL CONSTRUCTION)
MM 7 1370.0
Figure 3. Moisture At Test Cell 1
ANNUAL INFILTRATION : 400 U
MOISTURE ADI
MOISTURE LEACHED-.
6 1712 1429 913.7 6850 896.2 10279 IIM7 1370.0
TIME (OATS SINCE CELL CONSTRUCTION!
Figure 4. Moisture At Test Cell 2
342.5 513.7 685.0 896.2 1027.9 ll»87 1370.0
TIME (DAYS SINCE CELL CONSTRUCTION)
Figure 5. Moisture At Test Cell 4
48
-------
moisture added does not exceed this reten-
tion ability, leachate will not appear.
This quantity is known as the "field capac-
ity" and is technically defined as "the
maximum moisture content which a soil (or
solid waste) can retain in a gravitational
field without producing continuous downward
percolation."(5) Generally too, the removal
of significant quantities of leachate marks
the initiation of continuous leaching and
the point at which this field capacity is
attained. Some leachate may be emitted be-
fore this point; but generally, these are
small quantities and may be followed by
times at which no leachate is emitted. As
shown in Figures 3, 4 and 5, the field ca-
pacities for infiltration rates of 200, 400
and 800 mm were attained at 540, 480 and
150 days, respectively. Moisture conditions
present in each test cell at this initia-
tion of continuous leaching are detailed in
Table 6. The equation to define the water
balance in each cell at that time is:
Moisture Retained = (Initial Moisture)
+ (Moisture Added) - (Moisture
Leached)
The moisture retained in each cell at the
point of initial continuous leaching was
found to exist within a fairly tight range
of 1.02 to 1.31 I/kg on a dry weight basis.
(All mass values from this point on are
based on dry weights.) Presumably, after
field capacity has been reached, one liter
of moisture should be leached for each one
liter of moisture added. Thus, the mois-
ture retained should stabilize after the on-
set of continuous leaching. However, this
has not been the case. As shown in Figures
3, 4 and 5, the gap between cumulative
moisture added and cumulative moisture
leached has stabilized somewhat with the
onset of initial continuous leaching; how-
ever, the size of the gap is growing even
larger. This gap is quantified in Table 6.
As shown, Cells 1, 2 and 4 now retain
between 1.45 and 2.23 I/kg. The reason for
this increase cannot be fully explained.
One possible reason, however, may be the
effect of channeling. Channeling exists
when moisture added to a waste percolates
directly through it, failing to fill all
the voids before leaching. Some voids re-
maining in the waste may gradually be re-
taining moisture rather than letting it
channel through; this is one possible ex-
planation for an increasing moisture reten-
tion beyond the point of continuous leach-
ing. (Other possible explanations could be
failure to collect all leachate generated
due to an inordinate time for collection or
perhaps even a leak in the collection sys-
tem. )
LEACHATE QUALITY EVALUATION
Approximately 41 parameters are deter-
mined on leachate samples collected for
this project. Eleven of these parameters
were selected for in-depth investigation.
It is appropriate to note that graphs in-
cluded herein are plots of mass leached
(cumulative kg of contaminant/kg of dry
solid waste) as a function of leachate
volume (cumulative 1 of leachate/kg of dry
solid waste). An attempt was first made to
plot mass leached vs. time. It was thought
that this would be more meaningful to the
designer. However, generally histograms
are somewhat irregular (due to seasonal
fluctuations in applied moisture) and thus
trends are not as readily discernible. To
make the plots in this section useful as a
design aid, it is suggested that the user
consult the previous plots (Figures 3, 4
and 5) to determine expected leachate
volume for a given infiltration rate and
time. Once expected leachate volume is com-
puted, contaminant release can be deter-
mined from the ensuing plots in this sec-
tion.
TABLE 6. MOISTURE BALANCE SUMMARY
TEST
CELL
1
2
4
ANNUAL
INFILTRATION
203.2 0.27
406.4 0.55
812.8 1.09
MOISTURE TO CONTINUOUS LEACHING
No. of
Days
540
480
150
Initial
Moisture
0.54
0.54
0.54
Moisture
Added
(I/kg)
0.49
0.80
0.70
Moisture
Leached
0.01
0.03
0.05
Moisture
Retained
1.02
1.31
1.19
MOISTURE TO DATE
No. of
1370
1370
1370
Initial
Moisture
(I/kg)
0.54
0.54
0.54
Moisture
Added
(I/kg)
1.06
2.14
4.27
Moisture
Leached
0.15
1.11
2.58
Moisture
Retained
1.45
1.57
2.23
49
-------
A plot of pH as a function of cumula-
tive leachate volume is included as Figure
6. As shown, all three curves exhibit
somewhat similar trends. Generally,. pH
values cycled over a wide range between 4.7
and 7.6 in the early leaching stages (be-
tween 0 and 0.32 I/kg of cumulative leach-
ate volume). The average pH during this
phase is seen to be about 5.6. After this
period, pH values continue to exhibit a
cyclic nature, but over a more confined pH
range between 4.8 and 5.6. The average pH
during this phase is seen to be about 5.2.
The large fluctuations and higher average
value in the early phase are to be expected.
Early on in leachate generation, anaerobic
conditions are incomplete. Where they do
exist, pockets of organic acids may be gen-
erated and these may come through as slugs
in the leachate, greatly reducing the pH.
Most of the infiltrating water during this
period, however, merely channels through
the waste without picking up the acids. The
result is a leachate pH similar to that of
the infiltrating water. Later on in leach-
ate development, field capacity is approach-
ed or even attained, reducing the occurance
of channeling. The effect is more thorough
mixing, creating a well-buffered leachate.
In addition, more complete anaerobic condi-
tions prevail. As a result, organic acids
are generated in greater quantities, driv-
ing the average pH to lower values.
TOC
The release of TOC appears to be
approaching an asymptote (Figure 7) at
which only nominal amounts of TOC will sub-
sequently be released. This trend is most
apparent for Test Cell 4 (at 800 mm/year
infiltration) which has yielded the great-
est cumulative leachate volume. The curve
for Test Cell 2 exhibits a slightly higher
trend and thus, greater TOC release for a
given leachate volume. This tendency for
greater TOC release with lower infiltration
rates is not supported by data from Cell 1;
however, the data base from Cell 1 is too
limited to support conclusions about its
ultimate trending.
Despite these observations, there is
generally no substantial difference appar-
ent among the curves for these three cells.
That is, cumulative TOC leached for a given
cumulative leachate volume appears to be
the same regardless of the infiltration
rate. Thus, the effect of a higher infil-
tration rate is merely to accelerate the
release process with time. Ultimately, it
would appear, each cell will have similar
overall TOC release.
As shown in Table 3, the TOC in the
solid waste, when loaded into the test
cells was determined to be 21.8% by dry
weight. Since 31,800 mg/kg of TOC have
been leached by Cell 4 to date, 14.6% of
the initial TOC has been leached by this
Cell. This percentage leached is illustrat-
ed on the right vertical axis in Figure 7.
Since the overall trend of the TOC curve
appears to be asymptotic, it would be pre-
sumed that ultimate TOC leaching would not
be much larger than this value. The bal-
ance of the initial TOC may remain in the
solid waste and never be made available for
032 065 097 129 161 194 226 2.58
MOISTURE LEACHED SI Hf/kt SOLID WASTE)
Figure 6. Moisture Leached: pH
50
-------
032 065 097 l'29 161
MOISTURE LEACHATE » H20/kg SOLID VKSTEI
Figure 7. Mass Leached: TOC
leaching. Alternatively, some of the orr
ganic carbon may be converted by micro-
organisms into gases (C02 and Cfy). A por-
tion of the C02 may then be expected to be
leached as a carbonate.
COD
COD removal (Figure 8) for the 400 mm/
year cell exhibits the highest trajectory,
although a recent trend has caused it to
dip below the 800 mm/year cell. The trend
for the 200 mm/year cell is again lower
than the two higher infiltration cells.
All three cells follow a similar COD pat-
tern.
From observations, the asymptotic-
trending curve for COD appears to have the
same slope as that for TOC. Nevertheless,
it is likely that the COD curve will climb
at a faster rate (i.e., decline at a slower
rate) in the future. Initially, TOC is one
of the primary contributors to the COD
determination. However, inorganics also
contribute to COD and as TOC tapers off
these may become the driving force behind
COD. The cyclical behavior of pH is espe-
cially conducive to the continued appear-
ance of COD in leachate. When pH values
dip low and C02 is available in the absence
of 02, ferrous iron and other inorganic
contributors to COD are created and held
in solution.
032 0.65 097 129 161 194
MOISTURE LEACHED (XI Hf/ta) SOUO WASTE)
Figure 8. Mass Leached: COD
51
-------
Total Solids
TKN
Total solids release (Figure 9) also
reveals an asymptotic trending. The curve
for Cell 2 reveals a greater divergence
from that for Cell 4 than was encountered
previously. Nevertheless, the overall
trend for Cell 2 is similar to Cell 4. As
shown in Table 1, each of these cells had a
total solids dry weight of slightly less
than 2000 kg. Thus, for Test Cell 4, when
42,200 mg of solids have been leached to
date, approximately 4.2% of available
solids has been released. The asymptotic
trend of the curve would indicate that ul-
timate release of solids with time would
not be much greater than this amount.
The curve for total solids reveals a
slightly greater slope than that for TOC or
COD. This is to be expected since release
of solids (ultimately in the form of inerts)
is expected to continue long after release
of TOC and COD have tapered off to nominal
quantities. The nature of the solids re-
leased could be expected to vary consider-
ably with time. Initially, solids released
are probably inorganic dusts and readily
soluble inorganics present in the solid
waste which are being flushed out in the
leachate. The solid waste sort categories
contributing to these dusts are likely to
be the fines, ground glass, ash, rock and
dirt. After this effect is completed,
organic contributions increase and may
reach a 50 - 50 level with inorganics in
the solids. Ultimately, inorganics prevail
in the total solids once again.
Total kjeldahl nitrogen leached by
Cells 1, 2 and 4 is plotted in Figure 10.
Again, the release exhibits an asymptotic
trending for all three infiltration rates.
This time, the release plotted for both the
400 mm and the 200 mm cell exhibit a higher
trajectory than the 800 mm cell. The devia-
tion is greater among the three curves than
was found for COD and TOC and is similar to
that found for total solids. As shown on
the right axis, 74.1% of the TKN assayed
in the solid waste has been leached. This
value is much higher than has been seen in
the release of other parameters. However,
high TKN release is expected since condi-
tions are ideal for biological denitrifica-
tion as a result of high temperature, acid
pH and the presence of organics. Whether
over 70% has actually been released is
questionable, however. It is possible that
the initial TKN reading in the solid waste
is erroneous due to faulty analysis or com-
pilation of a solid waste sample that was
not representative of TKN actually in the
waste.
Metals: Cd, Fe, Hg, Ni, Pb and Zn
Mass release for six selected metals
are presented in Figures 11 through 16.
Generally, these curves can be classified
into three types. The first type is the
familiar asymptotic trend seen for most of
the previously described parameters. This
trend is exhibited by mercury, nickel and
zinc in Figures 13, 14 and 16, respectively.
0.52 0.6!
''6MOISTUie llACHEO HI H^/kfl SOLIOWISTE)
Figure 9. Mass Leached: Total Solids
52
-------
065 0.97 -29 161 194
MOISTURE LEACHED » H^OAg SOLID WASTE)
Figure 10. Mass Leached: TKN
s
3
r
x
- 200 MM/YR
032 065 097 129 16) 194
MOISTURE LEACHED III H^Vkg SOLID WASTE)
•2O
•1.0
0
256
Figure 11. Mass Leached: Cd
As was generally the case for previous
asymptotic curves, the trend for the 400 irm/
year cell has a higher release than that
for the 800 mm/year cell. The 200 mm/year
fluctuated among being below, between and
above the release trend for the other two
cells for mercury, nickel and zinc, respec-
tively.
Mass release to date as a percentage
of that available for nickel was found to
be 15.6%, similar to TOC. Mercury leached,
on the other hand, amounted to only 0.9% of
that available; this was less than any
other parameter investigated. Zinc, how-
ever, was found to have leached 90.6% of
that assayed in the refuse; this was far
greater than for any other parameter inves-
tigated. Release of zinc would be expected
to be high since it has very high solubil-
ity relative to the other metals investi-
gated here. (Nonetheless, it is unlikely
that over 90% of zinc has been leached.
Possible explanations may again be inac-
curate analysis or a non-representative
solid waste sample.) The behavior of nic-
kel and zinc as asymptotic curves is some-
what surprising. Most metals examined here
are governed by chemical reactions and
could be expected to yield a constant re-
lease and straight-line plot. Mercury is
the one possible exception to this since
biological reactions may predominate in the
creation of methyl mere ,sry.
53
-------
032 065 097 129 161
MOISTURE LEACHED ID HjO/kg SOLID WASTE)
3
•30 o
,0
Z"58
Figure 12. Mass Leached: Fe
„* '
'o
B
0'32 o'65 O97^9^61 I 94
MOISTURE LEACHED III H,O/kg SOLID WASTE)
1-0
2.56
Figure 13. Mass Leached: Hg
The second type of curve, a linear re-
lationship, was observed for cadmium and
iron in Figures 11 and 12, respectively.
In each case, the trajectories for the
400 mm and 200 mm/year cells exhibit the
same type of straight line behavior as for
the 800 mm/year cell. However, the 400 mm/
year cell plot in the cadmium figure ex-
hibits a lower trajectory than that for the
800 mm/year cell. The 400 mm cell plot for
iron exhibits its usual higher trajectory
than the 800 mm cell. The percent of avail-
able mass released is similar for both these
metals at 9.6% for cadmium and 7.7% for
iron. However, owing to the apparent non-
declining (straight line) growth trends ob-
served for cadmium and iron (relative to
the declining asymptotic trends seen else-
where) ultimate release of these two metals
could be expected to greatly exceed these
percentages.
The third type of curve observed among
these plots is exhibited by lead in Figure
15. This plot shows an initial linear re-
lease, followed by a sharp increase. This
trajectory change occurs at a total leach-
ate volume of approximately 1.61 I/kg for
the 800 mm/year cell. Oddly, however, this
change occurs at a leachate volume of about
0.65 I/kg for the 400 mm/year cell. The
reason for this behavior is unexplained;
generally before, we have seen similar tra-
jectory behavior and changes in trajectory
to occur at a single total leachate volume,
regardless of the infiltration rate.
54
-------
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-------
065 0.97 I Z9 I 61
MOISTURE LEACHED Bl H20/kg SOLID W4STE)
Figure 16. Mass Leached: Zn
•900
•800
•700
5
•600 *
g
i
•500 2
-«o §
*
•300 S
tn
-200 3
"1111-
3*0
S5 700 87S
TIME IQMS SNCE CELL CONSTRUCTION!
Figure 17. Gas Composition At Test Cell 16
50% through the fourth year. Typical atmos-
pheric gases (nitrogen and oxygen) consume
the balance of gas compositions and were
found to contribute up to 85% of gas through
the first year before declining steadily to
levels between 0 and 20%. Other gases (e.g.
hydrogen) were also detected over the time
period shown but were at trace concentra-
tions (less than 1%) and therefore, not
shown. Generally, gas composition fluctuat-
ed dramatically with time. Despite these
sometimes severe fluctuations, the overall
trends shown in Figure 17 generally follow
the theoretical gas production patterns re-
ported by Rovers and Farquhar.(°/
A plot of gas quantity with time for
Test Cell 16 has been included as Figure 18.
Data included is for a 1-year period
stretching from 2^ to 3^ years after test
cell construction. As shown, gas volumes
have fluctuated between 0.05 and 1.0 ml/
kg/day. Overall trends indicate an average
of approximately Q.5 ml/kg/day over this 1-
year period for a "cumulative gas generation
of 0.18 1/kg/year. Because attempts to
seal the test cells and quantify gas volumes
were unsuccessful in the early years of
this project, ultimate gas production
volumes cannot be determined.
ACKNOWLEDGEMENTS
The work upon which this paper is
based was performed pursuant to Contract
No. 68-03-2758 with the U.S. Environmental
56
-------
1030 se M42
TIME {DAYS SINCE CELL CONSTRUCTION)
Figure 18. Gas Quantity At Test Cell 16
Protection Agency. The authors would like
to express their appreciation to Mr. Dirk
R. Brunner, Project Officer, for his assis-
tance. The data base used in preparing
this paper was obtained from the efforts of
Systems Technology, Inc., pursuant to EPA
Contract No. 68-03-2120.
REFERENCES
1. U.S. Environmental Protection Agency.
"Solid Waste Disposal Facilities,
Proposed Classification Criteria."
Federal Register. February 6, 1978.
Part II. pp.4942 - 4955.
2. Swartzbaugh, Joseph T.; Robert C.
Hentrich; Gretchen Sabel. "Evalua-
tion of Landfilled Municipal and
Selected Industrial Solid Wastes."
U.S. EPA Contract No. 68-03-2120.
June 1977. p. 15.
3. Streng, D.R. "The Effects of the Dis-
posal of Industrial Waste Within a
Sanitary Landfill Environment."
Residual Management by Land Dispos-
al, Proceedings of the Hazardous
Waste Research Symposium. Febru-
ary 2 - 4, 1976. pp. 67, 68.
4. Streng, D.R. "The Effects of Indus-
trial Sludges on Landfill Leachates
and Gas." Management of Gas and
Leachate in Landfills, Proceedings
of the Third Annual Municipal Solid
Waste Research Symposium. March 14 -
16, 1977. p. 44.
6.
Fenn, Dennis 6.; Keith J. Hanley;
TruettV. DeGeare. "Use of the
Water Balance Method for Predicting
Leachate Generation from Solid Waste
Disposal Sites." October 1975. p. 4.
Rovers, F.A. ; G.J. Farquhar. "Gas
Production During Refuse Decomposi-
tion." Water, Air and Soil Pollu-
tion. 2-483. 1973.
57
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GAS PRODUCTION IN SANITARY LANDFILL SIMUIATORS
T. E. Myers, J. C. Duke, Jr., P. G. Malone, D. W. Thompson
U. S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39180
ABSTRACT
Gas compositions and production rates from sanitary landfill simulators during the
initial 100 days of study were determined using conventional gas chromatography and a
newly developed, automated gas production monitoring system. The automated gas monitoring
system allows the simulator to release gas only when the presssure in the simulators
exceeds surrounding atmospheric pressure by 2 cm water column. Measurement of gas flow
with a thermoelectric device is an improvement over previous systems because the units do
not have to be corrected for ambient temperature and pressure variation. This measuring
system also eliminates leakage (through liquids and/or gaskets) which has complicated
volumetric determinations in previous published studies. Gas flow, barometric pressure,
ambient temperature, and test cell (simulator) temperature are automatically digitized and
recorded by a data logger at hourly intervals. Gas samples were analyzed for oxygen,
nitrogen, carbon dioxide, methane, hydrogen and water vapor. The gas- analysis system
and the production monitoring system are described and data for the first one hundred days
of operation are presented.
Gas production measurements are in good agreement with those reported in the litera-
ture for similar systems. No methane or hydrogen has been detected in gas samples.
Carbon dioxide has been the only product gas observed to date.
INTRODUCTION
Gas generation in sanitary landfills
creates two major problems. Carbon dio-
xide produced by the fill goes into solu-
tion in surrounding groundwater and causes
a "hardness halo" in the groundwater near
the fill. Methane produced by anaerobic
decomposition can migrate off-site and
create hazardous conditions in surrounding
structures. Many investigators have
reported production of combustible gas from
municipal solid wastes (1, 2, 3, 4, 5, 6),
and economic methane recovery from sanitary
landfills has been demonstrated (7, 8).
Accurate measurement of the composition
and amount of gas produced during decom-
position of municipal solid wastes (MSW) is
essential to both understanding the pollu-
tion problem and exploiting a possible fuel
source.
Measurements of gas from decay of MSW
in sealed containers (1, 2, 3, 5, 9, 10)
have varied widely depending on the experi-
mental conditions under which the observa-
tions were made. Experimental parameters
which have affected gas production in MSW
landfill simulators include moisture con-
tent, type of MSW (baled, shredded, un-
processed, or synthetic) degree of compac-
tion, test cell size, and duration of
test. Dewalle, Chian, and Hammerberg
(1, 11) recently published a extensive
review of the effects of these experimen-
tal variables on gas production from MSW
and concluded that moisture and type of
MSW were the major controlling parameters.
The wide variability in published results
from previous experiments indicated the
need for a long-term, well-instrumented
landfill simulator experiment.
The work described in this paper is
intended to corroborate and add to pre-
vious determinations of gas production
and gas composition from MSW using an
improved gas monitoring methodology. Most
58
-------
investigators have relied on manometers
(10), wet test meters (1, 5), and Mariotte
flasks (1). One design of a sanitary land-
fill simulator proposed by Miller and
others (12) incorporated a linear mass flow-
meter with automatic flow integration and
flow rate recording. The gas monitoring
project described here parallels the pre-
vious work (1, 5, 6); but with more complete
instrumentation. Two sizes of lysimeters,
that are comparable in capacity to those
used by other researchers were included in
this investigation to allow a broad compari-
son of data obtained in this project with
that obtained in other experimental systems.
This paper describes a completely automated
gas monitoring system, and sanitary land-
fill simulators (lysimeters or test cells)
on which the system has been installed;
reviews the characteristics of the system's
performance to date and the first 100 days'
data; and presents a comparison of the
results obtained to published data from
similar systems.
MATERIALS AND METHODS
Lysimeter Construction
The lysimeters or simulators employed
in this study are cylindrical, steel (6.35
mm rolled plate) tanks with a coal-tar
epoxy coating on all interior surfaces. The
acid- and base-resistant, coal-tar epoxy
protects the lysimeter walls from corrosion
and the lysimeter contents from contamina-
tion. Two lysimeters (Numbers 10 and 22)
have dimensions of 0.91 m inside diameter
and 1.83 m height, and two (Numbers 15 and
16) have dimensions of 1.83 m inside dia-
meter and 3.66 m height. In the former,
0.91 x 1.22 m cells of compacted MSW were
placed on a soil layer that rests on a
layer of polypropylene beads, and in the
latter 1.83 x 2. A A m cells of compacted MSW
were placed on a soil layer that rests on
a layer of polypropylene beads (Figure 1).
Unbaled, unshredded MSW was placed in 30.5
cm lifts and compacted to approximately
400 kg (wet wt)/cu m density in the larger
lysimeters; smaller, randomly sized lifts
were compacted to an approximate density
of A05 kg (wet wt)/cu m in the smaller
lysimeters. The weights of MSW placed in
each lysimeter are given in Table 1. All
MSW was obtained from non-commercial
collection routes in Warren County, MS, in
April, 1978.
A 500-kg composite sample of MSW was
sorted at the time the lysimeters were
filled and the resulting percent composi-
tion of the MSW used in the study is given
in Table 2. Table 2 also presents composi-
tion data from other lysimeter studies.
After loading was completed on April
16, 1978, the lysimeters were sealed by
welding steel lids to the tops of the
lysimeters and by pumping metal sealant
(3M Weatherban 202) into a machined groove
(Figure 2) on the undersides of the lids.
The details of the loading procedure for
these four MSW lysimeters, the provisions
for rainfall simulation and leachate
collection and the temperature and baro-
metric pressure instrumentation are des-
cribed in a construction report (15).
Figure 3 is a photograph of the faci-
lity in which the lysimeters are housed.
The lysimeters stand in a pit, one end of
which can be seen in Figure 3. The pit,
1.5m deep, allows access to the top of
the tanks for servicing. The building is
temperature-controlled at 25 + 3°C.
Each lysimeter profile was construct-
ed to resemble a core of MSW taken from a
municipal landfill. The lysimeters simu-
late medium density cells in a sanitary
landfill in the humid eastern United States
containing unprocessed MSW. Infiltration
is simulated by applying 66 cm of deioni-
zed water per year (at a rate of 1.27 cm
per week). The initial moisture content
of the MSW was 21.92% (of the dry weight).
Gas Flow Measuring and Sampling System
The gas flow measuring and sampling
system consists of gas probes in each tank
that collect gas produced by the decaying
waste, a gas flow measuring and logging
device and a system that allows the extrac-
tion of an uncontaminated gas sample for
analysis. Figure A is a schematic diagram
of the system.
Gas Probes
Three gas probes were installed in
each lysimeter. Their locations within
the municipal solid waste profile for a
large lysimeter are shown in Figure 5.
Comparable locations were used in the small
lysimeters. Each gas probe (Figure 6)
consists of a perforated 0.6 cm copper
tube coated both inside and out with coal-
59
-------
7.6cm
DE IONIZED
WATER
POLYPROPYLENE
BEADS
Figure 1. Schematic diagram of the municipal solid waste lysimeters
TABLE 1. WEIGHTS OF MSW PLACED IN THE LYSIMETERS
Lysimeter
No.
10
15
16
22
Wet Wt.
(kg)
322
2555
2555
318
Dry Wt.
(kg)
264
2096
2096
261
60
-------
TABLE 2. PERCENT COMPOSITION OF MUNICIPAL SOLID WASTE
USED IN THIS AND OTHER INVESTIGATIONS
This Jackson &
Category Study Streng(13)
Paper 44.79* 40.53
Metal 10.82 8.29
Plastics,
rubber ,
leather 9.03 6.52
Glass 7.61 7.42
Textiles 3.08 4.19
Disposable
diapers 2.68 1.78
Food waste 0.94 7.53
Wood 0.49 0.86
Garden waste 0.41 15.32
Ash, rock,
dirt, fines 20.15 5.48
Chian Eifert &
and others (1) Swartzbaugh(14)
36.5 49.6
14.7 9.5
2.8 6.0
6.8 12.0
0.7 3.2
1.4
14.4 7.3
3.1 4.6
14.9 5.4
* All percentages are on a dry wt. basis.
1-4 IfWrm
In
•VXAAAAAAAA/W
S~
^~~~~^ \!\\
^.^LJ
^^^^a
LYSIMETER
••— WALL
NA/WWW\
— GREASE FITTING
.64cm STOCK
^ .16 MACHINED GROOVE
cm
Figure 2. Detail showing method of sealing
the tops of the lysimeters.
61
-------
Figure 3. Facility for housing landfill simulator project.
SStf^L.,- X'SSSFS/SW1TCH I LOSf*
Shut oft vol»»
Sol.nocd nJvi
Figure 4. Schematic diagram of gas flow
measurement and sampling system.
GP = Gas Collection Probe
62
-------
GAS LINES
IAP 19cm ^ 0 64cm t|NSERT V, 9em \G4 <(
COWUMI MMIEUX
Figure 6. Detail of construction
of gas collection probes
Figure 5. Position of gas collection
probes in the large lysimeters
tar epoxy to prevent corrosion by leachate.
The copper tubing was fitted into a per-
forated 1.9 cm PVC pipe to protect the
tubing during compaction of the waste.
Each gas probe was connected to a gas
collection line using a union after the
underlying municipal solid waste had been
placed and compacted. An epoxy-sealed
rubber insert in the PVC pipe upstream from
the union prevents leachate contact with
and corrosion of the union and attached
copper gas lines. A 1.9 cm PVC pipe
attached to the inside wall of the steel
tank covers the gas lines as they run up
the wall and out of the solid waste. The
copper gas collection lines pass through
the tank wall at a point just below the
top of the lysimeter. At the exits, the
lines were brazed to the exterior of the
lysimeters. The PVC pipe and copper gas
lines extending up the insides of the cells
were attached in such a way so as to allow
for compaction and consolidation of the
municipal solid waste
during the course of the experiment.
Gas Flow Measuring System
The gas flow measuring system operates
on a pressure-controlled flow principle.
Internal cell pressure is maintained at a
pressure slightly above atmospheric by
controlled out-gassing of the lysimeters.
Gas flow is measured by a linear mass
flowtneter. The internal tank pressure is
normally allowed to reach a pressure of 4
cm water column (WC), with respect to
external air pressure; then gas is bled
off through the gas flowmeter until
pressure is reduced to a low set point
(usually 2 cm WC). The components of the
gas flow measuring system for each cell
are as follows: one differential pressure
switch/gauge, three solenoid valves
(normally closed), one linear mass gas
flowmeter, one controller, seven shut-off
valves, and one pressure gauge. A data
logger (Martek DLS) records gas production
data from all four lysimeters.
The differential pressure switch/
gauge incorporates gauge and switch set
point indicators for continuous indication
of internal pressure and switch settings.
These units are diaphragm-operated with
switching accomplished by photocell-
controlled relays. Set points are adjusta-
ble over a range of 0-5 cm WC. The unit
can be regulated to 0.1 cm WC. The
pressure switch/gauge is used to operate
two normally-closed solenoid valves. When
the pressure reaches the high set point
(4 cm WC) the two solenoid valves open and
the gas from the lysimeter passes through
the flowmeter. When the pressure drops to
the low set point (2 cm WC) the solenoid
valves close. A pressure gauge (no
switching capability) has been installed
63
-------
so that periodic checks can be made on the
pressure switch/gauge's performance. The
pressure switch/gauge is a Dywer Photo-
helic Model 3000-5-CM and the auxiliary
pressure gauge is a Dywer Magnehelic Model
2015.
The linear mass flowmeter consists of
an electrically-heated tube and an arrange-
ment of thermocouples which measure
differential cooling caused by the gas
passing through the tube. Thermoelectric
elements generate DC voltages which are
directly proportional to the rate of mass
flow of gas through the tube. This pro-
portionality permits the linear mass flow-
meter calibrated for one gas to be used
to measure the flow of a mixture of gases,
such as landfill gas, if the gas composi-
tion and the thermal conductivity of the
component gases are known. The mass flow-
meter signal is insensitive to ambient
pressure and temperature changes. These
mass flowmeters because of their linear
signal are ideal for use with totalizers
and automatic data reduction equipment.
The flowmeter, at its maximum flow rate
(1 liter/min), generates a 5 VDC output.
The flowmeters are Matheson Model 8116-0113
with Model H-1K transducers. The manu-
facturer's calibration was checked by
comparing the recorded flow through each
flowmeter with a reference flow standard
(RFS). Where units varied more than +0.5%
from the RFS, they were recalibrated
according to the manufacturer's instruction.
Three normally-closed solenoid valves
downstream of the linear mass flowmeter open
and close the gas lines. The valves are
energized by a controller accepting input
from the pressure switch/gauge and the mass
flowmeter. Additional manually-operated
shut-off and switching valves can be used
to selectively sample different locations
in the lysimeters and to close off the gas
flow from the lysimeters in the event main-
tenance is required.
The controller, a solid state logic box,
operates the solenoid valves as follows:
(1) When pressure reaches the high set
point on the pressure switch/gauge, solenoid
valves Nos. 1 and 2 (Figure 4) open and gas
moves out of the lysimeter through the
flowmeter.
(2) When and if the flow rate reaches
95% of the measuring capacity of the flow-
meter, solenoid No. 2 closes to keep the
gas
rate in a measurable range.
(3) When the flow rate drops to 20%
of the capacity of the flowmeter, solenoid
No. 2 reopens. Steps (2) and (3) prevent
gas flow rates from overranging the flow-
meter.
(4) Solenoids 1 and 2 are activated
until the pressure drops to the low set
point of the pressure/switch gauge; both
solenoids then close.
Analog signals from the linear mass
flowmeter are digitalized through a voltage-
to-frequency conversion and then accumula-
ted in an electronic counter. Totals from
the electronic counters (totalizers) are
recorded on cassette tape at hourly inter-
vals by a 56-channel, Martek DLS data
logger. The counter registers are returned
to zero after each hourly update. With
each update the data logger also records
day, hour (from an internal clock), temp-
eratures from three thermistor locations
in the large lysimeters and from one
thermistor location in each of the two
small lysimeters (Figure 1) , barometric
pressure, ambient air temperature from
two locations in the lysimeter facility,
and reference voltages for the electronics
associated with temperature measurement.
All recorded data are identified according
to day and hour.
Gas Sample Collection
Two different sampling methods were
tested during the first 18 days of lysi-
meter operation, one system used Tedlar
bags, the other did not require Tedlar
bags. Initially gas samples were com-
posited into Tedlar gas bags and sampled
for analysis using glass gas bulbs filled
using a diaphram pump. This initial
sampling configuration is shown in Figure
7a. Gases were composited in the Tedlar
bags using a flow proportional sampling
system operated by the electronic flow
controller. Fo'r every 90 milliliters
of gas registered on the flow counters,
the controller closed solenoid No. 2
(Figure 4) directing 10 milliliters through
solenoid No. 3 into a Tedlar bag. Tedlar
bags of 2-mil thickness and 48-liter
capacity were used. The glass gas bulbs
are cylinders with 0-ring (neoprene)
sealed glass plungers that act as valves
on each end. Tygon tubing was used as gas
line from the Tedlar bags to the glass
64
-------
Figure 7. Diagram showing sampling
systems used with MSW
lysimeter gases.
System shown in 7a uses a
Tedlar bag to composite sample.
System shown in 7b collects
a "grab sample" through the
gas monitoring system.
cylinders and from the glass cylinders to
a diaphragm pump. The Tedlar bags were
attached to the gas measuring system (CMS)
so that the bags would be filled with gas
composited over a given sample interval.
However, with this system, the expected
oxygen depletion in the gas samples was not
observed. The lysimeters including all
fittings were checked for leaks with a gas
leak detector (Gow-Mac Model 21-200) and no
leaks were found. Excellent replication of
gas analyses run after samples had been
stored varying lengths of time (up to four
hours) in the gas bulbs showed that the gas
bulbs were not leaking. Gas samples were
taken directly from a lysimeter at the
branch in the CMS for direct sampling of
the lysimeters (Figure 4) and at the same
time from the Tedlar gas bag. The sample
directly from the lysimeter was an order of
magnitude lower in oxygen than the Tedlar
bag sample. As a check for leaks, the Ted-
lar bag was filled with helium. Comparison
of analyses of the bag's gas composition
immediately after filling and 24 hours
after filling showed a two-fold increase
in oxygen content. Leakage could be due to
permeation through the polymer material or
to physical breaks in the bags. Suppliers
caution that the Tedlar bags are very deli-
cate and are easily damaged. By migrating
through microvoids in the polymer's struc-
ture, gas molecules can permeate the Tedlar
(16). Recently Polasek and Bullin (17)
have reported that Tedlar bags were unsatis-
factory for ambient air sampling. The com-
bination of theoretical considerations and
practical experience led to development of
a system eliminating Tedlar bags.
As an alternative to the Tedlar bag
composite sample, grab samples were
collected from the lysimeters through the
CMS in glass gas bulbs in the same bulb-
pump procedure used before (Figure 7a)
except that the Tedlar bag had been removed.
Shortly after the change to grab samples
had been made, the 0-rings on the gas bulbs
began to leak. To overcome these initial
sampling problems an all-metal system using
a compressor and steel storage tank was
developed.
A small vacuum pump/compressor and a
stainless steel gas cylinder is now used
in the sampling configuration shown in
Figure 7b. Copper tubing is used for gas
lines from the CMS to the sample cylinder.
Stainless steel quick-disconnects with
double-end, shut-offs are employed through-
out the system in order to prevent contami-
nation during connection and disconnection
of gas lines. The sample cylinder (Mathe-
son, stainless steel, 150 m& capacity) is
purged by pumping lysimeter gas through
the cylinder. One end of the cylinder is
then shut off, and lysimeter gas is pumped
into the cylinder to a pressure of 2.9 kg/
cm2. The compressor is a KNF Neuberger,
Inc., Model N04 STI diaphragm (Teflon)
vacuum pump/compressor. This unit offers
oil-free operation and contaminant-free
pumping in a unit of relatively small size.
Since the all-metal sample collection was
initiated, the oxygen levels have been at
or below detection limits (<0.1%) and the
remaining components of the samples have
been within expected ranges.
Gas Analysis
Gas samples are analyzed on a Perkin-
Elmer Sigma 3 gas chromatograph (GC) for
oxygen, hydrogen, nitrogen, carbon dioxide,
methane and water vapor. The separation
and quantification of these gases is per-
formed on a 274 x 3.2 mm Carbosieve S
column; the column temperature is program-
med from 30°C to 175°C; helium carries the
sample stream to a thermal conductivity
detector. The GC is used with a Perkin-
Elmer 056 recorder and an electronic peak
integrator. The GC is calibrated with
commercially prepared gas mixtures, and
the results are reported in volume percent.
The analytical technique used in this in-
vestigation does not separate oxygen and
argon. Very low residual oxygen levels
observed in the landfill gas are do to
traces of argon in the gas samples.
65
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DATA REDUCTION AND PRESENTATION
The system for data reduction and pre-
sentation is shown in Figure 8. The raw
data tapes from the logger are read by a
Martek Model 421-DRS magnetic tape reader
and printed on a Anadex Model DP-500-9
paper tape printer. Another Martex Model
421-DRS magnetic tape reader is used to
transfer data from the magnetic tape to a
Hewlett-Packard Model 9830A computer
through a Martek Model 421-12 DRS computer
interfacing unit. The data fed from the
Martek tapes to the HP 9830A is immediately
printed on a Hewlett Packard Model 9866A
printer at which time the data is verified
by comparison with the printout from the
Anadex unit. After verification, the data
are reorganized and stored in raw form on
magnetic tapes in an array that allows for
easy access and manipulation by the com-
puter. The tape files, each of which con-
tains one update, are stored sequentially
with the tape number and file number of the
individual updates being recorded in a log
book. As the raw data tapes become avai-
lable, the raw data are reduced to engi-
neering units by the computer using equa-
tions that correct for non-linear output
from thermistors and barometric pressure
sensors and for variation in gas composi-
tion. The reduced data for a whole day
are stored on a new tape file along with
the cummulative gas production for the day.
In this manner, the computer builds a tape
file library for each lysimeter containing
all the reduced data for each day in a
separate tape file to facilitate
retrieval. The raw data tapes are pre-
served as originally generated.
After storing the data on the proper
tape file, the computer prints a data
table for that day. The table contains
the lysimeter number, the day; and for
each update during the day, the time of
the update and all the reduced data (gas
production, temperatures, and barometric
pressure).
A computer program was developed to
plot the reduced data on a Hewlett-Packard
Model 9862A plotter. The computer reads
the data off of the reduced data tape file
for the lysimeter of interest. The com-
puter produces a plot of time versus gas
production, temperature, and barometric
pressure (all on the same plot) for a
particular lysimeter and a particular day
as specified by the user.
Another program was developed to
plot daily cumulative gas production over
a period of time. The computer inputs the
daily cumulative gas production and the
day from the reduced data tape file for
the lysimeter of interest and plots pro-
duction versus day for the period of time
specified.
The computer can be programmed to
perform other data manipulations as needed
obtaining the data from the reduced data
tape file for each lysimeter. The system
is structured so that new data can be
continually added while data reduction and
manipulation continues. This system
handles a large amount of data in a short
time and at a very low cost. Such a data
handling and storage task would be prohibi-
tively expensive without the use of such a
system.
H
A KDUCTIOM
TNI HP-MKM WILL KCWHITI TK Mm
MO MMCt WM*UTMM,IIUNS, HI8MI,
LOM, ETC
Figure 8. Diagram showing system for
handling data from MSW
lysimeters,
RESULTS AND DISCUSSION
Quantity of Gas Produced
The total gas production for the
landfill simulators for the initial 100
days is given in Table 3. The average
value is 61.8 ml per kilogram (dry wt.)
per day. The maximum value for gas pro-
duction for the study is 69.5 mil per
kilogram (dry wt) per day. Both the
average and maximum rates are within the
range reported for similar experiments
(11, 2, 5). The production rates are
higher than rates calculated for actual
landfills (22-45 ml/kg/day)(11). It
should be noted that these data are only
66
-------
TABLE 3. SUMMARY OF GAS PRODUCTION FOR THE FIRST 100 DAYS
Lysimeter
10
Dry wt.
MSW
(kg)
264
Total
Gas
Production
(liters)
1335
(1506)*
Average Daily Gas
Production
(m£/kg (dw) • day)
(57.0)
15
16
22
2096
2096
261
13991
14559
1401
Average
66.8
69.5
53.8
61.8
* Failure of totalizer resulted in 10 days' loss of data. Value in parentheses is a
projected gas production figure based on production before and after breakdown.
100 days' record and include the initial
rapid C02 production associated with the
beginning of decomposition.
A review of the literature indicates
that a great deal of variability is to be
expected in gas production data. Most
systems would underestimate gas production
due to leakage or equipment malfunction (11).
There is also an inherent variability that
is related to the composition of the refuse
material in the simulator. Ramaswamy (9)
demonstrated that the proportion of food
scraps (or material added to act of food
scraps) in the solid waste has significant
effect of the volume of gas produced.
Figures 9 and 10 show two typical gas
production curves over a 24-hour period for
Lysimeter 15. These were selected to show
how temperature and barometric pressure
changes affect movement of gas out of a
tank over the course of a day. The effect
of temperature is especially obvious in
Figure 10, where the gas flow can be shown
to increase as the temperature increases
in the building and in the headspace at
the top of the simulator.
Figures 11-14 show gas production over
a 100-day period for the lysimeters. The
production fluctuates widely, reflecting
changes in pressure differential caused by
variations in temperature, barometric
pressure, and microbial activity. The
major feature in this data is an overall
decline in gas production as the refuse
stabilizes.. Changes in production rate
may occur when the lysimeters move into
methane generation.
In general, the gas production rates
reported here are within the range of
rates observed by other researchers. The
average rates are higher than the majority
of landfill simulator gas production rates,
perhaps reflecting an increased accuracy
in the gas flow determination from the
automated flow measuring system. The
overall pattern of declining gas produc-
tion matches the trend observed by other
researchers; an initial gas surge that
tapers off to a lower, more nearly cons-
tant production rate.
Gas Composition
Changes in the composition of the
gas samples obtained from the lysimeters
are shown in Figures 15-18. The oxygen
level in all four lysimeters declined
very rapidly after the tanks were sealed.
All four of the tanks were sampled within
24 hours of sealing and the apparent
oxygen (oxygen plus argon) had dropped to
below 1.0%. The percent C02 shows a
general increase in all four tanks. Nitro-
gen levels show an overall decline due to
the sweeping of the tank by C02 generated
by microbial metabolism. No hydrogen or
methane was detected in any of the gas
samples for the period reported here.
67
-------
H0T
30--
LY5 ND. 15
DRY IB
MIDDLE THERMISTOR
--7B
u
7S*
ffi
u
n:
0.
a:
n:
ta
--7H
9 12
TIME CHOURS)
-"-73
Figure 9. Plot showing variations in temperature, barometric pressure,
and gas flow for day 18.
H0T LY5 NO. IS
DRY B0
30-•
T3S T77
BAROMETRIC
LOWER PRESSURE
/THERMISTOR
TOP THERMISTOR
--3B
--7B
5
%X
Ul
at
a.
•-7H
9 12
TIME CHDUR5)
Figure 10. Plot showing variations in temperature, barometric pressure,
and gas flow for day 80.
68
-------
60 T
LY5 ND. IB
Figure 11. Plot showing variation in gas flow for lysimeter 10 for first 100 days.
600T LY5 ND. IS
Figure 12. Plot showing variation in gas flow for lysimeter 15 for first 100 days.
69
-------
G00T
500--
H00--
U1
K
W
Ul
IE
in
200--
100- •
LY5 NO. IB
20
H0 E0
DRY
100
Figure 13. Plot showing variation in gas flow for lysimeter 16 for first 100 days.
B0T
LY5 NO. 22
100
Figure 1A. Plot showing variation in gas flow for lysimeter 22 for first 100 days.
70
-------
Figure 15. Plot showing variation in
gas composition in lysimeter
10 for first 100 days.
Figure 16. Plot showing variation in gas
composition in lysimeter 15 for
first 100 days.
Figure 17. Plot showing variation in gas
composition in lysimeter 16
for first 100 days.
C02
H,
OjtA,
Figure 18. Plot showing variation in gas
composition in lysimeter 22
for first 100 days.
The variation in gas composition ob-
served in this investigation differs
significantly from the ideal model pro-
posed by Farquhar and Rovers (2). They
proposed a gas production pattern with
four distinct phases. The first phase
involved nitrogen purging and oxygen dep-
letion. The second phase involved in-
creased hydrogen and carbon dioxide pro-
duction. The third phase was charac-
terized by a start-up of methane genera-
tion and a slight decrease and leveling-
off of carbon dioxide evolution. The last
phase involved development of a constant
level of carbon dioxide and methane pro-
duction. The aerobic decomposition in
this study (Phase I) lasted only a very
short time (<2A hours). The first measure-
ments taken showed negligible oxygen
levels. No hydrogen production (Phase II)
or methane production (Phase III) was
detected during the period reported here.
The results observed in the tanks
used in this experiment approach closely
those observed in other large tanks con-
taining unshredded refuse. Merz and Stone
(3) reported no significant gas production
in large containers until 250 days into
their experiment and no significant quan-
tity of methane in the gas eventually
generated. Rovers and Farquhar (10) ob-
served a 50-day lag in gas production
in the single sealed tank they used and
no significant quantity of methane was
recorded until 248 days had elapsed. Con-
tainer sizes, temperature, moisture con-
tent, the character of refuse, degree of
compaction, and the use of shredded as
opposed to unshredded refuse, all appear
to affect the composition of gas generated
during stabilization. Other unmeasured
or unmeasurable factors such as changing
71
-------
character of microbial populations and the
availability of micronutrients probably
affect the major stabilization processes
and the types of decay gases produced at
any particular time in any particular
experimental setup.
While it is not possible to indicate
why hydrogen and methane are absent in the
gas samples coming from the landfill simu-
lator, some obvious factors can be ruled out.
Gas measurements have shown consistent, very
low levels of apparent oxygen, indicating
this should be no inhibitory factor. It
has been proposed that water could carry
oxygen into the lysimeters. Water has been
added to the simulators at a rate equal to
1.27 cm of infiltration per week; but
this small quantity of water could only
contribute oxygen equal to 0.004% of the
gas void available in the simulator. A
small amount of 02 introduced this way
probably affects only the bacteria in the
upper few centimeters of the simulator.
Gas probes placed in the headspace of the
tank, where any Q^ introduced should
appear, showed no detectable differences
in composition when compared to probes in
the center or bottom of the tank.
The tanks have been maintained in a
constant temperature facility within the
range at which other experimenters have
observed hydrogen and/or methane production.
There is no indication of inhibitory temp-
erature effects.
The refuse in the tank has not been
shredded or compacted more than refuse
placed in other experimental simulators.
The excessive compaction and shredding
have been indicated as inhibiting methane
production (11).
The refuse in the tank has been in-
creasing in moisture content. Simulated
infiltration was provided at regular inter-
vals so moisture fronts should have moved
through the refuse, with successively more
refuse becoming saturated. Thus, while the
tank has not been totally saturated, parts
of the refuse pile may have reached an
optimum moisture content for methane pro-
duction during the study. However, in-situ
moisture measurements would be required
to prove that suitable moisture regimes for
methane production do exist.
As additional data on leachate pH,
nutrient levels and organic substrates are
collected, reasons for the particular gas
composition observed in this study may
become clearer. It appears that the simu-
lators in this experiment will all reach
field capacity before sigificant methane
or hydrogen production is observed.
Changes in the character of the leachate
that can be correlated with the production
of methane or hydrogen may provide informa-
tion on what factors control methane or
hydrogen generation in this experiment.
SUMMARY AND CONCLUSIONS
The first 100 days of data have been
collected on gas production from four
landfill simulators. An automated gas
measuring system developed for the simu-
lators is functioning satisfactorily. The.
system incorporates an electronic digital
recording device that interfaces with a
small cotnputer to produce data listings
and plots of data variation.
The average gas flow rates observed
in the experiment are consistent with
experimental values available in the litera-
ture. The average gas generation rates
observed here are higher than field measure-
ments of gas production at actual landfills.
The pattern of declining gas production
matches the trend observed by other
researchers.
Gas composition is being determined
at regular intervals using a gas chroma-
tographic technique. An all-metal gas
sampling system has been developed in order
to obtain uncontaminated gas samples.
Analyses available to date indicate that
carbon dioxide is the product gas being
generated in the lysimeters. These results
are consistent with data available in the
literature from several previous experi-
ments .
ACKNOWLEDGEMENT S
This study is part of a major research
program on solid and hazardous waste dis-
posal, which is now being conducted by the
U. S. Army Engineer, Waterways Experiment
Station and funded by the U. S. Environ-
mental Protection Agency, Municipal En-
vironmental Research Laboratory, Solid
and Hazardous Waste Research Division,
Cincinnati, Ohio, under Interagency Agree-
ment EPA-IAG-D4-0569. Robert E. Landreth
72
-------
is the EPA Program Manager for this
research.
REFERENCES
Ramaswamy, J. N., "Nutritional Effects
on Acid and Gas Production in Sani-
tary Landfills." PhD. Thesis, West
Virginia University, Morgantown, WV.
1970.
1. Chian, E. S. K., DeWalle, F. B. and
Hammerbert, E. "Effect of Moisture
Regime and Other Factors on Municipal
Solid Waste Stabilization," p. 73-86,
in Banerji, S. K. (ed.), "Management
of Gas Leachate in Landfills," EPA-
600/9-77-026, U. S. Environmental Pro-
tection Agency, Cincinnati, OH, 1977.
2. Farquhar, G. J. and Rovers, F. A. "Gas
Production during Refuse Decomposition,"
Water. Air, and Soil Pollution. 2(1):
483, 1973.
3. Merz, R. C. and Stone, R. "Special
Studies of a Sanitary Landfill," Uni-
ted States Public Health Service, Bur-
eau of Solid Waste Management. U. S.
Environmental Protection Agency Publ.
EPA-SW-8R6-70, 1968.
4. Fungaroli, A. A. "Pollution of Sub-
surface Water by Sanitary Landfills."
vol. 1, EP-000 162 U. S. Environmental
Protection Agency, Washington, D.C.
1971.
5. Streng, D. R. "The Effects of Indust-
rial Sludges on Landfill Leachate in
Landfills," EPA-600/9-77-026, U. S.
Environmental Protection Agency, Cin-
cinnati, OH. 1977.
6. Swartzbaugh, J. T., Hentrich, R. L.,
Jr., and Sabel, G. V. "Co-Disposal of
Industrial and Municipal Wastes in a
Landfill." p. 129-152 in Shultz, D. W.
(ed.) "Land Disposal of Hazardous
Wastes," EPA-600/9-78-016 U. S. Envi-
ronmental Protection Agency, Cincinnati,
OH. 1977.
7. Carlson, J. A., "Recovery of Landfill
Gas at Mountain View." SW-587d U. S.
Environmental Protection Agency, Cin-
cinnati, OH. 1977.
8. Colonna, R. A. "Methane Gas Recovery
at Mountain View Moves into Second
Phase," Solid Waste Management 19(5):
90, 1976.
10. Rovers, F. A. and Farquhar, G. J.
"Infiltration and Landfill Behavior."
Jour. Environ. Engr. Division, Amer.
Soc. Civil Engr. 99(EE5): 671. 1973.
11. DeWalle, F. B., Chian, E. S. K., and
Hammerberg, E. "Gas Production from
Solid Wastes in Landfills," Jour.
Environ. Engr. Division, Amer. Soc.
Civil Engr. 104(EE3): 415-432, 1978.
12. Miller, W. V., Ward, C. J., Boeltcher,
Boeltcher, R. A., and Clarke, N. P.
"Sanitary Landfill Simulation - Test
Parameters and a Simulator Conceptual
Design." Tech. Note N-1451. Civil
Engineering Laboratory, U. S. Naval
Construction Battalion Ctr., Port
Heuneme, CA. 1976.
13. Jackson, A. G. and Streng, D. R. "Gas
and Leachate Generation in Various
Solid Waste Environments." in "Gas
and Leachate from Landfills: Formation
Collection, and Treatment." EPA 600/
9-76-004, U. S. Environmental Protection
Agency, Cincinnati, OH. 1976.
14. Eifert, M. C. and Swartzbaugh, J. T.
"Influence of Municipal Solid Wastes
Processing on Gas and Leachate Genera-
tion." p. 55-72 in Banerji, S. K. (ed.)
"Management of Gas and Leachate in
Landfills." EPA-600/9-77-026, U. S.
Environmental Protection Agency, Cin-
cinnati, OH. 1977.
15. Myers, T. E., Malone, P. G., and Duke,
J. C. "The Effect of Raw and Treated
Sludge on Leachate Quality in Land-
fill Environments and Gas Production
Rates and Compositions in a Sanitary
Landfill Environment: Construction
Report." USAE Waterways Experiment
Station, Vicksburg, MS. Draft in pre-
paration.
16. E. I. Dupont de Nemours. "Reviewing
the Chemical Properties of 'Teflon1
Resins." Jour. Teflon 5:19, 1964.
17. Polasek, J. C. and Bullin, J. A.
"Evaluation of Bag Sequential Sampling
Techniques for Ambient Air Analysis."
Environ. Sci. and Tech. 12:6. 1978.
73
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LEACHATE PRODUCTION FROM LANDFILLED MUNICIPAL WASTE
BOONE COUNTY FIELD SITE
Richard J. Wigh
Regional Services Corporation
Columbus, Indiana
Dirk R. Brunner
USEPA
Cincinnati, Ohio
ABSTRACT
Five municipal waste test cells were constructed at the Boone County Field Site
during 1971 and 1972. Two were field-scale and three were small-scale cells constructed
for the purpose of performance comparison. All cells have been monitored for temperature,
gas composition,settlement, and leachate quantity and characteristics. This paper pre-
sents interim results from the analysis of over four years of the leachate quantity and
quality data. It must be emphasized that the results are from relatively shallow (less
than 2.5 meters) batch-type cells.
INTRODUCTION
The Boone County Field Site consists
of a ten acre tract located 8 km west of
the City of Walton, Kentucky. Available
facilities at the site include an office
trailer, a pole barn, and a truck scale.
An instrumentation shed has been placed
near the test cell and a weather station
has been erected at the site.
Elevations at the research site range
between 213 and 244 m above sea level.
Surficial soils at the site are predomin-
antly a lean clay, classified by USDA as
Nicholson silt loam. Rubbly limestone
mixed with thin beds of soft calcareous
shades of the Fairview formation underlie
the shallow soil. The mean annual pre-
cipitation in the area is 927 mm. Monthly
normal mean temperatures range from 0 deg.
C in January to 24.4 deg.C. in July.
The objectives of test cells 1, 2A,
2B, 2C, and 2D included:
(1) Analyze the amount and character-
istics of leachate.
(2) Analyze the composition of gases
present in the cells.
(3) Evaluate a clayey-silt soil as an
impervious liner for leachate control.
(4) Evaluate the behavior of a field-
scale test cell, 2D, as compared to simi-
larly constructed small-scale test cells,
2A, 2B, and 2C.
TEST CELL DESCRIPTION
Test Cell 1 consisted of a 45.4 m long
by 9.2 m wide trench type sanitary landfill
cell. The trench was excavated with verti-
cal side walls and ramps on both ends slop-
ing approximately 1:7. The center 15.3 m
of the trench was sloped approximately 7
percent to the transverse center line as
shown in Figure 1. A 30 mil (.76 mm) syn-
thetic liner (Hypalon) was centered in the
base of the cell to prevent any leachate
from migrating below the cell. Directly
above the liner a slotted collection pipe
was installed along the transverse center
74
-------
line. Above this pipe and the synthetic
liner a 45.7 cm thick clayey-silt soil
liner was placed.
A second slotted collection pipe was
installed in a trench in the soil liner.
Short-circuiting to the lower pipe was
prevented by lining the base and sides of
the trench with a polyethylene strip. Both
pipes drained into the observation unit be-
side the cell. The area around both pipes
was backfilled with clean silica gravel.
Details of the drainage scheme are shown
in Figure 2.
During June 1971, 395 metric tons of
residential refuse was placed in the test
cell at a dry density of 429 kg/cubic
meter. Moisture, temperature, gas and
settlement probes were placed within the
cell as it was constructed. Approximately
.6 m of the compacted clayey-silt (CL)
soil was placed over the refuse.
Four additional test cells containing
municipal solid waste were constructed
during August 1972. Three of the cells,
2A, 2B, and 2C were enclosed in identical
cylindrical steel pipes, 1.83 m in dia-
meter and 3.66 m long. The fourth test
cell, 2D, was an 8.53 m square field-scale
cell constructed to compare performance
with the small-scale cells.
The steel pipes were coated with cold
tar epoxy and placed vertically in an ex-
cavation on reinforced concrete pads.
Slotted pipe in a trough in the concrete
pad was used to collect leachate. Earth
backfill was placed around the pipes to
within 150 mm of the tops. Refuse was
placed in the pipes in 90-135 Kg increments
and compacted by dropping a 135 Kg weight
from a height of approximately 1.2 m above
the refuse. Temperature and gas probes
were placed at several levels within the
cell during refuse placement. 300 mm of
compacted soil was placed above the refuse
and then 300 mm of pea gravel to allow
rapid percolation of rainfall and to mini-
mize evaporation.
Cell 2D was constructed in an excava-
tion 8.53 m square and 3.20 m deep. A 30
mil CPE liner was placed above a shaped
sand bed in the base of the cell and ex-
tending up the sidewalls. A slotted PVC
pipe was placed along the center line of
the base of the cell for leachate collec-
tion and gravity drainage to the collection
well. The entire base of the cell and
liner was covered with 300 mm of silica
sand. Plywood sheets were placed against
the synthetic liner on the sidewalls for
protection from puncture and tearing during
cell filling. Construction details are
shown in Figure 3.
A small bulldozer was lowered into
the cell by a crane for compaction of
refuse. Temperature and gas probes were
placed during the filling at locations
shown in Figure 3. A 300 mm layer of com-
pacted soil cover was placed over the 2.44
m of refuse. A berm system, consisting of
150 mm high triangular-shaped clay berms,
was hand constructed on top of the soil
cover. This was constructed to promote
uniform percolation of rainfall into the
refuse cell.
Samples were obtained from the resi-
dential refuse being placed in all cells
for moisture and composition studies.
Chemical analysis of the refuse was done
for a number of parameters for Test Cell 1.
Statistical analysis indicated that any
performance variations within cells 2A,2B
and 2C could not be attributed to the dif-
ferences in the composition or the original
moisture. A summary of the cell data is
shown in Table 1.
LEACHATE QUANTITY
TEST CELL 1
Leachate was initially collected from
both the upper and lower pipes in Test Cell
1 approximately two months after construct-
ion. Cumulative leachate volume is shown
in Figure 4 together with the volume of
leachate predicted by using the water bal-
ance method. Leachate collected was 32%
of the precipitation after 4.5 years.
In computing the water balance it was
assumed that the monthly mean temperatures
for the Boone County site were the same as
that reported for Covington, Kentucky. The
runoff co-efficients for the wet and dry
seasons were chosen as .17 and .13. Assum-
ing a soil moisture storage capacity of 125
mm for the final cover, 90 mm of water were
required to bring the final soil cover to
field capacity. An additional 106,000 lit-
ers of water were required to bring the
entire cell and the soil liner to field
capacity based on an estimated refuse field
capacity of 330 mm/m of refuse.
75
-------
_L
aservation Unit p | 5'
II f
II-—--
II
50'
Leachate
Collection Pipes
149'
30'
PLAN VIEW
32?
Refuse
'"*!
| Edge of
-*j/6ulkhead
6 mil_
Plastic Liner I
2" Soil Cover
>
Compacted Solid Waste
18" Clay
30 Mil. Synthetic Liner
aachate (See Figure 3)
Pipes
LONGITUDINAL SECTION
Observation Unit —i
Soil
Cover
0.5%
f^ 30
8W08V.
1
Leachate Pipes
TRANSVERSE SECTION
I
4 Drain Pipe
30 Mil. Synthetic Liner —'
LONGITUDINAL VIEW OF COLLECTIQM SYSTEM
/Silica
Gravel
-6 mil Plastic Liner
. 18"
ne* 30 mil
^ynthetic Liner
8.8% Slope 8.8% Slope
SECTION A-A
Figure 2. Leachate Collection System.
Figure 1. Design of Cell No. 1
-------
0.51
LONGITUDINAL PROFILE ALONG LEACHATE COLLECTION PIPE
3.0'
3.0'
GRAVEL
CLAY
O O A
9.0'
A O
7.0'
-*
O a
^ J
7.0'TTo1
REFUSE
30 MIL C.P.E. LINER
O A o
28.0'
','1.0'
8.0'
0.7'
0.5'
SVERSE PROFILE AT EFFLUENT END OF LEACHATE COLLECTION PIP]
GRAVEL
CLAY
OA LEVEL 1
14.0'
0 LEVEL 4
REFUSE
OA LEVEL 7
3" P.V.C. PIPE \ /30 MIL C.P.E. LINER
"™" — _ A • J * x> Q A WT\ / * A • J *
~~ ~ — - ••— —»5te ^^ OAWJJ / ^..__ ^^ _ — i— !• —
28.0'
^- ^
' 1
~Ti.c
~fi.(
H~:
t
0,Qf
1 1
1 f
8.0'
i
1" - 25.4 mm
1' - 0.3 m
O TEMPERATURE
A GAS
Figure 3. Construction details for cell 2D.
77
-------
TABLE 1
SUMMARY OF CELL DATA
Cover soil classification
Depth of soil cover, m
o
Surface area of refuse, m
Depth of refuse, m
Mass of refuse, kg (wet)
Wet density of refuse, kg/m
2A
CL
.30
2.627
2.56
2640
392.6
Test
2B
CL
.30
2.627
2.56
2898
430.9
Cell
2C
CL
.30
2.627
2.56
2814
418.4
2D
CL
.30
72.83
2.44
106,231
597.8
Moisture content of refuse,
% wet weight
22.5
27.1
24.1
31.8
The water balance calculations were
reasonably accurate in predicting the
quantity of leachate, with only a 12.7%
difference after 4.5 years. If average
evapotranspiration values had been used,
rather than ones computed from the actual
climatic conditions experienced, the dif-
ference would have been 35%. This large
difference indicates a need for leachate
volume calculations in designs to be based
on extreme weather conditions as well as
average values.
SOIL LINER
The quantity of leachate collected
from both the upper and lower pipes and
the amount of precipitation is listed in
Table 2. The quantity of leachate from
the lower pipe was equal to or greater
than that volume from the upper pipe until
January, 1972. This was caused by leaving
the valve closed on the upper pipe except
for weekly sampling, thereby inducing suf-
ficient head to cause leakage into the
lower pipe. After December 20, 1971, the
upper pipe was allowed to drain freely
through an S-trap into a sump in the ob-
servation unit, thereby greatly reducing
the hydraulic head and consequently reduc-
ing the flow from the lower pipe.
The percentage for the leachate col-
lected from the lower pipe has decreased
over the years due to the change in col-
lection method, and/or a decrease in per-
meability of the soil liner, to a point
where more than 99% of the leachate is
collected from the upper pipe. This in-
dicates that the soil liner, maintained
under a free flowing condition, is pre-
venting virtually any of the leachate from
migrating to the lower pipe.
From Table 2 a tendency can be noted
that a greater percentage of the total flow
comes from the lower pipe during the months
of low total flow. For example, during
1974, 50% of the flow in the lower pipe
occurred during six months when only 17%
of the total flow occurred. Apparently
during periods of high total flow, the soil
liner becomes saturated, and with a higher
permeability existing at the refuse-soil
interface the leachate flows principally
to the upper pipe. During periods of low
total flow, the soil liner is not fully
saturated, allowing percolation down to the
liner and lower pipe in a larger percentage
than when the soil is fully saturated. It
is possible that the synthetic liner and
the soil liner are functioning together and
that the large quantity collected in the
upper pipe is not due to the soil alone.
It appears that the synthetic liner is
responsible for at least some portion of
the flow to the upper pipe by not allowing
any deep percolation and by keeping the
soil liner in a saturated condition for a
longer time than if downward percolation
were allowed.
78
-------
TABLE 2. SEASONAL DISTRIBUTION OF COLLECTED LEACHATE
Months
June -Aug .
Sept. -Nov.
Dec . -Feb .
Mar. -May
June -Aug.
Sept. -Nov.
Dec . -Feb .
Mar. -May
June -Aug.
Sept. -Nov.
Dec . -Feb .
Mar . -May
June -Aug.
Sept. -Nov.
Dec . -Feb .
Mar . -May
June -Aug .
Sept. -Nov.
Year
1971
1971
1971-1972C
1972
1972
1972
1972-1973
1973
1973
1973
1973-197^
197^
1971*
197^
197^-1975
1975
1975
1975
Upper Pipea
116
135
2,2kQ
6,731
1,W5
16,580
62,096
127,^30
57,536
W,582
^3,917
65,872
25,2lU
1+5,829
90,123
80,792
3^,960
27,993
Upper Pipe"
52
36
81
91
96
95
99. k
99.9
99-7
99.8
99-9
99.8
99.7
99.8
99-9
99.9
99.7
99.7
Lower Pipea
107
2l*3
539
661
66
880
395
156
175
97
50
131
72
79
51
55
106
93
Lower Pipe
U8
6U
19
9
k
5
0.6
0.1
0.3
0.2
0.1
0.2
0.3
0.2
0.1
0.1
o.3
0.3
a. Volume in liters
b. Percent of total
c. Beginning of freely drained condition on January 1, 1972
79
-------
TEST CELLS 2A, 2B, 2C, 2D
The experimental design called for
the input of approximately 500 mm of pre-
cipitation each year into all of the cells.
Average annual rainfall at the site is in
excess of 900 mm so the cells were period-
ically covered, the cylinders with caps
and 2D with nylon reinforced Hypalon.
Leachate was initially collected from
each test cell on the date and at the cum-
ulative rainfall quantities in Table 3.
The early appearance of leachate from 2D,
the field-scale cell, also occurred in Cell
1, indicating some short-circuiting.
Figure 5 shows the quantity of leach-
ate collected from each test cell and with
precipitation. Test Cell 2C produced very
little leachate during the reporting peri-
od in comparison to 2A and 2B. A test
boring in the cell did not show any free
water stored in the cylinder. It was as-
sumed that a leak developed at a welded
joint near the surface of the soil cover
and very little of the precipitation actu-
ally entered the refuse mass.
The quantities of leachate collected
from 2A and 2B vary slightly, but by the
end of 1976 50% more than 2A and 72% more
than 2B per unit of surface area had been
collected from 2D. One possible cause of
this large difference could be leakage in-
to Cell 2D through the walls. There also
could be leakage through the cover. The
quantity of leachate collected from 2D was
in excess of the precipitation that occur-
red when the cover was removed.
The time delay between initial pre-
cipitation input and eventual steady leach-
ate production results from the absorptive
capacity of the refuse being achieved, or
field capacity being reached. The field
capacity for the refuse can be estimated
from the work of Fungaroli and Steiner,
knowing the in-place density of the refuse.
The values are presented in the first col-
umn of Table 4.
The water required to bring the test
cells to field capacity can be estimated
using these values presented in the first
column times the initial refuse depth, and
then subtracting the initial moisture stor-
ed in the refuse and adding in 50 mm of
water required to achieve field capacity
in the cover soil. This value is listed
in the second column of Table 4.
In order to compare this estimated
value with the apparent water actually
required, the apparent water required was
chosen as that precipitation less leachate-
value when leachate production initially
became steady. This apparent water re-
quirement is in the third column of Table
4. The apparent field capacity is presen-
ted in the fourth column.
The values of estimated and apparent
field capacity compare favorably, being
within 10%, or less of each other for all
cells. Values might be closer, but the
sequence of covering and uncovering the
cells made leachate flow erratic and esti-
mating the start of leachate flow was dif-
ficult.
LEACHATE QUALITY
Leachate samples were generally ana-
lyzed on a bi-weekly schedule. Work from
test cell 1 indicated that concentrations
were more total water flow than time de-
pendent so the sample concentration data
were reduced to weighted mean concentra-
tions at the approximate time at which 100
mm intervals of leachate flow were record-
ed. This normalized the data for each cell
so that concentration histories were based
TABLE 3. INITIAL COLLECTION OF
LEACHATE;
Test Cell
2A
2B
2C
2D
DATE LEACHATE COLLECTED
6-15-73
2-13-73
6-19-73
9-25-72
CUMULATIVE PRECIPITATION3
724
588
765
51
a. Millimeters
80
-------
LEACHATE VOLUMK, LITERS
CUMULATIVE LEACHATE, MM OVER CELL SURFACE AREA
CO
o
9
E>
O
O G>
• e o
O B>
o o
©B>
DO
>o
o o
o
o
o> o
G» o
& O
& o
o o
E> o
> o
o o
o e
t> e
o o
o
e
• < >a
o at
:e -
ia *"
t-i
s* i
D>
0
o
o
-------
TABLE 4. REFUSE FIELD CAPACITY
Test
Cell
2A
2B
2D
Estimated
Refuse
Field
Capacity3
350
358
400
Estimated Water
Required to Reach
Field Capacity"3
706
669
560
Apparent Water
Required to Reach
Field Capacity"
720
590
500
Apparent
Refuse
Field
Capacity0
356
327
375
a. millimeters/meter of refuse depth, after Fungaroli and Steiner
b. millimeters
c. millimeters/meter of refuse depth
on a parameter accounting for the varying
leachate quantities collected from each
cell. Concentration and mass removal his-
tories are presented in Figures 6-15.
A summary of peak concentrations and
the date of the sample is presented in
Table 5 for selected parameters. It.is
notable that all but one of the peak con-
centrations for test cell 2A occurred with-
in a two month time span starting with the
onset of leachate production. This was
the time period during which or shortly
after field capacity was achieved. Ap-
parently these peak concentrations were
the result of initial water contact with
the refuse when the supply of the leachable
substances and the contact time was high.
For test cell 2B the time span for
peaks was somewhat longer than 2A, rang-
ing to over 6 months. Test cell 2B did
begin leachate production 4 months ear-
lier than 2A and before the estimated
field capacity was reached so this range
might actually have coincided closely with
2A with the peak concentrations occurring
during or shortly after field capacity was
reached.
For test cell 2D the general time
span for peaks was four months, with cal-
cium and total hardness somewhat later.
The volume of leachate collected prior to
and during this time range was much great-
er than that for 2A and 2B and somewhat
later than when sufficient precipitation
had entered to satisfy both the apparent
and estimated water requirements. It did
not appear that the peak concentrations
for 2D occurred during the period that
field capacity was reached as occurred for
2A, 2B and test cell 1. If peaks did occur
during this period, then the high concen-
trations in the leachate would had to have
been either reduced by significant diluting
leakage from the sides of the cell or by
channelling through the cell. The latter
situation would result in field capacity
not actually having been achieved until
somewhat after estimated water requirements
had been met, possibly during the time and
leachate volume range when peak concen-
trations were recorded. Dilution was in-
dicated by the lower magnitude of almost
all of the peak concentrations of 2D as
compared to 2A and 2B.
Leachate Composition Comparibility
One of the primary objectives of the
later test cells was to evaluate the be-
havior of a field-scale test cell, 2D,
compared to similarly constructed small-
scale test cells 2A, 2B and 2C. The con-
cept was to determine whether similarity
existed between individual small-scale
cells as well as similarity between the
small-scale cells and the field-scale cell,
2D. It was hoped that the small-scale
cells would be adequate models of the large
scale cell so that future research efforts
might utilize the smaller cells for pre-
diction of field behavior.
82
-------
CUMULATIVE MASS OF COD REMOVED, g/kg DRY REFUSE
Mrotu!p>oiov^ja>
OOOOOOOO
00
CO
I
I 8
5
s
WEIGHTED MEAN CONCENTRATION OF COD. mg/1
-------
s
£1,400
§ 1.200
H 1,000
8 800
o
o
| 60°
Q
! 400
o
M
200
•2A
• 2B
I
I
I
I
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED PER UNIT SURFACE AREA, MM
Figure 8 . Weighted mean sulfate concentration.
1.400
1.4
D" 1-2
1.0
.6
.2
0
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED PER UNIT OF SURFACE AREA, MM
Figure 9 . Cumulative sulfate mass removal.
1.400
84
-------
2,400 -
«H
. 2.100
8
1.800
g l'
1,200
900
600
300
J L
_L
_L
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED PER UNIT OF SURFACE AREA, MM
Figure 10 . Weighted mean chloride concentration.
1,400
1
B 2.4
8 2.1
tf
A_
0-
A-
2A
2B
2D
1
1.5
1.2
.9
.6
.3
jy
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED PER UNIT OF SURFACE AREA, MM
Figure 11. Cumulative chloride mass removal.
1,400
85
-------
|> 600
S 525
S 450
o
2 375
1 300
g
o
225
o 150
3
S 75
J L
J_
_L
_L
_L
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED PER UNIT OF SURFACE AREA, MM
Figure 12. Weighted mean magnesium concentration.
1,400
3
tu
O
s
.50
.40
.10
.20
.10
.05
O 2D
A 1
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED PER UNIT OF SURFACE AREA, MM
Figure 13. Cumulative magnesium mass removal.
1,400
86
-------
1,800
1.000
2 600
g 400
g
200
-•A
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED FER UNIT OF SURFACE AREA, MM
Figure 14 . Weighted mean Iron concentration.
1.400
O
A
— 2A
— 2B
— 2D
— 1
100 200 400 600 800 1,000 1,200
CUMULATIVE LEACHATE VOLUME COLLECTED FER UNIT SURFACE AREA, MM
Figure 15. Cumulative Iron mass removal.
1,400
87
-------
TABLE 5. PEAK CONCENTRATIONS
oo
oo
Parameter
COD
Total
Kjeldahl-N
Ammonia-N
Test Cell 2A
Concentration3 Date
57330
1560
1035
Or tho -phosphate 390
Sulfate
Sodium
Potassium
Chloride
Iron
Magnesium
Manganese
Calcium
Zinc
Hardness
Total Solids
PH
Alkalinity
Acidity
Conductivity
1306
1900
2225
2335
1547
486
109
2280
150
7067
46484
6.2
11535
6720
17000
7-31-73
7-31-73
11-7-73
6-5-73
7-31-73
8-14-73
7-17-73
7-31-73
8-14-73
7-31-73
6-5-73
7-17-73
7-17-73
6-19-73
7-31-73
7-31-73
7-31-73
6-19-73
8-14-73
Test Cell 2B
Concentration Date
61600b
1897
1185
185
2000
1700
2939
2343
2902
617
115
4000
360
10575
45628
6.0
13880
6843
18000
4-24-73
10-23-73
10-23-73
6-19-73
10-23-73
7-17-73
11-7-73
9-25-73
4-24-73
10-23-73
5-8-73
5-8-73
7-17-73
4-24-73
7-31-73
12-4-73
2-27-73
7-17-73
8-14-73
Test Cell 2D
Concentration Date
41869
1242
947
82
1280
1375
1893
2260
1183
411
58
2300
67
6713
36252
6.2
8963
5057
16000
11-7-73
10-23-73
11-20-73
7-31-73
11-7-73
8-28-73
11-7-73
10-9-73
9-25-73
11-20-73
8-14-73
1-29-74
7-3-73
12-16-75
8-14-73
10-2-72
2-26-74
2-26-74
8-13-74
Test Cell 1
Concentration3 Date
37500
364
536
61
1160
1040
1950
1749
616
374
184
2363
104
7500
23600
6.3
8870
3620
12200
1-23-73
12-11-72
2-6-73
9-25-72
1-23-73
4-3-73
6-26-73
5-15-73
10-16-73
11-27-72
9-18-72
10-16-73
12-11-72
1-23-73
1-23-73
8-28-71
3-6-73
2-6-73
11-27-72
a. mg/1
b. early peak, concentration later dropped and peaked again on 11-7-73
-------
It was determined that on the basis
of a 10 component analysis of composition
that variations in performance between
cells 2A, 2B and 2C could not readily
be attributed to variation in refuse com-
position. Unit densities of 2A, 2B and
2C were similar, ranging from 392-431
kg/m . The refuse depth was the same for
all small cells. Water input to each cell
was assumed to be the same but the leach-
ate production varied somewhat between 2A
and 2B and very widely for 2C.
The initial refuse composition for
cell 2D was assumed similar to that of the
small cells. The density was somewhat
greater at 598 kg/m3 at a slightly higher
moisture content. The possible effect on
leachate concentration of this greater
density is not known. The input of water
was assumed to be the same as to the small
scale cells but it was obvious from Figure
5 that it was not. Cumulative leachate
production was actually greater than the
precipitation. Refuse depth was slightly
less in 2D at 2.44 m whereas in the small
cells the depth was 2.56 m.
To determine whether the concentra-
tion histories were similar for 2A and 2B
an analysis of differences was performed.
The differences were compared at the 10%
significance level.
A summary of the statistical test re-
sults comparing the concentration histories
of the parameters is presented in Table 6.
For only 4 of 14 parameters was the average
difference of the concentration history
curves of 2A and 2B not significant at the
107= level through the 0 - 1,300 mm range.
While 71 percent of the parameters tested
indicated test cells 2A and 2B were stat-
istically different (based on the test
used) examination of the COD concentration
history (Figure 6), as an example, showed
very similar responses for the two test
cells. This type of data pattern resulted
in a small standard deviation, which when
divided into the average algebraic dif-
ference of the data points, yielded a high
significant difference.
A total of 9 of the 14 selected para-
meters showed no significant difference
for the average of 2A and 2B or 2A as com-
pared to 2D. Of the remaining 5 parameters
only COD showed a highly significant dif-
ference. This indicated that cell 2A stat-
istically provided a reasonable model of
2D for many parameter concentration hist-
ories. This is not the situation for 2B
where only 6 of the 14 parameters showed
no significant difference. Since most of
the parameter histories for 2A and 2B were
not statistically similar, based on the re-
sults of this test it would be inaccurate
to state that any model of a large-scale
cell would provide as close a resemblance
as 2A has to 2D.
Many of the weighted mean concentra-
tion history curves showed a later peak
concentration for cell 2D than for 2A or
2B with reasonably close or slightly higher
concentrations. Since this early large var-
iation in concentrations and time to peak
might have influenced the results of the
paired difference tests, additional dif-
ference analyses were done for the data
points on the concentration history curves
for 2A and 2D beginning at the peak of the
concentration of 2D rather than at the 100
mm data point. These results are presented
in Table 7. Only 3 of the 13 parameters
did not show a significant difference. It
is interesting to note that all of these
three, COD, chloride and zinc, were signi-
ficantly different over the entire data
range.
Paired difference testing was also
done on the cumulative mass removal curves
through 1,300 mm. The results for selected
parameters with closely coinciding curves
are presented in Table 8. All showed a
significant difference, even when two
curves almost coincided throughout the en-
tire leachate volume range. While two
curves might almost coincide, for example
COD, normally one (2A or 2B) was just above
the other. This resulted in a small ave-
rage difference, but a very small standard
deviation, and a significant difference.
To overcome this weakness of the test,
the gain in mass removal for each 100 mm
interval for 2A was compared to that gain
for 2B. These paired difference test re-
sults are presented in Table 9. This pro-
vided a different perspective into the
closeness of the cumulative mass removal
curves for 2A and 2B with 9 of the 14 para-
meters showing no significant difference.
These results contrasted with the con-
centration history results where only 4 of
the 14 parameters showed no significant
difference. Apparently 2A and 2B were
relatively similar in mass removal but not
89
-------
TABLE 6 WEIGHTED MEAN CONCENTRATION HISTORIES - PAIRED DIFFERENCE TEST RESULTS
Parameter
COD
Sulfate
K-Nitrogen
Amnonia-N
Orthophosphate
Chloride
Potassium
Sodium
Calcium
Magnesium
Iron
Hardness
Manganese
Zinc
2A-2B
calc
3.82
2.17
4.15
1.64
2.51
.943
1.25
8.87
5.33
10.0
2.89
8.35
.354
7.50
2A-2B
1.83
1.83
1.83
1.83C
1.83
1.86
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
2A+2B
— 2 — - D
calc
1.31
2.87
2.14
1.40
-
2A+2B
2 ~ D 2A-2D
E10 'calc
5.00
0.98
1.97
1.83
.921
1.86
1.83
1.59
1.69
.321
1.45
0.79
1.83
2.26
2A-2D
So
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
2B-2D
t ,
calc
7.70
0.47
3.92
1.24
1.70
5.55
3.44
.259
5.52
5.80
2B-2D
C10
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
a. 'calc - calculated by division of the average difference by the standard
deviation of the average differences.
b. tio - tabular t
c. Underscored values shows no statistically significant difference.
TABLE ?. PAIRED DIFFERENCE TEST RESULTS. STARTING POINT AT TEST CELL 2D
Parameter
COD
Sulfate
K-Nitrogen
Ammonia-N
Orthophosphate
Chloride
Potassium
Sodium
Calcium
Magnesium
Iron
Hardness
Zinc
Starting Leachate
Volumes
500
500
600
600
300
500
500
500
500
500
500
300
300
2A-2D
' calcb
1.39
10.2
9.08
10.4
3.79
1.55
5.29
5.87
2.10
4.71
9.21
4.50
.983
2A-2D
tioc
1.94
1.94
2.02
2.02
1.86
1.94
1.94
1.94
1.94
1.94
1.94
1.86
1.86
Result
Not Significant
Significant
Significant
Significant
Significant
Not Significant
Significant
Significant
Significant
Significant
Significant
Significant
Not Significant
a. millimeters - volume per unit of surface area
b' 'calc ~ calculated by division of the average difference by the
standard deviation of the average difference
t - tabular t
90
-------
TABLE 8 . CUMULATIVE WEIGHT HISTORY PAIRED DIFFERENCE TEST RESULTS
Parameter
COD
Sulfate
K-Nitrogen
Ammonia-N
Orthophosphate
Chloride
Potassium
Sodium
Cal cium
Magnesium
Iron
Hardness
Manganese
Zinc
a. t
calc
2A-2B
tcalcb
4.25
4.58
1.96
14.2
63.6
9.16
3.14
29.0
27.3
17.9
8.82
18.1
7.21
44.5
calculated by division of
standard deviation of the
2A-2B
tlOb
1.83
1.83
1.83
1.83
1.83
1.86
1.83
1.83
1.83
1.83
1.83
1.83
1.83
1.83
the average difference
average difference
Results
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
Significant
by the
b. t - tabular t
TABLE 9 . INTERVAL MASS REMOVAL PAIRED DIFFERENCE TEST RESULTS
Parameter
COD
Sulfate
K-Nitrogen
Ammonia-N
Orthophosphate
Chloride
Potassium
Sodium
Calcium
Magnesium
Iron
Hardness
Manganese
Zinc
2A-2B
t a
calc
.522
.928
.536
1.35
2.48
.845
.308
2.78
1.49
1.93
.494
2.55
.405
10.0
2A-2B
fciob
1.833
1.833
1.833
1.833
1.833
1.860
1.833
1.833
1.833
1.833
1.833
1.833
1.833
1.833
Results
Not Significant
Not Significant
Not Significant
Not Significant
Significant
Not Significant
Not Significant
Significant
Not Significant
Significant
Not Significant
Significant
Not Significant
Significant
a. ^caic ~ calculated by division of the average difference by the
standard deviation of the average difference
b. t1Q - tabular t
91
-------
so in concentration histories. This in-
dicated that the removal of these sub-
stances from the refuse in 2A and 2B was
limited by the amount of the substance
readily available for leaching at that
time period in the decomposition process.
That is the leachate production varied
within some range, and the concentration
varied from cell to cell, but the mass re-
moval during each interval was comparable.
Application of the paired difference
statistic to the leachate data led to the
following observations:
1. Based on incremental increases in
masses of parameter removed, test
cells 2A and 2B, were not signifi-
cantly different except for ortho-
phosphate, sodium, magnesium, hardness
and zinc.
2. The statistic must be used care-
fully when evaluating the compara-
bility of concentration or cumulative
mass histories. While the majority
of parameters showed significant dif-
ferences between cells (except for 2A
and 2D), very similar data which were
consistently and slightly different
were determined to be significantly
different because their standard dev-
iation was small. Thus, cells 2A and
2B, designed to evaluate performance
duplication of identically construct-
ed and sized test cells were statist-
ically determined to have performed
differently. The test cells, however
did perform in a very similar manner.
MATHEMATICAL DESCRIPTION OF LEACHATE
CONCENTRATION HISTORY
The repetitive shape of the leachate
concentration curves and similar volumes
at peak concentrations for many of the
parameters indicated that the weighted
mean concentration history curves might
be mathematically described.
The concentrations in the leachate
are dependent on many factors, not all of
which are understood or known, especially
the magnitude of influence the factors
exert on resultant concentrations. Im-
portant variables might be the initial
mass of a substance readily available for
leaching, decomposition of refuse within
the fill and subsequent additional mass
availability, the pH, solubility limits,
the rate of water throughput, decomposit-
ion or reduction of the leachate constitu-
ents during travel through the fill, the
depth of the fill and cover soil effects
within the fill. The number of variables
involved and the lack of understanding of
their effect on resultant leachate concen-
trations made a semi-empirical curve-fit-
ting approach attractive as an initial
effort.
The shape of the weighted mean con-
centration history curves compared favor-
ably with the equation for two consecutive
first order reactions having the form:
C = klk2M (e-k1v_e-k2v) (1)
k2-k1
C is the concentration at any volume
of leachate, k^ and k£ are rate constants
and M is the total leachable mass per unit'
of surface area. The equation is in terms
of v, the volume of leachate collected per
unit of surface area, to coincide with the
weighted mean data and the plotting of con-
centration versus volume. Since volume of
leachate collected is some function of time
such as sinusoidal in a seasonal environ-
ment, the equation could be changed to a
time dependent function.
Since M was unknown, to solve for the
rate constants it was necessary to divide
Equation 1 by itself when the values of C
and v were known, resulting in the form:
C = r
e-klv-e-k2v _ (2)
e-klvmax-e-k2vmax
r was selected to be the peak con-
centration on the weighted mean concentra-
tion history curves occurring at cumula-
tive volume vmax< k-^ and ^ were deter -
by trial and error for best visual fit to
the 2A plot. The respective C^, vmax,
ki and ^ for selected parameters are pre-
sented in Table 10. The comparative con-
centration history plots are shown in
Figures 16-20.
A reasonably good visual fit was ob-
tained with Equation 2 for four of the
parameters. It was not possible with this
equation to describe the concentration be-
havior of iron because of the rapid fall
after peak. This also happened to a lesser
extent with COD and sulfate. Curve fitting
in these instances was primarily done so
that good coincidence was obtained at the
end of the data.
92
-------
WEIGHTED MEAN CONCENTRATION OF SULFATE, mg/1
WEIGHTED MEAN CONCENTRATION OF COD, mg/1
IO
CO
§ 5
TT
c n
re >
£• a
? >
5 «
-------
WEIGHTED MEAN CONCENTRATION OF MAGNESIUM, mg/1
• r
rr W
ft >
"• a
a «
I
WEIGHTED MEAN CHLORIDE CONCENTRATION, mg/1
c
9
rr
-------
96
WEIGHTED MEAN CONCENTRATION OF IRON, mg/1
to
O
O
o
o
o
o
o
OQ
NJ
O
<§.
rt
(D
D.
O
o
8
o
o
o
H
0
3
O
O
o
It
a
rt
H
0>
rt
H-
O
3
ET
H-
co
rt
O
<3
••
w
A
ro
1
10
*
B
O
o
r1
5
i_3
W
O
T)
W
P8
G
H
H
O
CO
G
5
8
|
^.
*
£j*
2
o
o
§
o
M
*O
O
O
M
10
O
O
o
o
H 10
§
ro
-------
TABLE 10. EQUATION CONSTANTS FOR CELL 2A
Parameter
COD
Sulfate
Chloride
Magnesium
Iron
a.
b.
c.
Ca
max
55,400
1,130
2,205
425
1,409
mg/1
mm - volume per unit of
I/mm
vb
max
200
200
100
200
200
surface area
*C1
.00098
.00138
.00120
.00150
.00062
*z
.0145
.0125
.0350
.0120
.0170
With kj^ and ^ known, it was possible
to solve Equation 1 for the total mass of
a parameter that might be leached. The
total mass per kilogram of dry refuse for
test cell 2A obtained from Equation 1 is
listed in the first column of Table 11.
The percent of this calculated total mass
that had actually been removed at 1500 mm
of leachate is presented in the second
column.
The total mass available and percen-
tage removal in Table 11 was based on the
shape of only 1500 mm of an infinite con-
centration history so these values should
be treated with caution. It is interesting
to note, though, that if this mass is an
accurate representation, the very high re-
moval percentages that had occurred after
only 1500 mm of leachate.
The total masses projected in Table
11 for sulfate, chloride and magnesium
ranged from 1/3 to 1/2 of the total amounts
actually measured in samples of the refuse
in test cell 1. The projected amount of
COD is only 11% of that measured from the
samples of refuse in test cell 1. The
values in Table 11 might be more accurate
projections of the mass that can be re-
moved than that total mass measured in test
cell 1 because some of the contaminant mass
is probably permanently bound in a non-
water soluble state.
SUMMARY AND CONCLUSIONS
Test Cell 1
The initial sanitary landfill test
cell was constructed at the Boone County
Field Site in June, 1971. It contained
395 metric tons of refuse at a wet density
of 592 kg/cubic meter. The maximum depth
of refuse was 2.6 m. Summarized findings,
based on the data collected through 52.5
months were as follows:
1. Over 791,000 liters of leachate had
been collected by December 1, 1975, re-
presenting 1831 mm of infiltration through
the refuse. It is estimated that an
TABLE 11. CELL 2A - TOTAL AVAILABLE MASS REMOVALS
Parameter
AVAILABLE TOTAL MASSd
REMOVAL at 1500 mm
COD
Sulfate
Chloride
Magnesium
Iron
89.6
1.41
2.73
.500
3.26
70%
75%
81%
86%
31%
a. g/Kg of dry refuse
96
-------
additional 106,000 liters of water was re-
quired to bring the cell to field capacity
meaning 36.5% of the precipitation over
the surface area of the final refuse lift
infiltrated the final soil cover into the
refuse. Less than 4,000 liters of leach-
ate, .5% of the total volume, passed
through the compacted soil liner.
2. The water balance method estimated
leachate production at 87.3% of the actual
volume collected. Seasonal differences in
the actual volumes and estimates were 4%
less during the winter (Dec.-Feb.), 19%
more in the spring, and 38% more in the
summer and fall.
3. The normal concentration history for
most of the parameters was low initial val-
ues rising to peak concentration during
the period field capacity was reached fol-
lowed by a slow downward trend to 10-35%
of the peak value after 4.5 years.
4. Over 58 kg of COD, 1.3 kg of sulfate,
10.7 kg of hardness, 1.3 kg of iron, 1.5
kg of sodium and 2.1 kg of chloride per
metric ton of dry refuse had been leached
out of the refuse mass after 1830 mm of
leachate.
Test Cells 2A, 2B, 2C and 2D
Four sanitary landfill test cells con-
taining municipal solid waste were con-
structed at the Boone County Field Site
during August 1972. Three of the cells,
2A, 2B and 2C were small-scale and the
fourth cell, 2D, was constructed similarly
to a normal landfill cell. These units
were constructed to compare the perform-
ance of small-scale systems with a field-
scale cell and to evaluate the variations
within the three small cells. Findings
after 51 months of data collection were:
1. The initial refuse composition and
moisture in all cells was determined to
be statistically similar. In-place refuse
densities in the small cells varied from
392-431 kg/m3. The density in cell 2D was
598 kg/m3.
2. After precipitation input to all cells
of 2050 mm, leachate collected per unit of
surface area varied from 213-2347 mm. The
low value occurred in 2C and was probably
due to a leak from the cylinder side or
base. The upper value was collected from
2D and was in excess of precipitation,
indicating leakage into the cell from the
soil walls. The apparent field capacity
of the refuse in all cells was found to be
within 10% of values reported in the liter-
ature.
3. Leachate composition histories were
statistically compared at intervals of 100
mm of leachate collected using a paired
difference test. The statistical test was
not adequate, indicating non-similarity
where data trends were close and similar-
ity in some instances where graphs showed
obvious differences. For most of the para-
meters studied the concentration histories
of 2A and 2B showed similar responses and
trends. The histories from 2D character-
istically showed a later and lower peak
value than in 2A and 2B.
4. Mass removals from 2A and 2B were gen-
erally similar and statistically the same
on an incremental basis for 9 of 14 para-
meters. Mass removed per kg of dry refuse
from 2D was less than that from 2A and 2B
for all parameters examined. After 1500
mm of leachate, mass removal was estimated
for five parameters to be from 31-86% of
the total available.
5. The density and leachate volume dif-
ferences precluded a definitive comparison
of the behavior of small and large-scale
test cells. The statistical evaluation
of the comparative behavior of identically
constructed small-scale cells was incon-
clusive.
ACKNOWLEDGEMENT
The test cell data analysis was per-
formed under contract with the Solid and
Hazardous Waste Research Division of the
Municipal Environmental Research Labora-
tory in Cincinnati, Ohio. Project Officers
for the two contracts were Richard A.Carnes
and Dirk R. Brunner.
REFERENCES
1. Wigh, Richard J., Interim Summary Re-
port; Boone County Field Site-Test Cell 1.
MERL, ORD, EPA, May 1976. (unpublished)
2. Wigh, Richard J., Boone County Field
Site Interim Report; Test Cells 2A, 2B, 2C
and 2D. MERL, ORD, EPA, February 1978.
97
-------
INFLUENCE OF MSW PROCESSING ON GAS AND LEACHATE PRODUCTION
Robert L. Hentrich, Jr.
Joseph T. Swartzbaugh
James A. Thomas
Systems Technology Corporation
245 North Valley Road
Xenia, Ohio 45385
ABSTRACT
A study was initiated in 1974 to investigate the effects of preprocessing municipal
refuse prior to landfilling on the decomposition products of that refuse once buried. The
preprocessing procedures considered are shredding, baling, or a combination of both
techniques. The leachate volume and composition as well as the composition of the gases
produced are being considered. The original project was for a three-year period. The
project being reported on is a new contract which calls for continued monitoring and
data analysis. The study of the gas and leachate was accomplished through the use of
landfill simulators buried in the ground. The facility is located at Franklin, Ohio.
The data to date indicates that preprocessing of waste does indeed have effects on
the production and composition of leachate and gas. Whether the effects produced are a
help or a hinderance will depend on the situations as faced by the individual landfill
operator or designer.
INTRODUCTION
The landfilling of municipal refuse
is the primary disposal methodology in
general use to date. However, the in-
terment of wastes with its subsequent
decomposition produces by-products which
offer the distinct potential for untoward
effects on the surrounding environment.
Leachate production is one of the pri-
mary sources for environmental insult
arising from landfilled material decompo-
sition. As a concentrated liquid waste
stream, it has potential for contaminating
both surface and groundwater.
Decomposition gases evolved from a
landfill present a potential hazardous
situation in the area of the fill site.
This hazard is of a long-term nature and
the threat exists long after a fill is
completed. This is especially true in the
case of methane which in concentrations of
5 to 15 percent with oxygen in the air
forms an explosive mixture.
This paper concerns itself with the
study of the preprocessing of municipal
refuse prior to landfilling and its sub-
sequent effect on the leachate and gases
produced. The preprocessing procedures
considered were baling, shredding, and a
combination of both procedures.
CELL OPERATION
Five landfill simulators are located
at the SYSTECH Waste Treatment Center site
in Franklin, Ohio. They are buried con-
crete cells each of which contains muni-
cipal refuse which had been subjected to
different preprocessing steps.1 The
test cells were charged with refuse as
follows.
Cell Refuse Weight (ww)
1 Baled, shredded refuse 11,700 kg
2 Baled, whole refuse 11,700 kg
3 Baled, whole refuse
(saturated) 11,700 kg
4 Unbaled, shredded refuse 10,800 kg
5 Unbaled, whole refuse 9,700 kg
All of the weights listed above were
calculated except the refuse wet weights
for Cells 4 and 5. The cells were
98
-------
instrumented and plumbed for temperature
monitoring, leachate collection, water
addition, and gas sampling.
Water additions were made in accor-
dance with a schedule designed to resemble
the rainfall patterns of the midwestern
region of the United States.
Leachate collection and gas sampling
were accomplished via plumbing lines which
connected each of the simulators with a
centrally located instrumentation cell.
Temperature data was gathered through the
use of 24 thermocouples placed in each of
the simulators.
Leachate samples and gas samples were
collected on a monthly basis and analyzed
for those parammeters pertinent to sani-
tary landfill operation. The cells were
also quantitatively drained monthly to
perform water balance studies.
MOISTURE MONITORING
Cells 1, 2, 4, and 5 have been
operated on a water addition and volu-
metric leachate collection basis for
approximately 3.5 years. The water
additions were made according to a schedule
resembling the annual rainfall pattern for
the midwestern United States. This sched-
ule is shown in Table 1. The particulars
of the physical arrangement for the water
addition procedures were described in
depth in the final report under a prior
contract with the USEPA (Ref. 1).
During the time period of the study
to date, Cell 3 was operated under "satu-
rated" conditions. This was accomplished
by only withdrawing enough leachate to
perform the required analyses during the
initial saturation period. After achiev-
ing saturation, the leachate was drained
monthly and an amount of water was added
which was equal to the volume of leachate
withdrawn. As no transpiration or evapor-
ation takes place within these enclosed
cells, the amount of moisture in Cell 3 is
assumed to remain constant.
The theoretical field capacity of
refuse is its absorptive capacity for
moisture. In theory, the amount of water
infiltrating a landfill should equal the
quantity of leachate exiting the landfill
once field capacity is reached. In a
practical, real world situation, however,
the definition of apparent or practical
field capacity as reported by Fenn2 is
more apropos to the problem. Fenn defines
field capacity as the maximum moisture
content which a soil (or solid waste) can
retain in a gravitational field without
producing continuous downward percolation.
The data in this report is presented in
terms of "field capacity" having been
attained at the initiation of continuous
leachate production.
The total moisture retained within a
cell is directly inferred from the volume
of water added minus the volume of leach-
ate removed. As the test cells are
enclosed, transpiration and runoff do not
enter into the calculation. The appparent
moisture retained in the cell was calcula-
ted as follows:
Apparent moisture retained in the cell
(ml/kg) =
1000 water added (£) - Leachate removed (£)
(kg solid waste)
As far as reaching the point of con-
tinuous leachate production is concerned,
Cell 2 (containing baled, unshredded
waste) began producing leachate in the
second month of operation. Cell 1 (baled,
shredded) began producing in the fifth
month, Cell 4 (shredded) began in the
fifth month, and Cell 5 (unshredded) began
producing in the sixth month. The results
indicate that the preprocessing of the
wastes prior to interment did have some
positive effect on the time frame in
which continuous leachate production was
begun.
The total moisture retained for the
cells containing baled refuse (Cells 1
and 2) continued the trend toward simi-
larity, but the cells containing unbaled
refuse abandoned the trend exhibited
earlier and showed a new trend toward
divergence with Cell 5 (unbaled, whole
refuse) having a higher propensity to
retain moisture. Both unbaled cells
retained significatly greater amounts of
moisture overall than did the baled
cells. The obvious inversely proportional
effects of the moisture retained phenomena
on leachate volume is shown in Figure 1.
Similar results were observed when
the moisture retained was normalized to
the wet weight of the refuse landfilled.
The average moisture retained figures in
99
-------
The average moisture retained figures in
Table 2 further illustrate this phenomenon.
The data to date indicate that the
processing of refuse prior to landfilling
does have a positive effect on the start
up of continuous leaching as well as the
volume of leachate produced when compared
to refuse which is landfilled without
baling or shredding. This trend was
noticeable during the course of the
original study and has become even more
pronounced during the first year of this
effort.
The moisture retained values are
still rising again indicating that theoret-
ical field capacity has not been reached.
LEACHATE DATA
Leachate samples have been collected
since January 1975. The leachate was
withdrawn from the bottom of each test
cell via lines which have their terminus
in the lower level of the instrumentation
cell. Collection was made from each of
the cells on a monthly basis. The volume
collected was recorded and analytical
procedures to determine chemical and
biological parameters were carried out.
The pH and conductivity of the leachates
were measured and the individual leachate
samples were analyzed for chemical oxygen
demand, total organic carbon, alkalinity,
total phosphorous, Kjeldahl nitrogen,
total solids, and for the following
metals: iron, copper, zinc, cadmium,
chromium, lead, and nickel. In general,
the analyses were completed according to
methods described in Chian and DeWalle.3
General statements that can be made
about the leachate emanating from five
test cells are that the greatest amount
of leachate to date has emanated from the
baled cells, Test Cells 1 and 2, closely
followed by the saturated bale cell, Test
Cell 3. Much smaller total amounts of
leachate volume have emanated from Test
Cell 4, the Shredded Cell, and even less
from Test Cell 5 containing the unprocessed
waste. Leachate volume in itself, however,
is not a measure of the potential for
environmental insult due to the leachate
since, in most cases, it can be stated
that the "quality" of the leachate is
"better" in the Test Cells 1 and 2 and
"worse" in the leachate from Test Cell 4.
By this we mean that the concentration
of measured pollutants in the leachate,
as well as the total accumulative mass of
specific measured pollutants in the
leachate, tends to be least in Test Cells
1 and 2 and tends to be greatest in Test
Cell 4.
Because of the slight, but con-
ceivably important differences in waste
composition and in leachate volume
emanating from the test cells, it was
necessary to devise a means of adjusting
the viewpoint with which we evaluated the
leachate emanating from the test cells.
It was decided that for purposes of
analysis and interpretation the most
meaningful measure of leachate quality
would be a measure of the total mass of
specific pollutants emanating from each
cell per kilogram of solid waste in the
cell. Thus, the pollutant out is calcu-
lated by multiplying the concentration of
pollutant as measured each month, times
the volume of leachate for that month,
divided by the total mass of solid waste
in the measured test cell.
There is some question about the
equivalence of even this measured para-
meter when attempting to compare test
cells. It was of some concern as to
whether or not the most meaningful measure
would be cumulative pollutant as a
function of time. This approach would
give an indication of the importance,
over some period, of the biological
activity within a landfill for the diff-
erent processings as well as the physical
and chemical interactions taking place.
Alternatively, we could consider the
total cumulative pollutant leached as
compared with the leachate volume passing
through the test cell. This latter
measure would seem to give a better
indication of the physical and chemical
interactions alone since it will be
dependent upon the amount of moisture
actually flushing through the cells.
Admittedly, this would also affect the
biological activity, but we feel that,
in general, the comparison on a time basis
gives measure of relative biological
activity and its effects, while the
measurement as a function on the leachate
volume out, is a more direct indicator of
the early stage physical and chemical
activity within the test cell. This is
not to infer that either approach is more
desirable than the other. There are
100
-------
merely two different ways of looking at
essentially the same data.
It is commonly accepted that baling
will prevent infiltration of moisture into
the mass of solid waste, while shredding
will accelerate this infiltration. These
two mechanical processes have different
aims. The intent of baling is to delay the
decomposition of solid waste as long as
possible so as to result in a weaker and
thus more "treatable" leachate. The aim
of shredding is to accelerate the decom-
position of the waste and to achieve a
stable landfill in a shorter period of
time. The actual needs and wishes of any
locality would determine which of these
approaches was more desirable to them.
Table 3 shows a comparison of the test
cells leachate on a common volume basis
at 5200 liters of leachate out. This
leachate volume was chosen since it is the
greatest amount of leachate to have
emated from Test Cell 5 to date and, thus,
all cells could be compared on a common
leachate volume basis. Viewing the table,
it can be immediately noticed that the
biological parameter measures of total
alkalinity, total solids, total organic
carbon, total Kjeldahl nitrogen, and
chemical oxygen demand all exhibit similar
distinquishing characteristics in comparing
processing methods.
Test Cells 1 and 2, both of which are
baled, show nearly identical total cumula-
tive values per kilogram for these para-
meters and they are quite obviously
significantly smaller than the totals for
any of the other test cells. Test Cell 3,
which is operated in a saturated condition,
is considerably greater than either Test
Cell 1 or 2, although it also is baled
and, as a matter of fact, shows almost
identical cumulative leachate parameters
as Test Cell 5 for these biological
measures. We are confident that this
similarity with Test Cell 3 and 5 is
happenstance, although it is a fortuitous
happenstance, and may serve as a guideline
for the nature of pollutants emanating
from a baled cell in an exceedingly moist
environment. The final conclusion to be
drawn on the biological parameters is that
the shredded material in Test Cell 4 does
indeed seem to be stabilizing at an
accelerated rate since the total amount of
each measured parameter is significantly
greater than the leachate of the unpro-
cessed or the baled cells.
It is interesting to note that not
only in the biological parameters but,
as may be seen in the rest of Table 3,
also in the metal parameters measured,
Cell 1 which contained shredded baled
waste is in every case nearly identical
with Cell 2 which contains only baled but
otherwise unprocessed waste. This would
seem to indicate that baling of the waste
is the important physical process in this
case and that the addition of shredding of
the waste (unless it were to achieve
easier or cheaper processing) is super-
fluous and unnecssary for baling. In
other words, if a community is intending
to operate a baled landfill and is contem-
plating the purchase of a shredder in
addition to a baler, this second piece of
equipment would appear to be unnecessary
if the long-term, slowly stabilizing
situation of a baled landfill is desired.
If rapid stabilization is desired, then we
would recommend not baling the waste but
rather shredding alone. The combination
of the two technologies shows no measurable
advantage to date.
The chemical parameters measured
consistently throughout the study were
selected metal ions. Table 3 thus also
shows, on a common leachate volume basis,
the amount of iron, copper, cadmium, zinc,
nickel, chromium, and lead leaching from
the five test cells. The results for
these materials are not as readily inter-
preted as the biological parameters. It
is noticeable that the amount of metals
leaching from the shredded cell is in
nearly every case much greater than the
amounts leaching from the other cells. It
is also noticeable that Cells 1 and 2, the
baled only and shredded baled cells, are
nearly identical in these parameters, but
the strong statements which are obvious
for the biological parameters are not
nearly as obvious, for the metal con-
stituents of leachate.
It is thought that the effect of pro-
cessing on the biological parameters is
much more noticeable because these tend to
be measures only of the organic material
contained in the waste which is very
similar both in composition and quantity.
The components in the solid waste, however,
which can result in leaching of specific
metals, are present only in small amounts
and thus are highly susceptible to great
variability from one sample to the next.
It is our feeling at this time that the
101
-------
inherent variability of solid waste has
resulted in large variations of specific
metal-bearing wastes from cell to cell.
This is because the total leachable metal
ions, although small in the refuse, are
susceptible to high percentage variation.
In other words, if the waste in Cell 1
were to contain 0.01 percent of its total
mass as zinc salts and Test Cell 4 were to
contain 0.03 percent of its total mass as
zinc salts, both of these are exceedingly
small numbers, difficult to measure with
any great accuracy, and yet note that one
is three times as great as the other.
Such slight discrepancies can result in
tremendous variation in the quality of the
leachate in each case. This points up one
of the more severe drawbacks to the sort
of uncontrolled experiment which is common
practice in evaluating and experimenting
on landfilling as a waste disposal method-
ology. Even within this limitation, it is
obvious that the shredded cell produces
higher levels of each measured pollutant
while the baling seems to produce a more
dilute leachate in each case measured on
a basis of common leachate volume. This,
in both cases, is thought to be due to the
nature of the processing employed and not
to the admitted variations in the compo-
sition of the waste in the test cells.
The shredding obviously makes more active
sites available both for biological
activity and for chemical and physical
interactions. This is born out by the
fact that the shredded cell has retained a
much higher level of moisture than the
baled cells, and in fact, the waste in
Test Cell 4 seems to act in a manner
similar to a household sponge.
Figures 2 through 25 show the plots
of cumulative masses of leachate parameters
versus, in one case, cumulative leachate
volume and, in the other case, time.
GAS COMPOSITION DATA
The gases produced via refuse decom-
position in a landfill include both the
products of aerobic decomposition (C02)
and anaerobic decomposition (CHj. and CO'z).
The bacteria responsible for methane
producton are strict anaerobes. Therefore,
methane will not be produced when oxygen
is present. The fact that researchers
(4, 5), have found oxygen and methane
simultaneously in their samples is an
indication that both situations can occur
simultaneously but in different portions
of the landfilled waste. Such factors as
oxygen presence in the upper layers of a
landfill, dissolved oxygen in the in-
filtration water, and the heterogenous
nature of the refuse results in pockets of
anaerobiosis and aerobiosis occurring
simultaneously in the same general land-
fill area.
The process of anaerobic decompo-
sition is similar to that found in an
anaerobic sewage sludge digester. The
initial process is the formation of
organic acids by the facultative anaerobic
acid formers. These organic acids then
provide a suitable substrate for the
anaerobic methane formers which utilize
them to produce methane. Other landfill
researchers (6) report this process to be
occurring in landfills. One of the
important goals of this study was to
determine compositional data on the gases
generated in a landfill environment and
the effects of preprocessing of waste on
gas composition.
Figures 26, through, 29, show time
history of the composition of gases drawn
from the test cells throughout this study.
The first impression is one of lack of
consistency both in time and from cell to
cell. Data indicative of high-methane
production is the situation for cell one
containing the baled, shredded waste. It
is obvious from the data that this cell is
and has for some time been indicative of
an anaerobic methane-producing situation.
Data for Cell 5, however, indicated that
little or no methane had been produced
within this cell to date. This is a
difficult conclusion to accept in light
of the fact that it would seem reasonable
that at least some portion of such a large
waste sample should have achieved anaero-
biosis. However, this is not borne out by
the data. The other cells all show varying
levels of anaerobiosis achieved. Varia-
tions in the composition of the gas stream
with time are not readily explainable
either in terms of seasonal changes or
other control factors such as water
addition rate.
In previous reports we indicated that
the early data did seem to follow seasonal
variations in the gas composition. At
that time we had hypothesized that this
could be due both to variations in the
temperature of the waste and its
concomitant effect on the health of the
102
-------
anaerobic culture as well as the dissolved
oxygen in the water added to the cells
which also would have a very important
effect on the anaerobic cultures. Later
data, however, does not seem to bear out
either of these hypotheses and, thus, we
have no ready explanation for the time
variations in the gas composition which
are seen.
CONCLUSIONS AND RECOMMENDATIONS
Analysis of the data collected in the
study during the time period covered by
this report gives rise to the following
conclusions.
In regard to moisture infiltration of
a landfill, the data indicate that the
preprocessing step of baling shows an
enhancement of leachate production both in
regard to time passage to the initiation
of continuous leaching and in the overall
volume of leachate produced. This is
shown by the fact that the baled cells
continuously produced leachate three to
four months before the unbaled cells.
It also can be seen in the total leachate
collected over the test period as well as
the moisture retained in the refuse cells
during the test period. It is concluded
that the baling step, not the shredding,
is the processing procedure to consider
where early or heavy leaching is of con-
cern.
The pollutant concentration, when
compared cell to cell on an equal volume
leached basis, shows that shredding is the
processing procedure that has the greatest
enhancement effect on leachate pollutants
produced. Baling on the other hand sub-
stantially lowers the pollutant mass flow
from a landfill.
Taken together, these observations
lead to the conclusion that the baling of
refuse will allow for a landfill which
will stabilize over a long period of time
with a greater volume of less concentrated
leachate being produced during the process.
On the other hand, shredding appears
to offer the shorter stabilization time
frame but with a lesser volume of more
concentrated leachate being produced.
The data concerning the baled waste
in a saturated environment when compared
with unprocessed waste offer an
coincidental but interesting conclusion.
That is, the baled waste in the saturation
state behaves quite similarly to unpro-
cessed waste in a normal landfill environ-
ment in regard to pollutant concentration
produced. This finding should be of
special interest to designers of landfills
in geographically wet areas.
In summary, based on the data to
date, it appears that either baling alone
or shredding alone are the preprocessing
procedures which should be considered when
designing landfills. Combined baling
and shredding appears to offer no
advantages when considering the quantity
or quality of leachate produced.
In regard to the composition of
gases produced in landfills with pre-
processing, the only conclusion to be
drawn at this time which is supported
by the data is that the shredding of
waste will result in a much more rapid
methane production.
LIST OF REFERENCES
1. R. L. Hentrich, Jr., and J. T. Swartz-
baugh, "A study of the effects of
various preprocessing procedures on
landfilled municipal refuse," Final
Report, EPA Contract No. 68-03-2024.
2. D. G. Fenn, K. J. Hanley, and
T. V. DeGeare, "Use of the water
balance method for predicting leachate
generation from solid waste disposal
sites," EPA/530/SW-168, U.S. Environ-
mental Protection Agency, Cincinati,
Ohio 1975.
3. E.S. Chian, and F. B. DeWalle, "Com-
pilation of methodology used for
measuring pollution parameters of
sanitary landfill seachate," Ecological
Research Series, EPA/600/3-75-011,
1975.
4. R. K. Ham, "Solid waste degradation
due to shredding and sludge addition,"
EPA 600/9-76-004, U.S. Environmental
Protection Agency, page 168 ff,
Cincinnati, Ohio 1976.
5. R. C. Ilerz and R. Stone, "Gas Pro-
duction in a sanitary landfill,"
Public Works 95(2), 84ff, 1964.
103
-------
6. Rovers, F. A. and G. J. Farquhar, "Gas
Production During Refuse IJecompostion,"
Water, Air, and Soil Pollution,
2-483 (1973).
104
-------
LIST OF FIGURES
Figure 1. Leachate Volume
Figure 2. Total Alkalinity
Figure 3. Total Alkalinity
Figure 4. Total Solids
Figure 5. Total Solids
Figure 6. Total Organic Carbon
Figure 7. Total Organic Carbon
Figure 8. Total Kjeldahl Nitrogen
Figure 9. Total Kjeldahl Nitrogen
Figure 10. Chemical Oxygen Demand
Figure 11. Chemical Oxygen Demand
Figure 12. Iron
Figure 13. Iron
Figure 14. Copper
Figure 15. Copper
Figure 16. Cadmium
Figure 17. Cadmium
Figure 18. Zinc
Figure 19. Zinc
Figure 20. Nickel
Figure 21. Nickel
Figure 22. Chromium
Figure 23. Chromium
Figure 24. Lead
Figure 25. Lead
Figure 26. Oxygen Composition
Figure 27. Carbon Dioxide Composition
Figure 28. Nitrogen Composition
Figure 29.' Methane Composition
vs
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
Mass
VS
in
VS
VS
Time
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Flow
Time
VS
Time
Time
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
VS
Time
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
Time
Leachate Volume
LIST OF TABLES
Table 1. Water Addition Schedule
Table 2. Water Balance Summary
Table 3. Comparison of Mass Flow of Leachate Parameters On An Equal Leachate
Volume Basis.
105
-------
o
o
CUMULfiTIVE LEflCHflTE VOLUME
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
TOTflL flLKRLINITY
o
--J
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
TOTflL flLKflLINITY
o
00
12.50 25.00 37.50 50.00
CUMULATIVE LERCHRTE VOLUME
62.5075.00. 87.50
(LITERS) «10*
100.00
-------
601
0.00
MILIGRflMS/KILOGRflM
40.00 80.00 120.00
*10Z
160.00 200.00
& X + * 0
o o o o o
rn rn rn m rn
en .c co r\> —•
Q
—I
XI
CO
Q
a
CO
-------
TOTflL SOLIDS
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
12.50 25.00 37.50 50.00
CUMULflTIVE LEflCHflTE VOLUME
62.50 75.00 , 87.50
(LITERS) «10?
100.00
-------
o
o
TOTflL ORGflNIC CflRBON
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
TOTflL ORGRNIC CflRBON
CELL 1
CELL 2
+ CELL 3
x CELL
12.50 25.00 37.50 50.00
CUMULRTIVE LERCHflTE VOLUME
62.50 75.00 87.50
(LITERS) *10*
100.00
-------
Ell
0.00
MILIGRRMS/KILOGRRM
80.00 160.00 240.00 320.00 HOP.00
fr X + fr 0
o o o o o
rn rn rn rn fi
tn 4= cd ro »-
Q
rn
r~
a
Q
o
nn
-------
TOTflL KJELDflHL NITROGEN
o.
CELL 1
CELL 2
CELL 3
x CELL
CELL 5
12.50 25.00 37.50 50.00
CUMULflTIVE LEflCHflTE VOLUME
62.50 75.00 . 87.50
(LITERS) «10*
100.00
-------
SLl
0.00
MILIGRflMS/KILOGRflM «10f
50.00 100.00 150.00 200.00
„ n nn
250.00
X + * G
o o o o o
rn ni ro rn rn
01 *: o> w *-
3D
Q
X
O
rn
a
rn
ID
z
a
-------
CHEMICflL OXYGEN DEMflND
CELL 1
CELL 2
CELL 3
x CELL
CELL 5
12.50 25.00 37.50 50.00
CUMULflTIVE LEflCHflTE VOLUME
62.50 75.00 87.50
(LITERS) »*102
100.00
-------
IRON
CELL 1
CELL 2
+ CELL 3
x CELL
CELL
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
o
o
IRON
00
^00
12.50 25.00 37.50 50.00
CUMULRTIVE LEflCHflTE VOLUME
62.50 75.00 87.50
(LITERS) *10?
100.00
-------
COPPER
o.
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
COPPER
"tToo
12.SO 25.00 37.50 50.00
CUMULflTlVE LEflCHfiTE VOLUME
62.50
(LITERS)
75.00
87.50
100.00
*1CT
-------
Oo
*-»o
*o
CCo
iC
cSg
¥
o
o
CflDMIUM
0 CELL 1
A CELL 2
+ CELL 3
x CELL M
CELL 5
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
CRDMIUM
ro
ro
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
"t.oo
12.50 25.00 37.50 50.00
CUMULflTIVE LEflCHflTE VOLUME
62.50 75.00 . 87.50
(LITERS) «10*
100.00
-------
ZINC
ro
GO
CELL 1
CELL 2
+ CELL 3
x CELL
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
ZINC
CELL 1
CELL 2
CELL 3
x CELL
12.50 25.00 37.50
CUMULflTIVE LEflCHflTE
50,00
VOLUME
62.50 75.00
(LITERS) *
87.50
100,00
-------
ro
tn
X*
V.
CELL 5
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
NICKEL
ro
CD
CELL 1
CELL 2
+ CELL 3
X CELL
CELL 5
12.50 25.00 37.50 50.00
CUMULflTlVE LEflCHflTE VOLUME
62.50 75.00
(LITERS)
87.50
100.00
-------
CHROMIUM
CM
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
CHROMIUM
ro
00
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
12.50 25.00 37.50 50.00
CUMULflTIVE LEflCHflTE VOLUME
62.50 75,00 87.50
(LITERS) «10*
100.00
-------
LEBD
PO
10
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
JUN
1975
OEC
JUN
1976
OEC
JUN
1977
OEC
JUN
1978
OEC
-------
LEflD
co
o
CELL 1
CELL 2
+ CELL 3
x CELL
CELL 5
^.00
1
.50 25.00 37.50 50.00
CUMULflTIVE LEflCHfiTE VOLUME
62.50 75.00 87.50
(LITERS) «10'
100.00
-------
OXYGEN
CELL 1
CELL 2
+ CELL 3
X CELL 4
CELL 5
JUN
1975
DEC
JUN
1976
DEC
JUN
1977
DEC
-------
100.00
-------
O
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LU
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NITROGEN
JUN
1975
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1976
DEC
JUN
1977
DEC
JUN
1978
DEC
-------
0.00
VOLUME PERCENTflGE
20.00 40.00 60.00 80.00 100.00
o o o o o
rn rn m rn rn
-------
WATER ADDITION SCHEDULE
Month
January
February
March
April
May
June
July
August
September
October
November
December
cm
0
5.54
11.08
11.08
11.08
5.5A
0
0
0
5.54
5.54
5.54
gal
0
104.5
209.0
209.0
209.0
104.5
0
0
0
104.5
104.5
104.5
Water Applied
Liter
0
396
791
791
791
396
0
0
0
396
396
396
135
-------
WATER BALANCE SUMMARY
Test Cell
Time to Reach
F.C.* in Mths.
Water Added to
Reach F.C. (£)
Avg. Moisture
Retained in Cell
Subsequent to
Reaching
F.C. (£)
Avg. Moisture
(ml/kg Refuse)
1 5 2397 x = 3419
a ± 1226
2 2 396 x = 3494
a ± 1350
4 5 1397 x = 5038
a ± 1725
5 6 2816 jc = 5733
a ± 1728
(36%)
(39%)
(34%)
(30%)
x =
a ±
x =
a ±
x =
a ±
x =
a ±
301
95 (32%)
300
116
465
159
590
178
(39%)
(34%)
(30%)
* Field capacity is defined as the maximum moisture content which a solid
(or solid waste) can retain in a gravitational field without producing
continuous downward percolation (Reference 2). Data is presented in terms
of "field capacity" meaning the initiation of continuous leachate production.
136
-------
COMPARISON OF CUMULATIVE MASSES OF LEACHATE PARAMETERS
ON A BASIS OF EQUAL LEACHATE VOLUME
Parameter
Total Alkalinity
Total Solids
TOC
TKN
COD
Iron
Copper
Cadmium
Zinc
Nickel
Chromium
Lead
Cell 1
Baled/Shredded
(mg/kg)
2411
5600
3190
94
6030
170
23
15.14
6475
0.24
131.0
202.3
Cell 2
Baled
(mg/kg)
2299
5729
3561
119
8494
275
23
21.26
6266
0.32
131.3
178.2
Cell 3
Baled/Constant
Moisture
(mg/kg)
3929
9592
5746
187
14926
293
52
31.37
2240
0.67
130.4
195.4
Cell 4
Shredded
(mg/kg)
6472
17742
8833
335
22492
608
48
46.15
50336
0.97
143.5
292.9
Cell 5
Unprocessed
(mg/kg)
3421
9154
5452
230
13887
104
45
38.99
11465
0.33
70.07
219.8
-------
PATHOGEN CONTENT OF LANDFILL LEACHATE
P. V. SCARPING and J. A. DONNELLY
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING
THE UNIVERSITY OF CINCINNATI
Cincinnati, Ohio 45221
and
D. BRUNNER
SOLID AND HAZARDOUS WASTE RESEARCH DIVISION
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
U. S. ENVIRONMENTAL PROTECTION AGENCY
Cincinnati, Ohio 45268
ABSTRACT
Increasing amounts of municipal solid waste, sewage sludge, hospital waste, chemi-
cals, etc., are being sent to sanitary landfills and open dumps. This material may
contain pathogenic microorganisms which may be leached out with rain water, and subse-
quently contaminate ground and surface waters. It was found in our studies that older
landfills contained Bacillus sp., Streptococcus sp., Corynebacterium sp. , and yeast.
Pathogens found in these older landfills included Listeria monocytogenes , Acinetobacter
sp., Moraxella sp. , and Allescheria boydii. Fecal streptococcal levels in all these
landfills studied were high. The fecal streptococcal MPN test was not always specific,
since in some leachates Gram positive rods, in addition to the streptococci, gave purple
growth in ethyl violet azide broth. The leachate also showed toxicity when added to pure
cultures of Gram negative rods and streptococci by repressing plate counts by at least
two logs.
Leachates from six experimental laboratory lysimeters at the University of
Cincinnati containing various combinations of municipal and hospital wastes and sewage
sludge were also studied. Eighty-five species of streptococci were isolated from these
experimental lysimeters, and fifty-seven species or 67 percent were enterococci. This
indicated that fecal material was present in the lysimeter contents. Pathogenic isola-
tions have not yet been made in these ongoing laboratory studies.
Leachates may present a microbial health hazard since fecal indicator bacterial
forms such as fecal streptococci are found in them. However, only a limited number of
pathogens have been isolated from older landfill leachates and none have been isolated
as yet from the ongoing University of Cincinnati experimental lysimeters.
INTRODUCTION ±n sanitary iandfills pr
Today one of our primary concerns is open dumps. These solid wastes contain
the assessment of the environmental health untreated animal and human fecal matter,
hazard associated with the disposal of animal remains, and sewage sludge. The
138
-------
use of disposable diapers is one way
human excreta becomes present in solid
waste. Ground and surface waters may
become contaminated by microbial movement
from the landfill site through the sur-
rounding soil by the leaching action of
rainwater or by the addition of liquid
wastes (Peterson, 1971, 1974; Brunner,
1974; Engelbrecht et_ al., 1974). Human
health could thus be affected through
direct contact with the solid waste, its
leachate or indirectly through con-
taminated water, air, land, or via biolo-
gical vectors. The potential hazard from
pathogenic agents reaching sanitary land-
fills is a function of three interrelated
conditions (Engelbrecht ejt al., 1974) :
1. the density and nature of the
pathogens initially placed in
the landfill,
2. the ability of the pathogens
to survive or to retain their
infectious properties in the
landfill environment or in
the leachate, and
3. the ability of the pathogens
to move through the landfill
with the leachate into the
surrounding environment and
present a hazard to human
health.
As pointed out by Engelbrecht
et al. (1974) , Pohland and Engelbrecht
(1976), and by Blannon and Peterson
(1974), specific information on the sur-
vival of infectious agents in sanitary
landfills is essentially nonexistent.
It is thus the prime concern of these
studies to characterize and evaluate the
persistence of microbes, especially
those of pathogenic significance or
indication, in landfill leachates.
EXPERIMENTAL APPROACH
The objectives of this study were
to evaluate the microbial health hazard
associated with leachate. The initial
and continuing effort of Phase I was to
determine periodically the presence of
microbial (bacterial and fungal) pathogens
in leachates obtained from several exist-
ing commercial and experimental landfills,
and to determine the species of fecal
streptococci commonly found in leachate
in order to ascertain their significance.
The Phase II study was undertaken to study
the microbial populations emanating from
recently deposited wastes.
The sources for leachate studied
under Phase I are briefly described in
Table 1. The commercial landfill, cur-
rently operational, covers approximately
700 acres and was begun in 1954. Leachate
is collected from a pipe which drains the
landfill leachate from a filled-in 15 acre
lake, assumed to be the lowest drainage
area for the landfill. The leachate is
assumed to be representative of the entire
landfill and is at least seasonally diluted
by groundwater discharge. The site
receives municipal and commercial wastes
and had accepted industrial wastes in the
past.
The Walton, Kentucky sources are
from the U.S. EPA (SHWRD) Boone County
Field Site. The 435 ton landfill was
constructed in two weeks during June, 1971,
with municipal refuse and covered with a
clay loam placed on a 2 percent slope.
Leachate has been volumetrically collected
since August, 1971. The 2 ton landfill
was also constructed of municipal refuse,
out filled and placed in operation in 2
days during August, 1972.
The Center Hill sources are also
from an ongoing SHWRD experimental land-
fill project. Nineteen batch-type land-
fills containing 2 tons of municipal
refuse, some with selected materials
(CaC03, H20, industrial sludges) added,
were constructed in November 1974 and
April, 1975.
Small-scale experimental batch-
type landfills were specially constructed
(Figure 1) at the University of Cincinnati
to investigate microbial population changes
from the initial time of disposal. The
contents of these landfills (Table 2) are
combinations of or solely sewage sludge,
municipal refuse, and shredded hospital
ward wastes.
Leachate samples from all the test
sites, except the University of Cincinnati
139
-------
TABLE 1. CHARACTERIZATION OF COMMERCIAL AND
EXPERIMENTAL LANDFILLS AND LABORATORY
LYSIMETERS USED IN THIS STUDY
Type of
Landfill or
Lysimeter
Contained
In
Solid
Waste
Dimensions Added
Amount
of Solid Date
Waste Prepared
Location
of Site
Phase I
Commercial Full-
Scale Operational
Landfill
Soil
Municipal, Millions
700 Hospital, of
Acres Commercial Tons
1954
Experimental Large-
Scale, Batch-Type,
Field Sanitary
Landfill
40'xl40' 435 June, Walton,
Soil x8.5' deep Municipal Tons 1971 Kentucky
Experimental Field
Large-Scale,
Batch-Type
Lysimeters
Steel
Cylinders
in
Soil
2 August, Walton,
12'x6* Municipal Tons 1972 Kentucky
Experimental Field Steel
Large-Scale,
Batch-Type
Lysimeters
Cylinders
in
Soil 12 'x6'
Municipal ,
Sewage
Sludge,
Industrial
2
Tons
November ,
1974 and
April,
1975
Center
Hill,
Cincinnati,
Ohio
Phase II
Experimental,
Laboratory,
Small-Scale
Lysimeters
Steel
Drums at
20°C in the
Laboratory 2 ' x2 '
Municipal,
Hospital,
Sewage
Sludge
150
Lbs.
August,
1978
University
of
Cincinnati
TJame withheld since commercial firm involved.
140
-------
FIGURE 1
Schematic of Experimental Laboratory Lysi meter
Gas Sampling Bulb
20 in
Sampling Basin
Watering Ports
SOLID WASTE
Excess
Storage Area
Watering trough
Thermistor
Drainage
Drainage Port
141
-------
TABLE 2- CONTENTS OF EXPERIMENTAL LABORATORY - SCALE,
BATCH-TYPE SANITARY LANDFILL TEST CELLS
(LYSIMETERS) AT THE UNIVERSITY OF CINCINNATI
Lysimeter Contents
Sewage Sludge
Municipal Solid Waste and
Sewage Sludge
Municipal Solid Waste
Municipal Solid Waste
Municipal Solid Waste and
Hospital Waste
Hospital Waste
Constructed in August, 1978, and placed at 20°C.
142
-------
lysimeters, were each aseptically col-
lected four times a year. The samples
were refrigerated within one hour after
collection, and were analyzed within 24
hours. The leachates in the University
of Cincinnati study were collected on a
frequent basis, often weekly, and were
examined within 24 hours. All leachates
were diluted and plated using the bacteri-
ological smear technique both aerobically
and anaerobically on blood agar plates,
and on other differential agar plates.
Cooked meat medium and selenite F were
used also. Coliform and fecal strepto-
coccal MPN tests were included. Chemical
analyses were made to characterize the
leachates.
The microorganisms obtained for
identification came from the aerobic and
anaerobic blood plates, selenite F,
cooked meat medium and azide dextrose
medium. The procedures for the identi-
fication of microorganisms present in
leachate came from Microbiological Methods
for Monitoring the Environment (1978),
Standard Methods for Examination of Water
and Wastewater (1976), and current clinical
manuals. API strips for the enterobactera-
ceae and the clostridia were also used.
EXPERIMENTAL RESULTS
The criteria used to determine if
an isolated organism was pathogenic was
if it appeared on the U. S. Public Health
Service's Classification of Etiologic
Agents on the Basis of Hazard (1976).
This classification is based on how
infectious the microorganisms are for
humans and animals, as shown in Table 3.
Bacteria from Class 2, moderately infec-
tious organisms, which could be expected
to be found in municipal refuse are listed
in Table 4. Those organisms which could
be found in human or animal feces were
listed in this table, along with respi-
ratory organisms which might find their
way to refuse.
Certain species of streptococci occur
only in man, and/or animals, fowls, and/or
vegetation. Therefore, such information
is useful for source identifications.
Table 5 shows the human, animal, and vege-
table origins of streptococcal groups.
Microbes Isolated and Identified
The microorganisms isolated from the
landfills are shown in Tables 6 and 7.
They are grouped by the landfills from
which they were obtained, and are listed
in alphabetical order. The four most
frequent species isolated, listed in the
order most frequent, are: species of the
genera Bacillus, Corynebacterium, and
Streptococcus, and yeast. The yeast iso-
lates were not differentiated into genera.
It was usual to find only 3 or 4 genera
in a leachate sample. Note on the tables
that some of the microorganisms are marked
with an asterisk. These appear in the
Public Health Service publication
Classification of Etiologic Agents on the
Basis of Hazard (1976) as Class 2 bacterial
agents. These are Listeria monocytogenes,
Moraxella, and Acinetobacter. Allescheria
boydii (see Table 7), while not on the CDC
list, is a pathogen which causes madura
foot abscesses. In general, all these
microorganisms are not particularly
invasive, but they are pathogenic.
These landfills were over 4 years
old, yet many types of microorganisms were
present. The spore-bearing microorganisms
were the Bacillus sp., the Clostridia sp.,
and the fungi. These are known to endure
in the presence of high temperatures,
disinfectants, etc. The Listeria mono-
cytogenes is known to be a particularly
persistent microorganism in refrigerated
cultures, and are known to grow at low
temperatures.
Assays on leachate from the older
landfills (Phase I) were begun in
November, 1977, and indicated that total
coliform, and consequently fecal coliform
counts, were less than 30/100 ml. Previous
investigations of the coliform content of
the Batch-Type Field Sanitary Landfill
leachates by others indicated they were
not detectable 30 weeks after construction
of the landfill. In Phase II of this
study, the small scale landfills at the
University of Cincinnati showed total
coliform titers of 10 from initial
leachate samples taken from the municipal
solid waste lysimeters. The titer was
10 three weeks later, 10 after four
weeks, and less than 20 after six weeks.
143
-------
TABLE 3. THE BASIS FOR CLASSIFICATIONa OF
HAZARDOUS MICROBIAL AGENTS
CLASS
1
2
3
4
DEFINITION
Agents of no or minimal hazard to human or animal health.
Agents of ordinary potential hazard such as staphylo-
cocci, that can cause disease when the agent penetrates
the skin.
Agents of special hazard such as human tuberculosis
which requires special conditions in order to contain
them.
Agents of extreme hazard to personnel or may cause
serious epidemic disease. Example: smallpox virus.
Foreign animal pathogens which cannot be permitted in
the United States. Example: foot and mouth disease
virus.
From Classification of Etiologic Agents on the Basis of Hazard, 1976.
144
-------
TABLE 4. REPRESENTATIVE PATHOGENIC MICROORGANISMS
WHICH MAY BE ISOLATED FROM MUNICIPAL LANDFILLS
Microorganisms Natural Habitat in
Nature Man
Clostridium sp. + +
Erysipelothrix + +
insidiosa
Klebsiella + +
pneumoniae
Lister ia sp. +
Mima polymorpha - +
(Actinetobacter sp.)
Moraxella sp. - +
Pasteurella sp. - +
Salmonella sp. + +
Shigella sp. - +•
Staphylococcus - +
aureus
Streptococcus - +
pyogenes
Highly Infectious Disease Produced
Food poisoning, diarrhea,
gas gangrene
Skin infection, arthri-
tis, septicemia
+ Pneumonia
Abscesses
Skin, eye infection,
pneumonia
Urinary tract infection
Gastrointestinal
disturbance
+ Food poisoning,
septicemia
+ Intestinal infection
Wound infection,
food poisoning
+ Acute infection
As defined by the CDC Classification of Etiologic Agents.
145
-------
TABLE 5. THE HUMAN, ANIMAL, & VEGETABLE
ORIGINS OF STREPTOCOCCAL GROUPS
Group
A
B
Not Groups A, B, or
D (i.e. Groups C, G, F)
D, not enterococcus
Enterococcus
(Group D)
Viridans
Q
Species
S. pyogenes
S. agalactiae
S. dysagalactiae
S. equi
S. equisimilis
S . zooepidemicus
S. anginosus
S. bo vis
S . equinus
S. faecalis
S. faecalis subsp.
liquefaciens
S. faecalis subsp.
zymogenes
S. faecium
S . durans
S. salivarius
S. mitis
S . avium
Origin
man
cattle , man
man , animal
animal
horse
man , animal
vegetarian , insects
man , animal
man , animal
man , animal
man
man
fowl
Lancefield Groups A through Q are determined by the precipitan test.
Viridans is determined by henolysis on blood agar plates.
146
-------
TABLE 6. BACTERIA ISOLATED FROM COMMERCIAL AND
EXPERIMENTAL LANDFILL LEACHATES
COMMERCIAL SITE
Achromobacter sp.
Anaerobic streptococcus
Bacillus sp.
Clostridium fallax
Clostridium sp.
Corynebacterium sp.
pseudomonas - like
Streptococcus sp.
a. streptococcus
BOONE COUNTY FIELD SITE
CENTER HILL FACILITY
Aeromonas sp.
Bacillus sp.
CDC Group Ve-1
Corynebacterium sp.
*Listeria monocytogenes
Micrococcus sp.
*Moraxella sp.
Neisseria sp
Serratia marcescens
Streptococcus sp.
a streptococcus
*Acinetobacter sp.
Bacillus sp.
Clostridium sp.
Corynebacterium sp.
Enterobacter cloacae
*Listeria monocytogene s
pseudomonas - like
Staphylococcus albus
Streptococcus sp.
*CDC Agents of ordinary potential hazard.
147
-------
TABLE 7. FUNGI ISOLATED FROM COMMERCIAL AND
EXPERIMENTAL LANDFILL LEACHATES
COMMERCIAL SITE Yeast
BOONE COUNTY Allescheria boydii
Cephalosporium sp.
Yeast
CENTER HILL FACILITY Fusarium sp.
Pen!oilHum sp.
Sepedonium sp.
Yeast
148
-------
Obyiously, the total coliform (and the
fecal coliform) MPN tests were not desir-
able as indicators of pathogenic presence
in landfill leachates because die-off was
more rapid than the pathogens which were
later isolated.
Unlike the coliforms, fecal strepto-
cocci were found in most all leachates
sampled. The pathogens listed in Table 6
were frequently found in the presence of
fecal streptococci; therefore, the fecal
streptococci assay is a better indicator
of the presence of pathogens than fecal
coliform. Results of streptococcal assays
of the Center Hill leachates (Figure 2)
indicated they were not always present in
all leachates, regardless of whether the
leachates derived from municipal refuse
or mixtures of refuse and selected
industrial sludges. This indicates the
possibility of pathogen presence in the
absence of fecal streptococci, dependent
on the ability of pathogens to withstand
the environment which depressed the fecal
streptococci.
Assay Interferences
The absence of fecal streptococci in
some of Center Hill assays was surprising
and warranted further investigation
(Figure 2). While some of the experi-
mental landfills contained heavy metal
bearing wastes, the negative results of
the fecal streptococci assays occurred in
the municipal refuse leachates as well
as from the refuse-industrial sludge
wastes.
A Gram stain of all of the positive
ethyl violet azide tubes showed that some
of the positive tests did indeed contain
streptococci, while a large number of
others showed Gram positive rods instead
of cocci. Litsky et_ al. (1953) found that
upon the examination of sewage and river
water that Gram positive rods growing in
the presumptive test azide dextrose broth
tubes could also grow out in confirmatory
ethyl violet azide broth and produce a
positive reaction, i.e., a purple button
in the bottom of the tube.
Leachates from the municipal solid
waste test cells at Center Hill that were
positive for fecal streptococci were used
as an undiluted sample in the test pro-
cedure , and were found to inhibit strep-
tococcal growth. After the leachate was
diluted to 10"1 or 10~2, the streptococci
did grow out in the azide dextrose and in
the ethyl violet azide broth to produce a
positive test for streptococci. In addi-
tion, the large number of very low strep-
tococci titers, especially in the Center
Hill test cells containing municipal solid
waste, i.e., Test Cells 3, 11, 15, and 16,
suggested that the streptococcal levels
were becoming low and that the streptococci
enter the leachate in an irregular fashion,
and thus do not always appear in the
leachate. It should be mentioned also
that the numbers of Gram positive sporu-
lating Bacillus sp., recovered on plate
counting medium far exceeded those of the
other microorganisms present. Perhaps
the large number of these rods interfere
with the growth of the fecal streptococci.
Some preliminary work was done to
determine if leachate itself could inter-
fere with the isolation of pathogens,
since so few were present and they
appeared in such an irregular fashion.
The study consisted of adding washed cells
of Klebsiella pneumoniae, Salmonella
typhimurium, Pseudomonas aeruginosa, and
Streptococcus faecalis to both phosphate
buffer and leachate held at room tempera-
ture. Recovery of the microbes commenced
immediately after the dilutions were pre-
pared. As seen in Figure 3, the cultures
in the leachate decreased at least 2 logs.
The recovery counts in leachate were
10 /ml while those placed in buffer had a
count of 10^ or more. This indicated
possible interference of the leachate with
the recovery procedure, and the possible
inhibition of pathogen growth. Other
investigators (Glotzbecker, 1974) in our
laboratory showed that only 1% Escherichia
coli and 10% Streptococcus faecalis sur-
vived 2 hours in Boone County leachate at
10°C. Possible explanations for this
apparent toxicity could include (1) meta-
bolic inhibition due to drastic changes
in the chemical environment from the
growth medium to the leachate; (2) toxic
levels of specific chemical constituents
of the leachate; and (3) biological compe-
tition for nutrients by other, more
149
-------
en
O
FIGURE 2
Fecal Streptococcal Presence in Center Hill Experimental Field Lysi meter
10'-
io6-
*3
u
O —
u E A
£ 0 10 '
Q. o
£ \
co Z .,
o. If3
o SE
i£
io2-
101-
S Gram positive rods observed
ED Gram positive cocci observed
S Sewage Sludge
Ca CaC(>3 added
1 Industrial Sludge
^
X
X
X
X
X
X
X
X
* 4
99
-
••
••
ft
»»
«»
««
• •
wmtm
x
X
^s
X
X,
,
X
X
X
\
J§
Vs,
X
X
X
X
X
^1
^
\
\
X
X
N
^^
i
(
, — 1
X
X
X
X
X
X
X
X
S
st
•MM
••
* *
•;
..
i
i
* *
0 9
• •
••
• «
••
ft
..
I
— i
X
X
X
X
^
• *
»•
..
••
• *
••
* -•
• •
I
I
••
•*
••
••
It
• 1
••
* •
• •
••
..
**
1 23456 7 8 9 10 11 12 13 14 15 16 17 18 19
Center Hill Test Cells
-------
FIGURE 3. The Inhibition of Landfill Leachates
in9-
108-
m7-
! io6-
|io5
O
lio4-
io3-
102-
101'
B = Buffer
M
M
•H
^
•»
^
B
L
B
L
B
L = Leac hate
L
B
L
K. pneumoniae S. typhimurium Rqeryginosg
on " on ~ on
EMB Agar XLDAgar EMB Agar
plates plates plates
faecalis
on
KFAgar
plates
-------
numerous organisms. Suppression of growth
or even reduction in the numbers of
organisms detected does not necessarily
indicate death, but merely an inability
to ascertain active growth or metabolism.
A change in the environment, such as
achieved by dilution in a less antagonistic
liquid (buffer solution, clean water, etc.),
can lead to more diverse identification
and enumeration. Alternatively, long
term exposure to the antagonistic con-
ditions of leachate may effectively reduce
the number of pathogens and indicators
released from a landfill.
Phase II Assays
The specially constructed experi-
mental landfills were constructed in
August, 1978 and kept in a 20°C environ-
mental room.* The landfills received 20
inches (508 mm)/yr. of net infiltration
(Figure 4). The wastes were brought to
field capacity over a 6 week period.
Leachates were collected for analysis on
a frequent basis, often weekly.
Bacterial counts of the solid wastes
used in the construction of the lysimeters
are reported in Table 8. The numbers of
total viable aerobic bacteria, total and
fecal coliforms, and fecal streptococci
recovered were very similar, regardless
of waste type; only fecal streptococci
seemed to show a significant difference.
The species of gram negative bacteria
recovered from the sewage sludge, and the
municipal and hospital wastes used in the
construction of the lysimeters are listed
in Table 9. Note the presence of the
pathogens. CDC Class II Klebsiella sp.,
were found in all three wastes; Pasteurella
hemolyticum was found only in sewage sludge;
Mima sp., was found in both sewage sludge
and refuse; the other pathogens isolated
were found in both hospital waste and
refuse. Thus, pathogens may be expected
to be found in landfilled wastes.
The isolation and speciation of
fecal streptococci are shown in Table 10,
but this study is not completely meaning-
ful at this time b-ecause of the small
number of colonies which have been identi-
fied. This work is continuing and should
allow for more complete characterization
of the wastes placed in the landfills.
*The temperature of the landfills stabi-
lized at 20°C one week after construction.
Numbers of bacteria quantified over
the initial 17 week period of waste
decomposition are provided in Tables 11,
12, and 13. The aerobic plate counts
showed a gradual decline in the number of
organisms over the 17 week period.
Leachates from sewage sludge generally
yielded slightly smaller numbers of bac-
teria than when mixed with municipal
refuse. Leachates from hospital waste
generally yielded slightly larger numbers
than leachates from the hospital waste-
municipal refuse mixture. The number of
bacteria assayed with blood agar plates
also showed a gradual decline over the 17
week period. A change in the method of
analysis for total and fecal coliform (to
that of Allen e_t al., 1976) resulted in
slightly larger enumeration in weeks 13,
15, and 17, but the decline in the number'
of organisms over the 17 week period was
very pronounced for the coliforms and less
rapid for the fecal streptococci. The
municipal refuse-sewage sludge mixture
had larger numbers of indicator organisms
than did the sewage sludge alone, but the
two sources of leachate yielded approxi-
mately the same numbers by week 17. The
somewhat erratic numbers of fecal strep-
tococci indicated that they can thrive
and multiply in some landfill environments.
The data summarized in Table 14 is
incomplete, since the fecal streptococcal
speciation studies are in progress. Fecal
streptococci have been observed in leach-
ates from all laboratory lysimeters in
higher numbers than the fecal or total
coliforms. We hope in the near future to
accumulate more complete speciation data
so that we may draw final conclusions as
to the origins of the fecal material in
the lysimeters. However, at this time
eighty-five species of streptococci were
isolated from these experimental lysi-
meters , and fifty-seven species or 67
percent were enterococci. This indicated
the presence of fecal matter in the lysi-
meter contents,, and thus indirectly the
presence of bacterial pathogens. No
pathogens have been isolated yet; assays
are continuing. However, Table 15 indi-
cated the presence in these leachates of
diphtheroids of unknown etiology which
have been found but not identified.
Therefore, we will have to delay final
conclusions as to the presence of patho-
gens until pathogenic identification
152
-------
01
CO
FIGURE 4
Addition of Water and Production of Leachate in Laboratory Lysimeter C
LYSIMETER UC-C
Water Added
Leachate Produced
12 14 16 18
WEEKS
Post Lysimeter Construction
-------
TABLE 8. BACTERIAL COUNTS OF THE SOLID WASTE USED IN
CONSTRUCTIOM OF THE UNIVERSITY OF CINCINNATI
LYSIMETERS
Bacterial Counts
c"li^
Waste Total
Coliform
Sewage
sludge 2.8xlOn
Hospital
waste 9.0xlG10
Municipal
waste 7.65xl010
KPN/gram
Fecal Fecal
Coliform Streptococcal
2.3xl010 3.3xl09
9.0xl010 8.6xl010
4.65xl010 2.5X1011
Bacterial
Numbers /grana
1.67xl09
3.8xl09
4. 2 8x10 10
aRecovered on brain heart infusion agar plates.
154
-------
TABLE 9. GRAM NEGATIVE BACTERIA ISOLATED FROM SOLID WASTE
USED IN THE CONSTRUCTION OF THE UNIVERSITY OF
CINCINNATI LYSIMETERS
Bacterial Genera
and Species
Oxidase Negative
Lactose Fermenters
Escherichia coli.
Enterobacter sp.
*Klebsiella sp.
Citrobacter sp.
Oxidase Negative
Non- lactose Fermenters
Serratia sp.
Proteus sp.
Providance sp.
*Salmonella sp.
Oxidase Positive
Non-fermenters
Aeromonas sp .
Flavobacterium sp.
*Herellea sp.
*Mima sp .
*Moraxella sp.
*Pasteurella hemolyticum
Pseudomonas sp.
Sewage Sludge
8
7
3
4
4
3
b
b
b
1
b
2
b
1
1
Numbers Isolated From
Municipal Waste
3
3
3
10
b
10
1
3
2
b
2
1
1
b
2
Hospital Waste
2
6
5
11
4
13
1
1
3
b
2
b
1
b
17
Identified by the procedure of Wolf (1975).
None detected.
£1
A fermenter.
*These bacteria appear on the CDC list classifying etiologic agents on the basis of
hazard (Classification of Etiologic Agents on the Basis of Hazard, 1976).
155
-------
TABLE 10. STREPTOCOCCAL GROUPS AND SPECIES ISOLATED FROM
SOLID WASTE USED IN THE CONSTRUCTION OF THE
UNIVERSITY OF CINCINNATI LYSIMETERS
Streptococcal Groups
and Speciesa
Group A
Group B
Not Groups A, B, or D
(i.e. Group C, G, and/or F)
Group D (enterococcus)
S. faecalis subsp. liquefaciens
S. faecalis
S. faecium
Total
Group D (not enterococcus)
Numbers of
Municipal
b
1
2
3
1
1
5
1
Streptococcal Isolates From
Waste Hospital Waste
b
b
1
5
b
b
5
1
Viridans
S_. salivarius 2_
Total Viridans Group 5
The Streptococcal groups were identified by the procedure of Facklam (1974) and the
species were identified by the procedure of Pavlova (1972).
None detected.
156
-------
TABLE 11. BACTERIAL NUMBERS IN LEACHATE FROM
UNIVERSITY OF CINCINNATI LYSIMETERS
Bacterial Numbers/ml10 in Leachate From
Leachate Sample
Taken at Week3
4
5
7
8
9
10
11
12
13
14
15
17
c
Lysimeter
A
2.8xl04
2.0xl06
6.9xl05
2 . 5xl06
l.SxlO6
4.3xl05
4.3xl05
7.0xl05
1.4xl06
8.6xl04
3.5xl05
9.7xl05
B
l.SxlO7
2.2xl06
3 . 4xl06
4.2xl06
1 . 8xl06
l.OxlO6
2.7xl06
7.35xl05
5.4xl05
3.9xl05
3.8xl05
2.5xl05
C
5.8xl05
4.7xl07
8.4xl06
5.5xl06
4.0xl06
2.75xl05
2.0xl05
4.0xl05
7.9xl05
1.06xl06
3.2xl05
8.2xl05
D
l.SxlO7
8. 0x10 7
5.7xl06
d
3.4xl05
1.2xl06
3.2xl05
7.1xl05
3.1xl06
2.75xl06
3.5xl06
1.6xl05
E
d
1.6xl07
7.2xl06
4.0xl06
8.3xl05
5.6xl05
4.3xl05
3.2xl05
1.46xl05
2.65xl04
l.OxlO5
5.3xl04
F
d
8 . 5xl06
2.6xl07
1.58xl07
l.OxlO5
1.9xl06
S.lxlO5
1.43xl06
6.3xl06
3.9xl05
3.2xl06
2.8xl06
Weeks after construction of lysimeters.
Determined with plate count agar incubated at 35°C under aerobic conditions.
C
Lysimeter contents: A = sewage sludge
B = municipal solid waste plus sewage sludge
C and D = municipal solid waste
E = municipal solid waste plus hospital waste
P = hospital waste
TJot determined.
157
-------
TABLE 12. NUMBERS OF AEROBIC AND ANAEROBIC
BACTERIA IN LEACHATE FROM UNIVERSITY
OF CINCINNATI LYSIMETERS
Leachate Sample Conditions of
Taken at Weeka Incubat-i on13
4
5
8
9
10
12
13
14
15
17
Aerobic
Anaerobic
Aerobic
Anaerobic
Anaerobic
Aerobic
Anaerobic
Anaerobic
Anaerobic
Aerobic
Anaerobic
Anaerobic
Anaerobic
Aerobic
Anaerobic
Bacterial Numbers/ml0 in Leachate From
Lysimeter
A
1.6x10
1.0x10
1.5x10
1.5x10
8.1x10
7.5x10
6.6x10
2:2x10
5.0x10
1.9x10
6.3x10
3.0x10
4.0x10
4
3
5
5
4
4
3
4
3
5
3
3
4
3.74xl05
3.76xl05
B
4.3xl05
2.6xl08
2.4xl06
1.3xl07
2.1xl06
l.OxlO6
3.1xl04
l.lxlO5
1.3xl05
1.2xl06
l.lxlO5
1.7xl05
6.0xl04
6.3xl04
e
C
2.2x10
2.3x10
1.8x10
4.4x10
3.0x10
7.9x10
1.6x10
1.4x10
3.2x10
6.8x10
8.0x10
4.6x10
1.2x10
7.9x10
9.4x10
5
7
7
7
7
5
6
5
5
5
5
5
5
5
4
1.
6.
1.
6.
2.
1.
3.
2.
5.
2.
5.
2.
1.
1.
3.
D
5x10
9x10
5x10
7x10
8x10
2x10
4x10
1x10
0x10
7x10
6x10
4x10
7
7
7
7
7
5
5
5
4
6
5
5
36xl05
76xl07
IxlO5
E
e
e
l.OxlO7
3.1xl07
1.3xl07
1.4xl05
8.8xl05
1.2xl06
7.4xl04
7.6xl04
S.lxlO5
1.5xl05
6.0xl04
3.0xl04
3.0xl05
F
e
e
2.2xl07
4.5xl07
2.0xl07
l.OxlO5
1.3xl06
l.lxlO5
l.SxlO5
1.2xl05
2.1xl06
l.OxlO6
4.2xl05
6.2xl04
1.56xl05
Weeks after construction of lysimeters.
Incubation at 35°C for 48 hours. The GasPak provided anaerobic conditions.
Q
Determined with blood agar plates.
Lysimeter contents: A = sewage sludge, B = municipal solid waste plus sewage sludge,
C and D = municipal solid waste, E = municipal solid waste plus
hospital waste, F = hospital waste.
"Not determined.
158
-------
TABLE 13. COLIFORM AND STREPTOCOCCAL MPN TITERSa IN LEACHATES
b
FROM UNIVERSITY OF CINCINNATI LYSIMETERS
Weeks
4
5
7
9
11
13
15
17
Total
Coliform
5
< 20
< 20
< 20
< 20
7d
2.2xl02d
1.3xl02d
A
Fecal
Coliform
2
< 20
< 20
< 20
< 20
<20d
1.7xl0ld
< 2d
Leachate MPN
Fecal
Streptococcal
7.9xl02
9.2xl03
9.2xl02
2.4xl03
3.5xl03
5.4xl02
3.5xl02
1.7xl02
Counts :
Total
Coliform
1.4xl05
1.3xl02
1.7xl02
< 20
< 20
8.0x10
< 2d
^
B
Fecal
Coliform
9.4xl04
S.OxlO1
2
< 20
< 20
<20d
< 2d
< 2d
Fecal
Streptococcal
4.9xl05
9.2xl02
9.2xl04
1.6xl04
3.5xl03
9.2xl03
2.3xl03
1.7xl02
aColiform and Streptococcal MPN/100 ml as determined by Standard Methods (1976).
Lysimeter contents: A = Sewage sludge
B = Municipal solid waste plus sewage sludge
CWeeks after Lysimeter construction.
Procedure changed according to Allen et al (1976).
159
-------
TABLE 14. STREPTOCOCCAL GROUP AND SPECIES ISOLATED FROM
LEACHATES OBTAINED THROUGH THIRTEEN WEEKS AFTER
CONSTRUCTION OF THE UNIVERSITY OF CINCINNATI LYSIMETERS
Streptococcal Groups
Numbers of Streptococcal Isolated from Lysimeter
and species
Group A
Group B
Non-group A, B, or D
Group D (enterococcus)
S. faecalis subsp. liquefaciens
S. faecalis
S. faecium
S . durans
Total
A
c
c
c
c
1
3
c
4
B
c
c
c
c
1
5
7
16
C
c
c
c
c -
c
1
3
4
D E
c c
c c
c c
c 4
c 3
c 4
c 1
c 16
F
c
c
c
5
8
c
4
17
Group D (not enterococcus)
Viridans
S. salivarius
The Streptococcal groups were identified by the procedure of Facklam (1974) while the
species were identified by the procedure of Pavlova (1972).
The contents of lysimeters are: A = sewage sludge
B = municipal solid waste plus sewage sludge
C = municipal solid waste
D = municipal solid waste
E = municipal solid waste plus' hospital waste
F = hospital waste
£
None detected at this time.
160
-------
TABLE 15. NUMBERS OF NON-SPORE FORMING;
GRAM POSITIVE; ROD SHAPED BACTERIA
ISOLATED FROM UNIVERSITY OF
CINCINNATI LYSIMETER LEACHATES
Leachate Sample
b
Taken at Week
4
5
Bacterial Numbers/ml in Leachate From
d
Lysimeter
A B C D E F
7 . 5x10 e e e e e
2.2xl04 2.45xl04 9.7xl04 9.2xl04 2.6xl04 l.lxlO5
2.8xl04 6.5xl03 4.7xl04 1.3xl04 S.lxlO4 1.7xl04
13
l.OxlO4 1.59xl04 7.8xl04 4.5xl05 1.6xl04 5.9xl04
17
1.27xl04 5.8xl03 7.87xl04 3.0xl04 2.26xl05 7.0xlQ6
Examples: Corynebacterium sp., Listeria sp., Kurthia sp., etc.
Weeks after construction of lysimeters.
Determined on tellurite blood agar plates incubated for 48 hours at 35°C.
"Lysimeter contents: A = sewage sludge
B = municipal solid waste plus sewage sludge
C and D = municipal solid waste
E = municipal solid waste plus hospital waste
F = hospital waste
a
"Not determined.
161
-------
more complete speciation data so that we
may draw final conclusions as to the ori-
gins of the fecal material in the lysime-
ters. However, at this time eighty-five
species of streptococci were isolated from
these experimental lysimeters, and fifty-
seven species or 67 percent were entero-
cocci. This indicated the presence of
fecal matter in the lysimeter contents,
and thus indirectly the presence of bacte-
rial pathogens. Nevertheless, pathogenic
isolations have not yet been made. How-
ever, Table 15 indicates the presence in
these leachates of diphtheroids of unknown
etiology. Therefore, we will have to delay
final conclusions as to the presence of
pathogens until pathogenic identification
studies are completed.
Fungal (i.e., yeasts and molds) num-
bers were also determined using Sabouraud
agar plates incubated at room temperature
(20 to 22°C), and counted after one week.
Even after 23 weeks, fungal numbers were
still high (see Table 16).
Comparisons were also made of fecal
coliform and fecal streptococci titers to
determine the origin of fecal pollution in
both the solid waste used to construct the
lysimeters and in the lysimeter leachates.
The latter studies (in the leachates) are
not completed at this time, but the re-
sults of the former can be seen in Table
17. Note that the ratios of the sewage
sludge (74) are indicative of pollution
derived from domestic wastes composed of
man's body wastes, whereas both the hospi-
tal and municipal wastes, if one holds to
the ratio figures given in the literature,
are not suggestive of human fecal pollu-
tion. Blannon and Peterson (1974) pointed
out, however, that the FC:FS ratios must
be applied carefully since these correla-
tions may be altered because of the various
ecological factors existing in solid waste
landfills. For example, they noted in
leachates a rapid die-off of fecal coli-
forms and the survival of fecal strepto-
cocci. It was suggested that the use of a
ratio relationship for leachates may be
valid only during the initial leaching
period. Feachem (1975), however, presented
data that showed that the differential
die-away of fecal coliforms and fecal
streptococci can, in fact, strengthen the
value of the FC:FS ratio as a means of
distinguishing human from non-human pollu-
tion. Feachem concluded that initially
high FC:FS ratio values (>4) which fall
indicate human contamination, whereas
initially low ratios (<0.7) which subse-
quently rise suggest a non-human fecal
source. Thus, reliance on the FCtFS ratios
is possible even with differential survi-
val. However, Feachem based his observa-
tions on FCjFS ratios in the water environ-
ment. It would also be significant if his
observations could be extended to the
landfill environment where changes in
FC:FS ratios also occur.
The chemical environment in which
the microbes were found was delineated to
evaluate how chemical composition might
affect microbial numbers and types. An
example of the results showing the para-
meters evaluated is presented in Figure 5
for lysimeter E. Declining trends in the
chemical parameters studied are apparent,
but it is too soon to conclude what effect
the chemical content of the leachates had
on the microbial populations of the lysi-
meters.
CONCLUSIONS
Based on the above information, it
can be concluded that:
1. A limited number of bacterial
pathogens have been found in
leachates from commercial and
experimental landfills, and
environmental lysimeters.
2. Total and fecal coliforms may not
be acceptable indicators of fecal
pollution after the first month
or two of the landfill, since
pathogens have been recovered
from leachates with low or no
total or fecal coliform numbers.
Newer procedures for coliform
recovery may indicate the pre-
sence of larger numbers.
3. The fecal streptococcal test
still remains an attractive index
of fecal (and pathogenic) pollu-
tion of leachates.
4. Leachate toxicity interferes
with the isolation of microbes.
162
-------
TABLE 16. FUNGAL NUMBERS ISOLATED FROM
UNIVERSITY OF CINCINNATI
LYSIMETER LEACHATES
Fungal Numbers/ml in Leachate From
Taken at Week3 Lysimeter
A B C D E
5 2.0xl04 S.OxlO4 l.SxlO4 S.OxlO5 < 10
13 IxlO3 1.3xl05 c 4-OxlO5 4.6xl04
15 5xl03 1.6xl04 c 1.2xl04 2.0xl04
F
3.0xl04
7.0xl04
l.SxlO4
23 1.4xl04 3.2xl04 l.SxlO4 1.13xlQ5 l.lxlO5 l.OxlQ5
Weeks after construction of lysimeters.
Determined on Sabouraud agar plates incubated at room temperature (20 to 22°C).
Q
Not determined.
163
-------
TABLE 17. COMPARISON OF FECAL COLIFORM AND
FECAL STREPTOCOCCI TITERS TO DETERMINE
THE ORIGIN OF FECAL POLLUTION OF SOLID
WASTE IN UNIVERSITY OF CINCINNATI
LYSIMETERS
Type of
Solid Waste
Sewage sludge
Hospital waste
Municipal waste
Fecal Coli form/Fecal Streptococci Ratios
2.3xl010
0. JO
3.3x10
9.0X1010
11
1.1x10
4.65X1010 1Q
2.5xlOU
aRatios of MPN values as described by Geldreich e_t al. (1964).
164
-------
cn
en
i-s
G. o-
Q O
3 O
n
CD
f
TJ
X
FIGURE 5
Chemical Ana ysis of Leachates from Laborator L simeterE
CQQ
Phosphate^
Conductance
• -a-
Total Solids^
Q> •••••Q D«
Volatile Sol ids,
o g
_L
8 9 10 11 12 13
WEEKS
Post Lysimeter Construction
±
o
o
hs
D)
a
8
14 15 16 17
-o
0)
E
D
•Si
D
~a
o
L§
i
o>
89
-------
by the standard plate count and blood
agar plates generally decreased as
disposal time increased. Fungal counts,
however, remained relatively constant.
ACKNOWLEDGMENTS
This research was supported by the
U. S. Environmental Protection Agency
Grant //R-804733. The authors acknowledge
the excellent technical assistance of
Ms. Mary Lee Zink, Ms. Sandra Cronier,
Ms. Edna McKay, and Mr. William Held.
REFERENCES
Allen, M. J., R. H. Taylor, E. F. Geld-
reich. 1976. The Impact of
Excessive Bacterial Populations on
Coliform Methodology. Am. Water
Works Assoc. Water Quality Tech-
nology Conference, San Diego,
Calif., Dec. 6 & 7, 1976.
Blannon, J. C. and M. L. Peterson. 1974.
Survival of Fecal Coliforms and
Fecal Streptococci in a Sanitary
Landfill. News of Environmental
Research in Cincinnati, April 12,
1974. U. S. Environmental Pro-
tection Agency, Cincinnati, OH.
4 pp.
Bordner, R., J. Winter, and P. Scarpino
(eds.). 1978. Microbiological
Methods for Monitoring the Environ-
ment, Water and Wastes. EPA-600/8-
78-017, U. S. Environmental Pro-
tection Agency, Cincinnati, OH.
338 pp.
Brunner, D. R. 1974. U. S. Environmental
Protection Agency, Personal Com-
munication.
Classification of Etiologic Agents on the
Basis of Hazard. 1976. Public
Health Service, U. S. Department of
Health, Education, and Welfare,
Atlanta, Georgia. 13 pp.
Cooper, R. C., S. A. Klein, C. J. Leong,
J. L. Potter, and C. G. Golueke.
1974. Final Report: Effect of
Disposable Diapers on the Composition
of Leachate from a Landfill. SERL
Report No. 74-3, University of
California, Berkeley. 97 pp.
Engelbrecht, R. S. 1973. Survival of
Bacteria in a Simulated Sanitary
Landfill. A Research Report Pre-
pared for the Tissue Division of
the American Paper Institute. Pre-
sented at the Water Resources
Symposium Number Seven. University
of Texas, April 1-3, 1974.
Engelbrecht, R. S., M. J. Weber, P.
Amirhor, D. H. Foster, and D. LaRossa.
1974. Biological Properties of
Sanitary Landfill Leachate. In:
Virus Survival in Water and Waste-
water Systems, Water Resources
Symposium, Number Seven (J. F.
Milana, Jr., and B. P. Sagik, eds.).
Center for Research in Water
Resources, University of Texas,
Austin, pp. 201-217.
Facklam, R. R., J. F. Padula, L. G. Thacker,
E. C. Wortham, and B. J. Sconyers.
1974. Presumptive Identification of
Group A, B, and D Streptococci.
Appl. Microbiol., 27:107-113.
Feachem, R. 1975. An Improved Role for
Faecal Coliform to Faecal Strepto-
cocci Ratios in the Differentiation
Between Human and Non-human Pollution
Sources. Water Res., 9:689-690.
Geldreich, E. E., H. F. Clark, and C. B.
Huff. 1964. A Study of Pollution
Indicators in a Waste Stabilization
Pond. J. Water Poll. Cont. Fed.,
36:1372-1379.
Glotzbecker, R. A. 1974. Presence and
Survival in Landfill Leachates and
Migration through Soil Columns of
Bacterial Indicators of Fecal Pollu-
tion. Masters thesis, University of
Cincinnati. 122 pp.
166
-------
Litsky, W., W. L. Mallmann, and C. W.
Field. 1953. A New Medium for the
Detection of Enterococci in Water.
Amer. J. Pub. Health, 43:873-879.
Pavlova, M. T., F. T. Brezenski, and W.
Litsky. 1972. Evaluation of Various
Media for Isolation, Enumeration and
Identification of Fecal Streptococci
From Natural Sources. Health Lab.
Sci., 9:289-298.
Peterson, M. L. 1971. Pathogens Associ-
ated with Solid Waste Processing.
Open-file Report SW-49r, U. S.
Environmental Protection Agency.
Peterson, M. L. 1974. Soiled Disposable
Diapers: A Potential Source of
Viruses. Amer. J. Pub. Health,
64:912-914.
Pohland, F. G., and R. S. Engelbrecht.
1976. Impact of Sanitary Landfills:
An Overview of Environmental
Factors and Control Alternatives.
Prepared for American Paper Institute.
82 pp.
Standard Methods for the Examination.of
Water and Wastewater. APHA, AWWA,
WPCF, Washington, D. C. (14th ed.,
1976).
Wolf, P. L., B. Russell, A. Shimoda. 1975.
Practical Clinical Microbiology and
Mycology: Techniques and Interpreta-
tions. John Wiley & Sons, New York.
167
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GAS AND LEACHATE: SUMMARY
Vijay P. Patel, Robert L. Hoye
and
Richard 0. Toftner
PEDCo Environmental, Inc.
Cincinnati, Ohio 45246
ABSTRACT
Gas and leachate present a principal challenge to design and operation of sanitary
landfills. Our knowledge of the behavior and characteristics of these contaminants is
continually expanding and more effective ways to apply this knowledge are being found.
Considerable variation exists in the physical processes affecting the fate of contaminants
in different circumstances thus contributing to the difficulty in designing safeguards to
the environment. For example, the harmful effects of leachates may be attenuated by some
soils, but to rely upon soil properties as a sole design measure may be risky.
The variations in the properties of leachate and gas and the physical conditions
under which they are generated and exist also complicates the design of collection and
treatment devices that would lessen the harmful effects. Without knowing the precise
parameters to design for, presents a risk of either over-designing or under-designing. In
the first case excessive costs may be involved; in the latter, costs may be expended only
to have the contaminants harm the environment anyway. This issue will become even more
important as the Resource Conservation and Recovery Act provisions are promulgated and
enforced for sanitary landfills.
Development of other answers and more precise application of the knowledge as it
emerges must therefore continue. This paper discusses some of the past and current work
and consolidates some findings of EPA to date. Even now the work is continuing and
further breakthrough in the control and treatment of gas and leachate associated with
sanitary landfills can be expected.
LANDFILL LEACHATE
Leachate is generated when water
enters the landfill, percolates through it,
and picks up soluble materials, some of
them soluble products of biological and
chemical reactions. Water can enter a fill
by such means as precipitation or by
drainage of floodwaters, springs, or ground-
water into the fill. Therefore, sites are
selected and sanitary landfills should be
designed and constructed to avoid the
intrusion of water.
Volume and Composition of Leachate
The volume of leachate produced depends
on many factors, but is generally deter-
mined by the extent to which surface water
infiltrates or groundwater is intercepted.
The composition of leachate varies
widely and also depends on many factors
such as the composition and age of the
solid waste, temperature, and the amount of
available oxygen. Commonly, there is
little control over the quantity and
characteristics of the input solid waste,
so it is not surprising that output char-
acteristics are so highly variable. Table
1 shows the range of compositions of leach-
ates from sanitary landfills.
Examination of Table 1 leads to the
following observations. Leachate is
generally high in biologically oxidizable
organics and total solids. Concentrations
of heavy metals are generally less than 1
milligram per liter, but zinc occurs often
in concentrations of 100 milligram per
liter or more. Iron concentrations of 1000
168
-------
TABLE 1. COMPOSITION OF TYPICAL LEACHATES
FROM SANITARY LANDFILLS1
(mg/liter except pH value)
Constituent
Iron
Zinc
Phosphate
Sulfate
Chloride
Sodium
Nitrogen
Hardness (as CaC03)
COD
Total residue
Nickel
Copper
PH
Concentration range
200- 1,700
1- 135
5- 130
25- 500
100- 2,400
100- 3,800
20- 500
200- 5,250
100-51,000
1,000-45,000
0.01-0.8
0.10-9.0
4.00-8.5
milligrams per liter are common. Leachate
derived from recently deposited solid waste
is generally acidic, whereas the pH level of
more stabilized solid wastes generally is
near 7.
The biological properties of leachate
have also been investigated, the studies
focusing primarily on the density of total
plate count bacteria, total coliforms, fecal
coliforms, and fecal streptococci. 2--> The
data indicate a significant bacterial
population associated with sanitary landfill
leachate and also show a drastic reduction
in the density of the bacteria with time of
operation or with time of leaching. This
decrease in density may result from adverse
environmental conditions prevailing in the
landfill.6
Migration of Leachate
From a technological point of view, the
most difficult problem associated with
design of a sanitary landfill is to predict
the migration of contaminants in the soil.
Computer simulation models have been devel-
oped to predict the movement of leachate
through a landfill.7 The fate of con-
taminants carried in solution and suspen-
sion is affected by physical processes,
such as filtration, dispersion, and mixing,
and by chemical processes in the soil, such
as ion exchange, adsorption, and oxidation
and reduction.
Mechanical filtration by soil is an
effective process. Most suspended matter
and a substantial number of microorganisms
are removed from leachate after a few
meters of travel through a fairly coarse,
sandy soil. Although dispersion can reduce
the concentration of pollutants in solution,
it cannot be relied upon as a means of con-
taminant removal. Because of their large
cation exchange capacity (CEC), and surface
area, the clay minerals, e.g. montmorillon-
ite, illite, kaolinite, chlorite, and
vermiculite, are the most important frac-
tions of -soil in attenuating contaminants
carried in leachate. Another important
fraction is the hydrous iron oxide coatings
on soil properties; this fraction is
particularly effective in retaining metallic
pollutants. Recent investigation8 has led
to the conclusion that passage of leachate
through a calcium-saturated clay material
will result in high attenuation of the
heavy metals; moderate attenuation of
potassium, ammonium, magnesium, and silicon;
and relatively low attenuation of chlorine,
sodium, and water-soluble organic compounds.
In addition to the clay and iron
oxide related attenuation of pollutants in
leachate, physical adsorption on surfaces
is an important removal mechanism, partic-
ularly as regards bacteria and viruses.
Again, the clay minerals are the most
important fraction of soil.
This brief discussion of the attenua-
tion process should indicate the complexity
of the system and 'the difficulty of pro-
ceeding from a bas-ic understanding of the
system to a quantitative prediction of
attenuation.
Environmental Effects of Leachate
Assessment of the environmental effects
of leachate on surface and groundwaters
indicates that pollution can occur unless
adequate controls are provided during site
selection and during the design, operation,
surveillance, and long-term maintenance of
a sanitary landfill. Detrimental effects
of leachate on the environment include
169
-------
contamination of water supplies, fish kills
in nearby streams, and loss of livestock.
In numerous reported instances, leach-
ate has contaminated the surrounding soil
and polluted an underlying groundwater
aquifer or nearby surface water. The
following are recent examples. Private
wells located 300 meters downstream from
the Llangollon landfill (completed and
closed in 1968) in New Castle County,
Delaware, were heavily polluted and sub-
sequently abandoned. The municipal water
supply from Geneseo, Illinois, was polluted
by leachate from a garbage dump located
about 500 meters north of the well field.
Private wells located about 200 meters from
a landfill in Kane County, Illinois, showed
bacterial and chemical pollution.
Control and Treatment of Leachate
In many areas of the country, signifi-
cant amounts of leachate are generated and
few attenuating mechanisms are present.
Systems have been developed for collecting
and treating leachate in these less-than-
ideal situations. Most collection systems
utilize some type of impervious or highly
impermeable liner.
Installation of an impermeable liner
in a sanitary landfill to prevent leachate
from polluting ground and surface waters is
relatively recent development. Although
laboratory studies have simulated field
conditions in a sanitary landfill, little
is known of the long-term effects of exposing
liners to the many physical, chemical, and
biological processes taking place within
the landfill. The materials used as liners
include compacted natural clay soils, com-
pacted natural soils with bentonite added,
asphaltic materials, and artificial mem-
branes.
In one study, polymeric membranes and
admix materials were exposed to sanitary
landfill leachate, as shown in Table 2.9
After 1 year of exposure to leachate,
most of the liner materials that were eval-
uated showed relatively minor deterioration.
In no case was there a significant increase
in water permeability. The polymeric
membranes swelled and softened to various
degrees, but did not become permeable. The
admixed materials, such as soil, asphalt,
and asphaltic concretes, showed significant
loss of compressive strength but no increase
in permeability. These results indicate
that projections of the lifetime of the
various liners when in contact with leachate
must be based on much longer exposures.
Once leachate has been collected, it
must be treated before it can be released.
Treatment of leachate can be realized by:
0 Recirculating the leachate back
TABLE 2. LINER MATERIALS SELECTED FOR LEACHATE EXPOSURE TESTS'
Material
Thickness,
millimeters
Polymeric liner membranes:
Polyethylene (PE)
Polyvinyl chloride (PVC)
Butyl rubber
Chlorosulfonated polyethylene,
with fabric reinforcement
Ethylene propylene rubber (EPDM)
Chlorinated polyethylene (CPE)
Admix materials:
Paving asphalt concrete
Hydraulic asphalt concrete
Soil cement
Soil asphalt
Bituminous seal
Emulsion asphalt or fabric
0.10
0.20
0.63
0.34
0.51
0.32
55.88
60.96
114.30
101.60
7.62
7.62
170
-------
into the landfill to enhance
anaerobic biological removal of
the pollutants.
0 Treating it with other wastes at
a municipal wastewater treatment
plant.
0 Constructing a separate treatment
unit at the landfill site.
When leachate is recirculated, it is
applied to the top of the fill by surface
irrigation. As a result, the moisture con-
tent of the solid waste is increased and
presumably reaches an optimum level for
anaerobic biological stabilization. In
this treatment, the leachate is stabilized
at a rate equal to that of the solid waste
itself, with the solid waste functioning as
an anaerobic trickling filter.
We have very little information on the
combined treatment of leachate with domestic
wastewater. One reportlO states that
leachate with a COD of 10,000 milligrams
per liter can be added to domestic waste-
water in an extended aeration activated
sludge unit at a level of at least 5 per-
cent by volume without seriously impairing
the effluent quality.
Construction of a separate on-site
treatment unit is the most expensive method
of treating leachate. Leachate is amenable
to biological as well as physical-chemical
treatment processes. Following a recent
study at the University of Illinois, Chian
and DeWalleU concluded that biological
treatment methods, such as use of anaerobic
filters, aerated lagoon, and combined
treatment, are most applicable for treating
leachate from recently constructed landfills,
whereas physical-chemical treatment methods,
such as activated carbon adsorption, chem-
ical precipitation, chemical oxidation, and
reverse osmosis, are best applied to treat-
ment of leachate from more stabilized solid
was te.
Because the magnitude of any leachate
problem depends on many variables, the
effects of leachate collection and treatment
on the cost of sanitary landfill operations
are highly site-specific.
Chian and DeWalle-'-^ found that aerated
lagoons provide the least expensive method
of treating leachates having comparatively
low BOD5 values, (e.g. 5000 mg/liter) and
relatively high flowrates (e.g., 1.26
liters per second). As the BOD^ level of
the leachate increases at the same high
flowrate, the cost of treatment with
anaerobic filters becomes increasingly
attractive, and at a BOD5 value of 25,000
milligrams per liter it equals that of the
aerated lagoon process when credit is
deducted for the methane gas produced.
Treatment of leachate in aerated lagoons
and by physical-chemical treatment pro-
cesses is most effective, although such
treatment would cost more than combined
treatment of leachate and domestic waste-
water with activated sludge at high leachate
flowrates and low BOD5 levels. The cost
estimates are summarized in Table 3.
LANDFILL GAS
Gas is a natural decomposition product
resulting from the microbial degradation of
solid waste. Although such degradation
produces a variety of gases, methane and
carbon dioxide are the major gaseous pro-
ducts of landfill decomposition. Migration
of gas produced in a landfill may lead to a
variety of effects on the environment,
ranging from persistant problems with
repugnant odors to the accumulation and
explosion of high concentrations of methane.
Because of the potential problems, both the
production and migration of gas are impor-
tant considerations in selecting a site and
operating a landfill.
Volume and Composition of Landfill Gas
Gases generated from the stabilization
of landfilled solid waste are the result of
microbial degradation of the organic
matter present in the waste. Although
aerobic processes occur initially, faculta-
tive and anaerobic processes, gradually
replace them as the oxygen in the waste is
depleted. Because of this shift in pro-
cesses, there is a corresponding shift in
gas composition. Carbon dioxide is pro-
duced in large quantities initially, and
its production peaks in 2 weeks to 2 months,
then falls until a stable plateau is
achieved.l^ Xn contrast, methane may take
from months to many years to reach peak
production.
The rate of gas production increases
with increasing moisture content and temper-
ature of the solid waste; the production
rate decreases with increasing density of
the waste.14 other factors affecting gas
production include the pH level, nutrient
conditions, and metals content.
171
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TABLE 3. SUMMARY OF COST ESTIMATES FOR LEACHATE TREATMENT
12
Influent BOD, mg/ liter
Activated sludge (AS)
(Combined treatment)
Aerated lagoon (AL)
Anaerobic filter (AF)
AL-sand filter (SF)
-activated carbon (AC)
AL- SF-AC-Rever s e
Osmosis (R0)b
AF-SF-AC
AF-SF-AC-ROb
Leachate
f lowrate,
liters/sec
1.26
0.13
1.26
0.13
1.26
0.13
1.26
0.13
1.26
0.13
1.26
0.13
1.26
0.13
Typical
effluent COD,
mg/liter
25,000
30
30
500
500
1500
1500
125
125
25
25
375
375
75
75
5,000
30
30
100
100
300
300
25
25
5
5
75
75
15
15
Costs of treatment,
$/1000 liters leachate
25,000
6.13
10.92
4.72
8.34
5.83 (4.72)a
11.35 (10.24)
6.78
10.53
7.28
11.77
8.65 (7.55)
14.30 (13.2)
9.16 (8.02)
15.54 (14.33)
50,000
1.58
3.14
1.08
2.64
1.79 (1.55)
4.67 (4.43)
1.92
3.61
2.42
4.85
2.79 (2.56)
5.80 (5.57)
3.3 (3.03)
7.04 (6.70)
Numbers in parenthesis indicate the costs of treatment after deducting credit for methane
produced at $5.35/100 m3.
After RO treatment the total dissolved solids (TDS) decreased to 300 mg/liter and 60 mg/
liter at influent leachate BOD concentrations of 25,000 mg/liter and 5,000 mg/liter,
respectively.
Many and highly variable gas produc-
tion rates have been reported;!^ the varia-
tion is mainly attributable to: (1) methods
of data collection, (2) differences in
theoretical assumptous and calculations,
and (3) differences in the waste itself.
Methane, carbon dioxide, hydrogen, and
nitrogen are the major components of
landfill gas. Minor components include
argon, hydrogen sulfide, sulfides, disul-
fides, and an assortment of organic gases
in trace amounts. Typical composition of
landfill gas is presented in Table 4. As
with production, the gas composition varies
widely and is influenced by the same
parameters.
Migration of Landfill Gas
Landfill gases may migrate consider-
able distances from the landfill through
the surrounding soil. Because gas genera-
tion is not limited to the active life of
the filling operation but continues for a
period of years, gas control is a very
important design consideration.
TABLE 4. RANGE OF LANDFILL
GAS COMPOSITION^, 14
(percent)
Methane
Carbon dioxide
Nitrogen
Hydrogen
Oxygen
40-60
30-60
0-30
<1
0-20
Gases migrate in all directions from
the fill as a result of both pressure and
diffusional flows. The gases move in the
direction of decreasing pressure, and
diffuse because of gradients in gas con-
centrations. In early attempts to model
172
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gas flow from a landfill the investigators
recognized that the flow of gases around a
landfill consists of a mixture of different
gas types, but they accounted for this only
indirectly. Recent work at the Ohio State
University has been aimed toward more
rigorous solutions to be incorporated into
a user manual for design application. The
work by Moore and others has provided
techniques for predicting time-concentra-
tion profiles, computer programs for
analyzing specific situations, design
charts that may be used to estimate migra-
tion, and design criteria for control
devices.15
Environmental Effects of Landfill Gas
The three main environmental effects
associated with production of gas from
decomposing solid waste are: the escape of
odorous gases, fire and explosions due to
accumulations of methane, and damage to
vegetation on adjacent land. Although the
major components of landfill gas are odor-
less, minor constituents such as hydrogen
sulfide are extremely malodorous. Such
gases can migrate from the fill and accumu-
late in structures, making them unpleasant
and even dangerous to inhabit or work in.
In concentrations ranging from 5 to 15
percent by volume, methane is explosive in
the presence of oxygen. Reports of fires
and explosions resulting from accumulations
of methane from landfills include incidents
involving loss of life. Explosions in
Georgia (1967) and North Carolina (1969)
caused the deaths of five men.13 These
explosions were traced to the migration of
methane from landfills and its subsequent
accumulation in structures the men were
occupying. In addition to the explosion
hazard, methane also tends to displace
oxygen and thus can cause asphyxiation.
A number of cases of adverse effects
on vegetation caused by intrusion of land-
fill gases have been reported. Flower re-
ported three cases in New Jersey involving
injury and death of peach trees, ornamentals,
and commercial crops.16 These cases were
associated with the decomposition of munic-
ipal solid waste deposited in worked-out
sand and gravel pits, a situation that
would tend to promote gas migration.
Flower concluded in another report that
soil characteristics, modified by landfill
gas included moisture content and available
ammonia-nitrogen, iron, manganese, zinc,
and copper - all of which he found to be
significantly increased by the presence of
landfill gases.17 Flower also found a high
negative correlation between plant growth
and concentrations of methane and/or carbon
dioxide in the root atmosphere.
An additional environmental effect of
landfill gas is the potential for carbon
dioxide to dissolve in groundwater and thus
to reduce the pH level through the forma-
tion of carbonic acid. Acidic groundwater
is more susceptible to mineralization when
it comes into contact with acid-soluble
formations. The water may then be unfit
for human consumption or for some industrial
uses unless it is further treated.
Control of Landfill Gas
Vents and barriers are the two general
types of control devices that can be used
to control or prevent gas migration and
thus protect nearby structures and vegeta-
tion. Vents provide an escape route for
the gas, usually through trenches or pipes
filled with gravel and open to the atmo-
sphere. Barriers prohibit the movement of
gas through an area limited by an imperme-
able material. Hybrid systems, which com-
bine the mechanisms of vents and barriers,
are also used. These gas control systems
may be designed and installed before opera-
tion of the landfill or may be added on to
control or alleviate a gas migration pro-
blem.
Pipe vents can relieve localized accu-
mulations of gas in a sanitary landfill.
Normally some type of convective flow must
be introduced if pipe vents are to be
effective. Likewise, a trench vent may be
designed to vent naturally to the atmosphere
or to undergo forced convection by mechan-
ical pumping in either the exhaust or re-
charge mode.
A barrier can control gas migration
only if it extend? downward to another
impervious material. Natural and synthetic
impervious materials are used to line
landfills to control gas migration. Both
field experience and computer simulation
suggest that passive vent systems (wells,
trenches etc.) will relieve pressure but
will not prevent migration due to concen-
tration gradients.
Systematic monitoring of gas concen-
trations and movement is essential to
determine the effectiveness of a control
device and to ensure that gases do not
173
-------
accumulate to high levels,
Recovery and Utilization of Landfill Gas
Municipal solid waste disposal sites
are untapped sources of methane gas. Land-
fill gas, which is mainly produced during
anaerobic decomposition, has a volume com-
position of 40 to 60 percent methane.
Other gases produced are carbon dioxide,
nitrogen, and hydrogen sulfide. Table 5
shows the average gas composition obtained
at the Mount View study site.
TABLE 5. AVERAGE GAS COMPOSITION
AT MT. VIEW STUDY SITE
18
Constituent
Methane
Carbon dioxide
Nitrogen
Oxygen
Volume %
44.0
34.2
20.8
1.0
The amount of recoverable gas depends
upon two factors: the ultimate gas pro-
duction and the area-depth relationship.
Ultimate gas production values have ranged
from 0.003 to 0.43 scm/kg of refuse.19
These estimates include lysimeter studies
conducted at optimal conditions and include
the addition of sewage sludge to municipal
refuse. It is estimated that 0.15 scm of
raw landfill gas per kilograms of refuse
will be obtained at Mt. View. Since this
raw landfill gas is 44 percent methane,
0.07 scm of methane per kilogram of refuse
will be obtained.
The other factor concerns the area-
depth relationship. Because of the possi-
bility of air infiltration, a deeper land-
fill is preferred to a shallow landfill,
even though volume is constant. If air
infiltrates into the landfill, methane pro-
duction will cause or decline to a level
where the methane content of the raw gas is
too low for economic recovery. The Mt.
View site is 12 meters deep and has had
problems maintaining high pumping rates
(5.6 m3/min). Pumping has been reduced to
1.4 m3/min and a stable methane content of
44 to 45 percent has been achieved. This
problem has been directly attributed to the
infiltration of air from the higher pumping
rate. At the higher rate, landfill condi-
tions went from anaerobic to aerobic decom-
position and the volume of methane dropped
from 44 to 30 percent. The landfill re-
quired 2 months before anaerobic conditions
were reestablished.20 Deeper landfills (30
to 42 meters) in the Los Angeles area do
not appear to have this air infiltration
problems.
The heating value of raw landfill gas
is approximately 16.9 x 10 kJ/scm. Depend-
ing on final use, landfill gas may be need-
ed to be upgraded. At the Mt. View project,
the landfill gas will be compressed, dehy-
drated, and stripped of carbon dioxide to
produce a gas with a heating value 24.4 x
103 kJ/scm. This gas will then be fed into
a Pacific Gas and Electric Company main
transmission line for distribution to resi-
dential and industrial customers.
Cost estimates for collection and
treatment, indicates that landfill gas,
while not presently competitive with natural
gas or oil, is competitive with LNG or
SNG. Thus, landfill gas can be an important
supplemental or alternative fuel source.
REFERENCES
1. Steiner, R.C., A. A. Fungaroli, R. J.
Schoenberger, and P. W. Purdom.
Criteria for Sanitary Landfill Develop-
ment. Public Works, 103(3):77-79,
1971.
2. Cooper, R.C., et al. Virus Survival in
Solid Waste Treatment Systems In:
Virus Survival in Water and Wastewater
Systems, J. F. Malina and B.P. Sagik
(Eds.) Water Resources Symposium No.
7, Center for Research in Water Re-
sources, The University of Texas,
Austin, Texas. 218. 1974.
3. Engelbrecht, R. S., et al. Biological
Properties of Sanitary Landfill Leach-
ate, In: Virus Survival in Water and
Wastewater Systems, J.F. Malina and B.
P. Sagik (Eds.). Water Resources
Symposium No. 7. Center for Research
in Water Resources, The University of
Texas, Austin, Texas. 201. 1974.
4. Quasim, S. R., and J. C. Burchinal.
Leaching from Simulated Landfills.
Journal Water Pollution Control Fed-
eration, 42, 371. 1970.
5. Blannon, J. C., and M. L. Peterson.
Survival of Fecal Coliforms and Fecal
Streptococci in a Sanitary Landfill.
174
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10.
11.
12.
13.
14.
U.S. Environmental Protection Agency,
Cincinnati, Ohio, Unpublished Report:
News of Environmental Research in
Cincinnati, April 12, 1974.
Engelbrecht, R. S. , and P. Amirhor. 15.
Biological Impact of Sanitary Landfill
Leachate on the Environment. Presented
at Second National Conference on
Complete Water Reuse, American Institute
of Chemical Engineers. Chicago,
Illinois. 1975.
16.
Freeze, R. A. Subsurface Hydrology at
Waste Disposal Sites. IBM Journal of
Research and Development, 16(2): 117-
129. 1972.
Griffin, R. A., and N. F. Shimp.
Draft Report, Attenuation of Pollutants
in Municipal Landfill - Leachate by 17.
Clay Minerals. Illinois State Geo-
logical Survey, Urbana, Illinois.
Prepared for Solid and Hazardous Waste
Research Division, Cincinnati, Ohio.
Contract No. 68-03-0211. 1978.
Haxo, H. E. Evaluation of Liner
Materials Exposed to Leachate
Materials. Research and Development 18.
Corporation, Oakland, California.-
EPA/600/2-76/255. U.S. Environmental
Protection Agency, Cincinnati, Ohio.
1976.
Boyle, W. C., and R. K. Ham. Bio- 19.
logical Treatability of Landfill
Leachate. Journal Water Pollution
Control Federation. 46,860. 1974.
Chian, E. S. K., and F. B. DeWalle. 20.
Sanitary Landfill Leachates and Their
Treatment. Journal Environmental
Engineering Division. ASCE. 102,
411. 1976.
Chian, E. S. K., and F. B. DeWalle.
Evaluation of Leachate Treatment.
Volume II. EPA-600/2-77-1866. U.S.
Environmental Protection Agency, Cin-
cinnati, Ohio. November 1977.
Rhyne, C.W. Landfill Gas. Internal
Report. Office of Solid Waste Manage-
ment Programs. U.S. Environmental
Protection Agency, Cincinnati, Ohio.
April 4, 1974.
DeWalle, F.B., E.S.K. Chian, and E.
Hammerberg. Gas Production from Solid
Waste in Landfills. Journal of the
Environmental Engineering Division.
Proceedings of the American Society of
Civil Engineers. Volume 104, No. EE3.
June 1978.
Moore, C.A., and I.S. Rai. Design
Criteria for Gas Migration Control
Devices. In: Proceedings of the Third
Annual Municipal Solid Waste Research
Symposium. St. Louis, Missouri.
March 14 through 16, 1977.
Flower, F.B., I.S. Leone; E.F. Oilman,
and J.J. Arthur. Landfill Gases and
Some Effects on Vegetation. In:
Proceedings of the Conference on
Metropolitan Physical Environment.
Syracuse, New York. August 25 through
29, 1975.
Flower, F.B., I.A. Leone; E.F. Oilman,
and J.J. Arthur. A Study of Vegetation
Problems Associated with Refuse Land-
fills. Solid and Hazardous Waste
Research Division. U.S. Environmental
Protection Agency, Cincinnati, Ohio.
Grant No. R803762-02. Draft Report.
1978.
Blanchet, M.J. et al. Treatment and
Utilization of Landfill Gas - Mount
View Project Feasibility Study. Pub-
lication No. SW-583. U.S. Environmental
Protection Agency, Washington, D.C.
Dair, F.R. Methane Gas Generation
from Landfills. American Public
Works Association Reporter. March
1977. pp. 20-23.
Carlson, J.A. et al. Recovery of
Landfill Gas: Engineering Site Study -
the Mount View Project. Publication
No. SW-587. U.S. Environmental Protec-
tion Agency. Washington, D.C.
175
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ANALYTICAL METHODS EVALUATION
FOR APPLICABILITY IN LEACHATE ANALYSIS
Foppe B. DeWalle
Theo Y. Zeisig
University of Washington
Seattle, Washington 98195
and
Edward S.K. Chian
Georgia Institute of Technology
Atlanta, Georgia 30332
ABSTRACT
This study conducted a round robin analysis of 10 leachate samples that
were analysed by 32 laboratories located in the United States and Canada. The
laboratories analysed for up to 28 constituents to include physical parameters,
organics, anions and cations. The study found that the overall coefficients of
variation varied between 32% for the chemical oxygen demand to as high as 210%
for the cadmium determination. Significant differences were noted between
results from colorimetric methods and titrimetric and physical methods. Results
obtained with automated methods generally deviated from other methods. The
average recovery of spiked parameters in one leachate sample was 81% but varied
widely for individual parameters. These findings point to the necessity of
using the standard addition technique to determine the matrix depression or
enhancement for each leachate sample. Splitting samples between laboratories
is also highly recommended as between laboratory variation is more significant
than within laboratory variation.
INTRODUCTION
Municipal solid waste is primarily into the surrounding soil and pollute
disposed of in sanitary landfills. While groundwaters and nearby aquifers. The
such a disposal method is optimum from assessment of the environmental impact
a public health standpoint, it can have of leachate requires the accurate and
adverse effects on the environment unless consistant determination of a substan-
sound engineering principles are used tial number of groundwater contaminants.
during design, operation and longterm An earlier study by Chian and DeWalle
maintenance of the solid waste fill. (1975) tested the standard addition
Infiltrating rainwater will dissolve technique for 29 parameters in a con-
organic and inorganic substances from centrated leachate sample. Several
the fill. This leachate may than migrate methods, especially those based on
176
-------
colorimetric methods, showed strong inter-
ferences due to the color and suspended
solids present in the leachate. The
present study conducted a round robin
analysis of 10 leachate samples that
were analysed by 32 laboratories for
28 constituents, to determine the
analytical variability of each method.
DATA AND ANALYSIS
A total of 120 laboratories that
were routinely conducting leachate
analysis, were contacted to learn about
their interest in participating in a
round robin study. Fifty two laborator-
ies indicated their willingness to par-
ticipate, among which Federal and State
laboratories were best represented
(60%) followed by commercial (20%)
and university (20%) laboratories.
Large leachate or polluted ground
water samples were subsequently
collected at nine sites in the US
and Canada. Four of these were full
scale landfills, two were pilot scale
landfills while three were laboratory
scale solid waste lysimeters as shown
in Table 1. The COD strength ranged
from 98 to 27,284 mg/1. These values
were close to the estimated value
submitted to each laboratory ahead
of time and therefore greatly aided
in the selection of the right dilution.
Thirty two of the fifty two labora-
tories completed the analysis of the
TABLE 1. LEACHATE COLLECTION LOCATIONS AND INITIAL ANALYTICAL RESULTS
~~~ ~ " " ~Estimated Measured
COD COD
Location Well/Drain Symbols (mg/g.) (mg/&)
Center Hill,
Cincinnati, Ohio
Enfield, Connecticut
Tellytown,
Pennsylvania
Llangollen,
Delaware
Univ. of Illinois,
Urbana, Illinois
Univ. of Illinois,
Urbana, Illinois
Boon County,
Kentucky
Univ. of British
Columbia, Vancouver,
British Columbia
Sonoma County,
California
Dade County, Miami,
Florida
Lysimeter Cell 16 A 30,000 27,284
Chlorine Brine
Drainpipe
Groundwater Well 26 B 30,000 2,168
Combined leachate C 23,000 16,084
Influent
Groundwater Well S 1 D 10,000 10,719
Lysimeter Drainpipe E 7,500 3,408
(spiked)
Lysimeter Drainpipe F 5,000 2,047
Test Cell Upper G 3,000 945
Drainpipe
Lysimeter Cell K H 1,800 1,298
Drainpipe
Test Cell D Recycle I 700 423
Drainpipe
Groundwater Well 4-20 J 100 98
177
-------
10 leachate samples, although not all
parameters were tested by all laborato-
ries. The least reported parameters
were the oxidation reduction potential
( 11 laboratories ), reflecting the
anaerobiosis of the sample and the
volatile acids ( 12 laboratories )
indicating the extend of the cellulose
decomposition and subsequent methane
fermentation.
The data were evaluated using the
analysis of variance with the laborato-
ries and samples as factors, both con-
siderd to behave in a random fashion.
This allows an estimate of the between
laboratory variance G^, within labora-
tory variance <5£, sample variance <52
and variance from laboratory-sample
interaction <5?~- In almost all instances
a natural logarithmic transformation of
the data was required to make the varia-
bility at different levels of the para-
meter approximately equal. The assump-
tion of homogeneity of variance was
tested by relating the within and in-
between laboratory standard deviation
to the concentration of the parameter
in the leachates. The within laboratory
standard deviation was calculated by
pooling the standard deviations compu-
ted from the replicates of each labo-
ratory, while the standard deviations
between laboratories was computed for
each leachate sample from the labora-
tory averages. Each standard deviation
o"was related to the mean through:
-------
leachate parameters were processed in
the above fashion. However for illustra-
tive purposes only the COD analysis will
be discussed.
ANALYSIS OF THE COD DATA
Data was received from 25 of the
46 laboratories who agreed to perform
the test on the 10 leachate samples. The
results in Table 2 indicate the range of
COD values reported with the maximum
value about 4.3 times larger than the
minimum value. Since a value of the
power term b included 1, a log trans-
formation was indicated ( Figure 1 and
2 ). The normal frequency distribution
and log normal frequency distribution
of the individual data points are shown
in Figure 3 and 4. A linear regression
through the quantile-quantile plots
showed that the average R increased
from 82% to 85% and that the average
standard deviation of R2 decreased
300.» a
0, 18000. 36000.
9000. 27000.
Average COD, i^g/Jt
6000.*
a 2. BO*
DC
S B
•" F
^ 2.10* H 6
£ -
5 s
° 1.40* I
° _
en
o _ •
J
.70*
1.60 3.20
2.40 4.00
Log.- of Average COD
4.60
Figure 1. Relationship of the within laboratory standard deviation
to the COD concentration level.
4.20*
2.80*
2000.
o 2.10*
- 2
0.* 2
o. leooo.
$000. 27000.
Average COD, mg/t
1.40*
+ -
1.60
2.4C
Log,_
3.20
*-0
Of Averaae COD
»C14
4. DO
Figure
2. Relationship of the between laboratory standard deviation
to the COD concentration level.
179
-------
40000.* O * 10500.* « 10000.* O
: R =92 ; R =63 : R =83
15000. • C
- ceccccc cc
. c CCCCCC
e c
HCOO.* 4
.
; R2=84 • ; R2=92 , ; R2=80
t o a«oo.+
OD nrooono o -
DDDD
00 0
>000.«
f ff
ft
ft
1000. • t
Z.O -2.0 0.0
1.0 -1.0
2000.. 2000.. """"I
:R=96 e 6 : R2=89 H i R2=62
200.*
: R2=81
Figure 3. Ordered laboratory averages for COD data (vertical axis) plotted
against quantiles from a normal distribution (horizontal axis)
for leachate samples A through J respectively.
180
-------
R2=87 '•": R2=92 "'"'- R2=70
c cc c c
ccrcccrcccc
c :c c
10.05* O ••«• 9 B'*°* O
: R =82 : R =86 - : R =90
0005 1C •
0003 090
D33
1.03* D
. f i f B.OO.
EFFF t
fftl
-let
IO* 6.80.
0,0 1.0 •*'D 0.0 2.0
-1 .0 1.0 -1 «O 1.0
'•": R2=99 . ' '•'"°:R2=77
Figure 4. Ordered laboratory averages for loge transformed COD data (ver-
tical axis) plotted against quantiles from a normal distribution
(horizontal axis) for leachate samples A through J respectively.
181
-------
from 12% to 9% after the log transfor-
mation, indicating that the transformed
data more closely resemble a normal dis-
tribution than the original data.
Most laboratories, i.e. 23 out of
the 25 used the dichromate reflux method
while one laboratory used the automated
dichromate reflux method. One laboratory
did not specify its method but probably
used the former method. A simple non
parametric test applicable to two-way
classified data without interaction, the
Friedman test, was used to determine
whether laboratories using different
methods had significantly different
scores. The Friedman test consists of
ranking the laboratories based on the
average reported value for each leachate
sample. The lowest value for analysis
of a given leachate sample is assigned
the rank of 1, the second lowest the
rank of 2 etc. These ranks are then
summed for each of the laboratories. The
ranking for the two COD metods showed
that the automated method had a score
of 49, while the reflux method had a
score of 132 indicating that the former
tends to give substantially lower results
than the reflux method.
The rank sum scored by each labo-
ratory was used to determine whether
excessive systematic error is attributed
to those laboratories scoring low and
high ranks. Assuming a chi square dis-
tribution,the 95% confidence interval
was calculated. Testing showed that 4
laboratories had consistently low scores
while 2 had high scores, indicating that
25% of the laboratories produce unaccep-
table results.
The analysis of variance on a
balanced data set with three replicates
showed an overall standard deviation,
equal to the coefficient of variation
in the original scale of 26.7%. The
analysis of variance performed on the
averages of all laboratories resulted
in a coefficient of 32.4%. The largest
component of the coefficient was made
up of a laboratory-sample interaction
indicating that some laboratories had
consistently high or low values depen-
ding on the leachate sample. Comparable
data generated in other studies ( EPA,
1974 ) show a coefficient of variation
of 6.6% for organic matter with a COD
of 270 mg/1 and 6.5% at 160 mg/1.
In none of the analysis was it
possible to detect a time effect,i.e.
a decrease of the COD due to bacterial
degradation within the 40 day period
that most analysis were conducted. Also
no significant dilution effect was
noted in which a higher COD is noted
at a greater dilution due to a reduc-
tion of interfering substances.
ANALYSIS OF OTHER CONSTITUENTS
The analytical results showed an
overall coefficient of variation rang-
ing from 32% for the COD test to 210%
for the cadmium determination as shown
in Table 3. The average coefficient of
variation for the physical parameters
such as pH and conductivity, is 93%,
for the organics such as COD and organic
nitrogen, is 81%. The variation for the
anions is 130% and for the cations 109%,
indicating that the parameters such as
sulfate and nitrate are the most diffi-
cult to determine precisely. The great-
est difficulty in the metal analysis
was noted for the cadmium and chromium
analysis.
Different methods used for indi-
vidual parameters tended to give vari-
able results. Both the automated colo-
rimetric COD method and the automated
alkalinity determination tended to give
lower results than the corresponding
manual titrimetric methods. The values
obtained with colorimetric Kjeldahl
method for organic nitrogen, the auto-
matic colorimetric method lor ammonia
nitrogen, the automated methylthymol
blue method for sulfate and the auto-
mated ferricyanide method for chloride
generally gave higher results than the
182
-------
corresponding manual methods.
Instrumental electrochemical methods
also tended to give values that were
different from the manual colorimetric
or titrimetric methods. Both the ammonia
and chloride determination with the spe-
cific ion electrode gave higher values
than the corresponding manual methods.
Differences were also noted
among instrumental methods. The barium
determination, for example, gave higher
results using the flame emission
method than the atomic absorption
alternative. The zinc determination
with the atomic absorption graphite
method tended to give higher results
than the direct aspiration atomic
TABLE
VARIANCE COMPONENT ESTIMATES WITH VISUALLY
OUTLYING LABORATORIES INCLUDED AND EXCLUDED*
Parameter
pH
ORP
Turbidity
Conductivity
Volatile Acids
COD
TOC
Total Residue
Volatile Residue
Organic Nitrogen
Ammonia Nitrogen
Sulfate
Total Phosphorus
Chloride
Alkalinity
Nitrate Nitrogen
Sodium
Potassium
Calcium
Magnesium
Barium
Iron
Zinc
Lead
Chromium
Cadmium
Copper
Nickel
G-r.
R
1 2
.35 .14
123 75
2.00 1.30
.46 .14
1.00 .66
.32 .24
.60 .28
.57 .21
.76 .29
1.50 .93
.89 .27
1.80 1.10
1.40 .63
.92 .17
.38 .19
2.00 1.40
.54 .12
.66 .16
.74 .23
.59 .10
1.40 .67
.53 .29
1.40 .41
.96 .79
1.70 .70
2.10 1.00
1.40 .60
1.10 .57
a T
L
1 2
.15 .10
93 39
1.50 .88
.22 .11
--
.63 .34
.20 .12
.29 .16
.52 .13
.64 .18
1.00 .76
.72 .16
.60 .66
1 . 20 .30
.49 .03
.22 .12
1.50 .90
.12 .06
.39 .12
.64 .12
.11 .08
1.00 .38
.28 .16
1.00 .18
.65 .51
1.30 .46
1.80 .76
1.10 .31
.73 .30
Sa\ c + cr2Tt
LS W
1 2
.31 .10
80 64
1.40 .95
.41 .10
.79 .57
.25 .20
.53 .24
.25 .16
.42 .22
1.10 .53
.52 .22
1.70 .90
.82 .55
.78 .16
.31 .14
1.30 1.10
.53 .10
.53 .11
.37 .20
.58 .06
.94 .55
.45 .24
.88 .37
.71 .60
1.10 .53
1.20 .64
.84 .51
.79 .48
% of labs
omitted
24
36
23
21
58
28
27
n
26
44
36
61
43
30
28
39
29
17
11
37
33
32
31
30
36
37
28
32
* Turbidity through Nickel for 1oge transformed data.
1 Visually outlying laboratories included.
2 Visually outlying laboratories excluded.
183
-------
absorption method. On the other hand, the
lead, chromium, nickel and cadmium as
determined in the graphite method tended
to give lower results than the direct
aspiration method.
All parameters were also tested
for time and dilution effects. Using a
one sided t-test at the 5% significance
level showed that no significant effect
existed.
Since the UI leachate sample was
send to the different laboratories both
spiked and unspiked, it was possible to
determine the recovery of the individual
elements. While the average recovery
was 81%, the value for the individual
parameters ranged from -138% for lead
to 328% for potassium ( Table 4 ). In
addition to lead negative recoveries
were also noted for phosphate, iron and
nitrate possibly indicating a precipi-
tation reaction and occurence of deni-
trification.
CONCLUSIONS AND RECOMMENDATIONS
The present study noted that the
between laboratory component of the
variation was larger than the within
laboratory variability. Substantial
TABLE 4. RESULTS OF RECOVERY STUDIES USING A SPIKED AND UNSPIKED
LEACHATE SAMPLE
Spiked
Sample
Parameter E
1
2
3
4
5
6
7
8
9
10
n
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
PH
ORP
Turbidity
Conductivity
Fatty Acids
COD
TOC
Total Residue
Volatile Residue
Organic Nitrogen
Ammonia Nitrogen
Sulfate
Total Phosphorus
Chloride
Alkalinity
Nitrate Nitrogen
Sodium
Potassium
Calcium
Magnesium
Barium
Iron
Zinc
Lead
Chromium
Cadmium
Copper
Nickel
Average
6.49
-138
349
5003
1514
3408
2220
4155
2168
168
103
112
6.42
275
1963
0.526
229
161
698
99.6
2.05
161
5.41
0.308
0.228
0.033
0.204
0.763
Unspiked
Sample
F
6.82
-196
560
3185
497
2047
66U
2944
1425
107
38.2
29.5
6.83
107
1701
0.608
103
83
675
60.7
1.87
172
4.67
0.317
0.080
0.010
0.199
0.144
Measured Calculated
Increase Increase
of Spiked of Spiked Percentage
Parameters Parameters Recovery
-0.33
-58
-211
1818
1017
1361
1560
1211
743
61
64.8
82.5
-0.41
168
262
-0.82
126
78
23
38.9
0.18
-11
0.74
-0.09
0.148
0.022
0.005
0.619
„
-
-
-
1062
4136
1141
4345
2660
35.5
26.4
156.5
1.3
97.7
145.5
0.65
66
23.8
263.3
35.5
2.7
131.3
6.3
0.065
0.580
0.007
0.035
0.640
_
-
-
—
ga7%
32.9%
137%
27.9%
27.9%
172%
245%
52.7%
-31.5%
172%
180%
-126%
191%
328%
8.7%
109%
6.7%
-8.4%
11.7%
-138%
25.5%
314%
14.3%
96.7%
81%
184
-------
differences were noted between different LIST OF REFERENCES
methods. Since more and more analysis
in the future will be conducted using Chian E.S.K and DeWalle F.B."Compilation
automated methods as opposed to manual of Methodology for Measuring Pollution
methods, a detailed comparison between Parameters of Landfill Leachate" US
the two type of methods is required for Environmental Protection Agency Report
several parameters. Such a comparison EPA 600/3-75-011, Cincinnati Ohio
is also required between electrochemical (1975).
methods using specific ion electrodes
and the corresponding manual methods. An EPA"Methods for Chemical Analysis of
indepth comparison between the graphite Water and Waste Water" US Environmental
AA and the direct aspiration AA is also Protection Agency, Technology Transfer,
necessary. Washington DC (1974)
185
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DEVELOPMENT OF THE PROPOSED
DEFINITION OF HAZARDOUS WASTE
David Friedman
U.S. Environmental Protection Agency
401 M Street S.W.
Washington, D.C. 20460
ABSTRACT
The Resource Conservation and Recovery Act of 1976 created a regulatory framework to
Control the disposal of waste materials. The Act divides wastes into two classes for con-
trol purposes. This paper summarizes how the broad legislative definition of a hazardous
waste was translated into the one proposed on December 8, 1978 (Federal Register) for use
in evaluating specific waste materials. The rationale for incorporating ignitability, cor-
rosivity, reactivity, toxicity, radioactivity, and infectiousness as characteristics of a
hazardous waste are discussed.
INTRODUCTION
The Resource Conservation and Recovery
Act of 1976 (RCRA) created a regulatory
framework to control the disposal of those
wastes not adequately controlled by exist-
ing environmental legislation. The Act
sets up two classes of waste. For hazard-
ous waste, it creates a management control
system which requires "cradle-to-grave" cog-
nizance including monitoring, record keep-
ing, and reporting throughout the system.
To paraphrase the Act, hazardous wastes are
those which may pose a substantial present
or potential hazard to human health or the
environment when improperly managed. All
other wastes are considered to be non-haz-
ardous and are subject only to requirements
of the States. The Act calls for the pro-
hibition of open dumping and requires envi-
ronmentally acceptable practices. However,
while EPA was given authority to write
rules for what constitutes environmentally
acceptable disposal, only in the case of
hazardous wastes was authority given to en-
force the rules. The Act also gives the
States the option of administering the haz-
ardous waste program as long as their pro-
gram is at least as stringent as the Federal
program. Thus, the Federal regulations will
be the least stringent to which generators,
storers, transporters, treaters, and dis-
posers of hazardous waste must respond.
This morning I will discuss some of the
highlights of how this broad definition was
refined into one which can be used to de-
termine whether or not a particular waste
is hazardous. Six criteria were used in
determining specific characteristics to use
in defining a hazardous waste. These cri-
teria were:
1. The particular characteristic was
spelled out in RCRA.
2. We had information on incidents
which showed a particular char-
acteristic has caused damage.
3. Other government or private organ-
izations which regulated or recom-
mend management methods for haz-
ardous substances have identified
a characteristic to be of concern.
4. The characteristic could provide
a general description of the haz-
ard rather than appearing merely
as a list of sources.
5. The likelihood of a hazard devel-
oping if the waste was mismanaged
is sufficiently great, and,
186
-------
6. A reliable identification or test
method for the presence of the
characteristic is available.
Use of this last criterion has led EPA
to try and describe each characteristic by
specific testing protocols. Where this was
not possible, the characteristic was either
set out as a prose description readily rec-
ognizable by persons working in the field,
or reserved for future regulatory action.
It must be emphasized that neither the
set of characteristics nor the specific def-
initions of the characteristics are static.
Both may be added to or changed as new in-
formation develops.
Based on those previous criteria, the
following hazard characteristics were
considered:
1. Ignitability
2. Corrosivity
3. Reactivity
4. Toxicity
5. Radioactivity
6. Infectiousness
In order to provide specific descrip-
tions of wastes meeting these characteris-
tics, each characteristic was defined in
terms of specific definable properties. The
following is a brief description of each
characteristic and its properties. It
should be noted here that radioactivity and
infectiousness are not included as charact-
eristics at this time.
Ignitability
The objective of the ignitability
characteristic is to identify wastes which
present a fire hazard under routine dis-
posal or storage conditions. The result-
ing fires present not only the immediate
danger of heat and smoke, but also provide
a pathway by which toxic particulates can
spread to the surrounding area.
There are several methods which can be
used to identify ignitable materials depend-
ing on the physical state. For liquid
wastes, flash point was selected as the
property to use. The specific value chosen,
60°C (140°F) was selected after considering
the ambient temperatures to which waste may
be exposed during management.
For solid materials, a descriptive
definition was selected because of lack of
suitable test methods. For waste gases,
EPA proposed to use the DOT identification
since the major hazard arising from flam-
mable gases would be during transport.
Corrosivity
A corrosivity characteristic has been
included for two reasons. First, to iden-
tify those wastes which need to be segre-
gated or specially handled because of their
ability to mobilize heavy metals which
might otherwise not migrate. Secondly, to
identify those wastes requiring special
containers during transportation and storage.
While heavy metal solubilization is an
extremely complex phenomenon, pH has been
found to be its most important indicator.
The pH limits chosen in these proposed regu-
lations were based upon skin corrosion lim-
its and heavy metal solubilization data.
The metal corrosion limits were taken from
DOT Hazardous Materials regulations, because
EPA1s concern about container damage is iden-
tical to that of DOT's in this case.
Reactivity
The objective of the reactive waste
characteristic is to identify waste which
under routine management presents a hazard
because of instability or extreme reactivity.
Reactivity includes the tendency to auto-
polymerize; to create a vigorous reaction
with air or water; to exhibit shock and
thermal instability; to generate toxic gases,
and to explode.
The largest stumbling block to develop-
ing general test methods for use in identi-
fying reactive waste is that while there
are many inputs of energy that may cause a
waste to react or exhibit hazardous proper-
ties, there is no one stress that can cause
all reactive waste to do so. To compound
the problem, reactivity is not just a func-
tion of the composition, temperature, and
availability of initiating agents, but is
also affected by the mass and geometry of
the waste. Thus, the reactivity of a tested
waste sample may not necessarily correspond
to the reactivity of the waste as a whole.
Since reactive waste is dangerous to
the generator's own operations (as well as
being hazardous for long term disposal),
generators of reactive waste tend to be aware
that their waste has that characteristic.
187
-------
For this reason, EPA feels that the pro-
posed descriptive definition will be an
adequate identification method when used
in conjunction with the test methods iden-
tifying thermal and shock instability.
Toxicity
The toxicity characteristic is intended
to identify waste which, if improperly dis-
posed of, may release toxicants in suffi-
cient amounts to pose a substantial hazard
to human health or the environment. The
RCRA definition of hazardous waste requires
EPA to make a judgement as to the hazard
posed by a waste "when improperly treated,
stored, transported, or disposed of, or
otherwise managed." For waste containing
toxic constituents, this hazard is depend-
ent on two factors:
- the intrinsic hazard of the con-
stituents of the waste, and
- the release of the constituents
to the environment under condi-
tions of improper management.
To assess the intrinsic hazard posed
by the constituents a series of toxicity
indicators has been considered. Those
which we feel are of sufficient concern to
be eventually incorporated in a hazardous
waste definition are:
- acute and chronic toxicity to
humans, animals, and plants,
- potential for bioaccumulation
in tissue,
- oncogenicity,
- mutagenicity, and
- teratogenicity.
However, the toxicity definition pro-
posed in December 18, 1978, is limited to
the onset of toxicants for which National
Interim Primary Drinking Water Standards
(NIPDWS) have been developed. To determine
whether toxic constituents in the waste
might migrate in the disposal environment,
a procedure has been developed to measure
the tendency of the constituents of a waste
to leak or leach out and become available
to the environment under poor management
conditions. This procedure has been termed
the Extraction Procedure and will be dis-
cussed later.
Radioactivity and Infectivity
Two other properties of wastes that
were deemed to be of concern are radioactiv-
ity and infectiousness. After studying this
area, it was decided that sources and types
of wastes posing these hazards are relative-
ly few. It was thus decided that, at this
time, instead of specifying specific tests
for these characteristics, identification
would be via a listing of sources.
As the toxicity characteristic is one
of the more complicated and far reaching
aspects of the definition, its development
will be discussed in more detail.
Numerous studies and reports indicate
that damage to ground and surface water
frequently results from migration of toxic
chemicals from the initial disposal site.
Groundwater contamination is a particularly
important concern because it is a source of
drinking water for almost half of the popu-
lation. In addition, once contaminated, its
usefulness as a source of drinking water may
be impaired for years. It was thus decided
that use of a groundwater contamination
scenario to "model" improper disposal would
be advisable. By selecting a groundwater
contamination scenario, we did not mean to
imply that other vectors are not important.
However, we do feel, that except in rare
cases, control levels set using this model
will be sufficient to protect against
other routes of contamination.
The model is based on wastes creating
a problem through migration of chemicals
out of the disposal site and into a drink-
ing water aquifer. I want to emphasize
that the contamination model has been de-
veloped for definitional purposes only.
It does not address actual disposal methods
which might need handling in a manner dif-
ferent from ordinary refuse.
Once the specific properties of toxic-
ity were selected, other objectives became
important. These include:
1. Formulation of a dynamic definition
which would not only identify those
wastes which contain known toxicants,
but also those wastes which contain
materials or combinations of materials
whose toxic properties have not yet
been recognized, and
2. specification of toxicant control
levels consistent with environmental
goals formulated under other regu-
latory authorities.
188
-------
In order to take into account the
difficulty of formulating a test scheme
applicable to wastes of widely varying
complexity, it was decided that having
definitions based on both analytical and
biological parameters would be desirable.
Either one could be used to evaluate
whether a given waste is hazardous. The
analytical set would rely on a quantitative
analysis of an extract of the waste, com-
bined with hazard thresholds based on mam-
malian, aquatic, and terrestrial plant
toxicities. If the concentration of any
species exceeded the calculated threshold
value, then the waste is deemed to be a
hazardous waste. A bioassay approach would
also be available to use when complicated
or hard to analyze wastes are to be eval-
uated. In this approach, sensitive aquatic
and plant species are exposed to an extract
of the waste and examined for signs of tox-
icity. If manifestations of toxicity are
noted, then the waste is a hazardous waste.
We feel that this type of definition is
desirable for several reasons:
1. By keying to waste properties,
rather than a static list of
known hazardous materials or
wastes, the definition would be
dynamic. As new toxic agents
enter the waste disposal network
they would then be immediately
covered.
2. Using biological indicators
offers a mechanism for assess-
ing toxicant synergism and an-
tagonism in complex mixtures
characteristic of wastes.
3. Testing costs are low enough so
that non-hazardous wastes will
not be forced into the hazardous
waste net as a result of prohibi-
tively expensive test procedures.
The test scheme devised to meet the
total definition of toxic waste is outlined
in Figure 1. However, at this time, it
must be pointed out that the characteristic
defining toxicity has been severely limited
in the regulations proposed on December 8,
1978. The proposed definition is limited
to those wastes containing significant
amounts of leachable substances for which
a National Interim. Primary Drinking Water
Standard has been set.
The complete definition would employ
biological tests for mutagenic activity
and environmental persistence coupled with
an instrumental method for bioaccumulation
potential. It includes a choice between
using either bioassay or analytical tests
for measuring chronic toxicity, aquatic
toxicity, and terrestrial plant toxicity.
For those toxicants known to be either mu-
tagenic, carcinogenic, or teratogenic, but
which are not biologically active in the
in vitro mutagenicity assays prescribed,
control will be via listing on the "Con-
trolled Substances List." In order to keep
testing costs to a minimum, consistent with
the need for adequate information, short-
term in vitro bioassays have been selected
whenever possible.
However, while we believe that the
toxicity definition that I have just out-
lined would substantially meet the goals
previously described, we feel that use of
this definition is premature at this time.
Three factors accounted for this decision.
1. We have not had sufficient time
to adequately validate and de-
bug the bioassay procedures.
2. Concern over using the NIOSH
Registry data in a manner for
which it was not intended.
3. The lack of adequate data with
which to determine the size of
the hazardous waste class which
would be so created.
Thus, in order to carry out the man-
date of RCRA and implement a hazardous
waste control program without further de-
lay, a modified approach was proposed on
December 18th. As I mentioned earlier,
this approach makes use of the Extraction
Procedure to measure toxicant availability
combined with use of EPA National Interim
Primary Drinking Water Regulations -as a
basis for determining threshold levels.
However, since many wastes contain mobile
toxic chemicals for which there are no
drinking water standards, an expanded use
has been made of lists as identifiers of
hazardous waste. These hazardous waste
lists contain those industrial processes
and wastes for which the Agency has suffi-
cient information to indicate that, in
general, disposal of the waste requires
controlled management. In order to give
the generator of a listed waste a means
of demonstrating that his particular waste
189
-------
FIGURE 1
Protocol for classification
of hazardous wastes
Waste
Liquid-Solid
Separation
KEY
Solid
Exceeds
Threshold"
Less than
Threshold
(Passes
Test)
Exceeds
"Threshold
(Fails
Test)
Extraction
Procedure
40 CFR 250.12(d)(2i)
Liquid
Mutagen
Test
40 CFR 250.15(a)(bi)
Analytical
Biaaccumulation
test
40 CFR 250.15 (a)lbii)
- —
Degradation
Test
J
Bioassay
•«-.
-*•
•*•
Analysis for
DWS Species
40 CFR 250.12 (did)
1
Organic Analysis
40 CFR 250.15 (a)lbiii)
1
Analysis for Water
Quality Criteria
& Phytotoxic Species
L
r
Non-Hazardous
Cytotoxicity
1
Daphnia Magna
(Aquatic Toxicity)
*
Soybean, Wheat, Radish
(Phytotoxicity)
}
Hazardous
190
-------
is ±n fact not hazardous, test procedures
have been developed.
While use of these analytical, muta-
genic, and bioaccumulative tests have not
been included in the hazardous waste defin-
ition because of a lack of data on their
impact, this is not a problem when they are
used for delisting purposes. In order for
a generator to demonstrate that his waste
is not hazardous, the Agency will accept
data using these tests.
191
-------
VEGETATION GROWTH IN LANDFILL ENVIRONS
Edward F. Gilman, Franklin B. Flower,
Ida A. Leone, and John J. Arthur
Cook College, Rutgers University
New Brunswick, New Jersey 08903
ABSTRACT
During the past dozen years, many attempts to revegetate completed sanitary landfills
have been undertaken throughout the United States, with variable degrees of success. This
has been evaluated in a recent nationwide field survey of vegetation growth on completed
sanitary landfills. Based on the results of this survey, literature reviews and other
field experiences, a study was undertaken to determine which species, if any, can maintain
themselves in a landfill environment; to investigate the feasibility of preventing land-
fill gas from penetrating the root zone of selected species by using gas barrier tech-
niques; and to identify the (those) factor (s) which are most important in maintaining
adequate plant growth on completed sanitary landfills. Ten replicates of nineteen woody
species were planted on a ten-year old completed sanitary landfill and five gas barrier
systems were constructed. The experiment was replicated on nearby old forest land to act
as a control. Of the nineteen species planted on the landfill for the past two years,
certain species have tolerated the landfill conditions better than 'others. Where the gas
barrier technique kept landfill gases from the root zone the trees grew best.
Carbon dioxide and methane are the major components of sanitary refuse landfill-
generated gas which have been associated with the demise of vegetation on and adjacent to
completed landfills. An investigation of the effects of carbon dioxide (002) and/or
methane (CH^) contaminated soil atmospheres on the growth of tomato (Lycopersicon
esculentum) plants indicated that C02 per se was toxic to tomato roots in a low Op soil
atmosphere, whereas CH1| per se was innocuous under the same conditions. Investigations
into the effects of COg and CHlf contaminated soil indicated that red maple (Acer rubrum)
is more tolerant to the presence of these gases than is sugar maple (Acer saccharum).
INTRODUCTION
The pressures of population expansion
and urbanization have prompted a reapprais-
al of anticipated uses for completed land-
fill sites. Conversion to recreational
areas or other non-structural usage has
been considered an acceptable end for com-
pleted landfill sites in urban areas; and
in rural areas intensifying land use has
resulted in attempts to use completed land-
fills for growing commercial crops. Numer-
ous farmers, as well as scores of land-
scapers, have encountered mixed success in
trying to establish agricultural crops,
trees, and shrubs on landfills throughout
the country. Three questions are often
raised: "What species will thrive on com-
pleted landfill sites?", "Are there any
techniques available which will help in
attempting to establish a vegetative cover
over a completed lindfill area?", and "What
is the nature of the toxic effect of land-
fill gas on vegetation?"
Reports from a Rutgers University (New
Brunswick, New Jersey) nationwide mail
survey funded by the Federal E.P.A. Solid
and Hazardous Waste Division determined
that the scope of problems encountered when
vegetating completed landfills was indeed
of national latitude (15). It was ascer-
192
-------
tained, from on-site visits to some 60 veg-
etated landfills, that answers to the pre-
viously raised questions would benefit not
only the landscaper or farmer trying to
vegetate a former landfill, but the general
public as well in that they too would ulti-
mately derive value from successful vegeta-
tion projects such as parks, golf courses
and recreational areas.
In order to investigate the possibil-
ity of successfully growing vegetation on
such areas, two experiments were designed:
(l) a field experiment with three objec-
tives: (a) to determine the relative tol-
erance of a number of commonly grown tree
and shrub species to the soil environment
created on and adjacent to a sanitary
refuse landfill; (b) to determine if bar-
riers to the migration of decompositional
gases can function in preventing gas con-
tamination of the root systems of selected
species; (c) to identify those soil factors
which are most responsible for causing
vegetation growth problems on completed
landfills. (2) A greenhouse experiment to
assess the effects on vegetation of soil
contamination by simulated landfill gas
(C02 and CHI).) mixtures.
This study was funded by EPA Grant No.
R 803762-02 from the Solid and Hazardous
Waste Division of the Environmental Pro-
tection Agency, Cincinnati, Ohio.
LITERATURE REVIEW
Serious disadvantages for adequate
vegetation growth inherent in landfill
sites; namely the production of toxic gas
mixtures from anaerobic decomposition of
organic matter present, as well as high
ground temperatures, have been reported
(38).
The composition of landfilled refuse
varies considerably depending on its ori-
gin, be it municipal, industrial, inciner-
ation ash or sewage sludge. The organic
content of solid waste collected from
homes, schools, commercial establishments
and industries generally ranges from 50 to
75$ on a weight basis. Most of these or-
ganics are biodegradable and can be broken
down into simpler compounds by both aerobic
and anaerobic organisms. The rate at which
this occurs is reported to be a function of
a variety of factors (8, 28).
When the refuse is initially deposited
in the landfill, there is enough oxygen
present to support a population of aerobic
bacteria. This state lasts from one day to>
many months (12). The literature indicates
carbon dioxide and water to be the princi-
pal products formed in aerobic decomposi-
tion (6). After the oxygen concentration
is depleted, the aerobic bacteria die, and
there is a sharp increase in the anaerobic
bacterial population. During anaerobic
decomposition C02 and CHI), are the principle
gases produced (ll, 35). Various other
gases reportedly produced in the anaerobic
environment of the landfill include ethane,
propane, hydrogen sulfide, nitrogen and
nitrous oxide (l, 7, 26, 35). Reserve
Synthetic Fuel Company reports finding over
60 different gases in a California landfill
(18).
In addition to the methane-producing
bacteria mentioned above, there exists a
bacterium, Pseudomonas chromobacterium,
which utilizes methane during its metabo-
lism. It oxidizes methane, producing car-
bon dioxide and water (22). Since oxygen
is required for this reaction, these bac-
teria will generally be found near the
upper surface of the landfill and in lands
adjacent to the landfill.
In spite of predictable negative suc-
cess in utilizing landfill for the support
of vegetation, many reports of success or
proposals for transforming barren former
refuse sites into, luxuriant vegetated areas
have appeared in the literature and in the
press (2, h, 22, 23, 29). In July 1972, an
article by Duane (9) applauding the con-
struction of golf courses on completed san-
itary landfills cited the successful use of
such tree species as Japanese black pine,
London plane, thornless honey locust and
Russian olive for beautifying the sites.
In 1973, an anonymous article appeared in
Solid Waste Management magazine describing
the transformation "From Refuse Heap to
Botanic Garden","of an 87-acre landfill in
Los Angeles that"had the distinction of
being the world's first such phenomena (3).
Few problems if any were either observed or
anticipated in achieving these spectacular
results with the exception of the report of
root damage to large trees and shrubs at
the Los Angeles Botanic Garden site.
At the same time, various investiga-
tors were experiencing difficulties in
growing vegetation at similar sites. In
January 1969, Professor F. Flower and
193
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associates of Rutgers University in New
Brunswick, New Jersey (IT), responding to a
complaint of vegetation death on private
properties adjacent to a landfill in Cherry
Hill Township observed dead trees and
shrubs of the following species: spruce,
rhododendron, Japanese yew, azalea, dog-
wood, and others. Testing of the soil with
appropriate equipment disclosed high con-
centrations of carbon dioxide and explosive
gases. The conclusion reached was that the
trees and shrubs might have been killed by
displacement of oxygen from their root
zones by lateral movement of the gases of
refuse decomposition or by the decomposi-
tion gases themselves. Additional vegeta-
tion deaths caused by the migration of
landfill gases were first noted at the
Hunter Farm in Cinnaminson, New Jersey in
1970 and at a peach orchard in Glassboro,
New Jersey in 1971
On a December 197*1- visit to the Hunter
Farm, when fields planted with rye were
growing poorly (l6) , gas checks revealed
that combustible gases were present in the
area of new vegetation injury and that mi-
grating gases were reaching up to 600 feet
from the nearest edge of the landfill. An-
other trip to Hunter ' s Farm was made in
June 1975 when corn was found to be growing
poorly in areas where combustible gas and
C02 concentrations were high (1*0.
In 19*1-5, Chang and Loomis conducted a gen-
eral survey of the literature and concluded
that plants would survive concentrations of
1 to 2$ oxygen in the root zone. They also
concluded that most plants should function
normally at soil oxygen concentrations
ranging from 5 to 10$ (7). Dense soil also
increases the need for oxygen at the grow-
ing root tip. This is believed to be due
to the extra work that has to be done by
the root tips as they push their way
through the soil (21). Higher temperatures
were found to increase the oxygen require-
ment for growing roots (32).
Low concentrations of oxygen have been
reported in the soil near natural gas leaks
(19). A similar situation has been found
both on and adjacent to sanitary landfills.
Oxygen volume concentrations in the soil on
landfills were found to range from 1$ to
of the soil atmosphere (1*0.
There has been a considerable amount
of research in establishing tolerance among
different species to excess carbon dioxide
in the root zone. Cotton seedlings grown
in hydroponic solutions were able to make
optimum growth with 10$ carbon dioxide pre-
sent, provided at least 7.5$ oxygen was
also present. Thirty to 1+5$ carbon dioxide,
however, was found to severely reduce root
growth (25). Red and black raspberries
were killed when their roots were exposed
to 10$ carbon dioxide. Root growth in
broad bean and kidney bean was completely
inhibited by 5.5$ carbon dioxide (32).
Volume concentrations of soil carbon
dioxide in the cover of landfills visited
ranged from less than 1$ to *|2$ of the soil
atmosphere. A large percentage of these
readings were in the 5$ to 15$ range (15).
Normal soil C02 concentrations range from
0.0*4 to 2$ (25); therefore, the levels re-
corded in the survey may be considered
excessive.
There is convincing indirect evidence
that shoot growth in trees is related to
water deficiency, another stress character-
istic of landfill cover soil. Forest men-
surationists find tree height the most
sensitive growth parameter for measuring
site productivity, to which the generally
accepted key is soil moisture (33, 3**^ 37).
Correlations between rainfall and shoot
growth have been attempted with various
degrees of success for many decades (27, 30),
and there is little doubt that wet years
produce longer shoots than dry years for
many tree species on upland sites. Root
tissues are probably never at as severe
water stress as shoot tissue because roots
are closer to the water supply than leaves.
Flood tolerance may be related to C02-
02 ratios in the soil. Hook et al (23)
investigated flood tolerance in swamp
tupelo and concluded that under flooding
conditions, this species develops new roots
that accelerate anaerobic respiration rate
in the absence of oxygen, oxidize their
rhizosphere, and tolerate high levels of
carbon dioxide. The absence of any of these
root adaptations would appear to reduce
flood tolerance of a species. White (37)
observed survival of certain species under
water for 10 days to 3 weeks after hurri-
cane Agnes in 1972. Those which did not
tolerate flooding conditions included
Norway maple, sugar maple, white birch,
gray birch and many others.
194
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PROCEDURES AND METHODS
Field Studies
An ideal site for a landfill study was
defined as one which has a relatively high
combustible gas concentration and adequate
drainage. The control site should be lo-
cated on virgin land, close to, but not
adjacent to the landfill and have no com-
bustible gas in its soil atmosphere. The
sites should be large enough to accomodate
a V spacing between adjacent trees.
The Edgeboro Landfill, on which the
experiment is being conducted, is located
on a marsh adjacent to the Raritan River.
The deposited refuse is reported by the
landfill owner to be approximately 30' deep
under the experimental plot. Some methane
may also be generated in the marsh beneath
the refuse. The general municipal refuse
landfill was completed at this location
early in 1966. Later that year,, 6"-10" of
soil were placed over the refuse as a final
cover.
The experimental plot is 72' x 108',
an area large enough to accommodate the
screening of 10 replicates of 19 different
tree and shrub species and 5 landfill gas
interception systems. The control plot is
located approximately a quarter of a mile
from the experimental plot and is on a
former undisturbed woodland. It is W)' x
110* and accommodates 10 replicates of the
same 19 species planted on the experimental
plot in addition to 2 gas-barrier systems.
Enough soil was spread on the experimental
landfill plot to bring the total depth of
cover soil to 2'. Two feet of the same
soil was spread on the control plot as
well.
Following the designation of the ex-
perimental plot, the precise boundaries for
5 gas interception systems (three 10' x IV
trenches and two iV x 18' mounds) were
determined by selecting the areas of high-
est combustible gas concentration in the
soil atmosphere. A catepillar tractor
bulldozer was used to dig the three 3'
deep trenches and to move the excavated
rubbish from the experimental site.
In order to prevent landfill decom-
position gases from penetrating the soil,
the 3 trenches were lined at the bottom
with various barrier materials prior to
backfilling with topsoil (Figure 1A). One
trench was underlain with a one-foot deep
layer of 1" round road-gravel beneath a
sheet of k-mil polyethylene plastic. Ten
five-foot long, four-inch diameter perfo-
rated P.V.C. pipes were placed through the
plastic and into the gravel equispaced
around the trench. A second trench was
lined on the bottom with a 1-ft. thick
layer of clay and also contained 10 verti-
cal vent pipes located around the periphery
of the trench. The third trench was under-
lain with a 1-ft. thick layer of clay and
contained no vents. Topsoil (79/0 sand, 12$.
silt, 9/0 clay) was then backfilled into
each of the trenches.
Two 3-ft. high soil mounds were con-
structed using the same soil as in the
trenches. One was underlain with a 1-ft.
thick layer of the same clay used in the
trenches while the other mound contained no
gas barrier (Figure IB).
In order to screen species represen-
tative of a maximum number of desirable
landscaping characteristics and a variety
of genotypes, plants were chosen from a
number of categories (Table 1). Nineteen
species were selected on the basis of these
eight criteria and planted in replicates of
10 on the experimental landfill and control
screening areas totaling 380 plants. Six
American basswood and h Japanese yew were
chosen for planting on each of the trenches
and mounds because of the reported suscep-
tibility of these species to landfill gases.
In order to characterize the landfill
cover-soil environment, gas samples were
collected from forty-eight buried samplers
approximately every two weeks, beginning in
March and ending in August 1977. Forty-two
of the sampling stations were on the exper-
imental plot and six on the control plot.
Gas samples were collected from the sam-
plers by means of gas-tight syringes and
analyzed for 02, C02, N2> and CHlj. in a
Carle Instrument Model 8^00 Gas Chromato-
graph. Soil temperatures at the 1' depth
were recorded from the same sample point
and on the same dates as the gas samples.
Beginning in mid-March, 1977, soil
moisture measurements were made at two
week intervals on six samples from the
experimental and four from the control
screening area, and one from each of the
gas interception systems. Soils were mea-
sured for bulk density in each planting
195
-------
h Japanese Yews
10 American Basswoods
0
3'
Topsoil
1' Gravel
-10'
T 1' Topsoil
J
jT-
Subsoil
Plastic Sheet
10 PVC Perforated
Vent Pipes
Figure 1A. Cross section end view of gravel/plastic/vents trench
Japanese Yews
10 American Basswoods
—
,
I1 Clay
,
1' Subsoil
Figure IB. Cross section end view of soil mound
196
-------
TABLE 1. TREE PLANTING SELECTION CRITERIA
Trees Tolerance to
Low C>2 Tension
Environments
w
w
pH
vy
R
B
H
O
W
O
03
Honey Locust (Gleditsia triacanthus)
American Sycamore (Platanus occidentalis)
Red Maple (Acer rubrum)
Green Ash (Fraxinus pennsylvancia)
Black Gum (Nyssa sylvatica)
Weeping Willow (Salix babylonica)
Pin Oak (Quercus palustris)
Ginkgo (Ginkgo biloba)
Sweet Gum (Liquidambar styraciflua)
American Basswood (Tilia americana)
Hybrid Poplar (Populus sp. )
Mixed Hybrid Poplar (Populus sp. )
Euonymus (Euonymus alatus)
Bayberry (Myrica pennsylvanica)
X
X
X
X
X
X
X
Aesthetic
Landscaping
Purposes
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Other *
Criteria
3
1
3
1
k
Rhododendron (Rhododendron elegans)
CQ
03
White Pine (Pinus strobus)
Japanese Black Pine (Plnus thunbergi)
Norway Spruce (Picea excelsal
Japanese Yew (Taxus cuspidata capitata)
X
X
X
X
2
U
* Other Criteria
1 Ubiquity
2 Seal salt tolerance
3 Tolerance to city conditions
h Susceptibility to landfill conditions
technique and in both the experimental and
control screening area.
In order to characterize the growth of
each tree on the experimental and control
plots during 1976, four measurements of
shoot length were obtained for each tree.
During the 1977 growing season, one measure-
ment each of root biomass and cross sec-
tional stem basal area, four measurements
of leaf weight and six measurements of
shoot length were obtained for each tree.
Simulated Landfill Studies
In order to select realistic concen-
trations of landfill gas components for
inclusion in simulated mixtures for green-
house studies, soil gas concentrations of
19 sanitary landfills visited throughout
the continental United States were measured
between August 1975 and January 1977 (l6).
To investigate the ability of tree
seedlings to survive in soil atmospheres
197
-------
contaminated with excessive amounts of
carbon dioxide (C02) and methane (CHlj.), two
species of maple were chosen: red maple
(Acer rubrum) because of its ability and
sugar maple (Acer saccharum) because of its
inability to withstand flooding. These
species were compared in order to determine
if the species more tolerant to flooding
was also more tolerant to soil atmospheric
contamination with C02 and CKi±.
One-year old red and sugar maple seed-
lings were planted (5 each) in twelve
20-gallon modified galvanized steel trash
cans (Figure 2).
The seedlings were divided into three
treatments with 20 seedlings (10 of each
species) in each treatment. For treatment
1 the soil in each can was fumigated with
a gas mixture containing approximately 3$
02, 1*0$ C02, 50$ CHlj. and 7$ N2. Treatment
2 was a control with compressed ambient air
forced through the soil. In treatment 3
the seedlings were flooded by filling the
cans with water to a depth of 2 inches. In
order to fumigate the soil, two cans were
attached in parallel to a cylinder contain-
ing the gas mixture.
The composition of the soil atmo-
spheres was monitored by extracting a 0.5
ml. sample of air from samplers buried at
a 7 inch depth in the soil and analyzing
it with a Carle model 8500 gas chromato-
graph.
The physiological condition of the
seedlings was monitored "by periodically
measuring the rate of transpiration with a
Lambda Instruments Diffusive Resistance
Porometer. This instrument measures water
vapor that evaporates from the leaf surface.
If the root system was damaged, the tree
would be unable to take up water fast
enough to support normal transpiration.
In order to investigate the effect of
simulated landfill gas on tomato plants,
Rutgers tomato (Lycopersicon esculentum)
plants were grown in specialized It-liter
culture vessels in sand solution culture
(Figure 3).
When the plants were about 1 foot
high, the lower leaves were pruned and lids
were placed on the glass vessels (Figure 3X
Cotton impregnated with heavy duty silicon
vacuum grease and vaseline was used to
provide a seal around the stems of the
plants.
Tomato experiment 1 was designed to
examine the response of tomato plants to a
soil atmosphere having suppressed 02 con-
centrations in conjunction with elevated
concentrations of C02 and CH^ (Table 2).
This experiment consisted of 21 plants
which were divided into 3 treatments with
7 replicates for each.
TABLE 2. COMPOSITION OF ATMOSPHERES USED
TO FUMIGATE TOMATO PLANTS IN
EXPERIMENT 1
TREATMENT
$02
$C02
$N2
$0%
21
trace
79
0
7
trace
93
0
7
10
58
25
* Atmospheric air
Experiment 2 was designed to determine
the effects of a soil atmosphere containing
high concentrations of both methane and
carbon dioxide on the growth of tomato
plants compared with soil atmospheres con-
taining only carbon dioxide or methane
(Table 3). This experiment consisted of 20
plants which were divided into 5 treatments
with It- replicates for each.
TABLE 3. COMPOSITION OF ATMOSPHERES USED
TO FUMIGATE TOMATO PLANTS IN
EXPERIMENT 2
TREATMENT
$o2
$C02
$N2
$Cffl+
A*
21
trace
79
0
B
5
trace
95
0
c
5
ho
55
0
D
5
1*0
5
50
E
5
trace
^5
50
* Atmospheric air
Experiment 3, was designed to deter-
mine the effects of a soil atmosphere con-
taining high concentrations of carbon
dioxide on the growth of tomato plants
exposed to differing oxygen concentrations
in the soil (Table 1*). This experiment
198
-------
-16"
Maple Seedlings
Gas Sampler
Soil Mixture
Glass Wool
Gravel
Gas Injection Port
2 Drainage Hole Plugs
2 Bricks
Figure 2. Modified galvanized steel trash can used to fumigate maple seedlings
199
-------
Notch in Second Lid
Notch in First Lid
Tomato Plant
01
9
Gas Mixture Inlet
Tomato Plant
2 Glass Lids
Gas Mixture Outlet
Gas Sampler
Thermometer
Sterilized Sand
Glass Wool
Gravel
Water Drainage Outlet
Figure 3. Culture vessel used to fumigate tomato plants
200
-------
consisted of 12 plants which were divided
into 3 treatments with k replicates for
each.
TABLE k. COMPOSITION OF ATMOSPHERE USED
TO FUMIGATE TOMATO PLANTS IN
EXPERIMENT 3
A
%02 k
foC02 trace
foN2 96
TREATMENT
B
15
30
55
C
k
30
66
Experiment k, was designed to deter-
mine the effects of a soil atmosphere con-
taining high concentrations of methane or
carbon dioxide on the growth of tomato
plants (Table 5). This experiment consist-
ed of 16 plants which were divided into k
treatments with k replicates for each.
TABLE 5- COMPOSITION OF ATMOSPHERE USED
TO FUMIGATE TOMATO PLANTS IN
EXPERIMENT k
TREATMENT
A BCD
%o2
foCOp
$N
2
%CEh
5
trace
95
0
15
10
75
0
15
20
65
0
5
trace
50
45
The height of the tomato plants was
determined by measuring the distance from
the glass lid to the tip of the uppermost
fully expanded leaf. Adventitious root
development was reported only when it
occurred above the lid.
The soil atmosphere in the culture
vessels was monitored with a Carle model
8500 gas chromatograph as described previ-
ously. Total nitrogen content of the dry
plant tissue was determined by using the
Kjeldahl method, which gives a reading in
mg. per 100 mg. of dry plant tissue (31).
RESULTS
Field Studies
Sixty-two trees died by the end of the
1977 growing season, 38 on the experimental
plot and 2k on the control. The mean car-
bon dioxide, methane and temperature were
significantly greater (99$ C.I.) and the
oxygen and moisture content significantly
lower on the experimental plot than on the
control plot. Bulk density was similar for
both plots.
The interpretation of whether a par-
ticular species grew significantly better
on the control or on the experimental plot
depended upon the tree variable measured.
On the basis of three or more of these
dependent (tree) variables, the majority of
species grew significantly better on the
control than on the experimental plot. The
results of Student's "t" tests for the tree
variables (i.e. root biomass, shoot length,
leaf weight and basal area) comparing ex- .
perimental with control plot indicated that
black gum exhibited the least variability
in growth between the experimental and
control plot as indicated by the low £"t"
value (Table 6). Rhododendron had the
poorest growth of all species in that all
replicates on both plots succumbed by the
end of the winter of 1976-1977, presumably
from the abnormally cold temperatures.
Tree data collected in 1976 and 1977
from the five experimental gas barrier
techniques and the experimental screening
area (which serves as a control for the
barrier techniques) for American basswood
and Japanese yew are given in Table 7- For
American basswood, the gravel/plastic/vents
trench and clay barrier mound on the land-
fill supported significantly better growth
(99$ c.l.) than did the experimental screen-
ing area which had no special treatment and
represented typical landfill conditions.
This was true for all the dependent (tree)
variables measured excluding root biomass.
On the other hand, Japanese yew showed no
significant differences between the barrier
techniques and the experimental screening
area.
In order to- estimate the relative
effect of the soil variables on growth of
trees on the landfill plot, multiple,
stepwise-regression analysis was performed
for American basswood because this species,
unlike all the others, was replicated 62
times and, therefore, provided for the best
assessment of the effect of the soil fac-
tors on tree growth.
Multiple regression analysis of shoot
201
-------
TABLE 6. RELATIVE TOLERANCE OF SPECIES TO LANDFILL CONDITONS
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
111
15
16
17
18
19
a. Rank
most
b. * "t"
a Species
black gum
Norway spruce
ginkgo
black pine
bayberry
mixed poplar
white pine
pin oak
Japanese yew
American basswood
American sycamore
red maple
sweet gum
euonymus
green ash
honey locust
hybrid poplar
weeping willow
rhododendron
1 - the best growth when experimental plot
tolerant of landfill conditions.
= the sum of the "t" statistics for shoot
* "t" Statistics b
2.66
3.22
^.95
6.59
6.62
8.13
8.94
8.96
8.98
9.^8
10.66
10.95
12.62
14.25
14.87
15.05
20.33
21.20
All plants died
is compared to the control plot, i.e.
length in 1976: leaf weight , basal
area increase, root biomass and shoot length in 1977 comparing the experimental area
with the control.
TABLE 7. MEAN VALUES FOR TREE VARIABLES FOR EACH
GAS BARRIER TECHNIQUE FOR 1977
Planting
Technique
Trench- Plastic/ ,
vents/, gravel
Trench- clay/
vents ,A
Trench- clay
no vents
Mounds-no clay
Mounds- clay
Experimental
screening area
Species
Jap. Yew
Basswood
Jap. Yew
Basswood^
Jap . Yew
Basswood
Jap . Yew
Basswood
Jap. Yew
Basswood
Jap. Yew
Basswood
Root
Biomass
(mg)
516
800
74
153
616
1069
1015
622
1062
930
572
644
Basal
Area
(cm2)
17.0
73.3*
9.3
0.0
26.0
23.9
14.0
31.3
6.2
6o.O*
45.0
26.8
Leaf
Weight
(g)
1.24
3.97*
o.4i
0.02
0.59
2.21
0.64
1.89
0.8
3.40*
10.98
1.04
Shoot Length
1976 1977
(inches)
5.2
12.41*
0.52
1.06
5.1
7.19
6.9
10.98*
7.1
12.1*
5.0
7.U
2.61
8.98*
2. it3
.66
2.96
5.58
1.84
6.66*
2.78
8.52*
2.17
3.84
Grew significantly better than the experimental screening area @ 99% C.L.
4 of the 6 replicates died during 1977
Landfill gas content was significantly higher than all other areas in 1976
202
-------
length data shows a correlation with the
carbon dioxide, oxygen, temperature, bulk
density and moisture content (R2=53^).
These same variables explained the differ-
ences in leaf weight (R -53$)j basal area
(R2=63$), and root biomass (R -39"/o).
Simulated Landfill Studies
Both red and sugar maple trees fumi-
gated with the COg-CR), mixture were in
noticeably worse condition than the con-
trols at the termination of the U8-day
experiment comparing the effects of simu-
lated landfill gases with those of flooding
on two maple species. The main symptoms
were chlorosis and abscission of the lower
leaves.
The rate of transpiration which is
inversely related to stomatal diffusive
resistance was significantly less (P <.01)
for the sugar maples fumigated with C02 and
Cm than the control on day-2^. However,
red maple seedlings fumigated with CO^ and
CHij. showed no significant difference in
transpiration from the control at any time
during the experiment. The sugar maples
grown in flooded soil showed a significant
decrease in transpiration rate on the 3rd
day of the treatment whereas the red maples
which were flooded did not show a decrease
in transpiration until day-U-2 of the
experiment.
Analysis of variance of the first
tomato experiment showed that there was no
statistically significant difference be-
tween the three treatments (Table 8). All
the plants receiving high C02 and CHl^. con-
centrations exhibited adventitious root
development on the stems above the glass
lids.
TABLE 8. TOTAL INCREASE IN HEIGHT, FOLIAR
DRY WEIGHT, AND TOTAL NITROGEN
CONTENT OF THE LEAVES OF TOMATO
PLANTS* AT THE TERMINATION OF
EXPERIMENT 1
TREATMENT
Total
Nitrogen ($)
Total Dry
Weight (g)
Total Increase
In Height (cm)
A
1.9
13.1
16.7
B
1.6
12. b
10.2
C
1.9
13.1
16.7
In experiment 2 the plants that were
treated with air or low 02, but no CHlj. or
C02 (Treatments A and B) grew significantly
better than did the plants receiving high
C02 with or without CHI). (Treatments C and D)
(Table 9). The visual appearance of the
plants also bore out this relationship.
TABLE 9. TOTAL INCREASE IN HEIGHT, FOLIAR
DRY WEIGHT, AND TOTAL NITROGEN
CONTENT OF THE LEAVES OF TOMATO
PLANTS* EXPERIMENT 2
TREATMENT
A
Total
Nitrogen
(#)
Total Dry
Weight
(g)
2.58a 2.6Ua 1.68b 1.89b 1.80b
9.^a 9.la 3.8c 2.2c 5.9b
* Each value is the mean of 7 replicates
Total
Increase
In Height
(cm) 20.9a 21.la 6.0c 5.0c l6.6b
* Mean of h replicates
All values in row followed by an a are
greater than values followed by a b or <
(P<0.01). Values followed by a b are great-
er than values followed by a < (P<0.01).
In the third experiment, the plants
that were treated with low 02 and low C02
(Treatment A) grew significantly better
than the plants given high C02 with high or
low Op (Treatments B and C) (Table 10). By
the 10th day of exposure all the plants
given high C02 (Treatments B and C) exhib-
ited adventitious root development on the
shoots and a general chlorosis of the
leaves. The plants remained in this condi-
tion throughout the experiment exhibiting
little additional growth.
TABLE 10. TOTAL INCREASE IN HEIGHT, FOLIAR
DRY WEIGHT AND ADVENTITIOUS ROOT
DEVELOPMENT OF TOMATO PLANTS AT
THE TERMINATION OF EXPERIMENT 3
TREATMENT
A B C
Total Increase
In Height (cm) 4l.3a 2. Ufa O.Ub
(continued)
203
-------
TABLE 10. (continued)
TREATMENT
B
Mean Dry
Weight (g)
Adventitious
Root Development
9.0a 3.013 2.5b
* All values in row folio-wed by an a are
greater than values followed by a b.
(P < 0.01).
In the Vth experiment, the plants that
were treated with low 02 (control) or 10%
C02 (Treatments A and B) grew significantly
better than the plants treated with 20f0
C02 (Treatment C)(Table 11). The latter
plants all exhibited adventitious root
development and general chlorosis by the
17th day of exposure.
TABLE 11. TOTAL FOLIAR NITROGEN AND DRY
WEIGHT AND INCREASE IN HEIGHT
AND ADVENTITIOUS ROOT DEVELOP-
MENT OF TOMATO PLANTS* AT THE
TERMINATION OF EXPERIMENT U
TREATMENT
A
Total
Nitrogen (%)
Mean Total
Dry Weight
(g)
3. la
11. Oa
2.5a 2. ka
9.5a 2. Ob
2. Ob
8.5a
Total Increase
In Height (cm) hl.Oa 51. 3a 3.8c 29.
Adventitious
Root
Development - - + +
* Mean of k- replicates
All values in a row followed by an a are
greater than values followed by a b or c
(KD.Ol). Values followed by a b are
greater than values followed by a c
By the 17th day of exposure all the
plants receiving k5% CE^ (Treatment D)
exhibited adventitious root development.
These plants also exhibited chlorosis of
the lower leaves.
Discussion
Although landfill gas was not signif-
icantly correlated with death of trees in
the field screening experiment (r=.238), it
was associated with dead trees in a small
number of instances. Most of the tree
deaths, however, could be attributed to
factors other than landfill gas. Low soil
moisture, transplanting difficulties,
animal damage, and winter injury can ex-
plain many of the deaths.
Although landfill gas concentrations
in the experimental plot were not high
enough to account for actual death of many
of the plants, representative landfill soil
conditions were of adequate magnitude to
detect the order of relative tolerance of
the surviving trees as listed in Table 6.
This listing resulted from a consideration
of four tree variables including leaf and
root biomass, shoot length (1976 and 1977),
and basal stem area.
It is interesting that of the nine
most tolerant species, only three i.e.
black gum, bayberry and pin oak, (26) have
been reported to be able to withstand low
oxygen tension in the soil, one of the
criteria for selecting experimental species
(Table 1). However, seven of the first ten
species were 3-feet or less in height when
planted, whereas seven of the last ten
species in Table 2 were 6-feet or taller
when planted. Possibly the size of the
tree as well as the biological ability of
species to withstand low oxygen, is impor-
tant in selecting vegetation for completed
sanitary landfills.
In order to assess the role of the
selected soil variables in predisposing
these species to landfill tolerance, mul-
tiple regression analysis was performed.
Results indicated that the soil variables
oxygen, carbon dioxide, temperature, mois-
ture content, and bulk density explained a
significant portion (95% C.I.) of the
discrepancies in tree responses to landfill
conditions.
The effectiveness of each gas barrier
technique in preventing methane gas migra-
tion into the trenches may be evaluated by
considering the ratio between the methane
concentrations around the periphery of the
trench and those inside the trench. In the
gravel/plastic/vents trench and clay barri-
er trench, the ratios are 207:1 and 5^:1
204
-------
respectively, indicating that these trenches
have functioned effectively in keeping out
methane gas. On the other hand, for the
clay/vents trench, the 1:1 ratio indicated
that this gas barrier technique was not ef-
fective in preventing the migration of
methane from the refuse into the trench.
Landfill gas was never detected in either
of the two mounds. Vegetation growth was
also best in the gravel/plastic/vents
trench and the two mounds.
Sugar maple was intolerant of flooding
as evidenced by the statistically signifi-
cant decrease in transpiration rate after
only one day of flooding and the loss of
all leaves by the termination of the exper-
iment. The transpiration rate of red maples
did not decrease until the U2nd day of
flooding. The fact that red maple is more
tolerant of flooding than sugar maple has
been reported in the literature (21).
Flood tolerance has been attributed to
more than one adaptive mechanism in several
species (25). The adventitious root devel-
opment on the flooded red maples in this
experiment have been found to occur on many
other "flood tolerant" species and are be-
lieved to contribute to flood tolerance to
some degree. Such an adaptation was not
observed on the red maples fumigated with
simulated sanitary landfill gas mixtures.
This is not surprising since adventitious
root development is dependent upon the pres-
ence of water. Other adaptations which are
believed to contribute to flood tolerance
which are not as water dependent include
the ability to withstand elevated levels of
002 in 'the soil (25) and to undergo anaer-
obic root respiration without the produc-
tion of inhibitory concentrations of etha-
nol. Mechanisms such as these could ex-
plain why the differences between the two
species were more pronounced in their re-
sponse to flooding than to soil contami-
nation with simulated landfill gas. The
inability to develop adventitious roots in
response to landfill gas contamination
would reduce the advantage enjoyed by flood
tolerant species whereas other mechanisms
contributing to flood tolerance such as the
ability to withstand elevated levels of C02
in the soil or undergo anaerobic respira-
tion in the roots which are not inhibited
by lack of water and would continue to
supply some protection.
Carbon dioxide contamination in the
root zone of tomato plants in solution
culture was toxic when the concentration of
C02 averaged 17.0$ during the experimental
period. Mien 002 concentrations averaged
8.8% or less no symptoms were observed,
indicating that there was a threshold level
between 9 and 17$ at which 002 became toxic
under these experimental conditons. Tomato
plants exposed to 17$ C02 exhibited pro-
gressive chlorosis and abscission of the
lower leaves, adventitious root development,
chlorosis of the entire plant, and a reduc-
tion in the growth rate. Exposing tomato
roots to concentrations of 002 between 25
and 36$ resulted in earlier and more severe
sympton development on tomato plants than
did 17
-------
less than 3 feet. During this study,
this factor appeared to be more impor-
tant than the biological ability of a
plant to withstand low oxygen environ-
ment s.
Red maple, which is flood tolerant, was
found to be more tolerant of soil con-
taminated by simulated landfill gas
than sugar maple, which is not toler-
ant of flooding.
Tomato plants growing in sand-solution
greenhouse cultures were severely
damaged by exposure to carbon dioxide
concentrations of 1J% or greater in
the root zone. This response was not
influenced by the presence or absence
of high concentrations of methane or
fluctuations in the Op concentrations,
provided the 0^ in the root zone was
not less than 2%.
RECOMMENDATIONS
Those responsible for planting vegeta-
tion on completed landfills should
avail themselves of current research
on the adaptability of species to
landfill conditions and avoid the use
of non-tolerant species.
The use of a barrier technique for
excluding landfill gas from the root
zone of vegetation should be consider-
ed when planting on a former landfill.
Two methods to consider are: (a) a
mound of soil over the existing cover,
(b) a lined and vented trench back-
filled with suitable soil.
The use of smaller planting stock
might also increase the chance of sur-
vivability.
Adequate irrigation of the plants es-
tablished on a landfill is an impor-
tant contribution to their survivabil-
ity.
Further studies should be undertaken
to determine if the ability to with-
stand high levels of carbon dioxide in
the root zone is a characteristic of
flood tolerant species.
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Rutgers University, New Brunswick,
New Jersey, 6 p. , 1969.
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22. Hoeks, J. Changes in Composition of
Soil Air Leaks in Natural Gas Mains.
Soil Science. 113:^7-5^, 1970.
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Hook, D.D, C.L. Brown and P.P. Kormanik.
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and Forestry, Park Recreation and
Cultural Affairs Adm. from Landfill to
Park. Brochure, 1*5 p. , December, 197^.
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Spring Precipitation and Height Growth
of Western Yellow Pine Saplings in
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Pepkowitz, L.P. and J.W. Shive.
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Rapid Wet-Digestion Micromethod.
Industrial and Engineering Chemistry.
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sponses of Red and Black Raspberry
Root Systems to Differences in 02,
C02 Pressures and Temperatures. Proc.
of the Am. Soc. for Hort. Sci. Vol.
75:^02, 1956.
Ralston, C.W. Estimation of Forest
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Forest Research. 1:171,
Spurr, S.H. Forest Ecology. Ronald
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North Am. Forest Soils Conference,
Michigan State University, East Lans-
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208
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EFFECTS OF PARTICLE SIZE ON LANDFILLED SOLID WASTE:
COLD CLIMATE STUDIES
Dave Hechler, Thomas, Dean, & Hoskins, Inc.
Great Falls, Montana
ABSTRACT
This research program was initiated with the overall objective of determining the
effects of milled refuse particle size on landfilled solid waste.
Four experimental test plots were constructed using four different particle size
distributions. Each pit representing a specific milled refuse particle size will be evalu-
ated in an attempt to correlate particle size with different parameters. The parameters
under study are: wind displacement of milled refuse, differential settlement of compacted
milled refuse, and attraction of vectors, rodents, birds and wildlife to the milled refuse.
Monitoring of the test pits was just initiated so preliminary results are not avail-
able to date. Particle size distribution curves are developed herein for the milled refuse
used. Four breakdowns of the composition of the raw solid waste prior to milling are in-
cluded. Moisture content and field density test results are shown herein.
This report was submitted in fulfillment of Grant R805012 by the Montana State Depart-
ment of Health and Environmental Sciences under the sponsorship of the U. S. Environmental
Protection Agency. This report covers the period from July 25, 1978, to December 20, 1978,
and work will be completed on July 3, 1980.
INTRODUCTION
BASIS FOR STUDY
Design criteria is inadequate or total-
ly unavailable, to date, for correlatiing
milled refuse particle size with wind dis-
placement problems, settlement different-
ials, vector problems, etc. This lack of
design criteria or operational parameters
could have a detrimental effect on future
milled refuse operations. States need more
detailed data to establish acceptable pa-
rameters for operation and maintenance of
shredding facilities. They also need more
detailed data to adequately adopt proper
regulations governing the disposal of mil-
led refuse. Some states are adopting reg-
ulations that define particle size limita-
tions without any proven data to substanti-
ate these limitations. Reliable design
criteria is needed to relate the effects of
particle size on operational and esthetic
variables.
PARAMETERS TO BE EVALUATED
The purpose of the project is to evaluate
the following variables:
1. The effect of wind velocities on the
displacement of compacted milled refuse
without cover.
2. The amount of differential settlement
occurring in compacted milled refuse
correlated with particle size.
3. The initial density in compacted milled
refuse and subsequent density with re-
lation to time resulting from consoli-
209
-------
dation of refuse using varying par-
ticle sizes.
The presence or absence of vectors,
rodents, birds, and wildlife corre-
lated to particle size of refuse.
Any observations of additional param-
eters that can be correlated with the
different particle size will be noted
throughout the project period.
PARTICIPANTS IN STUDY
This project is being funded by a
research grant through the Solid and Haz-
ardous Waste Research Division of the Mu-
nicipal Environmental Research Laboratory
of the Environmental Protection Agency and
by the Solid Waste Division of the Montana
State Department of Health and Environmen-
tal Sciences.
This project was undertaken by the
Montana Department of Health and Environ-
mental Sciences in cooperation with the
City of Great Falls. The firm of Thomas,
Dean & Hoskins, Inc., of Great Falls, Mon-
tana, was utilized to provide the consult-
ing engineering services required. The
City of Great Falls refuse shredder was
used to produce the different particle
sizes of refuse for placement in test pits.
EXPERIMENTAL WORK
PROCEDURAL REQUIREMENTS FOR STUDY
The Environmental Protection Agency
was very specific on the methods and pro-
cedures they wanted followed to develop the
research data needed. Project work was not
initiated until the Environmental Protec-
tion Agency, Montana State Department of
Health & Environmental Sciences, and Thomas,
Dean & Hoskins, Inc., were all in agreement
as to the methods and procedures that would
be followed to complete the research work.
In general, the project was to include
four test plots or holes with dimensions
20 feet wide, by 35 feet long, by 6 feet
deep excavated in the ground. Each test
plot was to be filled with compacted refuse
of a specific particle size. The milled
refuse in the first test pit was proposed
to ideally have 70 percent passing a two
inch particle size, the second pit, 70 per-
cent passing a four inch particle size, the
third, 70 percent passing a six inch par-
ticle size, and the fourth pit, 70 percent
passing an eight inch particle size. The
test plots were to be located end to end
with the long side of the four pits facing
the prevailing southwest winds. These test
pits were to be located in such a configu-
ration and at a location that would be un-
obstructed in regard to the prevailing
winds.
Following completion of the installa-
tion of the refuse in the pits, each pit
was to be enclosed with one-half inch mesh
fencing.
Monitoring data over a two year period
is to provide information on wind displace-
ment and settlement of the differing sizes
of milled refuse. It also is to provide a
correlation between vectors, rodents, birds
and wildlife attraction to the varying par-
ticle sizes.
FIELD CONSTRUCTION OF TEST PITS
On August 18, 1978, Thomas, Dean S Hos-
kins, Inc., was given the go-ahead to ini-
tiate the project work required for the
study.
The site selected for construction of
the test pits was located on a hill one-
quarter mile east of the existing City of
Great Falls landfill. This site was selec-
ted because the wind blows across the site
unobstructed by any physical features such
as trees, buildings, etc. The haul dis-
tance to the test site was approximately
equal to that required to get to the City
landfill site.
Four test pits were excavated with di-
mensions of 21'x36'x6' deep. A Caterpillar
Traxcavator Model 977 with a 2-3/4 cubic
yard bucket was used to excavate and shape
the four test pits. Each test pit was sep-
arated from the adjacent pit by 8 feet of
undisturbed soil. Access to the interior
of each pit was down a steep slope into the
hole .
Following completion of the excavation
phase of the test pits, a carpenter instal-
210
-------
led the plywood sidewalls. These plywood
sidewalls were installed to provide a pit
with the exact dimensions of 20 feet wide
by 30 feet long. It is impossible to ex-
cavate a hole with exact dimensional tol-
erances so the plywood sidewalls were in-
stalled to assure that the pit dimensions
would be accurate. Knowing the exact di-
mensions of the pit, it would be possible
to determine the volume and subsequently
the wet density of the "in-place" refuse.
The plywood sidewalls were installed to a
height six inches below the existing ground
surface to keep from obstructing any wind
from blowing against the top surface of the
compacted refuse. Two by four framing pro-
vided support for the plywood sidewalls.
An 8 foot long portion of the plywood side-
wall construction was not installed until
after the compaction equipment was driven
into each test pit.
The milled refuse for the test pits
was provided by the City of Great Falls
shredding facility. This solid waste re-
duction plant was constructed in. 1975 with
two Heil vertical shaft grinding mills;
one 20 ton per hour unit and one 15 ton per
hour unit.
The shredding facility has a magnetic
separator unit for removal of ferrous metals
installed on the outlet conveyor belt. At
the time that this project was initiated,
the magnetic separator was not in operation.
Therefore, the milled ferrous metal material
was included in the refuse placed in the
test pits.
Weigh scales are installed at the waste
reduction plant to weigh all incoming refuse
and all milled refuse prior to disposal.
All the refuse delivered to the test pits
was weighed on these existing scales.
It was proposed that the mills would
produce a specific, but different, particle
size distribution of refuse for installing
in each of the four test pits. We construc-
ted a sieve unit or trommel for analyzing
a milled refuse sample in regard to particle
sizes. The trommel was designed to sieve
out particle sizes of dimensions 1/2 inch,
1 inch, 2 inch, 4 inch, 6 inch, and 8 inch.
Hammer adjustments in the mills could then
be made to approximate the size of particle
required.
The sieve unit consisted of two 13.5 ft.
long circular trommel units, 22 inches in
diameter with a support frame. Each of the
two cylindrical units contained three dif-
ferent screens or sieve sizes. Two trommel
units were required to process the six dif-
ferent mesh sizes required. They were de-
signed to be manually turned by hand. The
upper end of the trommel frame was raised
above the floor 13-1/4 inches to allow par-
ticle flow from one end to the other. The
refuse would be placed in the end of the
trommel unit with the smallest sieve size
near the head end of the unit. As the trom-
mel was turned, the refuse would fall and
tumble through the one-half inch screened
area down to the second screen with one inch
openings, past the third screen with two
inch openings, and out the end of the trom-
mel unit onto a container on the floor. At
this point, the refuse would be rerun through
the second trommel unit sieving it to 4 inch,
6 inch, and 8 inch particle sizes. Any-
thing larger than 8 inch would pass out the
end of the trommel. In this way, it was
possible to run a sieve analysis using six
different sieve sizes.
Grinding shredded refuse to a consistent
particle size was an area of concern during
the placement operation. Hammer mills such
as Great Falls' unit tend to be subject to
hammer wear on a day-to-day basis. As the
hammers wear, the particle size of the mate-
rial varies also. The more the hammers wear,
the larger becomes the particle size. So
it was important that once shredding was
started and placement begun, the operation
continued uninterrupted until a specific
pit was complete. Getting the refuse to the
site, into the pits, and compacted in place
without delays was difficult due to the many
operations that had to be coordinated at
one time.
Milled refuse was hauled to the pit in
65 cubic yard transfer trailers which carry
a pay load of approximately 30,000 to 32,000
pounds per load. Five to six loads were
required per pit. The pulverized material
was compacted into the 65 cubic yard trans-
fer trailer at the pulverizer facility.
The compactor unit that presses this mate-
rial into the truck does so obtaining a wet
density of approximately 500 Ibs. per cubic
yard.
For each 65 cubic yard load of refuse
211
-------
milled for placement in a test pit, one
composite sample was sieved and one moist-
ure content was determined. To get the
samples for these tests a 30 gallon con-
tainer was placed underneath the bottom of
the discharge conveyor belt as the refuse
tumbled off the conveyor belt prior to com-
paction into the transfer trailer. The 30
gallon container was partially filled each
time a sample was taken to develop a com-
posite sample for each 65 cubic yard load.
The moisture samples were collected in
plastic bags and dried in the ovens at our
laboratory following the days run.
When the 65 cubic yard transfer trailer
was completely filled, it was then weighed
and sent to the test pit site area. The
refuse was then stockpiled at the site.
A John Deere backhoe-loader was used to
pick up the refuse and place it in lifts
into the specified pit. Once the refuse
was discharged into the pit, the backhoe
was used to spread the refuse to a uniform
depth of 18" to 24". Then a Caterpillar
dozer on tracks located down in the bottom
of the pit was used to drive over the mate-
rial and compact it to the required density
of approximately 1,000 pounds per cubic
yard.
Placement of the refuse depended on
many different operations. The City pul-
verizer experienced some breakdowns which
stopped production of the milled refuse
and subsequently shut down the placement
of the refuse in the pits. Also, there
were some backhoe and dozer equipment
breakdowns at the test pit site which shut
down the refuse placement operation. Ex-
cessive windy weather, rain, and snow con-
ditions sometimes shut down the placement
operation also.
Field installation of the milled refuse
required two pieces of equipment. A John
Deere backhoe was used to spread the milled
refuse in lifts. Then a Caterpillar Trax-
cavator which we located down in the pit
was used to compact the refuse. Compaction
was essentially complete when there was no
indentation left by the dozer tracks on the
surface of the refuse. This required about
six passes over the refuse with one track.
The Caterpillar Traxcavator weighed
36,500 pounds with a track width of one foot
six inches and an on-ground length of nine
feet six inches. The three-bar street pads
on the tracks provided a compressive down-
ward force of 1,281 pounds per square foot.
Following completion of the installa-
tion of each load of approximately 65 cubic
yards of refuse, measurements were made to
determine the in-place wet density of the
load. Knowing the weight of the delivered
load of refuse and the field measured vol-
ume of the compacted refuse in place, the
wet density could be determined. See Fig-
ure A-l for the location of the density
check points. We attempted to maintain a
wet density of approximately 1000 Ibs. per
cubic yard in place. Densities varied from
approximately 835 up to over 1,364 Ibs. per
cubic yard for an average somewhere around
1,000 Ibs. per cubic yard for all pits. It
was our opinion that obtaining a density of
1,000 Ibs. per cubic yard was probably in
excess of what most landfill sites accom-
plish in Montana. Heavier densities may be
obtained in areas where land is scarce, but
in Montana where land is more readily avail-
able there is generally less compactive ef-
fort applied to the waste.
To measure settlement that occurs with-
in the lower portions of the pit, we instal-
led two foot diameter steel discs approxi-
mately 4 to 5 feet above the bottom of each
pit. The reason for installing the plates
2 to 3 feet below the surface was that the
refuse in the top portion of each pit will
probably be displaced by wind velocities
throughout the two year study period. With
these plates installed below the surface,
we can determine what settlement takes place
in the different pits throughout the period.
The 1/4 inch metal discs were installed,
four per pit, at the locations given in
Figure A-l.
Following completion of placement of
the refuse in each pit, we excavated back
down to the surface of these metal discs
and installed 4 inch diameter pipe. This
was to allow for access to the top of the
metal discs throughout the project period.
We attempted to dig through the compacted
refuse by hand which proved almost impos-
sible. But we were finally able to use a
gasoline powered fence post auger and very
carefully dig down through the refuse to
the metal discs. Then we cleaned the holes
out by hand and installed the 4 inch diame-
212
-------
ter pipes for access to the tops of the
metal plates.
Following completion of the placement
of the refuse and the installation of these
plates, the pits were covered with plastic
to prevent the refuse from blowing and
being displaced prior to installation of
the fenced enclosure.
The fencing encloses four sides of each
pit allowing for a three foot buffer area
on the sides of each pit and a four foot
buffer area on the ends of each pit. The
refuse that is displaced by the wind will
settle in this buffer area where it can be
collected for weight determination during
the monitoring stage of the data collection
phase of this project. The fencing mate-
rial around the periphery of each pit is
1/2 inch mesh to allow for retaining the
1/2 inch or larger material within the pit
area. Anything smaller than 1/2 inch may
get through the fence and be blown away.
Originally, the area over the top of
each test pit was to be enclosed with a
chicken wire mesh to prevent the refuse
from soaring up out of the pit. However,
the Environmental Protection Agency felt
that this top covering should be elimina-
ted to allow for bird access to the area,
since this is one of the items to be noted
in the project.
DATA COLLECTION AND FIELD MONITORING
Previous mention has been made of the
sieve tests that were conducted during the
placement of the refuse material in the
test pits. Also, moisture tests and in-
place density tests were taken during that
same period of refuse placement. In addi-
tion to the test data recorded on the
initial construction phase of the project,
additional data will be collected through-
out the remaining project period. As men-
tioned before, settlement determinations
are to be made on the test plates installed
on the interior of each test pit. Also,
elevation checks are to be made on the test
pit surfaces, Figure A-l, on a periodic
basis to determine if settlement takes
place on the surface of the pit. However,
it should be noted here that any displace-
ment of the material, due to wind, will
also lower the top working surface of the
pit and, therefore, it will be difficult to
determine whether settlement took place on
the surface or whether the material was
actually displaced due to wind. However,
as time progresses and the top surface
builds up a scum type layer preventing wind
displacement of the material, then it will
be possible to determine if settlement
takes place due to deterioration of the pit
itself. Other measurements in regard to
vector, rodent activity, and bird activity,
are to be made.
A comparison shall be made to deter-
mine the number of flies attracted to each
plot to see if the different particle size
can be correlated with fly activity. A
Scudder Grille shall be used to attract the
flies for counting. Fly counts shall be
made once per week, from May through Sep-
tember the first year, and once per month
from May through June 30, the second year.
Rodent activity shall be checked in an
attempt to correlate it with the size of
the milled refuse. Since each test plot is
to be fenced, two small 6 inch diameter
access holes were cut in the fencing on the
northeast and southwest sides of each test
plot. This will allow the rodents to gain
access to the area should they desire.
Rats have never been observed in the Great
Falls area, but gophers and field mice are
common. To ascertain the rodent species,
snap traps shall be set in the area of any
runs that develop. Trap checks shall be
made once per week from May through Sep-
tember the first year, and once per month,
from May through June 30, the second year.
Bird activity shall be monitored for
each test pit. During each monthly or bi-
monthly visit to the site, bird activity
shall be noted in and around each test plot.
The test pit is open on top to allow for
bird access to the refuse.
Analysis of wind effects on the com-
pacted refuse will continue throughout the
project period. Measurements of wind cor-
related with amount of refuse displaced is
critical in the early stages of the project
following material placement in the test
pits. Wind direction and velocity data
shall be provided by the U.S. Weather Bur-
eau for the periods of collection to see if
any correlation exists between the particle
size of the material displaced and the
213
-------
average and maximum wind velocity data for
that period. Temperature and precipitation
data will also be collected.
RESULTS TO DATE
At the time of this writing (December,
1978) results are limited. Tests performed
during construction of the test pits are
complete, but field monitoring following
installation of the pits is just beginning.
The only parameter monitored during this
initial two week period has been wind data.
When the oral presentation is made, more
data should be available.
Located in the appendix of this report
are curves indicating the different results
of the sieve analysis for each pit. Figure
A-2 through A-5 indicates the variation in
the particle sizes within each pit. There
is a considerable range of variation due to
hammer wear in the mills themselves over
the period while the refuse was being
placed in the pits. It usually took from
two to three days to get one pit filled
with compacted refuse.
We attempted to obtain a uniform par-
ticle size for each pit but found out that
this was impossible due to limitations of
the hammers in the mill and also the limi-
tations of the raw domestic refuse prior to
milling.
In this project, we were not required
to run sieve analyses on the raw refuse,
although we did run one sample through just
for informational purposes. While attempt-
ing to mill an 8 inch particle size for the
last pit, we found it impossible to obtain
70 percent passing (30 percent retained) an
8 inch screen. Because of this difficulty,
we wanted to determine whether this limita-
tion was caused by the configuration of the
hammers inside the mills or by the size of
the incoming raw refuse. As a result, we
ran the test on the raw refuse and found
that the raw refuse itself without even
milling would not meet the criteria of 30
percent retained on an 8 inch screen. The
one sample we did run (Figure A-6 in appen-
dix) on the raw refuse indicated that 30
percent of the sample was larger (70 per-
cent passing) than a 4-1/4 inch screen.
With a normal gradation it would then be
impossible to get anything larger than what
the raw refuse gradation was coming into
the pulverizer unit. With the majority of
the hammers removed from the mill, the lar-
gest size particle we could mill was used
for pit #4. A 6 inch particle size (70 per-
cent passing) was used for the top lift of
pit #4 and this was the largest particle
size of any loads delivered to the test
site .
The curves for pit No. 1 indicate that
the top lift has 70 percent passing a 2-1/2
inch sieve. However, the lower lifts in
pit No. 1, lifts one through four, vary in
size from approximately 3-1/2 inches to
4-1/2 inches at the 70 percent passing line.
Pit No. 2 has a top lift at approximately
4-1/2 inches particle size with the lower
lifts varying from 4-1/2 inches down to 3
inches in particle size at the 70 percent
passing line. Pit No. 3 also has a top lift
of approximately 4-2/3 inch particle size
with the lower lifts varying from 4-1/2 in-
ches up to 5-1/2 inches approximately at the
70 percent passing line. Pit No. 4 has a
top lift using a 6 inch particle size. The
lower lifts in pit No. 4 varied from approx-
imately 4-1/2 inches up to 5 or 5-1/4 inches
in diameter at the 70 percent passing line.
This was the largest particle size in any of
the four pits.
On November 4, wind gusts in excess of
80 mph fanned a fire at the City landfill
site and wind-carried cinders started a fire
in test pit No. 3. The fire ruined the pit
and chances to obtain any future test data
from it. Pit No. 3 is therefore eliminated
from the project work.
The composition of the raw solid waste
as sampled for each test pit is shown in
Table A-l in the Appendix. The category for
"Ash, Rocks & Dirt" was included under fines
since the material was too small to separate
from other fines. Grass cuttings were also
included under fines except for in pit No. 1
where an attempt was made to place it under
garden waste. The average composition in
percent by wet weight shown represents the
typical composition of municipal waste for
the Great Falls area as would be received
in the fall of the year.
The table also indicates for comparison
purposes only, data from the Proceedings
of the 1970 National Incinerator Conference
and the Land Disposal Project for Boone
County Field Site, Walton, Kentucky. With
the data modified to include the same param-
214
-------
eters, the Great Falls refuse falls near
or within the range of the other two sets
of data. Our metal content was slightly
higher than the other studies revealed but
this was due to one sample being high. We
feel this is a general indication that the
refuse used in the test pits was similar to
that produced by other areas.
Density and moisture content data is
shown in Table A-2 in the Appendix. An
attempt was made to try and be consistent
in the compactive effort applied to each
lift of refuse but this was not always done.
The densities of the lifts varied from 835
Ibs./C.Y. up to 1,364 Ibs./C.Y. with over-
all densities of 1,117; 991; and 987 Ibs./
C.Y. for pits 1, 2 and 4 respectively.
This compares closely to our goal of 1,000
Ibs./C.Y. Pit No. 3 was omitted from the
data determination due to the fire which
destroyed the pit as previously mentioned.
The dry weight moisture contents varied
from 13.2 to 32.01 percent for the different
lifts with the averages being 19.62, 20.85
and 21.19 percent for pits 1, 2 and 4 re-
spectively. Normal moisture contents for
municipal refuse vary from approximately
20 percent up to 60 percent so these per-
centiles in Great Falls would be on the
low side of this range.
On November 29, 1978, the test pits
were completed with the fencing installed
and the plastic covering removed. On Decem-
ber 1, 1978, a snow storm covered the test
pits with a snow cover that increased with
later storms. Windy periods caused a heavy
crust to develop on the snow and as of this
writing on December 20, 1978, (a written
copy of each presentation had to be submit-
ted by January 1, 1979), the surfaces of
the test pits were still unchanged. A warm-
thaw with prolonged temperatures above
freezing without additional precipitation
will be required to dry the surface of the
pits. Winds in excess of 40 mph have
recently occurred although little refuse
has been displaced due to the snow crust on
the pits. Internal settlement and surface
settlement of the test pits will not be
evaluated for the first month's operation
until the end of December. Fly counts and
rodent trapping are not checked during the
winter months and there has not been any
evidence of bird activity at the site as of
this writing.
To date it is too early to recommend
any specific size of milled refuse particle
as having advantages over a smaller or
larger size. Field monitoring has just
begun and will continue for another 1-1/2
years providing more data as time progresses.
If one particle size is proven to have
advantages over any other particle size, it
will be difficult to consistently mill the
refuse to the preferred particle size with
the vertical shaft mills installed in Great
Falls. The sieve analyses indicate that when
grinding the smaller particle sizes, the
Heil units will not consistently produce
one size particle. The continual increase
in particle size is caused by the normal
wear of the hammers. When milling the larger
particle sizes of refuse, the particle size
varies with the particle size distribution
of the incoming raw waste. Hammer wear
would be experienced on any brand of shred-
der unit and is not unique to just the Great
Falls Milling units. It is possible that
a change in the design of some grinding
mills may be required if a limitation is to
be placed on the size of particle that must
be produced.
215
-------
IN3
cn
in
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DENSITY CHECK POINT
SETTLEMENT DISCS
CHECK
( T XV°)
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SURFACE ELEVATIONS
FIGURE A-l
ELEVATION CHECK POINTS
-------
100
90
80
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PARTICLE SIZE, Inches
PARTICLE SIZE DISTRIBUTION CURVE - TEST PIT #1 - MILLED REFUSE
-------
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PARTICLE SIZE, Inches
Figure A- 3 PARTICLE SIZE DISTRIBUTION CURVE TEST PIT #2 - MILLED REFUSE
-------
100
90
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PARTICLE SIZE, Inches
PARTICLE SIZE DISTRIBUTION CURVE - TEST PIT #3 - MILLED REFUSE
-------
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0 60
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PARTICLE SIZE, Inches
•igure A- 5 PARTICLE SIZE DISTRIBUTION CURVE - TEST PIT #4 - MILLED REFUSE
-------
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-------
TABLE A-l REFUSE COMPOSITION COMPARISIONS _,
Sample
Location
Pit *1
Fit #2
Pit *3
Pit *4
Avg. of
all pits
Avg . c £
Pits *
1968 An-
nual Avg . (x)
Boone Cnty.
Kentucky +
Boone Cnty.
w/o Misc . ^gp
Total
',. 'eight
Sepa-
rated
(pounds)
98.4
136.9
219.7
102.9
COMPONENT-PERCENT BY WET WEIGHT
Food
Waste
8.1
9.4
1.9
5.0
6.1
8.2
19.3
4.5
5.4
Garden
Waste
*10.4
1.9
22.7
9.7
11.2
Exclu-
ded
9.2
Exclu-
ded
Paper
55.8
38.5
28.1
35.8
39.6
£3.3
51.6
49.2
58.3
Rubber,
leather,
and
Textiles
9.6
2.2
0.4
2.2
3.6
4.8
4.6
10.3<>
12.2<>
Wood
0.2
3.6
0.9
1.2
1.5
2.0
3.0
4.1
4.9
Metal
5.4
16.9
7.9
13.2
10.8
14.5
10.2
9.2
10.9
Glass
6.8
9.9
4.9
5.7
6.8
9.1
9.9
7.1
8.4
Plastic
2.7
8.4
5.5
7.3
6.0
8.1
1.4
Incl.
w/
rubcer
Incl.
w/
rubber
Ash, rock,
dirt, fines
and
Miscellaneous
1.0
9.2
27.7
19.9
14.4
Exclu-
ded
6.3
Exclu-
ded
ro
ro
ro
A Grass included here for this test only.
* Excluding garden waste, ash, rocks, dirt, fines and miscellaneous.
(x) Estimated annual average National Refuse Composition on a yard waste-free & misc.-free basis-1970 Natl.
Incinerator Conference Proceedings.
+ Land Disposal Project Boone County Field Site, Walton, Kentucky, Jan. 1973.
O Includes plastics.
iff Excludes ash, rock, dirt, fines & misc. garden waste.
-------
TABLE A-2 DENSITY-MOISTURE SUMMARY SHEET
SAMPLE
DENSITY (x) OVERALL*
LOCATION LIFT LBS/C.Y. DENSITY LBS/C.Y.
Pit #1
TOTAL
AVERAGE
Pit #2
TOTAL
AVERAGE
Pit tt3
Pit #4
TOTAL
AVERAGE
1
2
3
4
5 & 6
1
2
3
4
5
Destroyed by fire
1
2
3
4
5
6
879
1099
1104
1128
1364
1115 1117
835
1260
833
1157
935
1004 991
852
1009
1108
1213
1066
862
1018 987
MOISTURE %
BY DRY WEIGHT
14.76
]9.21
31.23
17.93
14.95
19.62
22.48
13.20
19.84
16.73
32.01
20.85
17.82
14.39
29.04
25.79
22.95
17.12
21.19
HO Based on weight of refuse compacted in a field measured volume for
each lift of placed refuse.
* Based on survey elevations taken on bottom of empty pit and top of
i i u,j_l Ji.Tt (or volnmo tlotorininal- ion. Total weuihL oC all refuse in
pit- incJucU'il in del orm mat ion .
223
-------
ASSESSMENT OF MUNICIPAL SOLID WASTE DISPOSAL
IN SALINE/MARSHLAND ENVIRONMENTS
Michael S. Klein
and
Kenneth A. MacGregor
Management of Resources and the Environment
Glastonbury, Connecticut 06033
ABSTRACT
The research design, data acquisition methodology and preliminary results of assess-
ment of the environmental impacts of municipal solid waste disposal in coastal saline
environments is described. Secondary datawere gathered via computerized searches of
several data bases covering both the published scientific literature and unpublished fug-
itive literature. None of the literature specifically addresses the problem at hand, but
analysis of approximately 3,000 citations delivered revealed 217 useful documents.
A questionnaire mailed to 186 state solid waste and pollution control agencies
produce meaningful responses from 18 states. At least one hundred forty seven sites were
identified, of which at least 70 are still in operation. Some form of environmental moni-
toring has been performed at 70 sites.
INTRODUCTION
The forty-eight contiguous states are
located on the Atlantic and Pacific Oceans,
as well as on the Gulf of Mexico. When
Alaska, Hawaii, and Puerto Rico are consid-
ered, this range expands to include the
Arctic Ocean, Bering Sea, and the Caribbean
Sea. The physical and biological condi-
tions, therefore, range from arctic to tro-
pical along the 86,500 miles (HA, 300 km)
of U.S. shoreline which are subject to ti-
dal fluctuations. This shoreline encom-
passes part of twenty-two states, as well
as the Commonwealth of Puerto Rico (U.S.
possessions such as the Virgin Islands,
Guam, Marshall Islands, etc. were not con-
sidered within the scope of this study).
In the past, state and local govern-
ments, as well as many private citizens,
viewed the coastal zone as a low productiv-
ity, low value environment. Since a very
high percentage of our population is loca-
ted adjacent to coastal areas, these low-
lying lands have been used as depositories
for solid waste. As undeveloped land be-
came increasingly scarce, municipal solid
waste was used as landfill to create addi-
tional dry land along the coasts. However,
in recent years coastal lands have been
formally identified as having significant
ecological, flood control, water purifica-
tion, and aesthetic values. Attempts have
been made to calculate the economic value
of particularly high productivity environ-
ments such as salt marshes.
This recognition has lead to several
legislative and executive actions designed
to protect these values. The state and
federal environmental protection acts have
sought, with varying degrees of success,
to integrate environmental considerations
into the governmental decision-making
process. The Clean Water Act requires
permits to dredge or fill in wetlands or
waters of the U.S., and to discharge pollu-
tants to surface waters. The Coastal Zone
Management Act encourages integrated state
planning and management in the coastal zone.
State wetland protection acts strictly reg-
ulate modification and filling in some
states.
Two major federal actions within the
last three years have directly affected the
use of coastal areas for municipal solid
waste disposal. Regulations promulgated
under the Resource Conservation and Recov-
224
-------
ery Act of 1976 (P.L. 94-580) have set up
criteria for acceptable solid waste dispos-
al sites. Wetlands are considered to be
among a group of environmentally sensitive
areas whose use is to be avoided. As the
result of a determination that leachate
generation constitutes discharge of a poll-
utant, National Pollutant Discharge Elimin-
ation System (NPDES) permits will be re-
quired, for which there will be a presump-
tion against issuance. Those coastal areas
which are not wetlands are regulated as
floodplains. Disposal sites in such areas
must be protected to the level of the 100
year storm. This provides an economic sanc-
tion against disposal in coastal saline en-
vironments. The other federal restriction
operates in a more indirect manner. Exe-
cutive Order 11990 (May 24, 1977) was is-
sued "to avoid to the extent possible the
long and short term adverse impacts associ-
ated with the destruction or modification
of wetlands and to avoid direct or indirect
support of new construction in wetlands
wherever there is a practicable alterna-
tive." The order requires leadership ac-
tion by federal agencies to avoid destruc-
tion or degradation of wetlands and their
natural values, including avoiding direct
or indirect support of construction on wet-
lands, unless there is no practicable al-
ternative, and provided that all practica-
ble mitigating measures are taken. Recent
EPA implementing regulations require expli-
cit justification of wetland projects, in-
cluding demonstration that no practicable
alternative exists.
As part of a larger study for the So-
lid and Hazardous Waste Research Division
of EPA, Management of Resources and the
Environment (MRE) is undertaking a secon-
dary data search and assessment of the
history and environmental impacts of muni-
cipal solid waste disposal in coastal sa-
line environments. Disposal of sewage
sludge, dredged material, cellar dirt, etc.
are outside the scope of this study, except
to the extent that they may be admixed with
domestic and commercial refuse. (A less
technical, although more appropriate term,
would be common garbage.) Likewise, this
study is not concerned with deep ocean dis-
posal, but rather with material deposited
on or adjacent to the immediate shoreline.
During the late 1960"s and early
1970's, in an attempt to define the nature
of the environmental problems facing us,
many overview pollution studies were de-
signed and executed. Wastler and Wastler
(1972), of the then Federal Water Quality
Administration, identified eight domina-
ting environmental factors of estuarine
zones in the United States. These included:
(1) The width and benthic character
of the Continental Shelf
(2) The nature of associated currents
(3) The coastline structure
(4) The associated river flow
(5) The extent and quality of sedi-
mentation
(6) The associated climate
(7) The associated precipitation
(8) The nature of the tide
By adding two additional general areas
of concern, (9) leachate generation and
movement, and (10) ecological impact, the
study goals were drawn to specifically fo-
cus on solid waste disposal in saline en-
vironments and thus reinforce the need for
a broad interpretation of potential and
real environmental impacts.
STUDY DESIGN
Recognizing that published works nor-
mally provide a good base of data, we per-
formed a preliminary and very limited lit-
erature search in order to test the speci-
fic procedures which could be used, and to
add to our understanding of the study pro-
blem. As a result of that preliminary
search, it was clear that, as initially sus-
pected, relatively few specific articles
are available in the scientific literature.
We concluded that -"fugitive literature,"
such as engineering reports and field in-
spection reports,-would have to be diligent-
ly sought in order to effectively pursue
case studies which should augment the more
accessible literature, which is less spec-
ific.
For example, the Government of the
Virgin Islands considered the creation of a
marine landfill of approximately twenty
acres in Stalley Bay on the south shore of
St. Thomas. Requiring .Army Corps permitting,
with review and comment by EPA, the project
involved diking and the disposal of munici-
225
-------
pal solid waste directly into the impound-
ed marine environment. Predictions of a
flow net analysis of leachate movement
through the permeable dike and under the
dike, and an evaluation of the probable
ecological impact also were prepared. This
type of information, which is current, site
specific, and has meaningful data, would
not normally surface in a standard litera-
ture search. Another complicating factor
is the cross-disciplinary nature of the
information desired. Use of conventional
biological or oceanographic data bases
would probably overlook valuable research.
Compilation of information from coast-
al communities relative to solid waste
quantities and attitudinal responses re-
quires an understanding of past solid waste
management practices. Except for larger
communities, the task of disposing of solid
waste has been relegated to a low position
in municipal operations. As such, record
keeping and data gathering has historically
been very limited. The extraction of this
information from coastal states and towns
would require a creative and vigorous inves-
tigation in order to assure a complete re-
covery of available information.
With these factors in mind, a strategy
was developed to allow for a cost-effective
extraction of relevant information on the
history, environmental impacts, and govern-
mental attitudes toward municipal solid
waste (MSW) disposal in coastal saline en-
vironments. First, the published literature
would be searched via computerized keyword
access to such data bases as BIOSIS, Ocean-
ic Abstracts, etc. Then the cross-discip-
linary and gray or fugitive literature
would be accessed via Environline, Endex,
NTIS, WRSIC and SWIRS. Cross indexing via
the Smithsonian Scientific Information
Exchange and Scientific Citation Index and
monitoring of Current Contents was proposed
as a further check and to help combat the
inevitable lag between publication and
entry into computerized data bases.
In order to extract unpublished infor-
mation and state/municipal attitudes, all
governmental agencies with responsibility
for regulating, planning, or monitoring
coastal waste disposal would be queried
directly through a mailed questionnaire.
COMPUTERIZED SEARCHES
Based on the size of the data bases,
literature covered, degree of overlap (or
non-overlap), timeliness, and cost, the
following data bases were accessed:
Water Resources Scientific Informa-
tion Center (WRSIC)
Solid Waste Information Retrieval
System (SWIRS)
BIOSIS (Biological Abstracts)
Engineering Index (Endex)
Oceanic Abstracts
National Technical Information
Service (NTIS)
Datrix
Pollution Abstracts
Enviroline
EIST
Smithsonian Scientific Information
Exchange (SSIE)
Ph.D. Dissertations
Depending on the data base, the print-
outs included various amounts of informa-
tion. At the least, the complete biblio-
graphic citation, including title, author,
journal volume and page (if applicable),
data, and place of publication were given.
Sponsoring agencies of contract research
are usually specified. In addition, some
entries included pagination, key words,
descriptors, abstracts, or short annotations.
The SSIE data base is slightly differ-
ent from all the others. The Smithsonian
Scientific Information Exchange maintains a
file of over 200,000 ongoing and recently
completed basic and applied research pro-
jects sponsored by over 1300 Federal, state
and local agencies, private foundations, and
universities. The individual records in the
file consist of: project title, supporting
organization name and number, principal in-
vestigator, performing organization, pro-
ject summary, reporting period and (usually)
funding level. The purpose of using this
file was to locate workers with active
226
-------
research interests in the field of waste
disposal in aquatic environments. These
individuals were then contacted by letter
to see if their research, or any of which
they were aware, had yielded results which
would be of use to the study.
Several manual searches of non-compu-
terized data bases were also conducted.
In this way, the files of the then Office
of Solid Waste Management and Planning,
MERL, Yale University Library of Forestry
and Environmental Sciences and MRE's tech-
nical library were also checked.
RESULTS
The literature searches confirmed that
there is a large body of literature on so-
lid waste disposal in the open ocean envi-
ronment, impact of sewage sludge, sewage
effluent and dredged material disposal in
both near shore and open ocean environments,
modification of coastal wetlands, terres-
trial solid waste disposal, and bibliogra-
phies of same. What was lacking, however,
was published information on the environ-
mental impact of disposal of municipal so-
lid waste in saline environments. A deci-
sion was made to recover all citations from
which information could be extrapolated to
the problem at hand.
As a result of the entire literature
search effort, over 3,000 citations were
generated. The breakdown of those deemed
useful and which were acquired is presented
in Table 1.
Table 1: Document Recovery via
Literature Search
Data Base
WRSIC
SWIRS
BIOSIS
End ex
Oceanic Abstracts
NTIS
Pollution Abstracts
Datrix
EIST
Enviroline
OSWMP
SSIE
Other manual searches
Useful Citations
50*
23
9
2
7
23
19
1
1
9
4
43
26
217 TOTAL
*does not reflect search update (1/79)
QUESTIONNAIRE SURVEY
As originally predicted, extraction
of useful specific data on quantities, case
histories, environmental impacts and gov-
ernment attitudes on municipal solid waste
in saline environments required an aggress-
ive data acquisition program aimed at state
and local solid waste management and envi-
ronmental protection agencies. The most
effective methodology for contacting and
eliciting this information was felt to be
through direct mail contact. Accordingly,
a questionnaire was designed which contain-
ed both closed and open-ended items. The
closed items were designed to obtain fac-
tual response on specific issues, such as:
have coastal saline environments been used
as a repository for municipal solid waste
in your state/city?; if so, has monitoring
been conducted?; where are these sites lo-
cated? ; how long was the site used?; what
type of waste was deposited?; what type of
operation was involved?; etc. The open-
ended questions were designed to determine
agency attitudes toward the costs, benefits
and public response to such waste disposal
operations. The entire questionnaire is
presented in the Figure 1.
Although provisions were included in
the questionnaire for forwarding to a more
appropriate agency, past experience had
shown that more useful data would be col-
lected in a shorter time period, if every
attempt was made to determine the agency
with primary responsibility within each
state. Water pollution and solid waste
management statutes were reviewed for each
state in the study. Agencies with apparent
responsibility were cross-checked with a
file of U.S., state and local environmental
officials to develop an accurate, up-to-
date list of names and addresses.
RESPONSE
Initial response to the questionnaire
was fair. One hundred and eighty six
letters were mailed on August 1, 1978. 54
responses were received by 8/31/78, 9 more
by 9/30/78, and a total of 67 by 10/31/78.
Over thirty of these indicated that the
questionnaire had been forwarded to a more
appropriate agency. At this point, a second
mailing was undertaken. In addition to
contacting 123 non-respondents, a question-
naire was sent to thirty agencies not on
the initial mailing list, who were referred
to us by various respondees. By November
227
-------
30, thirty-three more questionnaires were
returned. The final results of the mail
survey, in terms of response, are displayed
in Tables 2 and 3.
DISPOSAL SITES
Responses were received from all
states except Rhode Island. In addition,
Virginia, North Carolina, Florida and Dela-
ware provided no meaningful information.
The information presented below is, there-
fore, based on data supplied by eighteen of
the twenty-three states (including Puerto
Rico) with borders on saline waters. In-
stances of municipal solid waste disposal
were indentified in all of the eighteen
states for which data were available; at
least 147 separate sites were located.
Environmental monitoring data of some sort
are available at 77 sites in 11 states.
These data vary from coliform counts to
bioassays to water and sediment chemistry
analysis. New Jersey, Maryland, Califor-
nia and New York have the most comprehen-
sive data sets. At least one site was in
operation for fifty years (ending in 1967).
At least seventy sites located in coastal
saline environments are still receiving
municipal solid waste. These data are
summarized in Table 4. Closure orders have
been or soon will be issued for five of
these sites. It should be noted that sev-
eral states indicated that more complete
data will be available as they complete
their RCRA inventories.
STATE ATTITUDES AND LEGISLATION
Most states indicated that the RCRA
solid waste criteria which severely re-
strict solid waste disposal in estuarine
and coastal wetlands and floodplains will
have no effect on their solid waste man-
agement programs. This was because pre-
existing legislation prohibited such siting.
Alaska and Louisiana felt that the new
regulation might have a serious impact due
to a high percentage of regulated areas
(the Alaskan response was based on the
large areas of permafrost and/or muskeg
environment and so was not directly res-
ponsive to the question.) Connecticut
discourages new sites, but felt that ver-
tical expansion of existing sites was
preferable to creating new potential sour-
ces of pollution. They felt that discharge
of leachate to a wetland should not be pro-
hibited without site-specific review, due
to the high population density and limited
distribution of RCRA acceptable sites. In
Massachusetts, new coastal MSW disposal
operations are allowed only if no other
option is feasible and if strict pollution
control measures are incorporated into site
design (their regulatory program closely
parallels RCRA regulations). New Jersey
allows permitted landfills in non-wetland
coastal areas. No new sites have been ap-
proved in Oregon for several years, although
there is no absolute prohibition. In Wash-
ington state, Indian nations currently use
coastal disposal sites.
There are also several states which
anticipate some impact as a result of res-
trictions on use of areas subject to inun-
dation by a 100 year storm i.e., a storm
of such intensity that its likelihood of
occurrence is 1% for any particular year.
Texas, Georgia, Connecticut and Alabama
currently permit MSW disposal in floodplains.
In the first three states, the present set-
back is to the level of the 50 year flood
while in Alabama there are no floodplain
restrictions. Connecticut will soon be
switching to the 100 year storm standard.
CONCLUSIONS
Coastal saline environments have his-
torically received large volumes of munici-
pal solid waste. Although such use has
tapered off dramatically in recent years,
there are at least seventy such sites still
in operation, and the actual number is pro-
bably at least twice that. Environmental
monitoring data is available for many sites,
although there has been virtually no stand-
ardization of procedures or parameters in-
volved. Comparison among sites, therefore,
will be difficult.
There have been major state and feder-
al regulatory schemes adopted in recent
years which restrict such waste disposal
practices in the future. There has been,
however, no systematic attempt to document
the environmental impacts of such disposal.
While sewage sludge dumping, sewage efflu-
ent disposal, dredge spoil disposal and
other waste discharges to saline environ-
ments have been carefully categorized as to
their impacts on water quality, sediment
characteristics and benthic and free-living
biota, municipal solid waste disposal has
largely been ignored, except as it affects
water quality.
228
-------
The data that do exist are unpublished
and to a large extent scattered throughout the
the files of various state, regional and
local solid waste and water pollution con-
trol agencies. They concentrate on short
term leachate generation and migration para-
meters, with little or no attempt to deter-
mine if the leachate and/or landfill is
affecting the surrounding ecosystem.
ONGOING RESEARCH
MRE will be conducting one of the most
important aspects of the study this winter,
although the results are not available at
the time this paper is being prepared. As
a result of the responses from the mail sur-
vey, several states were selected for more
intense investigation. Criteria for selec-
tion included: broad biogeographical repre-
sentation, a good-sized data set on sever-
al sites, and the inability of the respon-
sible agencies to extract and supply the
data in a timely manner. In this way, Conn-
ecticut, New York, New Jersey, Maryland,
South Carolina, Louisiana, Washington and
California were selected for visits. To-
gether, these eight states contain 128+
sites, with monitoring available at 56 of
them. This represents 87% and 73% respec-
tively, of the known sites in the two cate-
gories. In addition, the literature search
has been updated to include research con-
ducted and/or entered into searched data
bases in the 20-24 months that elapsed
since the initial search in January, 1977.
229
-------
Table 2. Response to Questionnaire Mailed August 4, 1978
STATE
Alabama
Alaska
California
Connecticut
Delaware
Florida
Georgia
Hawaii
Louisiana
Maine
Maryland
Massachusetts
Mississippi
New Hampshire
New Jersey
New York
North Carolina
Oregon
Puerto Rico
Rhode Island
South Carolina
Texas
Virginia
Washington
Number of
Agencies
Contacted
7
6
19
12
6
11
7
8
5
10
8
5
3
6
7
8
8
9
7
6
7
8
6
9
August 31,
2(1)*
1
10(2)
3(3)
KD
3(3)
KD
1(1)
2***
5(4)
6(2)
1
3(1)
KD
1(1)
5(4)
0
2(1)
2***
0
3(1)
KD
0
0
Response
September 30,
0
0
1
0
2
1 (1)
0
1
0
0
0
0
0
0
1(1)
0
0
0
1
0
1(1)
0
0
1
Through:
November 6,**
0
0
1
0
0
0
0
3
1
0
1
0
1
0
0
0
0
0
0
0
1
1
0
KD
Total
2(1)
1
12(2)
3(3)
3(1)
4(4)
KD
5(1)
3***
5(4)
7(2)
1
4(1)
KD
2(2)
5(4)
0
2(1)
3***
0
5(2)
2(1)
0
7
* numbers in parentheses indicate questionnaires which did not supply meaningful infor-
mation, were forwarded to a more appropriate agency, or had already been answered by
the appropriate agency
** date of mailing of follow-up questionnaire
*** includes one Return-to-Sender
230
-------
Table 3. Response to Questionnaire Follow-up Mailed Nov. 6, 1978
STATE
Alabama
Alaska
California
Connecticut
Delaware
Florida
Georgia
Hawaii
Louisiana
Maine
Maryland
Massachusetts
Mississippi
New Hampshire
New Jersey
New York
North Carolina
Oregon
Puerto Rico
Rhode Island
South Carolina
Texas
Virginia
Washington
Number of
Letters
Sent
6
5
11
12
4
10
7
6
2
8
4
4
1
5
5
6
8
8
4
6
5
4
6
8
November 30
3(2)*
0
4(2)
2(2)
3(3)
3(3)
2(2)
KD
0
3(2)
1(1)
1(1)
2(2)
0
0
0
2(2)
1(1)
0
KD
3(2)
0
0-
1(1)
Response Through:
December 31
KD
0
KD
1(1)
0
2(2)
1
2(1)
0
0
KD
0
0
1(1)
1(1)
4(2)
0
0
3(2)
0
1
0
1(1)
KD
January 31
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
1
0
0
0
0
0
0
0
0
Total
4(3)
0
5(3)
3(3)
3(3)
5(5)
3(2)
3(2)
0
3(2)
2(2)
2(1)
2(2)
KD
KD
5(2)
2(2)
KD
3(2)
KD
4(2)
0
KD
2(2)
* numbers in parentheses indicate questionnaires which did not supply meaningful infor-
mation , were forwarded to a more appropriate agency, or had already been answered by
a more appropriate agency.
231
-------
Table 4: Municipal Solid Waste Disposal Sites in Coastal Saline Environments
STATE
Alabama
Alaska
California
Connecticut
Delaware*
Florida*
Georgia*
Hawaii
Louisiana
Maine
Maryland
Massachusetts
Mississippi
New Hampshire
New Jersey
New York
North Carolina*
Oregon
Puerto Rico
Rhode Island**
South Carolina
Texas
Virginia*
Washington
KNOWN
SITES
1
many
40 +
5 +
0
-
-
1
4
5
12
8
4
0
40±
11
0
1
4
-
2+
3
-
14+
147+
SITES WITH
MONITORING
0
0
7±
4
0
0
0
1
4
7
12
8
0
0
30+
7
0
1
4
-
1+
0
0
1
77+
OPERATING
SITES
0
many
20
3
0
-
-
1
4
3
6
7***
3
0
22+
7+
0
1
0
-
0
0
-
3
70+
*
**
***
limited response
no response
three sites under orders to close
232
-------
Name of Respondent:
Organization:
Address : Telephone:_
A. Have there been past, or are there ongoing instances of municipal solid waste disposal
in coastal saline marsh areas of your state?
yes no
B. Has monitoring or testing of environmental conditions of these operations ever been
conducted?
yes no
(If yes, please complete the following for each site for which monitoring or
testing of environmental conditions has been conducted and for which data exists.
Use additional sheets for multiple areas).
1. Identification of disposal site(s)(name/location)
2. Years of operation 19 through 19
3. Type of waste deposited
4. Type of operation and duration in years
crush & cover burning uncovered operation_
Describe environmental quality testing undertaken. Type of information gathered,
when, agency performing testing.
Would you please forward copies of the program described in #5 above and the
results obtained?
Responsible regulatory agency, group or indivdual having additional information:
(include phone no. & address).
NOTE: The following questions may require the use of additional sheets for answering.
Please staple them to this questionnaire.
C. What will be the effect of federal regulations severely restricting solid waste dispos-
al in estuarine and coastal marshlands and flooplains on your solid waste management pro-
gram? Please circle your response.
a. No. effect. This is already prohibited by state and/or local laws.
b. Some effect, especially in the following situations:
c. Significant effect, especially in the following situations:
D. If your agency has previously considered disposal in the coastal zone a viable alter-
native to deal with the solid waste problem, why has it done so?
E. What problems, both technical and with the public, have you encountered concerning
solid waste disposal sites in estuarine and coastal marshlands?
F. What benefits do you see, both technical and from the public, from restricting solid
waste disposal in estuarine and coastal marshlands?
Figure 1. Simplified Version of Questionnaire
233
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SOIL COVER FOR CONTROLLING LEACHATE FROM SOLID WASTE
Richard J. Lutton
Geotechnical Laboratory
U. S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39180
ABSTRACT
Design of cover for controlling leachate from solid waste should utilize engineering
procedures and concepts. Available soil classified in terms of USC and USDA systems can
be ranked for assisting or impeding water flow, and on this basis soil choices can be
made. Beyond this first step, however, there is a diversity of opportunity for exercising
ingenuity in planning and in designing features to assure that a suitable cover is
constructed.
INTRODUCTION
This paper summarizes some results of
a study on cover for solid and hazardous
waste.^1' The most common cover material
has been soil, particularly indigenous
soil at the disposal site, and such soil
will continue to be preferred for many
years even though synthetic and waste
materials may be used in greater amounts in
the future. Although some aspects of soil
as cover have not been thoroughly inves-
tigated, much is standardized and well
known from previous experience and practice
in soil mechanics, agriculture, and soils
construction.
SOIL CLASSIFICATION
Currently, soils used in solid waste
disposal design and construction are
classified according to either the Unified
Soil Classification System (USCS) or the
U. S. Department of Agriculture (USDA)
System. The USCS is engineering oriented;
soils are grouped according to gradation
of particle sizes, to percentages of
gravel, sand, and fines, and to plasticity
characteristics. The USDA system classi-
fies on the basis of texture only, i.e.,
percentages of gravel, sand, silt, and
clay. Figure 1 presents relationships
between the two systems based on laboratory
tests on hundreds of soil samples.
MOVEMENT OF WATER THROUGH COVER SOIL
Infiltration
The Horton model*'3' provides a simple
conceptual representation of the general
infiltration rate-time relationship (for a
constant source of water at the ground
surface). The maximum infiltration
100.0
A
USDA TYPE
USCS TYPE
SP-SM
PERCENT SAND
Figure 1. USCS superimposed on USDA
soil chart'
234
-------
capacity occurs at the beginning, and the
rate decreases, first rapidly then more
slowly, before reaching a stable minimum
after as little as one hour. This curve
can be conceptually applied to actual
conditions. Thus, rainfall of intensity
below the infiltration capacity curve
(Figure 2) penetrates in its entirety.
TIME
Figure 2, Infiltration capacity curve
separating infiltration from runoff
amounts in a rainfall event.
When the rainfall intensity exceeds the
infiltration capacity, the excess over
capacity accumulates on the surface and
runoff occurs.
The most important factor affecting
infiltration is usually the moisture
content of the soil. The process is
driven^' by combined gravitational and
capillary force acting downward. As the
process continues, capillary pores become
filled; and descending to greater depth,
the gravitationally driven water encounters
increased resistance due to reduction in
large-pore space and sometimes also to a
barrier such as clay. Hence, the initial,
rapid reduction of infiltration rate
(Figure 2) occurs. Low intensity periods
may permit recovery of high infiltration
capacity by providing time for elimination
of surface water accumulations and time
for internal drainage of gravitational
water within the soil.
Percolation
The portion of infiltration which is
important to leachate control is that
continuing at a stable minimum infiltration
rate (Figure 2) after soil pores are
filled. This rate is approximated by the
coefficient of permeability .k. of the
soil. Various investigators^ have shown
that water flows through unsaturated soil
according to a modified form of Darcy's law
in which k is a nonlinear function of
water content.
An important manifestation of the
effect of k and its dependency on water
content occurs in layered systems of
contrasting soil types.(°>T1 Where a
wetting front, descending in a soil of
relatively fine pore sizes, contacts a
predominantly large-pored soil, the pore
volume capable of holding water at the
suction pressures existing at the wetting
front is reduced, as is the water-filled
cross section. Before the wetting front
can advance, the suction pressure at that
point must decrease until it is low enough
to allow the pores to fill with water.
This hang up or delay continues until
the upper layer approaches saturation, at
which time the water is believed to
descend along localized channels'°' rather
than as a planar wetting front. Where the
coarsely pored soil overlies the finer
layer, a similar process reduces the rate
of flow to an evaporation surface above.'^'
RATING AVAILABLE SOILS
From the discussions above, it is
noted that the dominant characteristics of
cover soils affecting water percolation
and in turn leachate generation are
permeability and water-holding capacity.
PERMEABILITY
Soils are rated in Table 1 for
effectiveness in controlling percolation
from I (best) to X (poorest) on the basis
of k . Typical values of k are included
for each soil type for clarification of
235
-------
TABLE 1. SOIL RANKING FOR CONTROLLING PERCOLATION
WATER STORAGE CAPACITY
uses
Soil
GW, GP
GM
GC
SW, SP
SM
SC
ML
CL
MH
CH
Ranking For
Description
Gravel
Silty Gravel
Clayey Gravel
Sand
Silty Sand
Clayey Sand
Silt
Silty Clay
Clayey Silt
Clay
Impeding
X
VII
V
IX
VIII
VI
IV
II
III
I
(k, cm/s)
(5 x 10~2)
(5 x I0'h)
do-11'
do"2)
(10-3)
(2 X 10"1*)
do"5)
(3 x 10"8)
do"7)
do"9)
Assisting
I
IV
VI
II
III
V
VII
IX
VIII
X
the absolute position of the particular
rating. Selection or rating of soil at a
site can be made quickly on this basis;
e.g., an SM soil rates III and therefore is
a reasonably good cover for assisting
(rather than impeding) percolation, as
might be desired in a system where leachate
is recycled through the waste for faster
stabilization.
The importance of water storage in
cover soil lies in the ability to absorb
and at least temporarily hold infiltrated
water that would otherwise percolate
through. To quantify water-holding charac-
teristics , one can formulate in terms of
field capacity and saturated water content.
Figure 3 presents approximate water storage
capacities for the range of USDA soil
types. Bound water, plant-available water,
and gravitational water are distinguished
for given soils according to availability
for use by plants. Only gravitational
water and plant-available water space
contribute to water-holding capacity as
far as the cover soil function of
controlling percolation. For impeding
percolation plant-available water space is
best since it is not susceptible to
drainage (percolation). Gravitational
water space is only beneficial where a low-
permeability layer slows free drainage at
depth. Gravitational water space prevails
in granular materials like sand. At the
other extreme, gravitational water space
is entirely subordinate to plant-available
water space in clay.
SAND
FINE SANDY
SAND LOAM
FINE
SANDY
LOAM
LOAM SILT CLAYHEAV
LOAM LOAM CLAY
LIGHT LOAM
CLAY
LOAM
Figure 3. Water storage capacities for the range of USDA soil types.
236
-------
ANALYSIS OF COVER FOR PERCOLATION
After the characteristics of the
available soil have been evaluated as
discussed above, an analysis can be under-
taken to estimate the amount of percolation
to be expected. This analysis provides a
basis for making some refinements in
design.
WATER BALANCE ANALYSIS
The water balance analysis has been
proposed for solving the problem of
estimating percolation.(°1 Water balance
equations assure continuity as follows:
PERCOLATION = PRECIPITATION - RUNOFF
- EVAPOTRANSPIRATION - CHANGE IN STORAGE
The procedure maintains a running account
or tabulation^' of water introduced to
and removed from the system. Monthly
increments are convenient and have been
used most in the past.
Figure k shows graphically the water
balance for 2 ft of loamy soil cover at
ACTUAL
EVAPOTRANSPIRA TION
JFMAMJJASOND
Figure k. Monthly water balance in
millimeters for 2-ft clay-loam cover at
Cincinnati, Ohio'°).
Cincinnati, Ohio. The monthly rainfall
means are based on a 25-year record. The
basic curve, for infiltration, was obtained
by subtracting a reasonable runoff percent-
age from each mean monthly precipitation
amount. The actual evapotranspiration
curve is obtained by adjusting the
potential evapotranspiration estimates
(derived according to Thornthwaite'^') for
the availability of water in storage; thus
in dry months soil water in storage
decreases and causes actual evapotranspira-
tion to be less than potential levels.
Since water storage is a characteris-
tic of the soil, then some flexibility for
designing exists in the choice of soil and
its thickness according to the water
balance analysis. However, it does appear
from this type of analysis^ ' that thick-
ening the soil cover to increase storage
and thereby reduce percolation is not an
efficient design procedure. The other
important property k enters into the
water balance equation above at only one
place, in the runoff coefficient. Thus,
soils with low k tend to have high runoff
amounts subtracted at the start. However,
permeability should also affect subsequent
steps in water balancing and the fact that
it does not provides a valid criticism of
the technique discussed here.
CRITERION FOR ALLOWABLE PERCOLATION
Perhaps the greatest challenge in
designing a cover for a humid area is in
establishing what are tolerable limits of
percolation. Attempts at solving this
problem have been made previously. ''
Annual percolation has been estimated and
used along with an assumed field capacity
(1-k in./ft) of the waste to estimate the
time to field capacity of the waste cell.
Upon reaching field capacity, the leachate
will be generated at the annual percolation
rate. This predic-feion is valuable in that
it offers a starting point, albeit an
oversimplified one. Experience shows that
a leaking solid waste disposal site becomes
a problem before field capacity. Water
percolating through the cover usually
becomes channelized, especially in hetero-
geneous solid waste such as from municipal
sources.
A more realistic criterion for
allowable percolation may be on the basis
of what is the tolerable leachate rate. If
237
-------
a system is designed capable of collecting
and retaining X in. of leachate, then
that X value will dictate the allowable
percolation rate through the cover.
Accordingly, the designer may be advised to
analyze, besides the average condition, a
daily or even hourly water balance for the
10-year storm, etc. In this way, extreme
throughflows will be incorporated in the
design and will not surprise and overwhelm
a system designed only for average
percolation.
DESIGNING FOR INFILTRATION/PERCOLATION
CONTROL
Several of the parameters influencing
infiltration/percolation can be manipulated
during design and construction. Presently,
the usual intention is to impede the
percolation of water, and the following
guidance is oriented in that direction.
For cases where the cover is intended to
pass water freely, the appropriate proce-
dure should also be apparent in contrast.
SELECTION OR BLENDING OF SOIL
The most direct means of designing a
cover to impede percolation into solid
waste cells is by use of fine-grained soil
with inherently low k (Table l).
Conversely, where a need exists for
relatively free percolation, the choice of
cover soil should be among those with
predominantly coarse grain sizes (and
high k ). Well-graded soils have lower k
values than those with uniform gradation,
i.e., principally of a small range of
grain sizes (provided the median grain size
is the same). Other factors, such as
shrinking and cracking characteristics, and
plant root development may complicate the
choice.
If well-graded fine soil is not
available nearby but coarse- and fine-
grained soils are, consider blending for
an acceptable product and increased source
supply. Blending is effective only for
increasing impedance to water movement
since blending almost always results in a
broadening of the grain-size distribution
as compared with distribution of the
component soils. Blending is usually an
expensive operation, and a thorough review
of other options should be made before
proceeding on a large scale.
COMPACTION
As a general rule, the cover should be
compacted. Compaction is effective in
reducing infiltration and percolation since
k values are sharply reduced. At
municipal waste landfills, an effort of
more than two passes of the spreading or
compacting equipment may be impractical to
monitor and regulate. Higher compactive
effort seems appropriate for intermediate
and final covers except as it will inter-
fere with seeding grass. Care should be
taken to assure that the water content
during compaction does not greatly exceed
the optimum percentage.
LAYERING
Layering (Figure 5) achieves effects
not obtainable with a single material. A
LOAM
II 1 1 1 1 1 1 1 1 '1 (
SILT (FILTER)
-LI 1 1 II 1 1 1 1 L.
SAND (BUFFER)
Figure 5. Design for a 2-ft layered
cover over sand buffer on waste.
two-layer system should be sufficient for
most cover and, in order to impede perco-
lation, might consist of a layer of
compacted clay of very low k value
beneath a layer of silty sand to support
vegetation, provide erosion protection,
and help retain capillary water in the
clay layer. The geometry and layer compo-
sition should be incorporated in the design
on a site-specific basis after other
options have been considered.
MEMBRANES AND BARRIERS
Numerous impermeable membranes and
barriers are available to stop percolation
where such a need has been established.
238
-------
The costs are high, and cover systems
incorporating such features are ordinarily
only specified over hazardous wastes.
AVOID DISCONTINUITIES
An otherwise well-designed cover
system may "be compromised in time if deep
cracks or offsets develop. Such discon-
tinuities commonly form in association
with differential settlement and,
therefore, are aggravated by formation of
depressions detaining some runoff. The
first step to avoiding discontinuities
comes in placement and compaction of the
solid waste that forms the base. Hetero-
geneity should be reduced as much as
possible; bulky objects such as hard
frames or elastic tires should be kept
from the upper part of the waste cell. A
second beneficial procedure is to increase
cover thickness sufficiently that antici-
pated differential settlement will not
expose the waste cell to direct perco-
lation. Ponding in associated depressions
can be avoided by providing sufficient
slope.
SURFACE SLOPE
Rainfall runoff increases with
increasing slope of the surface; hence
infiltration decreases. Since erosion also
increases with increasing slope, the design
of slope should balance the opposing con-
siderations (where percolation is
undesirable). On slopes of less than
3 percent, the irregularities of the
surface and vegetation commonly trap and
detain runoff. The value 5 percent has
been suggested>and used in grounds
maintenance as a first approximation of
slope sufficient to promote runoff without
risking excessive erosion.
WINTER GRASS
In mild climates, as in the south-
eastern United States, consideration should
be given to growing both summer and winter
grass to protect the cover from erosion and
to extend the range of evapotranspiration
to a year-round basis.
DRAINAGE
The first rule of surface drainage
design for solid waste sites is to inter-
cept and direct all water from outside
the immediate area. Interception is
accomplished by constructing a ditch or
system of ditches on the uphill sides.
Simply design the ditch to accommodate
anticipated discharge, e.g., 10-year
storm, according to an appropriate hydrau-
lic formula.
On the cover itself discharge volumes
are small, and the main concern is removing
water quickly with minimal damage by
erosion. A ditch slope of 2 percent is
recommended. ' Ditches should be
grassed, and for proper mowing maintenance
side slopes should not exceed 1 vertical
on 3 horizontal or in cases of V-shaped
channels, 1 on 6. Actually, flat-bottomed
channels are preferred to V-shaped
channels from the point of view of erosion.
Removal of cover soil water through
buried drains offers promise for effective
reduction of percolation into waste cells
since such drains have been proven viable
in engineering and agriculture. Drains
require little maintenance and leave the
surface in a natural and esthetically
pleasing condition. A herringbone pattern
of drains can be adapted easily to minor
topographic irregularities as they are
developed in landfilling.
FUTURE DIRECTION OF STUDY
A top priority need for refinement
exists in the analysis of percolation
amounts to be expected through soil cover.
Once these amounts can be predicted
accurately, there will be a basis and an
impetus for adjusting soil composition or
for refining designs accordingly. The
study is currently proceeding toward that
goal.
REFERENCES
Lutton, R. J. et al., "Selection and
Design of Cover for Solid Waste,"
U. S. Environmental Protection Agency,
Report (in preparation), 1979.
Meyer, M. P. and Knight, S. J.,
"Trafficability of Soils, Soil Classi-
fication," U. S. Army Engineer Water-
ways Experiment Station, Technical
Memorandum 3-2HO, Supplement 16, 1961.
239
-------
Viessman, W., Jr., Harbaugh, T. E.,
and Knapp, J. W., Introduction to
Hydrology, Intext Educational, New
York, 1972, Ul5 pp.
Gray, D. M. and Norum, D. I., "The
Effect of Soil Moisture on Infil
tration as Related to Runoff and
Recharge," Soil Moisture, Proceedings
of Hydrology Symposium, No. 6,
National Research Council of Canada,
1968, pp 133-150.
Philip, J. R., "Theory of Infiltra
tion," Advances in Hydroscience,
Vol 5, V. T. Chow, ed. , Academic
Press, New York, 1969, pp 215-296.
Miller, D. E. and Gardner, W. H.,
"Water Infiltration Into Stratified
Soil," Soil Science Society of
America Proceedings, Vol 26, 1962,
pp 115-119.
Hillel, D., "Computer Simulation of
Soil-Water Dynamics: A Compendium
of Recent Work," International
Development Research Centre, Monograph
IDRC-082e, Ottawa, 1977, 21k pp.
8. Fenn, D. G., Hanley, K. J., and
DeGeare, T. V., "Use of the Water
Balance Method for Predicting
Leachate Generation from Solid Waste
Disposal Sites," U. S. Environmental
Protection Agency, Report SW-168,
Cincinnati, OH, 1975.
9. Thornthwaite, C. W. and Mather, J. R.,
"The Water Balance," Publications in
Climatology, Vol VIII, No. 1, Drexel
Institute, New Jersey, 1955, 86 pp.
10. Daas, P. et al., "Leachate Production
at Sanitary Landfill Sites," Journal
of the Environmental Engineering
Division, American Society of Civil
Engineers, Vol 103, 1977, pp 981-988.
11. Conover, H. S., Grounds Maintenance
Handbook, 3d ed., McGraw-Hill,
New York, 1977, 631 pp.
240
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LINER MATERIALS EXPOSED TO MSW LANDFILL LEACHATE
H. E. Haxo, Jr.
Matrecon, Inc.
Oakland, California
ABSTRACT
This paper presents the results of immersing specimens of 28 different polymeric mem-
brane liner materials in sanitary landfill leachate for 8 and 19 months. These 28 liners
include variations in polymer, compound, thickness, fabric reinforcement, and manufacturer.
The polymeric materials include butyl rubber, chlorinated polyethylene, chlorosulfonated
polyethylene, elasticized polyolefin, ethylene propylene rubber, neoprene, polybutylene,
polyester elastomer, low-density polyethylene, plasticized polyvinyl chloride, and poly-
vinyl chloride plus pitch.
The effects of the immersion were assessed by measuring the amount of swelling and
the changes in such physical properties as tensile strength, elongation, modulus, hardness,
and puncture resistance.
The results of the immersion tests generally confirm results previously obtained on
membrane liner materials exposed for one year in simulated landfills. Specimens of chlori-
nated polyethylene, chlorosulfonated polyethylene, ethylene propylene rubber, and neoprene
liners showed the greatest swell and loss of properties, although specimens of some of the
ethylene propylene rubber and neoprene liners showed little swelling and loss of properties.
Generally the change in properties of a given material appears to relate to the amount
that it swelled.
Also reported are the results of the water vapor permeability testing of 27 membrane
liners, the water absorption of a series of polymeric membranes at room temperature and at
70°C, and the retrieval and testing of samples of a six-year old membrane liner from a dem-
onstration landfill.
A promising simple test for assessing permeability and physical properties of membrane
liners for landfills is described. Test results are presented.
INTRODUCTION
This project was undertaken in 1973
with the primary purpose of assessing the
effects upon a variety of liner materials
of exposure to leachate from municipal solid
wastes. At the time the project was initi-
ated, the lining of landfills with various
impermeable materials appeared to be a feas-
ible means of preventing the migration of
the leachate into the surface and ground-
waters, resulting- in their pollution. There
was, however, little information available
as to durability of the various available
liner materials in such an environment.
There were considerable data as to the
service lives of lining materials for con-
taining water, but there was concern as to
the long-term effectiveness of various liner
materials in contact with leachate.
The primary effort of this project has
been the exposure of selected lining ma-
terials in conditions which simulate actual
use in sanitary landfills. Results of one
year of exposure of these materials has been
reported (1-5). The effects of one year of
exposure were comparatively mild and
241
-------
inadequate with which to form a basis for
making long-range projections of service
lives. Consequently, the exposure periods
were extended and the scope of the project
was expanded to include studies on addition-
al materials and an investigation of simpler
methods of assessing the effectiveness and
durability of the various liner materials.
This paper concentrates on the invest-
igations of polymeric membrane liner ma-
terials and particularly on the effects of
the total immersion of these materials for
8 and 19 months in leachate produced in the
same simulated landfills used in this proj-
ect. Other areas discussed in this paper
are water absorption, permeability studies,
and a description of a laboratory test for
assessing the permeability and durability
of membrane liners. The results of the re-
covery of a membrane liner from a demonstra-
tion landfill are also presented.
EXPERIMENTAL DETAILS
The conditions at the bottom of a land-
fill that must be simulated for the genera-
tion of leachate and for the exposure test-
ing of liner materials are illustrated in
Figure 1.
This schematic drawing of a liner in-
cludes the following features:
- Municipal solid waste.
- A porous soil cover on the liner on
which waste can be dumped without
damaging the liner and through which
leachate generated in the fill can
drain.
- The liner which may be from 30 mils
to 3 ft in thickness, depending on
the liner material used.
- Compacted soil on which the liner has
been placed. The soil has been
graded to give drainage to the leach-
ate.
- Uncompacted native soil.
- Groundwater level, usually well below
the landfill.
The design of the simulated landfill
and leachate generator is illustrated in
Figures 2 and 3.
Approximately 930 pounds of shredded
municipal refuse was placed in each of the
generators. The composition of the refuse
is shown in Table 1; the amount of identi-
fiable food waste was low.
TABLE 1. COMPOSITION OF REFUSE
Material
Percent
Water 12.2
Paper 53.6
Cloth 0.8
Plastics and rubber 4.9
Wood, garden, and food waste 5.1
Oils and fats 0.9
Metal 7.6
Glass, rock, and soil 14.9
Total 100.0
The leachate used throughout these
studies was produced in the simulated san-
itary landfills in which the primary liner
specimens were also exposed. The average
composition of the leachate at the end of
the first year, when the first set of gen-
erators was disassembled and the liner spec-
imers were retrieved and tested, is shown in
Table 2.
TABLE 2. ANALYSIS OF LEACHATE3
Test
Value
Total solids, % 3.31
Volatile solids 1.95
Nonvolatile solids 1.36
Chemical oxygen demand (COD), g/1 45.9
PH 5.05
Total volatile acids (TVA), g/1 24.33
Organic acids, g/1
Acetic 11.25
Propionic 2.87
Isobutyric 0.81
Butyric 6.93
At the end of the first year of operation
when the first set of liner specimens were
recovered and tested.
242
-------
I\3
-P.
CO
POROUS LAYER FOR DRAINAGE
PONDING OF LEACHATE
LINER 10.030-36IN)
COMPACTED-GRADED SOIL
GROUNDWATER LEVEL
Figure 1. Schematic drawing of the circum-
stances of the liner at the bot-
tom of a solid waste landfill.
-------
SHREDDED REPUTE
COMPACTED TO S FT.
THICKNESS
CONCRETE B»SE
LEACHATE DRAIN PROM REFUSE
TO COLLECTION BAG
DRAIN ROCK V THICK
SOIL COVER
. THICK
POLYETHYLENE LINER
REFUSE COLUMN-
SPIRAL-WELD PIPE,
" DIA. X 10 FT. HIQW
MASTIC. SEAL
5AND
LINEK SPECIMEN
CAST EPOXY RESIN RING
QRAVEL
LEACHATE. DRAIN THKU LINER
TO COLLECTION BA
-------
. SAND
EPOXY.SEAL •-'.• '.
'" ' MEMBRANE LINER
Figure 3. Detail of the base of the leachate generator showing the refuse, the sand cover, and the liner.
One foot of leachate is allowed to pond on the liner. The additional leachate is continuously
collected. Leachate that seeps through or by-passes the liner because of a failure of the seal
is also continuously collected.
-------
The strength of the leachate dropped
as is shown in Figures 4 and 5. The compo-
sitions of the leachates from the 12 gener-
ators, which have remained in operation
since the first group of liners were recov-
ered and tested in November 1974, were ini-
tially quite uniform. However, in recent
months the average strength of the leach-
ates has dropped significantly and differ-
ences in compositions have developed. Nu-
trient (urea) is being added with the water
to several generators to increase the
strength, particularly of the volatile acids.
IMMERSION STUDY
The comparable results of the first
year of exposure tests of the buried strips
of the membrane materials with those of the
primary liners indicated the complete immer-
sion of a specimen in leachate would be a
feasible method of exposing liners for test
purposes (Table 3). For the generator ex-
posures, the strips were placed in a curled
position in the leachate-saturated sand di-
rectly above the primary liner specimens.
In this position both sides of a strip spec-
imen are exposed to leachate where only one
side of a primary liner is exposed.
The availability of leachate from the
simulated landfills made it possible to use
the same fluid for immersing test specimens
as is in the generators, thus allowing di-
rect correlation between the immersion test
and exposure at the bottom of the simulated
landfills.
An immersion study was undertaken to
evaluate membrane liner materials only, as
admix materials do not lend themselves to
tests of this type. The basic design of the
immersion system consists of a series of six
polyethylene tanks through which the leach-
ate is allowed to flow at the rate of 14 ml
per minute. The system is essentially air-
tight and the leachate is circulated once
every 12 days. Each tank holds 14 specimens,
8 in. by 10 in. (Figure 6). Three sets of
28 specimens of each membrane were immersed
in the leachate so that they could be re-
moved in sets from the system after three
exposure intervals. The 28 membranes of 11
different polymeric materials that were se-
lected for testing consist of the following:
Type of material
Number of
different
liners immersed
Butyl rubber 1
Chlorinated polyethylene 3
Chlorosulfonated polyethylene 3
Elasticized polyolefin 1
Ethylene propylene rubber 5
Neoprene 4
Polybutylene 1
Polyester elastomer 1
Polyethylene 1
Polyvinyl chloride 7
Polyvinyl chloride + pitch 1^
Total 28
The tests performed on the lining ma-
terials before exposure and at three subse-
quent intervals are:
- Weight.
- Dimensions.
- Tensile strength, in machine and
transverse directions, ASTM D412.
- Hardness, ASTM D2240.
- Tear strength in machine and trans-
verse directions, ASTM D624, Die C.
- Puncture resistance, FTM 101B, Method
2065.
- Volatiles at 105°C, ASTM D297.
- Specific gravity, ASTM D297.
The output of the 12 generators is
blended and is added to the immersion sys-
tem every four weeks, replacing part of the
leachate in the system. During the first
months of operation, the composition of the
leachate before and after exposure was com-
parable to the average obtained by the math-
ematical averages of the compositions of the
individual cells. Recently, the leachate
appears to have changed considerably during
the time it is in the immersion system, in-
dicating a possible biological contamination
of the immersion system.
After 8 and 19 months of immersion, the
liner specimens were retrieved and tested.
Selected results are presented in Tables 3
and 4 and Figures 7 and 8.
246
-------
4.0-
I I I
TOTAL SOLIDS
3.0
.J
t-
z:
LJ
I-
O
o
CO
O
O
CO
2.0-
1.0--1
NON-VOLATILE SOLIDS
24 GENERATORS
i I
1974!
1975
1976
ELAPSED TIME
1977
1978
Figure 4. Average solids contents of the leachate produced in the generators, November 1974 - May 1978.
The data for November 1974 - November 1975 are the averages for the leachate from 24 generators.
Twelve generators were disassembled in November 1975 and, consequently, the data for December
1975 - May 1978 are the averages for the leachates from the 12 remaining generators.
-------
no
J^
CO
|1974|
Figure 5.
1975
1976 I
ELAPSED TIME
1977
1978
Average total volatile acids content (TVA), as acetic acid, of the leachate produced in the gen-
erators, November 1974 - May 1978. The data for November 1974 - November 1975 are the averages
for the leachates from 24 generators. The data for December 1975 - May 1978 are the average,-,
for the leachates from 12 generators.
-------
TABLE 3. SWELLING OF POLYMERIC MEMBRANE LINERS BY LANDFILL LEACHATE -
LEACHATE CONTENT OF EXPOSED MEMBRANE LINER MATERIALS IN PERCENT
ro
-p>
Polymer
Butyl rubber
Chlorinated polyethylene
Chlorosulfonated polyethylene
Ethylene propylene rubber
Neoprene
Polybutylene
Polyethylene
Polyvinyl chloride
Liner
no.
7
44
12
3
6
8
16
9
20
21
11
17
19
Exposed in simulated
landfill for 12 monthsa
Primary Buried
specimens specimens
2.0 1.8
-
6.8 9.0
20.0
12.8 13.6
5.5
5.5 6.0
8.7
0.3
0.02 0.3
5.0
3.6 3.3
0.8
Immersion in leachate for 8 and 19 months
"volatiles'ia
8 mo.
_
1.4
7.9
18.6
12.1
2.9
-
9.0
-0.2
0
2.4'
2.3
0.9
19 mo.
_
2.6
14.4
22.8
14.9
3.8
-
14.8
0.7
0.2
4.4
4.4
1.9
From swelling test0
8 mo.
_
1.8
8.7
16.1
12.0
5.7
-
16.2
0.1
0.6
2.8
3.2
1.6
19 mo.
_
3.4
15.0
21.0
13.9
7.0
-
24.1
0.8
0.7
6.0
3.2
1.8
a ' ' o
Percent leachate in swollen liner as determined by "volatiles content" at room temperature and at 105 C.
Calculated from the increase in weight of the immersed specimens.
-------
COVER DETAIL
CROSS SECTION
SPECIMENS ATTACH
TO HOOKS
LEACHATE IN
LEACHATE OUT
LEACHATE IN
LEACHATE OUT
14 SPECIMENS
NOTE:
PLASTIC WELD SEALS
COVER TO CONTAINER
POLYETHYLENE TANK
Figure 6. Individual polyethylene immersion tank, showing method of
holding specimens and the inlet and outlet for the leachate.
250
-------
TABLE 4. RETENTION OF MODULUS3 OF POLYMERIC MEMBRANE LINER MATERIALS
ON IMMERSION IN LANDFILL LEACHATE
Polymer
Butyl rubber
Chlorinated polyethylene
Chlorosulfonated polyethylene
Elasticized polyolefin
Ethylene propylene rubber
Neoprene
Polybutylene
Polyester elastomer
Polyethylene
Polyvinyl chloride
Polyvinyl chloride + pitch0
Liner
no.
44
12
38
86
3
6b
85
36
8
18
83b
91
41
9
37
42b
90
98
75
21
11
17
19
40
67
88
89
52
S-200, psi !
Unexposed
685
1330
1205
810
735
1550
1770
970
690
760
845
855
1040
1235
1635
-
1190
3120
2735
1260
2120
1965
1740
1720
1700
2400
2455
1020
8 mo.
590
1130
1070
790
395
1775
1360
1005
870
840
905
775
1035
975
1630
-
1245
3160
2790
1340
1845
1570
1545
1560
1570
1900
2370
870
19 mo.
620
1190
1090
860
335
2070
1920
1050
860
830
900
790
1030
950
1640
-
1350
3150
2670
1285
1805
1640
1645
1570
1780
2105
2330
880
Retention
% of original value
8 mo.
86
85
89
98
54
114
77
104
126
110
107
91
100
79
100
-
105
101
102
106
87
80
89
91
92
79
96
85
19 mo.
90
89
90
106
46
134
108
109
124
109
107
92
99
77
100
-
114
101
98
102
85
84
94
91
105
88
95
86
aAverage of stress at 200% elongation (S-200) measured in machine and transverse
directions.
^Fabric reinforced.
CS-100 values given; original and subsequent exposed specimens failed at less than
200% elongation.
251
-------
CHLOMNATfD
"dfc"
PQLWINVL CHLORID
POLVVHIVL CHLORIC*
B MONTHS IMMERSION
UNCR HO
ABSORPTION OF LEACHATE *
Figure 7. Swelling of membrane liners during immersion in leachate for
8 and 19 months.
252
-------
BUTYL flUMEH
FOLYEITEH ELASTOMER
TENSILE STRENGTH. % ORIGINAL
Figure 8. Retention of tensile strength of polymeric membrane liners on
immersion in landfill leachate after 8 and 19 months. Ten-
strength data were obtained by averaging the machine and trans-
verse tests. The number of different liners of a given poly-
mer that are included in the test is shown in parentheses.
253
-------
The swelling that occurred during the
immersion is compared in Table 3 with the
swelling of samples of similar materials in
the simulated landfills for 12 months. The
buried and primary specimens generally
swelled equally in the 12 months that they
were exposed in the simulated landfills. In
many cases, the 8 months of immersion were
equal to the 12 months of exposure in the
simulated landfills. On the basis of these
data, it appears that the immersion in the
leachate is quite comparable to the exposure
in the simulated sanitary landfills.
In Figure 7 the data on swelling of the
liners during the immersion in leachate is
arranged by polymer type. The range of val-
ues for a given polymer is indicated by the
bars for 8 and 19 months. The data show
that, not only does the swelling vary from
polymer-to-polymer, but also within a poly-
mer type, because of compound differences.
Chlorinated polyethylene, chlorosulfonated
polyethylene, and neoprene showed the great-
est variations within a polymer type. On
the other hand, the seven polyvinyl chloride
liner specimens varied only a few percent.
In almost all cases the swelling values for
the 19 months of immersion were higher than
the eight-month values.
The effect on the tensile strength and
modulus (stress at 200% elongation) of the
same materials is shown in Figure 8 and in
Table 4, respectively. The effects appear
to be related to degree of swell which the
specimens have undergone. Those specimens
which swell little vary little in tensile
strength and modulus. Again, the polyvinyl
chloride membranes have a low spread in val-
ues and retained their original tensile and
modulus. Overall, the polyolefins, such as
polyethylene, polybutylene, and elasticized
polyolefin, exhibit the low swelling and
highest retention values.
The effect of immersion in leachate up
to 19 months appears to have a relatively
mild effect upon most of the membranes as
shown for tensile strength and retention vs.
immersion time in Figure 9.
The changes in properties, e.g. tensile
strength, appear to be generally related to
the amount of swell which the membranes have
undergone during the immersion. This is il-
lustrated in Figure 10, in which retentions
of tensile strength have been plotted
against the leachate absorption for the lin-
er materials.
WATER ABSORPTION STUDY
The swelling of rubber or plastic com-
positions generally results in a reduction
of mechanical properties and an increase in
permeability. Severe swelling could ulti-
mately cause the failure and nonperformance
of polymeric membrane materials. During the
first year of exposure in the simulated land-
fills, some of the specimens showed signifi-
cant absorption of leachate and reduction in
properties (2). Immersion of specimens in
water resulted in comparable absorption, al-
though the magnitude and the order of in-
creasing swell were not the same as in leach-
ate (Table 5).
The water absorption studies were ex-
tended using ASTM Test Method D570 (6). Ab-
sorption tests were run at room temperature
and at 70°C. The objectives of these studies
were to determine the correlation of swell-
ing by leachate with that by water, which is
the major constituent of the leachate. Also,
water is a standard reference fluid for
swelling tests. In addition, it was desired
to determine whether the swelling of the lin-
er materials would plateau, that is, come to
equilibrium on extended immersion times. Re-
sults of water absorption of 11 membrane
liners on immersion in water up to 100 weeks,
both at room temperature and at 70 C, are
presented in Table 6. The relative results
for the two temperatures were generally the
same; however, one of the major differences
was with one of the polyvinyl chloride lin-
ers (#11), which yielded the lowest swell at
room temperature, but was sixth at 70°C. The
liner materials that had the lowest swell
were the polyvinyl chloride, the elasticized
polyolefin, and the ethylene propylene rub-
ber; those that swelled the most were neo-
prene, chlorosulfonated polyethylene, and
chlorinated polyethylene. The chlorinated
polyethylene and the ethylene propylene rub-
ber essentially reached equilibrium swell at
70°C in the 100 weeks. A polyvinyl chloride
liner appeared to have reached equilibrium
swell; however, it hardened because of loss
of plasticizer. It appears that several of
the other liner materials, particularly the
neoprene and chlorosulfonated polyethylene,
will continue to swell for considerable
lengths of time.
254
-------
DAYS EXPOSED
DAYS EXPOSED
Figure 9. Retention of tensile strength of the individual polymeric mem-
branes as a function of immersion time in landfill leachate.
Tensile strength values based upon the average data obtained
in the machine and transverse direction are used. Liner num-
bers as well as the initial tensile strength for each liner
are shown. Data given for 8 months (240 days) and 19 months
(570 days).
255
-------
• 19 MONTHS IMMERSION
LEACHATE ABSORPTION %
Figure 10. Retention of average tensile strength of membrane liner ma-
terials during immersion in landfill leachate as a function
of swelling by the leachate.
256
-------
TABLE 5. COMPARISON OF THE SWELLING OF MEMBRANE LINER MATERIALS
IMMERSED IN WATER AND IN LEACHATE
Swelling, %
Liner In water In leachate
Polymer no. for 44 weeks for 32 weeks
Chlorosulfonated polyethylene 6 10.9 13.3
Elasticized polyolefin 36 0 0.1
Ethylene propylene rubber 8 1.6 6.0
Polyester elastomer 75 0.67 2.0
Polyvinyl chloride 11 0.70 2.9
257
-------
TABLE 6. WATER ABSORPTION OF SELECTED MEMBRANE LINER MATERIALS AT ROOM TEMPERATURE AND AT 70 Ca
ro
tn
Water absorbed, % by weight
At room temperature
Polymer
Butyl rubber
Chlorinated polyethylene
Chlorosulfonated poly-
ethylene
Elasticized polyolefin
Ethylene propylene rubber
Neoprene
Polyester elastomer
Polyvinyl chloride
Liner
No.
57
77
6
36
8
26
43
82
75
11
59
1
week
0.
1.
3.
0.
0.
1.
3.
2.
1.
1.
1.
82
63
44
39
50
20
80
43
07
29
59
11
weeks
3.22
5.53
6.97
0.52
1.30
1.84
13.62
8.29
1.05
1.10
2.34
44
weeks
4.50
10.2
10.9
0.0
1.56
1.49
37.8
18.5
0.67
0.70
2.43
100
weeks
6.4
12.5
16.3
4.5
2.25
2.56
75.1
32.1
1.31
1.25
2.98
1
day
2.04
3.04
5.68
0.24
0.42
0.74
3.89
2.49
1.18
1.51
2.09
1
week
4.62
15.9
22.1
0.36
1.11
1.44
14.1
8.11
1.28
5.59
4.87
At 70 C
11
weeks
17.54
58.4
131.0
0.45
3.55
4.52
107.0
47.4
1.10
12.13
8.25
44
weeks
53.9
140.0
245.6
0.57
10.8
11.20
240.0
191.4
0.72
39.2
24.0
100
weeks
103.2
179.3
370.5
8.7
17.8
17.4
(b)
295.0
0.22
87.4
25. 5C
aASTM D570-63 specimens 1x2 in. in deionized water.
Specimens began to disintegrate between 44th and 69th weeks.
"Specimens have become hard, indicating loss of plasticizer.
-------
These tests are being continued for the
duration of the project. Also, physical
testing of exposed samples will be made to
determine the effect on physical properties
from the swelling in water.
A comparison is made of the swelling in
water and leachate in Table 5 for five lin-
ers. The swelling in leachate for 32 weeks
was greater in all cases than swelling in
water for 44 weeks, indicating the possible
effect of the organic acid content of the
leachate.
PERMEABILITY OF MEMBRANE LINERS TO
WATER VAPOR
As the basic function of a liner is to
control the flow of leachate and prevent its
entrance into the surface and groundwater,
permeability to water and dissolved ingred-
ients is its most important property. The
great range in the permeability of materials
which are potentially useful as liners for
landfills makes it difficult to use a single
laboratory test to assess this property.
The polymeric membrane lining materials are
essentially nonporous and, consequently, the
mechanism for the transport of fluids
through the membranes is determined by the
solubility and the rates of diffusion on a
molecular scale. This is also true of as-
phaltic membrane liners. On the other hand,
the transport of fluids through admix ma-
terials and soils is determined by a viscous
flow mechanism. The driving force which
moves fluids through membranes is largely
determined by concentration differences,
whereas the transport through the admixes is
determined by hydrostatic pressure. The use
of permeameters similar to those used for
admixes requires extremely long tests.
The polymeric membrane liner industry
has been using vapor transmission, following
ASTM E-96, Method BW (7), as a measure of
the permeability of the membrane liners. In
this test, a small water cup with a membrane
specimen cover is placed in an inverted po-
sition in an environment having controlled
temperature, humidity, and airstream (Figure
11). The loss in weight of the cup is fol-
lowed as a function of time and the permea-
bility calculated from the slope. This test
is intended for those applications in which
one side is wetted under conditions where
the hydraulic head is relatively unimportant
and moisture transfer is governed by capil-
lary and water diffusion forces. In this
test the driving force is supplied by the
difference in the vapor pressure from the
two sides of the membrane.
Water vapor permeability of 27 polymer-
ic membrane liners is reported in Table 7.
The polyester liner, which was the thinnest
membrane in the series, with a thickness of
eight mils, had the highest rate of water
vapor transmission. However, its water va-
por permeability, which corrects for thick-
ness and is a property of the liner polymer,
is in the same range as that of polyvinyl
chloride compositions, some of which are con-
siderably more permeable. There is a three-
fold variation from the lowest permeability
to the highest in the case of polyvinyl
chloride liners. As a group, the polyvinyl
chloride liners are the most permeable; the
most impermeable materials in this test ser-
ies are elasticized polyolefin and butyl rub-
ber, both of which have less than one tenth
of the water vapor permeability of polyvinyl
chloride. There is a considerable spread in
the values for butyl rubber, indicating com-
pound differences. The other liner materials
are intermediate in water vapor permeability,
with a possible twofold variation among them.
Increased test times, during which the
membranes are swelled somewhat by the water,
yield slightly higher permeabilities, indi-
cating that their permeabilities will be
greater on long-term exposure. Additional
tests of swollen liner specimens are pro-
jected.
BAG TEST FOR ASSESSING MEMBRANE
LINER MATERIALS
The water vapor method described above
for assessing the permeability of membrane
liner materials yields results that are prob-
ably satisfactory for comparing the relative
merits of the various liners to water. How-
ever, leachate contains dissolved constitu-
ents, many of which would not pass through
the liner. Also, the test conditions in the
vapor transmission method are not comparable
to the conditions that a liner would encoun-
ter at the base of a landfill. The driving
force, in the case of the vapor test, is a
difference in humidity on both sides of the
membrane. Such a condition would not exist
at the base of a fill. The driving forces
259
-------
ro
cr>
o
CUP IN INVERTED
POSITION
TEST SPECIMEN
SEALED IN CUP
WAX FOR SEALING
LINER IN CUP
HOT PLATE FOR
HEATING WAX
MOLD FOR MAKING
RING SEAL
TEST SPECIMEN
Figure 11. E96 water vapor permeability cup and auxiliary equipment.
-------
TABLE 7. WATER VAPOR PERMEABILITY OF POLYMERIC MEMBRANE LINERS, ASTM E-96, METHOD BW
Polymer
Butyl rubber
Chlorinated poly-
ethylene
Chlorosulfonated
polyethylene
Elasticized
polyolefin
Ethylene-propylene
rubber
Neoprene
Polyester elastomer
Polyvinyl chloride
Liner
No.
22
57
12
38
77
86
3
6b
55
36
8
18
26
41
83
9
42
43
82
75
11
17
19
40
59
88
89
Thickness
mils
73.?
33.5
33.3
32.3
31.0
21.0
31.0
37.0
35.0
28.3
67.0
48.5
38.0
20.0
37.0
61.0
20.0
31.5
61.2
8.0
30.0
20.0
21.0
32.5
33.0
20.5
11.0
cm
0.185
0.085
0.085
0.082
0.079
0.053
0.079
0.094
0.089
0.072
0.170
0.123
0.097
0.051
0.094
0.159
0.051
0.080
0.155
0.020
0.076
0.051
0.054
0.083
0.084
0.052
0.028
Test
time,
days
49
21
28
21
21
28
32
40
42
28
28
28
28
21
28
21
42
28
63
21
28
35
42
42
21
35
35
Rate of
water vapor
tr ansmis s ion ,
g/d • m2
0.097
0.020
0.264
0.361
0.320
0.643
0.634
0.422
0.438
0.142
0.172
0.314
0.327
0.270
0.190
0.237
0.304
0.448
0.240
10.50
1.85
2.97
2.78
4.17
4.20
2.94
4.42
Water vapor Water vapor
permeance, permeability,
10" 2 g/d-m2.mmHg 10" •* g/d • nr • mmHg • cm
(metric perm) (metric perm-cm)
0.75
0.17
2.10
2.90
2.80
5.10
5.00
4.21
3.47
1.20
1.40
2.49
2.80
2.15
1.50
1.90
24.1
3.90
2.00
91.0
16.0
24.0
22.0
33.0
36.0
23.0
35.0
1.39
0.15
1.76
2.35
2.10
2.72
3.97
3.79
3.09
0.85
2.52
3.07
2.72
1.09
1.42
2.89
1.22
3.12
3.11
18.2
•12.2
12.0
11.8
27.3
30.2
12.1
9.77
Average temperature, 72°F; average relative humidity, 42%.
Fabric-reinforced.
-------
that exist are either hydrostatic pressure
of a leachate on the liner or the dif-
ference in concentration of the leachate
and the groundwater below. In the latter
driving force, the osmotic pressure will
force the fluid to go from a low concentra-
tion of dissolved constituents into a high
concentration. A test has been devised in
which the osmotic pressure will be the driv-
ing force for the movement of water and dis-
solved constituents across a membrane. This
test involves the fabrication of small bags
which can be filled with leachate or other
test fluid and sealed and placed in deion-
3-zed water (Figure 12) . The flow of ma-
terials through the membrane can be measured
by determining the weight increase of the
bag and measuring the pH and electrical con-
ductivity of the deionized water.
Initial experiments have been carried
out with a 5% solution of sodium chloride
and leachate. The composition of the leach-
ate is given in Table 8. The test results
are presented in Tables 9 and 10 for these
fluids, respectively.
Results with 5% NaCl solution in the
bags of the various liner materials are pre-
sented in Table 8. The elasticized polyole-
fin and a polyvinyl chloride liner (#11) are
the most impermeable to both water and the
ions. The chlorosulfonated polyethylene was
most permeable to the ions and the polyester
elastomer was most permeable to water. The
latter, however, was the thinnest (8 mils)
compared with the others (>20 mils).
In the case of the bags containing leach-
ate, it is again apparent that there was
movement through the liner by both the water
and the dissolved ingredients of the leach-
ate (Table 10). An increase in electrical
conductivity occurred, indicating the perme-
ation of some ions from the leachate into the
deionized water. Also, there was an increase
in the weight of the bags containing the
leachate, indicating permeation of water into
the bags containing leachate. In this series,
the elasticized polyolefin again yielded the
lowest transmission of water and of dissolved
components and the chlorinated polyethylene
appears to be the most permeable. Also, one
of the polyvinyl chloride liners (#17) ap-
pears to be quite permeable to ions.
TABLE 8. CHARACTERISTICS OF LEACHATE
IN BAGSa
Property
Total solids, %
Total volatile solids, %
Chemical oxygen demand, g/1
Total volatile acids, g/1
pH
Conductivity, ymho
Value
b
2.0
l.lb
35. 7b
15. 2b
5.15b
11,500
"Amount of leachate in each bag is 100 ml.
Samples were taken from the blend of leach-
ates collected on November 8, 1976.
Average value for the Isachates taken from
the 12 generators.
The ionic concentrations were calcu-
lated from the electrical conductivities
using a plot of electrical conductivity and
NaCl concentration for aqueous solutions
(8). This calculation assumes the ions are
principally sodium and chloride. The water
permeabilities of the liner membranes are
calculated from the respective increases in
weight of the liner bags containing the test
fluids.
RECOVERY AND TESTING OF SAMPLES OF A
POLYVINYL CHLORIDE LINER FROM A
DEMONSTRATION LANDFILL
Information from the field regarding the
performance of artificial lining materials on
long exposure to sanitary landfill leachate
has been very limited. First, such use for
these liners, particularly the polymeric mem-
branes, is relatively new, dating from the
early 1970's. Second, effective and economic
methods of retrieving specimens and repairing
linings at the bottoms of landfills have not
been developed.
A demonstration landfill in Crawford
County, Ohio, placed in the spring of 1971,
was lined with a polyvinyl chloride liner.
The liner from this landfill was relatively
accessible as the total fill contained one
lift of 8 ft of refuse and was about 12 ft
deep, including the cover. This demonstra-
tion landfill had been designed to compare
conventionally processed solid waste with
rough and compacted wastes. The various
types of refuse had been placed in essential-
ly waterproof cells lined with plastic mem-
branes. The effect of water content on con-
solidation and decomposition of the refuse
was to be determined. However, all of the
262
-------
INNER BAG
MEMBRANE UNDER TEST
LEACHATE OR
NaCI SOLUTION
(INSIDE INNER BAG)
DEIONIZED WATER
OUTER BAG
POLYBUTYLENE
Figure 12. Schematic of osmosis bag assembly, showing inner bag made of
membrane material under test. The inner bag is filled with
leachate or 5% salt solution and sealed at the neck. The
outer polybutylene bag, which can be easily opened, is filled
with deionized water. The water in the outer bag is monitored
for pH and conductivity; the inner bag is monitored for weight
change.
263
-------
CT>
-e>
TABLE 9. TESTS OF MEMBRANE LINER BAGS FILLED WITH 5% NaCl SOLUTION -
PERMEABILITY OF LINERS TO WATER AND TO IONS DUE TO OSMOSIS
Polymer
Chlorinated
polyethylene
Chlorosulfonated
polyethylene
Elasticized
polyolefin
Polyester elastomer
Polyvinyl chloride
Polyvinyl chloride
Blank
Ion concentration
Liner deionized watera,
no . ppm
77 <1
6 2
36 <1
75 <1
11 <1
59 <1
-
113
Ionsa,
ppm
13
48
5
12
7
10
4
days immersion
"Water" permeability0
g/m2/s x 10~7
21.6
29.1
(0
55.7
5.6
22.8
—
200
Ionsa,
ppm
17
63
6
16
8
12
4
days immersion
"Water" permeability0
g/m2/s x 10~7
18.8
26.5
0.7
63.9
8.3
22.4
—
Concentration of ions (NaCl) in deionized water in outer bags; parts per million calculated from electrical con-
ductivity measurements.
Calculated from the weight increase in the inner bags containing the salt solution.
'Lost weight.
-------
TABLE 10. TESTS OF MEMBRANE LINER BAGS FILLED WITH LEACHATE -
PERMEABILITY OF MEMBRANES TO WATER AND TO IONS DUE TO OSMOSIS
Original values Values at 70 days
Polymer
Chlorinated
polyethylene
Elasticized
polyolefin
Polyester
elastomer
Polyvinyl
chloride
Polyvinyl
chloride
Polyvinyl
chloride
Blank
Liner
no.
77
36
75
11
17
59
—
PHa
5.7
5.1
4.0
5.8
5.0
5.7
5.5
Values at 500 days
Ion Ion Water Ion Water
conc.,b conc.,b permeability,0 cone., permeability,0
ppm pHa ppm g/m/s x 10~7 pHa ppm g/m/s x 10~
3 5.8 16 49.6
2 5.0 5 (d)
10 3.5 41 17.1
3 4.4 18 12.1
7 2.9 190 9.7
3 3.8 35 28.6
<1 5.7 <1
6.5 72 19.6
4.5 10 0.9
6.4 28 12.2
6.0 18 4.6
2.8 190 5.7
6.3 9 5.0
4.3 6
pH and conductivity of deionized water in the outer bag.
Ion concentration of deionized water in outer bag calculated as NaCl from electrical conductivity measure-
ments .
!?Water permeability of liner calculated from weight gain of the inner bag containing leachate.
Lost weight.
-------
cells were flooded with water in a heavy
rainfall just before the fill was closed.
Thus, the original objectives could not be
met and the project was terminated.
In view of the relative accessibility
of the liner, the landfill was opened in
May 1977, after six years, and the membrane
liner was recovered. The cells appeared to
have retained the water. The condition of
the refuse did not appear to be typical of
sanitary landfills. The odor was mild, and
the refuse showed little deterioration. The
samples of liners recovered from the cells
appeared to be in excellent condition with
little difference apparent between samples
taken from the top of the cell, above the
refuse, and those taken from the bottom, be-
low the refuse. The top liner had been un-
der 3 ft of clay cover, and the bottom lin-
er had been under about 2 ft of clay and
was on top of pea gravel. Both liners had
taken the shape of soil and gravel without
breaking. The depressions were as much as
6 in. deep in a 1 ft area in the exposed
top liner.
Results of tests of samples taken from
the top of the fill and from the bottom of
the fill are given in Table 11. However,
there was no sample of the original material
available for comparison. The amount of
swelling and the possible decrease in prop-
erties were within the range of values ob-
served in the immersion testing for the
seven polyvinyl chloride materials. The
specimen taken from the bottom was probably
not in direct contact with the leachate in
the fill during the six years it was in
place. The two-foot soil layer above the
liner was a highly impermeable clay having
a permeability coefficient 1.4 x 10 cm/sec.
The clay layer and the weak leachate
created a situation that is not typical of
what is expected in a fullscale landfill.
ACKNOWLEDGMENT S
The work reported in this paper was
performed under Contract 68-03-2134, "Eval-
uation of Liner Materials Exposed to Leach-
ate", with the Municipal Environmental Re-
search Laboratory of the Environmental Pro-
tection Agency.
The author wishes to thank Robert E.
Landreth for his support and guidance in
this project. He also wishes to thank
Dr. Clarence Golueke and Stephen Klein of
the Sanitary Engineering Research Labora-
tory, University of California, Berkeley,
for their guidance with respect to leachate
characterization.
REFERENCES
1. Haxo, H.E., and R.M. White. First In-
terim Report: Evaluation of Liner Ma-
terials Exposed to Leachate. EPA Con-
tract 68-03-2134, unpublished, 1974.
2. Haxo, H.E., and R.M. White. Second In-
terim Report: Evaluation of Liner Ma-
terials Exposed to Leachate. EPA-600/2-
76-255, U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1976. NTIS
No.: PB259-913.
3. Haxo, H.E., R.S. Haxo, and T.F. Kellogg.
Third Interim Report: Evaluation of Li-
ner Materials Exposed to Leachate, U.S.
Environmental Protection Agency, Cinc-
innati, Ohio, in press.
4. Haxo, H.E. Assessing Synthetic and Ad-
mixed Materials for Lining Landfills.
In: Gas and Leachate from Landfills:
Formulation, Collection and Treatment.
EPA 600/9-76-004, U.S. Environmental
Protection Agency, Cincinnati, Ohio,
1976. NTIS No.: PB251-161.
5. Haxo, H.E. Compatibility of Liners with
Leachate. In: Management of Gas and
Leachate in Landfills, Proceedings of
the Third Annual Municipal Solid Waste
Research Symposium, EPA-600/9-77-026,
U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1977. NTIS No.
PB272-595.
6. ASTM D570-63 (1972) Test for Water Ab-
sorption of Plastics. Part 35. Ameri-
can Society for Testing and Materials,
Philadelphia, PA (1975).
7. ASTM E96-66 (1972). Tests for Water
Vapor Transmission of Materials in Sheet
Form. Parts 18, 20, 35, and 41. Amer-
ican Society for Testing and Materials,
Philadelphia, PA, 1977.
8. Osmotic Parameters and Electrical Con-
ductivities of Aqueous Solutions. Hand-
book of Chemistry and Physics, 54th
Edition, p D235, CRC Press (1973-1974).
266
-------
TABLE 11. PROPERTIES OF POLYVINYL CHLORIDE LINER RECOVERED FROM A
DEMONSTRATION LANDFILL IN CRAWFORD COUNTY, OHIO
ro
CTV
Property
Thickness, mils
Tensile strength, psi
Elongation at break, %
Set at break, %
S-100, psi
S-200, psi
S-300, psi
Tear strength, ppi
Hardness (Duro A) , instant
Puncture resistance, Ib
Elongation, in.
Seam strength (shear) , ppi
Locus of failure
Test
method
—
ASTM D412
ASTM D412
ASTM D412
ASTM D412
ASTM D412
ASTM D412
ASTM D624
ASTM D2240
Fed Std 101
-B-2065
ASTM D413
Liner from
top of fill
(#96)
Machine Transverse
30
2665 2600
340 360
66 79
1290 1245
1830 1750
2245 2300
374 370
77
41.4
0.66
49.5
SEa
Liner from
bottom of fill
(#97A)
Machine
28
2550
325
55
1185
1785
2400
343
78
37.3
0.65
45.5
BRKb
Transverse
—
2475
350
70
1085
1605
2205
341
—
—
—
—
—
aBreak at seam.
in tab.
-------
FORECASTING PRODUCTION OF LANDFILL LEACHATE
Dirk R. Brunner
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
ABSTRACT
The results of several research projects are reviewed with respect to predictable
trends in leachate composition. Two projects resulted in forecasting models which are
briefly described. Potential applications of a technique to forecast leachate production
are provided along with factors which are considered important in making the technique
useful for design, operation and regulation of municipal refuse landfills.
Introduction
Disposal of municipal refuse to the
land results in gaseous and liquid emis-
sions which may have a detrimental effect
on the environment and the public health.
The severity of the effect will depend on
the effectiveness of hydrogeological con-
ditions at the disposal facility and on
the effectiveness of control systems spe-
cially constructed to augment the site's
natural control processes. The character-
istics of the leachate (quantity, composi-
tion and production rate) produced by
rainwater infiltrating the decomposing
wastes greatly influence the effectiveness
of natural control processes. The ability
to estimate the leachate characteristics
which the surrounding environment must
accept has not received much attention,
despite the fact that such information can
be very useful in reducing the subjective-
ness of environmental assessments and im-
proving the design of disposal facilities.
This paper is intended to describe the
need for a leachate forecasting procedure,
why achievement of such a goal seems
plausible, and what factors are considered
important.
Background
The practice of municipal refuse
disposal by sanitary landfill ing has been
studied sporadically for several decades.
Eliasson (1) characterized leachate from
a few metropolitan New York landfills and
estimated the moisture requirements for
vigorous biological activity. Merz (2)
using plywood bins placed in an operating
landfill provided several months of data
on leachate composition. The work by Merz
and Stone (3) identified the importance of
moisture content and temperature on the
rate of waste decomposition which was
estimated by measuring gas production.
The work of Fungaroli (4) yielded
long-term information on leachate charac-
teristics under simulated East Coast
precipitation/infiltration conditions, and
successfully described the movement of
leachate in groundwater underlying a
field-scale test cell containing several
hundred tonnes of refuse. Hydraulic and
long-term leaching characteristics of
shredded refuse were also reported. The
work of Burchinal and his co-workers em-
phasized the importance of microbial
activity within a landfill (5-6). Tempera-
ture and moisture were identified as being
very important in controlling the microbial
activity; the importance of depth of
leached waste was studied.
These and other studies indicated a
potential for water pollution was created
by leachate which generally originated
from water percolating landfilled, micro-
bially active municipal solid waste. A
common factor of these early studies was
intentional application of water to the
"landfill." A common criticism at that
time (late 60's) was that leachate was a
laboratory anomally; that operating
268
-------
landfills which followed good practice
(compact the refuse, cover daily, select
and slope cover material to shed water)
were not known to have created or threaten
surface or groundwater contamination nor
even if leachate was produced.
The Solid and Hazardous Waste Re-
search Division (SHWRD), EPA installed a
395 tonne experimental landfill (Test Cell
1) at its Boone County Field Site (BCFS)
to determine if application of good prac-
tice would produce a leachate and, if so,
the composition. The volume of leachate
collected was in general agreement with
estimates made according to the procedures
of Thornthwaite which were applied to
landfills by Remson et al (7) and Fenn
et al (8). Four additional experiments
were installed at the BCFS: three 2
tonne, 0.91m diameter test cells (2A, 2B,
and 2C) and one 72 tonne, 8.5m square test
cell. The purpose of these test cells was
to determine the replication of small-
scale experiments and the comparable
performance of large and small-scale test
cells. Wigh (9) has presented a review of
results from these five experimental
landfills located at the BCFS.
Sensitivity of leachate composition
to different infiltration rates was one of
the objectives of a series of 19 experi-
mental landfills constructed by USEPA at
the Center Hill Facility in Cincinnati.
There were constructed identical to the
small scale test cells at the BCFS; re-
sults have been periodically reported by
Jackson (10), Streng (11-12) Swartzbaugh
(13) and Walsh (14).
Observations
A review of the BCFS results and
other studies where the landfilled refuse
has been subjected to single pass leaching
of a batch of refuse. (No recirculation of
leachate and no addition of fresh refuse)
indicates leachate composition follows
similar trends (Figure 1). Assay results,
expressed as concentrations, tend to peak
at the same time that the refuse begins to
leach in equilibrium with infiltration,
followed by a gradual decline to a low-
level concentration which persists for a
long time. The apparent relationship of
the peak concentration and attainment of
field capacity was noted by Wigh for a
number of assays performed on the BCFS
leachates (Table 1). Results of
Pohland (15) suggest that experimental
landfills which are rapidly brought to
field capacity achieve peak concentrations
only after the microbial activity has had
sufficient time to influence leachate
composition.
Constituents in leachate from any
particular study are subject to variations
(Figures 2&3) from sample to sample, but as
a whole follow the general declining trend
depicted in Figure 1. More consistent
trends were noted when assays were repre-
sented as a function of cumulative leachate
volume (Figure 4). The results of several
different experimental landfills at the
Center Hill Facility (Figure 5) followed a
very similar trend, regardless of the
rate of infiltration; the addition of per
capita equivalent sewage sludge and 3% by.
weight of CaCOs had no significant effect
on the general trend. The empirical
results" showed greatest variation during
the initial leaching which represented
leachate collected prior to and immediately
after field capacity. The net throughput
of water, measured as infiltration or
leachate, is seen to be an important
variable in describing leachate composition.
The mass of material released from
these experimental landfills has also
followed very consistent trends. Release
of total solids (Figure 6) for an experi-
ment receiving 813 mm/yr of infiltration
decreased gradually as the volume of
infiltration (leachate) increased. Compar-
able experiments, but receiving 406 mm/yr
and in some cases with additive materials
(initial water, sewage sludge, and CaCOJ,
released total solids in similar patterns.
The consistency of such observations
led some investigators to consider empiri-
cal modeling. Wigh (16) showed good agree-
ment between BCFS - TC2 data and an equa-
tion which contained empirically determined
constants (Figure 7). The peak concentra-
tion and the volume of leachate when the
peak occurred were used to solve the equa-
tion; constants KI and l<2 were determined
by trial and error. The resulting equation
when applied to an identical experiment
yielded a 3.5% over-estimate (@ 1200 mm)
of actual, empirical results, and when
applied to a comparable field scale experi-
ment yielded a 9.2% underestimate (@ 1400
mm). The equation in its present form,
however, is applicable only to systems
built and operated in a comparable manner.
269
-------
CUMMULATIVE
LEACHATE
VOLUME
TIME
CONCENTRATION
TIME
FIGURE 1. General response of leachate
composition from a single pass leaching of
a fixed amount of municipal refuse.
270
-------
TABLE 1. PEAK CONCENTRATIONS AND FIELD CAPACITY
EXPERIMENT
PEAK
2A
EXPERIMENT
PEAK
2B
PARAMETER
COD
Total
Kjeldahl-N
Ammonia-N
Ortho-
phosphate
Sulfate
Sodium
Potassium
Chloride
Iron
Magnesium
Manganese
Calcium
Zinc
Hardness
Total Solids
Alkalinity
Acidity
Conductivity
Mean
CONCENTRATION
57330
1560
1035
390
1306
1900
2225
2335
1547
486
109
2280
150
7067
46484
11535
6720
17000
Standard Deviation
Leachate
Field Capacity6
TIME
51
51
65
43
51
53
49
51
53
51
43
49
49
45
51
51
45
53
50.2
4.9
43
43
CONCENTRATION"
61600d
1897
1185
185
2000
1700
2939
2343
2902
617
115
4000
360
10575
45628
13880
6843
18000
TIME1"
37
63
63
45
63
49
65
59
37
63
39
39
49
37
49
29
49
53
49.3
11.4
27
43
b. mg/1
c. Weeks since
d. Early peak,
a. From Boone
e. From water
construction
conentration later dropped
County Field Site Test Cell
storage calculations.
and
s 2A
peaked again on 11/7/73
& 2B.
sample.
271
-------
PO
~J
PO
QUARTERLY MEAN
1971
1972
1973
1974
1975
FIGURE 2. Boone County Field Site Test Cell 1 weighted mean chemical
oxygen demand concentration.
-------
ro
•»j
GO
1,800
1,600
1,400
^5 1,200
S 1,000
800
600
400
200
ae.
O
O MONTHLY MEAN
O-- —QUARTERLY MEAN
1971
1972
1973
1974
1975
FIGURE S.Boone County Field Sight Test Cell 1 weighted mean chloride
concentration.
-------
60.00
- 50.00
0)
2 40.00
O 30.00
to
^ 20.00
2 10.00
0.00
60.00
- 50.00
o>
2 40.00
O 30.00
to
^ 20.00
i—
2 10.00
0.00
_L
_L
_L
_L
_L
oo K O> o
•* oo oo •—
O -- cs Tt m
* "*: oo o e^
.oo^l^^^^,^
TIMEDAYSxlO° "~ ""
O
O
CUMULATIVE LEACHATE VOLUME,
LITERS/kg OF DRY REFUSE
FIGURE 4. Total solids concentration from
experimental refuse landfill leached @813
mm/yr.
274
-------
72,000
C4-
o>
E
<
c*
H-
z
LU
U
60,000
•MUNICIPAL REFUSE LEACHED @813mm/yr.
* " " " @406mm/yr.
o 'I II AND SEWAGE SLUDGE
LEACHED @ 406mm/yr.
AMUNICIPAL REFUSE WITH 3 % BY
WEIGHT OF Ca CO3 AND LEACHED
@ 406mm/yr.
48,000
.A
o: +
.AA+
36,000
24,000
O 12,000
*oo
0 0
1.0
2.0
3.0
CUMULATIVE LEACHATE VOLUME,
I/kg DRY REFUSE
FIGURE 5. Total solids concentrations released
from different experimental landfills.
275
-------
ui 54.0
to
LL.
LU
>- 45.0
c*
LL.
O
o> 36.0
\
E
CD
£ 27.0
O
S
LU
* 18.0
to
0
~
0
to on
* • ^
—i
^f
t—
O
H-
_
•
A©'
.0*
++ oV
4- '0
. 0
+ ' ov
-f-*/0^
.Q V • MUNICIPAL REFUSE LEACHED @813mm/yr.
_ 1 . V + " II II @406mm/yr.
1 **O O " '• SLUDGE AND SEWAGE
ij- O V7 LEACHED @406mm/yr.
T OV ^ AAUNICIPAL REFUSE AND 3% BY WEIGHT
_|J" •* OF CQCo3 AND LEACH
,*O ED @406mm/yr.
.n ^ 1" I" PLACED @ FIELD CAPA
+ CITY AND LEACHED
~ *O @406mm/yr.
, . y li M AND INORGANIC PIG
•T. MENT WASTE LEACH
* ED @406mm/vr.
W » II LEACHED @406mm/yr
T @21°C (7°C WARMER THAN OTHERS)
1 1
0 1.0 2.0 3.
CUMULATIVE LEACHATE VOLUME,
LITERS/kg OF DRY REFUSE
FIGURE 6. Total solids removed from different
experimental landfills.
276
-------
LL1
WEIGHTED MEAN CHEMICAL OXYGEN DEMAND,mg/l
c
O -i
O CD
I N
n
O IT1
II.
•< -I
31 S
(D
10
o
c
c
r~
>
>
n
O
i—
c
£
m
3
3
•tfc
o
o
oo
O
o
10
o
o
o
c
2
m
II
io
U1
IO
O
O
O
O
p
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O
O
O
b
O
O
to
-------
Qasim (17) developed a concept pro-
posed earlier (18) which assumed chloride
can be used as a surrogate parameter of
landfill leachate and that chloride con-
centration may be determined on the basis
that adsorption occurs at a rate propor-
tional to the concentration of solute in
the liquid phase and the difference between
the actual and maximum possible concentra-
tion of the solute absorbed on the solid
particles. Comparison of empirical data
with theoretical estimates were generally
good during the initial phase of the study,
but tended to underestimate chloride con-
centrations as leaching continued. Proce-
dures for applying the concept were also
provided. Relationships of dimensionless
parameters and equation constants need to
be verified for conditions prevalent in
the field, and the long-term accuracy of
estimates improved.
The limited success of initial
attempts to describe leachate composition
and the consistent trends of data obtained
from experimental landfills indicates that
further development is warranted.
Need for a Forecasting,Procedure
The ability to describe leachate
characteristics is considered a signifi-
cant improvement in the design and regu-
latory review processes and in guiding the
operational aspects of the landfill. It
is also expected to improve the confidence
and reliability of estimates describing
the capability of the hydrogeological
setting of any specific location to prevent
contamination of groundwater. Evaluation
of the continued threat to the groundwater
posed by abandoned, completed, or active
disposal facilities would also be possible
with such a tool.
Decisions regarding the suitability
of the hydrogeological setting to allevi-
ate any threat of groundwater contamination
can be improved by using a forecasting
procedure to estimate the rate, duration,
total quantities, and concentration of
materials which will be leached. Attenu-
ative capabilities of soils are dependent
in part on the total amount of material to
be removed, and the concentration. A site
considered marginal due to limited attenu-
ative capability could be utilized by
identifying the amount and time during
which materials should be removed from
the leachate (by treatment, recirculation,
or other techniques) prior to discharge to
the underlying soils (Figure 8).
In a similar manner, existing dis-
posal facilities may be evaluated to de-
termine if corrective action is warranted
to eliminate perceived or existing ground-
water pollution problems. A conceptual
framework is provided by a forecasting
model to estimate the release pattern of '
pollutants. The need for corrective action
can be established after field verification
of the prediction and appropriate control
measures selected based on estimated future
contaminant release. Costly and unneeded
installation of corrective measures can be
avoided in a rational and environmentally
sound manner.
The performance requirement of both
leachate collection and treatment systems
could be tailored to meet the needs of the
hydrogeological setting by using a leachate
forecasting procedure. Cost effective and
environmentally sound decisions regarding
the allowable transmission of leachate
through a liner system to underlying soils,
and the performance life of a liner system
could be determined. Estimation of long-
term costs and decisions regarding respon-
sibility for operation and maintenance of a
leachate treatment system would be aided.
Operational aspects of a landfill
could be managed to affect the infiltration
rates and hence the time during which the
more contaminated leachates.may be ex-
pected. It may be advantageous from a cost
and management basis and ultimately envi-
ronmentally sound to construct the landfill
in a manner which will introduce greater
quantities of infiltrating water during the
operational life than to prolong the
release of contaminants until after the
site is not operating and resources may be
difficult to secure for construction and
operation of a control system.
The inability to describe or forecast
leachate production was evident at two
landfills where leachate treatment systems
were designed, based on field sampling and
laboratory analysis, and built but re-
quired significant modification because the
characteristics of the leachates had „
changed. In one case, the leachate had
decreased in quality to such an extent that
the treatment process selected (anaerobic
filter) was ineffective. The leachate
composition at the other landfill had
278
-------
<
ex.
u
Z
O
LEACHATE TREATMENT
REQUIRED
PRIOR TO DISCHARGE
TIME FROM START OF OPERATION
FIGURE 8. Leachate production from a refuse landfill
operated for several years.
279
-------
increased significantly, and additional
treatment facilities were needed.
Elements of a Forecasting Procedure
A leachate forecasting procedure
should be sensitive (responsive to changes)
to the following items to be useful in
meeting the design, regulatory and opera-
tional needs:
1. Mass of waste
2. Geometric configuration (depth,
surface area)
3. Waste composition (to the extent
that increasing quantities
of unique wastes such as industrial
or municipal sludges can be
evaluated
4. Infiltration (leachate production,
moisture throughput)
5. Temperature
6. Microbial activity
The list is not intended to be com-
plete, but it is representative of con-
clusions from laboratory studies and field
observations. The need to include the ma-
jority of these items is obvious; a special
note regarding microbial activity is
warranted.
The decomposition of municipal refuse
proceeds through poorly-defined processes
which include physical, chemical, and
biological action. The role of microbial
activity is expected to be very signi-
ficant in determining the characteristics
of leachate. Farquhar and Rovers (19)
proposed several sequential phases (char-
acterized by landfill gas composition) of
microbial activity. Leachate and gas are
the two modes of transport for microbial
metabolic processes, consequently, signi-
ficant changes in offgases may well be
expected to represent microbial population
and/or metabolic shifts which will also
affect leachate production. The work of
Pohland (15) clearly shows the interrela-
tionship of gas and leachate composition;
they are the result of dynamic microbial
activity. There is, unfortunately, a
severe lack of quantitative information on
gas and leachate production under con-
trolled laboratory or pilotscale condi-
tions; explicit description of the rela-
tionship between gas and leachate produc-
tion is a desirable goal, but one which
will require several years to achieve with
any empirical support.
The forecasting procedure should have
another desirable attribute: a sound con-
ceptual bases. The use of an empirically
derived regression equation may be useful
under certain conditions, but the utility
of the forecasting procedure would be
severely curtailed if it were not respon-
sive to changing characteristics of land-
fill design and operation and solid waste
characertisties. Although a myriad of
physical, chemical, and biological reac-
tions are involved in refuse decomposition,
the description of the processes in an
equilibrium or dynamic manner would not be
possible with the existing data base;
the mechanics of using the resulting
forecasting procedure would likely be so
burdensome as to preclude its use.
Identification and development of the
primary phenomena controlling leachate
production would be a preferable basis to
such a complex approach. For example,
leachate composition may be controlled by
rate limiting reactions, where the composi-
tion is principally dependent on the rate
of leachate movement through the waste
because the rate of solubilization is slow
relative to the rate of leachate flow.
Saturation limiting reactions may also pro-
vide a better description, where composi-
tion is dependent on complex solution
equilibria which occur fast relative to
leachate flow. Concentration gradients
between the flowing leachate and a stagnant
water film over the refuse particles is
being evaluated as a basis for a forecast-
ing procedure (20). Certainly, the compo-
sition of leachate will be dependent on the
finite material available for solution.
Ham and Stegman (21) have described pheno-
mena which were considered important in
their developmental work on waste extrac-
tion procedures. A review was also pro-
vided in a compilation of extraction and
leaching procedures (22).
Development of a useful forecasting
procedure must be responsive to incremental
additions of solid waste as is encountered
in day to day landfill operations. The
proposed procedure must also be verified
by comparing projected composition and
mass removals with long-term observations
made at field sites where volume and compo-
sition of leachate, the mass of refuse and
other parameters are measured.
280
-------
Summary
An appreciable amount of information
on leachate production has been collected
over several decades. Results of several
experiments seem to follow very consistent
trends which can be described using empiri-
cal models, but these models are limited in
their applications, because they describe
leachate from batch-type laboratory and
pilot scale experiments of relatively
shallow depth. A need exists for a leach-
ate forecasting procedure which will be
sensitive to waste characteristics, site
geometry, infiltration, temperature, and
microbial activity. Such a procedure would
be useful for design, operation and regula-
tory purposes. A conceptual framework would
be established from which quantitative and
rational estimates of leachate production,
could be made. These estimates are needed
for designing, and operating leachate
collection and treatment systems, for
assessing the adequacy of the site hydro-
geology to prevent groundwater contamina-
tion, for planning the operational filling
of the disposal site, and for assessing the
need for remedial or corrective action at
completed or operating disposal facilities
to alleviate a real or suspected ground-
water contamination condition. The proce-
dure should be conceptually sound but
should not be so complex as to inhibit its
usefulness.
References
1. Eliasson, R.; Decomposition of Land-
fills. American Journal of Public
Health. 32 (9), 1029-1037. 1942.
2. Merz, R.C. "Investigation of Leaching
of a Sanitary Landfill" California
State Water Pollution Control Board
Report No. 10. Sacramento, California,
1954.
3. Merz, R.C. and R. Stone. Special
Studies of a Sanitary Landfill.
National Technology Information
Service. PB 196148, U.S.D. HEW.
1970.
4. Fungaroli, A.A. Investigation of Sani-
tary Landfill Behavior. EPA-600/2-
79-053a&b. U.S. Environmental Pro-
tection Agency, Cincinnati, Ohio
June 1979.
5. Lin, Y.H. Acid and Gas Production
from Sanitary Landfills. Ph.D.
Thesis. University of W. Virginia,
Morgantown 1966.
6. Burchinal , J.C. Microbiology and
Acid Production in Sanitary Landfills:
Summary Report. USEPA Research Grant
EC 00249. Cincinnati, 1973.
7. Remson, I. ejt al_. "Water Movement in
an Unsaturated Sanitary Landfill."
Proceedings of the American Society of
Civil Engineers 94(SA2): 307-316.
April 1968.
8. Fenn, D.G. et al_. Use of the Water
Balance Method for Predicting Leachate
from Sanitary Landfills.
9. Wigh, R. "Leachate Production from
Land-filled Municipal Wastes" in
Municipal Solid Waste: Land Disposal
and Resource Recovery. Orlando, Florida,
March 26, 27, and 28, 1979.
10. Jackson, A.G. and D.R. Streng. Gas
and Leachate Generation in Various
Solid Waste Environments" in Gas and
Leachate from Landfills: Formation.
Collection and Treatment. EPA-600/9-
76-004, USEPA, Cincinnati, Ohio
March 1976.
11. Streng, D.R. "The Effects of the
Disposal of Industrial Waste Within
a Sanitary Landfill Environment" in
Residual Management by Land Disposal
LPA-bOU/9-76-015, USEPA, Cincinnati,'
July 1976.
12. Streng, D.R. "The Effects of Industrial
Sludges on Landfill Leachates and Gas"
in Management of Gas and Leachate in
Landfills. EPA-600/9-77-026. September
1977.
13. Swartzbaugh, J.T. "Co-disposal of In-
dustrial and Municipal Wastes in a
Landfill" in Land Disposal of Hazardous
Bastes. EPA-6UO/9-/8-016. August 1978.
14. Walsh, J. and R. Kinman, "Gas and
Leachate Production under Controlled
Moisture Conditions." in Municipal
Solid Waste: Land Disposal and Resource
Recovery. Orlando, Florida. March 26,
27, and 28 1979.
281
-------
15. Pohland, F.G. Sanitary Landfill
Stabilization with Leachate Recycle
and Residual Treatment. EPA-600/2-
75-043. USEPA Cincinnati, Ohio
October 1975.
16. Wigh, R.J. Boone County Field Site
Interim Report: Test Cells 2A, 2B,
2C & 2D. EPA-600/2-79-058. USEPA,
Cincinnati, Ohio. June 1979.
17. Qasim, S.R. and J.C. Burchinal.
"Leaching of Pollutants from Refuse
Beds." Jour. San. Eng. Div. ASCE; 96_
(SA1) 49-58 February 1970.
18. Effect of Refuse Dumps on Groundwater
Quality. California State Water
Pollution Control Board, Report No.
24. Sacramento 1961.
19. Farquhar, G.J. and F. Rovers. "Gas
Production during Refuse Decomposi-
tion." Water. Air and Soil Pollution
2, 483, 1973.
20. Mooij, H. "Solid Waste Research
Activities in Canada." in Municipal
Solid Waste: Land Disposal and
Resource Recovery. Orlando, Florida.
March 2628, 1979.
21. Ham, R. et al. Final Report: Compari-
son of Three Waste Leaching Tests.
EPA-600/2-79-071 U.S. Environmental
Protection Agency, Cincinnati, Ohio
1979.
22. Lowenbach, W. Compilation and Evalu-
ation of Leaching Test Methods. EPA-
600/2-78-095. U.S. Environmental
Protection Agency, Cincinnati, Ohio.
May 1978.
282
-------
PILOT-SCALE INVESTIGATIONS OF ACCELERATED
LANDFILL STABILIZATION WITH LEACHATE RECYCLE
Frederick G. Pohland, David E. Shank, Ronald
E. Benson and Herbert H. Timmerman
School of Civil Engineering
Georgia Institute of Technology
Atlanta, Georgia 30332
ABSTRACT
Pilot-scale investigations of accelerated landfill stabilization with leachate
recycle continue to demonstrate the advantage of this solid waste management option
with respect to process control and predictability. Stabilization of readily available
organic materials contained in shredded municipal solid waste and transferred to recycled
leachate was essentially completed within about six months with a concomitant accele-
rated production of gas. Landfill behavior during periods of rapid stabilization fol-
lowed predictable patterns as measured by selected parameters including TOG, COD, BOD,-,
total volatile acids, pH, conductivity, total alkalinity, gas production and composition,
ORP, and chlorides. The inter-relationships of these parameters and their application
for interpretation of landfill stabilization during leachate recycle are described within
a landfill management perspective.
INTRODUCTION
Emerging regulations governing land
disposal of solid wastes continue to
require safeguards against the migration
of reaction products from landfill sites
into the environment. Much of this empha-
sis arises due to the concern over the
consequences of leachate and gas produc-
tion. The production of both leachate
and gas are inextricably related and
therefore tend to manifest themselves in
an often unpredictable and elusive fashion.
Under such circumstances, the environ-
mental impacts of leachate and gas migra-
tion from landfills are frequently eval-
uated only after the fact and without much
opportunity for providing an immediate
and lasting remedy. This dilemma is a
direct outgrowth of past landfill manage-
ment practices and a tradition of attempt-
ing to isolate all landfill sites and
store their contents in perpetuity.
From an engineering point of view, it
is most important to ensure and maintain
operational control over landfill disposal
of solid wastes in order to provide lasting
guarantees against environmental impairment.
Therefore, the concept of confinement of
the site and control over the reaction
products within the site becomes an attrac-
tive option. Indeed, with the enactment
of the Resource Conservation and Recovery
Act of 1976 (P.L. 94-580) and the resultant
guidelines for the control of hazardous
wastes, such a management strategy almost
becomes a necessity. Confinement, however,
implies isolation, accumulation, collection,
and regulated treatment or release of con-
taminants for which several procedures may
be considered.
Recognizing the eventual need for
collection and treatment of leachate at
certain landfill sites, efforts have been
made to investigate the relative propriety
283
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of both biological and physical-chemical
treatment methods. These have been pre-
sented and reviewed elsewhere(l~3) with
descriptions of operational characteristics,
limitations, and relative economics of
application. Collectively, these efforts
indicate that preparations for separate
leachate treatment, except possibly for
controlled discharge to an existing sewer-
age system, become exceedingly challenging
particularly in view of the many uncer-
tainties regarding leachate quantity and
quality. Moreover, since actual leachate
production, without intentional addition
of moisture to the landfill either during
operation or after closure, is generally
delayed for an indeterminate number of
years, treatment becomes an ex post facto
proposition, the eventual implementation
of which and its effectiveness then becomes
a matter of considerable conjecture.
To alleviate some of the problems
heretofore described and to address the
issues of control and predictability of
landfill behavior, research on the concept
of leachate containment, collection and
recycle utilizing the landfill as a treat-
ment system has been conducted at Georgia
Tech for the past eight years. It is the
purpose of this report to review selected
results of more recent studies and to
demonstrate that leachate recycle is a
viable management option for solid waste
disposal sites.
5 LW ULATED SANITKR Y LANDFILLS
( no teat* )
EXPERIMENTAL TECHNIQUES
Prototype Landfill Configuration
To augment the results of the initial
landfill column studies(^ and to permit
investigations on a larger scale, leachate
recycle studies were extended with the
construction of two simulated landfill
cells as illustrated in Figure 1.
The essential differences between
the operation of these cells and the
original columns were that the new cells
were filled with about ten feet of shred-
ded municipal solid wastes, were allowed
Figure 1. Pilot-Scale Landfill Cells
with Leachate Recycle
to reach field capacity in response to
natural rainfall, and were constructed
to permit gas collection and analysis of
the effects of evaporation. One cell was
left open to incident rainfall, the other
was sealed to allow for gas measurements
and to prohibit loss of moisture by evapo-
ration. Accordingly, the amount of rain-
fall received by the open cell was measured
and an equivalent amount of tap water was
284
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added to the sealed cell.
The landfill cells were each construc-
ted of reinforced concrete, 10 feet square
by 14 feet deep, with a sloping base. All
exposed surfaces were covered with a
sealant and the interior-walls were cus-
hioned with styrofoam prior to insertion
of a continuous Hypalon R liner. This
liner was left open at the top in the open
cell and covered to form a completely
sealed enclosure for the sealed cell. This
enclosure was finally sealed with a 0.25-
inch thick steel lid.
A system of underdrains bedded in
gravel was placed both above and below the
liner in the bottom of each cell to permit
leachate collection for recycle and examin-
ation for liner integrity with time.
Leachate collection was accomplished with
55-gal sumps from which it could be pumped
through a distribution system placed in
gravel at the surface of each cell just
above the solid waste and below a 2-foot
layer of soil cover.
The conduits for leachate collection
and recycle were of 2-inch PVC pipe;
underdrains and distribution laterals were
perforated with 0.5-inch diameter holes
drilled 4.0 inches on center. Two gas
collection networks were also employed
with the sealed cell. The principal
gas collection system consisted of a
length of 0.75-inch diameter PVC pipe
extending from the leachate distribution
conduit. The alternate system was designed
to collect gas which had migrated into
the void space above the cover soil and
below the confining lid. In addition to
these gas collection systems, temperature
probes were placed into the interior of
each cell to provide a continuing record
and comparison of cell temperatures with
ambient conditions.
Facility Operation
Upon completion of the construction
of the landfill containment structures,
each received residential-type solid waste
collected and shredded to a nominal size
of 2.5 to 3.0 inches in DeKalb County,
Georgia. The shredded solid waste was
delivered to the facility site and placed
in 2.0-foot increments to a manually
compacted density of 537 pounds/cu.yd.
The final compacted depths of solid waste
were 9.0 feet and 8.5 feet in the open and
sealed cells, respectively. The initial
filling operation was completed on
August 13, 1976 with the installation of
the leachate distribution system, the final
2.0 feet of cover soil, and closure of the
sealed cell. Over the next year, the cells
were allowed to reach field capacity with
incident rainfall or water addition to the
respective open and sealed cells. During
this period, rainfall, temperature and
relative humidity were recorded, the cells
were checked for any leachate production,
and the sealed cell was sampled for possible
gas evolution.
Although some leachate appeared in
both cells in small quantity on an inter-
mittent basis, it -did not appear regularly
until the Fall of 1977. Accordingly,
September 1, 1977 was selected as the time
that leachate production nominally began.
Thereafter, samples were periodically
collected for analysis from the recircu-
lation sump of each cell and available
leachate was recycled at about weekly
intervals. By day 208, enough leachate
was available to initiate daily recycle
and 200 gallons/day/cell were recirculated.
This procedure was employed until day 346
when the daily recycle quantity was reduced
to that quantity capable of being passed
through the open cell in one day. Every
other day recycle was initiated on day 401
and the amount recycled through each cell
was gradually reduced to about 40 to 50
gallons.
Analytical Procedures
As the solid waste was being placed,
six compacted samples were collected and
analyzed for density, moisture, total
volatile solids, calorific value, and
CHN content. The leachate samples collec-
ted from both cells were analyzed for pH,
ORP, conductivity, volatile acids, TOC and
285
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TIC, BOD,-, COD, total suspended, and
volatile solids, total alkalinity, nitrogen,
phosphorous, sulfates, Chlorides and
selected metals (Fe, Ni, Mn, Cr, Cd, Mg,
Cu, Na, K, Ca, Zn, Al, Pb) . Gas samples
were analyzed for C02, 0-, N CH, and H-.
Standard Methods(4) techniques , supplemented
with instrumental analyses, were used
thoughout the studies.
EXPERIMENTAL RESULTS AND DISCUSSION
Selected data from the studies are
presented in Table 1 and Figures 2
through 13. These data reflect the most
pertinent results of environmental con-
ditions existing during the test period
as well as solid waste characteristics
and analyses on leachate and gas samples.
The time scales used in this presentation,
i.e., time since placement of solid waste
and time since leachate production began,
are related in that nominal leachate
production began 383 days after the solid
waste was initially placed in the cells.
Solid Waste Characteristics
The original character of the solid
waste utilized in the study is included
in Table 1. These analyses were intended
to provide some comparative information on
the constituent nature of the solid waste
and an opportunity for final characteri-
zation after leachate recycle and stabi-
lization had been completed.
Environmental Conditions
The weekly ranges in maximum and
minimum ambient and internal cell tempera-
tures are presented in Figures 2 and 3,
respectively. These temperatures were
continuously monitored, and although
diurnal variations were observed, weekly
averages of low and high temperatures were
considered sufficient to display the sea-
sonal variations to which the cells were
exposed. Accordingly, ambient temperatures
varied from a low of -12.2°C in January
1977 to a high of 42.2°C in July 1977.
Because of some insulation, these variations
in low and high temperatures were not so
dramatic in the landfill cells. The open
cell ranged from a low of 12°C to a high of
38.5°C and the sealed cell varied between
a low of 6.5°C and a high of 41°C. The
somewhat lower and higher temperature ranges
in the closed cell were considered a con-
sequence of the isolated nature of that
cell which influenced the effects of warm-
ing during the day and cooling at night.
However, the differences noted between the
average temperatures of the two cells were
not considered significant to the overall
stabilization rates of the solid waste and
leachate between the two cells at least
within the time frame of the study period.
The incremental and cumulative rain-
fall incident on the open cell and added
as tap water equivalent to the sealed cell
are indicated in Figure 4. Except for
some relatively dry periods during the
Table 1
Original Characteristics of Solid Waste Used During
Pilot Scale Investigations with Leachate Recycle
Parameter
3
Density as placed, Ib/yd
Moisture Content as placed, "L
Total Volatile Solids, % dry
Carbon, % dry
Hydrogen, % dry
Nitrogen, % dry
Calorific Value, BTU/lb dry
Average Analysis*
537
33,
75.
45.3
5.46
3.33
7758
*Average of six representative samples.
286
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20 40 60 10 100 120 140 160
TIME SINCE PLACEMENT OF SOLID WASTE, weeks
Figure 2. Ranges of Weekly Maximum and Minimum
Ambient Temperatures at Test Site
OPEN CELL
SEALED CELL
0 20 40
T- Auguet 13 .1976
100
977
. DU OU
L— September 1 , 19
TIME SINCE PLACEMENT OF SOLID WASTE, weeks
Figure 3. Ranges of Weekly Maximum and Minimum
Temperatures within the Landfill Cells
287
-------
120-r 6T
0 200
^—August 13,1976
400 600
Se ptember 1.1977
TIME SINCE PLACEMENT OF SOLID WASTE, fflys
Figure 4. Incremental and Cumulative Rainfall at Test Site
CO 120 160 240 300 360 420
TIME SINCE LEACHATE RECYCLE BEGAN days
Figure 5. Total Organic Carbon Concentrations in Leachates
from Pilot-Scale Landfill Cells
288
-------
latter stages of the study, rainfall was
relatively consistent with an accumulation
of about 120 inches at the end of the
report period.
Leachate and Gas Characteristics
Selected analytical data accumulated
during 520 days of leachate production with
either intermittent, daily or every other
day leachate recycle are indicated in
Figures 5 through 13. Recognizing that
those parameters commonly employed to
measure pollutional potential are parti-
cularly germane to the identification and
solution of problems associated with the
production of leachate, TOC, COD and BOD,.
were used to reflect that pollutional
potential derived from the decomposition of
organic matter. As indicated in Figures
5, 6 and 7, all three parameters exhibited
essentially the same pattern with leachate
recycle. During initial weekly recycle
periods, the data were somewhat erratic
particularly for the sealed cell where the
even distribution of rainfall across the
entire surface of the landfill apparently
was not simulated by the introduction of
equivalent water through the recycle
distribution system of the sealed cell.
However, once daily recycle procedures
were initiated, these variations were
moderated in both cells and more even and
rapid decreases in pollutant concentra-
tions were experienced.
Notwithstanding dilution effects, the
rapid decline in pollutant concentrations
in the leacbate as consequenced by daily
recycle was considered primarily indi-
cative of an initial acceleration of
biological stabilization of the more
readily available organics contained with-
in each cell. Consequently, daily
recirculation of leachate served to pro-
vide a continuing exposure of the internal
biological populations to nutrients con-
tained in the leachate and thereby enhanced
overall conversion of those constituents
as well as those in the solid waste and
transferred to the leachate during passage.
Since biological stabilization during
landfill disposal of solid waste depends
largely on anaerobic microbial activity,
it is possible to further interpret the
observed changes in pollutional character-
istics of the leachate. If the two-
phase process of acid fermentation with
the production of intermediates such as
the volatile acids followed by fermentation
of these acids to CH. and C0_ is applied,
then the results of Figures 5 through 7
should also be reflected by an initial
appearance and subsequent utilization of
volatile acids. Indeed, inspection of
Figure 8 indicates a similar rise in
volatile acids followed by their virtual
elimination (below detectable limits)
particularly after daily leachate recycle
was instituted. It is also interesting
to note that reductions in these parameters
in the sealed cell preceded those in the
open cell although the eventual results
were the same. This difference could be
attributed to the preferred environment
provided to the volatile acid utilizers
by the sealed cell, i.e., a more positive
exclusion of oxygen and its detrimental
influence on the obligate anaerobic methane
formers.
As could be anticipated, as volatile
acids accumulated, pH decreased as indi-
cated in Figure 9. Moreover, this decreased
pH condition was sustained until the vola-
tile acids were converted and removed; the
change in pH toward neutral was again more
rapid in the leachate of the sealed cell
than in that of the open cell. This pH
change in both cells was indicative of a
buffer shift from that established by the
volatile acids to that of the more favor-
able bicarbonate buffer system which is
also considered necessary for efficient
CH, production. This shift is further-
more illustrated by 'decreases in con-
ductivity as well as- in total alkalinity
attributable to the Volatile acids as
illustrated in Figure 10.
Following the production and accumu-
lation of volatile acids with the con-
289
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0 60 120 160 240 300 360
TIME SINCE LEACHATE RECYCLE BEGAN, days
Figure 6. Chemical Oxygen Demand of Leachates from
Pilot-Scale Landfill Cells
OPEN CELL
SEALED CELL
200 250 300 350 400 450 500
TIME SINCE LEACHATE RECVCLE BEGAN, dlys
Figure 7. Biochemical Oxygen Demand of Leachates
from Pilot-Scale Landfill Cells
290
-------
CO 120 180 240 300 360
TIME SINCE LEACHATE RECYCLE BEGAN, dayi
420
Figure 8. Total Volatile Acids Concentration in Leachates
from Pilot-Scale Landfill Cells
OPEN CELL
SEALED CELL
60 120 180 240 300 360 420 480
TIME SINCE LEACHATE RECYCLE BEGAN,days
Figure 9. Conductivity and pH of Leachates from
Pilot-Scale Landfill Cells
291
-------
20
18
O 1 6
14
12
-WEEKLY RECYCLE
DAI LY RECYCLE
OPEN CELL
SEALED CELL
120 180
240 300 360 420 4SO
TIME SINCE LEACHATE RECYCLE BEGAN, diyl
Figure 10. Total Alkalinity of Leachates from Pilot-
Scale Landfill Cells
TIME SINCE LEACHATE RECYCLE BEGAN, days
Figure 11. Gas Production and Composition from the
Sealed ?ilot-Scale Landfill Cp.ll
292
-------
comitant decline in pH, gas production in
the sealed cell began to increase and
accelerate as environmental conditions
became more favorable for the growth and
proliferation of the CH formers. Accord-
ingly, gas production increased commen-
surate with the reduction in volatile acids
and increase in pH. Whereas, during
periods of volatile acid accumulation,
little methane was formed, soon thereafter,
gas production accelerated to reach a high
of 639 liters per day with a CH, content
of 57% normalized to about 60% as indicated
on Figures 11 and 12. This period of
accelerated gas production coincides with
the period of most rapid stabilization and
although gas production was still being
measured at the end of the report period,
it had diminished to about 10 to 20 liters
per day. Consequently, the greatest
majority of gas production from the readily
available organic pollutants in the leach-
ate had been completed during the rela-
tively short period of about three months
when conditions favoring CH, production
were most optimum. These optimum con-
ditions are also reflected by ORP measure-
ments (Figure 12) and, although not as
negative as generally reported as neces-
sary for most efficient CH, production ,_,
during anaerobic biological stabilization ,
the trend is indicative of requisite
negative values and probably were not more
so due to sampling difficulties associated
with the unavoidable exposure of samples
to oxygen (air) during sampling and
analysis.
Finally, since dilution consequenced
by the addition of rainfall or water
equivalent to the two cells would result
in some dilution of pollutant concentra-
tions, a conservative constituent could
be chosen to reflect the differences in
moisture accumulation in the open cell
which was reduced by evaporation oppor-
tunities and that amount accumulated in the
sealed cell where evaporation was dis-
allowed. Inspection of Figure 13 provides
some indication of this difference of
accumulated moisture between the two cells
at the end of the report period. Accord-
ingly, concentrations of chloride in the
open cell, where some moisture was lost to
evaporation, are higher than in the sealed
cell where more dilution capacity is
available. Collectively, these results
indicate that between 20 to 30 percent of
the rainfall incident on the open cell
during the report period was lost due to
evaporation. The relative degree of
dilution afforded by that amount of rain-
fall thereby contributing to the accumu-
lated quantity of leachate has important
ramifications with respect to actual
masses of materials contained in the
leachates. For instance, the chloride
concentration exposed to a clay contain-
ment liner is important to prediction of
the rate of its migration into the sur-
rounding environment particularly if it is
used as a tracer and/or quality standard.
In these experiments, the chloride con-
centration diluted by water equivalent to
incident-rainfall was about 325 mg/£; with
the indicated evaporation, this concentra-
tion increased to about 410 mg/£.
SUMMARY AND CONCLUSIONS
Continuing research investigations
with pilot-scale landfill cells and
leachate containment, collection and
recycle have supported the results of
previous work establishing the advantages
of such a landfill management option in
promoting more rapid and predictable
stablization of readily available organic
constituents with concomitant increased
rates of gas production. Decreasing the
time for such stabilization to a matter
of months rather than years provides
attractive opportunities for energy
recovery as well as rapid realization of
potentials for land reclamation and/or
ultimate use without the uncertainities
attendant with present landfill manage-
ment practices. The data presented herein
should better enable the engineer and
scientist to consider leachate recycle
as one option for better design, operation
and control of landfill disposal of solid
waste with respect to practicability,
economics and safeguards against environ-
mental impairment.
293
-------
O O
2 00
250
500
TIME SINCE LEACHATE RECYCLE BEGAN, d.yi
Figure 12. Normalized Gas Production and Oxidation-
Reduction Potential of Leachate from the
Sealed Pilot-Scale Landfill Cell
OPEN CELL
SEALED CELL
€0 120 180 240 300 360 420 480
TIME SINCE LEACHATE RECYCLE BEGAN, diyt
Figure 13. Chloride Concentrations in Leachates from
Pilot-Scale Landfill Cells
294
-------
ACKNOWLEDGEMENT
This research was sponsored jointly
by Georgia Tech and the U.S. Environmental
Protection Agency under EPA research grant
R-803953.
REFERENCES
1. Pohland, F. G., "Sanitary Landfill
Stabilization with Leachate Recycle
and Residual Treatment," Environ-
mental Protection Technology Series,
EPA-600/2-75-043, October 1975, 105 p.
2. Chian, E. S. K. and DeWalle, F. B.,
"Evaluation of Leachate Treatment,
Volume I: Characterization of
Leachate," Environmental Protection
Technology Series, EPA-600/2-77-186a,
September 1977, 209 p.
3. Chian, E. S. K. and DeWalle, F. B.,
"Evaluation of Leachate Treatment,
Volume II: Biological and Physical-
Chemical Processes," Environmental
Protection Technology Series, EPA-
600/2-77-186b, November 1977, 244 p.
4. "Standard Methods for the Examination
of Water and Wastewater," 14th
Edition, American Public Health
Association, 1975, 1193 p.
5. Pohland, F. G. and Ghosh, S.,
"Developments in Anaerobic Treatment
Processes," Biotechnology and Bio-
engineering, Symp. No. 2, 85, (1971).
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LEACHATE TREATMENT SCHEMES - RESEARCH APPROACH
Donald S. Mavinic, Ph.D., P.Eng.
Associate Professor of Civil Engineering
University of British Columbia
Vancouver, Canada
ABSTRACT
Leachates are produced when surface and/or groundwater pass through layers of
refuse in a landfill site and become contaminated. If these leachates enter a nearby
receiving water, a serious water quality problem may result, with potential for fish
kills. It is now generally accepted (and law in some areas) that landfill leachates
and their effects be controlled, primarily through collection and treatment of such.
The purpose of this paper is to provide a brief overview of the approach to and
research results, to date, of a comprehensive long-term, solid waste disposal/leachate
treatability study; this project has been underway at the University of British Columbia,
since 1971, and is under the direction of personnel in the Environmental Engineering
Group of the Department of Civil Engineering. The approach to variable-strength, leachate
treatment, brief summaries of several of the research projects completed to date (or
about to be) and preliminary information on scale-up to on-site lagoon treatment of an
insitu leachate, are presented in this manuscript. Topics requiring further investiga-
tions are also outlined.
INTRODUCTION
Sanitary landfills still remain the
most popular method of solid waste dis-
posal. However, one of the major problems
presented by landfills, particularly in
high precipitation climates, such as the
Pacific Northwest, is the production of
leachate. These leachates are produced
as surface and/or groundwater pass through
layers of refuse in a landfill site and
become contaminated. If this leachate
enters a nearly receiving water, a serious
pollution problem may result, with a
potential for fish kills. The magnitude
of such pollution depends on a number of
factors, including strength and quantity
of leachate produced, as well as the
dilution being afforded by the receiving
water. The former, in turn, depend on a
number of variables, including composition
of the refuse, age and hydrogeology of the
site, and of course, the climate.
Various adverse environmental effects
due to leachates have been well documented
in the literature (1,2,3). Although
leachate composition varies widely, it is
often classified as a high strength waste-
water, that is, the levels of such waste-
water parameters as BOD, COD, suspended
solids, and turbidity are many times
greater than those found in municipal
wastewater. Additional characteristics
such as low dissolved oxygen, low pH,
and a spectrum of toxic chemicals and
metallic ions are quite commonplace.
Table 1 illustrates the observed variabil-
ity of leachate strength and composition
(1).
It is now generally accepted (and
law, in some areas) that landfill leachates
and their effects be controlled primarily
through collection and treatment of such.
This concept is being applied to both
existing fills and proposed sites. Treat-
ment of leachates might include on-site
schemes, discharge to an existing munici-
pal sewer line (with downstream combined
treatment) or even separate on-site
storage and periodic haul ing to the near-
est treatment plant.
296
-------
A number of factors are involved in
this decision making process, including
of course, proven treatment technology
for a leachate-type waste. The latter, in
turn, is currently the subject of exten-
sive on-going research in the water pollu-
tion control field. This paper is an
attempt to summarize the approach and
results (to date) of part of a long-term
solid waste disposal/leachate treatability
research study; this project has been
underway since 1971 at the University of
British Columbia, under the direction
of personnel in the Environmental Engineer-
ing Group. The initiator and overall
coordinator of this project is Dr. R.D.
Cameron of the Department of Civil Engin-
eering.
BRIEF PROJECT HISTORY AND RATIONALE
(i) Solid Waste Disposal Study
As indicated above, this study is a
long-term one and is now in its eighth
year of operation. It is solely under
the direction of R.D. Cameron and only
remotely involves this author. Although
the number of personnel associated with
this particular project has fluctuated
over the years, currently, the support
staff includes four full-time technicians,
one full-time and one half-time Research
Associates. In addition, this project is
backed up by the finest available instru-
mentation.
The purpose of this on-going program
is to characterize landfill leachates
and monitor variations in their composi-
tion with time, precipitation rate, cover
material and other parameters. This
study is being carried out on existing
landfills and a battery of special
lysimeters. A total of thirty-nine various
sized lysimeters are currently in operation,
the largest of which are outlined in Table
2. A major part of this study involves
thorough examination of co-disposal of
industrial and municipal wastes, including
so-called "toxic and hazardous" compounds.
Extensive toxicity studies are also being
carried out. Interested readers are urged
to contact the principle investigator
directly for further details and informa-
tion on this aspect of the project.
(ii) Approach to Leachate Treatability
The Pacific Northwest, including the
province of British Columbia, is quite
famous for its high levels of precipitation.
This is particularly true for the City of
Vancouver and the surrounding areas.
This area is also quite famous for its
fishing industry, in particular the
commercial salmon fishing industry. The
latter is worth millions of dollars
annually to both Canadian and U.S. fisher-
men.
Considering these two facts and the
extensive use of landfills for disposal
of solid wastes, one quickly realizes
that a major problem exists - the
production of leachates of varying
strengths and composition and its poten-
tial for serious receiving water pollution
and fish kill. Because of today's general
environmental awareness and concern, as
well as stricter pollution control laws,
governing both discharge and receiving
water quality, the collection and treat-
ment of leachates throughout the province
is now an accepted fact.
Because of the nature and complexity
of the problem and the lack, in literature,
of convincing and proven treatment tech-
nology for such an unusual waste (espec-
ially high-strength versions), the research
approach undertaken by this author and his
colleagues involves several comprehensive
and deliberate steps. The approach to
developing viable treatment methodology
is being carried out as follows:
(a) The leachate sources are both
lysimeters as described above, and existing
landfill sites in the Vancouver area. In
this manner, a cross-section of leachate
composition and strength can be obtained,
with a goal toward simulating the progres-
sion of landfills from young to old sites.
In addition, treating the leachate "as is",
whether exceptionally strong or weak,
injects a distinct note of realism to the
project, i.e. field conditions.
(b) Examination' of a complete cross-
section of possible treatment schemes,
although formidable in concept, is
imperative. In a sense, a "shot-gun"
approach has been used with a goal toward
narrowing down the choice(s) . The latter,
in turn, would be based on proven effec-
tiveness, viability and cost-effectiveness,
in conjunction with on-site treatment or
combined municipal-leachate treatment.
The scope of research projects includes
297
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aerobic-biological, anaerobic-biological,
chemical/physio-chemical, joint biological-
chemical, and other more exotic treatment
schemes.
(c) These research projects are being
undertaken at the laboratory or bench-
scale level for the time being. Once the
treatment effectiveness has been proven at
this level and the field of choice, so to
speak, has been narrowed down, scale-up
to pilot-plant or full-scale will be
examined in conjunction with (d) below.
(d) Pending successful bench-scale treat-
ment of any one particular leachate,
optimization is planned. This is to be
carried out in connection with a demonstra-
tion pilot-plant or integrated treatment
scheme in the field, should time and/or
funding be a critical factor. Under
extended circumstances, optimization and
prediction for scale-up are to be performed
in the laboratory.
(e) The project scope not only includes
the personnel within the Environmental
Engineering Group at the University, but
invites municipal, provincial and federal
participation and working assistance. The
concept of "team approach", in an on-going
study, is of vital concern to the momentum
of this program.
Considering the aforementioned points,
the following section provides a synopsis
of some of the "leachate treatment schemes"
examined to date. In some instances, the
projects have been completed and the
results fully or partially documented in
the literature; in other cases, the work
has just been completed, or is about to
be, and only preliminary results are
presented.
SUMMARY OF TREATMENT SCHEMES
(i) Project Title: Physio-Chemical Treat-
ment of a High-Strength, Sanitary
Landfill Leachate
Summary
Preliminary results from this project
have been presented elsewhere (4). The
entire study is now in the final write-up
stage and further results will shortly be
available.
The research described here-in was
aimed at developing a physical-chemical
treatment process for a strong, landfill
leachate, such that the effluent might
lend itself to controlled discharge to a
biological treatment system or, if
necessary, to a natural receiving water.
The lysimeter-generated leachate composi-
tion is shown in Table 3.
Preliminary screening, using a
Placket-Burman two-level, fractional
factorial design (4), indicated that only
lime, alum, ferric sulphate, ozone and
synthetic polymers, individually and in
combinations might be significant treat-
ment reagents, out of a possible 12
variables tested; however, subsequent
work demonstrated only lime and ozone to
be significantly effective in treating the
raw leachate. Ozone was applied via a
specially designed, contacting system
(described elsewhere (4)) while all
chemical and physical reagents, including
lime, were tested in conventional jar-
testing apparati.
The results essentially indicated that
lime was quite effective in removing many
of the monitored pollutants, with "best
treatment" dosages at approximately
2350 mg/L. Ozone was mainly effective
only after 100 mg/L had been applied.
The leachate was found to have a "consti-
tuent ordered" ozone demand that must be
satisfied before any other pollutant is
significantly removed. This demand was
primarily due to the dissolved organic
content of the waste. Best treatment was
considered in the context of cost-
effectiveness, not necessarily maximum
applied dosages.
The combination of lime and ozone, in
specific concentration ranges, was found
to effectively remove or reduce many of
the metallic ions, adjust pH, and even
disinfect this high-strength leachate.
Colour and turbidity were dramatically
reduced - however, organic carbon and
COD reduction were limited, essentially
peaking at 48% and 34% respectively, in
the context of "best treatment". It was
also recognized that the sludge produced
in this physical-chemical treatment process
could pose additional problems, both in
treatment and disposal.
(ii) Project Title: Treatment of a Com-
plex Landfill Leachate With Peat
298
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Summary
All aspects of this research project
have been completed. The final results
have been published elsewhere (5). The
basis for this project was previous work
by Lidkea (6) and Tinh et al. (7).
The aim of this study was to use cheap,
locally-available peat as a treatment
scheme for landfill leachates, since some
of British Columbia's largest landfills
(i.e. Vancouver's Burns Bog Landfill) are
located on peat bogs. The leachate tested
was collected from this local landfill
site and the composition is shown in Table
4.
This study incorporated the passage
of leachate through plexiglass columns
filled with an amorphous-granular peat.
Preliminary adjustment of pH showed that
reducing the pH downward to 4.8 dramatically
reduced the metal adsorption capacity;
however, upon increasing the pH to 8.4,
the metal removal was significantly
increased, owing to the filtration of
precipitated metals. The best adsorption
of metals seemed to occur at the "natural"
pH of 7.1.
In this work, manganese was found to
be the limiting pollutant. At the 0.05
mg/L maximum acceptable concentration
allowed by the British Columbia Pollution
Control Branch (8), 94% of the total
metals were removed, thus requiring 159 kg
(350 Ib) of peat per 1000 litres of
leachate. Resting the peat for 1 month
did not significantly increase the removal
capacity.
This research project also demon-
strated that desorption of some contamin-
ants occurred when water was percolated
through the peat. The desorption-test
effluent was not toxic to fish, but iron,
lead and COD exceeded acceptable values (8).
Chemical pre-treatment of the leachate,
using lime and ferric chloride, did achieve
significant iron, manganese and calcium
removals; however, chemical pre-treatment,
followed by peat adsorption, offered no
advantages, other than reducing toxicity
to fish. Therefore, peat treatment alone
was quite effective in reducing leachate
contaminant concentrations to a level that
was non-toxic to fish (rainbow trout).
Table 5 summarizes the overall findings
of this study (5).
(iii) Project Title: Treatability of
Leachate From a Sanitary Landfill
By Anaerobic Digestion
Summary
This research project was successfully
completed in 1974 and the final results
have been published elsewhere (9) . A
synopsis is presented herein.
The study investigated the possibility
of reducing large amounts of oxygen demand-
ing material in a high-strength leachate
through the process of anaerobic digestion,
without any prior removal of heavy metals.
This work also included a study of the
effects of varying detention times on
process performance and leachate character-
istics. The digesters employed were of
14 litres capacity and were operated at
35°C.
The strength of the leachate was
such that influent BOD,- values ranged
from 11,000 - 16,000 mg/L - nevertheless,
BOD5 removals ranged from 80 to 96 percent
over detention times of 5 to 20 days.
Similarly COD removals ranged from 65 to
79 percent for influent values of 23,000
to 33,000 mg/L.
The leachate feed also contained a
variety of metals, including aluminum,
cadmium, chromium, copper, lead, mercury,
nickel and zinc - zinc exhibited the high-
est influent concentration at 65 mg/L.
Despite the presence of these metals, the
anaerobic digestion process seemed to
function consistently. Many of these
metals associated themselves almost
completely with the sludge portion of the
effluent.
Gas production, in this study, was
monitored on the basis of BOD and COD
destroyed - 11.9 to 15.0 cubic feet of
total gas was produced per pound of BODj
destroyed. This digester gas contained
68 to 76 percent methane, with the
percentage decreasing with increased
detention time. On the basis of COD, 5.8
to 6.8 cubic feet of methane was produced
per pound of COD destroyed. (Note: cu ft/lb
x 0.0624 = m3/kg).
Despite reasonably good treatment
efficiency at detention times up to 20
days, residual 6005 values ranged from 400
to 3000 mg/L - thus, further treatment
299
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would obviously be mandatory to meet
appropriate discharge levels. Settling
the effluent for one half hour reduced
these residuals by 13 to 57 percent.
(iv) Project Title - Aerobic Biostabili-
zation of a High-Strength, Landfill
Leachate
Summary
This project was completed in 1976
and was the first in an on-going series
of aerobic, biotreatment studies. The
results have been widely published and
comprehensive data can be found elsewhere
(10,11,12) - only a brief overview is
presented herein.
This study concerned itself with
treating a high-strength leachate (lysi-
meter generated) by aerobic, biological
methods, without any prior removal of the
heavy metals or toxic substances contained
in that leachate. The effect of varying
sludge age was also investigated and the
distribution of the heavy metals in both
the settled sludge and effluent was
examined.
The digesters employed in this project
and all subsequent studies were complete-
mix, 10-litre volume units, such as shown
in Figure 1. Similarly, the leachate feed
for all aerobic studies closely resembled
the composition shown in Table 6. All
biological reactors were operated on a
"fill and draw" basis, from start to steady
state conditions. This biotreatment study
was performed at room temperature (21° -
25°C) and at conventional BOD5:N:P ratios
of approximately 100:5:1.
Using high MLVSS concentrations, 8,000
to 16,000 mg/L, with a combination of air
and mechanical mixing to control foaming,
stable digester operation was maintained
with sludge ages ranging from 10 to 60
days. Table 7 summarizes the overall
performance of the digesters. For
influent COD concentrations averaging
48,000 mg/L, settled effluent COD removal
ranged from 96.0 to 99.2%, over a sludge
age range of 10 to 60 days. Mixed liquor
COD removals were correspondingly 51 to
76 percent. Similar treatment efficiencies
were obtained for the BOD^ results. Just
increasing the sludge age from 10 to 20
days showed significant improvement in
effluent quality. Settling was complete
after 2 hours.
The leachate feed also contained a
variety of metals in varying concentrations
- iron exhibited the highest influent con-
centration at close to 1000 ppm. Most of
these metals were almost completely
removed by the settling biofloc; others
were associated with the sludge solids to
a lesser extent. Overall metal removals
were as follows: aluminum, cadmium,
calcium, chromium, iron, manganese and
zinc - >95%; lead - average of 85%;
nickel - average of 77%; magnesium -
average of 60%; and potassium (with sodium)
- average of 12%.
In this study, it was also observed
that for the most part there existed a
very predictable pattern of decreasing
metal concentrations in the final effluent
with increasing sludge age. At the same
time, a drop in steady-state, mixed liquor
metal concentrations was observed with
increasing sludge age, despite the fact
that corresponding MLVSS levels were also
dropping. The indication is that sludge
age or loading rate may play a more sig-
nificant role than reactor solids levels
in controlling metal concentrations. It
is also recognized that since most of the
metals were concentrated in the sludge,
an additional problem has been created,
with respect to further treatment and
disposal of this sludge.
Analysis of the kinetic parameters
in this study indicated that there was
inhibition of the biological processes
responsible for the removal of oxygen
demanding material in this leachate -
probably due to a combination of high metal
concentration and exotic organic compounds.
A recommendation for "best treatment" of
this leachate (or any similar waste) called
for a minimum sludge age of 20 days and
a food to micro-organism ratio under 0.15
kg BOD5/kg MLVSS/day.
(v) Project Title: Temperature Effects
on Two-Stage, Aerobic Bio-Treatment
of Leachate
Summary
This research project has just recent-
ly been terminated. To date, only pre-
liminary data analysis has been completed
- final results will be available, in
report form, in early 1979 (13).
300
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The aims of this study were threefold:
(a) two-stage biological treatment of a
high-strength leachate with the second
reactor acting as a polishing step,
(b) determination of overall effects on
both reactors of a gradual temperature
drop, and
(c) attempt to optimize the two-stage
system under the varying conditions
of temperature and sludge age.
Again, in this study, 10-litre volume
reactors were employed and operated on a
fill-and-draw basis under steady-state
conditions. The mixed liquor was thorough-
ly mixed and aerated. Nutrient loading
was slightly in excess of BOD5:N:P=100:5:1.
Sludge ages of 6,9, and 20 days were used
in the first stage reactors, while the
polishing reactors were operated at 6,10,
12 and 20 days. The reactors were started
up and operated at room temperature (23-
25°C) and then subsequently exposed to
operating temperatures of 16°C and 9°C.
The leachate was lysimeter-generated and
was characterized by COD and BODg values
of 19,000 mg/L and 14,000 mg/L respective-
ly; in addition, it contained a spectrum
of metals (eg. iron at 1225 mg/L) and
total solids over 10,000 mg/L.
Preliminary data analysis has revealed
some interesting, and in certain cases,
unexpected results. The removal of organic
material in the first stage reactors was
exceptionally good, with better than 99
percent BOD^ and 95 percent COD removals
being achieved. These results held true
for most combinations of sludge age and
temperatures tested. As a result of low,
residual concentrations of biodegradable
organics in the first-stage effluent, the
polishing reactors were viable only at 9°C,
the lowest temperature investigated. At
this temperature and sludge ages examined,
the polishing reactors further removed an
average 80 percent of the residual 6005
and 30-60 percent of the COD. Second
stage, steady-state MLVSS levels ranged
from 150-400 mg/L only, while the first-
stage units stabilized at MLVSS values of
4000 to 6000 mg/L, depending on sludge age.
First-stage metal removal was 90 per-
cent or better for most of the nine metals
monitored. Nickel and magnesium, however,
experienced only an average 50% reduction.
The polishing stage further reduced
residual levels of manganese, iron and zinc
while additional removal of the other metals
was insignificant. This latter observation
might be partially explained by the initial
low concentrations of these metals in the
first-stage effluent.
For the temperature ranges studied,
the performance of the reactors, both in
terms of organic and metal removal, was
not significantly effected as long as the
temperature adjustment was gradual. Only
at 9°C was there indication of reactor
instability, especially at the lower sludge
ages. It was noted, however, that the
settling characteristics of the mixed-
liquor were highly variable, with a combin-
ation of higher sludge age and higher
temperature producing a better settling
effluent. At the low sludge ages and
operating temperatures, mixed-liquor
settling "was slow and consistently produced
highly-turbid effluent (SS ^ 400 mg/L).
Microscopic examination of the mixed-liquor
revealed a network of branching, filament-
ous growth and a near absence of rotifers.
In addition, some bacteria remained dis-
persed while others tended to form inte-
grated, bacterial clumps.
(vi) Project Title: Operating Performance
of Combined Biological-Chemical,
Leachate Treatment Systems
Summary
This study was carried out in parallel
to Project (v) and has also just been
completed. The final report will be
available in early 1979 (14).
This research project investigated the
possibility of treating a high-strength,
leachate with an aerobic, biological system
followed by a lime-polishing step. Also
investigated were the effects of varying
temperature and sludge age, both separately
and in combination", as well as lime dosages.
10-litre volume reactors were once
again employed and operated on a daily
fill-and-draw basis to steady-state condi-
tions . Nutrient loadings were maintained
at approximately 6005:N:P = 100:5:1. The
leachate feed was similar to that employed
in Project (v). Daily effluents being
generated (after settling and/or filtering)
were collected and properly stored for use
in the polishing step. The investigation
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was carried out in two steps - a "tempera-
ture reduction phase, TRP" and a "cold-
temperature phase, CTP". During the TRP
portion, sludge ages of 25 and 15 days
were employed in combination with tempera-
tures of 24°C, 16°C and 9°C. In the CTP
study, the operating temperature was low-
ered to 5°C and additional units of 12,9
and 6 day sludge age were adopted. This
approach (in combination with the Project
(v) work) thus provided a cross-section of
operating possibilities for a single-stage
biotreatment process, independent of the
polishing step.
The lime-polishing step was performed
under the Standard Jar Test procedure. To
ensure uniformity, no lime testing was
carried out until enough first stage
effluent was collected to cover the entire
second-stage testing schedule. Lime
additions ranged from 100 mg/L to 1600 mg/L
and were applied only to those effluents
requiring further treatment (via prior
analysis and examination of local pollution
control objectives) (8).
Data analysis, to date, has revealed
some interesting results. BODg and COD
removal efficiencies, during the TRP por-
tion of this project, were exceptionally
good - essentially better than 99% and 97%
respectively, for both the filtered and
settled effluents. Similarly, metal re-
ductions were better than 90% for most of
the metals monitored (eg. influent iron
greater than 1000 mg/L). Lowering the
operating temperature for the sludge ages
investigated seemed to offer no particular
operational problems - as a result, lime-
polishing was determined as being unneces-
sary for many of the TRP effluents.
During the CTP portion of this work,
reactor instability was observed, particu-
larly at the lower sludge ages. Reactor
failure was achieved at a combination of
5 C and 6-day sludge age. Lime-polishing
was performed on both settled and filtered
effluents from the remaining (and viable)
25,15,12, and 9 day units.
In most cases, the second stage or
lime-polishing step consistently produced
final effluents that were more than accept-
able in meeting local discharge guidelines
- in some cases even as low as 100 mg/L of
lime additions. Further reduction in
levels of organics, solids and metals were
significant. However, residual organic
and metal removals were found to be highly
dependent on final pH and initial solids
levels, with both influencing the level
of metal precipitation achieved and quality
of settling.
Again, mixed liquor settling proved
highly variable, with progressively poor
settling as operating temperatures and
sludge ages decreased. Increasing the
allowable settling time seemed to offer no
particular advantages in these circum-
stances .
(vii) Project Title: Nutrient Require-
ments for Biostabilization of a
Landfill Leachate
Summary
This project was an immediate follow-
up study to the work of Uloth (10). The
research has been completed and a final
report is in progress (15).
This study investigated the nitrogen
and phosphorus requirements of aerobic
microorganisms treating a high-strength
leachate, both by itself and in combination
with domestic sewage (primary effluent).
Special emphasis was placed on the
efficiency of metal removal as a function
of nutrient loading.
In the first series of experiments,
the nutrient loading was varied in a set
of biological reactors having a 20-day
sludge age, operating at room temperatures
(22-24°C), and fed with a high-strength
leachate (as described previously). The
BOD5:N:P ratio was varied from 100:3.19:
0.12 to 100:5:1.1. The most effective
overall treatment was achieved with a
loading of 100:3.19:1.11, as shown in
Table 8. When the nutrient loading was
increased or decreased from this level,
there was a consistent increase in 3005,
suspended solids and metal concentrations
in the treated effluent. In addition, at
nutrient loadings below 100:3.19:1.11,
mixed liquor sludge bulking was prevalent.
In the second series of experiments,
the leachate feed was combined with domes-
tic sewage, in proportions varying from
0 to 20% (vol. leachate)/(vol. leachate
plus sewage). No additional nutrients
were added to the reactors - the 6005:N:P
ratio varied from 100:24:4.3 to 100:3.62:
0.12. The end result of this study was
302
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very effective treatment of all combined
wastewaters. There was no corresponding
increase in BOD5 or metal concentrations
in the treated effluent when a higher
proportion of leachate was added to the
reactors. The sludge did not bulk, even
though the ratio dropped to 100:3.62:0.12.
As a result of this study, it appears
that, if treating a similar leachate (or
other waste) with a 20-day reactor or
aerated lagoon, the required nutrient
loading could be significantly reduced
below the recommended 8005:N:P ratio of
100:5:1. At low volumetric BOD loadings
of approximately 10 Ib BOD5 per day per
1000 cu ft, a low nutrient loading of
100:3.62:0.12 did not seem to adversely
affect treatment efficiency. However, at
a higher loading of 60 Ib BOD5 per day
per 1000 cu ft, the minimum nutrient load-
ing needed was 100:3.19:0.5. Therefore,
an increase in volumetric loading of high-
strength leachate required a corresponding
increase in phosphorus input.
In addition, for the units that exhib-
ited sludge bulking and poor settling under
low nutrient loading conditions, a high
level of suspended solids prevailed in the
final effluent; because most of the metals
were bound to these solids, final effluent
metal concentrations were also dramatically
increased.
(viii) Project Title: Preliminary Design,
Richmond, B.C. Landfill
Summary
(This project is under the direction
of R.D. Cameron).
A local landfill, receiving about 500
tons of municipal and commercial refuse
per day, has been discharging leachate to
a nearby river at an estimated rate of
one million Imp gal per day. Leachate pro-
duced from the 310 acre active site is a
combination of essentially all of the annual
precipitation (40 in per year) plus river
water entering at high tide. Having
recently been brought under permit, the
landfill operators are faced with having to
treat the existing leachate, as well as
that which will be produced during and
after filling the remaining 350 acres.
Preliminary data (16) showed that the
approximate reductions shown in Table 9
were required to meet effluent standards.
With the expected site expansion, it was
concluded that aerobic biological treatment,
followed by activated carbon adsorption,
and then followed by either reverse osmosis
or ion exchange, would be the most feasible
and flexible treatment method.
It was also expected that, with a
proper collection system, less leachate
dilution will be occurring with time; thus,
leachate strength will increase. For this
reason a leachate spring near the active
face was chosen as the collection site
for a relatively high-strength leachate.
Table 10 shows the parameters exceeding
effluent standards.
Semi-batch, aerated lagoon laboratory
studies were conducted at 2, 3, 5, 7 and
10 day solids detention times. Nutrients
were added to achieve a BOD:N:P ratio of
100:5:1. The results from this work are
summarized in Table 11 (16). The higher
strength second leachate sample also
responded well to treatment with a BOD
removal efficiency of 99.4% at 10 day
solids detention time.
With the exception of iron, sulphate
and boron, all contaminants were reduced
to less than effluent standards. The
effluent from treatment of leachate sample
I was non-toxic, while that from sample II
had a 96 h - LC50 of 72% by volume.
Insufficient leachate treatment
effluent volume was available for complete
activated carbon treatment. The few
tests conducted, however, showed that iron
could be reduced to less than effluent
standards, using about 2% to 3 times the
carbon normally required for tertiary
treatment. Overall COD removal efficiency
was increased to 99.4%.
Small-scale, sludge-leaching tests
were also performed to evaluate the
possibility of placing the aerobically
produced sludge back into the landfill.
For just the metals, the percentage leached
at a leaching volume of 212 inL per gm of
dry sludge solids were:
Zn < 0% (adsorbed from tap water)
Mn 0.4%
Fe 4.2%
Al 4.8%
Cr 14.5%
Subsequent to the research, the land-
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fill operators called for a preliminary
design. With the excellent BOD removal and
good sludge settleability found in the
laboratory study, enough confidence had
been generated to recommend going to a
full-scale facility without an intermediate
pilot plant study. However, the rate of
leachate production is expected to be such
that the initial stages of the full scale
facility will serve as a pilot study for
subsequent stages if necessary. Thus, some
reduction in leachate volume will probably
occur initially, due to proposed changes
in the leachate collection system. Within
six or seven years, leachate strength and
flow will peak at an expected BOD5 of 5000
mg/L and a 1.3 Imp mgd flow rate.
Preliminary design will provide for a
five day sludge age at a flow of 1 Imp mgd.
While BOD removal efficiency will be some-
what reduced due to cooler field tempera-
ture, this will be balanced by both a flow
reduction as well as a longer than neces-
sary detention time. The aeration basin
will be of the complete mix type with
provision for additional units, if neces-
sary; also provided will be separate
clarifiers.
It is also expected that "tees" will
be provided from the sludge lines, so that
sludge recycle can be practised. Sufficient
space will be allotted for polymer or
chemical addition, before settling, although
this is not considered to be likely. Space
will also be provided for activated carbon
treatment (or something else) of the efflu-
ent.
Preliminary agreement has been reached
with the regulatory agency such that, if
all other parameters meet the effluent
guidelines, the sulphate, iron and boron
standards will be waived. All sludge will
be returned to the landfill for disposal
without dewatering.
This flexible design, if installed,
will provide valuable operating data which
can then be used to evaluate the field
kinetic coefficients. If the optimistic
design criteria are not suitable for the
expected increased loading, sufficient
lead time will be available to add to the
initial facility. The facility will also
be designed so that, for the aeration
basins at least, stages can be removed as
the site ages and the space utilized for
the ultimate site development.
Two major questions are currently
unanswered - one will be answered during
field operation while the other will not.
The first question is whether or not metal
leaching from the returned sludge will
be sufficient to cause a plant overload.
The second question relates to where the
sludge will be disposed of after the land-
fill operation has ceased. This will
likely be a problem for ten to fifteen
years and is one which has not yet been
addressed.
SUMMARY AND CONCLUSIONS
As discussed in the preceeding pages,
a broad spectrum of possible leachate
treatment schemes has been examined and
the resulting data fully or partially
analyzed. Certainly many of the questions
and uncertainties surrounding leachate
treatment at the start of this long-term
project have been eliminated and the
project scope narrowed down considerably.
However, there are still some treatment
aspects requiring further examination as a
result of those projects completed to date.
Further bench-scale research is therefore
planned,especially in the areas of "treat-
ment sludge", combined treatment and
effluent polishing. Although these areas
do need further investigation, preliminary
optimization and scale-up is not too un-
realistic at this time, depending on the
characteristics of the leachate and circum-
stances in question. To this end, further
work is now in progress.
ACKNOWLEDGEMENTS
The author is indebted to his
colleague, Dr. R.D. Cameron - it is through
much of Bob's efforts that this project was
initiated and is continuing. In addition,
the author is grateful to the technical
staff, especially Mrs. E. McDonald, head
technician, and many graduate students that
have been involved with this study over the
years. Financial support for this continu-
ing project has originated from the Govern-
ment of British Columbia, National Research
Council of Canada, Environment Canada, and
the City of Vancouver.
REFERENCES
1. Cameron, R.D., "The Effects of Solid
Waste Landfill Leachates on Receiving
Water", paper presented at the BCWWA
304
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Conference, Harrison Hot Springs, B.C. 11.
Canada, April 1975.
2. Hughes, G. et al., "Pollution of
Groundwater Due to Municipal Dumps",
Technical Bulletin No. 42, Inland 12.
Water Branch, Dept. Energy, Mines and
Resources, Ottawa, Canada, 1971.
3. Zanoni, A.E., "Groundwater Pollution
from Sanitary Landfills and Refuse
Dump Grounds - A Critical Review",
Dept. Natural Resources, Madison, 13.
Wise., 1971.
4. Bjorkman, V.B. and Mavinic, D.S.,
"Physio-Chemical Treatment of a High-
Strength Leachate", Proceedings of the
32nd Annual Purdue Industrial Waste 14.
Conference, West Lafayette, Indiana,
May, 1977.
5. Cameron, R.D., "Treatment of a Complex
Landfill Leachate With Peat", Can.
Jour. Civil Eng., Vol. 5, No. 1,
March 1978. 15.
6. Lidkea, T.R., "Treatment of Sanitary
Landfill Leachates With Peat", M.A.Sc.
Thesis, Dept. Civil Eng., Univ. of
British Columbia, Vancouver, April,
1974. 16.
7. Tinh, V.Q., et al., "Peat Moss, a
Natural Absorbing Agent for the Treat-
ment of Polluted Water", Can. Mining
and Metallurgical Bulletin, Vol. 64,
No. 707, Ottawa, 1971.
8. B.C. Department of Lands, Forests, and
Water Resources, "Pollution Control
Objectives for Municipal Type Waste
Discharges in British Columbia", Water
Resources Service, Victoria, 1975.
9. Poorman, P.L. and Cameron, R.D.,
"Treatability of Leachate From a San-
itary Landfill By Anaerobic Digestion",
Tech. Report No. 5, Environmental
Engr'g Group, Dept. Civil Engr'g, UBC,
Vancouver, 1974. (Prepared for
Province of British Columbia.)
10. Uloth, V.C. and Mavinic, D.S., "Aerobic
Biostabilization of a High-Strength
Landfill Leachate", Tech. Report No. 7,
Environmental Engr'g Group, Dept. Civil
Engr'g., UBC, Vancouver, 1976. (Pre-
pared for Province of British Columbia.)
Uloth, V.C. and Mavinic, D.S., "Aerobic
Bio-treatment of a High-Strength
Leachate", JEED, ASCE, Vol. 103,
No. 4, August 1977.
Mavinic, D.S. and Uloth, V.C., "Fate
of Heavy Metals in Bio-Treatment of
Leachate", Proceedings of the ASCE
National Conference on Environmental
Engineering, Kansas City, Missouri,
July, 1978.
Zapf-Gilje, R. and Mavinic, D.S.,
"Temperature Effects on Two-Stage,
Aerobic Bio-Treatment of Leachate",
Final Report in progress. Dept. Civil
Engr'g, UBC, Vancouver, April, 1979.
Graham, D.W. and Mavinic, D.S.,
"Operating Performance of Combined
Biological-Chemical, Leachate Treat-
ment Systems", Final Report in
progress, Dept. Civil Engr'g, UBC,
Vancouver, Feb, 1979.
Temoin, P.E. and Mavinic, D.S.,
"Nutrient Requirements for Bio-
stabilization of a Landfill Leachate",
Final Report in progress, Dept. Civil
Engr'g, UBC, Vancouver, March 1979.
Lee, C.J. and Cameron, R.D., "Treat-
ment of a Municipal Landfill Leachate",
Final Report in progress, Dept. Civil
Engr'g, UBC, Vancouver, January 1979.
305'
-------
CO
o
en
Volumetric
graduation
(on masking tape)
Plastic tubing
Oil - free air
Electric motrr
Porous, Glass, Coarse
bubble diffuser
Adjustable screw clamp
Electric motor
driven stirrer
j
Rubber stopper
FIGURE I 'SCHEMATIC OF LABORATORY AEROBIC DIGESTERS
( 10 litre volume units )
-------
TABLE 1
COMPOSITION OF TYPICAL LEACHATES
Parameter
BOD5
COD
Total Carbon
Total Organic Carbon
Total Solids
Total Volatile Solids
Total Dissolved Solids
Acidity
Alkalinity
Aluminum
Arsenic
Barium
Beryllium
Calcium
Cadmium
Chloride
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nitrogen - total
- NH3
Nickel
Phosphorus - total
Potassium
Sodium
Sulphates
Sulphides
Titanium
Vanadium
Zinc
pH
Tannin-like compounds
Colour (chloroplatinate)
Odour
Range of Values
(Landfills and
9 -
0 -
715 -
715 -
1,000 -
1,000 -
0 -
0 -
0 -
0 -
0 -
0 -
0 -
5 -
0 -
34 -
0 -
0 -
0.2 -
0 -
165 -
0.06 -
0 -
0 -
0 -
0 -
0.01 -
0 -
2.8 -
0 -
1 -
0 -
0 -
0 -
0 -
3.7 -
78 -
0 -
not detectable
or Concentrations*
Test Lysimeters)
55,000
90,000
22,350
22,350
45,000
23,157
42,300
9,560
20,900
122
11.6
5.4
0.3
4,000
0.19
2,800
33.4
10
5,500
5.0
15,600
1,400
0.064
0.52
2,406
1,106
0.80
154
3,770
7,700
1,826
0.13
5.0
1.4
1,000
8.5
1,278
12,000
to terrible
*all values except those for pH, colour and odour are in mg/L.
307
-------
TABLE 2
TYPICAL LYSIMETER DETAILS
(one of 16 such units)
(1) Dimensions - 14 feet (4.27 m) deep, 4 feet (1.22 m) in diameter
(2) Cover Material - 2 feet (0.61 m) of hog fuel
(3) Total weight of refuse - 3420 Ib (1549 kg)
(4) Depth of refuse - 8 feet (2.44 m)
(5) Weight (density) before final cover - 884 Ib/cu yd (wet) (523 kg/m )
(6) Simulated Precipitation - 15 inches per year (38.1 cm/yr)
(7) Moisture content - 34.7%
(8) Percentage composition of refuse:
Food waste - 11.8
Garden waste - 9.8
Paper products - 47.6
Cardboard - 5.4
Textiles - 3.6
Wood -4.7
Metals - 8.7
Glass and ceramics - 7.0
Ash, rocks and dirt - 1.4
Total - 100%
TABLE 3
A TYPICAL LEACHATE ANALYSIS FOR PROJECT (i)
pH
Colour
Total Solids
Turbidity
Total Carbon
Organic Carbon
COD
Fe
Zn
Na
K
Ni
Cu
Mn
Cr
Al
Si
Co
5.3
2500 Helige colour units
7140 mg/L
69 Hach Formazin Units
5230 mg/L
5203 mg/L
14,000 mg/L
47 mg/L
12.45 mg/L
188 mg/L
156 mg/L
0.165 mg/L
0.39 mg/L
10.14 mg/L
1.14 mg/L
0.40 mg/L
36.3 mg/L
2.10 mg/L
308
-------
TABLE 4
LEACHATE ANALYSIS - IN SITU SAMPLE FOR PROJECT (ii)
Parameter
PH
Alkalinity (pH = 4.5)
COD
Total residue
Non-filtrable residue
Calcium x
Chloride
Iron
Lead
Magnesium
Manganese
Nitrogen - total Kjeldahl
Phosphorus
Potassium
Sodium
Zinc
BOD5
Acidity (pH = 8.3)
Volatile solids
Fluoride
Nitrogen - ammonia
Sulphate
Tannin-like compounds
Aluminum
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium
Cobalt
Copper
Molybdenum
Nickel
Silicon
Silver
Tin
Titanium
Vanadium
Measurement
7.1
3400
903
4636
134
175
2400
30.3
0.065
126
0.57
494
1.56
600
840
0.43
120
185
1092
0.27
427
5.3
62.4
0.27
0.038
0.08
0.025'
4.5
0.0037
0.053
N.D.
0.024
0.013
0.069
9.80
N.D.
N.D. '
N.D. ~
N.D. -
Notes: N.D. - not detectable. All values except pH as mg/L;
alkalinity and acidity in mg/L as CaCO_.
All metals as total concentrations.
309
-------
TABLE 5
PEAT REQUIREMENTS FOR LEACHATE TREATMENT - PROJECT (ii)
Total dissolved solids
loading (mg/g)
Total metal removal (mg/g)
Peat required (kg (dry) /1000L
leachate)
COD removal (mg/g)
P removal (mg/g)
TKN removal (mg/g)
Non-filtrable residue
removal (mg/g)
Chloride removal (mg/g)
PH
7.1
34.1
12.6
159
5.7
0.01
3.5
0.9
16.3
7.8
16.2
5.0
397
2.4
0.005
1.6
0.4
6.4
8.4
35.3
13.1
159
3.9
0.07
3.0
2.1
15.6
TABLE 6
LEACHATE FEED COMPOSITION FOR PROJECT (iv)
BOD5
COD
Total Carbon
Total Org . Carbon
Total Solids
Tot. Volatile Solids
Tot. Dissolv. Solids
Acidity
Alkalinity
Aluminum
Arsenic
Barium
Beryllium
Boron
Calcium
Tannin-like Cmpds.
PH
- 36,000 mg/L
- 48,000
- 15,400
- 15,389
- 26,600
- 17,800
- 25,700
5,640
7,640
- 41.8
3.6
0.7
trace
- 7.30
- 1,394
- 578
- 5.02
Cadmium
Chloride
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nitrogen - Total
- NH3
Nickel
Phosphorus - total
Potassium
Sodium
Selenium
Sulphates
Zinc
- 0.39 mg/L
- 1,620
- 1.9
- 0.24
- 960
- 1.44
- 310
- 41.0
trace
- 1,080
- 725
- 0.65
- 19.8
- 1,060
- 1,250
- 0.450
- 1,070
- 223
310
-------
TABLE 7
TREATMENT EFFICIENCY AND REACTOR CHARACTERISTICS FOR PROJECT (iv)
Parameter
(all but pH in ppm)
Steady-State MLSS
Concentration
Steady-State MLVSS
Concentration
Effluent Total
Solids
Effluent COD
Effluent BOD5
Effluent Total
Organic Carbon
Effluent Alkalinity
Effluent pH
Digester Sludge Age, 6 (days)
10
24,250
16,100
6,050
1,547
129
683
1,320
8.80
20
22,650
15,100
5,200
594
32
268
1,210
8.73
30
20,175
12,045
5,070
533
59
221
969
8.65
45
20,300
11,880
4,870
428
66
-
728
8.74
60
14,300
8,100
4,450
386
75
-
542
8.60
Leachate
Feed
-
-
26,600
48,000
36,000
15,389
7,640
5.02
TABLE 8
PARTIAL DATA SUMMARY FOR LEACHATE TREATMENT STUDY - PROJECT (vii)
(1) Treated Effluent
(mg/L)
BOD_
S.S.
Chromium
Iron
Lead
Zinc
(2) Nutrient Loading
BOD/N/P
Leachate
Feed
19330
990
0.365
960
0.167
49.5
Reactor
A
82
380
0.050
25.2
O.C11
1.31
100
5.03
1.11
Reactor
B
55
133
0.033
9.72
0.006
0.630
100
3.98
1.11
Reactor
C
36
47
0.035
4.27
0.003
0.295
100
3.19
1.11
Reactor
D
300
1805
0.103
27.3
0.023
2.10
100
3 .98
0.32
Reactor
E
1430
245
0.040
13.5
0.005
0.726
100
3.98
0.12
Reactor
F
560
160
0.033
6.73
0.015
0.543
100
3.19
0.12
311
-------
TABLE 9
LEACHATE STRENGTH REDUCTION REQUIRED FOR PROJECT (viii)
Parameter
BOD5
SS
Sulphate
Iron
Lead
Manganese
Zinc
Toxicity
(96 hr LC50)
Effluent Standard
100 mg/L
100
50
0.30
0.05
0.05
0.50
100%
% Reduction Needed
87
50
75
99.4
50
99
60
80
TABLE 10
LEACHATE COLLECTED FOR PROJECT (viii)
Parameter
BOD
SS
Sulphate
Boron
Iron
Manganese
Zinc
96 hr LCRn
50
Sample 1
1140 mg/L
125
250
5.9
22.4
4.3
1.3
NA
Sample 2
2980 mg/L
NA
83
7.4
1.6
7.8
0.6
4 .2% V/V
TABLE 11
AEROBIC LAGOON TREATMENT OF LEACHATE - PROJECT (viii)
Influent BOD5
Growth yield coef f . - y
Endogenous decay coef f . - b -
ks
k
0_ min. -
{*
BODc removal
COD removal
MLVSS
F/M ratio
Settled effluent SS
1000 mg/L (approx.)
0.59 mg VSS/mg BOD5
0.040 day"1
99 mg/L
4.5 day"1
0.42 days
99.1%
88%
560 mg/L @ 9C = 5 days
0.4 day-1 @ 9C = 5 days
10 - 20 mg/L
312
-------
LEACHATE TREATMENT DEMONSTRATION
Bernard J. Stoll
U.S. Environmental Protection Agency
401 M St. S.W.
Washington, D.C. 20460
ABSTRACT
This paper reports the results of three years of operation of a solid waste landfill
leachate treatment plant. This plant incorporates chemical, physical, and biological
unit processes and was constructed to enable operation in several sequences of unit
processes. The processes include: equalization, lime precipitation, sedimentation,
ammonia stripping, activated sludge, carbon adsorption, and chlorination.
The purpose of this project was to demonstrate the treatment of landfill leachate
at full scale in four treatment sequences. The plant is supplied by an adjacent, lined
landfill which generates about 20,000 gallons per day of leachate high in organic
matter, ammonia, and heavy metals.
Of the treatment sequences demonstrated, that sequence which incorporates
equalization, lime precipitation/clarification, ammonia stripping, activated sludge
treatment, and chlorination (in that order) has been the most effective in achieving
the discharge standards for this wastewater treatment facility. This treatment
sequence has been found capable of meeting the discharge standards except BOD and
lead, which have been occasionally exceeded, and ammonia, which has seldom been
achieved.
BACKGROUND
EPA has been studying the treatment
of landfill leachate, because of the
potential for adverse effect on ground
and surface waters, for several years.
Most investigations were laboratory-scale
or occasionally pilot-scale treatment
systems. In early 1975 the Office of
Solid Waste became aware of initiation of
construction of a leachate treatment
system to serve a lined landfill in
Pennsylvania. That State had awarded an
operating permit for a mixed municipal
solid waste landfill which was to be
constructed above grade, underlain with
and surrounded by a dike covered with a
sprayed asphaltic compound, in 1970.
The permit included a provision re-
quiring leachate treatment and discharge
to the Delaware River at such time as
the dike became filled with leachate
to within two feet of overflowing.
The Delaware River Basin Commission
subsequently (1974) awarded a permit
for discharge of treated leachate from
the landfill to the Delaware River
during the high stream flow months of
December through April in accordance
with the effluent quality criteria
listed in Table 1
Applied Technology Associates was
awarded a demonstration grant in late
1975 to evaluate the efficiency and
economics of full-scale treatment of
landfill leachate at the GROWS
(Geological Reclamation Operations and
Waste Systems, Inc.) landfill, located
in Bucks County near Tullytown,
Pennsylvania. The evaluation was to
comprise two years of full-scale
313
-------
TABLE 1
SUMMARY OF EFFLUENT CRITERIA*
Parameter
Maximum Concentration
mg/liter
BOD5
Ammonia-Nitrogen
Phosphate
Oil and grease
Iron
Zinc
Copper
Cadmium
Lead
Mercury
Chromium
100.0
35.0
20.0
10.0
7.0
0.6
0.2
0.02
0.1
0.01
0.1
*Commonwealth of Pennsylvania Department
of Environmental Resources and Delaware
River Basin Commission.
operation of this leachate treatment
system which incorporated chemical,
physical and biological treatment.
THE SYSTEM
The leachate treatment system
designed to meet the needs of the GROWS
landfill was a modification of a package
type sewage treatment plant. The system
consisted of a flash mixing chamber for
lime addition to influent leachate prior
to introduction to a cylindrical clari-
fication unit. Clarified effluent was
then to be introduced to a prefabricated
aeration/sedimentation unit for activated
sludge biological treatment, prior to
discharge.
In order to determine design parame-
ters for the leachate treatment system,
samples of the landfill leachate were
obtained and used for operation of a
laboratory bench-scale treatment system.
The leachate characteristics upon which
plant design was based are presented in
Table 2. Limited sampling in the early
stages of landfill operation yielded
these characteristics which will be shown
later as having changed dramatically.
The ultimate design flow for this system
was estimated by a water balance at 100 gpm.
During the three years of this
demonstration the original design has
been modified significantly through
addition of two lagoons. The first
lagoon was constructed to serve as an
ammonia stripping pond following lime
addition to the influent leachate.
The second lagoon, added late in the
project, serves as an equalization
pond constructed ahead of the entire
leachate treatment system.
The current facility is shown
schematically for System 1 in Figure 1.
Detention times in the various units are
about 2 days in each of the lagoons, 2
hours in the reactor clarifier, and 6
hours in the aeration chambers at the
design flow of 100 gpm. Since current
flow rates are only about 15 gpm these
detention times should be increased
accordingly.
As a result of award of the demon-
stration grant the facility has been
equipped with a laboratory trailer to
enable prompt analysis of samples to
enable system evaluation and operation.
TABLE 2
DESIGN LEACHATE CHARACTERISTICS
Constituents
Raw Leachate*
BOD5
Sus. Solids
Total Solids
Percent Volatile
PH
Chlorine
Iron, total
Zinc
Chloride
Organic Nitrogen
Nitrate
Sulfate
Copper
Hardness
Alkalinity
Color, standard units
Flow, mgd
Temperature, °F
1500
1500
3000
55
5.5
200
600
10
800
100
20
300
1
800
1100
50
0.144
80
*A11 units are mg/1 except pH, color,
flow, and temperature.
314
-------
FIGURE 1. SCHEMATIC FLOW SYSTEM 1
oo
en
Sludge
Holding — ^_
21 cu m f
Reactor
^j.^^^
35.8 cu m \
\
Landfill
^"
Equalization
Lagoon
950 cu m
V
3
*\
\
/^l
Vv^
i
^
./ Waste Activated Sludge '
N 1
Settling
JJj 1 , Chamber
•« | / 23.7 cu m Chlorine
"^ 1 -1*"
)
/
^
i
r
// ^— 7,6 cu m
Aeration Clia.nib&r r / ^ ^^
75'71 cu m / ' ^ To River
/ or
75. 71 cu m
| Sludg_e_ ,
« H3POA
Ammonia
Lagoon
950
cu m
-------
DISCUSSION
As previously indicated the design
leachate characteristics presented in
Table 2 have been shown to be highly
inaccurate. Over the life of this
project leachate volume and strength
have fluctuated widely but have tended
to increase overall. Table 3 presents
the quality of the raw landfill leachate
for each year of this project and the
average leachate quality, over time.
To further depict the variability of raw
leachate quality Figure 2 is included.
As seen in Figure 2, the COD has varied
from as low as 5000 mg/1 to as high as
50,000 mg/1.
Anyone who has worked with landfill
leachate is familiar with such fluctua-
tions in leachate quality. Elaboration
on this topic is considered appropriate
in this report in that it demonstrates
one of the problems encountered by both
the designer and operator of such a
leachate treatment facility. Since,
as in this case, it is often necessary
to design the leachate treatment system
either at the design stage of the
landfill or in the very early stages of
landfill operation, the designers must
rely upon the literature for "typical"
leachate quality modified by leachate
quality prediction techniques. In this
situation, young landfill leachate and
prediction techniques were inadequate.
From the operator's standpoint
leachate quality variations can cause
serious difficulty in attempting to
automate chemical addition to the
influent raw leachate, such as lime.
Only frequent analysis of influent
leachate and subsequent adjustment of
chemical feed can accomplish the
desired result. Significant variation
in the organic strength of influent
leachate to a biological treatment
element is also a problem, but the
buffering capacity of activated sludge
ameliorates this problem somewhat.
Construction of an equalization lagoon
upstream of the treatment facility was
the "solution" selected to reduce the
degree of quality fluctuation at this
facility.
Construction of this leachate
treatment facility was completed in
late 1975. Start-up attempts were
initially frustrated by freezing
temperatures until Spring of 1976.
Three attempts at establishing an
activated sludge culture by acclima-
tion of waste activated sludge "seed"
from a nearby sewage treatment plant
were unsuccessful. Bench-scale
simulation of the biological unit
process indicated that the landfill
leachate was deficient in phosphorous
and had an excessive ammonia concen-
tration which was thought to be toxic
to the biomass. The phosphorous
deficiency was immediately corrected
by addition of phosphoric acid ahead
of the aeration tanks. In order to
deal with the high concentration of
ammonia, the twin aeration tanks were
modified from parallel to series flow.
In the first tank the pH was raised
to greater than 10 to enable ammonia
stripping by aeration. After several
weeks of operating in this mode, it was
concluded that there was insufficient
surface area for effective ammonia
stripping. This decision led to con-
struction of the first of the two
"add-on" lagoons.
Construction of this lagoon equipped
with a diffused aeration system proved
effective in reducing influent ammonia
concentrations by greater than 50%.
A leachate acclimated biomass was finally
achieved in July 1976. This biomass
was again lost to freezing weather
during the 1977-78 winter and reestab-
lishment of the biomass in the Spring
of 1978 was somewhat less difficult.
As indicated earlier, chemical/
physical followed by activated sludge
treatment was the original treatment
design and the sequence expected to
be the most effective. This sequence
(referred to as System 1) was initiated
on August 1, 1976 (following acclimation
of the activated sludge to leachate)
and evaluated through April 30, 1977.
Operation in the System 1 sequence
involves chemical addition, primarily
lime, to the raw influent leachate to
precipitate dissolved metals and reduce
suspended solids. Following clarifica-
tion the leachate, now at a pH in
excess of 10.5, is introduced into the
aerated ammonia stripping lagoon. The
lagoon effluent is neutralized with
acid, if necessary, and supplemented
316
-------
TABLE 3. LANDFILL LEACHATE CHARACTERISTICS*
Item
Biochemical oxygen demand (5-day)
Chemical oxygen demand
Suspended solids
Dissolved solids
pH
Alkalinity, as CaC03
Hardness, as CaCC>3
Calcium
Magnesium
Phosphate
Ammonia-N
Kj eldahl-N
Sulfate
Chloride
Sodium
Potassium
Cadmium
Chromium
Copper
Iron
Nickel
Lead
Zinc
Mercury
11/15/75-9/1/76
4,460
11,210
1,994
11,190
7.06
5,685
5,116
651
652
2.81
1,966
1,660
114
4,816
1,177
969
0.043
0.158
0.441
245
.531
.524
8.70
.0074
Concentration+
9/1/76-9/1/77
13,000
20,032
549
14,154
6.61
5,620
4,986
894
454
2.61
724
760
683
4,395
1,386
950
0.09
0.43
0.39
378
1.98
0.81
31
.0051
9/1/77-8/31/78
11,359
21,836
1,730
13,181
7.31
4,830
3,135
725
250
2.98
883
611
428
3,101
1,457
968
0.10
0.22
0.32
176
1.27
0.45
11.0
0.012
11/15/75-8/31/78
10,907
18,553
1,044
13,029
6.85
5,404
4,652
818
453
2.74
1,001
984
462
4,240
1,354
961
0.086
0.28
0.39
312
1.55
0.67
21
0.007
*These values represent the arithmetic mean of all raw leachate data.
4A11 units mg/liter except pH.
-------
FIGURE 2. RAW LEACHATE CHEMICAL OXYGEN DEMAND
(Note change in scale on ordinate.)
25
20 -
15 •
10 -
5 -
0 DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV.
1976
50
20 1
10
DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV.
1977
318
-------
with phosphoric acid prior to introduc-
tion into one of the two parallel
activated sludge chambers. Clarified
effluent from the biological system is
either returned to the landfill or
discharged to the Delaware River
depending upon effluent quality and
the time of year. Effluent is
chlorinated before discharge to the
Delaware River.
This same System 1 sequence was
retested in July and August 1978 with
the following modifications:
1. raw leachate was first intro-
duced into an aerated equalization
lagoon,
2. the activated sludge aeration
chambers were operated in series instead
of in parallel, and
3. the flow rate was only about
half that of the previous operating
period (i.e. 10,000 vs 22,000 gpd).
Concurrent evaluation of System 2
also took place during these periods
since the System 2 sequence is chemical/
physical treatment only. The performance
of System 2 is discussed later in this
report.
Table 4 displays the leachate
treatment efficiency of the two operating
periods in the System 1 sequence in
comparison to the discharge standards.
As seen in this table BOD removal
exceeded 99% during the first operating
period but only approached 95% during
the second. Conversely, ammonia removal
during the later period exceeded 99% while
during the earlier period of operation
only 89% ammonia removal was achieved,
on the average. Finally, COD removal
approached 95% during both these
operating periods. No satisfactory
explanation for these variations in
performance has been developed.
Presented in Table 5 are the average
costs of operation and maintenance of
this treatment facility in the System 1
sequence. You will note in this table
that power costs account for nearly
two-thirds of the cost of treatment.
This high power costs reflects the demand
for leachate and effluent pumping and
maintenance of the laboratory in addition
TABLE 5
SYSTEM 1 - OPERATION AND MAINTENANCE COSTS
(8/1/76 - 5/1/77; 7/1/78 - 8/31/78)
Total Flow, gal 5,953,255
Lime, lb/1000 gal 36.43
Sulfuric acid, gal/1000 gal 0.132
Phosphoric acid, gal/1000 gal 0.019
NaOH, gal/1000 gal 0.123
NaOCl, gal/1000 gal 0.151
Costs, $/1000 gal
Power
Lime
H2S04
H3P0.4
NaOH
NaOCl
Total
1.92
1.10
0.10
0.05
0.08
0.11
3.36
to the requirements for actual treatment.
In this treatment process, the aeration
blowers account for the greater energy
consumption. Labor of approximately
20 man-hours per week is not included
in these costs. Please note that costs
presented in this table are the averages
of data collected only for these two
periods of operation.
Leachate treatment in the System 2
sequence was evaluated over a longer
period of time than by any other sequence.
Since System 1 includes System 2, infor-
mation on this chemical/physical treat-
ment sequence was gathered during the
periods of operation in System 1. In
addition, except during the brief periods
of evaluation in the Systems 3 and 4
treatment sequences, evaluation of the
treatability of raw leachate by System 2
was continued.
The System 2 treatment sequence
has essentially been evaluated in three
modes. Since System 2 data gathering
began prior to accilimation of the
activated sludge biomass, some data has
been gathered on the effectiveness of
lime addition to the raw leachate
followed by clarification. The majority
319
-------
TABLE 4. SYSTEM 1* TREATMENT PERFORMANCE AFTER ACCLIMATION OF ACTIVATED SLUDGE
(August 1, 1976 - May 1, 1977; and July 1, 1978 - August 31, 1978)
CO
ro
O
8/1/76 - 5/1/77
Parameter
Sus. Solids
Dis. Solids
COD
BOD5
Alkalinity
Hardness
Magnesium
Calcium
Chloride
Sulfate
Phosphate
Ammonia-N
Kj eldahl-N
Sodium
Potassium
Cadmium
Chromium
Copper
Iron
Nickel
Lead
Zinc
Mercury
Flow, gpd
Influent**
686
13563
18488
12468
5479
5331
499
929
4264
645
2.15
705
748
1310
906
0.08
0.28
0.44
376
1.91
0.82
22
0.006
21034
Concentration
Effluent**
101
5693
939
118
685
1314
107
347
2592
951
13.7
80
102
821
524
0.01
0.07
0.10
3.0
0.76
0.12
0.57
.004
Percent
Removal
97.4
58.0
94.9
99.1
87.5
75.4
78.6
62.6
39.2
88.7
86.4
37.3
42.2
87.5
75.0
77.3
99.2
60.2
85.4
97.4
28.9
Influent**
1655
13091
18505
8143
5262
2504
275
653
8578
178
1.39
1076
1248
872
0.06
0.16
0.20
9.7
0.88
0.30
3.38
0.003
10000
7/1/78 - 8/31/78
Concentration
Effluent**
478
7244
1008
464
1496
1456
105
113
2254
836
17.2
6.3
1145
743
0.04
0.04
0.16
0.71
0.67
0.11
0.16
0.002
Percent
Removal
71.1
44.7
94.6
94.3
71.6
41.9
62.0
82.7
73.7
99.4
8.3
14.8
33.3
75.0
25.0
99.3
24.1
64.6
95.3
33.3
Discharge
Standard
100
35
0.02
0.1
0.2
7.0
0.1
0.6
0.01
This system consists of lime addition, sedimentation, air stripping, neutralization, nutrient
supplementation and activated sludge.
* mg/1
-------
of data on this treatment sequence was
gathered when the system included
chemical addition, primarily lime, to
both assist in heavy metal removals and
clarification, as well as, raise the
pH to above 10.5 to enable ammonia
removal by stripping in the aerated
lagoon. Data gathering in the final
mode followed installation of the
aerated equalization lagoon at the
head of the plant. Leachate, when
treated only in the System 2 sequence,
was returned to the landfill.
In Table 6 is presented the per-
formance data on System 2. Values
contained in this table are the averages
of all samples analyzed. As indicated,
influent values are the averages for
the entire project period. Lime treat-
ment effluent values are those collected
whenever this process was in operation.
Finally, ammonia stripping lagoon effluent
values are those obtained whenever it was
operating. For this reason effluent
values should be compared only to influent
and not to one another except in a
general way.
The information in Table 6 generally
indicates the beneficial effect of the
ammonia stripping lagoon. As seen,
ammonia was reduced by nearly 60 percent
when the lagoon was in operation.
Presented in Table 7 are the average
costs of operation and maintenance of this
treatment facility in the System 2 sequence.
As seen in this table, cost information is
presented for three operating periods, one
without and two with the ammonia stripping
lagoon in operation. As with System 1
power costs represent the major cost of
leachate trea.ment. Because of fluctua-
tions in the raw leachate quality and the
fact that the operating periods do not
overlap, the two total cost figures
should not be directly compared.
Following completion of the initial
evaluation of System 1 on May 1, 1977,
a four-month evaluation of treatment
sequences, Systems 3 and 4, was conducted.
System 3 consisted of reversing the flow
so that raw leachate first entered the
biological treatment tanks followed by
chemical/physical polishing of the
effluent. System 4 represents the
treatment efficiencies of the biological
treatment section alone. These two
treatment sequences were attempted only
after the activated sludge had become
acclimated to leachate, since early
project attempts to acclimate a sewage
activated sludge to raw leachate had
failed. Table 8 summarizes the
efficiencies of these two sequences in
treating landfill leachate.
TABLE 7. OPERATION AND MAINTENANCE COSTS - SYSTEM 2 -
(11/15/75 - 5/1/77 and 11/1/77 - 8/31/78)
Flow, average gpd
Lime, lb/1000 gal
NaOH, gal/1000 gal
NaOCl, gal/1000 gal
Costs, $/1000 gal
Power
Lime
NaOH
NaOCl
Total
During Operation Without Lagoon
11/15/75 - 6/14/76
22,805
29.7
0
0
1.48
.89
0
0
2.37
During Operation With Lagoon
6/14/76 - 5/1/77 &
11/1/77 - 8/31/78
38,618
19.40
0.044
0.054
1.70
0.58
.03
.04
2.35
321
-------
TABLE 6. SUMMARY OF EFFECTS OF CHEMICAL/PHYSICAL TREATMENT
Sus. Solids
Dis. Solids
COD
BODc
.J
Alkalinity
Hardness
Magnesium
Calcium
Chloride
Sulfate
Phosphate
Ammonia-N
Kjeldahl-N
Sodium
Potassium
Cadmium
Chromium
Copper
Iron
Nickel
Lead
Zinc
Mercury
Raw
Leachate
x(mg/l)
1044
13029
18553
10907
5404
4652
453
818
4240
462
2.74
1001
984
1354
961
0.086
0.28
0.39
312
1.55
0.67
21
0.007
Lime Treatment
Effluent +
x(mg/l) R(%)
239
7972
7188
5265
3052
2461
209
696
3516
426
0.26
890
867
830
613
0.03
0.09
0.10
3.8
0.57
0.24
0.61
0.003
77.1
38.8
61.2
51.7
43.5
47.1
53.9
14.9
17.1
7.8
90.5
11.1
11.9
38.7
36.2
65.1
67.8
74.7
98.8
63.2
64.2
97.1
57.1
Ammonia Lagoon
Effluent -H-
x(mg/l) R(%)
288
4650
8793
3600
2374
1587
117
424
2669
525
0.27
412
349
956
572
0.04
0.08
0.27
5.6
0.73
0.23
0.85
0.010
72.4
64.3
52.6
67.0
56.1
65.9
74.2
48.2
37.0
—
90.1
58.8
64.5
29.4
40.5
53.5
71.4
30.8
98.2
52.9
65.7
96.0
"
+ 11/15/75 - 5/1/77 and 11/1/77 - 8/31/78
H-f 6/14/76 - 5/1/77 and 11/1/77 - 8/31/78
x Average concentration.
R Percentage removal.
-------
As seen in this table biological
treatment only, while showing signifi-
cant reductions in organic matter, did
not perform anywhere well enough to
permit discharge in compliance with the
facilities discharge permit. System 3,
which included chemical/physical polish-
ing of the effluent, achieved signifi-
cantly greater removal efficiencies but
again failed to reach discharge standards.
No cost information was developed for
these treatment sequences.
The overall conclusion, based upon
system performance in the four described
sequences, is that treatment of leachate
from this landfill must include biological
treatment preceded by chemical/physical
processes.
Of the several additional leachate
treatment technologies investigated in
bench-scale units on a limited basis,
only activated carbon filtration and
breakpoint chlorination yielded meaning-
TABLE 8. SUMMARY OF SYSTEMS
ful results. Carbon filtration of this
raw leachate was unsuccessful due to
rapid plugging of the filter media.
Carbon filtration of system effluent,
however, provided significant additional
reductions in heavy metals concentrations.
Breakpoint chlorination was demonstrated
as accomplishing additional ammonia
reduction in the final treatment plant
effluent. The remaining limited evalua-
tions of methods for improved heavy
metals and suspended solids removal
were inconclusive.
A more complete discussion of these
bench-scale evaluations, as well as a
thorough discussion of performance in
the Systems 1 through 4 treatment se-
quences, is included in the final report
on this demonstration. This report,
entitled "Demonstrating Leachate Treat-
ment - Report on a Full-scale Operating
Plant," will be available shortly from
the Office of Solid Waste.
3 AND 4 (5/1/77 - 8/31/77)
Parameter
Alkalinity
Ammonia-N
BODs
Cadmium
Calcium
Chloride
Chromium
COD
Copper
Dis. Solids
Hardness
Iron
Kjeldahl-N
Lead
Magnesium
Mercury
Nickel
Phosphates
Potassium
Sodium
Sulfate
Sus. Solids
Zinc
Raw
Leachate
x\mg/l)
5087
649
12649
0.11
937
4178
0.48
21152
0.27
14742
4463
348
708
0.76
350
0.007
2.0
2.3
1076
1536
658
1136
40
System 4
Effluent
x(ms/l)
2788
312
2150
0.08
573
3778
0.37
4680
0.22
10081
2805
195
347
0.50
242
.007
1.29
4.6
996
1412
853
1322
19
R(%)
45.2
51.9
83.0
27.3
38.8
9.6
22.9
77.9
18.5
31.6
37.1
44.0
51.0
34.2
30.9
0
35.5
—
7.4
8.1
—
—
52.5
System 3
Effluent
x(mg/l)
1178
153
763
0.02
287
1496
0.08
2257
.07
5353
924
1.02
180
0.15
48
.002
0.27
0.56
476
719
513
180
0.51
R(%)
76.8
76.4
94.0
81.8
69.4
64.2
83.3
89.3
74.1
63.7
79.3
99.7
74.6
80.3
86.3
71.4
86.5
75.7
55.8
53.2
22.0
84.2
98.7
Discharge
Standard
(mg/D
*
35
100
0.02
*
*
0.1
*
0.2
*
*
7
*
0.1
*
0.01
*
*
*
*
*
*
0.6
* No discharge standard for this parameter.
X Average concentration. R Percentage removal.
323
-------
REMEDIAL ACTION ALTERNATIVES FOR MUNICIPAL
SOLID WASTE LANDFILL SITES
By:
William W. Beck, Jr.
A. W. MARTIN ASSOCIATES, INC.
King of Prussia, PA
ABSTRACT
There are numerous remedial action alternatives (remedial measures)
for use during or after closure of landfills and dumps which do not
meet current environmental standards. Some of the alternatives are
passive, that is, they require little or no maintenance once emplaced.
Others are active and require a continuing input of manpower or elec-
tricity.
Most of the techniques discussed herein deal with the reduction or
elimination of infiltration into landfills in one of five categories:
surface water control, passive ground-water management, active ground-
water or plume management, chemical immobilization of wastes, and
excavation and reburial. The technology presented is widely used in
construction but has not necessarily as yet been applied to landfill
closure.
INTRODUCTION
Most of the municipal refuse
in the United States is disposed
of in approximately 15,000 sites,
two-thirds of which are open
dumps. The Solid Waste Disposal
Act as amended by the Resource
Conservation and Recovery Act
(RCRA) of 1976 requires the
phasing out of open dumps within
the next 5 years. With the
implementation of RCRA and more
stringent State solid waste
disposal practices it is antici-
pated that the majority of the
approximately 10,000 open dumps
will be closed within the next 5
years and increased volumes of
solid waste will be disposed of
in existing permitted sanitary
landfills.
Closing open dumps and
upgrading existing landfills both
involve minimizing or eliminating
the potential for resource contam-
ination. Remedial measures are
used to reduce the amount or
concentration of the contaminants
produced and/or to prevent or
redirect their movement from the
disposal site. The procedures
described here have been general-
ized and although widely used by
the construction industry, they
have not been applied to landfill
closure. For some waste disposal
sites remedial methods may be
suitable, while for other sites,
because of their size or speficic
characteristics, these methods
may be impractical.
REMEDIAL ACTION ALTERNATIVES
To illustrate the remedial
methods, a hypothetical 4-hectare
(10-acre) landfill located in the
northeastern United States in a
depression situated on a slope
between an upland ground-water
recharge area and a ground-water
discharge area with a stream is
utilized. The landfill is under-
lain by 30 m (100 ft) of uncon-
solidated, fairly permeable mate-
rials of either glacial, coastal,
324
-------
or saprolitic origin, underlain
by an indeterminate bedrock. The
water table is 6 m (20 ft) below
the ground surface and the lower
3 to 5 m (10 to 15 ft) of the
landfill is in the ground water.
The landfill originated as a
pushover burning dump. The waste
is 12 to 15 m (40 to 50 ft) deep
and extends 3 to 5 m (10 to
15 ft) above the ground surface.
The bottom 3 to 5 m (10 to 15 ft)
was dumped rather than landfilled
and is located below the water
table. The remaining waste was
landfilled and covered with very
sandy material. Mainly municipal
refuse has been accepted at the
site. However, during the time
it was operated as a dump, no
records of the materials depos-
ited were kept, and it is possi-
ble that several nearby indust-
ries may have dumped industrial
and/or hazardous wastes into the
landfill.
To minimize pollution from a
solid waste disposal site, leach-
ate generation and movement must
be limited or controlled. Leach-
ate production can be controlled
by minimizing the amount of water
entering the landfill. Reducing
the amount of water in contact
with the fill reduces the quan-
tity of leachate generated.
However, if the quantity of water
is not sufficiently minimized,
the pollutional load may not be
reduced at all and, indeed, may
be increased due to higher con-
taminant concentrations. There-
fore, if water inflow reduction
is to be used as a remedial
measure, the reduction must
be significant.
It is generally not possible
to reduce or eliminate the amount
of moisture present in municipal
refuse when collected. However,
both vertical and horizontal
percolation into the fill can be
controlled by a number of tech-
niques designed to either in-
crease or decrease flow. The
techniques considered herein have
been grouped in five categories:
surface water control, ground-
water control, plume management,
chemical immobilization, and
excavation and reburial. It may
be necessary to apply more than
one method from more than one
category to effect significant
results. For ease of comparison,
the major characteristics and
estimated costs based on the
hypothetical 4-hectare (10-acre)
landfill of these alternatives
are summarized in Table 1.
SURFACE WATER CONTROL
Surface water infiltration
can often be reduced during
normal landfill closure if care-
ful design and construction
practices are followed. There
are four ways to minimize water
infiltration. The first is to
increase runoff from the landfill
surface by regrading to provide
for moderate sheet flow from the
surface. The second is to reduce
the amount of runoff flowing onto
the landfill surface by con-
structing diversion ditches and
terraces. The third is to de-
crease infiltration into the
landfill by applying a low
permeability cover or seal to
retard the vertical movement of
water below the cover material.
The fourth is to increase inter-
ception and transpiration of
precipitation by planting vege-
tation on the landfill.
To increase runoff from the
landfill by regrading (see
Figure 1), the surface should be
sloped such"that the water has
the shortest possible flow path
from any point on the site. Thus
a mound in the central portion
sloping equally on all sides is
an ideal regrading plan. Depend-
ing on the type of soil on the
site, slopes of 6 to 12 percent
are generally recommended. The
cost of this regrading will
depend upon the current grade of
the landfill and the availability
325
-------
TABLE 1. SUMMARY OF ESTIMATED COSTS
AND CHARACTERISTICS OF REMEDIAL METHODS
Method
Average
Estimated Costs*
(S in Thousands)
Characteristics/Remarks
Contour Grading 184
Surface Hater Diversion 20
Surface Sealing
Clay [15-46 cm (6-18 in.)) 234
Bituminous Concrete 14-13 cit\
(1.5-5 in.)) 315
Fly Ash [30-60 cm (12-24 in.)) 235
PVC (30 mil) 482
Drainage Field (if required) 65
Revegetation on Elopes <12 percent 10
on Slopes>12 percent 19
Surface Water Control
Increases runoff, reduces infiltration.
Diverts surface water from fill.
If locally available, native clay is eco-
nomical means of retarding infiltration.
Rapid coverage; can eliminate infiltration.
Material nay leach metals; nay be available
free.
Very impermeable; expensive ceal; careful
subgrade preparation is necessary.
Carries infiltrated water off seal; in-
creases effectiveness of seal.
Stabilizes cover material; seasonally in-
creases transpiration; provides aesthetic
benefit.
Bentonite Slurry Trench
Grout Curtain
Sheet Piling
Bettor Sealing
670
1,400
800
4,000
Groundwater Control
Simple construction methods; retards ground-
water flow.
Very effective in permeable Boils.
Widely used for shoring.
Leachate collection may be needed; acts as a
liner; difficult drilling through refuse.
Drains 23
.Hell Point Dcwatering 185
Deep Well Dewatering 163
Injection/Extractior. Barrier 199
Spray Irrigation 336
At-grade Irrigation 32
Subgrade Irrigation 2B
Plume Management**
Effective in"lovenng water table a few
meters in unconsolidated materials; can
be used to collect shallow leachate.
Suction lift limits depth to 7-9 n (20-30
ft); inexpensive installation; uses only
one pump; car be used to collect shallow
leachate.
Used in lowering deep water tables; one
pump needed per well; high maintenance
costs.
Creates a hydraulic barrier to stop leach-
ate movement; operation and maintenance
costs are high.
Spreads leachate over the landfill for re-
cycling; potential odor problem.
Gated pipe with ridge and furrow irriga-
tion; potential odor problem; recycles
leachate.
L>arge-scale drainage field; recycles leach-
ate.
Chemical Fixation of Cover
Chemical Injection
145
Chemical Immobilisation
OSes chemically fixed sludge to provide a
top seal; provides means of disposal for
sludge; he.'ps stabilize landfill.
Immobilizes a single pollutant; In nost
cases not feasible.
Excavation and Reburxal
4,570
Excavation and Beburial
Very expensive; difficult construction.
•Costs for hypothetical 4-hectare 110-acre) landfill
••Costs include present worth of 20 years, operation, maintenance, and, where applicable,
power for 4-hectare (10-acre) landfill.
326
-------
co
ro
Seeding ft Mulching
Oivtriion Ditch
Mo « dope 18 percent
Contour Grade(6 —12 percent)
UNCONSOLIDATED EARTH MATERIALS
Stream
BEDROCK
Not to Sco/f
Figure 1. Cross section of landfill showing contour grading
and surface water diversion.
-------
of local cover material. If
major changes in grade are
necessary, costs will escalate
rapidly.
Diversion ditches are gen-
erally most useful in areas where
the landfill is at the middle or
the bottom of a slope and surface
water collects upslope from the
landfill and flows onto it.
Standard construction techniques
developed for handling storm
runoff in highway and subdivision
construction can be used to
redirect surface water around a
landfill. These techniques are
generally not excessive in cost
if the equipment used for re-
grading and covering operations
is already available at the
landfill.
If the material available
for covering the site is highly
permeable and if the landfill is
in an area of high rainfall,
surface sealing may be effective
(see Figure 2). A number of
materials potentially suitable
for sealing, in order of gener-
ally increasing costs, are local
clay (where available), soil
cement, bentonite, bituminous
concrete, asphalt, and plastic
(PVC) membranes. These materials
can markedly reduce infiltration
into the landfill. In cases
where low permeability cover
material is to be placed over the
seal, it may be necessary to
construct a drain on top of the
seal to carry away water inter-
cepted by it. A properly con-
structed seal can reduce infil-
tration essentially 100 percent.
An important consideration
in landfill surface sealing is
gas venting. Some kind of
opening such as a gravel trench
with mushroom cap vent (shown on
Figure 2) or gas venting wells
must be provided to allow escape
for the gases formed by decom-
posing refuse. The gas can be
collected in trenches or wells
and, if sufficient quantities are
available, it can be used or
sold.
Revegetation of the completed
landfill surface is recommended
in favorable climates to stabi-
lize the final cover material,
aesthetically upgrade the area,
and seasonally increase evapo-
transpiration of precipitation.
Procedures for vegetating the
landfill surface are very similar
to those used in stabilizing
highway grades and other areas of
recent construction. The surface
can be hydroseeded with a suit-
able grass mixture and mulched
with a straw mulch. Steep slopes
can be treated with legumes or
vetch to hasten stabilization.
Overland runoff over unvegetated
soils rapidly erodes most cover
materials and destroys the final
grade. Therefore, vegetation is
strongly recommended in most
areas.
GROUND-WATER CONTROL
Subsurface infiltration
barriers, or passive ground-
water control measures, are
designed to either prevent
ground water from flowing through
the landfill and generating
leachate or control the movement
of leachate away from the land-
fill. Barriers are constructed
of low permeability materials to
divert and impede ground-water
flow in the vicinity of the
landfill. The engineering tech-
nology associated with ground-
water barriers has been developed
for use in constructing cutoff
walls around and under dams and
excavation control structures in
areas of shallow ground water,
e.g., at the sea coast. Barriers
that can be used at landfills
include slurry trenches, grout
curtains, sheet pilings, and
landfill bottom sealing.
Slurry trenches (see Figure
3) are constructed by excavating
a trench through a bentonite
slurry using draglines. The
bentonite slurry is continuously
pumped into the excavation and
328
-------
OJ
ro
4 hectares (lOacres)
Contour Grade 16-12 percent)
Gravel Trench
Mushroom Cop
Gas Vent
Seeding and
Mulchmg~~\
Mai. Slope
L>vl8 percent
I I/I)
IZ-l5ml«O-5O.ft)
46cm (I8ln) Soil Cover
Cop of Suitable Seal Material
UNCONSOLIDATED EARTH MATERIALS
Figure 2. Cross section of capped landfill.
-------
UNCONSOUOAT E D
EARTH MATERIALS
BEDROCK
Hot to Scolt
(a)
(b)
Figure 3. Cross section of landfill
before (a) and after (b) slurry-trench
cutoff wall installation.
330
-------
serves to stabilize the nearly
vertical wall of the trench and
ultimately to seal the area. The
excavation is often carried to
bedrock or other low permeability
layer but can be terminated at
shallower depths. Although
costly, slurry trenches are
generally the least expensive
form of passive ground-water
barrier.
Grout curtains (see Figure
4) are emplaced by forcing a thin
cement grout through tubes which
are driven deep into the ground
on 2- to 3-foot centers and
withdrawn slowly. Two or more
rows of grout are usually needed
to provide a seal. Like a slurry
trench, the grout is generally
emplaced down to an impermeable
layer. Grout curtains are quite
expensive when constructed to the
dimensions necessary to cut off
ground-water flow in the vicinity
of a reasonably sized landfill.
Sheet piling (see Figure 5)
has been extensively used in
near-shore and offshore con-
struction to stabilize areas for
excavation. It is driven into
the ground with a pile driver so
that depending on the design the
piles either butt or interlock.
For sheet piling, as for all of
the passive groundwater barriers,
unconsolidated material must be
present around the landfill with
no large stones or boulders as
these will deflect or prevent the
piling from being effectively
driven. Sheet piling is gener-
ally very expensive when used in
the quantities necessary at
landfills.
Bottom sealing (see Figure
6) of a landfill is like emplac-
ing a grout curtain in a bowl
shape under the landfill. Grout
tubes are driven through the
landfill, which can entail
considerable expense because of
bulky or resistant refuse. A
bottom-grouted landfill is
similar to an engineered landfill
with a liner except that the seal
is emplaced after filling.
Generally speaking, unless the
sources of leachate generation
were removed, leachate collection
would be necessary with a bottom-
grouted landfill.
PLUME MANAGEMENT
The purpose of plume manage-
ment or active ground-water
management is to manipulate the
water table in the area of the
landfill to either prevent the
formation of leachate or contain
its spread. To do this, water
must be extracted from or added
to the ground-water system
through drains, shallow well
points, or deep wells. The
capital costs of these systems
are generally much lower than
those of passive barriers, but
the operation and maintenance
costs are considerably higher
since in most cases a continuing
supply of electrical power and
ongoing maintenance of pumps and
wells is required.
The technology of drains has
been developed for use in ag-
riculture, highway, and con-
struction. Drains (see Figure 7)
can be a low-cost means of
lowering the water table a few
meters provided the area in
which the drain is to be em-
placed can be readily excavated.
Drains can be used to lower the
water table upgradient of the
fill, to collect leachate if it
is following a shallow flow
path, or to introduce leachate
over the refuse on top of the
fill. Drains are generally
constructed using crushed stone
and perforated pipe. Construc-
tion costs are comparatively low
providing the depth of drain
emplacement is not excessive.
However, when highly mineralized
waters are present, drains are
more susceptible to clogging and
maintenance costs may be sig-
nificant.
Well points (see Figure 8)
are widely used in construction
331
-------
co
co
po
UNCONSOLIDATED
EARTH MATERIALS
Figure 4. Cross section showing a grout curtain at landfill-
-------
GO
u>
Co
UNCONSOLIOATED
ARTH MATERIALS
Figure 5. Cross section showing a sheet piling cutoff wall
at landfill
-------
co
CO
Mm. I 3m (3ft) soil loytr
UNCONSOLI DATED EARTH MATERIALS
Figure 6. Cross section showing a grouted bottom seal
beneath landfill.
-------
CO
co
en
UNCONSOLIDATEO
EARTH MATERIALS
Figure 7. Cross section showing a drain downgradient from
the landfill.
-------
GROUNDWATER
BlFLOW
^-Assumes noleochote
colltcted with groundwoter
WELL
POINTS
OR
EXTRACTION
WELLS
STONE -
FILLED
TRENCH
FOR RECHARGE*
4-hectore
(10-ocre)
LANDFILL
Discharge From
We I It to Trerx-h
DISCHARGE
PIPE
Figure 8. Plan view of well points or extraction
wells used to lower the water table upgradient
from the landfill.
336
-------
to dewater shallow excavations.
They are effective up to the
limits of suction lift, i.e., 7
to 9 m (20 to 30 ft) below the
ground. The main advantage of
well points is that a large
number of wells can be powered
using a single suction pump.
They are effective for dewatering
shallow landfills and collecting
shallow leachate. The instal-
lation cost for well points is
moderate but maintenance can be
relatively high since a good
vacuum must be maintained on the
entire system.
Deep wells (see Figure 9)
can be used to dewater consoli-
dated formations or areas where
the water table is too deep for
economical use of suction lifts
or drains. Construction and
operation of deep wells is a
relatively simple but long-term
operation, and maintenance costs
can be high especially if the
wells are used to collect leach-
ate.
Any of these systems can be
used to inject water into an
aquifer to provide a ground-water
barrier to the flow of leachate.
This technology has been de-
veloped and applied in control-
ling the spread of sea water into
potable aquifers and is potenti-
ally applicable to control leach-
ate movement toward important
well fields. However, the
operation and maintenance costs
are high and the leachate is only
rerouted from its path, the
quantity generated is not re-
duced.
The use of any of these
systems for leachate collection
will necessitate some means of
leachate disposal. It is often
feasible to recycle the leachate
onto the landfill to hasten
landfill stabilization. Leachate
can be recycled by spray irri-
gation, at-grade irrigation, or
subgrade irrigation (i.e., drains
and tile fields). Spray irri-
gation involves the highest
capital, energy, and maintenance
costs, but also provides some
leachate treatment and recy-
cling. At-grade irrigation
considerably reduces the power
requirements but shares with
spray irrigation potential odor
problems. Subgrade irrigation
provides little direct leachate
renovation but avoids the
potential problem of having
large quantities of leachate
exposed at the ground surface.
Generally speaking, landfills
will stabilize more rapidly with
leachate recycling. Poten-
tially, a leachate collection
system could be abandoned when
the landfill has stabilized.
All of these ground-water
management schemes involve a
long-term commitment of manpower
and funds to the maintenance and
operation of the systems.
Probably the least operation and
maintenance costs would be
required using drains and the
most using a leachate collection
and recycling system. However,
there may be cases where any or
all of these measures will be
applicable and necessary for
leachate control.
CHEMICAL IMMOBILIZATION
Chemical immobilization is
a developing technology used to
stabilize the waste and/or cover
material through a chemical
reaction. The method involves
either the emplacement of a
chemically stabilized low
permeability cover or the
injection of a chemical into the
refuse and leachate plume to
destroy a contaminant. The
technology for chemical im-
mobilization' originated in
chemical engineering and sludge
stabilization work.
The first use of chemical
immobilization (see Figure 10)
is identical in intent to top
sealing but uses a chemically
stabilized waste product, i.e.,
sludge, to form a low perme-
337
-------
co
GO
CO
Woltr table
belor*
Stone-filled trench
for recharge
UNCONSOLIDATED
EARTH MATERIALS
~~^—Water table with pumping
BEDROCK
*A«tumes no leoctiate collected with groundwoler
Figure 9. Cross section showing an extraction well at
landfill.
-------
co
co
10
4 hector*! (lOocres)
Contour Grade (6-12 percent)
Seeding and
Mulching
Cap of Chemically Stabilized
Waste Material C60m (2ft)3
UNCONSOLIOATED
EARTH MATERIALS
Figure 10. Cross section of landfill sealed with
stabilized waste material.
-------
ability blanket on top of the
landfill. In areas where this
would be permitted, this method
would have the beneficial effect
of disposing of a waste product
and at the same time aiding in
the stabilization of the land-
fill. Most chemical immobili-
zation processes are proprietary,
but in general they involve
either a cement base or chemical
reaction base process. When a
suitable waste material is
available within reasonable
distance of the landfill, this
procedure can be cost-advan-
tageous over other top sealing
technology.
The other form of chemical
immobilization (see Figure 11) is
the injection of a chemical to
destroy or tie up a specific
pollutant. Generally speaking,
any one chemical is effective
only against one or two types of
pollutants. This process is
potentially very expensive but
would be applicable in areas
where a known hazardous material,
such as cyanide, had been em-
placed and was migrating with the
ground water. Chemical immobili-
zation is a developing field and,
at present, most methods of
chemical immobilization would not
be feasible for municipal refuse.
EXCAVATION AND REBURIAL
The purpose of excavation
and reburial is to move the
leachate-generating material to a
better engineered or environ-
mentally less sensitive area.
Although conceptually very
simple, excavation and reburial
is expensive as well as practi-
cally and politically difficult.
Basically, the process involves
removing the entire contents of
the landfill with common con-
struction procedures and moving
them, usually by truck, to
another area where a better
engineered and sited landfill is
available. Problems arising in
excavation and reburial include
the technical problems of re-
movina large quantities of bulky
and partially decomposed wastes
from the landfill, transporting
partially saturated and saturated
material over public roads with-
out spillage or leakage, and
cleaning up a leachate-filled pit
after the waste material has been
removed.
In addition, in most cases
there are political constraints
on the movement of such material
through any populated areas, and
there may be considerable local
opposition to the importation of
municipal refuse to an existing
or new landfill. The process is
in any case very costly, but in
areas where a severe leachate
problem has developed and a
properly designed landfill is
available nearby it may be
applicable.
SUMMARY
Surface regrading and
revegetation is useful and
necessary at practically all
landfills, and surface
sealing is a useful adjunct
to this where no natural low
permeability cover is available.
Groundwater manipulation is
potentially very effective in
areas where either much of the
landfill is below the water table
or the leachate is moving toward
an important public water supply.
Leachate collection and recycling
may be a useful part of ground-
water control. Chemical im-
mobilization is a relatively new
technology whose applicability
will increase as more techniques
are developed; however, the use
of a stabilized sludge or other
waste product for cover or
sealing material appears to be
feasible in areas where it would
not be prohibited by local
authorities and where the mate-
rial is locally available.
Excavation and reburial should be
generally considered as a last
resort which would be used only
when all efforts to stabilize the
refuse in place appear to be
futile. Although it is poten-
340
-------
Metering
Well
pump
6m
(20ft)
WoleJ
Tobt«
30m
1100ft)
27m
(90 III
4 hectares (lOocresl-
-Hvpochlocilt
storage
Water supply well
•
UNCONSOLIOATEO EARTH MATERIALS
.Infection pipe is pulled
up and chemical is injected
at successive depths.
BEDROCK
Hot to Scott
Stream
Figure H- Cross section of landfill treated by
chemical injection.
-------
tially very effective it is also
a difficult and expensive under-
taking.
In the selection of remedial
measures for use in minimizing
pollution at any waste disposal
site, professional feasibility
assessment and design will be
necessary.
ACKNOWLEDGEMENTS
This paper concerns itself
with one phase of a multiphase
project being conducted by A. W.
Martin Associates, Inc. under
U.S. EPA Contract No. 68-03-2519,
Donald E. Banning, Project
Officer. Other phases involve
the selection of an abandoned
waste disposal site for study,
the design and implementaion of
remedial neutralization pro-
cedures, and the implementation
of a monitoring program to de-
termine the effectiveness of the
procedures. A comprehensive
discussion of remedial measures
and estimates of their costs can
be found in "Guidance Manual for
Minimizing Pollution from Waste
Disposal Sites" (EPA-600/2-27-
142) .
342
-------
REMEDIAL ACTION ACTIVITIES FOR ARMY CREEK LANDFILL
David C. Clark, P.E.
New Castle County D.P.W.
Newark, Delaware
Contributions By:
W. M. Leis, R. F. Weston, Inc.
A. Thomas, R. F. Weston, Inc.
ABSTRACT
Groundwater contamination due to leachate emanating from the
Army Creek Landfill in New Castle County, Delaware, has been con-
trolled by a system of pumping wells. From the outset, the wells
were considered to be temporary control measures until a permanent
solution was developed.
After five years of extensive research, the recommended
permanent control measures are still hydrogeologic in nature. They
include;
• Minimize leachate production by decreasing precipitation
infiltration and groundwater flow.
• Maximize leachate recovery by locating contaminant recovery
wells closer to and within the landfill.
Initial costs associated with this program are approximately
$4.4 million with annual operating and maintenance costs approaching
$990 ,000 per year.
SITE HISTORY
Between 1960 and 1968,
New Castle County, Delaware
utilized an abandoned sand and
gravel pit as the primary dis-
posal site for municipal and
industrial wastes. The land-
fill location in Northern
Delaware is shown on the map
in Figure 1.
From records and test
borings, it was determined
that a modified area fill
method was used to emplace
the refuse material. During
the landfilling operation, daily
covering was probably not practiced.
This, coupled with less than ade-
quate compaction within the areas,
caused differential settling and
an uneven finished surface when
the fill was closed.
The final lift was emplaced
in 1968, and the completed fill
encompassed a volume of 1.9 million
cubic yards of refuse, about 30 per-
cent (or 600,000 cubic yards) of
which was beneath the seasonal high
water table. Refuse thicknesses
343
-------
FIGURE l LOCATION MAP OF ARMY CREEK LANDFILL
-------
over the 47-acre site range
from about 6 to over 35 feet.
Late in 1971, water in
a residential well, located
900 feet southwest of the land-
fill, developed quality pro-
blems such as a distinctly
disagreeable odor and perma-
nent staining of porcelain
fixtures. Gradually, this
condition became more pro-
nounced and the water supply
abandoned. Analyses conduct-
ed by the Delaware Geological
Survey and New Castle County
Public Works Department indi-
cated the presence of leachate
in the ground water. In ear-
ly 1972, intensive field study
was begun by New Castle County
through its consultant, Roy F.
Weston, Inc., and the Dela-
ware Geological Survey to de-
termine the hydrogeologic cir-
cumstances responsible for
this problem.
HYDROGEOLOGIC DESCRIPTION
The surficial geology
of the old gravel pit/landfill
consists of medium and coarse-
textured, channel-bedded, un-
consolidated sands that demon-
strate substantial textural
variability within a short
vertical section. The origin
of these sands has been relat-
ed to glacial meltwaters hav-
ing seasonal discharges. The
deposits settled in shallow,
relatively narrow braided
channels with numerous ice
floes. These deposits have
been formally named the Colum-
bia Formation and within the
study area form a continuous
surficial layer up to 60 feet
in thickness with the forma-
tional base varying between
+20 to -20 feet present mean
sea level. Dragline excava-
tions in the gravel pit dur-
ing quarrying had terminated
at a basal quartz conglomerate
It has been determined from air
photos that in at least two places
within the gravel pit this basal
conglomerate was removed by exca-
vation and the bottom of the gravel
pit was continued into the under-
lying aquifer sands of the early
Cretaceous Potomac Formation which
has been heavily developed for
ground water since the early 1960's.
In the immediate area, well
pumpage has exceeded 8 mgd during
this decade. Consequently, the
natural southerly ground water
gradient has been steepened, and
the rate of ground water movement
has been greatly accelerated.
This was an alarming discovery
considering a wellfield belonging
to a major water company lies
3,000 feet southwest of the land-
fill. See Figure 2.
CONTAMINATION HISTORY
By mid-1972, an investiga-
tion had been undertaken to deter-
mine the extent of the leachate-
affected area. Figure 2 shows the
leachate plume as determined by
data gathered from an expanded
monitor well network. This line
is an approximate location based
upon specific parameters used as
standard indicators. These param-
eters included physical appearance
of water, e.g. color and odor, and
COD, total iron, manganese, and
chlorides. The concentration of
iron and manganese in aquifer
waters is such that they are use-
ful as quality parameters. Their
gradual increase over background
conditions has, therefore, indica-
ted: (1) remobilized metals under
nonequilibrium conditions and/or
(2) fresh dissolved metals carried
in,solution. The COD levels with-
in the landfill were normally high
(see Table 1). A few hundred feet
south in monitoring wells nearest
the landfill the COD levels had
dropped significantly, indicating
that organic decomposition of the
landfill was subsiding or, more
345
-------
GO
-p»
en
DELAWARE SAND &
GRAVEL LANDFILL x
FIGURE 2 EXTENT OF CONTAMINATION MIGRATION AS OF
AUGUST 1973 IN RELATION TO THE DELAWARE SAND &
GRAVEL LANDFILL AND THE ARTESIAN WATER
COMPANY WELLFIELD
-------
likely, that fresh, oxygena-
ted recharge waters were ful-
ly oxidizing the organics
within the Potomac aquifer
through interformational leak-
age.
Based on aquifer char-
acteristics of the Upper Po-
tomac, the rate of contaminant
migration was computed. The
permeability of the channel
sands of the Potomac is great-
er than 500 gpd/sq. ft. The
hydraulic gradients, as can
be inferred from the potenti-
ometric surface map in Figure
3, vary from about 0.015 ft./
ft. immediately south of the
landfill to 0.02 ft./ft., as
the gradient steepens nearer
the production wells. An
average rate of movement of
0.5 feet per day is reason-
able for the area close to
the landfill and increases to
1.5 ft./day down-gradient
closer to the pumping centers
of the nearby water company
wells.
As leachate enters the
Upper Potomac aquifer, bar-
ring attenuation of select
constituents, it was expected
to reach the water company's
pumping wells within 10 years
if no corrective procedures
were undertaken.
LEACHATE QUALITY
The quality of leachate
generated by saturated decom-
position of domestic refuse
depends upon such variables
as waste composition and
sorting, compaction, moisture
capacity, temperature, and
age of the refuse. Thus, the
actual concentrations of chem-
ical species in various leach-
ates vary greatly. A young
landfill will generally pro-
duce a leachate characterized
by very high concentrations
of dissolved organic and inorganic
substances. Both the Chemical Oxy-
gen Demand (COD, a measure of dis-
solved organics) and the Total Dis-
solved Solids concentration (TDS,
a measure of dissolved inorganics)
are typically in the thousands of
parts per million for the raw leach-
ate. The concentration of most
environmentally significant metals
greatly exceeds the recommended EPA
limits for such substances in pot-
able water. The leachate concen-
tration rapidly decreases as it
migrates down-gradient from the
landfill by such processes as dilu-
tion, bioassimilation, chemical ox-
idation, and adsorption.
The background water quality
in the Potomac aquifer has a low
dissolved solids concentration.
The range of inorganic constituents
in natural Potomac waters is listed
in Table 1, along with comparison
values from selected observation
wells located within and down-gra-
dient of the landfill.
COUNTER-PUMPING PROGRAM
The installation of a net-
work of monitoring wells was com-
pleted in early 1973, so that the
ground water area affected by migra-
tion of leachate could be fully
identified.
Through an analysis of the
initial flow network in the Potomac
aquifer and computed well interfer-
ences from selected observation
wells, an interim contaminant con-
trol was designed. The control
consists of an artificially de-
pressed drainage divide within the
Upper Potomac aquifer, down-gradient
from the landfill at about a third
of the linear distance to the water
company wellfield. The drainage
divide, as designed, was composed
of a two-part well interference
system. Counter-pumping wells were
systematically located within the
channel sands of the Upper Potomac
aquifer to create the initial
347
-------
Map showing the theoretical ground water flow pattern in the
upper Potomac aquifer based on piezometric and stratigraphic
information in the vicinity of the Army Creek Landfill, September 1972
-10
co
-p=>
O3
0 1000 2000 3000 4000
I— I +=
Scale in Feet
O Production Well
• Observation Well
Piezometric Contour (feet below mean sea level)
10 Foot Contour Interval
Flow Lines
FIGURE 3 POTENTIOMETRIC SURFACE MAP OF THE UPPER
POTOMAC AQUIFER PRIOR TO INSTALLATION OF
CONTROL MEASURES
-------
Background Quality
Upper Potomac Aquifer
OJ
-p*
10
COD (ppm)
IDS (ppm)
NH.N (ppm)
NO,N (ppm)
Cl (ppm)
2Fe (ppm)
Phenols (ppm) <
Sp C
(^ mhos cm-')
14
2Q
55
1 75
92
20
:20 ppb
120
Water table Beneath
Landfill
5617
3606
1134
436
550
18
2500
Potomac Aquifer 400
ft. Downgradient from
Landfill
170
933
722
236
47
01
1900
Concentration of Specific Chemicals and Contaminants Near Army Creek Landfill
TABLE 1
-------
divide. Secondly, the water
company wells were throttled
back to initiate head build-
up down-gradient. The first
counter-pumping wells have
been in operation since Novem-
ber 1973. At the time of com-
pletion in early 1974, the re-
covery wellfield was pumping
a total of 3.54 million gal-
lons of contaminated water
per day.
The divide has been
effective in preventing con-
taminated waters from flowing
into the steepened gradient
of the water company's wells.
In plan view, the divide con-
sists roughly of an L-shaped
ground water mound south and
east of the landfill as shown
in Figure 4. The flow lines
again indicate the preferred
flow path of a particle with-
in this network.
An added feature to the
divide is the physical remov-
al of contaminants at that
point. The leakage charac-
teristics through the Colum-
bia Formation south of the
counter-pumping network then
allow fresh recharge to enter
the aquifer. The recovered
contaminated water is allowed
to settle within a perched
retention pond south of the
landfill. Through mild oxi-
dation, certain contaminants
are removed and the overflow
infiltrates the Columbia For-
mation and the Delaware
Estuary.
In cross section, the
development of the drainage
divide during the history of
the leachate containment is
shown in Figure 5. Line A
shows the piezometric gradi-
ent from north to south be-
tween the landfill and the
community wells. Line B
shows the same traverse line after
initiation of the control measures'
in late 1973. Since that time, the
piezometric gradient has risen and
declined with respect to increased
recharge, seasonal demand, chemical
and bacteriological encrustation of
the recovery wells, and later re-
habilitation ; still it has remained
fairly constant in position and
effectiveness to this day.
The counter-pumping measures
at the Army Creek Landfill have
been successful. Figure 6 shows an
interpretive line of contaminants
based upon spring 1978 data. In
certain fringe area monitoring
points, the ground water quality
has actually been shown to improve,
although it is still below U.S.
Public Health Service limits and
EPA interim standards for potable
water.
The counter-pumping program
had, from its inception, been view-
ed as an emergency contaminant con-
trol program—one that would be
utilized to prevent further migra-
tion while an ultimate solution was
developed and implemented. Various
"permanent" solutions are summarized
below. It should be sufficient to
state that the presented cost esti-
mate reflects a "worst case" situ-
ation whereby each operation must
be carried out to its fullest ex-
tent. Furthermore, the presented
cost does not include control
measures for the neighboring
Delaware Sand and Gravel landfill.
I. ATTENUATION
This alternative involves
utilization of natural processes to
cleanse the aquifer. These pro-
cesses include dilution, adsorption,
and oxidation. It is concluded
that attenuation is presently taking
place in the aquifer, largely due
to dilution of contaminated water
by cleaner water entering the aqui-
fer and, to a lesser extent, to
350
-------
OJ
en
Piezometric surface March 1976
contours are in feet below sea level
RW-etc = well nos.
SCALE 1:9600
FIGURE 4 LOCATION OF RECOVERY WELLS AT ARMY CREEK
-------
Horizontal Scale 1:800
Vertical Exageration SOX
LANDFILL
COMMUNITY VXELLS
CO
en
IX)
We,1 56
Well 40
Since October 1974
Prior to Initiation
of Controls
Well 22
FIGURE 5 CROSS SECTION THROUGH THE PIEZOMETRIC SUR-
FACE "DRAINAGE DIVIDE"
-------
co
en
co
SCALE 1:9600
• Wells having Improved
water quality
FIGURE 6 EXTENT OF CONTAMINANT MIGRATION AS OF MAY 1978
-------
adsorption of constituents to
the aquifer sands. It is fur-
ther concluded that the nat-
ural process of oxidation of
contaminants is insignificant.
Instituting this alternative
could result in either (a)
abandonment of the Artesian
Water Company Llangollen
Wellfield and development of
another water supply source
equal to the theorized sus-
tained yield (4.5 mgd) or (b)
treatment of the ground water
at the wellhead prior to use.
Since it is presently unknown
whether the contaminated
ground water can be treated
to drinking water standards,
further discussion of this
alternative is limited to
abandonment of the aquifer
and subsequent development
of another water supply
source. This alternative
does not necessarily imply
that the aquifer is to be
abandoned. Rather, it may
be necessary to abandon the
existing wellfield due to its
proximity to the landfill or
add additional treatment,
i.e., carbon adsorption, to
Artesian Water Company's ex-
isting treatment process to
remove the organic fraction.
It also may be possible,
through dilution and adsorp-
tion within the aquifer, to
withdraw this water at some
distance downgradient for
potable water supply without
additional treatment. Ini-
tial capital costs for this
program are approximated at
$3,000,000 with yearly opera-
tion and maintenance costs
of $1,232,000.
II. HYDROGEOLOGIC CONTROLS
This alternative en-
tails controlling the water
entry and exit from the land-
fill by the following means:
A. Precipitation
Infiltration Reduction - The land-
fill surface may be regraded and
covered with a material suitable to
retard infiltration, yet conducive
to vegetative cover. Approximately
80 percent of precipitation falling
on the landfill surface can be
prevented from infiltrating the
refuse. The resultant infiltration
may then average about 32,000 gpd.
B. Interception of Ground-
water Inflow - Groundwater inflow
to the landfill from the Pleisto-
cene sands can be reduced by one
or a combination of the following
methods:
1. A well-point system
2. A series of larger
diameter wells with sub-
mersible pumps.
3. A perforated tile
drain.
4. A gravity-operated re-
charge well system screen-
ed in both the Columbia
and Pleistocene sands.
5. Excavation and drain-
age through an open chan-
nel around the landfill.
It is anticipated that 90
percent of the present ground water
inflow to the -landfill could be
eliminated and thus resultant in-
flow would be approximately 15,000
gpd.
C. Collection of Leachate
Within the Landfill - Much of the
leachate could be collected by
drains constructed in the landfill
itself. These drains would consist
of perforated drain pipe surrounded
with gravel. .These collector pipes
would be inclined toward a central
sump equipped with a small pump to
remove an anticipated 45,000 gpd
to a leachate treatment facility.
It is generally agreed that
the most promising leachate collec-
tion system would consist of sev-
eral recovery wells located within,
directly beneath, or in immediate
proximity of the landfill so as to
354
-------
maximize the collection of
leachate and minimize the
collection of clean water.
This conclusion is tempered to
the need for pump tests in the
landfill area to determine
local well interference and
subsequently determine the
location and number of re-
covery wells necessary to
insure virtually complete
leachate recovery.
In considering this
alternative, one must address
the disposal of recovered
concentrated leachate. It
has been suggested that the
recovered leachate could be
discharged into a County
sewer located in the immedi-
ate proximity of the landfill.
Initial capital costs associ-
ated with this alternative
are approximately $4,450,000
with operation and mainten-
ance costs reaching $990,000
per year.
III. REMOVE THE SOURCE
Several alternatives
have been considered with
respect to removing the
source of contamination, in-
cluding the following:
A. Transport to
Another Landfill - This al-
ternative consists of exca-
vating the entire landfill
and transporting it to ano-
ther site with adequate en-
vironmental safeguards.
The major shortcoming
of this alternative is that
much the same hydrogeologic
control and leachate treat-
ment would be required at
the new site as would be re-
quired at the present site.
Additionally, there are en-
vironmental unknowns and sig-
nificant costs associated
with excavating the landfill.
Initial capital costs for the
transporting alternative are
approximately $14,770,000. Yearly
operation and maintenance costs
would be approximately $970,000.
B. Incinerate - This alter-
native consists of excavation, in-
cineration, and removal of the res-
idue to another site. Of the in-
cinerators investigated, the Union
Carbide Purox System (with or with-
out shredding) and a steam genera-
ting incinerator have been retained
as viable alternatives as long as
fresh refuse to reduce overall
moisture content is available.
Among the considerations to be made
about this alternative are excess-
ive capital costs requiring inte-
gration of the incineration facil-
ity into a regional solid waste
management program, the need for a
supplemental fuel source, the need
for air pollution control measures
and operational difficulties.
Initial capital outlay would range
from $22.7 to $38.3 million. Year-
ly operation and maintenance costs
would range from $1.17 to $1.8
million.
IV. HASTEN DECOMPOSITION
Several alternatives were
considered to hasten in situ de-
composition of the refuse.
A. Recirculation - Spray
irrigation of treated domestic
sewage and industrial wastewaters
has been demonstrated to be an
effective means of waste treatment.
The treatment processes include
aeration while spraying, bacterial
decomposition in the upper soil
layers, chemical adsorption on
soil particles, and chemical uptake
by plants.
Unfortunately, spray irri-
gation of leachate would have sev-
eral major difficulties, including:
1. Airborne odors.
2. Possible chemical
355
-------
toxicity to plants.
3. Clogging of sur-
face soil pores and
plant stomata by iron
and manganese pre-
cipitates from the
oxidized leachate.
4. Clogging of sur-
face soil pores by a
slime derived from
the highly organic
chemical loading in
the leachate.
The highly concentrated
nature of the leachate would
require that it be sprayed
onto the landfill at rates
considerably lower than the
2-inch per week guideline for
treated domestic wastewater
on permeable soils. If the
leachate were recycled by
spreading through infiltra-
tion galleries on the land-
fill surface, clogging of
these galleries by aerated
leachate precipitates would
still be a problem.
Addition of water to
the landfill would generate
large volumes of contaminated
water; some of which would
inevitably leak through the
landfill floor to the Potomac
aquifer. The addition of
water would also raise the
zone of saturation in the
landfill, causing outflow of
leachate to the Columbia sand
north of the landfill by
local reversal of the water
table gradient, and into Army
Creek as it seeps along the
western, southern, and per-
haps eastern margins of the
landfill.
Thus, with no assurance
that recycling water into the
landfill would appreciably
hasten the achievement of
chemical stability of the
buried refuse and considering
the problems discussed above,
the most troublesome of which is
the production of large volumes of
leachate, such a program should not
be initiated.
B. Annelidic Consumption -
This alternative involves the use
of earthworms to metabilize organ-
ics present in the landfill. Since
earthworms can only survive in an
aerobic environment, excavation
will be an integral step in this
process. Metabolized materials
would be removed in a stepwise
fashion after the earthworms have
left a section of the fill. It is
also realized that the costs
associated with earthworms and
earthworm management addresses only
a small fraction of the refuse and
the vast majority of the refuse
must be later disposed of off-site.
Initial capital costs would be
$19.8 million and operation and
maintenance costs would approach
$870,000 per year.
V. PRESSURE MAINTENANCE
Rather than recovering con-
taminated water from beneath the
landfill, another alternative was
to inject fresh water beneath the
landfill to raise the peizometric
surface of the Potomac aquifer to
the landfill base, thus preventing
the downward migration of contami-
nants into the Potomac Formation.
Water could be drawn from elsewhere
in the aquifer for injection at the
landfill site. This alternative
would require a rather extensive
pumping/injection well network with
associated operational problems.
It would be necessary to recover
leachate within the landfill if
this correctional measure was under-
taken .
VI. LANDFILL AERATION
This alternative involves
the bubbling of air into the land-
fill. There are indications that
this process, coupled with minimi-
zation of leachate production, is
356
-------
effective in precipitating
heavy metals and enhancing
aerobic stabilization of
other contaminants. The
precipitated metals could be
of assistance in sealing the
base of the landfill, thereby
reducing the downward migra-
tion of contaminants. Con-
cern has been expressed over
how well air could be dis-
tributed through the refuse,
It was also anticipated that
operational difficulties
would be encountered.
RECOMMENDED ACTION
In November, 1977, a
panel of nationally recog-
nized authorities in the
field of Solid Waste Disposal
reviewed the alternatives de-
veloped by New Castle County.
It was the consensus of these
participants that the follow-
ing measures be instituted to
effectively manage the
problem.
1. Minimize Leachate
Production
a. Minimize pre-
cipitation infiltration
through the refuse by the
application of a relatively
impermeable cover material,
regrading the surface to pro-
mote stormwater runoff, and
revegetation.
b. Minimize ground
water inflow through the ref-
use by excavating a cutoff
trench along the northwestern
boundary of the landfill.
2.
Recovery
Maximize Leachate
a. Construct new
recovery wells within or
closer to the landfill bound-
ary to recover concentrated
leachate before it enters the
Upper Potomac Formation.
b. Phase out existing
recovery well system as downgradient
water quality improves. This action
will ultimately make available
additional water for production
purposes.
To this end, New Castle
County and their consultant, R. F.
Weston, Inc., have developed a five
year implementation plan for which
we are presently seeking funds. It
is hoped that Federal and State
participation will permit the
completion of this project by 1984.
References: LEIS, W. M. and
D. C. CLARK. Control Program for
Leachate Affecting a Multiple
Aquifer System, Army Creek Landfill,
New Castle County, Delaware 1976.
Army Creek
Landfill Technical Roundtable,
November 18, 1978, Summary Proceed-
ings , New Castle County Areawide
Waste Treatment Management Program.
Unpublished Draft,
357
-------
PREDICTING MOVEMENT OF SELECTED METALS IN SOILS:
APPLICATION TO DISPOSAL PROBLEMS
W.H. Fuller, A. Amoozegar-Fard and G.E. Carter
Soils, Water and Engineering
The University of Arizona
Tucson, Arizona 85721
ABSTRACT
Predicting movement of polluting constituents requires the establishment of a model
whether it is "mental", based wholly on experience, or mathematical, based on sophisticated
computerizable equations derived from actual migration data. The Lapidus and Amundson
mathematical model and its solution as proposed was adopted in the prediction of movement
of Cd, Ni, and Zn using parameters from disturbed soil columns and municipal solid waste
leachates to develop a user-oriented predictive tool. The cadmium prototype is presented
in this paper to illustrate its use. Confidence in this approach for application to dis-
posal requires verification under field conditions.
BACKGROUND
The ability to predict movement of
pollutants through soil must become one of
our main goals in disposal operations, since
the soil is considered as the ultimate re-
ceptacle of most of our nation's waste.
Functional predictions are not beyond reali-
ty. The soil scientist, for example, well
demonstrates the potential for such predic-
tions in the field of plant nutrition, soil
reclamation and salt control (Allaway, 1968;
Lisk, 1972; Walsh and Beaton, 1973, USDA,
1954). Unfortunately, direct application
of these studies to migration rates of
trace and heavy metals in waste streams,
particularly the ones involving the conven-
tional cation exchange capacity and mild
extractions (Black, 1965), has not been
found to share the same success (Korte et
al., 1976). In fact, the hydrous oxides of
Fe, Mn, and Al appear to be as influential,
if not more so, to retention of heavy and
trace metals in soils, as cation exchange
capacity (Jenne, 1968; Korte et al., 1975,
1976; and Leeper, 1978). Furthermore,
waste streams involved a broader spectrum of
elements than plant nutrients, and usually
are carried in a wide diversity of solu-
tions which affects attenuation in a domi-
nant manner.
Before predictive designs for disposal
of toxic-metal-containing wastes can be
established, a multitude of factors influ-
encing metal migration rates in soils must
be identified and evaluated. The three
prominent components of the disposal en-
vironment affecting metal migration are
soil, leachate, and specific element
(Fuller, 1977).No two metals respond
(attenuate) identically to the same set of
parameters.
Prediction of pollutant migration
rate through soils may be approached in
several different ways. The most common
method available to us at this time depends
strictly on personal judgment. In the
selection of a suitable site for disposal,
the operator must apply a mental "model"
for the evaluation of the many factors he
keeps in mind as a result of experience.
A mental "model" is the same as a theoreti-
cal and computerized model minus the hard-
ware and is subject to errors of judgment
based on qualitative rather than quantita-
tive information. Thus, a model is a sim-
plified representation of an actual waste
disposal system (van Genuchten, 1978)
whether it exists in the mind from practi-
cal experience or is computerized using
measured parameters and complicated
equations.
358
-------
Another means of predicting pollutant
migration rate is to rank the pollutants
according to soil interactions as illus-
trated by Korte et al. (1976). Although
this method is more quantitative than the
mental "model", it too is a highly quali-
tative procedure. Heavy metal-soil inter-
actions were ranked (Figures 1 and 2) using
11 prominent toxic waste elements, As, Be,
Cd, Cr, Cu, Hg, Ni, Pb, Se, V, and Zn with
10 soils representing 7 of the 10 major
soil orders of the world (Table 1). Cat-
ions and anions were ranked separately
because of differences in migration behav-
ior in different soils. Changes in order-
ing of soils when going from cations to
anions involve a higher rank for soils
having lower pH values and/or higher free
iron oxide content. The soil environment
was strictly anaerobic and the leachate
flow saturated, like that of conditions
under a landfill operation. Predicted
relationships for similar soils and any
situation can be found by using Tables 1
and 2 and typical attenuation curves as
presented for each soil and a given element
(Korte et al., 1976), Figures 3 and 4.
The "models" in the above cases are
highly empirical and seriously lacking in
the precision necessary for long-range pre-
dictions in pollution control. Therefore,
we have selected a mathematical model
patterned after that of Lapidus and
Amundson (1952) in simulating metal migra-
tion through soil. Soil and broad leachate
properties that most influence metal atten-
uation have been quantitatively measured
as previously described in detail by
O'Donnell et al., 1977; Korte et al., 1976;
and Fuller, 1977, 1978. These measurements
are in the form of stochastic functions of
TABLE 1. CHARACTERISTICS OF THE SOILS USED.
Soil
series*
Davidson
Molokai
Nicholson
Fanno
Mohave
(Ca)
Ava
Anthony
Mohave
Kalkaska
Wag ram
Soi
Clay
%
61
52
49
46
40
31
15
11
5
4
1 texture
Silt
%
20
25
47
19
28
60
14
37
4
8
Sand
%
19
23
3
35
32
10
71
52
91
88
Texture
class
US DA
clay
clay
silty
clay
clay
clay
loam
silty
clay
loam
sandy
loam
sandy
loam
sand
loamy
sand
PH
soil
paste
6.2
6.2
6.7
7.0
7.8
4.5
7.8
7.3
4.7
4.2
Cation
exchange
capacity
meq/lOOg
9
14
37
33
12
19
6
10
10
2
Elec.
Cond. of
extract
ymhos/cm
169
1262
176
392
510
157
328
615
237
225
Col umn
bulk
density Porosity
g/cm3
1.89
1.44
1.53
1.48
1.54
1.45
2.07
1.78
1.53
1.89
0.476
0.429
0.460
0.484
0.446
0.478
0.360
0.365
0.404
0.378
Total
surface
area
m2
18,212
23,420
43,019
44,811
50,235
22,325
8,831
16,507
3,542
3,616
Oriented on basis of clay content.
359
-------
INCREASING MOBILITY
co
01
o
t
INCREASING
ATTENUATION
CAPACITY
MODERATE
MOBILITY
Figure 1. Relative mobility of cation-forming elements through soil.
-------
INCREASING MOBILITY
t
INCREASING
ATTENUATION
CAPACITY
MODERATE
MOBILITY !:!:!:i'i\"<\\\
Figure 2. Relative mobility of anion-forming elements through soil.
TABLE 2. DESIGNATION SHOWING TYPE OF CURVE GENERATED FROM EACH COLUMN
Soil
Wagram
Ava
Kalkaska
Davidson
Molokai
Chalmers
Nicholson
Fanno
Mohave
Mohave (Ca)
Anthony
As
A*
C
C
C
E
_t
E
C
B
E
A
Be
C
D
D
D
E
-
E
E
D
E
D
Cd
A
A
C
C
E
-
E
E
D
E
A
Cr
A
C
C
E
E
-
D
C
A
A
A
Cu
E
D
E
E
E
-
E
E
E
E
D
Hg
A
B-C
C
C
D
D
B-C
C
B
D
A
Ni
A
A
B
B
D
D-E
E
E
C
E
A
Pb
B
D
E
E
E
-
E
E
E
E
D
Se
D
E
C
E
E
-
E
E
C
C
C
V
A
B
D
E
E
C
E
D
B
E
A
Zn
A
A-B
B
D
E
-
D
C
B
E
B
t
A, B, C, ... refer to curves in Figure 4.
- designates experiments not run.
361
-------
co
01
ro
1.0 •-
WAGRAM
DAVIDSON
C/Co .5 -
10
15 20
PORE VOLUMES
25
30
Figure 3. Relative migration of Ni through four soils.
-------
CO
CM
U)
C/Co .5 -
TIME
Figure 4. Types of breakthrough curves generated (horizontal scale is approximately 30 days).
-------
specific properties of soil-leachate-metal
systems. The general plan has been to
match theoretical curves describing selec-
ted metal movement in soil columns under
saturated flow conditions with actual data.
Forcing such a match gives rise to specif-
ic values for the theoretical parameters
in the L-A model. For each soil column,
these parameters can be translated direct-
ly into a migration rate for a particular
element (metal).
OBJECTIVE
The major objective is to determine
the long-range, steady-state migration
rates of selected metals contained in
landfill-type leachates and to arrive at
simple formulas that will predict migra-
tion rates.
APPROACH
To examine metal migration rates
under field conditions is difficult and
very time consuming. Useful data for
screening purposes may be obtained through
the employment of soil columns in the lab-
oratory (Fuller, 1977, 1978), while avoid-
ing the problems of field conditions.
Results of this research may then be ex-
posed to field experiment for further
verification and necessary refinements.
We have elected to use soil column studies
in connection with a mathematical model
(O'Donnell et al., 1977).
Many models have been proposed to
describe chemical movement in porous media.
Selim and Mansell (1976) considered solute
flow in finite columns where the solute and
adsorbate followed an instantaneous equi-
librium relationship. Skopp and Warrick
(1974) considered the soil to be composed
of a mobile and stagnant region where the
solute adsorption is a diffusion controlled
process (Figure 5). Van Genuchten and
Wierenga (1976) considered the soil to be
composed of several regions. The solute
adsorption, however, was considered to be
a function of the concentration gradient
between the mobile and stagnant regions.
Models by Selim et al. (1976), and Davidson
et al. (1975), had numerical solutions.
Any of the above models can be used
to describe metal transport in the soil.
All have some unknown parameters which
must be evaluated from experiemntal data.
This involves tedious computer work if the
solutions are complicated. The model and
its solution proposed by Lapidus and
Amundson (1952) has an advantage that it is
simple (relative to Selim and Mansell, 1976,
and van Genuchten and Wierenga, 1976) and
it has an analytical representation in con-
trast to Davidson et al. (1975), and Selim
et al. (1976).
The Lapidus-Amundson mathematical
model is:
JK 1 jm
9t a 3t
92c _3c
iJz7" 3z
(1)
where:
c = concentration in soil solution (M/L )
v = convective (pore water) velocity (L/T)
p
D = diffusion coefficient (L /T)
3 3
a = fractional pore volume of soil (L /L )
n = amount adsorbed per unit volume of soil
(M/L3)
z = vertical distance (L)
t = time (T)
The term 3n/3t describes a linear, non-
equilibrium adsorption and is assumed to be
an/at = 10,0 - K2n
(2)
where K, and K2 are forward and backward
reaction rates (1/T), respectively.
The boundary and initial conditions for
a steady input concentration (c ) are:
c = co
c = 0}
n = 0'
z = 0
t = 0
t > 0
z > 0
(3a)
(3b)
The solution to Eqs. (1) and (2) sub-
ject to (3a) and (3b) is
t
c = c exp(vz/2D)[F(t) + K9 / F(t)dt] (4)
o i 0
where
t _
F(t) = [exp(-K9t)] / {I [2/a)/K1K?3(t-0)]
° ' *
with d = v/4D + K,/a - K?' I is the modi-
fied Bessel function of tne first kind of
order zero. The term c/c0 is referred to as
364
-------
GO
en
ui
X ,
5::::i^
.-3E
—/o-_---_-
-:=r-i
B
MOBILE
- L
Y '^Xxxxxxxyxx^xSTATION A RXr:::::::::::::::::;:;:;:;::x::::::;:;:
INACTIVE
Figures. Idealized flow regime in porous media. (A) Model of flow in soils,
(B) Simplified model, analogous to A. The shading patterns in A and B
correspond.
-------
relative concentration, C, and is a
function of z and t, and contains the par-
ameter v, a, D, K, and K?.
The Lapidus-Amundson model was formu-
lated to describe the effect of longitudi-
nal diffusion in ion exchange and chromat-
ographic columns, where the chemical and
physical parameters are uniform and well
controlled; and the system is relatively
simple. In a soil-leachate system, the
number of parameters increases greatly,
and their interrelationships are much more
complex. The advantage of the Lapidus-
Amundson model is that it combines all
unknown or immeasurable parameters into
three unknowns, D, K-), K2, which can be
determined from the experimental data as
described below. It would be impossible
to determine the spatial interrelation
between all the different physical and
chemical sites in the soil-leachate sys-
tem. By applying the Lapidus-Amundson
model, the net effect of the chemical na-
ture of the leachate on the forward and
backward reaction rates at a multitude of
different adsorption sites is combined in-
to an effective forward and backward
reaction rate for the particular conditions
of the soil-leachate system in the experi-
ment. Similarly, an effective diffusion co-
efficient is determined, or a diffusion-dis-
persion coefficient since the effects of dif-
fusion-dispersion combine in one variable.
Miscible displacement theories and
experimental data indicate the solute
profile is not one of piston displacement,
but rather is a smooth distribution of
concentrations (Nielsen and Biggar, 1962).
In addition, different relative concentra-
tions appear to travel at different rates
(Figure 6). Since the velocity of a par-
ticular concentration ratio is a function
of distance, it follows that the shape of
the experimental breakthrough curve will
also be a function of z. However, the
model predicts that for z > 10 cm the
velocity of a particular relative concen-
tration approaches an asymptotic value;
i.e., steady-state velocity for any rela-
tive concentration has been achieved by a
depth of 10 cm (Figure 6).
Six U.S. soils representing five of
ten major soil orders were used to make
10-cm soil columns which were leached with
two municipal solid waste leachates
(Fuller, 1978) whose salt and iron con-
tents had been altered to varying degrees
(Table 3).
In the application of the model, v is'
estimated by v ,/a where v , is the Darcian
velocity. The variables a, c, CQ are easily
measured. Using these measurable parameters
the values of D, K-| , K2 are selected to give
the closest match between the breakthrough
curve predicted by the model and the exper-
imental breakthrough observed in the column
experiments. A variable metric minimiza-
tion routine (Davidon, 1959) was employed
to find the location of the minimum of the
sum of squares of the differences between
the experimental values, Y(t-j) and the
predicted values C(t.); i.e.,
SSD =
1=1
£Y(t.) - C(t.)]
To obtain the theoretical breakthrough
curve,- the Eq. (4) is integrated numerically
using a 16-term Gaussian Legendre quadra-
ture formula (Abramowitz and Stegun, 1970).
The modified Bessel function, 1Q, is approx-
imated by a Chebyshev polynomial (Abromowitz
and Stegun, 1970). Fifteen equally spaced
points from the experimentally determined
breakthrough curve were used for comparison.
The program used is iterative and may
be continued until the sum of squares of
errors (SSD) is as small as desired. When
this point is reached, the current values
of D, K-j and l<2,are accepted as the true
val ues.
Once the parameters D, K] and l<2 for
a specific soil and a specific element
are determined, the relative concentration
(i.e., c/c0 = C) is a function of z and t
only. Our attempt is, however, to deter-
mine the migration rate of a particular
relative concentration. The question is,
knowing all the parameters (D, K-| , K£, a,
v and c0) for a given soil and a given
element, how loTig will it take for a par-
ticular relative concentration, C, to
reach a given -depth, say ground water.
Mathematically, what we are asking is the
following: Find a function z = z(t) so
that for any time, t > 0, the following is
true:
C(z(t), t) = C'
Thus, for any time t > 0, z(t) gives the
location of the relative concentration C1.
The migration rate of C1 would then be
366
-------
€/Co = C4
co
CTl
Steady-state velocities are
the slopes of these lines
(z > 10 cm)
C/Co = C5
TIME -- t
Figure 6. Trajectories of different relative concentrations. (Plot of z = z(t),
where z = z(t) satisfies c(t,z(t)) = Ci, i = 1,2,3,4,5.
-------
TABLE 3. SOME CHEMICAL CHARACTERISTICS OF LEACHATES REMOVED FROM A MUNICIPAL SOLID WASTE LANDFILL GENERATOR, TUCSON, AZ:
LANDFILL II.
Leachate*
sample
date
8/29/76
9/27/76
10/20/76
11/8/76
12/1/76
1/14/77
2/8/77
pH EC
ymhos/cm
5.4 17,000 11
5.4 11,500 10
5.4 9,000 7
5.4 9,000 7
5.4 9,500 7
5.4 9,500 7
5.4 9,100 7
*
oo Dates during which soil -col
§ detectable limits.
TABLE 4.
Pore
Water
Velocity
3 cm/ day
6 cm/ day
12 cm/ day
24 cm/ day
TOC
,628
,082
,628
,491
,446
,765
,949
Ca
820
815
690
731
760
760
665
Mg
310
270
100
107
108
108
105
umn experiments were
APPARENT Cd VELOCITY AS
z = 10 cm, a = .35, D =
0.1
1.65
3.07
6.02
12.83
0.2
1.55
2.90
5.57
11.94
RELATED TO
2 cm2/day,
0.3
1.48
2.80
5.50
10.84
PORE
Kl =
Na
418
374
300
295
305
295
295
undertaken
K
1060
980
700
700
695
680
670
: Cd
WATER VELOCITY
7 day"1, K2 =
0.4
1.42
2.70
5.37
10.70
0.5
1.36
2.62
5.17
11.10
Fe
ppm —
885
900
640
720
720
720
785
Mn
12.5
12.2
12.0
12.3
12.5
13.0
13.0
(8/29/76-9/27/76).
. (Calculated from
15 day"1.)
c/co
0.6
1.30
2.53
5.00
9.74
0.7
1.24
2.43
4.73
8.55
Zn Co
6.5 0.6
8.0 0.6
6.0 0.5
6.8 0.5
7.8 0.4
9.3 0.4
9.3 0.4
Ni
0.70
0.70
0 50
0.25
0.25
0.25
0.25
Cu, Cd, Cr, and Pb were
equation (lOa)
0.8
1.14
2.28
4.54
8.21
Si P04
33 24
36 31
33 24
26 24
25 24
25 24
25 24
below
with parameters
0.9
0.89
2.01
4.34
8.20
0.95
—
--
4.16
7.62
-------
given by dz/dt.
The function C(z(t), t) = C1 is compli-
cated, therefore it is not possible to
solve for z(t) directly. However, if one
fixes not only the relative concentration
at C1 but also chooses a particular depth z,
it is possible to use an interpolation
scheme to find the time t at which the rel-
ative concentration C1 passes the depth z.
That is, this interpolation scheme deter-
mines one point along the curve z = z(t).
By choosing various fixed depths and using
the same interpolation methods, one obtains
a series of points along the curve z = z(t),
Figure 6. Note that in general z = z(t) is
not a straight line, however, for depths
greater than about 10 cm, the curve becomes
linear for all practical purposes. That is,
it achieves a steady-state condition.
By estimating the steady-state velocity
using the "linear" portion of the curve,
we can determine the effect of change in
the soil-leachate system on migration rates
using multiple regression analysis. The
main characteristics of the soils and
leachates have been measured to identify
the effect of soil and leachate properties
on Cd, Ni, and Zn attenuation. The soil
parameters are, a) texture, b) pH, c) free
iron, d) total dissolved solids or salt
(ION), and e) surface area; for leachates
they are, a) total organic carbon (TOC),
b) inorganic salts (ION), c) soluble Fe,
d) pH.
Using Cd movement as prototype, Table
4 lists the calculated speed of the rela-
tive concentrations for the parameters
z = 10 cm, a = 0.35, D = 2 cm2/day, K-| =
7 day"1 and Kg = 15 day"1. The table en-
tries are Cd velocities as they move past
z = 10 cm for leachate pore velocities of
3 cm/day, 6 cm/day, 12 cm/day and 24 cm/day.
Most of the velocities follow the simple
rule of being halved when the leachate ve-
locity is halved. So we assume that the
velocity of a given concentration ratio is
proportional to the pore velocity of the
leachate and can therefore put the Cd
velocity at a particular relative concentra-
tion C1 and particular fluid speed, s, as:
Vel(C',s) = S(A1-FACTR-1 + A2-FACTR-2 + ...
+ AN-FACTR-N) (5)
The factors FACTR-i, i = 1, ..., N, in Eq.
(5) are the particular soil leachate proper-
ties under consideration.
The application of this type of
equation is of course only valid if the
migration rate is proportional to the pore
velocity of the carrier fluid. Otherwise a
multitude of additional experiments will
need to be undertaken with pore velocity as
an additional variable. But preliminary
experiments indicate that over at least a
limited range, this proportionality is
maintained.
It was determined in the course of our
experiments that it is the ratio of the
forward and backward reaction rates which
is the dominant factor in determining the
breakthrough curve, as opposed to the
absolute magnitude of K-| or l<2. A plot of
the values of K-j and K£ which give an ac-
ceptable fit of the theoretical break-
through curve to the experimental curve
results in a straight line with a slope
equal to K-j/Kg. The line segments gener-
ated for each of the soils reported varied
within a narrow range if at all at differ-
ent fluid velocities. For example, when
flux was changed fourfold (i.e., 3 ml/hr to
12 ml/hr) the K-j/Kg ratios varied according
to a common trend but to a limited extent
for the soils involved (see Figure 7).
Such narrow ranges of differences in slope
of line segments as a result of differences
in fluid velocities are not universal for
all soils. Nicholson sic and Molokai c are
notable exceptions according to soils from
our laboratory not reported here. Never-
theless, for the purpose of model develop-
ment we chose to assume flux is of much
less importance as a variable than other
parameters in the soils used in this re-
search program (Alesii et al. 1979).
The flux dependency of the diffusion
coefficient also needs to be considered. A
true diffusion coefficient should be inde-
pendent of pore velocity (Bresler, 1973).
But since the D term in the Lapidus-
Amundson equation is actually a combination
diffusion-dispersion term, there will be
some flux dependence since the dispersion
coefficient is a function of pore velocity.
The diffusion coefficient has been shown to
be independent of the salt concentration
and dependent on only the water concentra-
tion for all practical purposes in soil-
water systems (Porter et al., 1960; Kemper
and van Schaik, 1966). Kemper and van
Schaik (1966) propose a functional relation-
ship between the diffusion coefficient, D,
and the volumetric water content, 9, as
being Dp(e) = D0aebs; where a and b are
369
-------
24
20
16
12
8
4
0
i- Leach ate F1 ux,
—*— 14.6 cm/da
--0-- 3.7 cm/da
Kalkaska s
(Michigan)
i i i
Wagram Is
(N. Carolina)
t
20
16
-12
8
4
0
Anthony si
(Ariz.-Calif.)
Ava sicl
(Illinois)
20
16
12
8
4
Q
Davidson c
(N. Carolina)
Fanno c
(Ariz.-Calif.!
i i i i i
04 8 12 16 20 24 28 32
04 S 12 16 20 24 28
Figure 7. Line segments for six soils relating forward (K,) and backward (Kp) reaction
coefficients as influenced by flux, where: Rate of Adsorption
8n/3t = K.,c - K2n (Eq. 2).
370
-------
empirical constants, and D0 is the
diffusion coefficient in a free-water sys-
tem. This relationship has been found to
hold when the range of water content cor-
responds to 0.30 to 15 bars suction by
01 sen and Kemper (1968), when b equals 10
and a ranges from 0.001 in clays to 0.005
in sandy loams. These values for a and b
were also successfully applied by Bresler
(1973), and Melamed et al. (1977).
Bresler (1973) reports that many investi-
gators have shown a linear relationship
between the dispersion coefficient Dp, and
the average pore velocity v in the form
&h(V) = A|v| where A is an empirically
determined constant. Bresler (1973) re-
ports values for A of 0.28, 0.39, and 0.55;
while Melamed et al. (1977) use a value of
0.40.
The net result is that the diffusion -
dispersion term, D, is related to Dp and
D as follows : p
D(9,V) = Dp(8) + Dh(V)
D(e.V) = D0aebe + A|V|
(6a)
(6b)
In the experiments which we did, the
values for v were on the order of 0.82
cm/hr in Davidson clay and 1.17 cm/hr in
Wagram loamy sand. Using these flux rates
and the D0 of chloride (0.04 cm2/hr) as a
reference point, it can be seen from the
relation above that Dn is more than an
order of magnitude greater than Dp (0.23
cm2/hr vs 0.0048 cmz/hr in Davidson clay).
In the flux range in which the experiments
were run, the equation predicts that Dn
describes 98% of D. By decreasing the flux
by an order of magnitude, the Du term
should still describe 83% of D. We assume
therefore for the purposes of model develop-
ment that the relationship between the dif-
fusion-dispersion coefficient and flux a
remains linear over the range of interest.
Biggar and Nielsen (1976) present a rela-
tion between the apparent diffusion coef-
ficient, D, and pore water velocity v,
D = 0.6 + 2.93 v1'11 with an r value of
0.795.
We regress the soil and leachate prop-
erties having most effect on migration
rates with the migration rates in the fol-
lowing way: The regression equation is
written one variable at a time with all
variables available to bring into the
equation at each step. The first variable
in the equation is that one which does the
most to explain the variation in the migra
tion rates. The second variable to enter
the equation is that one which does the
most to explain the variation in the migra
tion rates not already explained by the
first variable. Variables continue to be
added in this way until either all varia-
bles are in the equation or until none of
the unused variables are statistically sig
nificant in explaining the remaining vari-
ation in the migration rates.
INTERPRETATION OF RESULTS
The apparent cadmium velocity through
the soil is approximated by the following
set of equations:
V .1 = ^{-1.589 (CLAY) + 0.0196(CLAYxCLAY)
+ 1.385 (lONxSILT)
0.207(CLAYxFeO)
+ 37.667]
- 14.054(FeO) +
0.0122(CLAYxSILT)
V .2 = {-1.472(CLAY) + O.OlS(CLAYxCLAY) +
.183
0
1.238(IONxSILT) - 12.504(FeO) +
(CLAYxFeO) + 0.011 (CLAYxSILT) +
34.022]
V .3 = Q£-I. 401 (CLAY) + 0.018(CLAYxCLAY) +
1.187(lONxSILT) - 11.511(FeO) +
0.168(CLAYxFeO) + 0.011 (CLAYxSILT) +
31.693]
V .4 = |g{-1.347(CLAY) + 0.017(CLAYxCLAY) +
1.166(IONxSILT) - 10.809(FeO) +
0.1 57 (CLAYxFeO) + 0.010(CLAYxSILT +
29.924]
V .5 =
1.121(IONxSILT)
OJ49(CLAYxFeO)
28.391]
.6 = |g{-lJ90(CLAY)
1.069(IONxSILT)
0.149(CLAYxFeO)
27.137]
V .7 =
_ V
^j{-1.184(CLAY)
0.986(IONxSILT)
(CLAYxFeO) + 0.
25.846]
+ 0.016(CLAYxCLAY) +
- 10.245(FeO) +
+ O.OlO(CLAYxSILT) +
+ 0.015(CLAYxCLAY) +
- 10.190(FeO) +
+ O.OlO(CLAYxSILT) +
+ 0.015(CLAYxCLAY) +
-- 9.272(FeO) + 0.134
009(CLAYxSILT) +
To use these equations:
371
-------
1) Estimate clay content (%)
2) Estimate silt content (%)
3) Estimate total ion content of the
leachate (%): This is the sum
of soluble salts and iron in
solution.
4) Estimate free iron oxide content
(%).
5) Estimate the pore velocity of the
leachate (cm/day). (The Darcian
velocity divided by the leachate
filled porosity.)
6) Determine the particular relative
concentration.
7) Substitute the quantities from
steps 1-5 into the equation de-
termined from step 6.
For example, suppose the soil has the
characteristics:
Clay content = 15%, silt content = 2Q%,
free iron oxide content = 1.5%. Suppose
the leachate has total soluble ions 0.08%.
If the porosity of the soil was 0.38 and
the infiltration rate was 0.6cm-Yen^/day,
then the pore velocity would be 0.6/.38=T1.6
cm/day. Suppose the initial cadmium con-
centration in the leachate is 2 ppm and
the concentration limit was 1 ppm. Then
the relative concentration of interest is
0.5. Substitution into the equation for
V .5 yields
3Q-[-1.289(15) + 0.016 (15x15) +
1.212 (0.08x20) - 10.245 (1.5) +
0.149 (15 x 1.5) + 0.010 (15x20) +
+ 28.391]
= 0.290 cm/day
To summarize this point, we have
plotted the data from all the columns run
and have matched theoretical curves to the
observed curves to get individual values
for D, KI and K? for each column. At this
point the only data that have been used
are values of a, v, c0 and the experimental
breakthrough curve from the column. And
for selected relative concentrations we
have migration rates for each column.
To generalize these results from the
few columns run to a more general setting
and also to display the results in an
easily accessible form we make use of mul-
tiple regression equations. One regres-
sion equation for each of the selected
relative concentrations.
LIMITATIONS AND ADVANTAGES OF THIS MODEL
APPROACH
Limitations: Caution must be exer-
cised when using this approximation for
several reasons. First, these were based
on column experiments and not field condi-
tions. Second, although the regression of
velocity with both soil and leachate prop-
erties have an r^ value on the order of
0.82, considerable variation in the actual
velocity values and those predicted by the
regression equations are still present.
These variations are most noticeable in
those soils which are low in both clay and
silt. Here we feel that these regression
equations should not be relied upon for
highly accurate predictions of Cd movement.
Rather they should be used to gain some
idea of the degree to which the selected
soil and leachate properties either con-
tribute to or detract from the Cd transport
velocity.
Refinements in the Model are needed in
order of most increase in predictive capa-
bility per expenditure of a given amount
of development work. These include :
1) Tests with leachates radically differ-
ent from those used to date.
2) Inclusion of more soil and leachate
parameters.
3) Use of more than 15 reference points
on curves (possibly 21; that means
much greater computer costs, but also
means greater predictable precision).
4) More analyses of sensitivity of output
to character of input so it can be
determined where to exercise most
care in collecting input data and
which experimental conditions to con-
trol most closely in developing the
Model such as
--importance of soil bulk density and
pore size distribution.
--nature of total organic carbon.
—identification of the effect of
other hydrous oxides such as Mn
and Al.
--importance of soil-leachate matrix
pH.
Advantages: The Model provides cer-
tain advantages over others:
1) Less complicated than many other
models.
372
-------
2) Does not require infinite information
of attenuation mechanisms which
would need many years to discover
and evaluate.
3) D, KI, and K£ have been derived as
real values from research experi-
mental data making it possible to
apply the model to actual landfill
disposal problems for attenuation of
potentially hazardous metals. In
short, D, K-], and K2 represent real
values beyond armchair theory.
4) The model is most likely to be applied
in its present form to the evalua-
tion of disposal sites because it is
—independent of computers, as far as
the ultimate user is concerned,
—much easier to use the products in
the form of mathematical equa-
tions or tables,
—less demanding for data than other
prominent simulation model
approaches,
—no more limited by the qua!1ty of
input data than other approaches,
and (for a given site) much less
limited by quantity of input
data than other approaches,
--most likely to be used in evaluat-
ing relative migration of a sin-
gle metal at several alternative
sites (because of extrapolation
problems, no claim of predicting
exact movement rate in undis-
turbed soil is made. However,
the model is very likely to es-
timate accurately metal movement
rate in disturbed soils as might
be found when landfills are lined
with clay-soil mixtures or with
native soils).
5) Concerned with nonconservative solutes
(such as metals) and nonconventional
leachates as well as raw, unspiked
municipal solid waste leachates.
6) Not conflicting with the large hydrol-
ogy modeling programs of the USGS.
7) Conveniently and accurately related to
easily measurable physical and chem-
ical properties of the soil-leachate
system.
ACKNOWLEDGMENTS
This research was supported in part
by the U.S. Environmental Protection
Agency, Solid and Hazardous Waste Research
Division, Municipal Environmental Research
Laboratory, Cincinnati, OH. Grant No. R
805731-01 and the University of Arizona,
Soils, Water and Engineering Department.
Arizona Agricultural Experiment Station
Paper No.
The authors wish to thank Rodney
Campbell and Dan O'Donnell for assistance
during the initial phases of the modeling
program and Bruno Alesii and Nic Korte in
the development of some of the Cd migration
data.
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374
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ENVIRONMENTAL IMPACT OF ALTERNATIVE METHODS
OF LANDFILLING ON SURFACE WATER AND GROUND WATER
By:
Grover H. Emrich
William W. Beck, Jr.
A. W. MARTIN ASSOCIATES, INC.
King of Prussia, PA
ABSTRACT
Suitable landfill sites must be utilized efficiently. Methods to
maximize site utilization include solid waste volume reduction (milling
and baling), increased site height (hillfills), and use of existing
excavations (coal strip mines). In this study, these methods are being
evaluated and compared with a standard sanitary landfill to determine
their environmental impact, especially on surface and ground-water
resources.
A balefill, millfill, hillfill, coal strip mine fill and permitted
sanitary landfill have been selected with similar physical and clima-
tological settings. All available data were collected pertaining to
operational history, climatology, hydrology, geology, soils, and
surface and ground-water quality. Data were assimilated and additional
water quality monitoring points were installed. Water quality samples
are now being collected.
INTRODUCTION
Solid waste generation and
disposal represent a continuing
environmental problem throughout
the United States. The amount of
solid waste being disposed on the
land represents 90 percent of the
total municipal solid waste.
This solid waste is disposed in
approximately 15,000 sites of
which approximately one-third are
permitted facilities. The
Resource Conservation and Re-
covery Act (RCRA) requires the
phasing out of open dumps within
the next five years which will
result in the disposal of in-
creased volumes in existing
sanitary landfills and/or the
opening of large landfills.
Suitable landfill sites must
be utilized efficiently. Where
suitable sites are available,
there will be emphasis on placing
more refuse in the site by
increasing its height, i.e.,
hillfills, or through volume
reduction, i.e., milling or
baling. In addition, large
abandoned strip mines offer
potential for the resolution of
waste disposal problems from
major metropolitan areas. The
growing need to completely
utilize the space available in
suitable waste disposal sites
through volume reduction or use
of alternate methods necessi-
tates an evaluation and com-
parison with the standard
sanitary landfill to determine
their environmental impact,
especially on surface and
ground-water resources.
The alternative methods of
waste disposal (millfill,
balefill, hillfill, and strip
mine landfill) represent po-
tential pollution sources as
375
-------
does the standard sanitary
landfill. At this time, however,
the characteristics of these
facilities that promote pollution
or conversely prevent it, have
not been fully documented.
Each method has character-
istics that affect their pollu-
tion potential. Milled refuse
decomposes rapidly producing
large quantities of concentrated
leachate. Millfills however
stabilize in a shorter period of
time with reduced concentrations
and volumes of leachate. Bale-
fills, conversely, are expected
to produce less concentrated
leachate for a long period of
time due to the high degree of
compaction. Strip mine landfills
present interesting and somewhat
unique problems. Pollution due
to acid mine drainage is common
throughout mining regions of the
United States. The added pol-
lution potential of solid waste
in these strip mines combined
with the complex hydrogeologic
system can create serious pol-
lution problems. Hillfills are
also unique in that large volumes
of waste are disposed above the
ground surface. Leachate break-
out between lifts, gas produc-
tion, and structural failure are
among their inherent problems as
well as the potential for large
volumes of leachate.
In order to determine the
environmental impacts of each
type of landfill on water re-
sources, a study is being con-
ducted which will evaluate and
compare volume reduction and
alternative methods of waste
disposal to sanitary landfills.
In addition the study will also
determine site characteristics
that control the occurrence or
non-occurrence of leachate.
These data obtained, through the
study of each type of landfill,
will be utilized to extrapolate
each method's usefulness into
other geographic areas.
SITE SELECTION
Site selection was a criti-
cal element of this study since
there are many variables (depth
to water, geology, hydrology,
refuse-processing, and site
preparation). Site selection
criteria were therefore estab-
lished and included:
1. Availability of back-
ground data.
2. Availability of detailed
engineering and scientific
reports.
3. Availability of the
site.
4. Accessibility of the
site.
5. Status of litigation, if
any.
6. Overall representative
nature of the site.
7. The site must be unlined.
8. The refuse must have
reached field capacity and be
generating leachate.
9. All sites must have
similar climatology.
The site selection criteria
were then applied to each type of
landfill located east of Missis-
sippi River (see Table 1). This
included an evaluation of 15
balefills, 23 millfills, 17
hillfills, and 253 landfills in
coal strip mines. Upon selection
of the five initial landfills for
study, field evaluations were
made at each of the selected
landfill sites to confirm the
existing data, assess the physi-
cal setting, and conduct geologic
and hydrologic evaluations as
necessary. Sources of meteoro-
logical data, additional data
pertaining to the operational
history, and data from the
regulatory agencies were col-
lected during the field evalu-
ation. It was found, after the
initial field evaluation, that
several of the sites did not meet
the criteria and additional sites
were selected.
376
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TABLE 1. Alternative Methods of Solid Waste Disposal in
Selected States East of the Mississippi River
Coal Strip
STATE Balefill Millfill Hillfill Mine Fill
Alabama 2000
Connecticut 0000
Delaware 0100
Florida 0310
Georgia 2200
Illinois 01 6 40
Indiana 0036
Kentucky 00 0 15
Louisiana 0200
Maine 1100
Maryland 0102
Massachusetts 1100
Michigan 0010
Minnesota 1020
Mississippi 0000
Missouri 0006
New Hampshire 0000
New Jersey 1100
New York 6100
North Carolina 0100
Ohio 12 0 56
Pennsylvania 001 120
Rhode Island 0000
South Carolina 0410
Tennessee 0002
Vermont 0000
Virginia 0010
West Virginia 0006
Wisconsin 0 _2 1 0
Total 15 23 17 253
377
-------
Upon final selection of the
five sites for the study, data
gathered during the field evalu-
ation together with other back-
ground data collected in earlier
stages of the project were
evaluated in order to determine
the possible needs for additional
monitoring. The monitoring
system was to delimit ground and
surface water flows and their
interrelationships as well as to
develop or refine water table
maps and limiting flow lines.
Existing chemical data were
analyzed to assist in the place-
ment of additional monitoring
points at each site.
SELECTED SITES
Millfill
The millfill, located in the
northeastern United States, has
been in operation since 1973
receiving an average of 285 tons
of refuse per day. The landfill
operates on a 130-acre tract of
which 45 acres have been filled
(see Figure 1). The fill is up
to 50 feet thick.
The site is located on the
lower slope of a valley wall. It
is underlain by coarse, poorly-
sorted glacial deposits which are
used for daily cover. Ground
water is at a depth from 5 to 15
feet below ground surface and
discharges to a nearby major
river to the south of the site.
The ground water has been moni-
tored by five wells and one
spring since the beginning of the
operation. Two additional wells
were emplaced in the fall of 1978
to augment the existing monitor-
ing network. Collection of
representative ground-water
samples is made after pumping
each well dry and allowing it to
recover. A grab sample is
obtained from the spring.
Balefill
The balefill is located in
the north-central United States
and was in operation for approxi-
mately two years, receiving an
estimated 238,000 tons of baled
refuse during that period. The
landfill utilized 39 acres during
that period (see Figure 2).
The fill is up to 30 feet thick.
The site is located on a
gently-rolling upland area. It
is underlain by extremely coarse,
poorly-sorted glacial deposits
which are used in part for daily
cover. Ground water is at an
average depth of 200 feet below
ground surface and flows in an
eastward direction to a major
river. Ground water at the site
had not been monitored prior to
this study. Leachate from the
site had been collected and
analyzed. Four wells were in-
stalled during the summer of 1978
to implement a ground-water
monitoring system. In addition
to these wells one additional
background well and two leachate
collection points are monitored
for this study. Representative
ground-water samples are collected
after pumping at least two well
volumes from each well. Grab
samples are obtained from the
leachate sampling points.
Hillfill
The hillfill is located in
the north-central United States
and operated between 1965 and
1976 receiving an estimated 750
tons of refuse per day. This
site is approximately 150 feet
high and occupies an area of 39
acres.
The site is located on a
glacial plain adjacent to several
streams (see Figure 3). This
site was constructed utilizing
relatively impermeable clay from
on-site excavations. Daily cover
was provided by both the clay and
glacial till. Ground water is at
a depth from 5 to 26 feet and
discharges to adjacent streams.
The ground water at the site has
been monitored since 1969 utili-
zing nine monitoring wells and
several adjacent water supply
wells. Surface water samples
378
-------
LEGEND
• Monitoring Well
O Spring
ROAD
Hot to Scale
Figure 1. Millfill site plan and location of nonitoring points.
379
-------
CO
CXI
o
\
.10
LEGEND
Monitoring Well
Leochote Discharge
from Test Cell
Limit of Balefill-
Not to Scale
Figure 2. Balefill site plan and location of ircnitoring points.
-------
/* J
( Lake . '
LEGEND
• Monitoring Well
® Surface Water
Sampling Point
Hot to Scoff
Figure 3. Hillfill site plan and location of monitoring points.
381
-------
have also been collected from the
adjacent lakes and streams. Two
additional wells were emplaced
during the fall of 1978 to aug-
ment the existing monitoring
network. Representative ground-
water samples are collected after
removing two well volumes from
the wells by bailing. Grab
samples were obtained from the
lakes.
Coal Strip Mine Landfill
The coal strip mine landfill
is located in the northeastern
United States and has been in
operation since 1968 receiving an
estimated 165 tons of refuse per
day. The landfill operates on a
40-acre tract of which an es-
timated 20 acres have been filled
(see Figure 4). The fill is up
to 80 feet thick.
The site is located near the
top of a hill which had previ-
ously been strip mined. Daily
cover is strip mine spoil.
Ground water at the site varies
from a depth of several feet
immediately below the operation
to 126 feet at the ridge top
above the operation. Ground
water at the site previously had
been monitored through use of one
spring and a hand-dug well.
Surface water was also monitored
at this site. Three wells were
emplaced during the summer of
1978 to monitor ground-water
conditions. These wells in
addition to the existing sampling
points are sampled. Representa-
tive ground-water samples are
collected by removing at least
two well volumes from each of the
wells prior to sampling. A grab
sample is obtained from the
spring, the hand-dug well, and
the stream.
Permitted Sanitary Landfill
The landfill is located in
the northeastern United States
and was operated between 1971 and
1975 using the trench method. It
accepted an estimated 112 cubic
yards of domestic refuse and
demolition debris daily. The
landfill utilized a total of 22
acres with waste being deposited
in thicknesses up to 20 feet
(see Figure 5).
The site is located on a
topographic and hydrologic
divide. The area around the
landfill slopes steeply down
toward two intersecting creeks.
Twenty to forty feet of poorly-
sorted, stoney clay till under-
lies the site. Bedrock is a
gray, dense, low permeability
shale. The till was used for
both intermediate and final
cover. Ground water is 40 to 50
feet below ground surface and
discharges to the adjacent
creeks. The ground water has
been monitored by six wells
completed around the landfill.
Two stream sampling points have
also been monitored during and
after the period of operation.
Each well is pumped dry and
allowed to recover before
collection of ground-water
samples in order to assure
representative samples. Grab
samples are obtained from the
surface water monitoring point.
SAMPLE COLLECTION - MONITORING
Selection of chemical
parameters for analysis was
based on the materials deposited
at the site and from the inter-
pretation of existing data.
From these two sources, it was
determined which ions are most
likely to be migrating from the
site and will be useful indica-
tors of contamination. The
following chemical analyses are
being performed on each sample:
alkalinityt acidity, sulfate,
chlorides, total solids, total
dissolved solids, nitrate nitro-
gen, amonia nitrogen, total
phosphate, total kjeldahl nitro-
gen, copper, iron, manganese,
sodium, lead, zinc, total or-
ganic carbon, COD. In addition
pH, specific conductivity, and
temperature are measured in the
field when the samples are
collected. Samples are being
382
-------
co
CO
CO
LEGEND
• Monitoring Well
• Surface Water Sampling Points
O Spring
\
Sampling
, 'Point Located . /
Further Downstream ®'/
Not to Seal*
Figure 4. Coal strip mine landfill site plan and location of monitoring points.
-------
Approximate
Limit of
Landfill Shed-id\\
Bulky Waste
Fill
Landfill R-operty
500ft.
LEGEND
Monitoring Well
Surfoc« Water
Sampling Point
Figure 5. Permitted sanitary landfill site plan and
location of monitoring points.
384
-------
collected quarterly over a 12-
month period at each of the five
selected sites. Each sample is
coarse-filtered in the field,
preserved in accordance with EPA
recommended methods, and shipped
to a private laboratory for
analysis within 24 hours of
sample collection.
All chemical and hydrologic
data are being stored in a
computer to insure rapid and
accurate recall. As needed,
statistical tests will be applied
to the data to determine varia-
tions occurring between sites.
In order to assess the
effectiveness and usefulness of
each of the five disposal me-
thods, it will be necessary to:
(1) reduce both historical and
current chemical data to a
meaningful format; (2) use hydro-
logic and meteorological data to
develop a water budget; and
(3) determine the pollution
potential and possible areas of
applicability for each method.
The impact of each site on
the environment is a function of
the quality and quantity of
leachate generated, the overall
attenuation characteristics of
the site, and hydrogeolic regime
at the site. The type of land-
fill operation is expected to
control the rate and strength of
leachate generation; the siting
and engineering of each disposal
site will govern the attenuation
and hydrogeologic effects.
CONCLUSIONS
Data about millfills, hill-
fills, balefills, and landfills
and coal strip mines have been
collected throughout the eastern
United States. Site selection
criteria have been developed and
utilized in the selection of five
sites. Background data at each
of these five sites have been
collected and the existing moni-
toring network evaluated. Addi-
tional monitoring points were
located where necessary to aug-
ment the existing network. The
first set of samples from all
sites was collected late fall of
1978. Sample collection will
continue on a quarterly basis for
one year.
ACKNOWLEDGEMENTS
The work which is reported
herein is being performed under
Contract #68-03-2620, Donald E.
Banning, Project Officer.
385
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PREDICTING LANDFILL GAS MOVEMENTS IN SOIL AND
EVALUATING CONTROL SYSTEMS
Charles A. Moore
Department of Civil Engineering
The Ohio State University
Columbus, Ohio 43210
INTRODUCTION
The Ohio State University has been in-
volved in developing analytical tools to
be used by the practicing engineering pro-
fession for the design of sanitary land-
fills to reduce methane migration potential.
Figure 1 shows a flow chart delineating the
major tasks and their sequencing. The de-
tails of these studies have been described
in the publications listed in the bibliog-
raphy.
The purpose of this paper is to pre-
sent a case history involving prediction
of methane migration at a proposed landfill
site. The prediction will be based upon
the use of the design charts published by
Moore (1976) and by Moore and Jayko (in
press); however, the site geology does not
allow for using the charts in a direct
manner. Rather, approximations are requir-
ed.
DESIGN EXAMPLE
Figure 2 shows a hypothetical site
plan for a landfill. The geologic strati-
graphy (Figure 2a) consists of a partially
saturated clay layer, the top of which is
at elevation 500 feet. The clay layer is
overlain by 50 feet of uniform sand, which
is in turn overlain by 3 feet of partially
saturated clay. The lower clay layer sup-
ports a perched water table rising to
elevation 515 feet. Erosion has resulted
in the formation of a bluff 23 feet high
which will serve as one side of the land-
fill. The natural bluff slopes at 2 hori-
zontal on 1 vertical.
The landfill will be placed adjacent
to the bluff with its base coinciding with
the erosion plane abutting the bluff (elev.
530). The top of the landfill will be at
elevation 570 feet.
Approximately 310 feet east of the
eastern edge of the landfill, a river has
cut a valley creating a bluff extending to
below elevation 500 feet. Approximately
100 feet west of the western edge of the
landfill, a fault has resulted in sound
limestone being uplifted to form the base
of the erosion plane at elevation 530 feet.
In plan view, the landfill occupies
4.5 acres and is shaped as shown in Figure
2b.
It is desired to eval ute the methane
migration potential of the site by the use
of design charts.
Life being what it is, the conditions
at this site do not apparently coincide
with the conditions assumed in developing
the design charts published by Moore (1976)
or Moore and Jayko (in press). Thus it
will be necessary to use the charts in an
approximate manner.
Initially, we must determine if the
charts are appropriate to use at all. The
charts were developed assuming that the
flow of methane was purely diffusional;
that is, the pressure within the landfill
is atmospheric. Such is likely to be the
case if the landfill is well vented, either
through a reasonably pervious cover, or
through artificial vents such as pipes.
The charts were also developed based upon
70% mole fraction methane in the landfill
for a period of 5 years, after which time
the methane concentration in the landfill
reduces to zero. Seventy percent methane
represents an upper theoretical limit;
whereas, 5 years decomposition time repre-
sents a relatively short decomposition
time. Nevertheless, the current state of
knowledge concerning methane generation
within landfills suggests that the assump-
tions made in developing the charts are
386
-------
develop computer codes
for general solution
I
prepare user's manual
for applying codes
to specific sites
derive equations
for gas flow around
sanitary landfills
I
verify equations
experimentally
i
develop charts
for planning
and design
develop computer codes
for design of control devices
evaluate practicality
of several configurations
for control devices
Figure 1 - Flow chart describing research program.
387
-------
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appropriate for many U.S. landfills.
In order to apply the charts we must
establish the geometric conditions and
boundary conditions. Reference to Figure
2 shows that the site geometry is complex
and does not comply with the simple geome-
try assumed in developing the design charts.
However, it is possible to adapt the charts
to suite the site geometry shown. The two
sides (East and West) of the landfill are
clearly dissimilar: The East side consists
of sand capped with clay. Moreover, the
landfill is located both above and below
ground. The side of the landfill slopes,
and a bluff exists of little over 300 feet
from the landfill edge. The West side con-
sists of uncapped sand, and the landfill
is located entirely above grade. A lime-
stone deposit is encountered 100 feet West
of the edge of the landfill. Finally, in
plan view the landfill is not circular.
To resolve this dilemma, one can make
the following approximations:
One can calculate an equivalent radius
of the landfill, r, by assuming a circular
landfill having an area equal to that of
the existing landfill:
Tr(r)2 = 4.5 acres = 2 x 105
square feet. Thus, r = 250 feet.
Now evaluate the methane migration
distance on the East and West sides inde-
pendently. Comments will be made later on
the consequences of this action.
For the East side, one must now address
the issue of the above grade portion of the
landfill. This, however, is not a dilemma
at all. Because the gas flow is diffusional
only, that portion of the landfill above
grade has no effect on the problem and can
be ignored. Thus, the depth of the landfill
should be taken as
df = 533 - 530 = 23 feet.
The next problem is the sloping side
of the landfill-soil interface. To circum-
vent this, one must assume that the edge
of the landfill is located at the point of
intersection of the landfill and the
ground surface (point A in Figure 2). The
landfill-soil interface will be assumed
vertical; thus, in effect, a portion of the
soil is assumed to be replaced by solid
waste. The effect of this assumption will
be to overestimate the methane migration
distance somewhat. Thus, one can now de-
termine the radius of the fill to be
rf = r = 250 feet.
One must now determine the radius to
the soil boundary, rs. Reference to Figure
2 shows that the bluff formed by the river
valley constitutes a pervious boundary of
zero methane concentration. The sloping
bluff will be approximated as being verti-
cal ; thus, rs = 250 + 310 = 560 feet.
The depth to an impervious boundary,
ds, will simply be the depth to the ground
water table. (The effect of the depressed
surface rear the bluff is ignored). Thus,
ds = 533 - 515 = 38 feet.
Having defined the geometric condi-
tions, it is now necessary to select the
proper chart to apply to the problem. The
soil is a sand and, therefore, coarse
grained. The bluff at the river valley is
in free contact with the atmosphere, and
thus constitutes a pervious boundary. The
conditions at the ground surface present
an additional problem. The effect of the
clay layer will be to impede venting of
methane to the atmosphere, however, it
does not constitute a perfectly impervious
layer. Nevertheless, imperviousness will
be assumed, recognizing that this approxi-
mation results in overestimating the dis-
tance of methane migration.
Thus, the appropriate chart to use is
Figure A2 from Moore and Jayko (in press)
which is reproduced in Figure 3. The
values to be used in entering the chart are
r. = 560 feet
d = 38 feet
= 250 feet
= 23 feet
38
23
560
250
= 2.24.
The chart is entered at ds/df =1.65. We
then move vertically until an interpolated
curve for rs/rf = 2.24 is encountered.
Finally, we move horizontally to obtain
rt/rf = 1.88. Thus, the maximum distance
of migration of the 5% methane contour will
389
-------
OJ
<£>
O
BEDROCK
I i ! I ' T- I -V i
COARSE GRAIN
t- SOIL
values on curves
are rs/rf
Figure 3 Design chart for granular soil (impervious ground surface
and pervious radial boundary). From Moore and Jayko
(in press).
-------
be
rt = 1.88 rf = 1.88 (250) = 470 feet.
This places the 5% contour extent at 470 -
250 = 220 feet beyond the edge of the land-
fill.
We now turn to the west side of the
landfill. Here the landfill exists en-
tirely above grade. As with the east side,
the portion above the ground is ignored,
therefore df = 0.
The radius of the fill is simply rf =
r = 250 feet. The radius to the soil
boundary will be taken as rs = 250 + 100 =
350 feet under the assumption that the
sound limestone encountered at the fault
constitutes a gas impervious boundary.
As on the east side, the depth to an
impervious layer is taken as the depth to
the groundwater table. Thus ds = 530 -515
= 15 feet.
Having defined the geometric condi-
tions, it is now necessary to choose an
appropriate chart. The soil is sandy and,
therefore, coarse grained. The limestone
constitutes an impervious radial boundary.
The uncapped sand-atmosphere interface is
pervious. Thus the appropriate chart is
Figure A.3 from Moore and Jayko (in press)
which is reproduced as Figure 4. The
values to be used in entering the chart
are
rs = 350 feet rf = 250 feet
d = 15 feet cL = 0 feet
a T
15
350
250
= 1 .4.
The value of ds/df = «> could present a
problem; however, reference to Figure 4
shows that for each value of rs/rf, the
curves are essentially horizontal for ds/
df greater than approximately 4.0. Thus
ds/df = 5.0, the highest value on the
chart, is an appropriate value to use for
ds/df = oo. Entering the chart at ds/df =
5.0, we move up to rs/rf = 1.4 (we lucked
out, because there is a curve for 1.4,
thus we need not interpolate) and then
over to find rWrf = 1.242. Thus the maxi-
mum distance of migration of the 5% methane
contour will be
rt = 1.242 rf = 1.242 (250) = 310 feet.
This places the 5% contour extent at 310 -
250 = 60 feet beyond the edge of the land-
fill .
Thus the 5% methane contour extends
220 feet to the east of the landfill and
60 feet to the west of the landfill.
One must now address the issue of the
separate treatment of the two sides of the
landfill. The concept upon which the de-
sign charts are abased involves exact
symmetry around the landfill. Considering
first the east side, the solution giving a
migration distance of 220 feet would have
presumed an equal migration distance on the
west side. The fact that the actual mi-
gration distance on the west side is only
60 feet means that, as far as the east side
is concerned, there is less methane on the
west side than would be anticipated. There-
fore the migration distance predicted for
the east side based on the simplifying
approximation will overestimate the actual
condition somewhat.
The converse arguement for the west
side would indicate that the simplifying
assumption results in underestimating the
actual gas migration distance on the west
side.
Finally, one must discuss the conse-
quences of assuming the landfill to be cir-
cular in plan view. Reference to figure Ib
shows that in actuality the landfill is
longer in a north-south direction than in
the east-west direction. The assumed
radius of 250 feet results in overestimat-
ing the methane migration distances in the
east and in the west directions. Had es-
timates been made in the north and south
directions (impossible, from a practical
point of view), they would have underes-
timated the methane migration distance.
Figure 5 shows a plan view delineating this
author's approximation of the 5% methane
migration contour around the landfill based
upon the calculations performed above. The
following factors influenced the decisions
made in drawing the contour.
Directly to the east of the landfill,
the basic distance was taken to be 220 feet
391
-------
co
U3
ro
1.36
i BEDROCK
[•_•_ I I i I i i- ••! .. i -i
COARSE GRAIN SOIL
values on curves
Figure 4 Design chart for granular soil (previous ground surface and
radial boundary). From Moore and Jayko (in press).
-------
x- * - ^ 5% methane contour
60
210
I
to
-------
from the edge of the fill. The following
factors supported a reduction in this
distance:
1.
2.
3.
4.
5.
the clay cap is not totally impervious
as assumed,
the clay cap was assumed to be infini-
tesimally thin; whereas, it is actually
3 feet thick,
the landfill is narrower in the east-
west direction than assumed,
the methane migration distance on the
west side is only 60 feet, and
the sloping landfill-soil interface
was accomodated by replacing some soil
by sol id waste.
Directly to the west of the landfill,
the basic distance was taken to be 60 feet
from the edge of the fill. The following
factor supported a reduction in this
distance:
7.
1. the landfill is narrower in the east-
west direction than assumed.
The following factor supported an increase
in this distance: 8.
1. the methane migration distance on the
east side is 220 feet (considerable
greater than 60 feet).
9.
The factor dictating increasing the 60 foot
distance on the west side was judged to
take precedence over the factor suggesting
a decrease. Increasing the distance from
60 to 70 feet was pure engineering intui- 10.
tion. The author would not be at all sur-
prised if field measurements disclosed
that the 5% methane level migrated all the
way over to the limestone.
REFERENCES 11.
1. Alzaydi, Ayad A. "Flow of Gases
Througn Porous Media," Ph.D. disser-
tation, the Ohio State University,
University Microfilms (Ann Arbor, MI.) 12.
No. 76-3367, 1975.
2. Alzaydi, Ayad A., Charles A. Moore
and Iqbal S. Rai. "Combined Pressure
and Diffusional Transition Region Flow
of Gases in Porous Media," AlChE Jour-
nal, Vol 24, No. 1, January, 1978.
Moore, Charles A. "Theoretical Ap-
proach to Gas Movement Through Soils,
Gas and Leachate from Landfills: For--
mation, Collection and Treatment," U.
S. EPA Report No. EPA-600/9-78-004,
held at Rutgers University, March 1975.
Moore, Charles A. and Iqbal S. Rai.
"Design Criteria for Gas Migration Con-
trol Devices, Management of Gas and
Leachate in Landfills," U.S. EPA Report
No. EPA-600/9-77-026, held at Univ. of
Missouri, March 1977.
Moore, Charles A. and Ayad A. Alzaydi.
"Development of Predictive Models for
Landfill Gas Movement - Theoretical
Considerations," (in press), Report
submitted to U.S. EPA.
Moore, Charles A. and Iqbal S. Rai.
"Development of Predictive Models for
Landfill Gas Movement - Computer Pro-
gram Development," (in press), report
submitted to U.S. EPA.
Moore, Charles A. and Katherine L.
Jayko. "Design Charts for Gas Move-
ment Around Sanitary Landfills," (in
press), report submitted to U.S. EPA.
Moore, Charles A. and John E. Lynch.
"Design Criteria for Landfill Gas Mi-
gration Control Devices," (in press)
report submitted to U.S. EPA.
Moore, Charles A. "Summary Report on
Sanitary Landfill Gas Movement and
Control," (in press), report submitted
to U.S. EPA.
Moore, Charles A. and Ronald M. McOm-
ber. "Conceptual Designs for Gas Mi-
gration Control Systems for City of
Hopkins Landfill," (in press), report
submitted to U.S. EPA.
Moore, Charlies A. "Landfill Gas Gen-
eration, Migration, and Control," Cri-
tical Reviews in Environmental Con-
trol, Vol. 9, Issue 2, May, 1979.
Moore, Charles A., Iqbal S. Rai and
Ayad A. Alzaydi. "Methane Migration
Around Sanitary Landfills," J. ASCE,
Geotechnical Engineering Division, Vol.
105, No. GT2, Proc. Paper 14372, Feb.
pp. 131-144, 1979.
394
-------
13. Moore, Charles A. "Conceptual Designs
for Gas Migration Control Systems for
the City of Hopkins Landfill," First
Annual Conference for Applied Research
and Practice on Municipal and Indus-
trial Waste at Madison, Sept. 13, 1978.
14. Rai, Iqbal S. "Mathematical Modeling
and Numerical Analysis of Flow of Gases
Around Sanitary Landfills," The Ohio
State University, University Microfilms
(Ann Arbor, MI), No. 76-10030, 1975.
15. Rai, Iqbal S. and Charles A. Moore.
"User's Manual for Computer Codes for
Gas Movement Around Sanitary Landfills,"
(in press), report submitted to U.S.
EPA.
16. Rai, Iqbal S. and Charles A. Moore
"Development of Predictive Models for
Landfill Gas Migration Control Devices,"
(in press), report submitted to U.S.
EPA.
395
-------
GAS MIGRATION AND MODELING
by
T. W. Constable, G. J. Farquhar and B. N. Clement
University of Waterloo, Waterloo, Ontario
ABSTRACT
A research program is currently underway to measure pressures and gas compositions
both in a landfill and at its periphery, and to use the results to estimate gas produc-
tion rates in the landfill and to calibrate a gas migration model.
Gas production rates will be estimated by monitoring gas compositions and pressures
before, during and after application of a zone of negative pressure within the landfill.
This zone is provided by means of a gas withdrawal well installed vertically in the
landfill and vented to a pump. Results from a trial pumping test are presented.
Several sets of pressure and concentration measurements have been obtained at the
migration study location. A typical set of data is presented, and shows the influence
and effectiveness of a forced venting system in operation at the site. The data from
all migration studies will be used to examine seasonal trends in migration patterns, and
to calibrate a gas transport model. An example of the model's ability to simulate field
conditions is given.
The influence of atmospheric pressure on gage pressure readings is demonstrated.
It is suggested that barometric pressures in the field be obtained at the same time as
gage pressures, and that all pressures be converted to absolute pressures for purposes of
comparison.
1. INTRODUCTION
The decomposition of organic matter
in the absence of oxygen results in part
in the production of gaseous by-products.
Under conditions usually encountered in
sanitary landfills, these gases consist
primarily of methane (CH^) and carbon
dioxide (C02). Small amounts of ammonia
CNH3) ,hydrogen sulphide (T^S), nitrogen
(N2), hydrogen (H2) and carbon monoxide
(CO) can also be produced (Farquhar and
Rovers, 1973).
Except in one or two isolated inci-
dences, gas production in sanitary land-
fills received little attention until the
early 1970's. Recently however, the po-
tential hazards of these gases at land-
fills have become a major concern. While
some recognition has been given to the
acidification of groundwaters from the
dissolution of C02 as a problem with res-
pect to water quality, the major focus of
attention has been directed toward CH^ and
the hazards presented by combustion.
To date there have been many cases
reported where CE^ produced in sanitary
landfills has migrated into adjacent prop-
erties and has created explosive condit-
ions when in concentrations ranging between
5% and 15% volume in air. Where explos-
ions have occurred, property damage has
been substantial. In some cases there has
been personal injury, even the loss of
life.
In response to this danger, regula-
tory agencies have begun to recommend the
installation of systems for venting or
diverting migrating gases. In some cases
these measures have been effective. In
others, they have not. The problem app-
ears to be that the patterns of gas prod-
uction and migration are poorly understood.
This stems in part from an incomplete
knowledge of the properties of the gas as
396
-------
produced in the landfill and the inability
to anticipate the manner and extent to
which it migrates in the soil.
A research program conducted by Water-
loo Engineering Associates Inc. in con-
junction with the University of Waterloo
was begun in April, 1978 to address these
problems. The scope of this investigation
and the results obtained to date are pres-
ented below.
2. OBJECTIVES
The objectives of the investigation
are
1. To study the extent of methane prod-
uction in landfills with respect to
a) gas composition,
b) gas pressure and
c) gas flow rates ;
2. To measure the patterns of gas move-
ment into soils adjacent to landfills;
3. To calibrate a previously developed
gas flux model for a specific land-
fill site; and
4. To demonstrate the model's capability
to predict gas concentrations in the
soil
a) under typical variations in
climatic conditions and
b) for various gas control mech-
anisms such as vents, diver-
sions and confinements.
These objectives are being pursued
through implementation of the experimental
program described in subsequent sections.
3. GAS PRODUCTION IN LANDFILLS
3 . 1
of _Exp er i.ment_al. Work
The objective of this phase of the
work is to provide information about gas
composition, pressure and production in
sanitary landfills . Such information is
essential to both the analysis of gas mi-
gration into adjacent soils and the assess-
ment of gas recovery potential at landfills.
Of the three measurements, gas production
is the most difficult. Most investiga-
tions of this property have been on a lab-
oratory scale. Actual field measurements
are sparse.
This study is examining the extent of
landfill gas production and its variation
through the review of published literature
and the collection of field data. Estim-
ates of gas production rates will be ob-
tained by monitoring gas compositions and
pressures before, during and after appli-
cation of a zone of negative pressure with-
in the landfill. This zone is provided by
means of a gas withdrawal well installed
vertically in the landfill and vented to a
pump.
3 . 2
Estimates of gas generation rates for
landfills given in the literature vary
widely, from values of 2.2 I/kg dry weight
(Coe, 1970) to 250 I/kg dry weight (Mande-
ville, 1976; De Walle e_t a^. , 1978. The
characteristics of landfill sites often
vary considerably, so that field studies
must be conducted to determine the actual
production rate at a given site.
Several field studies similar to the
one described herein have been conducted
to determine gas production rates. As in
this study, gas was removed from the land-
fill at various flow rates via a gas with-
drawal well, and gas production rates were
estimated based on the steady-state flow
rate.
Gas generation rates determined at
four landfills in California are reported
in Table 1. It can be seen that gas gener-
ation rates varied between 22 and 45 ml/kg-
day. DeWalle et^ _a!L. (1978), using sealed
containers filled with different amounts
of solid waste and maintained at different
environmental conditions, obtained average
gas production rates over a 300 day period
ranging from 0.29 to 18.1 ml/kg-day. Based
on these experiments, they concluded that a
gas production rate of 20 ml/kg-day can be
obtained at most landfills, with higher or
lower production rates obtained with high-
er or lower moisture contents. Their sugg-
ested rate of 20 ml/kg-day is comparable
with the rates reported in Table 1.
Blanchet (1976) suggested that the
optimum gas withdrawal rate from pumping
wells is 0.09 m3/min per m of well. This
rate is comparable to the rates reported
for the last three landfills in Table 1.
397
-------
Table 1 GAS PRODUCTION RATES AT CALIFORNIA LANDFILLS
Palos
Verdes
Depth of Well (m) 33.5
Radius of Influence (m) 76.
Mission
Canyon
30.
Sheldon-
Arleta
38.
76.
Mountain
View
12.
40.
Gas Flow Rate
(m-Vmin)
8.5
2.3
4.1
1.4
Dry Density (kg/m3)
714.
595.
595.
Gas Production Rate
a) ml/kg-day
b) m^/min per m
of well
30.
0.25
0.08
22.
O-.ll
45.
0.12
Reference
Schuyler,
1973
Schuyler,
1973
City of
Los Angeles,
1975
E.P.A.,
1977
3. 3 Ijij^t jrumentatjioil and_ Moni_tp_ring_of_ Site
The three-dimensional nature of the
negative pressure zone caused by pumping
from the gas withdrawal well is measured
with nests of gas sampling piezometers
located on three radii from the gas with-
drawal well, each nest consisting of five
piezometers at various depths. A plan
view of the gas production site is shown
in Figure 1. Piezometer nests 1 through
8 have been installed to date.
The gas withdrawal well is construct-
ed of 4" PVC pipe, with the bottom 3.3 m
of the pipe perforated and wrapped with
fibreglass tape to provide screening.
A typical piezometer nest install-
ation is shown in Figure 2. The bottom
piezometer is constructed of 1/2" PVC pipe
while the other piezometers are 1/4"
polyethylene tubing. The tubing is attach-
ed to the PVC pipe which provides a rel-
atively rigid central core and aids in
the installation of the piezometer nest.
A length of 1/4" tubing is also connected
to the top of the 1/2" PVC pipe. Each
piezometer is perforated over the bottom
0.6m and wrapped with fibreglass tape.
The piezometers are surrounded by pea
gravel in the monitoring wells, and sep-
arated by concrete plugs. Each of the
1/4" tubes are of different colours, with
each colour corresponding to a relative
depth in a well. . Use of coloured tubing
provides a means of instant recognition
of piezometer placement, and prevents
errors caused by monitoring incorrect
depths.
The tubing is routed to a central lo-
cation at the gas withdrawal well through
buried trenches. Approximately 2 m of the
tubing leading from each piezometer is
coiled around the gas withdrawal well with-
in a partially buried 0.6 m diameter corr-
ugated metal pipe with a removable locked
top. This provides a secure arrangement
for storage of the tubing and allows all
piezometers to be monitored from a single
location.
At the commencement of a pumping test,
each piezometer is connected via the 1/4"
tubing to a monitoring board, as shown in
Figure 3. Each tube has a separate on/off
val-ve to allow the piezometers to be sealed
in the intervals between measurements. The
monitoring board is also equipped with a
398
-------
oo
ID
Ground surface^
Blue
x ,-
•f
'•'•
__
in
^
r
_
*;
i4_
\A"0 Polyethylene Tubing
/ i— 0.6 m Trench Depth
/ i __
—
^'
^a
r,€F^
dl^
-^
hi'-,"!1^^
?:
:-"••: I-'
asf.jii
*T;f^"
''.*."'- '
\-
n&*
. '
:...V
s!4
tj?
S
it
•il
x8^^
"%£ '&J,*&1S
^-r-r-.- -~y--.^-~— •=- Unit
-l/2"0 PVC Central Cote
Green
sJ™^
Perforations — — i*i''"* | °
Yellow fl3a^*S'e"~~^^l-V- |
f^'1312
V} PIEZOMETER DETAIL '
r
Red ^ Conaete Plug
(^ Pea Gravel Screen
O Backfill
White Colour of tubing indicates
relative depth of Piezometer
i^ (Nnt tn $C3\*\
76 mm
Well Diameter
11
-o-
• In-place Piezometer Nest
O Future Piezometer Nest
•6
Scale-1:360
Figure 2-TYPICAL PIEZOMETER NEST INSTALLATION
Figure 1 -PLAN VIEW OF CAS PRODUCTION SITE
-------
(a) FRONT VIEW
-? 30 Valves
OOOOQO
0 0
0 0
O 0
0 O
0 0
o o
0 0
0 0
_J
0 0
0 0*
o o
0 0
fp"
ant-tube U-tube
anometer Manometer
0.9m
(b) SAMPLING TECHNIQUE
- "WT Stopcock
Valve
Latex Tubing
1/4" Polyethylene
Tubing
30cc'Plastipak'
Syringe
3/4" Plywood Board
Quick-disconnect
Coupling
Manometer
j Tubing
Slant-tube Manometer
Figure 3-MONITORING BOARD
slant tube manometer which can read press-
ures (positive or negative) from Q.Q1 to
3 inches of water. Pressures are obtained
by connecting the appropriate valve to the
manometer and turning the valve on. Such
an arrangement allows pressures in the
landfill to be monitored very quickly,
even for a large number of piezometers.
Gas concentration samples are collect-
ed in rPLASTIPAK' disposable syringes, 30
cc capacity, with 'Luer-Lok' tips. First,
a length of tubing leading to a piezometer
is purged by applying an aspirator to the
appropriate opened valve. Then the valve
is closed, and the needle of a syringe is
inserted into the latex tubing at the rear
of the monitoring board. A sample is
withdrawn, and the plunger in the syringe
is allowed to equilibrate before the need-
le is removed from the tube. Difficulties
are sometimes encountered when attempts
are made to withdraw samples from a tube
under a large negative pressure. The neg-
ative pressure pulls the plunger back into
the syringe and prevents removal of a samp-
(Not to scale)
of gas.
The syringe needle is then removed and
quickly replaced with a rubber serum stopp-
er. Since the stoppers are self-sealing,
samples required for gas analyses in the
laboratory can be removed from a sample
syringe by means of a 1 cc syringe inserted
in the stopper.
Control experiments using the 'PLAST-
IPAK' syringes have shown that an insig-
nificant amount of leakage occurs during
the interval from sample collection to
analysis. To ensure acquisition of reli-
able results, analyses are conducted in
the laboratory as soon as the samples are
returned from the field.
Samples are analyzed in the laboratory
using a Fisher Model 1200 Gas Partitioner.
Gases analyzed include methane, nitrogen,
oxygen and carbon dioxide.
400
-------
Or
u-0.5
a
-1.5
f.=
3= or-
13.7
50 100 150 200
Time (mm)
250 300
Figui* 4-TEMPORAL VARIATION IN PRESSURES IN PIEZOMETER
NEST ft6 (NOV 26, 1978)
3 . 4
Gage_Press u_re_
Problems were encountered with, respect
to interpretation of the pressure readings
in the landfill after completion of a
preliminary investigation of the gas pro-
duction site on November 13, 1978. It was
observed that pressures at individual piez-
ometers displayed considerable variation
over the three hour sampling period, with
pressures ranging from approximately -1 to
+0.5 inches of water, as measured by the
slant tube manometer. It was concluded
that pressure readings were being affected
by the atmospheric pressure; i.e., even
if the pressure in a piezometer remained
constant, changes in atmospheric pressure
would affect pressure readings on the
manometer.
Another series of pressure readings
were obtained over a subsequent five hour
period on November 26, 1978, and barometric
pressure at the site was also recorded dur-
ing this interval. The results from one of
the six piezometer nests are shown as a
representative indication of the effect of
barometric pressure on manometer readings.
Results from the other five piezometer
nests were similar.
The gage pressures in the piezometers
measured with the manometer are shown in
Figure 4 (a). Barometric pressure readings
during the sampling interval are shown in
Figure 4 (b). Absolute pressures (the sum
of the barometric and gage pressures) are
indicated in Figure 4 (c). It can be seen
that while relatively large fluctuations
in barometric pressure were observed, ab-
solute pressures in the landfill remained
fairly constant over the five hour period.
401
-------
Absolute pressures were found to vary con-
siderably from week to week, indicating
that the landfill does respond to changes
in atmospheric pressure but at a very slow
rate.
Thus relying on gage pressures alone
to give an indication of pressure changes
within a landfill can lead to erroneous
conculsions. For this reason, all subse-
quent pressure measurements were converted
to absolute pressures.
3. 5 Pump ing. Test
A trial pumping test was conducted at
the gas production site on January 12, 1979.
Gas concentrations and pressures were mea-
sured at the piezometers before initiation
of pumping, and pressures were continuous-
ly monitored throughout the pumping phase
of the test and after pumping ceased. The
pump was allowed to run for 90 minutes at
a rate of approximately 1.13 m^/min, and
pressure recovery within the landfill after
cessation of pumping was monitored for 30
minutes.
Contours of methane concentrations in
the monitored area before commencement of
pumping are shown in Figure 5. The lowest
methane concentrations were observed near
the bottom of the refuse, which is located
at an average depth of approximately 13.5m.
During drilling of the monitoring wells, it
was found that refuse at the bottom of the
landfill consisted mainly of nonputres-
cible materials, which would explain the
low methane concentrations. The shape of
the contours near the surface of the land-
fill are uncertain. It has been assumed
in Figure 5 that the contours are approx-
imately orthogonal to the surface because
the frozen soil presents an impermeable
upper boundary. However it is possible
that contours are approximately parallel
to the surface very near the bottom of the
frozen soil layer. Attempts will be made .
in future tests to determine upper contour
configurations.
Gas samples were not collected during
or after pumping for the trial test, but
will be obtained in future tests.
Gas Withdrawal WelL
0.6 m Frozen
L
± 13.5m
Piezometers
Scale
Verlical-1 • 120
Horizonul-1:240
Fijutt S - INITIAL CONTOURS OF METHANE CONCENTRATIONS (X)
(JAN 12, 1979)
402
-------
Drawdowns in absolute pressure at pie-
zometer nest 4 are shown in Figure 6. Mea-
surements were not available for the top
piezometer as it was plugged. As shown in
Figure 6, the largest drawdowns were ob-
tained in the piezometers located at the
same depth as the gas withdrawal well scr-
een, which was approximately 9m from piez-
ometer nest 4. It appears that steady-
state conditions were close to being ach-
ieved when the pump was shut off, however
this will be verified in future tests in-
volving longer pumping times.
It also appeared that pressures
reached an equilibrium throughout the depth
of the piezometer nest after pumping
ceased. This is apparent in Figure 6,
which shows that drawdown pressure 30 min-
utes after cessation of pumping was approx-
imately -0.7 inches of water in each of
the four piezometers.
Pressure contours in the landfill at
the end of the 90 minute pumping period
are shown in Figure 7. Atmospheric press-
ure at this time was approximately 409.9
inches of water, while pressures in the
landfill near the gas withdrawal well
screen were on the order of 408.8 inches
of water. It is quite apparent that the
zone of influence of the pump extended
beyond the range of the monitoring wells.
It is not possible at this time to estim-
ate how far this zone of influence ex-
tends ; monitoring wells 9 to 11 indicated
in Figure 1 will be used to examine its
extent.
Future pumping tests will involve
running the pump at different discharge
rates to attempt to contain the zone of
influence within the range of our monitor-
ing piezometers. Gas concentrations dur-
ing pumping at the positive pressure end
of the pump will also be obtained, as well
as in the piezometers during the recovery
period after pumping ceases. These meas-
urements will be used to obtain estimates
of gas production rates in the landfill,
as explained in the following section.
3.6 Analy_s is_Meth_odjDlogy
Results of the pumping tests descr-
ibed above will be used to estimate meth-
ane gas production rates in the landfill.
Two methods will be used to obtain these
estimates.
The first method will involve measur-
ing gas concentrations exhausting from the
pump after steady-state conditions have
been achieved. The rate of production will
then be estimated knowing the steady-state
gas concentrations and the discharge rate
and zone of influence of the pump. This
technique was used in the four California
studies listed in Table 1.
A second method of estimating methane
production rates will be attempted to pro-
vide an alternative means of estimation
and to allow results from the two techni-
ques to be compared. However unlike the
first method, which has been tried at
several landfills with reasonable success,
the second technique is still in the
theoretical stage, and it is not known
whether or not it will produce satisfactory
results.
While the first method will involve
monitoring gas concentrations and pressures
during pumping with steady-state conditions
in effect, the second method will involve
monitoring concentrations and pressures
during recovery of the landfill. After
pumping ceases, pressure equilibration
will occur in the zone of influence through
the introduction of air from the gas with-
drawal well and perhaps also the surface
of the landfill. This equilibration is
expected to occur fairly rapidly, and the
results of the first pumping test and those
conducted using a similar pumping technique
at another landfill (Gartner Lee Assoc.
Ltd., 1978) have indicated that this is
likely to occur.
Thus it is anticipated that, within a
short time after pumping ceases, pressures
in the landfill will have completely re-
covered while methane concentrations will
be partially depleted within the zone of
influence of the pump. Gas composition in
this zone will be monitored for some time,
and the rate of methane production will be
estimated based on the rate of recovery of
methane concentrations and changes in the
volumetric extent of the recovery zone.
4. GAS MIGRATION FROM LANDFILLS
4.1 Scope^ of_E:g>jjrlmenjt.al Wojrk
The objectives of this phase of the
work are to measure the patterns of gas
movement into soils adjacent to a landfill,
403
-------
NOTES
Gas Flow Rate =
1.13 mVmin
Pump Off e 90 rain
2.4m
3.0
Withdrawal
Well Screen
(9.14m away) 4-9
5.5
7.6m
10.7
I7'3
f 7.9
9.8
10.4
12.2
12.8m
Elapsed Time
after Pumping Start (min)
,0 60 120
Figure 6-ABSOLUTE PRESSURE DRAWDOWNS IN PIEZOMETER
NEST #4 DURING PUMPING TEST (JAN 12, 1979)
Gas Withdrawal Well
0.6 m Frozen
Layer
H3.5 m
NOTES;
Cas Flow Rate - 1.13 m3/mlq
Atmospheric Pressure =
409.9" H20
Piezometers
Scale
Verlical-1-UO
HoriionUl-V240
"I
Figure 7-ABSOLUTE PRESSURE CONTOURS O400"H->0)
AT END OF 90 rain PUMPING PERIOD
(JAN 12, 1979)
404
-------
to examine the. effects of precipitation
and frost cover on these patterns, and to
use these measurements to calibrate the
gas flux model described in Section 5.
4.2 Th e^ N_ature_qf_ Gas_ MigratIon
Gases generated in a landfill as a
result of anaerobic decomposition of organ-
ic materials normally migrate upwards
through the refuse and soil cover, and
diffuse into the atmosphere. However when
upward movement is impaired, the gases
move laterally along subsurface paths of
least resistance until they find a vertic-
al path to the atmosphere.
Two subsurface conditions tend to
promote lateral gas migration: those that
restrict or prevent upward movement, and
those that provide alternative routes for
lateral movement. Vertical passage can be
hindered by the soil cover compacted over
the refuse, particularly when saturated
with water or frozen. Surface structures
such as asphalt pavement, concrete found-
ations and floor slabs can also confine
gases and promote lateral migration. Alt-
ernative routes for gas migration are pro-
vided by manmade structures such as sub-
serf ace utility structures and sewers, and
also by cracks, fissures and voids result-
ing from landfill differential settlement.
Lateral migration of gases can occur
to considerable distances beyond fill
boundaries. In studies conducted on san-
itary landfills in the Los Angeles area,
methane concentrations of 10-20% were de-
tected as far as 180 m from the boundar-
ies of completed landfills at a depth of
0.6 m below the ground surface (County of
Los Angeles, 1972). The extent of gas
migration beyond the landfill boundaries
is a direct function of soil permeability
and of gas pressure and concentration with-
in the landfill. Gases generated in a
landfill surrounded by clay soils can
travel only a short distance from the edges
of the landfill. However in landfills
surrounded by more permeable materials,
such as those constructed in gravel
quarries, the gases can travel a large
distance from the fill boundaries.
Migrating gases consist mainly of
carbon dioxide and methane. Methane in
volumetric concentrations of 5-15% forms
an explosive mixture with air. Duffusion
of this mixture into enclosed buildings
can create severe explosion and fire haz-
ards.
Attempts to solve the problem of
methane migration are usually by either
the installation of impermeable barriers
or ventilation systems around the perim-
eter of the landfill. Venting may be
either natural or forced.
4.3 Instjrumeiita.tjL on_ jind_ Moili_tor_ing_o_f Site
Changes in gas composition and press-
ure in the migration study area are being
monitored by a number of piezometers, with
the main line of monitoring wells position-
ed orthoganally to the edge of the refuse
and extending approximately 50 m into the
soil adjacent to the landfill. Two add-
itional sets of wells are positioned on
either side of the main line to examine
spatial variations in pressures and gas
concentrations along the perimeter of the
refuse. A plan view of the gas migration
study area is shown in Figure 8.
Piezometer installation and sample
collection were conducted using the tech-
niques described above for the gas pro-
duction study.
4. 4 Mjtgrati_oii j[tudi_es_ _Conduct_ed_ _tp_Da_te^
Absolute pressures in the piezometers
at the migration site were measured once
a week for five weeks, commencing January
10, 1979. Gas compositions in the piez-
ometers were also measured on three of
these days. The results of January 17,
1979 are presented as an example of the
data that were obtained.
Contours of average absolute press-
ures in inches of water and average per-
cent methane concentrations for January 17
are shown in Figure 9. These contours rep-
resent average absolute pressures and con-
centrations throughout the depth of the
migration zone, which extends to the
groundwater table at a depth of approxim-
ately 8 m.
A forced venting system consisting of
vertical perforated pipes extending to the
groundwater table and connected to a horiz-
ontal header leading to a pump, is in op-
eration at the migration study site. The
influence of this system is shown by the
405
-------
O
CT1
REFUSE
'•'-' - ' ) Venting
0%~~.-^~..:^
System
4.2
Average Absolute
Pressures
(+4CO"H20)
Average X Methane
Concentrations
Scale-1 240
-*~1
S3
8'0 Header
• Piezometer Nest
A Vertical Interceptor Well
(approximate location)
O Above-ground Vent
• H
Sca!e-1:240
Figure 9-PLAN VIEW SHOWING CONTOURS OF PRESSURE AND
CONCENTRATION AT CAS MIGRATION SITE
(JAN 17,1979)
Figure 8-PUN VIEW OF GAS MIGRATION SITE
-------
magnitudes of the pressure contours in Fig-
ure 9. The effectiveness of the system is
apparent from the methane concentration
contours, which indicate that methane is
not migrating beyond the venting system.
Variations in pressures and concentra-
tions with depth on January 17 through the
main line of monitoring wells, indicated as
Section 'A-A' on Figure 8, are shown in
Figure 10. The influence and effective-
ness of the forced venting system is again
apparent from these elevation views.
Pressures appear to be fairly constant with
depth in the vicinity of the venting sys-
tem, indicating that gas is being withdrawn
throughout the total length of the vertical
perforated pipes. The large decrease in
methane concentrations, from 50% in the
refuse to 0% at the venting system, is also
apparent in Figure 10. As with the prod-
uction study, the shape of the pressure
and concentration contours near the surface
are uncertain at this time.
4.5 Aiialy_sis_of. MigratjLpn_ Resiults_
Results from the other four sampling
days were similar in some aspects to those
reported for January 17. The results were
similar in that approximately the same
patterns of pressure and concentration con-
tours were in effect on each of the study
days. However, the magnitude of these con-
tours displayed considerable variation from
week to week, the most marked being those
for absolute pressures. Changes in con-
centration contour magnitudes were caused
by variations in methane concentrations in
the refuse. No methane was found in the
area beyond the venting system on any of
the study days.
A number of additional migration stud-
ies will be conducted over the next several
months. Of particular interest will be
changes in migration patterns as thawing of
the upper soil occurs.
The data from all migration studies
will be used to examine seasonal trends in
pressure and methane concentration patterns,
and to calibrate the gas migration model
described in the following section.
5. HODELLING 'METHANE MIGRATION
5 . 1 Moded Des_c_ri2tion. ^md^ Cal±brat±on
Data collected from the migration
study site will be used to calibrate a
previously developed model for gas trans-
port in porous media (Mohsen £t_ al. , 1978).
In the model, the diffusion-convection equ-
ations coupled with a mass conservation
equation for a binary mixture of gases are
Scale:
Verfical-V60; Horizonta 1-1:300
0.6 m Frozen
Layer -.i™,*™*-—__
Piezometers^
Absolute
Pressure
Contours
HOO" H20)
4.7 .-5
Figure 10-ELEVATION VIEW (SECTION'A-At) SHOWING DEPTH
VARIATION IN PRESSURE AND CONCENTRATION
AT GAS MIGRATION SITE (JAN 17, 1979)
407
-------
solved using finite elements under a com-
bination of Dirichlet, Neumann and Cauchy
type boundary conditions. The finite el-
ement solution is a two step process. The
first step solves for the pressure field,
and mass and volume averaged velocities are
computed from this field. The second step
solves for gas concentrations at various
points within the media. Density and vis-
cosity changes are accounted for.
Field situations can be simulated
using either an axisymmetric configuration
with cylindrical coordinates, or a two-
dimensional Cartesian system. The axis-
ymmetric format consists of radial and nor-
mal (generally vertical) flux from the
source. This is a realistic condition at
many landfills. Although conditions must
be uniform at a given radius, any number
of horizontal soil strata is allowed. The
axisymmetric format will accommodate var-
ious media and boundary configurations,
both of which may be time-variant. For
solutions close to the source, the model
behaves like a two-dimensional orthogonal
system.
In applying the model to the gas mi-
gration site, the main line of piezometer
nests indicated as Section 'A-A' in Fig-
ure 8 will be discretized into a finite
element configuration. Data requirements
for application of the model to this loca-
tion will include porosity, intrinsic per-
meability and moisture content for soils
in the study section, and a deliniation of
all relevant boundary conditions. In
addition, relationships for viscosity and
density as a function of gas concentrat-
ion will be required and will be selected
from the literature.
In calibrating the model, values of
the relevant input parameters will be var-
ied within their measured limits to give a
best fit to field measured gas concentra-
tions and pressures. The sensitivity of
these parameters will also be examined.
5.2 Calibra.ted_Model_Ajjp li_cat_ions_
The calibrated model will be used to
display variations in gas migration patt-
erns and to evaluate various gas control
methods.
The variety of gas migration patterns
to be studied will include the following
soil conditions:
a) unconfined from above, homogeneous,
long term as normal;
b) statified soil including highly per-
meable layers as preferred migration
routes ;
c) confined from above to simulate winter
conditions; and
d) time varying influent boundary con-
ditions .
Methods for gas control at landfills
will also be evaluated in terms of their
effectiveness in reducing gas concentra-
tions. The methods examined will include:
a) atmospheric vents as a function of
penetration depth,
b) barriers, and
c) positive pressure systems for gas
collection.
5 . 3 Exam£le_ o_f _PZ.evi.2.uJL
Model
Model simulations have been performed
on data collected from a previous invest-
igation at the same landfill used for this
study. The site configuration is shown in
plan view in Figure 11. The figure also
shows the existance of a venting trench
along the northwest side of the landfill,
as well as the overall dimensions of the
trench and landfill. The forced venting
systems indicated on the diagram were not
in effect at the time this previous study
was conducted.
A previous field study was conducted
to evaluate the effectiveness of the trench
in preventing the migration of methane gas.
Figure 12 shows the pattern of multi-level
gas sampling piezometers used in this pre-
vious investigation, and their positions
relative to the trench. Samples were coll-
ected to determine gas compositions at the
various piezometer locations , and these
were used subsequently for comparison with
the model simulation.
Cross-section 'B-B1 , as indicated in
Figure 11 is shown in detail in Figure 13.
This represents the radial configuration
used for model simulation. Although data
such as pressure contours, source proper-
ties and media characteristics were sparse,
attempts were made to generate suitable
values for the simulation process.
408
-------
Pump House
-Gas Intercept- £
or System
(Wells and
Uterals) .
Previous Migration
Study Site
Figure 11-LOCATION OF STUDY AREAS
REFUSE
(approx. 15m away)
Moisture Seal
^ i»-
'—12"«> Perforated Corrugated Pipe
^
Coarse Gravel Trench
(Not to Scale)
O Gas Sampling Piezometer Nest
(4/well)
Figure 12- LAYOUT OF SAMaiNG, VENTING AND TRENCHING
SYSTEM FOR PREVIOUS MIOAT10N STUDY
409
-------
Axis of
|Symrnetfy R-152.4H,
— '^. 1U.D/ I"
H
Lnndfill Source ^-—
15-24 rnL
f
Vent
''^%: &*&%$.
^^ Clay
Water Table Boundary
Figure 13 - CROSS-SECTION'8-B'
520
9.14m
Soil
LI
Trench
I 5.18 ra
Oct Nov Dec Jan Feb March April May
(A, B, C, D denote X at different angular displacements)
—— Measurements at X Finite Element Model Solutioni
4.57m
Oct Nov Dec Jan Feb March April May June
Figure 14- COMPARISON OF GAS FLUX MODa RESULTS WITH
MEASUREMENTS
410
-------
The results of the simulation as com-
pared to the field measurements are shown
in Figure 14, for methane concentrations
at two points in the medium beyond the
trench. Although the comparision is only
fair, it must be noted that concentrations
at sampling points A to D, which are at the
same radial distance from the source as
the simulated point, displayed substant-
ial variability. The field data show that
the trench as installed is ineffective in
preventing the transport of methane gas.
The model simulation presents the same con-
culsion. Consequently, use of the model
in design considerations would appear
justified.
6. SUMMARY
A research program is currently under-
way to study pressures and gas composit-
ions both in a landfill and at its periph-
ery, and to use the results to calibrate a
gas flux model.
Estimates of gas generation rates
will be obtained by monitoring gas comp-
ositions and pressures before,during and
after application of a zone of negative
pressure within the landfill. This zone
is provided by means of a gas withdrawal
well installed vertically in the landfill
and vented to a pump. A trial pumping
test has indicated that sufficient draw-
down is achieved throughout the monitored
area to permit satisfactory measurements
to be obtained, and has provided support
for implementation of a theoretical tech-
nique for evaluating production rates us-
ing data collected during the recovery
period after pumping ceases.
Several sets of pressure and concen-
tration measurements have been obtained at
the migration site. The influence and
effectiveness of a forced venting system
in operation at this site were apparent
from these measurements. No methane was
found in the area beyond the venting sys-
tyem on any of the study days. The data
from all migration studies will be used to
examine seasonal trends in pressure and
methane concentration patterns, and to
calibrate a gas transport model.
An example of the ability of the gas
transport model to simulate field condit-
ions was given. The model will be used in
this study to display variations in gas
migration patterns under a variety of
soil conditions, and to evaluate various
gas control methods.
The influence of atmospheric press-
ure on gage pressure readings was demon-
strated. It is suggested that barometric
pressures in the field be obtained at the
same time as gage pressures, and that all
pressures by converted to absolute press-
ures for purposes of comparison.
REFERENCES
1. Blanchet, M. J., "Recovery of Methane
Due from North California Landfill",
Oil and Gas Journal, Vol. 74, No. 46,
Nov. 15, 1976.
2. City of Los Angeles, Bureau of Sani-
tation, "Estimation of the Quantity
and Quality of Landfill gas from the
Sheldon-Arleta Sanitary Landfill",
Internal Report, 1975.
3. County of Los Angeles, Department of
County Engineer, and Engineering-
Science Inc., Development of Construc-
tion and Use Criteria for Sanitary
Landfills, Final Report, Prepared
for the Department of Health, Educa-
tion and Welfare Public Health Service,
Solid Wastes Program, 1972.
4. Coe, J. J., "Effect of Solid Waste
Disposal on Ground Water Quality",
Journal of the American Water Works
Association, Dec., 1970
5. DeWalle, F. B., E. S. K. Chian and E.
Hammerberg, "Gas Production from Solid
Waste in Landfills", Journal of the
Environmental Engineering Division,
ASCE, Vol. 104, No. EE3, June, 1978.
6. Environmental Protection Agency, "Re-
covery of Landfill Gas at Mountain
View", Report No. SW-587d, May, 1977.
7. Farquhar, G. J. and F. A. Rovers, "Gas
Production During Refuse Decomposit-
ion", Water, Air and Soil Pollution,
Vol. 2, 1973.
8. Gartner Lee Associates Limited, "Hop-
kins Street Gas Migration Study, Gas
Pumping Test Results", Project No. 78-
21, Nov., 1978.
411
-------
9. Mandeville, R. T.,"Fuel Gas from
Landfill", Clean Fuels from Biomass,
Sewage, Urban Refuse, Agricultural
Wastes, Symposium Papers, Institute
of Gas Technology, Orlando, Florida,
Jan. 27-30, 1976.
10. Mohsen, M. F. N. , G. J. Farquhar and
N. Kouwen, "Modelling Methane Migra-
tion in Soil", Applied Mathematical
Modelling, Vol. 2, Dec., 1978.
11. Schuyler, R. E., "Energy Recovery at
the Landfill", presented at llth
Annual Seminar, Governmental Refuse
Collection and Disposal Association,
Santa Cruz, California, Nov., 1973.
412
-------
List of Attendees
Abeles, Tom
llth Ave., South
Minneapolis, MN 55407
Arlotta, Salvatore
Wehran Engineering
666 E. Main St.
Middletown, NY 10940
Absher, Susan M.
Environmental Protection Agency
4601 N. Park Ave., #1818
Chevy Chase, MD 20015
Barineau, James M.
Leon Cty. Public Works
Rt. 2, Box 656
Tallahassee, FL 32301
Albrecht, Oscar
SHWRD - MERL
26 W. St. Clair St.
Cincinnati, OH 45268
Basinger, Spencer K.
Oconee Area Plan. & Dev. Conun.
P.O. Box 707
Milledgeville, GA 31061
Alter, Harvey
Natl.Ctr.for Resource Recovery
1211 Connecticut Ave., NW
Washington, DC 20036
Beck, Richard B.
Burns & McDonnell Engr.
7821 E. 80th St.
Kansas City, MO 64106
Co.
Ammons, James T.
U.S. Army Corp of Engineers
110 Robin Lane
Huntsville, AL 35802
Beck, William W.
A.W. Martin Assoc.,Inc.
900 W. Valley Forge Rd.
King-Prussia, PA 19406
Anderson, Bernard F.
E.I. DuPont Co.
1610 E. Lafayette Dr.
West Chester, PA 19380
Bernheisel, J. F.
Natl. Ctr. for Resource Recovery
1211 Connecticut Ave., N.W.
Washington, DC 20036
Anderson, Robert C.
Environmental Law Inst.
1346 Connecticut Ave., N.W.
Washington, DC 20036
Blackham, William H.
11738 N.W. 26th St.
Coral Springs, FL 33065
Anderson, Robert J.
Mathtech
Box 2392
Princeton, NJ 08540
Bnjafield, D. W.
Redland Purle Lmt.
Claydons Lane
Essex, England
Anderson, Sonia
22 Fairway Dr.
Cranbury, NJ 08512
Bolton, Roger E.
Williams College
Dept. of Economics
Williamstown, MA 01267
413
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Boretsky, Metodij
U.S. Navy
8302 MacArthur Rd.
Wyndmoor, PA 19118
Chatterjee, Anil K.
SRI International
333 Ravonswood Ave.
Menlo Park, CA 94025
Bromley, John
Waste Research Unit
132 No. Ave.
Abingdon, OXON
Checca, Thomas J.
Post,Buckley,Schuh & Jernigan
13420 SW 77th Ave.
Miami, FL 33156
Brunner, Dirk R.
Environmental Protection Agency
5491 Wasigo Dr.
Cincinnati, OH 45230
Chian, Edward S.K.
Georgia Tech
Daniel Lab.
Atlanta, GA 30332
Brunner, Donald E.
U.S. Navy Civil Engr. Lab.
7266 Briarcliff Cir.
Ventura, CA 93003
Clark, Dave
New Castle Cty.Public Works
2701 Capital Trail
Newark, DE 19711
Buivid, Michael G.
Dynatech Corp.
34 Bowker St.
Brookline, MA 02146
Clark, Thomas P.
Minn. Pollution Control Agency
3572 Golfview Dr.
St. Paul, MN 55110
Bush, Harvey H.
Greenleaf/Telesca
1451 Brickell Ave.
Miami, FL 33134
Cleveland, Elmer G.
Environmental Protection Agency
345 Courtland St., NE
Atlanta, GA 30308
Carpenter, Charles D.
City of Orlando
1046 W. Gore
Orlando, FL 32805
Cohen, Alan S.
Argonne National Lab.
1543 N. Chickasaw Dr.
Naperville, IL 60540
Carroll, William D.
City of Winnipeg
280 William Ave.
Winnipeg, Manitoba Canada
Cooley, Kevin J.
Post,Buckley,Schuh & Jernigan
3191 Maguire Blvd.
Orlando, FL 32803
Charbonnier, James W.
American Resource Recovery
P.O. Box 698
Jupiter, FL 33458
Cowhey, James J.
Land & Lakes Co.
123 N. Northwest Highway
Park Ridge, IL 60068
414
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Cresap, C. C.
Dougharty Cty. Public Works
P.O. Box 1827
Albany, GA 31702
Del Fino, Ronald T.
R.I. Solid Waste Mgmt.
39 Pike St.
Providence, RI 02903
Croke, Kevin
2639 Praire
Evanston, IL 60202
DeLuca, Frank
Rt. 3, Box 1954
Odessa, FL 33556
Cunningham, Richard D.
The BF Goodrich Co.
500 So. Main St.
Akron, OH 44318
DeWalle, Foppe
Univ. of Washington
Dept. of Environ. Health
Seattle, Washington 98195
Curtis, Curtis D.
City of Orlando
1046 W. Gore
Orlando, FL 32805
Dietz, Jess C.
Clark,Dietz Engrs.,Inc.
P.O. Drawer 1976
Sanford, FL 32771
Dahl, Thomas E.
Martel Labs., Inc.
851 Snell Isle Blvd., NE
St.Petersburg, FL 33704
Doggett, Ralph
Intl. Research & Tech.
7655 Old Springhouse Rd.
McClean, VA 22101
Daly, Ernest
University of Miami
Dept. Mech. Engr.
Coral Gables, FL 33124
Domalski, Eugene
307 Summit Hall Rd.
Gaithersburg, MD 20760
Davis, Jack E.
Tuscaloosa Testing Lab.Inc.
P.O. Box 1094
Tuscaloosa, AL 35401
Donnelly, Jean A.
Univ. of Cincinnati
2323 Kenlee Dr.
Cincinnati, OH 45230
Davis, Robert
189 Sheridan Ave.
Longwood, FL 32750
Dower, Roger
Environmental Law Inst.
1346 Connecticut Ave.,N.W.
Washington, DC 20036
Deamud, John W.
Reynolds, Smith, Hills
7120 Lake Ellenor Dr.
Orlando, FL 32809
Duggan, James C.
Tennessee Valley Authority
440 Commerce Union Bank Bldg.
Chattanooga, TN 37401
415
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Eacott, Robert B.
Govt. of Western Australia
27 Eaton Villa Place
San Carlos, CA 94070
Fitzgerald, Sidney S.
SCA Services
901 Silver Hill Rd.
N.Little Rock, AR 72118
Eden, Burton H.
Combustion Equip. Assoc., Inc.
61 Taylor Reed Place
Stamford, CT 06906
Flatt, George
2008 Gibbs Dr.
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Elstrom, Alden
271% Pondella Rd.
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Flower, Franklin B.
Cook College-Rutgers Univ.
P.O. Box 231
New Brunswick, NJ 08903
Emrich, Grover H.
A.W. Martin Assoc.,Inc.
900 W. Valley Forge Rd.
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Flynn, Daniel V.
111. Environ. Protection Agency
603 Eastman Ave.
Springfield, IL 62702
Farrell, Robert S.
ME Dept. of Environ.
Div. of Solid Waste
Augusta, ME 04330
Protection
Fowler, Bert
Waste Mgmt. of 111.
P.O. Box 563
Palos Hgts., IL 60463
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P.O. Box 2842
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Gilbert/Commonwealth
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Franklin, William E.
Franklin Assoc., Ltd.
8340 Mission Rd., Suite 101
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Maplewood Rd.
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Freeman, Harry
IERL - EPA
Cincinnati. OH 45268
Fisher, Gerald E.
E.I. DuPont
3707 Chevy Chase
Louisvelle, KY 40218
Friedman, D.
Environmental Protection Agency
401 M Street S.W.
Washington, DC 20460
416
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Fuller, Wallace H.
Univ. of Arizona
Soils, Water & Engr.
Tucson, AZ 85721
Gordon, Judith G.
The Mitre Corp.
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Occidental Research Corp.
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111. St. Geological Survey
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Texaco Inc.
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City of Tampa
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Raytheon Service Co.
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Geswein, Allen
401 M. Street, SW
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Haigh, C. C.
Beaufort Cty. Public Works
P.O. Box 4279
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Todd Giddings & Assoc.
140 W. Fiarmount Ave.
State College, PA 16801
Halvorson, Thomas G.
Union Carbide Corp.
5535 Mapleton Rd.
Lockport, NY 14094
Goodson, Robert H.
Seaburn & Robertson, Inc.
5510 Gray St., Suite 118
Tampa, FL 33609
Ham, Robert
2130 Chadbourne Ave.
Madison, WI 53705
Gorczynski, Jan
Stevens Elastomeric Prod.
25 Payson Ave.
Easthampton, MA 01027
Hanna, Edward E.
City of Orlando
1046 W. Gore
Orlando, FL 32805
417
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Hansen, Warren G.
SCS Engineers
2875 152nd Ave., NE
Redmond, WA 98052
Hentrick, Robert
Systems Tech. Corp.
245 No. Valley Rd.
Xenia, OH 45385
Harp, James D.
Senergy, Inc.
2961 Fitzooth Dr.
Winter Park, FL 32792
Heyden, Peter
Cahn Engineering
Alex Dr.
Wallingford, CT 06904
Hartz, Ken
702 G Eagle Hts.
Madison, WI 53705
Hickey, Peter
New Executive Office Bldg.
Room 3011
Washington, DC 20024
Hasselriis, Floyd
Combustion Equip.
555 Madison Ave.
New York, NY 10022
Hill, David T.
Auburn University
1817 SW 78th Terrace
Gainesville, FL 32601
Haxo, Henry E.
Matrecon Inc.
Box 24075
Oakland, CA 94623
Hoye, Robert
Pedco Environmental, Inc.
11499 Chester Rd.
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Hecht, Norman L.
Univ. of Dayton Research Inst.
300 College Park Dr.
Dayton, OH 45469
Hudson, James F.
Urban Systems Research
36 Boylston St.
Cambridge, MA 02138
Heckler, Dave
Thomas,Dean & Hoskins,Inc.
3808 8th Ave., So.
Great Falls, MT 59405
Hunt, Robert G.
Franklin Assoc., Ltd.
8340 Mission Rd.
Prairie Vill., KS 66206
Helmstetter, Arthur J.
Systems Tech. Corp.
245 North Valley Rd.
Xenia, OH 45385
Hunt, Tim E.
P.B.Co.Solid Waste Authority
120 So. Olive Ave.
West Palm'fich, FL 33401
Hendrix, Sylvan
Koppers-Sprout Waldron Div.
P.O. Box 6221
Lakeland, FL 33803
Husain, Mohammad A.
FL Dept. of Environ. Reg.
1409 Chowkeebin Lane
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418
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Iglehart, Cecil
SCA Services, Inc.
8806 Nottingham Pkwy.
Louisville, KY 40222
Landreth, Robert E.
Environmental Protection Agency
26 West St. Clair
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James, Steve
SHWRD - MERL
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Lavigne, Ronald L.
Resource Control Inc.
Quabbin Office Bldg.,Valley Rd.
Barre, MA 01115
Jones, Larry W.
U.S. Army Corp of Engineers
Univ. of Tenn.
Knoxville, TN 37916
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Lycoming Co.
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Kinman, Riely N.
Univ. of Cincinnati
415 Stevenson Rd.
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Lazarus, Arthur G.
C-E Maguire, Inc.
31 Canal St.
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Chem/B348
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City of Sanford
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SHWRD - MERL
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Leamon, Michael R.
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2150 Storm Canyon Rd.
Winston-Salem, NC 27106
Klein, Michael S.
Mgmt. of Res. & Environ.
41C New London Turnpike
Glastonbury, CT 06033
LeCroy, Charles E.
Bay Cty. Solid Waste Dept.
206 South 22 A
Panama City, FL 32401
Knight, James A.
Georgia Inst. of Tech.
2117 Kodiak Dr. NE
Atlanta, GA 30345
Lewis, David
York Research Corp.
1 Research Dr.
Stanford, CT 06906
Laden, Kenneth G.
Dept. of Envir. Services
1321 So.Carolina Ave.,SE #4
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Lincoln, Edward
University of Florida
AG. Engr. Dept.
Gainesville, FL 32611
419
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Liskowitz, John W.
NJ Inst. of Tech.
Bunker Dr., RD #2
Belle Mead, NJ 08502
Mavinic, Donald S.
Univ. of British Columbia
1001 Canyon Blvd.
N.Vancouver, B.C..Canada V7R2K2
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Mayes, Sudderth & Etheredge
5750 Major Blvd.
Orlando, FL 32805
Mayo, Franics T.
Environmental Protection Agency
26 West St. Clair St.
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Love, John
Univ. of Mo.-Columbia
Engr. Bldg. 2024
Columbia, MO 65201
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Post,Buckley,Schuh,& Jernigan
7500 N.W. 52nd St.
Maimi, FL 33166
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Jamestown Star Rt.
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Boulder, CO 80302
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Monsanto Company
800 N. Linberg Blvd.
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City of Lake Worth
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15257 E. Colonial Dr.
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U.S. Army Corp of Engineers
P.O. Box 631
Vicksburg, MS 39180
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41C New London Turnpike
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California Pellet Mill Co.
1450 Kleppe Ln.
Sparks, NV 89431
McManatny, John
250 Carib Dr.
Merritt Isle., FL 32952
Malone, Philip G.
U.S. Army Corp of Engineers
P.O. Box 631
Vicksburg, MS 39180
Mellott, Philip K.
Nishna Sanitary Serv.,Inc.
P.O. Box 182
Elliott, IA 51532
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Tim Mather, Inc.
2701 Casey Key Rd.
Nokomis, FL 33555
Meyer, G. L.
USEPA
Ofc. Radiation Progs.
Washington, DC 20467
420
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Miller, Carlton K.
Broward County
Room 526, 236 S.E. 1st Ave.
Ft.Lauderdale, FL 33301
Mutch, Robert D.
Wehran Engineering
666 E. Main St.
Middletown, NY 10940
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SCS Engineers
11800 Sunrise Valley Dr.
Reston, VA 22091
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Waterways Experiment Station
P.O. Box 631
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Franklin Assoc.,Ltd.
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5750 Mahor Blvd., Suite 200
Orlando, Fl 32805
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Versar, Inc.
3257 Victor Cir.
Annadale, VA 22003
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John G. Reutter Associates
9th & Cooper Streets
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Environ. Impact Control Dir.
Fisheries & Environ. Canada
Ottawa, Ontario, Canada
Nichols, Walter P.
State Of Alabama - Public Health
State Office Building
Montgomery, AL 36130
Moore, Byron G.
City Of Orlando - Public Service
400 W. Livingston St.
Orlando, FL 32802
Noble, David
4827 W. Bradock
Alexandria, VA 22311
Moreau, Raymond L.
FL Res. Recovery Council
2600 Blair Stone Rd.
Tallahassee, FL 32301
Nollet, Anthony R.
AENCO Inc.
Box 387
New Castle, DE 19720
Morgan, William L.
Board of Health
308 N. 16th St.
New Castle, IN 47362
Oberacker, Don
SHWRD - MERL
26 W. St. Clair St.
Cincinnati, OH 45268
Murray, David E.
Reitz & Jens, Inc.
Ill S. Meramec
St. Louis, MO 63105
Oppelt, Edwin T.
Environmental Protection Agency
7939 Shelldale Way
Cincinnati, OH 45242
421
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Pace, Robert
1291 Plymouth Place
Jacksonville, FL 32205
Rebholz, Richard P.
City of Fort Walton Beach
Rt.1, Box 91
Mary Esther, FL 32569
Patel, Vijay
Pedco Environmental, Inc.
11499 Chester Rd.
Cincinnati, OH 45246
Reese, John A.
FL Dept. of Environ. Reg.
2600 Blairstone Rd.
Tallahassee, FL 32301
Peritz, Leigh A.
Raytheon Service Co.
63 Washington St.
Winchester, MA 01890
Reilly, Bertram
9 Choctaw Trail
Ormond Beach, FL 32074
Peterson, Arnold
Stevens Elastomeric
26 Payson Ave.
Easthampton, MA 01027
Reynolds, Stan L.
Syst.,Science & Software
Box 1620
La Jolla, CA 92038
Pohland, Fred
Georgia Tech - Civil Engineering
4631 North Springs Ct. NE
Atlanta, GA 30338
Rinaldo, Marjory L.
Residuals Mgmt. Tech.
1406 E. Washington Ave.
Madison, WI 53703
Polk, Malcolm
Atlanta University
Dept. of Chemistry
Atlanta, GA 30314
Ritchie, Charles W.
Dept. for Natural Resources
209 Pin Oak Place
Frankfort, KY 40601
Power, Richard M.
SCA Services, Inc.
19 Daley Ave.
Methuen, MA 01844
Robbins, John A.
Sverdrup & Parcel & Assoc.
174 Royal Palm St.
Sebastian, FL 32958
Pullan, Henry
Redland Purle Lmt.
Claydons Lane
Essex, England
Roberson, David L.
State Public,Health
State Office Bldg.
Montgomery,'AL 36130
Purdy, Kenneth R.
Tech Consultants, Inc.
1485 Leafmore Ridge
Decatur, GA 30033
Rogers, Charles J.
Environmental Protection Agency
461 Merry Maid Lane
Cincinnati, OH 45240
422
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Roulier, Mike
SHWRD - MERL
26 W. St. Clair St.
Cincinnati, OH 45268
Searcy, Phillip E.
Post,Buckley,Schuh & Jernigan
3191 Maguire Blvd.
Orlando, FL 32803
Rugg, Barry
New York Univ.
Barney Bldg.
New York, NY 10003
Seelinger, Richard W.
VOP, Inc.
40 VOP Plaza
Des Plaines, IL 60016
Banning, Don
SHWRD - MERL
26 W. St. Clair St.
Cincinnati, OH 45268
Sengupta, Subrata
University of Miami
Dept. Mech. Engr.
Coral Gables, FL 33124
Sarver, Glen E.
B.F. Goodrich Co.
Rt. 3, Box 11
Marietta, OH 45750
Shanks, Howard R.
Ames Laboratory
A207 Phys. Bldg.
Ames, IA 50011
Scaramelli, Alfred B.
Mitre Corp.
4 Carley Rd.
Lexington, MA 02173
Silva, Thomas F.
General Electric
782 Downing St.
Schenectady, NY 12309
Scarpino, P. V.
Univ. of Cincinnati
Dept. of Civil & Env.
Cincinnati, OH 45221
Engr.
Simister, Bruce W.
Midwest Research Inst.
4135 N.E. Davidson Rd. #374
Kansas City, MO 64116
Schmoeger, Gary A.
Martel Labs.,Inc.
6231 Cedar St.,NE
St.Petersburg, FL 33702
Simpson, William P.
Post,Buckley,Schuh & Jernigan
3191 Maguire Blvd.
Orlando, FL 32803
Schnelle, James F.
C-E Maguire, Inc.
31 Canal St.
Providence, RI 02903
Skinner, John
US EPA (AW 5-64)
401 M St., SW
Washington, DC 20460
Schomaker, Norbert B.
Environmental Protection Agency
65 Bayham Dr.
Cincinnati, OH 45218
Smith, Douglas F.
Dept. Environ. Reg.
825 NW 23rd. Ave., Suite
Gainesville, FL 32601
423
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Smith, Frank M.
Leon County
Rt. 2, Box 656
Tallahassee, FL 32301
Surowiec, Joseph T.
State of Georgia
3454 Alison Dr.
Doraville, GA 30340
Smith, Mark E.
Residuals Mgmt. Tech.
4201 Winnequah Rd.
Monona, WI 53716
Sussman, David
907 6th St.,SW,605-C
Washington, DC 20024
Srinivasan, V. R.
Louisiana State University
Baton Rouge, LO 70803
Swartzbaugh, Joseph T.
Systems Tech. Corp.
245 No. Valley Rd.
Xenia, OH 45385
Steeves, W. M.
Reynolds,Smith & Hills
P.O. Box 4850
Jacksonville, FL 32201
Taylor, James
University of Central Fla.
P.O. Box 25000
Orlando, FL 32816
Stenburg, Robert L.
Environmental Protection Agency
26 W. St. Clair St.
Cincinnati, OH 45268
Teer, Ellis H.
Glace & Radcliffe, Inc.
1347 Palmetto Ave.
Winter Park, FL 32789
Stenstrom, Michael K.
Univ. of California, L.A.
7619 Boelter Hall, UCLA
Los Angeles, CA 90024
Terrill, David
Lycoming Co.
48 W. Third St.
Williamsburg, PA 17701
Steven, Theodore
Alex Dr.
Wallingford, CT 06904
Thomas, Robert A.
Southwest Ga. APDC
P.O. Box 346
Camilla, GA 31730
Stoffel, Clarence M.
Owen Ayres & Assoc.
Rt. 3, Box 16B
Bloomer, WI 54724
Trezek, George
CA Recovery Systems, Inc.
160 Broadway, Suite 200
Richmond, CA 94804
Stoll, Bernard J.
USEPA, OSW
401 M St., SW
Washington, DC 20460
Underwood, George T.
Underwood & Assoc.
Ft. Myers, FL 33904
424
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Vandervort, John D.
Schlegel Area Sealing Syst.
54 Aldwick Rise
Fairport, NY 14450
Weinberger, Carl S.
Teledyne National
1910 Pot Spring Rd.
Timonium, MD 21093
Vesilind, P. A.
Duke University
Dept. of Civil Engr.
Durham, NC 27706
Weinstein, Jack S.
Mayes.Sudderth & Etheredge
5750 Major Blvd.,Suite 200
Orlando, FL 32805
Wagner, Paul L.
Mayes,Sudderth & Etheredge
3370 Vandiver Dr.
Marietta, GA 30066
Welch, Jerome
Kansas Geol. Survey
2606 Bonanza St.
Lawrence, KS 66044
Walsh, James J.
SCS Engineers
5242 Camelot Dr.
Fairfield, OH 45014
Wheeler, William B.
NE Georgia Planning Comm.
115 Lavender Rd.
Athens, GA 30606
Walter, Donald K.
Dept. of Energy
20 MS 2221C
Washington, DC 20545
White, Robert
425 Volker Blvd.
Kansas City, MO 64110
Wanielista, Martin P.
University of Central Fla.
P.O. Box 25000
Orlando, FL 32816
Wigh, Richard J.
Regional Services Corp.
3320 Woodcrest Ct.
Columbus, IN 47201
Ward, George D.
George D. Ward & Assoc.
821 NW Flanders
Portland, OR 97209
Wiles, Carlton C.
Environmental Protection Agency
5853 Brasher Ave.
Cincinnati, OH 45242
Watson, Jack E.
Seaman Corp.
401 Freeman Hill
Tryon, NC 28782
Wilkey, Michael L.
Argonne Natl. Lab.
9700 S. Cass Ave.
Argonne, IL 60439
Weaver, Larry D.
Warner Robins Air Log.Ctr.
113 Glenn Dr.
Warner Robins, GA 31093
Willey, Cliff R.
MD Environ. Service
60 West St.
Annapolis, MD 21403
425
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Wilson, Frank L.
Polk Cty. Environ. Services
P.O. Box 39
Bartow, FL 33830
Zimmerman, R. E.
Escor, Inc.
820 Davis St.
Evanston, IL 60201
Wilson, Ronald H.
Stottler Stagg & Assoc.
P.O. Box 272
Winter Haven, FL 33880
Zumwalt, John B.
Post,Buckley,Schuh & Jernigan
2131 Hollywood Blvd.
Hollywood, FL 33020
Woelfel, Gregory C.
Waste Management, Inc.
900 Jorie Blvd.
Oak Brook, IL 60521
Zwolak, Richard A.
Hillsborough Cty.
700 Twiggs St., Suite 800
Tampa, FL 33612
Wong, Kau-Fui
University of Miami
Dept. Mech. Engr.
Coral Gables, FL 33124
Wood, G. M.
Ontario-Environment
135 St. Clair Ave., W.
Toronto, Ontario Canada
Worrell, William A.
Brown & Caldwell
53 Perimeter Ctr. East
Atlanta, GA 30346
Young, Richard M.
Kansas Geological Survey
2503 Winterbrook Dr.
Lawrence, KS 66044
Yousef, Yousef A.
University of Central Fla.
P.O. Box 25000
Orlando, FL 32816
Kenzel, Kenneth M.
Senergy, Inc.
433 Oak Haven Dr.
Altamonte Spr, FL 32701
426
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TECHNICAL REPORT DATA
/Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/9-79-023a
3. RECIPIENT'S ACCESSI ON-NO.
4. TITLE AND SUBTITLE
MUNICIPAL SOLID WASTE: LAND DISPOSAL
Proceedings of the Fifth Annual Research Symposium
5. REPORT DATE
August 1979 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
Martin P. Wanielista and James S. Taylor, Editors
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of Central Florida
P.O. Box 25000
Orlando, Florida 32816
10. PROGRAM ELEMENT NO.
1DC818
11. CONTRACT/GRANT NO.
806198
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Symposium March 26-28, 1979
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
See also Municipal Solid Waste: Resource Recovery, EPA-600/9-79-023b
Project Officer: Robert E. Landreth (513) 684-7748
16. ABSTRACT
The fifth SHWRD research symposium on land disposal and resource recovery of municipal
solid waste was held at Orlando, Florida on March 26, 27, and 28, 1979. The purposes
of the symposium were (1) to provide a forum for a state-of-the-art review and dis-
cussion of ongoing and recently-completed research projects dealing with the manage-
ment of solid wastes; (2) to bring together people concerned with municipal solid
waste management who can benefit from an exchange of ideas and information; and (3) to
provide an arena for the peer review of SHWRD's overall research approach. These
proceedings are a compilation of the papers presented by the symposium speakers. They
are arranged in order of presentation. Volume I, land disposal, covered four primary
technical areas: Pollutant Identification, Environmental Assessment, Control Tech-
nology, and Pollutant Transport. Volume II, Resource Recovery, covered five primary
technical areas: Evaluation of Equipment, Unit Operations, and Processes; Economics
and Impediments; Systems Analysis and Special Studies; Utilization of Recovered
Materials; and Environmental Impacts of Resource Recovery.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Leaching, Collection, Disposal, Soils,
Permeability, Gas
Solid waste management,
Municipal solid waste,
Leachate, Toxic, Waste
treatment lining,
Groundwater pollution
13B
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
437
20. SECURITY CLASS (Thispage}
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
427
•US GOVERNMENT PRINTING OFFICE 1979 -657-060/5438
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