EPA/600/2-91/025
July 1991
LANDFILL LEACHATE CLOGGING OF GEOTEXTILE (AND SOIL) FILTERS
by
Robert M. Koemer and George R. Koemer
Geosynthctic Research Institute
Drezel University
Philadelphia, Pennsylvania 19104
Cooperative Agreement No. CR-814965
Project Officer
Robert E. Landreth
Municipal Solid Waste and Residuals Management Branch
TOste Minimization, Destruction and Disposal Research Division
Cincinnati. Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI. OHIO 45268
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TECHNICAL REPORT DATA
fPlcese read Instruction: on the reverse before eompletin-¦
1. REPORT NO.
EPA/600/2-91/025
2.
3. f PB9 1-213660
a. TITLE and subtitle
LANDFILL LEACHATE CLOGGING
FILTERS
OF GEOTEXTILE (AND SOIL)
5. REPORT DATE
Julv 1991
6 PERFORMING ORGANIZATION CODE
7. AUTHORISI
Robert M. Koerner and George R. Koerner
8. PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Geosynthetic Research Institute
10. PROGRAM ELEMENT NO.
Drexel University
Philadelphia, PA 19104
11. CONTRACT/GRANT NO.
CR-814965
12. SPONSORING AGENCY NAME ANDAODRESS
Risk Reduction Engineering Laboratory - Cincinnati, OH
13. TYPE OF REPORT AND PERIOD COVERED
Complete
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
14. SPONSORING AGENCY CODE
EPA/600/14
15. supplementary notes
Robert E. Landreth (513) 569-7871
FTS: 684-7871
i6.abstract primary leachate collection system of most solid waste landfills contains
a filter layer which has historically been a granular soil. Recently, however, various
types of geotextile filters have been used to replace the natural soil filters. A
project using six different landfill leachates and aimed at investigating the functionin
of different geotextile filters is the focus of this 36 month long study.
The initial 12 months, referred to as Phase I, investigated flow rates in various
filters under aerobic conditions at six different landfill sites using the site-specific
leachates. The study inadvertently found that the overlying granular soil clogged as
much as the geotextile filter that was located downstream. The effects of different
types and styles of geotextiles was generally masked by the upstream soil clogging. An
important finding in this task was the biodegradation of the geotextiles was not
evidenced and was concluded to be a non-issue.
The subsequent 24 months of study, referred to as Phase 11(a), led to the developnen:
of a vastly improved flow rate monitoring device. .y
In a separate task, referred to as Phase 11(b) and conducted simultanteously with
Phase 11(a), biocide treated geosynthetics were utilized at the two sites with the most
aggressive leachates. While the biocides may have been effective in killing micro-
organisms, the remnants were as troublesome as the viable bacteria in creating subsequen :
clogging.
17.
KEY WORDS AND DOCUMENT ANALYSIS
3. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSati Held/Group
Desi gn
Landfill leachate, Soil
filters, Geosynthetics,
Municipal solid waste.
Soil clogging, Biological
cloggi ng
18. DISTRIBUT OR STATEMENT
19. SECURITY CLASS (This Report!
UNCLASSIFIED
21 . NO. Op PAG ES
RELEASE TO PUBLIC
20 SECURITY class , This ptiRC)
UNCLASSIFIED
22. fFICE
1
EPA Farm 2220—1 (Rev, a-7?) PREvioui
e:it'On is obsolete
t
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DISCLAIMER
The information In this document has been funded wholly by the United States
Environmental Protection Agency under Cooperative Agreement No. CR-814965 to the
Geosynthetic Research Institute of Drexel University in Philadelphia. Pennsylvania. It has
been subjected to the Agency's peer and administrative review, and It has been approved for
publication as an EPA document. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
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FOREWORD
Today's rapidly developing and changing technologies and Industrial products and
practices frequency carry with them the Increased generation of materials that. If Improperly
dealt with, can threaten both public health and the environment. The U. S. Environmental
Protection Agency Is charged by Congress with protecting the Nation's land, air. and water
resources. Under a mandate of national environmental laws, the agency strives to formulate
and implement actions leading to a compatible balance between human activities and the
ability of natural systems to support and nurture life. These laws direct the EPA to perform
research to define our environmental problems, measure the Impacts, and search for
solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing,
and managing research, development, and demonstration programs to provide an
authoritative, defensible engineering basis in support of the policies, programs, and
regulations of the EPA with respect to drinking water, wastewater, pesticides, toxic substances,
solid and hazardous wastes, and Superfund-related activities.
This publication is one of the products of that research and provides a vital
communication link between the researcher and the user community. This document focuses
on the generation of simulated field test data relevant to the design, construction and
performance of landfill leachate collection systems. The data provided influences design and
performance of all such systems which rely upon leachate collection and removal.
E. Timothy Oppelt. Director
Risk Reduction Engineering Laboratory
iii
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ABSTRACT
The primary leachate collection system of most solid waste landfills contains a filter
layer which has typically been a granular soil. Recently, however, various types of geotextlle
filters have been used to replace the natural soil filter. Natural soil filters are designed using
conventional geotechnical engineering practice and these techniques have been modified and
adapted for the design of geotextlle filters. A project using six different landfill leachates and
aimed at investigating the functioning of these filters Is the focus of this 36 month long study.
The initial 12 months, referred to as Phase I, investigated flow rates in geotextlle filters
under aerobic conditions at six different landfill sites using the site-specific leachates. The
study inadvertently found that the overlying granular soil clogged as much as the geotextlle
filter that was located downstream. The effects of different types and styles of geotextlles was
generally masked by the upstream soil clogging. A separate anaerobic incubation task under
no-flow conditions showed clogging to be present but to a significantly lesser extent than with
the aerobic flow tests. This clogging was felt to be completely biological in nature rather than a
combination of sediment and biological processes. An important finding in this task was that
blodegradatlon of the geotextlles was not evidenced and was concluded to be a non-Issue.
The subsequent 24 months of study, referred to as Phase II, led to the development of a
vastly improved flow rate monitoring device which has recently become an ASTM Standard
Test Method, i.e., D1987-91, available May 1. 1991. Using these new flow columns, which are
made from PVC fittings locally available at hardware stores and are very inexpensive, a wide
range of variables were evaluated:
• four different styles of geotextlles
• geotextlle alone versus sand/geotextile filters
• anaerobic versus aerobic conditions
• six (very different) landfill leachates
The above 96 columns (4 x 2x 2x 6) were evaluated for their flow rate behavior over time and
found to essentially replicate the first year's aerobic test results. Varying degrees of clogging by
sediment (particulates) and micro-organisms did occur for the various geotextlle and natural
soil filters which were evaluated.
After establishing this point, a series of remediation attempts were evaluated. The flow
rate conditions showed measurable improvement. Water backflushlng was the most effective,
leachate backilushing and nitrogen gas backflushlng were intermediate, and vacuum
extraction was least effective. If remediation Is attempted, the periodicity of remediation
should probably be on a six month cycle.
iv
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In a separate third task, bioclde treated geosynthetlcs were utilized at the two sites with
the most aggressive leachates. While the blocldes may have been effective in killing micro-
organisms, the remnants were as troublesome as the viable bacteria in creating subsequent
clogging.
As final recommendations regarding geotextlle and soil filters placed over different
types of leachate drains It is felt that:
(a) Under the continuous flow of landfill leachate a gradually decreasing flow rate will
occur for all types of filters (soli or geotextlle) eventually reaching a terminal value.
(b) The terminal value of flow rate will vary according to the type of filter, the type of
leachate and the hydraulic gradient.
(c) The terminal flow rate for any given filter system must be compared to the design
required flow rate to ultimately assess the adequacy of the filter's design.
(d) Design criteria should be developed which considers the amount, size and type of
microorganisms and sediment present in the leachate along with conventional issues
such as hydraulic gradient and type of filter.
(e) Leachate collection systems at landfills which are decommissioned, or exhumed for
other reasons, should be investigated In light of the above recommendations.
(0 This particular project should be followed by another effort aimed at a larger variety
of geotextlle filters along with design guidance and field performance of existing
systems.
v
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Intentionally Blank Page
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CONTENTS
Page
Disclaimer 11
Foreword ill
Abstract lv
Figures v i i i
Tables i x
Acknowledgements xi
• Introduction and Scope 1
• Geotextlles and Soils Used In this Study 6
• Landfill Site and Leachate Characteristics 10
• Phase 1 - First Year Study 15
• Aerobic Flow Tests and Results 15
• Anaerobic Flow and Strength Tests and Results 30
• Summary of Phase I Study 37
• Phase II - Second/Third Year Study 40
• Incubation Columns and Testing Procedures 40
• Flow rates and Remediation Attempts 46
• Summary of Phase D Study 58
• Conclusions 61
• Recommendations 65
References 66
Appendices
A: Behavior of Bloclde Treated Geosynthetlcs 67
B: Individual Test Column Results of Phase n Study 89
C: Proposed Test Device and Method to Assess Filter Clogging 137
vi i
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FIGURES
Number Page
1 Generalized Cross Sections of Primary Leachate Collection Systems for
Solid Waste Landfills 4
2 Particle Size Range of Sediment and Mlcro-Organisms In the Landfill
Leachate with Ottawa Sand Shown for Comparison 13
3 Total Bacteria Count and Viable (Living) Count of Leachate Samples from
the Six Landfill Sites Evaluated in This Study, after Rios and Gealt'6' 14
4 Aerobic Flow Rate Test Setups and Photographs of the Actual Flow
Tests in Operation 16
5 Aerobic Flow Rate Test Results for all Geotextlles at Site PA-1 18
6 Aerobic Flow Rate Test Results for all Geotextlles at Site NY-2 19
6 Aerobic Flow Rate Test Results for all Geotextlles at Site DE-3 20
8 Aerobic Flow Rate Test Results for all Geotextlles at Site NJ-4 21
9 Aerobic Flow Rate Test Results for all Geotextlles at Site MD-5 22
10 Aerobic Flow Rate Test Results for all Geotextlles at Site PA-6 23
11 Exhumed Aerobic Flow Rate Test Setup Showing Clogged Geotextlle
Conditions (Geotextlle VV(C)-PP at Landfill Site PA-1) 24
12 Samples of the NW(N)-PET Geotextlles and the Overlying 6" of Ottawa
Sand Soil from the Various Landfills Sites After Twelve Months of
Aerobic Flow Testing 27
13 Anaerobic Incubation Drums with Geotextlles Immersed in Leachate
In Sets of Twelve Geotextlles of Each Type 31
14 Condition of Geotextlles After Six Months of Anaerobic Incubation at
Site NJ-4. Lower Photographs are Scanning Electron Micrographs of
Sediment and Growth on Selected Fibers: Left is Woven Fabric at 30
Magnification - Right is Nonwoven Fabric at 400 Magnification 34
15 Cross Section of Individual Flow Column and Storage Rack used to
Contain the Flow Columns When Not is Use at the Landfill Sites 41
16 Flow Column and Hydraulic Head Control Devices for Constant
Head Tests 43
17 Flow Column and Hydraulic Head Control Devices for Variable
(or Falling) Head Tests 44
18 Results of Continuous Leachate Flow Testing of Soil/Geotextlle
Column at DE-3 and NJ-4 Sites Based on Variable Head Tests 45
19 Average Response of Ninety-Six Flow Rate Columns from Phase II
Activities 63
v i i i
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TABLES j
Number Page
1 Characteristics of Leachates Generated In a Landfill by Solid Waste
Materials, after Chlan and DeWallef1' 2
2 Description of Geotextlles Used in Phase One of This Study 7
3 Description of Geotextlles Used in Phase Two of This Study 8
4 Details of Municipal Landfill Leachates Evaluated in this Study and
Approximate Leachate Characteristics 11
5 Results of Aerobic Flow Rate Tests After 12 Months of Evaluation in
Phase I Study (Percentages Given are Flow Rate Reductions Compared
to the Initial or As-Received Values) 29
6 Results of Anaerobic Flow Rate Tests (Percentages Given are Flow Rate
Reductions Compared to the Initial or As-Received Values; N/C Indicates
'no change") 33
7 Results of Anaerobic Strength Tests (Percentages Given are Strength
Reductions Compared to the Initial, or As-Received Values; N/C
indicates "no change") 36
8 Flow Rate Behavior and Percent Reduction in Flow Rate Due to
Biological Clogging During Initial Six (6) Months of Evaluation 47
9 Flow Rate Behavior and Percent Reduction in Flow Rates from
Biological Clogging after First Treatment at Six (6) Months Duration
(Backflush was with Site Specific Leachate) 48
10 Flow Rate Behavior and Percent Reduction In Flow Rate from Biological
Clogging Due to Four Months of Evaluation Following First Treatment
(Ten Months Total Exposure) 49
11 Flow Rate Behavior and Percent Reduction in Flow Rate from Biological
Clogging after Second Treatment at Ten (10) Months Duration
(Backflush was with Tap Water) 50
12 Flow Rate Behavior and Percent Reduction In Flow Rate from Biological
Clogging Due to Five (5) Months of Evaluation Following Second
Treatment (15 Months Total) 51
13 Flow Rate Behavior and Percent Reduction in Flow Rate from Biological
Clogging After Third Treatment at Fifteen (15) Months Duration
(Nitrogen Gas Backflush) 52
14 Flow Rate Behavior and Percent Reduction in Flow Rate from Biological
Clogging Due to Three (3) Months of Evaluation Following Nitrogen
Gas Backflush (18 Months Total) 53
15 Flow Rate Behavior and Percent Reduction In Flow Rate from Biological
Clogging After Fourth Treatment at Eighteen (18) Months Duration
(Vacuum Extraction) 54
ix
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Number Page
16 Flow Rate Behavior and Percent Reduction In Flow Rate from Biological
Clogging Due to Two (2) Months of Evaluation Following Fourth
Treatment (20 Months Total) 55
17 Flow Rate Recovery with Respect to Various Remediation Attempts 59
x
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ACKNOWLEDGEMENTS
nils study was funded by the U.S. Environmental Protection Agency under Cooperative
Agreement No. CR-814965. Robert E. Landreth was the Project Officer. Our sincere
appreciation Is extended to both the Agency and Mr. Landreth for this opportunity.
The cooperation of the six landfill owner/operators whose sites were utilized in this
study was also invaluable. We ofTer this acknowledgement anonymously at the respect of their
wishes.
Initial startup funding for the project was provided by the Hoechst-Celanese Corporation
of Spartanburg, South Carolina: Polyfelt, inc. of Evergreen, Alabama; and Terraflx
Geosynthetics. Inc. of Rexdale. Ontario. Canada. Geotextlles and geonets were donated by
numerous manufacturers. Blocldes were donated by the Ventron Division of Morton Thiokol,
Inc. of Danvers, Massachusetts. We thank all who were involved. Discussions with Gregory N.
Richardson of ENSC1, Inc. of High Point, North Carolina were very helpful in formulation of
the project scope and experiments.
Peer review of this final report has been provided by the thirty-nine (39) companies
comprising the Geosynthetic Research Institute.
Gundle Lining Systems. Inc.
Westinghouse E & GS, Inc.
U.S. Environmental Protection Agency
Polyfelt, Inc.
Waste Management, Inc.
Hoechst Celanese Corp.
Browning-Ferris Industries
Monsanto Company
E. I. Du Pont de Nemours & Co.. Inc.
Federal Highway Administration
Golder Associates, Inc.
Mirafl. Inc.
Tensar Earth Technology, Inc.
Fluid Systems, Inc. /National Seal Co.
Poly-America, Inc.
Union Carbide Corporation
Stevens Elastomerics Corp.
Akzo Industrial Systems bv
Phillips Petroleum Co.
SLT Environmental. Inc.
Exxon Chemical Co.
GeoSyntec Consultants. Inc.
Laidlaw Waste Systems, Ltd.
Nllex/Nova Corporation
Wfehran EnvlroTech, Inc.
Tenax, S.p.A.
Chambers Development Co.. Inc.
Amoco Fabrics and Fibers Co.
U.S. Bureau of Reclamation
Emcon Associates. Inc.
Hlmont, Inc.
Conwed Plastics Co.
Nicolon Corporation
James Clem Corporation
Occidental Chemical Corp.
American Colloid Co.
Accullner. Inc.
Richardson and Associates, Inc.
J &l L Engineering and Testing Co.
xi
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INTRODUCTION AND SCOPE
The management of liquids within a landfill represents a key element In their proper
functioning and overall design concept. The liquid Itself comes from moisture within the
waste as It Is received and placed In the facility, plus any precipitation that falls on the site
during its working lifetime. This total liquid Is referred to as "leachate" since it leaches
various constituents from the waste itself. Leachate varies greatly both in quality and In
quantity.
Regarding the quality of leachate. It la directly related to the nature of the solid waste
placed in the facility. One would naturally expect that hazardous waste leachate would be
different from non-hazardous, or domestic, waste leachate: but there Is even tremendous
difference within each of these categories. Chlan and De Wallet published data on the nature
of domestic landfill leachates Illustrating how leachates vary tremendously In their quality,
see Table 1. Recently EPA(2) and Haxo^3' have reviewed landfill leachate collected In the 1980 s
and found numerous changes In the chemical composition. However these studies were
directed at the chemical resistance of the liner system. The focus of this study is on filter
clogging (rather than liner degradation) in which the precipitates and micro-organisms are of
primary interest. Regarding the quantity of leachate. both the waste itself and the geographic
location of the facility' are important. For example, sewage sludge Is often intermingled with
municipal solid waste resulting in a much higher liquid content than a landfill accepting
construction demolition debris. Perhaps more Importantly, as far as leachate quantity is
concerned.is the geographic location of the landfill vis-a-vis the local amount of precipitation.
Identical landfills sited in the Seattle. Philadelphia and Las Vegas areas will have quantities of
leachate directly reflecting their local precipitation, i.e., a greater quantity would be generated
In Seattle than in Philadelphia, which In turn will be greater than Las Vegas. The HELP
computer model Is a valuable tool in estimating leachate quantities, see Schroeder, et aU4'
Whatever the quality and quantity of leachate. it will move gravltationally
downgradlent through the waste material to the base of the landfill where it encounters the
primary leachate collection and removal system. Here the leachate is accepted into a drainage
layer (generally gravel, but also other high permeability material like geonets and
geocomposltes), where it travels to a perforated pipe system. Within the perforated pipe, its
velocity is greatly increased as it travels to a sump area at the low elevation end of the facility.
A submersible pump Is then used which lifts the collected leachate out of the sump Into a
manhole or large diameter pipe, where it is transported for proper treatment and subsequent
1
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Table 1 - Characteristics of Leachates Generated in a Landfill by Solid Waste Materials,
after Chian and DeWalle'1'
Property Measured
Value (mg/U*
Chemical oxygen demand (COD)
40 - 89.520
Biological oxygen demand (BOD)
81 - 33.360
Total organic carbon fTOC)
256 - 28,000
PH
3.7- 8.5
Total solids (TS)
0- 59.200
Total dissolved solids (TDS)
584 - 44.900
Total suspended solids (TSS)
10- 700
Specific conductance
2810- 16.800
Alkalinity (CaCC>3)
0 - 20.800
Hardness (CaCC^)
0- 22,800
Total phosphorus (P)
0- 130
Ortho-phosphorus (P)
6.5- 85
NH4 - N
0- 1106
no3 + no2- n
0.2- 10.29
Calcium (Ca2+)
60- 7200
Chlorine (CD
4.7- 2467
Sodium (Na+)
0- 7700
Sulfate (-S03)2+
1- 1558
Manganese (Mn)
0.09- 125
Magnesium (Mg)
17- 15,600
Iron (Fe)
0- 2,820
Zinc (Zn)
0- 370
Copper (Cu)
0- 9.9
Cadmium (Ca)
0.03- 17
Lead (Pb)
SO. 10 - 2.0
•All values In milligrams per liter, except specific conductance, which Is In micro selsmens per
centimeter, and pH. which Is In pH units.
2
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disposal. Figure 1 shows two different concepts of the general scheme Just described. One
concept has entirely natural soil materials and the other is a hybrid between natural and
geosynthetic materials.
One important item not mentioned previously, but Is Illustrated In both profiles In
Figure 1, is the filter material located between the waste and drainage material. In Figure 1(a)
it is depicted as a sand, while in Figure lfb) It Is shown as a geotextlle. This JUter layer is the
complete focus of this project
The logic of a filter layer placed upstream of a drainage layer in a landfill is the same as
that of a filter placed In an earth dam, behind a retaining wall, adjacent to a highway, etc.. I.e.,
Its function Is that of filtration. Three mechanisms are required for the success of such filter
materials:
• They must be sufficiently permeable to pass liquid while minimizing upstream pore
water pressure.
• They must be sufficiently tight to prevent excessive loss of upstream soil.
• They must not completely clog, or shutoff flow, during their service lifetime.
There Is a long, and quite successful, history pertaining to the use of natural soil filters In
geotechnlcal engineering and transportation engineering practice. Various theoretical and
empirical rules have been established to the point where a relatively high degree of confidence
exists. These concepts are taught regularly In colleges and universities In a number of
engineering and science courses.
The advent of geotextlle filters is a relatively recent event. Their use versus natural soil
filters is very provocative. They use less space, are easier to transport, are easier to place and
Invariably are less expensive. While there Is an ever growing list of successful geotextlle filters
(the earliest dating back to 1968, see Barrett'5'), their use with landfill leachate Instead of
water Is much less established. Thus, the Initial focus of this project was toward an
Investigation of geotextlle filters in the landfill environment. However, as the project
developed, it was recognized that the soil filters had to be re-examined In light of their leachate
filtration. Thus it will become evident that both geotextlle filters and natural soil filters have
drawn our attention and will be equally examined in this study.
The report covers the entirety of this three-year project which was performed In three
separate phases. The first phase (which lasted 12 months) turned out to be somewhat
exploratory. It resulted In the development of a testing program which was successful In Its
general findings but proved to be inadequate In providing specific detail, mainly due to an
3
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J
LEACHATE
SOLID WASTE
SAND FILTER
? PERFORATED
•a. pipe-::
GRAVEL
,« .• ,« ,« ,• ,• ,• ,• .• ,« .# .• .•
PRIMARY FML
(a) Natural Soil Collection System
LEACHATE
SOLID WASTE
GEONET
GEOTEXTILE FILTER
PERFORATED
¦ PIPE
GRAVEL
PRIMARY FflL
(b) Geosynthetic Collection System
Figure 1 - Generalized cross sections of primary leachate collection systems for solid waste
landfills
4
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Inadequate test setup methodology. It, however, will be presented In Its entirety since its
qualitative findings are relevant. The second phase (lasting 24 months), greatly improved on
the measurement methodology. This Improvement ultimately led to a test setup and a set of
procedures which has recently been adapted by ASTM as a Standard Test Method. It provided
quite extensive and detailed quantitative information. Within this second phase a number of
biological related clogging remediation techniques were Investigated.
A third effort was directed toward the study of bloclde treated geonets and geotextlles. It
was performed over a 14 month period coincident with the Phase II study. This study is
Included In this Report as Appendix "A". Collectively, results of these different Phases have
supplied the background Information leading toward our final conclusions and
recommendations.
5
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GEOTEXTILES AND SOILS USED IN THIS STUDY
Various cross sections of different materials, all of which attempt to simulate the
profiles shown in Figure 1, were utilized. The first phase of the study used a
sand/geotextlle/geonet cross section, as was Illustrated in Figure 1(b) and Is often located on
the sldewalls of a landfill. These tests were aerobic* and Involved percolating leachate moving
vertically through the sand and geotextlle, followed by horizontal flow within the geonet.
There also were parallel studies conducted on the various geotextiles which were constantly
submerged In leachate, thus anaerobic* conditions. The six different geotextiles are listed in
Table 2(a), with their relevant physical and mechanical properties given in Table 2(b). The
sand used in the aerobic tests was a subrounded uniform size, Ottawa sand with a 0.42 mm (No.
40 sieve) average particle size. Its hydraulic conductivity Is approximately 0.02 cm/sec (0.04
ft/min). Since the hydraulic conductivity of the sand is high. It was felt that clogging could
develop In either It or in the geotextlle. As will be seen later, usually the sand clogged before the
geotextlle.
The second phase of the study used sand/geotextile/gravel and geotextile/gravel cross
sections to simulate the sketches of Figures 1(b) and 1(a), respectively. They were constantly
counterpolnted against one another to see If either the sand or the geotextiles were more
susceptible to clogging. The geotextiles evaluated are given in Table 3(a), along with their
physical and mechanical properties which are included in Table 3(b). The sand used above the
geotextiles (when It was used) was again a subrounded. uniform size, Ottawa sand with a 0.42
mm (No. 40 sieve) average particle size. Its hydraulic conductivity is approximately 0.02
cm/sec (0.04 ft/mln). It was the same type of sand used In the tests of the first phase described
earlier. The gravel located beneath the geotextlle was 1.0 to 1.5 inch in diameter and was used
as a support when placing soil above the geotextlle. Its openings are so large that flow was
considered to be unimpeded when passing through this layer. Subsequent visual examination
after the testing was complete confirmed this assumption. Both aerobic and anaerobic
conditions were evaluated. The actual test device was vastly improved In contrast to the setup
used In the phase one tests.
•Aerobic, referring to alternately wet and dry conditions, and anaerobic, referring to
constantly saturated, will be used throughout this report. While the aerobic description is
accurate. It Is recognized that keeping a system saturated does not guarantee "complete"
anaerobic conditions. It does, however, describe how the samples were maintained and
subsequently tested.
6
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Table 2 - Description of Geotextlles Used In Phase One of This Study
(a) Description of Geotextlles
Type of Fabric
Polymer
Filament
Designation and
Used at Site Number
Construction
Type
Type
Polymer Type
1
2
3
4
5
6
woven monofilament
polypropylene
continuous
W (C)-PP
V
V
V
V
(calendered)
woven monofilament
polypropylene
continuous
W (N)-PP
V
V
V
(non-calendered)
nonwoven needled
polypropylene
continuous
NW (N)-PP1
V
V
V
V
V
V
nonwoven needled
polyester
continuous
NW (N)-PET
V
V
V
V
V
V
nonwoven needled
polypropylene
staple
NW (N)-PP2
V
V
nonwoven needled
polyethylene
continuous
NW (N)-PE
V
V
V
V
nonwoven heat bonded
polypropylene
continuous
NW (HS)-PP
V
V
(b) Physical and Mechanical Properties of Geotextlles
Hydraulic
Designation and Thickness'1'" Mass per Unit Area POA'2) AOS'3' Permittivity^4) Conductivity
Polymer Type (mil) (mm) (oz/yd2) (g/m2) (%) 0g5(mm) (Sieve No.) (sec-1) (cm/sec) (ft/mln)
W (C)-PP
14
0.36
5.9
200
4
0.21-0.15
70- 100
0.14
0.005
0.010
W (N)-PP
20
0.51
6.5
220
10
0.42-0.21
40-70
2.3
0.12
0.24
NW (N)-PP1
87
2.2
8.3
280
n/a
0.21-0.15
70-100
2.1
0.46
0.92
NW (N)-PET
75
1.9
7.1
240
n/a
0.21-0.15
70- 100
2.0
0.38
0.76
NW (N)-PP2
102
2.6
7.7
260
n/a
0.21-0.15
70-100
1.8
0.47
0.94
NW (N)-PE
110
2.8
13.3
450
n/a
0.21-0.15
70-100
0.96
0.27
0.54
NW (HB)-PP
17
0.43
4.1
140
n/a
-0.15
-100
0.65
0.028
0.056
* (1) Under 43 Ib/fl2 (2.0 kPa) normal pressure
(2) Percent open area
(3) Apparent opening size
(4) Constant head test at 2.0 In. (50 mm) head
-------
Table 3 - Description of Geotextlles Used In Phase Two of This Study
(a) Physical Description of Geotextlles
Type of Fabric
Construction
Polymer
Type
Filament
Type
Designation
1
Used at Site Number
2 3 4 5
6
woven monofilament
(non-calendered)
polypropylene
continuous
WM (NC)
V
yl
yl
V
J
nonwoven heat bonded
polypropylene
continuous
NW (HB)
V
V
V
V
/ V
V
nonwoven needled
polyester
continuous
NW (N) 16
V
V
V
V
V
V
nonwoven needled
polyester
continuous
NW (N) 8
V
V
V
V
V
V
(b) Physical and Mechanical Properties of Geotextlles
Hydraulic
Designation Thickness'1'* Mass per Unit Area POA'2' AOS'3' Permittivity'4' Conductivity
(mil) (mm) (oz/yd2) (g/m2) (%) 0g5(mm) (Sieve No.) (sec-1) (cm/sec) (ft/mln)
WM (NC)
24
0.61
7.0
240
6.0
0.21
70
1.2
0.073
0.14
NW (HB)
16
0.41
4.0
140
n/a
0.21-0.15
70-100
0.6
0.025
0.049
NW (N) 16
195
4.9
16.0
540
n/a
0.21
70
0.7
0.35
0.69
NW (N) 8
93
2.4
8.0
270
n/a
0.15
100
1.4
0.33
0.65
• (1) Under 43 lb/ft2 (2.0 kPa) normal pressure
(2) Percent open area
(3) Apparent opening size
(4) Constant head test at 2.0 In. (50 mm) head
-------
The bloclde study mimicked the second phase of testing, with the exception that the
geotextlles (or geonets) were manufactured with the inclusion of vaiylng amounts of bloclde.
The geotextlles and sand that were used, along with the results, are Included in Appendix "A".
9
-------
LANDFILL SITE AND LEACHATE CHARACTERISTICS
Upon obtaining proper authorization and permission from the respective facility
owners, six landfills located within 200 miles of Philadelphia, Pennsylvania were utilized for
this study*. All six sites were used for the entire duration of this three year study. All were
municipal (i.e.. domestic) landfills, however, some were Intermingled with industrial waste of
various types and amounts. The amount of waste placed at each site vailed tremendously; from
100 to 8,000 tons per day. Perhaps more Importantly, the leachate management scheme, along
with the age of the facilities varied; thus, the quality of the leachate varied greatly. Table 4
gives what we feel are the most Important leachate characteristics for the purpose of filter
assessment. Le., the pH. COD. TS and BODsvalues. Table 4(a) gives the values at the time of the
project's start-up, and Table 4(b) gives the comparable values at the project's completion some
three years later.
To be noted from the COD, TS and BOD5 values listed in Table 4 is that each set of data
appears related to a particular landfill's leachate. In essence, when the COD Is high, so are the
TS and BOD5 values; similarly when one Is low, the others are also low. (There Is no clear
relationship to the pH values.) An ordering of the leachate strengths at the beginning of the
study ranging from "strongest" to "weakest" can be established as follows:
NJ4 strongest leachate
DE3 T
NY 2
PA 1 to
PA6 I
MD5 weakest leachate
Furthermore, there are additional clearly distinct differences between the NJ4 and DE3
leachates, both of which are very strong, and the NY2, PA1, PA6 and MD5 leachates, all of
which are relatively weak. It was anticipated that this general trend in leachate quality should
have some relationship with the long term flow trends to be established in the actual testing.
Two values in this table are particularly significant, the total solids (TS) and the biochemical
oxygen demand (BOD). It stands to reason that the higher the TS value, the more sediment and
particulate material is in the leachate; and the filter (either natural soil or geotextile) must
cope with this fine material. It is important to note that filters are designed on the basis of
their upstream soil particles and not on the sediment or turbidity of the liquid passing through
them. In a similar manner, the higher the BOD values, the more micro-organisms (various
•Ail sites will remain anonymous In this Report. We sincerely thank the owners of these
facilities for giving us access to their sites and extend special appreciation to the field
personnel for their excellent cooperation.
10
-------
Table 4 - Details of Municipal Landfill Leachates Evaluated In this Study and Approximate Leachate Characteristics
(a) Characteristics at the Start-Up Date for Each Site
Site
Designation
Start-Up
Date
Leachate Management
Scheme
Approximate Leachate Characteristics at Start-Up
pH
COD (mg/L)*
TS (mg/L)
BOD5 (mg/L)
PA-1
Nov. 18. 1987
Continuously Removed
8.0
15.000
8,000
2,000
NY-2
Dec. 10, 1987
Recycled through Landfill
and Continuously Removed
5.5
20.000
8,000
5,000
DE-3
Jan. 25. 1988
Recycled through Landfill
5.8
40.000
17,000
24.000
NJ-4
April 5, 1988
Continuously Removed
7.4
45.000
16,000
25.000
MD-5
June 6. 1988
Continuously Removed
6.8
1.000
100
150
PA-6
June 28, 1988
Continuously Removed
6.5
10.000
5,000
2,500
(b) Characteristics at the Termination of the Project for Each Site
Site
Designation
Date of
Final Readings
Leachate Management
Scheme
Approximate Leachate Characteristics at Completion
PH
COD (mg/L)
TS (mg/L)
BOD5 (mg/L)
PA-1
Oct. 29. 1990
Continuously Removed
8.0
10,500
5,000
3,000
NY-2
Oct. 30. 1990
Continuously Removed
6.3
13.000
7.000
5.000
DE-3
Oct. 31. 1990
Recycled through Landfill
6.5
25,000
15,000
15.000
NJ-4
Oct. 30. 1990
Continuously Removed
7.0
30.000
17,000
17,000
MD-5
Oct . 31. 1990
Continuously Removed
7.1
17.000
20,000
7,000
PA-6
Oct. 29. 1990
Continuously Removed
6.3
7,000
18,000
2,500
•COD
TS
BOD5
= chemical oxygen demand
= total solids content
= biochemical oxygen demand at five days
-------
forms of bacteria) that are present in the leachate. Here again, the filter must cope with these
micro-organisms with the hope that they will pass through the filter and be removed with the
leachate from within the downgradlent sump area. An Indication of the size of the sediment
and micro-organisms In the six different leachates is given In Figure 2. Both types of
particulates fall in a relatively tight size range almost entirely within the silt-size
classification. For comparison purposes, the particle size of the Ottawa sand used above the
geotextlles is also shown.
In addition to the high BOD5 values shown In Table 4(a). a further Indication of the
bacteria present in the leachates at the six selected landfill sites is given In Figure 3. Figure 3(a)
presents the number of biological cells per milliliter of leachate established by total direct
count. Note that the vertical scale Is logarithmic and the values range between 10® and 109
cells per ml. The values were obtained microscopically in a separate study which is given in
detail In Rios and Gealt'6*. Within this total count, the number of living cells, called the
"viable titer" Is given in Figure 3(b). While considerable scatter exists, the numbers are still
huge, i.e., between 106 and 107 living biological cells exist per ml of leachate. This represents
35 to 60% of the total count. Other details as to likely type of bacteria, techniques for counting,
etc.. are given In the reference cited. As anticipated, biological activity exists in municipal
waste landfill leachates on a massive scale.
Lastly, the possibility of a clogging synergism between sediment in the leachate coupled
with high micro-organism content cannot be discounted. Indeed there are references available
suggesting the possibility oflandfill drainage system clogging. Bass'7' presented several case
histories of sedimentation, biological growth and chemical precipitation clogging of leachate
collection systems. He states, "It would be difficult to rule out biological clogging as a failure
mechanism based on first principles". Ramke^> states In his report on German landfill
experiences, "the most frequent cause for failure Is formation of deposits in the seepage water
collectors or In the filter layer".
Thus, the realization that some clogging of collection systems might occur should be
acknowledged. What remains at issue is what is the degree of clogging: and. If felt to be
excessive, what techniques are available to remediate the situation. This research effort,
presented In separate phases, attempts to answer these questions. Phase One Is for 12 months
duration and Phase Two (with Improved monitoring devices and a series of remediation
attempts) Is for 24 months duration. They will be presented sequentially In the next two
Chapters. Phase Three, on bloclde treated geotextlles and geonets is Included as an Appendix.
12
-------
Gravel
Sand
Coarse to
medium
Fine
Silt
Clay
«
a
US E
5 R j
i i i
landard siei
§ \
i
i€ sizes
i
c
u
w
0
a
Leachate
Range
Ottawa
Sand
Grain diameter. mm
Figure 2 - Particle size range of sediment and micro-organisms In the landfill leachates with
Ottawa sand shown for comparison
13
-------
Total Direct Count
Apr. Uay Jun.
Month
Aug. Sept.
Viable Titer
10
P 10°-
Uar. Apr. Uay Jul
Month
Aug. S#pL
Figure 3 - Total bacteria count and viable (living) count of leachate samples from the six
landfill slles evaluated in this study, after Rlos and Gealt'6'
14
-------
PHASE I - FIRST YEAR STUDY
This phase of the project, which lasted for 12 months, was focused toward direct
simulation of soll/geotextile/geonet cross sections under aerobic conditions and of immersed
geotextiles In isolation under anaerobic conditions.
Aerobic Flow Tests and Results
The Initial portion of primary leachate flow in a landfill during its filling operations is
clearly aerobic. Furthermore, the collection area around the primary leachate removal sump
and manhole may also be functioning under aerobic conditions. In order to model these
situations, flow boxes of the type shown in Figure 4 were constructed. They were made to
simulate the bottom of a landfill with the geotextlle as the filter over a drain; in this case a
geonet drain. Whether the drain is a geonet, gravel or perforated pipe, however. Is of little direct
consequence since biological and precipitate clogging Is more apt to occur in the small spaces
of the filter rather than the significantly larger voids of the drain, whatever Its type. The use of
the open graded Ottawa sand above the geotextlle filters was done so that better flow control
could be maintained during the 12 month long tests. The use of sand over the geotextlle was
meant to simulate a soli working blanket which is often placed above the primary leachate
collection system before solid waste filling begins.
The wooden boxes used for these aerobic flow tests were 24 in. high with a cross section
measuring 12 in. by 12 in. They were made leakproof by silicon caulking and were then
painted with epoxy paint. The bottom portion of the boxes are flanged such that various
geotextiles can be incorporated in them. For all of these tests, a geonet is located beneath the
different geotextiles being investigated. A wooden base plate Is directly beneath the geonet and
it is bolted to the upper box flanges and caulked on three sides. The fourth side (i.e., the front of
the box) Is open which permits conveyance of the leachate out of the geonet drain after It passes
through the soll/geotextile system, see the lower right side photograph of Figure 4. Ottawa sand
(poorly graded, rounded particles, retained on a No. 40 size sieve! Is placed on the geotextlle to a
depth of 6 in. leaving the upper 18 In. of the box available for falling head leachate tests.
Sets of at least four boxes (and sometimes as many as six If the landfill owners wished to
evaluate their specific materials and cross sections) are setup at the landfill site near the
reservoir or underground storage tanks where the leachate Is temporarily stored. Usually the
boxes are housed in a small shed or maintenance building with no temperature nor humidity
control. Thus, ambient conditions prevail, e.g.. during the winter months the boxes
undoubtedly experienced freezing conditions numerous times.
15
-------
Leachate
Sand
Sand
Sand
Sand
Geotextiles
Geonet Drain (typ.)
Drain
Figure 4 - Aerobic Dow rate test setups and photographs of the actual flow tests In operation
16
-------
The leachate from a particular landfill site is pumped to the experimental flow system
either directly from the landfill sump area or from storage tanks located either above or below
ground. Leachate dousing is performed on a periodic basis, which Is either once or twice a
month. Otherwise, the boxes and their contents are either moist or nearly dry. Thus aerobic
conditions are assured. On monthly Intervals, flow rate tests of a falling head nature are
conducted. The time of flight for the head to fall from 24 to 18 in.: from 18 to 12 in. and from 12
to 6 in. (Le., to the top of the sand] Is measured. The resulting value obtained is the flow rate per
unit area, or "flux". It Is measured in units of gallons per minute per square foot of surface area,
i.e. gal/mln-ft2. The results of these tests for the seven geotextlles at the six landfill sites over
the 12-month test period are given as Figures 5 through 10. The actual data Is given in
Reference 9. They are coded according to the geotextile types listed in Table 2 and the landfill
designations listed in Table 4. The following observations are made on the basis of the trends
that are established in these figures.
(a) Flow rates measured after the Initial startup always decreased over time. Usually
the initial decrease was quite sharp.
(b) For most cases, the decrease then continued with either a linear, slightly
exponential or sharply exponential trend.
(c) In some cases the flow rate decreased to a level that was not measurable, at least
within the limits of our experimental system.
(d) There was some undulation of the flow rate trends which might be related to
temperature effects, I.e., low viscosity (hence high flow rates) during summer
months and/or high viscosity and perhaps frozen zones [hence low flow rates)
during winter months.
(e) Regarding landfill site PA-1, the W(C)-PP geotextile clogged below detection limits
within 4,5 months. This woven geotextile has a 4% open area and when exhumed
was seen to be embedded with particulates to a high degree. Figure 11 shows
photographs of this box as it was disassembled and the resulting condition of the -
geotextile. The lower photograph shows the open geotextile around the edges which
was under the flanged portions of the box and not exposed to leachate flow. Also
noted was a color difference (it was rust colored) In the sand above the geotextile.
This appears to Indicate the occurrence of biological clogging via iron and/or
manganese precipitation. This particular box was replaced by the W(N]-PP
geotextile with a 10% open area and Its performance over the subsequent 6.5
17
-------
.AEROBIC FLOW TEST
pai w(cypp
1 1 i "¦ i i i
2 3 4 5 6
7 8 9 10 1112
TIME (months)
12'
¦
24- b i r
10-
•
ir d i t
<
¦
12-to r
e-
¦
c
-PP1
¦
24- ia ir
•
ir to 12"
¦
12'tO 6"
10 11 12
TIME (monlhs)
12
io i
e
6
41b
2
0
.AEROBIC FLOW TEST
PA1 NW(N>-PET
•
24-to 1 r
•
16" to <2-
¦
12 ¦ to r
1 2 3 4 5 6 7 B 9101112
TIME (months)
.AEROBIC FLOW TEST
PA1 NW(N)-PP2
cj 10-
¦ 24" so 18'
• irioir
¦ 12 "to
r
¦
¦
¦
¦
2 3 45 67 8 9101112
TIME (months)
x
D
12
10
s
6
4
2
0
AEROBIC FLOW TEST
PA1 W(C)-PP
~ "RETEST
v..
a
24-10 ir
•
1 r io 1 t
¦
i2*w r
* I" t
234 567 09101112
TIME (months)
12
C\J
= 10^ ¦
c
I
«
® 6
D 4-
AEROBIC FLOW TEST
¦ PAI W(N)-PP
¦
24- :o i0"
•
i8Vd 12"
•
121 b 6"
i i i i ¦ i i ¦ r i i "» "t
0 1 2 3 4 5 6 7 8 9101112
TIME (monlhs)
Figure 5 - Aerobic flow rate test results for all geotextiles at Site PA-1
18
-------
.AEROBIC FLOW TEST
NY2 W(C)-PP
10 11 12
2 3 4 5 6 7
TIME (months)
12-
¦
24" 10 18"
•
18" 10 12"
cj 10-
¦
12-id r
c
I
<0
O)
X
3
"AEROBIC FLOW TEST
NY2 NW {N)-PP1
¦ 24":oir
• i8":oir
¦ 12" 10 6*
3 4 5 6 7
TIME (months)
III!
8 9 10 1112
"AEROBIC FLOW TEST
NY2 NW(N)-PET
12
¦
24" so 18"
•
18'D 1T
¦
12 ' 10 6*
i1 i-i
2 3 4
5 6 7
TIME (mornhs)
I I l'~T
B 9 10 1112
c
E
X
3
1 AEROBIC FLOW TEST
NY2 NW(N)-PP2
¦ 2<"to
1 0*
~ i r to i t
¦ 2 TO
$•
B ¦ ¦
n * 1 ¦ " 5
¦
¦ • ¦ i • , i a i
¦ . ¦
¦ a
4 5 6 7 8 9101112
TIME (months)
Figure 6 - Aerobic flow rate test results for all geotextlles at Site NY-2
19
-------
-AEROBIC FLOW TEST
DE3 w (cypp
10"
¦ 24"t0ir
• ir to ir
8-
¦
¦ 12 ¦ io r
i i i" i i i i i i i
23 4 5 67 6 9101112
TIME (months)
CJ
«
c
_c
E
CD
CD
X
3
"AEROBIC FLOW TEST
DE3 NW (N)-PP1
}*• 101 r
0 1 2 3 4 5 6 7 8 9101112
TIME (months)
12
DE3 NW(N>-PET
"i
m 24-B16"
• 18" to 12"
¦
m 12 -to 8"
\o
V ¦
1 Xi ¦ ¦
• ¦ ¦
¦
11 ¦ ii 7, !
¦
B •
¦ ¦ ¦ 11
¦
¦ i
4 5 6 7
TIME (months)
8 9 10 1112
12
ST 10
e
c
E
x
3
.AEROBIC FLOW TEST
DE3 NW (N)-PE
?<• io • r
18-toir
12-to 6-
I I I I I I I I I I
2 3 4 5 6 7 e 9101112
TIME (months)
¦AEROBIC FLOW TEST
DE3 W
-------
AEROBIC FLOW TEST
NJ4 NW{N)-PP1
¦ 24-10 19*
• 18" to 12*
¦ 12" tO 6"
w 10 ¦
LL
01 23456789101112
AEROBIC FLOW TEST
NJ4 W(C)-PP
¦ 24' to 18"
• 18"tDl2"
¦ ir»6*
re
o>
X
z>
-J
LL
0 1234567 89101112
TIME (month) TIME (month)
12"
10 ¦
e-
6 ¦
4
2i
0
.AEROBIC FLOW TEST
NJ4 (N)-PET
¦ . 1
¦
ji- io 18-
~
1F 10 12"
¦
12"!oe"
B o
¦ I I
«-*¦
'I I " I I' I 1 I "T I' T - I-
2 3 4 5 8 7 8 9 10 1112
TIME (month)
3
12
10
B
6
-J AEROBIC FLOW TEST —
NJ4 NW (N)-PE
B 24*10 18"
• 18" B 12"
¦ i2'»r
A"
¦V
. ;sh -
¦ ¦ ¦ a o a i
-j-i—
* D
0 12 3
4 5 6 7
TIME (month)
0 9 10 11 12
Figure 8 - Aerobic flow rate test results for all geotextiles at Site NJ-4
21
-------
12
10 " i
<
c 8"
S, 6
X -H
Z)
AEROBIC FLOW TEST
MD5 W(N)-PP
¦
24"to 18"
~
18" to 12"
¦
1 r ioe*
i- i i i i i i i i i i
0 1 2 34 567 89101112
TIME (month)
12
rT 10
<
3=
£ B
E
6
4
2
0
<9
O)
X
3
AEROBIC FLOW TEST
MD5 NW(N)-PP1
i i i
3 4 5
~ > r
6 7
B 24'toir
• irmr
¦ ir©r
¦
¦
•
¦ ¦
e 9 10 11 12
TIME (month)
AEROBIC FLOW TEST
¦ 24*10 IB"
• 1B-I01Z"
¦ 1ZM06-
CM 10
0 1 2 3 4 5 67 8 9101112
TIME (month)
12
o? 10
<
S 8
E
X
-------
AEROBIC FLOW TEST
PA6 W(N)-PP
¦
24" to 10"
~
18-10 ir
¦
irtor
1 i i i i i i i i i
2 3 4 5 67 8 9101112
TIME (monih)
12
10-
B-
« 6
X
A -
2-
AEROBIC FLOW TEST
PA6 NW(N)-PP1
0 1
¦
24-toie-
~
ir to ir
¦
irtoB-
-I 1 i i i i i i i i
2 3 4 5 6 7 6 9 10 11 12
TIME (month)
AEROBIC FLOW TEST
PA6 NW(N)-PET
24- to 1 er
1BT to 12"
1? lor
I '
~ I I I
2 3 4
i i
6 7
—i 1 i i
B 9 10 11 12
TIME (month)
12
S> 6
X *
AEROBIC FLOW TEST
PA6 NW(N)-PE
¦ 24" to 18"
~ inoir
.
¦ irio r
_ H _ ¦
fc- ¦ ' ¦ " ¦
i
' ^^1 m m
¦ a B -
¦ ¦ ¦ i:
¦ ¦ 1 ¦
0 1 23 45 67 8 9101112
TIME (month)
PA6 NW(HB)-PP
¦ 2<"tDi6"
¦
• 10" tt> \T
. °
¦ 12"*>6"
AEROBIC FLOW TEST
0 1 23 45 67 B 9101112
TIME (month)
Figure 10 - Aerobic flow rate test results for all geotextlles at Site PA-6
23
-------
Open
Geotextlle
Clogged —
Geotextlle
Figure 11 - Exhumed aerobic flow rate test setup showing dogged geotextlle conditions
(geotextlle W(C)-PP at landfill site PA-1)
2U
-------
months was reasonable, i.e.. the greater open area was effective In limiting the
amount of clogging. The three needle punched nonwoven geotextlles INW(N)-PP1,
NW(N)-PET and NW(N)-PP2] performed quite similarly to one another, all gradually
decreasing in flow rate over time but reaching apparent equilibrium flow
conditions.
(f) Regarding landfill site NY-2. the W(C)-PP geotextile (with the 4% open area) again
clogged severely, but now took the entire 12-month period to do so. The three
needle-punched nonwoven geotextlles [NW(X)-PP1, NW(N)-PET and NW|N)-PP2]
performed much better, and roughly equivalent to one another.
(g) Regarding landfill site DE-3 (which has a very strong leachate, recall Table 4), the
flow rate decreases were quite substantial. Again, the W(C)-PP geotextile with 4%
open area clogged to a degree where flow rates with our system could not be
measured. After seven months the flow rates were barely readable and after 12
months they were not readable. The three needle punched nonwovens INW(N)-PP1,
NW(N)-PET, and NW(N)-PE| also showed flow rate decreases but appear to have
stabilized after six months. Note that slight increases occurred between the 8th and
10th months and can only be explained as a "weaker" leachate at that particular
time. Note also the addition of NW(N)-PE (which is a polyethylene geotextile) and it
performs quite similarly to the polypropylene (PP) and polyester (PET) types. Thus,
the type of polymer from which the geotextile is manufactured appears to have
negligible significance.
(h) Regarding landfill site NJ-4. which has the "strongest" leachate, large flow rate
decreases are seen for all geotextlles. As with the preceding three landfill sites, the
W(C)-PP geotextile with 4% open area again clogged below detection limits, this time
within eight months. The three needle punched nonwovens |NW(N)-PP. NW(N)-PET
and NW(N)-PE] also had significant decreases. They behaved similarly to one
another and at the end of the 12 month period appeared to have stabilized at the
equilibrium values Indicated.
(1) Regarding landfill site MD-5, which has the "weakest" leachate of all sites, the flow
rate trends decrease but now only marginally. The W(N)-PP woven geotextile has a
10% open area and behaves significantly better than the W(C)-PP with lower percent
open area used at the previous four landfill sites. Clearly, the greater opening area
(from 4% to 10%) has a significant positive Influence. The three needle punched
nonwovens |NW(N)-PP1, NW(N)-PET and NW(N)-PE] perform similar to one another.
25
-------
again irrespective of polymer type. Added to this set of four geotextlles is a fifth box
containing a heat-bonded nonwoven geotextlJe NW(HB)-PP. Its performance Is
slightly poorer than the needle punched geotextlle types, but only nominally so.
Important is that all the geotextlles in this leachate reach equilibrium values before
the termination of the tests.
(J) Regarding landfill site PA-6, flow rates decrease but not significantly. The leachate
at this site is not very strong so the behavior Is understandable In light of the other
test results and their respective leachates. Clearly, the leachate type and
characteristics are seen to be of paramount Importance In the geotextlle clogging
Issue. Of the five geotextlles used at this site, the low percent open area woven
W(N)-PP and heat bonded nonwoven NW(HB)-PP dropped in flow rate from their
original values at a slightly greater rate than the three needle punched nonwqvens
|NW(N)-PP1, NW(N)-PET and NW(N)-PE|. All. however, reached a relatively high
equilibrium value.
The flow rate decreases presented In this section vary according to the type of leachate
and the type of geotextlle filter. This begs the question as to the mechanism(s) involved.
Shown in Table 4 was that all of the leachates contain very high solids content (as evidenced by
the TS values) and tremendously large amounts of bacteria (as evidenced by the BOD 5 values).
Thus, one could expect some amount of flow reduction as a response to the Influence of two
sources; sediment (particulate) matter and/or biologically oriented matter. Furthermore, the
two phenomena could be interacting with one another as is well established in the literature.
In order to visually examine the cross sections of the flow boxes after the 12-month flow
testing was complete, they were sampled with a 2.0 in. diameter thin-walled steel tube. This
tube was driven completely through the sand, geotextlle. geonet and wooden base plate. The
sampling tube was then cut ofT even with the top of the sand, turned upside down, and the
wooden box base plate was removed thereby exposing the bottom of the geonet. A low viscosity
epoxy was then poured Into the geonet. thereby flowing Into the geotextlle and then into the
sand. After hardening, the entire tube (with its sand, geotextlle and geonet contents) was cut
along Its diameter Into two halves. Upon opening the two halves, the cross-sections appeared
as shown In the photographs of Figure 12.
The upper photograph of Figure 12 shows the cross section of the needle punched
nonwoven polyester geotextlle |NW(N)-PET] at all six landfill sites after 12-months of leachate
flow testing. In the two cross sections of DE-3 and NJ-4. a very clear color change midway
through the sand layer can be noticed |see the lower photographs for some of this detail). The
26
-------
V
AEROBIC FLOW
SPECIMENS
12 MONTHS
ir- •
* "•*- - -
DE3 ^HIV ¦Bte.d HW
| « Clogged Sand
-Open Sand
-Geotextlle
Figure 12 - Samples of the NW(N)-PET geotextlles and the overlying 6" of Ottawa sand soil from
the various landfill sites after twelve months of aerobic flow testing
27
-------
upper rust color is clearly Indicative of Iron deposits typical of bacterial activity under aerobic
conditions. Note that these two sites with the major color changes had the strongest leachates
of all six sites. The other four cross sections of PA-1, NY-2. MD-5 and PA-6 also show residual
bacteria bonding within the sand, but without abrupt color changes. Clearly the influence of
strong leachates, such as DE-3 and NJ-4, are very much In evidence through examination of
these cross sections. Under high magnification, biological activity was seen to be present in all
samples throughout the six inches of Ottawa sand and into the geotextlJe filters. The
photographs are felt to be particularly significant in that biological activity occurs in sand
filters equally as much as It does in geotextUe filters. Furthermore, this sand filter has the
hydraulic conductivity (permeability) of some drainage layers, let alone most of the natural
soils used as filter lauers.
In summarizing these aerobic flow rate tests we find that flow reduction has occurred at
all six landfill sites. The relative amount, and the amount between different geotextiles varied
considerably. In order to view the total data set for comparative purposes. Table 5 has been
prepared. Here, the flow rate reductions are reported on the basis of their initial flow rate
values compared to the final 12-month values i.e., the percent flow rate retained. Some
observations concerning the aerobic flow rate results reported in this table follow:
(a) The woven geotextiles [W(C)-PP] with 4% open area had the largest flow rate
decreases, in three cases below experimental detection limits. This type of tightly
woven geotextlle should be questioned for use as a geotextlle filter for landfill
leachate with respect to the design required value.
(b) Using a similar type of woven fabric rw(N)-PP] but now with a 10% open area
produces reasonable and. In fact, quite good results.
(c) The trends and nominal differences between the four needle-punched nonwoven
fabrics [NW(N)-PP1. NW(N)-PET. NW(N)-PP2 and NW(N)-PE) all behaved similarly
and quite Independently of polymer type. Thus polypropylene, polyester and
polyethylene all are candidate polymers used to manufacture geotextlle filters in
leachate collection systems as far as flow rate behavior is concerned.
(d) Furthermore, all of the needle punched nonwoven geotextiles responded to the
various leachates In approximate relationship to the severity of leachate quality,
i.e. DE-3 and NJ-4 leachate, the harshest of all six landfill sites, produced the
largest flow rate reductions. The other four landfill sites PA-1, NY-2, MD-5 and
PA-6 with weaker leachates. resulted In lower flow rate reductions In approximate
proportion to their leachate strength.
28
-------
Table 5 - Results of Aerobic Flow Rate Tests After 12 Months of Evaluation In Phase I Study
(Percentages Given are Flow Rates Retained Compared to the Initial or As-Received
Values)
Site
Time
Aerobic Flow Rate Trends'1'
Designa-
tion
Startup
W(C)-PP
W(N)-PP
NW(N)-PP1
NW(N)-PET
NW(N)-PP2
NW(N)-PE
NW(HB)-PP
PA-1
11/18/87
0%I3>41
80%
85%
85%
85%
NY-2
12/10/87
10%
80%
80%
80%'21
DE-3
1/25/88
cn
o
20%
20%
25%
NJ-4
4/5/88
0%
20%
20%
10%
MD-5
6/6/88
90%
85%
85%
80%
75%
PA-6
6/28/88
90%
85%
85%
80%
70%
Notes:
111 flow rate tests within box (average of 24-18; 18-12; 12-6 In. falling head tests)
[21 the second PP geotextlle was changed at Site #3 to PE
[31 test clogged beyond detection limits and was restarted with higher POA fabric
14] retested
-------
(e) The heat-bonded nonwoven fabric [NW(HB)-PP] used at landfill sites MD-5 and PA-6
showed similar flow rate reductions as the needle punched nonwoven types.
(f) The sand overlying the above mentioned geotextlles was greatly affected by the
leachate. Sand clogging was contributing, to some unknown degree, throughout the
tests. This important issue will be evaluated in the Phase II study, and will be
presented In the conclusion portion of this report.
Anaerobic Flow and Strength Tests md Results
Soon after a landfill begins accepting appreciable quantities of solid waste, the available
oxygen is depleted and the situation at the bottom of the landfill becomes anaerobic. At the
level of the leachate collection system, this absence of air might even occur shortly after
placement of several lifts of waste. A clear indication of anaerobic conditions Is the presence
of methane gas, which occurs via anaerobic microorganisms interacting with the waste. This
portion of the study presents our simulation of this condition and the results of the subsequent
testing program.
To evaluate the anaerobic leachate effects on various geotexttle filters a completely
different strategy from the previous tests was taken. In this portion of the study it was decided
to Immerse 14 In. wide by 12 in. long geotextlle samples In 55 gallon drums filled with
leachate. The geotextlle test samples were placed on stainless steel racks within the drums In
sets of twelve for each of the four geotextlles evaluated at each site. Thus, the total anaerobic
test program consisted of 288 samples. See Figure 13 for a schematic diagram and photograph
of typical Incubation setup.
The leachate used for the incubation was taken from the landfill reservoir or storage
tank at the start-up dates listed In Table 4(a). Leachate characteristics are those listed in this
table and did not change during the course of the incubation. The drum lids were tightly sealed
at all times with the exception of once per month when the samples were removed from each
drum at each.landfill site. These samples were sealed In plastic bags and brought to our GRI
laboratory for Immediate testing and evaluation. For each geotextlle sample the following
tests were conducted.
• three permittivity tests'10'
• three radial transmisslvity tests'1 ^
• three Mullen burst tests'12'
• four 1.0 Inch wide strip tensile tests'13'
The flow tests were performed on the retrieved samples In two different directions. I.e.
now in the cross-plane direction (or permittivity) and flow in the in-plane direction (or
30
-------
55 gal Drum
55 gal Drum
Leachate
Leachate
Figure 13 - Anaerobic Incubation drums with geotextiles Immersed In leachate in sets of twelve
geotextites of each type
31
-------
transmisslvity). These tests were done on the samples in their as-retrieved leachate saturated
condition, however flow testing was performed with water.
The permittivity tests were done as stipulated in ASTM D-4491 with the exception of the
2 In. (50 mm) constant head. Our concern was that this value was too high and would
excessively wash the biological growth out of the geotextlle. Therefore we decided on use of a
0.5 in. (12 mm) constant head value. Three tests were done on each sample and the average
values were obtained. The data is given In Reference 9 since it consists of numerous sets of
information.
The transmisslvity tests were of the radial variety because this type of test requires
significantly less material than the planar test currently recommended by ASTM. The test is,
however, well behaved and is established in the literature. The radial transmisslvity test Is
performed under a constant head where liquid flows into a load bonnet and meets the inner
circumference of the donut-shaped test specimen. It then flows radially in the plane of the
geotextlle to the outer circumference where it is collected and measured. Calculations then
permit determination of the transmisslvity value. The tests performed in this study were all
done under a normal seating load of 43 lb/ft2 (2.0 kPa) and a constant head of 0.5 in. (12 mm).
As with the permittivity tests, the tabulated results are Included in Reference 9.
A complete photo-documentation of the anaerobic clogging of the geotextiles at each site
was compiled using a scanning electron microscope (SEM). This entire record is also presented
in Reference 9. The biological growth took very different forms at each of the different sites.
Also seen was that the biological colonies easily were detached from the fibers themselves, i.e.
a chemical bonding did not appear to have occurred, see Figure 14.
The averages of the permittivity and transmisslvity tests Just described were further
averaged with one another and are given in Table 6 following. Each landfill is listed separately
along with the specific geotextiles that were incubated in that particular geotextlle. From this
table It is seen that:
(a) The original flow rates decreased approximately 5% to 20% for all test specimens.
(b) The stronger leachates at landfill sites DE-3 and NJ-4 were associated with the
higher range of flow rate decreases.
(c) There was no particular sensitivity to geotextlle type nor to polymer type.
(d) These flow rate decreases are significantly less than the aerobic test results and are
lower than we suspected from viewing the exhumed geotextiles, note the condition
of geotextiles removed from Site NJ-4 after 6 months incubation in Figure 14.
32
-------
Table 6 - Results of Anaerobic Flow Rate Tests (Percentages Given are Flow Rates Retained Compared to the Initial or
As-Received Values; N/C indicates "nochange')
Site Startup W(C)PP W(N)PP NW(N)-PP1 NW(N)-PET NW(N)-PP2 NW(N)-PE NW(HB)-PP
Date
PA-1
11/18/87
90%
95%
95%
95%
NY-2
12/10/87
85%
90%
90%
90%
DE-3
1/25/88
80%
90%
90%
85%
NJ-4
4/5/88
80%
90%
90%
85%
MD-5
6/6/88
N/C
N/C
N/C
N/C
N/C
PA-6
6/28/88
N/C
N/C
N/C
95%
95%
Note:
All tests are the average of 3 permittivity and 3 transmlsslvity tests
-------
Figure 14 - Condition of geotextiles after six months of anaerobic Incubation at site NJ-4.
Lower photographs are scanning electron micrographs of sediment and growth on
selected fibers: Left Is woven fabric at 30 magnification.
Right Is nonwoven fabric at 400 magnification.
34
-------
(e) It is quite possible that the flow testing Iwith water] actually flushed some of the
biological growth and fine sediments out of the geotextlle. This situation was not
possible for the aerobic tests discussed previously.
(0 In comparing these flow rate reductions with the aerobic test results described
earlier It must be remembered that sand was not present in these tests; thus, flow
rate reductions should be significantly lower, and they were.
The Issue of biological degradation, or loss of strength, of geotextiles Is often expressed
by various groups, e.g.. regulators, owners and designers. Envisioned are microorganisms
which chemically attach themselves to the geotextUe's fibers and find molecular chain
endings from which degradation can occur. If such a mechanism occurs, It should be
evidenced by a loss of strength and/or a loss of elongation. Since numerous leachate
incubated geotextiles were available, it was decided to perform two types of strength tests;
burst and strip tensile tests. The resulting information from these tests conducted on
monthly exhumed geotextiles from each site are given In Reference 9. The geotextlle samples
brought from the sites were cut into test specimens and, for these strength tests, were air dried
before testing. These results were compared to the as-received, and nonlncubated, geotextiles
in the same type of tests. The results are summarized in Table 7 which follows.
Table 7 indicates that loss of strength from the various geotextiles at the six landfill sites
due to leachate incubation up to 12 months is a non-issue except for the nonwoven heat-bonded
polypropylene fabrics at sites MD-5 and PA-6. In regard to this strength loss, it is felt that
incubation within the leachate led to weakening of thermally fused fiber Junctions. Thus the
strength loss In this particular fabric Is felt to be the result of a physical effect rather than
being biologically motivated. With this exception. It appears that (within the accuracy of our
testing and observations on the photomicrographs of Reference 9) neither geotextlle strength
nor elongation suffered from the leachate exposure.
35
-------
Table 7 - Results of Anaerobic Strength Tests (Percentages Given are Strengths Retained Compared to the Initial,
or As-Received Values: N/C indicates "no change")
Site Startup W(C)PP W(N)PP NW(N)-PP1 NW(N)-PET NW(N)-PP2 NW(N)-PE NW(HB)-PP
PA-1
11/18/87
N/C
N/C
N/C
N/C
NY-2
12/10/87
N/C
N/C
N/C
N/C
DE-3
1/25/88
N/C
N/C
N/C
N/C
NJ-4
4/5/88
N/C
N/C
N/C
N/C
MD-5
6/6/88
N/C
N/C
N/C
N/C
70%
PA-6
6/28/88
N/C
N/C
N/C
N/C
70%
Note:
All data Is the average of 4-1 inch wide tensile tests and 3 Mullen burst tests
-------
Summary of Phase I Study
The results of the Phase I (first year's) study has shown that municipal landfill leachates
have tremendous numbers of biological micro-organisms present. For the six landfill
leachates evaluated, the bacterial content ranged from 10® to 109 cells per milliliter with 35 to
60% viability, i.e. live cells. This, in turn, is reflected by BOD5 levels varying from 1000 to
20.000 mg/1. Additionally, it was seen that a high total solids (TS) content (varying from 100 to
17.000 mg/1) always accompanied a high BOD content. The size of the sediment and micro-
organisms In the leachate varies from 2 to 100 microns, i.e., the particulates all fall within the
silt soil size range. It should be mentioned that all of the landfills evaluated In this study were
codisposed with industrial waste, but the nature and degree is unknown to the authors.
With this insight as to the nature and type of the particulates in the leachates, it was
decided to evaluate clogging under both aerobic and anaerobic conditions.
The aerobic portion oj the study used 12 In. x 12 in. flow boxes. 24 in. high. The boxes
were all constructed using a wooden base plate, a geonet drain, a geotextlle filter and 6 in. of
free draining sand. The remaining 18 in. of the boxes were empty so that falling head
permeability tests could be conducted . Leachate passed through the sand and geotextlle, then
flowed within the geonet which was open at one end only. The time of flight for given
(quantities of leachate to pass through the system was measured. Each of the six sites had at
least four boxes, the only difference being the type of geotextlle filter. Both woven and
nonwoven geotextlles were evaluated. They consisted of various polymer types and
manufacturing styles.
Based on the flow rate behavior over the 12-month evaluation period at each site, the
following conclusions are reached.
(a) Flow rate decreases from original values vary considerably. They range from full
reduction (within the limits of our detection system) to 10% reduction, with many
values being in the 80% to 20% reduction range,
fb) The relatively tight woven geotextlle filter, with a 4% open area, performed the
poorest. In each of the four different sites in which It was used, it clogged beyond our
detection limit. The time periods were from 4-1/2 to 12 months.
(c) Opening up the void space of the same type of woven geotextlle to a 10% open area
helped considerably. Flow rates still decreased but were more In line with the
needle punched nonwoven geotextlle types.
37
-------
(d) The needle punched nonwoven geotextiles performed equivalently. They were J
constructed similar to one another but were of different polymer types. Results
Indicate that polypropylene, polyester and polyethylene fibers do not appear to be
significantly different In their flow rate response behavior.
(e) A heat-bonded nonwoven geotextlle was used at two sites. Its response was
somewhat poorer than the needle punched nonwovens but better than the woven
geotextlle with 4% open area.
(f) The Phase I study Indicates that use of open woven geotextiles and each of the
needle-punched nonwoven geotextiles results in steady state flow conditions after
as little as 6 months, and almost always after 12 months. The flow rate reductions
varied from as low as 20% of the original values (at four sites) to as large as 80% (at
two sites). These reductions appeared to be related to the strength of the leachate
Insofar as their total solids (TS) and micro-organism content (BOD5) Is concerned.
In the worst cases, flow rates are usually above 1.0 gal/min-ft2. This Is equivalent
to 6.2 x 107 gal/acre-day which probably far exceeds most design requirements for
leachate collection system filters.
(g) The cause of the How reductions created somewhat of a dilemma. By cross
sectioning of the boxes at the end of the 12-month period, it was clearly evident that
the 6 In. of sand over the geotextlle was a major source of the flow reduction.
Clearly, the experiments showed that soil clogging is every bit as serious as
geotextile clogging. Furthermore, the soil which was used was a very open graded,
rounded sand [actually It was Ottawa sand) having a permeability coefficient
approximately 0.02 cm/sec (0.04 ft/mln). Thus, it actually meets (and exceeds) the
EPA criterion for a drainage soil, let alone a filter soil.
(h) Microscopic examination of the cross sectioned soil/geotextlle systems showed
heavy particulate clogging in the upper half of the soil layer. Thereafter the clogging
was either fibrous or consisted of very small clusters. Although not conclusively
proven, we feel that the upper portion of the soil column filtered the suspended
solids out of the leachate and thereafter biological activity spread throughout the
remaining portion of the soil column and into the underlying geotextlle. This
biological activity took numerous forms Including the deposition of solid
precipitates In the soil and geotextile voids. Thus different geotextiles (all other
things equal) responded differently to the same site's leachate.
38
-------
(l) The relative amounts of flow rate reduction between leachate sediment, biological
precipitates and biological growth could not be distinguished In these tests.
The anaerobic portion of the study was performed under completely submerged
conditions In 55 gal. drums. Twelve samples of each type of geotextlle were suspended on
stainless steel racks and placed in the site's leachate. One sample of each type was removed for
testing each month. Four geotextlle types were evaluated for each of the six landfill sites. After
removal of the samples they were brought to our laboratory and were tested for their retained
flow capability and possible strength reduction. The general conclusions are as follows:
(a) Relatively minor flow reductions occurred tri all types of geolextiLes evaluated. The
reduction values varied from 10% to 20%. Note, that these amounts are distinctly
less than occurred In most of the aerobic tests. The reason for this is that sediment
clogging was not Initiated since flow was not occurring during the incubation
periods. Furthermore, the absence of a soil column had a dramatic (but
quantitatively unknown) effect In Improving the flow rates.
(b) All of the exhumed geotextlles had heavy biological growth which could be easily
seen and felt.
(c) Scanning electron micrographs at various times of incubation (e.g.. 1, 3. 6 and 12
months), were compared to the as-received geotextlles, and were very
Informative.Here complete growth around the Individual fibers, or growth In
clusters, could be seen. While difficult to quantify, the amount of growth was clearly
related to the time of Immersion.
(d) The micrographs also revealed that the biological growth was easily removed from
the fiber's surfaces. There appeared to be no fixity or attachment to the fibers.
(e) The above observation was corroborated by various strength tests performed on the
geotextlles after immersion. Within the limits of our testing, there was no strength
reduction over the 12-month period. This suggests to us that for these leachates,
biological degradation of geotextiles is a nonproblem. Phase II studies will not
dwell upon the polymer degradation issue.
39
-------
PHASE n - SECOND/THIRD TEAR STUDY
Building upon the results of Phase I activities, Phase n of the project was aimed at
eliminating the objectionable features of the first phase and toward providing an opportunity
of remediating the filtration systems by various types of backflushlng. Furthermore, the focus
shifted from complete geotextlle filter clogging to a balance between geotextlle and soil filter
clogging. The new experimental test setups for this second phase were Intended to meet the
following criteria.
(a) Sand filter clogging should be distinguishable from geotextlle filter clogging.
(b) Sediment clogging should be distinguishable from biological clogging.
(c) Aerobic conditions should be distinguishable from anaerobic conditions.
(d) Identical geotextlles and soils should be used at every site.
(e) The flow columns should be capable of accommodating continuous or periodic flow
testing.
(0 The flow columns should use the leachate at the time of testing and not be stored for
any length of time lest It change In its composition and not represent site conditions.
(g) Constant head or variable head conditions should be capable of being
accommodated.
(h) The flow columns should be capable of being backflushed with liquids or gases and
the results assessed.
(1) The test setup should be adaptable to Include various blocide remediation attempts.
(]) Freezing of the test setups should be avoided.
(k) The flow columns should be sufficiently portable to evaluate in the sump, at the
leachate storage facility or in an enclosed space.
(1) The flow columns should be Inexpensive so that a large number can be constructed to
test a wide variety of filtration schemes.
Incubation Columns and Testing Procedures
In order to meet the experimental test device criteria Just described, incubation and flow
columns as shown in Figure 15 have been developed and are used throughout the Phase n study
and the blocide study which Is Included as Appendix "A".
The flow columns of Figure 15 are constructed from 4.0 In. diameter PVC pipe and related
fittings. Most large hardware stores and swimming pool accessory supply shops have these
Items In stock. The containment ring Is actually a pipe coupling which has a raised Inner "Hp"
upon which the geotextlle is placed and sealed. A non-water soluble adhesive is used to bond
the geotextlle to the Hp so as to prevent edge leakage. The upper and lower tubes are both 4.0
40
-------
Reproduced from
beat available copy.
©
Upper End Cap-
Upper Tube—
Containment Ring
Support Gravel
Lower Tube
Lover End Cap
Figure 15 - Cross section of Individual flow column and storage rack used to contain the flow
columns when not in use at the landfill sites
41
Flow
yVySoil
(Optional)
Geotextile
Test
Specimen
4 in.
4 in,
4 in. I"
-------
inch long sections of PVC pipe. They are contained by end caps which have pre-drllled 1.0 Inch
holes In them that are threaded. Support gravel of 1 to 1.5 Inch diameter. Is placed below the
geotextlle prior to positioning and gluing of the lower end cap. Similarly, If soil Is to be placed
above the geotextlle it must be done before the upper end cap Is fitted to the assembly. Cap
adaptors are then threaded into the end caps and fitted with 1.0 Inch diameter flexible tubing
(for constant head tests) or rigid clear tubing (for variable head tests). These two options are
shown In Figures 16 and 17, respectively, along with photographs of the completed devices.
The experimental testing program for this second phase of study was as follows:
1. Four different geotextlles were used at each of the four landfill sites and under each set
of test conditions; they are as follows:
(a) woven monofilament geotextile of 0.21 mm average opening size and 6% open area
fb) nonwoven heat bonded geotextlle of 0.21 to 0.15 mm average opening size
(c) lightweight nonwoven needle punched geotextile of 0.21 mm average opening size
(d) heavyweight nonwoven needle punched geotextlle of 0.15 mm average opening size
Complete details regarding these geotextlles were given previously in Table 3.
2. Soil (uniformly graded Ottawa sand of 0.42 mm average size, see Figure 2] was placed
above one set of the geotextlles, while nothing was placed above another set.
3. One set of the above mentioned columns were allowed to drain between readings (thus
providing aerobic conditions), while another set was constantly Immersed in
leachate (thus providing anaerobic conditions).
4. All of the above variations were done at each of the six landfill sites, thus 96 (4 x 2 x 2
x 6) flow columns of the type shown in Figure 15 are Included In this study.
5. Between landfill readings (which occurred at least on monthly intervals), the test
columns were stored at GRI as shown in the lower photograph of Figure 15.
Since all of the tests during the first year were performed on a monthly basis, and the
distinction between line particulate clogging versus biological clogging was never settled, a set
of continuous flow tests were performed. Here the flow columns were set up in a variable head
mode, as shown In Figure 17. and leachate was continuously supplied directly from a leachate
sump and passed through the system. The geotextlle/soil configuration was used so that flow
times were long enough to be accurately measured. The results of this testing at the two sites
with the harshest leachates. DE-3 and NJ-4, are shown in Figure 18. After an initial decrease
which was probably a tuning of the soll/geotextile system to the flow regime and the formation
of a stable flow network, the permeability of each leachate leveled oil to essentially constant
values. Thus, It was felt that any sediment within the leachate does not continue to build up so
42
-------
Inl»t H*»d Central
Ov«rfIow
(Optional) 0*ot*xtil»
t«s<
Sp«cim«n
OutM
H»jd
Control
Flow Column
Figure 16 - Flow column and hydraulic head control devices for constant head tests
-------
ha»t
0 v l0
hf p\f
i
Clear
Plastic
Standplpe
£$oii£
(Optional
m:W:
Geotextile
Test
Specimen
Flow Column
Outlet
mmm
-------
S3
<
Ul
r.
QC
0 6
0.5
£ 0 4
o
0.3
0 2
O.I
C.O
~ NJ-4 site
• DE-3 site
a.
TKq n
ag I
l flh-
o—
~
—•
»
100 200 300
VOLUME PASSED (Liters)
400
Figure 18 - Results of continuous leachate flow testing of soll/geotextlle/column at DE-3 and
NJ-4 sites based on variable head tests
45
-------
as to stop, or even substantially decrease, the system's flow. This suggests that the short term
filtration characteristics of both the soil and the geotextlle are adequate to handle the
indicated flow rates. It furthermore, provides a reference plane to which the long-term flow
rates can be compared. Such long-term flow tests are the focus of the not section.
Long term Intermittent flow rate evaluation of the columns using all six landfill
leachates were undertaken. Variable head tests of the sixteen variations at each site were
performed from which a "system permeability" could be calculated. The first test on each
column established the base line value called "original permeability" In units of "cm/sec".
From this point, flow tests were conducted on at least a monthly basis. The data to be reported
was an average of at least three Individual measurements per flow column.
Assuming that the flow rates would decrease as they did in Phase I testing, various
remediation schemes were undertaken after the Initial six months of flow rate testing. These
Included the following:
• leachate backflushlng
• water backflushlng
¦ nitrogen gas backflushlng
• vacuum extraction
The strategy was to take flow rate readings until near-equilibrium conditions were attained, or
until substantial clogging was evident, and then remediate the system by one of the above
techniques. The results are given In Tables 6 through 16. These tables give flow rates In the
form of system permeability (and percent reductions from the original value) for all 96 flow
columns at the following stages in this Phase n portion of the project.
Table 8 - Flow rates during the Initial six (6) months of evaluation
Table 9 - Flow rates after leachate backflush
Table 10 - Flow rates during the subsequent four (4) months of evaluation
Table 11 - Flow rates after water backflush
Table 12 - Flow rates during the subsequent flve (5) months of evaluation
Table 13 • Flow rates after nitrogen gas backflush
Table 14 - Flow rates during the subsequent three (3) months of evaluation
Table 15 - Flow rates after vacuum extraction
Table 16 - Flow rates during the subsequent two (2) months of evaluation
The data Included In these eight tables Is plotted In the form of 96 separate graphs and Is
included as Appendix "B". These curves generally take a similar form to one another in that
46
-------
Table 8 - Flow Rale Behavior and Pcrccnl Retained in Flow Rale Due lo Biological Clogging During Initial Six f6) Months of Evaluation
Geotextile
Type
Condition
& Cover
Orig. Perm,
(cm/sec)
PA-1
NY-2
DE-3
NJ-4
MD-5
PA-6
cm/sec
% Ret.
cm/sec '
ft Ret.
cm/sec
%ReL
cm/sec
%Ret.
cm/sec
% Ret
cm/sec
% Rei
WM (NC)
AN/S
0.64
0.10
16
0.14
22
0.12
19
0.10
16
0.23
36
0.18
28
WM (NC)
A/S
0.64
0.16
25
0.18
28
0.088
14
0.13
20
0.18
28
0.20
31
WM (NC)
AN/W
1.3
1.3
100
0.63
48
0.63
48
0.098
8
0.25
19
0.64
49
WM (NC)
A/W
1.3
0.63
48
1.3
100
0.25
19
0.018
1
0.42
32
0.13
10
NW (HB)
AN/S
0.64
0.12
19
0.15
23
0.11
17
0.082
13
0.17
23
0.16
25
NW (HB)
A/S
0.64
0.073
11
0.17
27
0.062
10
0.013
2
0.043
7
0.20
31
NW (HB)
AN/W
1.3
0.32
25
0.016
1
0.012
1
0.0053
0
0.036
3
0.0099
1
NW (HB)
A/W
1.3
0.0016
0
0.0028
0
0.0015
0
0.0021
0
0.012
1
0.0047
0
NW(N) 16
AN/S
0.64
0.16
25
0.15
23
0.13
20
0.065
10
0.20
31
0.23
36
NW(N) 16
A/S
0.64
0.18
28
0.18
28
0.12
19
0.13
20
0.21
33
0.21
33
NW (N) 16
AN/W
1J
0.84
65
U
100
0.32
25
0.21
16
0.42
32
0.42
32
NW(N) 16
A/W
1.3
0.84
65
1.3
100
0.045
3
0.25
19
0.64
49
0.11
8
NW (N) 8
AN/S
0.64
0.13
20
0.18
28
0.13
20
0.098
15
0.21
33
0.16
10
NW (N) 8
A/S
0.64
0.20
31
0.21
33
0.12
19
0.14
22
0.21
33
0.20
31
NW (N) 8
AN/W
1.3
0.84
65
1.3
100
0.42
32
0.64
49
0.64
49
0.64
49
NW (N) 8
A/W
1.3
0.84
65
1.3
100
0.066
5
0.075
6
0.64
49
0.64
49
Legend
WM = woven monofilament
NW =nonwoven
NC = non-calendered
HB = heat bonded
N = needled
AN = anaerobic
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
Summary.
• 6
• 4
• 38
• 34
• 14
96
columns (6%) have 100 to 76% flow retained
columns (47o) have 75 to 51% flow retained
columns (40%) have 50 to 26% flow retained
columns (35%) have 25 to 6% flow retained
columns fl 5%t have 5 to 0% flow retained
100%
-------
Table 9 - Flow Rale Behavior and Percent Retained in Flow Rales from Biological Clogging after First Treatment at Six (6) Months Duration
(Backflush was with Site Snccific Leachate't
Geotexlile
Type
WM(NQ
WM(NQ
WM(NC)
WM(NC)
NW(HB)
NW(HB)
NW(HB)
NW(HB)
NW(N) 16
NW (N) 16
NW(N) 16
NW(N) 16
NW (N) 8
NW (N) 8
NW (N) 8
NW (N) 8
Condition
& Cover
Orig. Perm.
PA-1
NY-2
DE-3
NJ-4
MD-5
PA-6
(cm/sec)
cm/scc
% Ret.
cm/sec
%Ret.
cm/sec
% Ret.
cm/sec
% ReL
cm/sec
% ReL
cm/sec
% ReL
AN/S
0.64
0.15
23
0.20
31
0.17
27
0.17
27
0.25
59
0.25
59
A/S
0.64
0.21
33
0.21
33
0.15
23
0.18
28
0.21
33
0.23
36
AN/W
1.3
1.3
100
1.3
100
1.3
100
0.42
33
0.64
49
1.3
100
A/W
1.3
1.3
100
1.3
100
1.3
100
0.64
49
0.64
49
1.3
100
AN/S
0.64
0.13
20
0.23
36
0.18
28
0.13
20
Oil
33
0.21
33
A/S
0.64
0.11
17
0.21
33
0.13
20
0.032
5
0.085
23
0.25
16
AN/W
1.3
1.3
100
0.064
2
0.045
2
0.42
32
0.064
4
0.040
3
A/W
1.3
0.004
1
0.0039
1
0.0059
1
0.0092
1
0.030
2
0.051
4
AN/S
0.64
0.18
28
0.21
33
0.15
23
0.15
23
0.20
31
0.28
44
A/S
0.64
0.21
33
0.20
31
0.16
25
0.18
28
0.23
36
0.23
36
AN/W
1.3
1.3
100
1.3
100
0.64
49
1.3
100
0.64
49
0.64
49
A/W
1.3
1.3
100
1.3
100
0.32
25
0.64
49
0.64
49
1.3
100
AN/S
0.64
0.17
27
0.25
39
0.16
25
0.14
22
0.13
20
0.21
33
A/S
0.64
0.21
32
0.23
36
0.17
27
0.16
25
0.12
19
0.25
39
AN/W
13
1.3
100
1.3
100
1.3
100
1.3
100
0.64
49
1.3
100
A/W
1.3
1.3
100
1.3
100
0.21
16
0.11
8
0.64
49
1.3
100
Legend
Summary
WM = woven monofilament
NW = nonwoven
NC = non
-------
Tabic 10 - Flow Rate Behavior and Percent Retained in Row Rate from Biological Clogging Due to Four Months of Evaluation
Following First Treatment (Ten Months Total Exposure)
Geotextile
Type
Condition
& Cover
Orig. Perm.
PA-I
1
NY-2
DE-3
NJ-4
MD-5
PA-6
(cm/sec)
cm/sec
% Ret.
cm/scc
% Ret.
cm/sec
% Ret.
cm/sec
% ReL
cm/sec
% Ret.
cm/sec % ReL
WM (NC)
AN/S
0.64
0.15
23
0.088
14
0.029
5
0.067
10
0.15
23
0.14
22
WM (NC)
A/S
0.64
0.17
27
0.12
19
0.038
6
0.12
19
0.031
5
0.13
20
WM (NC)
AN/W
1.3
0.64
49
0.42
32
0.36
28
0.64
49
0.079
6
0.64
49
WM (NC)
A/W
1.3
0.64
49
0.64
49
0.0043
0
0.034
3
0.25
19
0.42
32
NW (HB)
AN/S
0.64
0.17
27
0.077
12
0.065
10
0.082
13
0.14
22
0.12
19
NW (HB)
A/S
0.64
0.18
28
0.064
10
0.060
9
0.11
17
0.0049
1
0.11
17
NW(HB)
AN/W
1.3
0.64
49
0.067
5
0.0059
0
0.32
25
0.0052
0
0.0091
1
NW (HB)
A/W
1.3
0.002
0
. 0.002
0
0.0044
0
0.013
1
0.0072
1
0.0037
1
NW(N) 16
AN/S
0.64
0.13
20
0.094
15
0.059
9
0.13
20
0.13
20
0.13
20
NW (N) 16
A/S
0.64
0.17
27
0.11
17
0.069
11
0.094
15
0.12
19
0.13
20
NW(N) 16
AN/W
1.3
0.64
49
0.42
32
0.0097
1
0.64
49
036
28
0.32
25
NW (N) 16
A/W
1.3
0.32
25
0.098
8
0.0029
0
0.0059
0
0.0065
1
0.42
32
NW (N) 8
AN/S
0.64
0.12
19
0.12
19
0.069
11
0.026
4
0.11
17
0.12
19
NW (N) 8
A/S
0.64
0.32
50
0.11
17
0.079
12
0.067
10
0.14
22
0.12
19
NW (N) 8
AN/W
1.3
0.84
65
0.32
25
0.014
1
0.32
25
0.42
32
0.42
32
NW (N) 8
A/W
1.3
0.64
49
0.42
32
0.010
1
0.005
0
0.0065
0
0.18
14
Legend SuTPWY
columns (0%) have 100 to 76% flow retained
columns (2%) have 75 to 51% flow retained
columns (28%) have 50 to 26% flow retained
columns (48%) have 25 to 6% flow retained
columns <22%) have 5 to 0% flow retained
100%
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
WM = woven monofilament • 0
NW = nonwoven • 2
NC = non
-------
Tabic 11 - Flow Rale Behavior and Percent Retained in Flow Rate from Biological Clogging after Second Treatment at Ten (10) Months Duration
(Backflush was with Tap Water)
Geotextile Condition Orig. Perm. PA-1 NY-2 DE-3 NJ-4 MD-5 PA-6
Type
& Cover
(cm/sec)
cm/sec
% Ret.
cm/sec
% Ret.
cm/sec
% ReL
cm/scc
%ReL
cm/sec
% ReL
cm/sec
% ReL
WM (NC)
AN/S
0.64
0.36
56
0.36
56
0.18
28
0.20
31
0.25
39
0.28
44
WM (NC)
A/S
0.64
0.42
66
0.36
56
0.21
33
0.23
36
0.10
16
0.36
56
WM (NC)
AN/W
1.3
1.3
100
1.3
100
1.3
100
1.3
100
0.64
49
1.3
100
WM (NC)
• A/W
-1.3
1.3
100
13
100
0.51
39
0.64
49
1.3
100
1.3
100
NW (HB)
AN/S
0.64
0.32
50
0.28
44
0.15
23
0.21
33
0.17
27
0.28
44
NW (HB)
A/S
0.64
0.36
56
0.21
33
0.12
19
0.23
36
0.0075
1
0.32
50
NW (HB)
AN/W
1.3
1.3
100
0.64
49
0.85
65
0.85
65
0.079
6
1.3
100
NW (HB)
A/W
1.3
1.3
100
0.11
8
0.0003
0
0.18
14
0.32
25
0.42
66
NW (N) 16
AN/S
0.64
0.32
50
0.32
50
0.21
33
0.25
39
0.20
31
0.32
50
NW(N) 16
A/S
0.64
0.25
39
0.25
39
0.17
27
0.21
33
0.51
80
0.28
44
NW (N) 16
AN/W
1.3
1.3
100
1.3
100
0.64
49
0.85
65
0.85
65
0.85
65
NW(N) 16
A/W
1.3
1.3
100
1.3
100
0.36
28
0.047
7
0.079
12
0.85
65
NW (N) 8
AN/S
0.64
0.25
39
0.28
44
0.21
33
0.085
13
0.18
28
0.32
50
NW (N) 8
A/S
0.64
0.36
56
0.32
50
0.13
20
0.085
13
0.11
17
0.25
78
NW (N) 8
AN/W
1.3
1.3
100
1.3
100
1.3
100
1.3
100
1.3
100
1.3
100
NW (N) 8
A/W
1.3
1.3
100
0.84
65
0.32
25
0.21
16
0.64
49
0.85
65
Legend
Summary
WM = woven monofilament
NW = nonwoven
NC =non-calendered
HB = heat bonded
N = needled
AN = anaerobic
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
25 columns (26%) have 100 to 76% flow retained
23 columns (24%) have 75 to 51% flow retained
33 columns (34%) have 50 to 26% flow retained
13 columns (14%) have 25 to 6% flow retained
_2 columns ( 2%1 have 5 to 0% flow retained
96 100%
-------
Table 12 - Flow Rate Behavior and Percent Retained in Flow Rate from Biological Clogging Due to Five (51 Months of Evaluation Following Second
Treatment (15 Months Total)
Geoiextile
Type
Condition
& Cover
Orig. Perm.
PA-1
NY-2
DEO
NJ-4
MD-5
PA-6
(cm/sec)
cm/scc
% Ret.
cm/scc
% Ret.
cm/sec
% Ret
cm/sec
% Ret
cm/sec
% Ret
cm/sec ft
o Ret
WM (NQ
AN/S
0.64
.14
22
.12
19
.095
15
.12
19
.050
8
.10
16
WM (NC)
A/S
0.64
.09
14
.16
25
.061
10
.14
22
.080
13
.11
17
WM (NQ
AN/W
1.3
.43
33
.87
67
.077
6
.87
67
.22
17
.44
34
WM (NQ
A/W
1.3
.66
51
.44
34
.001
0
.001
0
.069
5
.012
1
NW (HB)
AN/S
0.64
.11
17
.11
17
.042
7
.061
10
.016
3
.078
12
NW (HB)
A/S
0.64
.11
17
.08
13
.037
6
.075
12
.001
0
.11
17
NW (HB)
AN/W
1.3
.069
5
.001
0
.001
0
.001
0
.001
0
.008
1
NW (HB)
A/W
1.3
.001
0
.001
0
.001
0
.001
0
.001
0
.002
0
NW(N) 16
AN/S
0.64
.13
20
.05
8
.052
8
.091
14
.028
4
.095
15
NW(N) 16
A/S
0.64
.14
22
.06
9
.038
6
.11
17
.091
14
.13
20
NW (N) 16
AN/W
1.3
.001
0
.001
0
.001
0
.001
0
.001
0
.014
1
NW (N) 16
A/W
1.3
.001
0
.001
0
.001
0
.001
0
.001
0
.003
0
NW (N) 8
AN/S
0.64
.15
23
.095
15
.073
11
.085
13
.057
9
.08
13
NW (N) 8
A/S
0.64
.18
28
.091
14
.066
10
.098
15
.11
17
.14
23
NW (N) 8
AN/W
1.3
.43
33
.13
10
.001
0
.44
34
.001
0
.01
1
NW (N) 8
A/W
1.3
.015
1
.001
0
.001
0
.001
0
.001
0
.011
1
Legend
Summary
WM = woven monofilament
NW = nonwoven
NC = non-calendered
HB = heat bonded
N = needled
AN = anaerobic
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
0 columns (0%) have 100 to 76% flow retained
3 columns (3%) have 75 to 51% flow retained
7 columns (7%) have 50 to 26% flow retained
48 columns (50%) have 25 to 6% flow retained
24 columns (40%) have 5 to 0% flow retained
96 100%
-------
Table 13 - Flow Rale Behavior and Percent Retained in Flow Rale from Biological Gogging After Third Treatment at Fifteen (15) Months Duration
(Nitrogen Gas Backflush^
Geotextile
Type
Condition
& Cover
Orig. Perm.
PA-1
NY-2
DE-3
NJ-4
MD-5
PA-6
(cm/sec)
cm/sec
% Ret.
cm/sec
% Ret.
cm/sec
%Ret
cm/sec ft
> Ret
cm/sec
%Ret
cm/sec
% Ret
WM (NC)
AN/S
.64
.32
50
.23
36
.23
36
.21
33
.20
31
.26
16
WM (NC)
A/S
.64
.21
33
.26
41
.21
33
.20
31
.20
31
.23
14
WM (NC)
AN/W
1.3
1.3
100
1.3
100
1.3
100
.87
67
.66
51
.87
67
WM (NC)
A/W
1.3
1.3
100
.66
51
.087
7
.08
6
.13
10
.33
25
NW (HB)
AN/S
.64
.28
44
.23
36
.18
28
.20
31
.18
28
.18
28
NW (HB)
A/S
.64
.20
31
.21
33
.13
20
.16
25
.087
14
.23
36
NW (HB)
AN/W
1.3
.87
67
.001
0
.087
67
.07
5
.001
0
.001
0
NW (HB)
A/W
1.3
.004
0
.001
0
.001
0
.001
0
.001
0
.001
0
NW (N) 16
AN/S
.64
.21
33
.26
41
.20
31
.21
33
.23
36
.23
36
NW(N) 16
A/S
.64
.21
33
.23
35
.18
28
.20
31
.21
33
25
39
NW(N) 16
AN/W
1.3
1.31
100
.87
67
.87
6
.87
67
.001
0
.001
0
NW(N) 16
A/W
1.3
.08
6
.87
67
.066
5
.05
4
.001
0
Oil
0
NW (N) 8
AN/S
.64
.21
33
.23
36
.20
31
.20
31
.21
33
.23
36
NW (N) 8
A/S
.64
23
36
.23
36
.18
28
.17
27
.21
33
.21
33
NW (N) 8
AN/W
1.3
.87
67
.66
51
.87
67
.66
51
.001
100
.04
3
NW (N) 8
A/W
1.3
.66
51
.001
0
.001
0
.03
3
.001
100
.03
3
L&snd
Summary
WM = woven monofilament
NW = nonwoven
NC = non-calendered
HB = heat bonded
N = needled
AN = anaerobic
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
7 columns (7%) havelOO to 76% flow retained
16 columns (17%) have 75 to 51% flow retained
44 columns (46%) have 50 to 26% flow retained
10 columns (10%) have 25 to 6% flow retained
12 columns (20%) have 5 to 0% flow retained
96 100%
-------
Tablel4 - Flow Rale Behavior and Percent Retained in Flow Rale from Biological Clogging Due lo Three (3) Months of Evaluation Following
Nitrogen Gas Backflush (18 Months Total)
Gcotextile
Type
Condition
A Cover
Orig. Perm.
PA-
1
NY-2
DE-3
NJ-4
MD-5
PA-6
(cm/sec)
cm/sec
% Rel.
cm/sec
% Ret.
cm/sec
% ReL
cm/sec
% ReL
cm/sec
% ReL
cm/sec
% ReL
WM (NQ
AN/S
0.64
0.11
17
0.13
20
0.075
12
0.16
25
0.015
2
0.073
11
WM(NQ
A/S
0.64
0.09
14
0.15
23
0.061
10
0.069
11
0.023
4
0.083
13
WM (NQ
AN/W
1.3
0.63
48
0.63
48
0.18
14
0.63
48
0.032
2
0.42
32
WM (NQ
A/W
1.3
0.42
32
0.31
24
0.001
0
0.001
0
0.001
0
0.037
3
NW(HB)
AN/S
0.64
0.10
16
0.07
11
0.051
8
0.060
9
0.014
2
0.064
10
NW(HB)
A/S
0.64
0.09
14
0.12
19
0.001
0
0.050
8
0.001
0
0.069
11
NW(HB)
AN/W
13
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW(HB)
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW(N) 16
AN/S
0.64
0.10
16
0.06
9
0.095
15
0.082
13
0.013
2
0.080
13
NW(N) 16
A/S
0.64
0.11
17
0.13
20
0.055
9
0.075
12
0.001
0
0.057
9
NW(N) 16
AN/W
1.3
0.42
32
0.001
0
0.016
1
0.63
48
0.001
0
0.001
0
NW(N) 16
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW(N)8
AN/S
0.64
0.09
14
0.09
14
0.12
19
0.10
16
0.032
5
0.086
13
NW (N) 8
A/S
0.64
0.12
19
0.14
22
0.044
7
0.088
14
0.023
4
0.071
11
NW (N) 8
AN/W
1.3
1.26
97
0.001
0
0.001
0
0.63
48
0.001
0
0.025
2
NW (N) 8
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
Legend
Swnmary
WM = woven monofilament
• i
columns (1%) have 100 to 76% flow retained
NW = nonwoven
• l
columns (1%) have75 to 51% flow retained
NC = non-calendered
• 9
columns (9%) have 40 to 26% flow retained
HB = heat bonded
• 39
columns (41 %) have 25 to 6% flow retained
N = needled
• 4fi
columns (48%) have 5 to 0% flow retained
AN = anaerobic
96
100%
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
-------
Tabic 15 - Flow Rate Behavior and Percent Retained in Flow Rale from Biological Clogging After Fourth Treatment at Eighteen (18)
Months Duration
Vacuum Extraction
Geotextile
Type
Condition
& Cover
Orig. Perm.
PA-1
NY-2
DE-3
NJ-4
MD-5
PA-6
(cm/sec)
cm/scc
% Ret.
cm/sec
% Ret.
cm/sec
% ReL
cm/sec
% ReL
cm/sec
% Ret
cm/sec % Ret
WM (NC)
AN/S
0.64
0.21
33
0.16
25
0.16
25
0.16
25
0.064
10
0.095
15
WM (NC)
A/S
0.64
0.001
0
0.13
20
0.086
13
0.11
17
0.050
8
0.14
22
WM (NC)
AN/W
1.3
0.63
48
0.84
65
0.84
65
0.84
65
0.31
24
0.42
32
WM (NC)
A/W
1.3
0.21
16
0.31
24
0.001
0
0.032
2
0.090
7
0.25
19
NW (HB)
AN/S
0.64
0.15
23
0.12
19
0.12
19
0.14
22
0.037
6
0.071
11
NW (HB)
A/S
0.64
0.001
0
0.14
22
0.042
7
0.057
9
0.001
0
0.12
19
NW (HB)
AN/W
1.3
0.04
3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW (HB)
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW (N) 16
AN/S
0.64
0.13
20
0.16
25
0.13
20
0.17
26
0.001
0
0.036
6
NW(N) 16
A/S
0.64
0.11
17
0.12
19
0.064
10
0.12
19
0.045
7
0.048
8
NW(N) 16
AN/W
1.3
0.63
48
0.001
0
0.36
28
0.84
65
0.001
0
0.001
0
NW(N) 16
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW (N) 8
AN/S
0.64
0.15
23
0.15
23
0.18
28
0.14
22
0.035
5
0.061
10
NW (N) 8
A/S
0.64
0.12
19
0.14
22
0.071
11
0.078
12
0.069
11
0.073
11
NW (N) 8
AN/W
1.3
0.63
48
0.001
0
0.001
0
0.84
65
0.001
0
0.066
5
NW (N) 8
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
Legend Summary
columns (0%) have 100 to 76% flow retained
columns (5%) have 75 to 51% flow retained
columns (13%) have 50 to 26% flow retained
columns (45%) have 25 to 6% flow retained
columns (37%^ have 5 to 0% flow retained
100%
A = aerobic
S = sand over geotextile
W = without sand, i.e. geotextile alone
WM = woven monofilament • 0
NW =nonwoven • 5
NC = non-calendered • 12
HB = heat bonded • 43
N - needled • 36
AN = anaerobic 96
-------
Tabic 16 - Flow Rate Behavior and Percent Retained in Flow Rate from Biological Clogging Due to Two(21 Months of Evaluation Following Fourth
Treatment (20 Months Total)
Geotextile
Type
Condition
A Cover
Orig. Perm.
PA-1
NY-2
DE-3
NJ-4
MD-5
PA-6
(cm/scc)
cm/scc
% Rcl.
cm/scc
% Ret.
cm/scc
% ReL
cm/sec
% ReL
cm/sec
% ReL
cm/sec
% ReL
WM (NC)
AN/S
0.64
0.14
22
0.12
19
0.091
14
0.11
17
0.005
1
0.082
13
WM (NC)
A/S
0.64
0.067
10
0.13
20
0.046
7
0.058
9
0.012
2
0.075
12
WM (NC)
AN/W
1.3
0.33
25
0.33
25
0.43
33
0.33
25
0.093
7
0.008
1
WM (NC)
A/W
1.3
0.059
5
0.19
15
0.001
0
0.001
0
0.001
0
0.068
5
NW (HB)
AN/S
0.64
0.12
19
0.066
10
0.053
8
0.048
8
0.005
1
0.054
8
NW (HB)
A/S
0.64
0.10
16
0.054
8
0.005
1
0.005
1
0.005
1
0.078
12
NW (HB)
AN/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW (HB)
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
NW (N) 16
AN/S
0.64
0.13
20
0.080
13
0.058
9
0.069
1
0.005
1
0.005
1
NW(N) 16
A/S
0.64
0.12
19
0.083
13
0.013
2
0.046
7
0.005
1
0.005
1
NW(N) 16
AN/W
1.3
0.11
8
0.001
0
0.001
0
0.33
25
0.001
0
0.001
0
NW (N) 16
A/W
1.3
0.001
0
0.05
4
0.001
0
0.001
0
0.001
0
0.001
0
NW (N) 8
AN/S
0.64
0.15
23
0.071
11
0.11
17
0.066
10
0.013
2
0.045
7
NW (N) 8
A/S
0.64
0.11
17
0.098
15
0.035
5
0.075
12
0.019
3
0.040
6
NW (N) 8
AN/W
1.3
0.43
33
0.11
8
0.001
0
0.076
6
0.001
0
0.001
0
NW (N) 8
A/W
1.3
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
0.001
0
Legend
WM = woven monofilament
NW = nonwoven
NC = non-calendered
HB = heat bonded
N = needled
AN = anaerobic
A = aerobic
S = sand over geotextile
W = without sand. i.e. geotextile alone
Summary
• 0 columns (0%) have 100 to 76% flow retained
• 0 columns (0%) have 75 to 51 % flow retained
• 1 columns (1 %) have 50 to 26% flow retained
• 44 columns (46%) have 25 to 6% flow retained
• 51 columns (53%1 have 5 to 0% flow retained
96 100%
-------
flow rates decrease until a remediation Is attempted. This remediation increases the flow rate
(to varying degrees), but subsequent testing over time causes the flow rate to decrease tending
toward the original, and uninterrupted behavior.
Same comments as to the remediation attempts are In order before discussing the trends
appearing in Tables 6 through 16 and the corresponding graphs of Appendix "B".
Regarding leachate baekflushlng: our thoughts were that additional liquid would not be
added to the total quantity of leachate generated at the site for an owner/operator to handle
and subsequently treat. Baekflushlng with leachate was accomplished by reversing the flow in
a constant head setup, recall Figure 16. The downstream gradient reservoir Inlets leachate at
the bottom of the flow column and outlets the leachate Into the upstream reservoir. A pump
with a controller is required to maintain a constant head In the downstream gradient
reservoir and a drain connects the upstream reservoir to the sump.
The bacldlushlng was performed at a constant head of three feet Due to the reverse mode
of flow, a geotextile and porous stone retainer was placed above the flow column to prevent the
sand from liquefying and flushing into the outlet reservoir. It is interesting to note that this
geotextile porous stone trap needed to be washed out or replaced after each baekflushlng. as It
always collected sediment and bloslime after each Ave minutes of baekflushlng.
Regarding baekflushlng with water: this technique was also accomplished by reversing
the flow on the test columns. The technique was performed In the laboratory for all ninety six
columns. The base of the flow column was attached to an inlet hose. The columns containing
sand were backflushed at 10 lb/sq. In. using a 100 gal/hr flow rate for a duration of one minute.
The columns containing geotextlles alone were backflushed at 2 lb/sq. In. using a 100 gal/hr
flow rate for a duration of one minute. Different pressures were utilized to ensure that^
excessive pressure would not dislodge those columns with the geotextile alone. Due to the
reverse mode of flow, a geotextile and porous stone retainer were placed above the flow column
to prevent the sand from liquefying and flushing into the outlet reservoir. Instead of an in-line
restraint, however, the geotextile porous stone trap was hand held above the column during the
baekflushlng process.
Regarding baekflushlng with nitrogen gas: the thought was not to add any liquid to the
system. Nitrogen was used so as not to destroy anaerobic conditions In those test columns
which were constantly saturated. Baekflushlng with nitrogen was accomplished by reversing
the flow in the columns. The technique was performed in the laboratory for all ninety six
columns. The test column was attached to an Inlet hose. The columns were first saturated with
leachate for 24 hours. The columns were then hooked up to the nitrogen tank and pressurized
56
-------
in a reverse mode. All of the columns were backflushed at 30 lb/ln2 using a 100 gal/hr flow
rate for a duration of one minute. Backflushlng with a gas produced a very different response
from that of backflushing with a liquid. In this case, no geotextlle nor porous stone retainer
was needed because only bubbles and leachate emerged from the top of the columns. Only
minor amounts of solids were transported In the froth which was emitted from the top of each
column.
Regarding vacuum extraction: our thoughts were that we could relieve the clogging by
sucking the blosllme and sediment down-gradient instead of trying to force it up-gradient as in
the other three remediation attempts. This method, like backflushing with nitrogen, would
not generate any additional liquid and might be relatively easy to Implement In the field.
Vacuum extraction was performed In the laboratory for all ninety six columns. The
permeameter base was attached to an Inlet hose. The columns were first saturated with
leachate for 240hours. The columns were then attached to the vacuum system and 500 ml of
leachate was drawn through each column. The vacuum was maintained at 10 Inches of
mercury during this time. Due to the different degrees of clogging some columns relinquished
this quantity of fluid quickly while others needed considerable time.
As mentioned previously. Tables 9, 11. 13 and 15 are the results of the leachate
backflush, water backflush, nitrogen backflush and vacuum extraction, respectively. Tables 8,
10. 12, 14 and 16 represent the flow rate behavior preceding and following each of these
remediation schemes.
57
-------
Summary of Phase Two Stndv
The flow rate trends observed In Phase I were again noticed In this Phase n study. We fed
that the Phase n data, however, is much more authoritative due to the greatly improved test
devices. Appendix *C" gives details of the ASTM Test Method which has been modeled and
developed on the basis of this testing program. It win be available as ASTM D1987-91, as of
May 1, 1991. Also It was noted that both the sand/geotextlle combined systems and the
geotcxtile by itself are candidates for clogging. Regarding the first six months of flow testing,
te., before the first remediation. the following comments apply.
• The columns with sand above the geotextlles clogged considerably more than those
with the geotextlle alone: te.. 23% flow was retained for sand/geotextlles vs. 34% flow
retained for geotextlles alone. Note that. If the heat-bonded nonwoven fabrics are
eliminated from the geotextlle group, the flow rate retained by the geotextlle group Is
45%, suggesting that geotextlles can certainly clog less than natural soil filters.
• Of the four geotextlles evaluated, the highest retained flow was with the lightweight
needled nonwoven (38.0%). with the heavyweight needled nonwoven (34.2%) and
woven monofilament (31.9%) slightly behind. The nonwoven heat-bonded fabric had
the lowest retained flow of only 10.0% after 6 months of evaluation.
• Of the various landfill leachates, the lowest retained flow rate was using the NJ-4
(14%) and DE-3 (17%) leachates. Recall from Table 4 that these are the leachates with
the highest TS and BOD 5 concentrations. The other four landfill leachates and their
percentages of flow retained after six months of testing were PA-6 (26%). MD-5 (29%).
PA-1 (38%) and NY-2 (41%).
In order to assess the overall performance of the remediation attempts, arid their
relative performance in contrast to one another, the data of Tables 9, 11. 13 and 15 were
analyzed with respect to their percent of flow rate improvement. These values were actually
scaled directly from the 96 curves of Appendix "B". The results for percent recovery, or
removal efficiency, are given In Table 17. The data Indicates the following trends:
• Backflushlng of geotextlles by themselves is more efficient than backflushlng of
geotextlle/sand systems. The average recovery efficiencies are 29% and 13%,
respectively.
• With sand overlying a geotextlle there is no measurable difference from one type of
geotextlle to another.
• With the geotextlle acting alone, remediation Is most effective with the woven
monofilament geotextlles (38% recovery efficiency), slightly less effective with the
58
-------
Table 17 - Flow Rate Recovery with Respect to Various Remediation Attempts
(a) Flow Columns with Sand Overlying Geotextile
Geotextile Condition Recovery Efficiency (%) Averages
Type Leachate Water Nitrogen Vacuum
woven.
monofilament
nonwoven,
heat-bonded
nonwoven,
needled-llght
nonwoven.
needled-heavy
anaerobic
aerobic
anaerobic
aerobic
anaerobic
aerobic
anaerobic
aerobic
15
7
8
9
11
6
6
5
26
27
20
18
20
19
25
25
17
14
21
16
19
14
24
19
8
7
7
6
6
2
8
3
17 } 15
14
14 } 13
12
14 } 12
11
!6} 14
13
.13%
Average
23
18
(b) Flow Columns with Geotextile Alone
Geotextile Condition Recovery Efficiency (%) Averages
Type Leachate Water Nitrogen Vacuum
woven.
monofilament
anaerobic
aerobic
45
58
60
56
45
20
18
7
42 } 38
35
nonwoven,
heat-bonded
nonwoven,
needled-llght
anaerobic
aerobic
anaerobic
aerobic
19
2
44
20
51
35
74
38
23
0
45
19
1
0
12
0
23 } 16
9
44 } 31
19
~29%
nonwoven,
needled-heavy
anaerobic
aerobic
35
35
44
42
51
29
10
0
35 } 30
26
Average
32
50
29
59
-------
nonwoven needled lightweight (31%) and heavyweight (30%) geotextlles. and relatively
ineffective with the nonwoven heat bonded geotextUes (16%).
For the cases where sand Is placed over the geotextlie, there Is no difference between
anaerobic and aerobic remediation schemes.
For the geotextlie acting by itself, remediation was slightly better under anaerobic
conditions than with aerobic conditions.
For the cases where sand is placed over the geotextlie. the remediation recovery
efficiency rankings were:
water > nitrogen > leach ate > vacuum
For the cases where the geotextlie is acting alone, the remediation recovery efficiency
rankings were:
water > leachate > nitrogen > vacuum
60
-------
CONCLUSIONS
Recognition of past research concerning biological dogging of landfill drainage systems
has led to a simulated field oriented project focused on geotextlle filter clogging using a number
of domestic landfill leachates. The filter was singled out (versus the geonet drain, drainage
stone or perforated pipe) since it has the smallest openings and Is likely to become clogged
before other components. Geotextiles were emphasized because they are relatively new
materials for this particular application.
Phase I of the study, which lasted for 12 months, caused a reorientation of our Initial
goals since the granular soils covering the filters were clogging before the geotextiles.
Furthermore, sediments, and/or particulates, were a major factor in the flow reductions which
appeared to be synergistic with the biological clogging. Clearly, partial filter clogging was
occurring with a gradual reduction of flow rate over time. These trends were common to all six
(6) landfills that were under observation. All of the landfills were domestic (Subtitle "D")
facilities; but were very different in their waste stream, volume of waste deposited and liquid
management schemes. It was recognized early in this Phase I activity that remediation
attempts would be a necessary part of the overall study, but the experimental setup could not
accommodate such activities. New, and different, test devices would be necessary If such
attempts were to be made. What was concluded, however, from Phase I activities were the
following:
• Filter clogging (as Indicated by flow rate reductions) over the 12-month test period
varied widely. The range was between 10% and 100% (I.e., to the limit of our
capability). .
• A geotextlle filter must be relatively open In its pore structure If it Is to limit the'
amount of clogging, I.e., the geotextlle must be capable of passing the sediment, or
particulates, along with the associated micro-organisms Into the down-gradient
drainage system.
• The polymer type (polypropylene, polyester or polyethylene) comprising the geotextlle -
fibers appears to be a non-issue.
• Both anaerobic and aerobic conditions promote clogging, the relative amounts,
however, were not capable of being Identified because of differing test setups.
• The strength of the geotextlles was not adversely effected by the 12-month exposure to
the various leachates. This finding, coupled with numerous micrographs which
showed no chemical attachment of bacteria to the fibers, leads us to conclude that
biological degradation of polymeric based geotextdes does not occur.
61
-------
Phase II of the study, which lasted for 24 months, saw the development of a new. and
vastly improved, test device for flow rate evaluation. The four Inch diameter flow columns
which were developed during this project have the following capabilities:
• All types of cross sections can be evaluated; geotextlles by themselves, soll/geotextlle
systems, soll/geotextlle/geonet systems, or soll/geotextlle /gravel systems.
• Anaerobic, or aerobic, conditions can be maintained.
• Flow rates can be evaluated using a falling head or a constant head measurement
approach.
• The devices are relatively small and quite portable. Therefore, they can be stored
indoors and taken to a site for evaluation, or stored at the site, or even within the
leachate storage tank or sump.
• Various types of remediation of clogged systems can be evaluated.
• The test devices and their measurement protocol have recently been adopted as an
ASTM Test Method, see Appendix "C". The test method designation Is D1987-91 and
will be available May 1. 1991.
• The test devices, and their contents, can be epoxy-set and cut in half to visually observe
the conditions existing within the cross section.
• Since all parts of the device consist of PVC plumbing and swimming pool accessories,
they are readily available, easily sealed by chemical wipes, and low in cost. Current
cost for all components necessary to build one flow column Is approximately $30.
Ninety-six (96) of the above described test columns were constructed and used for the
duration of this Phase II study. There were four geotextlles. with and without soli above them,
anaerobic and aerobic conditions, and all were used at six landfllls (4 x 2 x 2x 6 = 96). They
were evaluated for an Initial six months: from which flow reductions were seen to replicate the
results of the Phase I study. Thus, the first remediation, a leachate backfiush. was attempted.
It resulted in an improved flow rate but to varying amounts between the 96 different columns.
After four months of continued flow testing the flow rates decreased allowing for a second
remediation. This remediation used a water backflush. Again flow rates were Increased but
over the next five months they again decreased. The third remediation was a nitrogen gas
backflush. It improved flow rates, but three months later they were once again reduced. The
fourth, and last, remediation was vacuum extraction which only nominally improved flow
rates when it was performed. Thereafter, the flow rate again decreased. The overall average
behavior or the 96 columns is shown in Figure 19. It visually describes the decreasing flow rate
trends between remedlatlons and the rapid increase in flow rates Immediately following
62
-------
J
FLOW RATE
(* RETAINED)
TIME(MONTHS)
Figure 19 - Average response of nlnety-slx Dow rate colmns from Phase II Activities
63
f
-------
remediation. The individual curves for each of the 96 test columns are given In Appendix "B".
The conclusions reached from this Phase II study are as follows:
• Flow rate reductions were similar to the Phase I results and the conclusions drawn
earlier have been substantiated.
• If geotextile and/or soil filters are to be used in leachate collection systems they must
have sufficiently open voids to pass the sediment, or particulates, along with the
micro-organisms contained In the leachate into the downstream drainage system.
• The limiting, or equilibrium, flow rate retained must be compared to the site specific
design requirement to see If It Is adequate, or not. If flow rates over time are not
adequate, remediation Is necessary. It was found that the water backflush technique
gave the best results [35% Improvement), nitrogen gas backflush (23%) and leachate
backflush (17%) methods were next, and the vacuum extraction gave only nominal
Improvement (2%), I.e.. it was the least effective.
• The periodicity of backflushing to open up a clogged, or semi-clogged, filter system
appears to be approximately six (6) months.
Early in the overall study it was suggested that the Incorporation of blocides Into the
geotextile (or geonet) polymer structure might be effective In keeping the flow system open. The
concept was to add various amounts of a time-released biocide Into the polymer compound as
the product Is manufactured, which would essentially diffuse to the surface of the fibers during
its service life. Upon contact, it would subsequently kill the viable micro-organisms In the
leachate. In the tests that were conducted on 16 separately built flow columns there was some
experimental evidence that 2% and 4% bloclde was partially effective. However, the remains of
the dead bacteria must be permitted to pass through the system. This apparently could not
happen for our particular tests setups. Thus, the Idea of a very open filter system was further
reinforced. This bloclde study Is presented In Its entirety as Appendix "A".
64
-------
RECOMMENDATIONS
As far as recommendations are concerned; It Is very clear to us that landfill filters are
not, and cannot, be designed Identically as soil filters in geotechnlcal applications. Leachate
is a turbid, micro-organism laden liquid which behaves very differently than water.
Recognizing this feature leads us to our recommendations concerning landfill
drainage/filtration systems.
• The focus of attention should be placed on the filter with respect to long-term flow rate
capability. Note that the drainage component (gravel, geonet or pipe) can then be
designed based on the long-term flow rate capability of the filter.
• The filter, either geotextile or natural soil, must be sufficiently open so as to pass the
majority of the sediment and micro-organisms contained in the leachate Into the
downstream drain In a steady-state (I.e., equilibrium) manner.
• The required quantity of leachate flowing through the filter Is a site-specific design
consideration which has not been considered In this project.
• The drain beneath the filter must be capable of accepting this flow rate (along with the
associated sediment and micro-organisms) and of transmitting It to the downgradlent
sump for collection, removal and proper treatment.
These comments underscore the Importance of the design-by-function concept of
engineering design. For a landfill filter, this Involves comparing an allowable flow rate with a
required flow rate for a design value of factor-of-safety. This project gave insight as to
allowable flow rates for a variety of possible geotextile and natural soil filter conditions. The
required flow rate must come from a site-specific design. In this regard additional research
should be considered.
An additional project, with a focus on design considerations, is recommended. Clearly,
the HELP model'4' would be involved In such an effort, but other water balance methods might
also be considered. In fact, the entire liquids management strategy of landfllllng should
probably be investigated In light of current practice, e.g.. current trends toward leachate
recirculation practices. In such a proposed effort, field exhuming of abandoned landfills, or
exhuming sltes-of-oportunlty which have open leachate collection systems, should be
carefully examined for their behavior and performance. By so doing, feed-back Into either the
allowable flow rates or the required flow rates can be re-evaluated and appropriately modified.
65
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REFERENCES
1. Chlan, E. S. K. and DeWalle. F. B., "Evaluation of Leachate Treatment." Vol. I and II. EPA-
600/2-77-186 (a) and (b), U.S. EPA, ClnclnnaU. OH. 1977.
2. EPA, "Subtitle D Study - Phase I Report," U.S. EPA, Office of Solid Waste. Washington, DC,
EPA/530-SW-86-054. 1986.
3. Haxo, H. E.. Jr., "Compatibility of Flexible Membrane Liners and Municipal Solid Waste
Leachates," Contract No. 68-03-3413. Risk Reduction Engineering Laboratory. Cincinnati,
OH. 1990.
4. Schroeder. P. R. Gibson, A. C. and Smolen, M. D.. "Hydrologlc Evaluation of Landfill
Performance (HELP)," EPA/530/SW-84-010, U.S. EPA, MERL, Cincinnati, Ohio, 1984.
5. Barrett, R. J., "Use of Plastic Filters in Coastal Structures," Proc. 16th Intl. Conf. Coastal
Engr., Tokyo, Sept. 1966, pp. 1048-1067.
6. Rlos. N. and Gealt, M. A.. "Biological Growth In Landfill Leachate Collection Systems,"
Durability and Aging of Geosynthetics, Elsevier Appl. Scl. Publ., 1989, pp. 244-259.
7. Bass, J., "Avoiding Failure of Leachate Collection and Cap Drainage Systems," Final
Report of Contract No. 68-03-1822, U.S. EPA, Cincinnati, OH, Nov. 1985.
8. Ramke, H.-G.. "Considerations on the Construction and Maintenance of Dewatering
Systems for Domestic Trash Dumps," Translated by U.S. EPA from original German report
TR-87-0119, 1987.
9. Koemer, G. R and Koemer, R. M., "Biological Clogging of Geotextiles Used as Landfill
Filters; First Year's Results," GRI Report #3, Geosynthetlc Research Institute, Philadelphia,
PA, June 27, 1989.
10. American Society for Testing and Materials, ASTM D-4491, "Water Permeability of
Geotextiles by the Permittivity Method," Philadelphia, PA. 1991.
11. Raumann. G., "In-Plane Permeability of Compressed Geotextiles," Proc. Intl. Conf. on
Geotextiles, Las Vegas. NV, IFAI, pp. 55-60. 1982.
12. American Society for Testing and Materials, ASTM D-774, "Test Method for Bursting
Strength of Paper." Philadelphia, PA, 1991.
13. American Society for Testing and Materials. ASTM D-1682, "Test Method for Breaking
Load and Elongation of Textile Fabrics." Philadelphia, PA, 1991.
66
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Appendix "A"
BEHAVIOR OF BIOCIDE TREATED GEOSYNTHETICS
L- c - cv
-------
-------
APPENDIX "A"
BEHAVIOR OF BIOCIDE TREATED GEOSYNTHETICS
A-i Introduction
In light of the relatively large flow rate decreases that were observed in the course of this
study, an attempt at using biocides in the flow system was undertaken. This was done under the
assumption that the biocide would kill the micro-organisms that came into contact with it and that
the non-viable (i.e., dead) matter would pass through the system in much the same way that fine
particles or sediment moves through any other drainage system. Furthermore, the introduction of
the biocide was felt to be best achieved when delivered on a long-term basis rather than as one bulk
dosage. Thus, biocide was added to the polymer compound during fabrication of the respective
geonets or geotextiles. The reasoning for this approach was that the biocide would time release,
via molecular diffusion, through the polymer structure and migrate to the surface of the ribs or
fibers over a long period of time. If the approach is seen to be of value, calculations can then be
made as to the long-term time release behavior. This Appendix to the report describes our attempts
at increasing flow rates of landfill leachate filters and drainage systems using biocide treated
geosynthetics.
67
-------
A-2 Tvpe of Biocide
The biocide used in this study is Vinyzene® SB-1 PR manufactured by Morton Thiokol,
Inc. of Danvers, Massachusetts. Vinyzene SB-1 PR is a concentrate of 10, 10' -
oxybisphenoxarsine (OBPA) in a polypropylene resin carrier. The product, is supplied as a
homogeneous solid in pelletized form measuring approximately 3.5 mm by 2.5 mm. It is
recommended for use in polyolefins and other polymeric compositions requiring preservation
against fungal and bacterial deterioration. The manufacturer states that "low levels of Vinyzene
SB-1 EEA (a similar product but in an ethylene acrylic acid copolymer resin carrier) will provide
long term preservation against fungal and bacterial attack and will help prevent surface growth,
permanent staining, embrittlement and premature product failure." Vinyzene can be incorporated
into the polymer compound at any convenient stage of the manufacturing process. The product can
be fed into an extrusion operation in much the same way as pelletized color concentrates.
In 1976, EPA placed OBPA on its list of suspect pesticides that might be hazardous to
human health. EPA's review of animal and other studies on OBPA, however, indicated that it is
not as hazardous as originally suspected. On May 4, 1979 the U.S. Environmental Protection
Agency decided that the pesticide, OBPA, which is used in a wide variety of plastic consumer
products to protect them from fungal and bacterial damage, does not pose a threat to human health
or the environment if used in accordance with label instructions. This decision means that OBPA
has been restored to its former place on EPA's list of currently registered pesticides.
Materials containing OBPA include swimming pool liners, wall coating, vinyl roofs on cars,
marine upholstery, awnings, industrial fabric, and caulking for tubs, sinks, weatherscripping and
gutter repair. The EPA registration number for Vinyzene® is 2829-115 and Morton Thiokol's
patent number is 4,086,297.
Some selected physical and chemical properties of 10, lO'-oxybisphenoxarsine (OBPA) are
as follows.
68
-------
Molecular Formula:
Molecular Weight:
Structural Formula:
C24Hi6As203
502.2
Specific Gravity: 1.40-1.42
Appearance: White to off-white crystalline solid
Melting Point: 185 - 186°C.
Vapor Pressure: < 10-6 torr
-------
A-3 Incorporation of the Biocide into Different Geosvnthetics
The biocide was shipped to the respective geosynthetic fabrication facility for its inclusion
into the candidate geonet or geotextile. After the dosage was decided upon (it varied from 1 to 8%
by weight), it was added to the standard compound, suitably mixed and extruded into ribs (for
geonets) or fibers (for geotextiles).
In the first series of tests, either 1, 2 or 4% biocide was introduced into the compound to
produce a 250 mil thick, high density polyethylene (HDPE) geonet. For control purposes, the
same type of geonet was produced without the addition of any biocide. The cross section of the
columns for these tests consisted (from the top down) of sand/geotextile/geonet/gravel and they
were coded as Series "A", see Table A-l. Tests were conducted both saturated at all times (labeled
anaerobic) and allowed to air dry between readings (thus aerobic). All tests in this series were run
for 444 days duration.
The next series of tests, i.e. Series "B", utilized the biocide in the geotextile and did not use
a geonet. The cross section consisted of sand/geotextile/gravel. The geotextile was of the
nonwoven, needle-punched polypropylene variety and it contained either 2% or 4% biocide. The
biocide was introduced at the fabrication facility along with the manufacturers standard compound
of resin, carbon black (or other antidegradant) and processing package. As seen in Table A-l,
there were also geotextiles included with no biocide so as to act as the control columns. Tests were
conducted under both constantly saturated conditions (labeled anaerobic) and intermittently
saturated, then air dried condition (thus aerobic). All tests in this series were performed for 444
days.
Test Series "C" consisted of biocide treated geotextiles and no geonets; but unlike the
previous series, three different types of geotextiles were evaluated. The geotextiles were
nonwoven needle punched (as before) and also two types of woven monofilament fabrics with
different opening sizes, see Table A-l. The tests were also different in that gravel was used above
the geotextile instead of sand. Thus the flow column consisted of gravel/geotextile/gravel, with the
geotextiles treated with 2, 4 or 8% biocide. Again, the biocide was introduced at the
manufacturing facility. In this series, which lasted 121 days, all tests were kept saturated, thus
anaerobic.
70
-------
Table A-l - Conditions Within Flow Columns for Biocide Study
Coding (1)
Soil (2)
Geotextile (3)
Geotextile
Geotextile
Geonet (4)
Soil (5)
Condition
Above
Type
Size
AOS
Amt. Biocide
Amt. Biocide
Below
(mm)
Sieve
A0-AN
Sand
N-N-PP
0.15
100
0
0
Gravel
Anaerobic
A0-A
Sand
N-N-PP
0.15
100
0
0
Gravel
Aerobic
Al-AN
Sand
N-N-PP
0.15
100
0
1
Gravel
Anaerobic
Al-A
Sand
N-N-PP
0.15
100
0
1
Gravel
Aerobic
A2-AN
Sand
N-N-PP
0.15
100
0
2
Gravel
Anaerobic
A2-A
Sand
N-N-PP
0.15
100
0
2
Gravel
Aerobic
A4-AN
Sand
N-N-PP
0.15
100
0
4
Gravel
Anaerobic
A4-A
Sand
N-N-PP
0.15
100
0
4
Gravel
Aerobic
B0-AN1
Sand
N-N-PP
0.15
100
0
_
Gravel
Anaerobic
B0-AN2
Sand
N-N-PP
0.15
100
0
-
Gravel
Anaerobic
B0-A1
Sand
N-N-PP
0.15
100
0
-
Gravel
Aerobic
B0-A2
Sand
N-N-PP
0.15
100
0
-
Gravel
Aerobic
B2-AN
Sand
N-N-PP
0.15
100
2
-
Gravel
Anaerobic
B2-A
Sand
N-N-PP
0.15
100
2
-
Gravel
Aerobic
B4-AN
Sand
N-N-PP
0.15
100
4
-
Gravel
Anaerobic
B4-A
Sand
N-N-PP
0.15
100
4
-
Gravel
Aerobic
Notes
(1) Test Series "A" and "B" lasted 444 days; Test Series "C" lasted 121 days.
(2) Sand is a #40 Sieve Subrounded Ottawa Sand in a 4.0 inch thick layer above the geotextile
(3) N-N-PP = nonwoven needle punched polypropylene
W-M-PP1 = woven monofilament polypropylene AOS = 70
W-M-PP2 = woven monofilament polypropylene AOS = 40
(4) Geonet is a 250 mil HDPE
(5) Gravel is a 1" to 1.5" Subrounded Gravel
-------
Tabic A-l - Conlinued
Coding (1)
Soil (2)
Geolextile (3)
Gcotextile
Geoiexlile
Geonet (4)
Soil (5)
Condilion
Above
Type
Size
AOS
Ami. Biocide
Ami. Biocide
Below
(mm)
Sieve
C1-0-AN1
Gravel
N-N-PP
0.15
100
0
-
Gravel
Anaerobic
C1-0-AN2
Gravel
N-N PP
0.15
100
0
-
Gravel
Anaerobic
C1-2-AN1
Gravel
N-N-PP
0.15
100
2
-
Gravel
Anaerobic
C1-2-AN2
Gravel
N-N PP
0.15
100
2
-
Gravel
Anaerobic
C1-4-AN1
Gravel
N-N-PP
0.15
100
4
-
Gravel
Anaerobic
C1-4-AN2
Gravel
N-N-PP
0.15
100
4
-
Gravel
Anaerobic
C1-8-AN1
Gravel
N-N-PP
0.15
100
8
-
Gravel
Anaerobic
C1-8-AN2
Gravel
N-N-PP
0.15
100
8
-
Gravel
Anaerobic
C2-0-AN1
Gravel
N-N-PP
0.15
100
0
-
Gravel
Anaerobic
C2-0-AN2
Gravel
N-N-PP
0.15
100
0
-
Gravel
Anaerobic
C2-2-AN
Gravel
N-N-PP
0.15
100
2
-
Gravel
Anaerobic
C2-4 AN
Gravel
N-N-PP
0.15
100
4
-
Gravel
Anaerobic
C3-2-AN
Gravel
W-M-PP-1
0.21
70
2
_
Gravel
Anaerobic
C3-4-AN
Gravel
W-M-PP-1
0.21
70
4
"
Gravel
Anaerobic
C4-2-AN
Gravel
W-M-PP-2
0.42
40
2
-
Gravel
Anaerobic
C4-4-AN
Gravel
W-M-PP-2
0.42
40
4
-
Gravel
Anaerobic
-------
A-4 Field Testing and Evaluation Procedures
Flow rate testing for each of the columns with biocide treated geosynthetics were placed
within the four inch diameter incubation and test columns depicted in Figure A-l. As indicated in
Table A-l there were 8 columns in Series "A", 8 columns in Series "B" and 16 columns in Series
"C". Series "A" and "B" were evaluated over a 444 day duration and Series "C" was evaluated for
121 days duration.
All of the tests in this biocide study used leachate from landfill site DE-3. This particular
leachate has the highest concentration of COD, TS and BOD5 of the six landfill leachates which
were evaluated during the course of the project. The approximate properties of the leachate are as
follows:
• pH = 5.8
• COD - 40,000 mg/1
• TS = 17,000 mg/1
• BOD5 = 24,000 mg/1
Fresh leachate was used for each test since it was taken directly out of the sump at the low
elevation of the landfill or from the nearest underground storage tank.
The tests were of the falling head variety which measures the time of flight for a high head of
leachate to reach a lower value. The protocol for the test itself is included as Appendix "B" to this
report. Calculations allow for the determination of a "system" hydraulic conductivity, or
permeability coefficient which is in the units of cm/sec. This unit is the conventional one used in
EPA reports and manuals. Note, however, that the permeabiliy being measured is the permeability
of the composite system including each component which may retard flow. In this Appendix, the
"permeability" value will be used on a comparative basis, with the original value being the highest
that the system can possibly achieve.
73
-------
Figure A-l - Photograph of Field Incubation and Test Column
74
-------
A-5 Results of Test Series "A"
As indicated in Table A-l, this test series consisted of a sand/geotextile/geonet/gravel cross
section with the biocide having been introduced into the geonet. The biocide levels were at 0, 1,2
and 4% and tests were conducted under both anaerobic and aerobic conditions.
The system hydraulic conductivity, or simply "permeability", results for test Series "A" are
shown in Figures A-2 and A-3 representing anaerobic and aerobic conditions, respectively.
Separate curves are for the control and each biocide level in the geonet. Comparison of these two
figures indicates that there is essentially no difference in the flow characteristics from the anaerobic
to the aerobic state. Within the curves of each figure a nominal improvement in permeability from
using 2 or 4% biocide in the geonet was evidenced at the conclusion of the test peric^ of -44 days.
However, because the improvement in flow is nominal at the end of testing and flov. improvement
is not evidenced throughout the entire testing period, statistical variation in the data may influence
the behavioral trends. One general feeling is that using biocide in the geonet is simply not logical
since the flow rate in the geonet is relatively high. Thus the biocide probably did not have adequate
residence time to be effective.
75
-------
~ AO-AN
~ A1-AN
A2-AN
® A4-AN
100
200 300
Time (days)
400
500
Figure A-2 - Effect of Geonet Biocide Content on System
Permeability under Anaerobic Conditions
(Test Series "A")
76
-------
0.7
~ AO-A
• A1-A
p A2-A
© A4-A
0.6
£ 0.5
0.4
0 3
0.0
0
100
200
300
400
500
Time (dags)
Figure A-3 - Effect of Geonet Biocide Content on System
Permeability under Aerobic Conditions
(Test Series "A")
77
-------
A-6 Results of Test Series "B"
As indicated in Table A-l, this test series consisted of a sand/geotextile/gravel cross section
with the biocide having been introduced into the geotextile. The biocide levels were at 0, 2, and
4% and tests were conducted under anaerobic and aerobic conditions. The rational for this change
from the previous test series is that flow in the geotextile would be much lower than in the geonet
due to its much smaller void spaces. The greatly decreased flow rate in the geotextile would
possibly allow for the biocide to have a greater contact time with the micro-organisms in the
leachate and hence be more effective.
Figures A-4 and A-5 provide a comparison of anaerobic and aerobic conditions. A replicate
for the geotextile with 0% biocide was provided for each condition and the data was averaged for
plotting. A comparison of these figures reveals little difference in flow characteristics from
anaerobic to aerobic conditions. This same trend was seen previously with the geonet tests.
Generally, the geotextile with 4% biocide provided slightly higher flow rates with the exception of
the anaerobic state in which the geotextile clogged severely beyond 400 days. As with Series "A"
tests, statistical variation is bound to play a significant role. Two test specimens in Series "B", BO-
AX 1 and B4-A, were resin set and dissected to visually determine the extent of clogging. In each
specimen, as shown in Figure A-6, it appears as though the Ottawa sand has clogged within the
upper 1 to 2 inches of the specimen. Note the closeup photograph of Column B4-A where the
upper layer of soil was completely bonded together while the soil above the geotextile was loose.
The biofiJm apparently did not reach the level of the geotextile indicating that either the biocide is
too far from the biofilm itself or that the grain size distribution of the sand is sufficiently small to
create its own clogged layer.
-------
0.7
BO-AN
B2-AN
B4-AN
0.6
0.5
C- 0.4
0.3
0.2
0.0
100
0
200
300
400
500
Time (days)
Figure A-4 - Effect of Geotextile Biocide Content on System
Permeability under Anaerobic Conditions
(Test Series "B")
79
-------
0.7
BO-A
B2-A
B4-A
0.6
0.3
a
«
w
£ 0.2
o>
a.
0.0
0
100
200
300
400
500
Time (days)
Figure A-5 - Effect of Geotextile Biocide Content on System
Permeability under Aerobic Conditions
(Test Series "B")
80
-------
TErr«£WES-B-
Daik Areas
Show
Clogged Sand
Geo textile
Column B4-A
Figure A-6 - Photographs of Resin Set Columns of Test Series "B" Split in Half at the End
of 444 Days of Testing
81
-------
A-7 Results of Test Series "C"
After evaluating the flow columns of Test Series "A" and "B" for 323 days, it was apparent
that a clearly defined flow improvement resulting from biocide activity was not being observed. It
was considered likely that the biofilm layer was occurring in the upper portion of the sand, hence
the biocide in the geonet (Series "A") or in the geotextile (Series "B") was too far away from the
clogged layer to be effective. Thus, it become necessary to assemble an additional series of 16
columns without sand, which is the thrust of Series "C".
Series "C" columns consist of a cross section of gravel/geotextile/gravel. The gravel is 1.0
to 1.5 inch size and does little insofar as retarding flow is concerned. The geotextiles are treated
with varying amounts of biocide, from 0 to 8% (recall Table A-l) and all columns were evaluated
in the anaerobic condition. This latter decision was made since there was little difference in the
anaerobic and aerobic flow rates in the previous tests and anaerobic conditions are felt to better
simulate landfill leachate conditions. The geotextiles in this series varied considerably. Those used
were the following.
• nonwoven needle-punched with an opening size of 0.15 mm
• woven monofilament with a opening size of 0.21 mm
• woven monofilament with an opening size of 0.42 mm
The first part of Series "C" tests consists of the nonwoven needle punched polypropylene
geotextile with 0, 2, 4 and 8% biocide within the fabric. A replicate set was constructed so that the
values used in graphing are averages of the two data sets. An evaluation of varying biocide
contents is displayed in Figure A-7. There appears to be little difference in flow at the onset of
testing, however there is an improvement in flow with 8% biocide at the completion of testing 121
days later. The use of 8% biocide, however, may affect the strength characteristics of the fabric
and currently the EPA has restricted biocide content of this type in other media to 4%. As with the
other test series, statistical scatter is significant.
In the second pan of Series "C" testing, a different manufacturers nonwoven needle punched
polypropylene geotextile with 0, 2 and 4% biocide was used. A replicate was constructed for the
control, i.e., 0% biocide, and graphs were plotted using the average of data sets. To compare the
two different products, Figure A-8 was plotted. In the first month of testing, there is little
difference in flow rates. As the test progresses, the 2 and 4% biocide geotextiles tend to give better
82
-------
u
4J
W
•*.
E
u
3.0
2.5
2.0
" 1.5
1.0
£L
0.5
0.0
p C1-0-AN ••
~ C1-2-AN
¦ CI-4-AN
» n-R-AN
\
/
i
H
s
....
!
.......
! 1
25
50 75
Time (days)
100
125
Figure A-7 - Nonwoven Needle-Punched Effect of Geotextile
Biocide Content on System Permeability
(Test Series "C")
83
-------
3.0
D C1-0-AN
~ C1-2-AN
¦ CI-4-AN
<~ C2-0-AN
¦ C2-2-AN
o C2-4-AN
2.5
^ 2.0
£? 1.5
.0
0.5
0 0
25
50
75
125
0
100
Time (days)
Figure A-8 - Comparison of Two Nonwoven Needle-Punched
Geotextiles with Varying Biocide Content
(Test Series "C")
84
-------
flow rates with a large improvement in flow at 121 days. Statistical scattering of the data and the J
short duration of the testing are concerns with respect to the significance of the data.
TWo woven monofilament polypropylene geotextiles were used for the third part of the
Series "C" tests. The apparent opening sizes and other relevant test conditions are provided in
Table A-l. Each fabric was tested with 2 and 4% biocide content. A control with 0% biocide, was
not constructed for this test set. To compare the effects of opening size on clogging Figure A-9
was prepared. From the graph it is seen that the larger opening size geotextile provides a
measurable increase in flow rate with the 4% biocide content giving better results in general. The
smaller opening size fabric with 4% biocide clogged severely two months into the test. The four
samples in this series were then epoxy resin set and dissected in the same manner as the Series B
specimens. Photographs are given as Figure A-10. While difficult to see on the photographs, it
was obvious thai the larger opening size (0.42 mm) allowed more epoxy to flow through the
geotextile indicating that it was indeed providing better flow than the 0.21 mm opening size
geotextile.
85
-------
3.0
~ C3-2-AN
¦ C3-4-AN
~ C4-2-AN
• C4-4-AN
2.5
0.5
0.0
25
75
0
50
100
125
Time (dogs)
Figure A-9 - Comparison of Woven Monofilament Geotextile
Opening Size with Varying Biocide Content
(Test Series "C")
86
-------
Figure A-10 -Photographs of Resin Set Columns of Test Series "C" Split in Half at the End
of 121 Days of Testing
87
-------
A-8 Conclusions of Biocide Study
From the results of the Series "A" tests (biocide in geonets) and Series "B" tests (biocide in
geotextiles) it was concluded that the location of the biocide vis-a-vis the initial formation of a
biofilm layer is critical. This conclusion was tentatively reached after 323 days of conducting these
tests. It was confirmed at the termination of the 444 day tests after setting the test columns with
epoxy and cutting them apart. Clearly the biofilm layer was occurring at the top of the sand
column some 2 to 3 inches above the biocide treated geosynthetics, recall Figure A-6. While there
may have been some flow rate improvement due to high concentrations of biocide, it was very
subtile (at best) and was masked by the inherent scatter in the test data. There was essentially no
difference between flow rates in anaerobic versus aerobic conditions.
These findings led to Series "C" tests which contained no sand above the biocide treated
geosynthetic and forced the leachate to interface directly with the biocide. Rather than use a single
type of geotextile, three different types of geotextiles were utilized. They had opening sizes
varying from 0.15 mm (the nonwoven needle-punched styles used in test Series "B"), to 0.21 mm
(a woven monofilament), to 0.42 mm (another woven monofilament). Quite clearly, the flow rates
through the largest opening size geotextiles, i.e. the 0.42 mm, were the highest. This suggests to
us that micro-organisms (dead or alive) must be able to pass through the system. Whenever these
micro-organisms reside on, or within, the small pores of a filter (either natural soil or a geotextile)
there is a possibility of partial, or even complete, clogging.
88
-------
Appendix "B~
INDIVIDUAL TEST COLUMN RESULTS
OF PHASE n STUDY
(All 96 Columns In Phase n are Included In this Appendix along with
Each of the Four Remediation Attempts)
-------
I 00 *-
m z
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TIME (MONTHS)
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igure 1 - 5ystem Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column WM (NIC) AN/S
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Figure 2 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column WM (NO A/S
89
-------
8 10 12 1A 16 18 20 22 24
TIME(MONTHS)
Figure 3 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test WM (NO AN/W
ICO
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Flgu-e A - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column WM (NC) A/W
90
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Figure 5 - System Permeability Retained and Various Remediation Attempts for
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TIME (MONTHS)
Figure 6 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 arid Flow Test Column NW (HS) A/S
91
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Figure 8 - System Permeability Retained and Various Remediation Attempts Tor
Landfill PA-1 and Flow Test Column NW (H5) A/W
92
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Figure 9 - Systen Permeaolllty Retafned and Various Remediation Attempts for
Land* 111 PA-1 and Flow Test Column NW (N) 16 AM/S
100
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:fgj.-e 10 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column NW (N) 16 A/S
93
-------
100
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Figure 1 I - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column NW (N) 16 AN/W
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Figure \7 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column NW (N) 16 A/W
94
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Figure 13 - 5ystem Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column NW (N) 8 AN/S
loos'
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Figure 14 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-l and Flow Test Column NW CN) 8 A/5
95
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TIME(MONTHS)
System Permeability Retained and Various Remediation Attempts for
Landfill PA- I and Flow Test Column NW (N) 8 AN/W
100
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TIME(MONTHS)
Flgire 16 - System Permeability Retained and Various Remediation Attempts for
Landfill PA-1 and Flow Test Column NW (N) 8 A/W
96
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Figure 17 - System PermeaDlllty Retained and Various Remediation Attempts for
Landfill MY-2 and Flow Test Column WM (NC) AN/5
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TIME(MONTHS)
Ftgjre 18 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column WM (NC) A/5
97
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clgure 19 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column WM (NC) AN/w
6 10 12 14
TIME(MONTHS)
20 22
Figure 20 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column WM (NC) A/W
98
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TIME(MONTHS)
Figure 21 - System Permeability Retained and Various Remediation Attempts for
Landfill NV-2 and Flow Test Column NW (H5) AN/S
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Figure 22 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (HS) A/S
99
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6 8 10 12 14 16 16 20 22 24
TIME(MONTHS)
Flgjre 23 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (H5) AN/W
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Figure 24 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (HS) A/W
100
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Figure 25 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 16 AN/S
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Figure 26 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 16 A/S
101
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Figure 27 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 16 AN/W
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Figure 28 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 16 A/W
102
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Figure 29 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) B AN/S
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Figure 30 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 8 A/5
103
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TIME(MONTHS)
Figure 31 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 8 AN/w
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TIME(MONTHS)
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F1gu_e 32 - System Permeability Retained and Various Remediation Attempts for
Landfill NY-2 and Flow Test Column NW (N) 8 A/w
104
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TIME (MONTHS)
Figure 33 - System Permeability Retained and Various Remediation Attempts for
Land'111 DE-3 and Flow Test Column WM (NC) AIM/S
100?
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TIME (MONTHS)
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Figure 34 - System Permeability Retained and Various Remediation Attempts Tor
Landfill DE-3 and Flow Test Column WM (NC) A/S
105
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Figure 35 - System Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column WM (NC) AN/W
100
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TIME(MONTHS)
Figure 36 - System Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column WM (NC) A/W
106
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100
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TIME(MONTHS)
16 16 20 22
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Flgire 37 - System Permeability Retained and Various Remediation Attempts for
Laidflll Dt-3 and Flow Test Column NW (HS) AN/5
I 001H
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TIME(MONTHS)
Figure 38 - System Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column NW (HS) A/S
107
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TIME(MONTHS)
Figure 39 - Syste-n Permeability Retained and Various Remediation Attempts for
Landfill De-3 and Flow Test Column NW (H5) AN/w
too?
6 10 12 M 16 10 20 22 24
TIME (MONTHS)
Figure 40 - System Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column NW (H5) A/W
108
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TIME(MONTHS)
Flgjre 42 - System Permeability Retained and Various Remediation Attempts Tor
Landfill DE-3 aid Flow Test Column NW (16) A/S
109
-------
6 10 12 14 16 18 20 22 24
TIME(MONTHS)
Figure 43 - System Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column NW (16} an/W
too
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TIME(MONTHS)
Figure 44 - System Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column NW (! 6) A/W
110
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TIME(MONTHS)
Figure 45 - Systen Permeability Retained and Various Remediation Attempts for
Landfill DE-3 and Flow Test Column NW (B) AN/5
100*'
80
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16 18 20 22 24
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TIME (MONTHS)
Figure 46 - System Permeability Retained and Various Remediation Attempts for
Landfill OE-3 and Flow Test Column NW (8) A/5
111
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Figure 49 - System Permeability Retained and Various Remediation Attempts for
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Figure 51 - System Permeability Retained and Various Remediation Attempts for
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Figure 52 - System Permeability Retained and Various Remediation Attempts for
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Figure 54 - System Permeability Retained and Various Remediation Attempts ror
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Figure 56 - System Permeability Retained and Various Remediation Attempts for
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Figure 72 - System Permeability Retained and Various Remediation Attempts for
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TIME (MONTHS)
Ffgure 73 - System Permeability Retained and Various Remediation Attempts for
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Figure 74 - System Permeability Retained and Various Remediation Attempts for
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126
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Figure 77 - System Permeability Retained and Va-lous Remediation Attempts for
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Figure 78 - System Permeability Retained and Various Remediation Attempts for
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Flgire 79 - System Permea&lllty Retained and Various Remediation Attempts for
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Figure 81 - System Permeability Retained and Various Remediation Attempts for
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Figure 84 - System Permeability Retained and Various Remediation Attempts for
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Figure 85 - System Permeability Retained and Various Remediation Attempts for
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Figure 86 - System Permeability Retained and Various Remediation Attempts for
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Figure 87 - System Permeability Retained and Various Remediation Attempts for
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132
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133
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134
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136
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Appendix "C"
TEST DEVICE AND METHOD
TO ASSESS FILTER CLOGGING*
This test method has been a Geosynthetic Research Institute Standard under the designation
of GRI-GT2. As of March 1. 1991 It became an ASTM Standard under the designation of D1987-
91. Hard copy should be available by May 1, 1991. A1 that time the GRI Standard will be
eliminated from any further distribution.
i^'c"
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Getfeiines nGcomembrartes
Ccognds
Gc
-------
3. Terminology
3.1 peotexrile. n - a permeable geosynthetic comprised solely of textiles.
3.2 permeability, n - the rate of flow of a liquid under a differential pressure through a
material.
Discussion - In peotextiles. permeability refers to hydraulic conductivity
3.3 permittivity, (y) (t-1), n - of geotextiles. the volumetric flow rate of water per unit, in a
cross sectional area head under laminar flow conditions.
3.4 aerobic, n - a condition in which a measurable volume of air is present in the incubation
chamber or system.
Discussion - In geotextiles. this condition can potentially contribute to the growth of
micro-organisms.
3.5 anaerobic, n - a condition in which no measurable volume of air is present in the
incubation chamber or system.
Discussion - In peotexriles. this condition cannot contribute to the growth of micro-
organisms.
3.6 back flushing, n - a process by which liquid is forced in the reverse direction to the flow
direction.
Discussion - In other drainage application areas, this process is commonly used to free
clogged drainage systems of materials that impede the intended direction of flow.
3.7 biocide. n - a chemical used to kill bacteria and other microorganisms.
4 . Summary of Test Method
4.1 A geotextile filter specimen or geotextile/soil filter composite specimen is positioned in a
flow column so that a designated liquid flows through it under either constant or falling head
conditions.
4.1.1 The designated liquid might contain micro-organisms from which biological
growth can occur.
4.2 Flow rate is measured over time, converted to either permittivity or permeability, and
reported according.
4.2.1 Between readings, the test specimen can be allowed to be in either nonsaturated
or saturated conditions.
4.2.2 Back flushing can be introduced from the direction opposite to the intended flow
direction and evaluated accordingly.
4.2.3 Biocide can be introduced with the back flushing liquid, or introduced within the
test specimen, and evaluated accordingly.
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5. Significance and Use
5.1 This test method is performance oriented for determining if, and to what degree,
different liquids create biological activity on geotextile filters thereby reducing their flow
capability. The use of the method is primarily oriented toward landfill leachates but can be
performed with any liquid coming from a particular site or synthesized from a predetermined
mixture of biological microorganisms.
5.2 The test can be used to compare the flow capability of different types of geotextiles or
soil/geotextile combinations.
5.3 This test will usually take considerable time, e.g., up to 1,000 hours, for the biological
activity to initiate, grow, and reach an equilibrium condition. The curves resulting from the
test are intended to indicate the in situ behavior of a geotextile or soil/geotextile filter.
5.4 The test specimen can be incubated under non-saturated drained conditions between
readings, or kept saturated at all times. The first case allows for air penetration into the flow
column and thus aerobic conditions. The second case can result in the absence of air, thus it
may simulate anaerobic conditions.
5.5 The flow rate can be determined using either a constant head test procedure or on the
basis of a falling head test procedure. In either case the flow column containing the geotextile
or soil/geotextile is the same, only the head control devices change.
Note 1 —It has been found that once biological clogging initiates, constant head tests
often pass inadequate quantities of liquid to accurately measure. It thus
becomes necessary to use falling head tests which can be measured on the
basis of time of movement of a relatively small quantity of liquid between two
designated points on a clear plastic standpipe.
5.6 If the establishment of an unacceptably high degree of clogging is seen in the flow rate
curves, the device allows for backflushing with water or with water containing a biocide.
5.7 The resulting flow rate curves are intended for use in the design of full scale geotextile or
soil/yeotextile filtration systems and possible remediation schemes in the case of landfill leachate
collection and removal systems.
6. Apparatus
6.1 The flow column and specimen mount consists of a 100 mm (4.0 in.) inside diameter
containment ring for placement of the geotextile specimen along with upper and lower flow
tubes to allow for uniform flow trajectories (see Figure 1). The flow tubes are each sealed
with end caps which have entry and exit tubing connections (see Figure 1). The upper tube
can be made sufficiently long so as to provide for a soil column to be placed above the
geotextile. When this type of combined soil/geotextile cross section is used, however, it is
difficult to distinguish which material is clogging i.e., the soil or the geotextile. It does
however simulate many existing filtration systems. In such cases, a separate test setup with
the geotextile by itself will be required as a control test and the difference in behavior between
the two tests will give an indication as to the contribution of soil clogging to the flow
reduction.
139
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6.2 Hydraulic head control devices are required at both the inlet and outlet ends of the flow
column. Figure 2 shows the complete setup based on constant hydraulic head monitoring
where concentric plastic cylinders are used with the inner cylinders being at the elevation
from which head is measured. The elevation difference between the inner cylinder at the inlet
end and the inner cylinder at the outlet end is the total head across the geotextile test specimen
(or soil/geotextile test specimen in the case of a combined test column). Note that the
elevation of the outlet must be above the elevation of the geotextile.
6.3 A hydraulic head siandpipe above the flow column is required for falling hydraulic head
monitoring. Figure 3 shows this type of test configuration in which a clear plastic standpipe
is placed above the flow column. Liquid movement is monitored for the time of flight
between two marks on the standpipe. Note that the elevation of the outlet must be above the
elevation of the geotextile.
6.4 The overall test system dimensions are sufficiently small so that either of the above
mentioned units can be used at a field site if desirable. They can either be kept stationary in
the laboratory or in the field, or they can be transported from the laboratory to the field site
when required.
6.5 The permeating liquid is generally site specific and often comprises landfill leachate.
Other liquids for which biological clogging is of concern can also be evaluated. The liquid
can be synthesized on an as-required basis.
Note 2 — A synthesized liquid which has been used in determining the resistance of
plastics to bacteria is Pseudomonas aeruginosa ATCC 13388 (available from
American Type Culture Collection, 12301 Parklawn Drive, Rockville, MD
20852) or MYCO B 1468 (available from Mycological Services, P. O. Box
126, Amherst, MA 01002). Specific details must be agreed upon by the
parties involved.
7. Sampling
7.1 Lot Sample — Divide the product into lots and take the lot sample as directed in Practice
D4354.
7.2 Laboratory Sample — For the laboratory sample, take a swatch extending the full width
of the geotextile of sufficient length along the selvage from each sample roll so that the
requirements of the following section can be met. Taie a sample that will exclude material
from the outer wrap and inner wrap around the core unless the sample is taken at the
production site, then inner and outer wrap material may be used.
7.3 Test Specimens — From the laboratory sample select the number of specimens as per the
number of flow columns to be evaluated. Space the specimens along a diagonal on the unit
of the laboratory sample. Take no specimens nearer the selvage or edge of the laboratory
sample than 10% of the width of the laboratory sample. The minimum specimen diameter
should be 100 mm (4.0 in.) so that full fixity can be achieved around the inside of the flow
column.
8. Conditioning
8.1 There is no conditioning of the geotextile test specimen, per se, since this test method is
a hydraulic one and the conditions of the permeating fluid will be the controlling factor.
140
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8.2 The relative humidity should be 100% except during times of air drying between non-
saturated test readings. For saturated conditions the relative humidity should always be
100%.
8.3 The temperature of the test over its entire duration is important. It is desirable to track
temperature continuously. If not possible, frequent readings at regular intervals are required.
9. Procedure "A" • Constant Head Test
9.1 Select and properly prepare the geotextile test specimen. Trim the specimen to the exact
and full diameter of the inside of the flow column.
9.2 Fix the geotextile test specimen to the inside of the containment ring. If a water
insoluable glue is used be sure that any excess does not extend into the flow area of the
geotextile.
9.3 Caulk the upper surface of the geotextile to the inside of the containment ring using a
silicon based caulk and allow it to completely cure. The caulk must be carefully placed so as
not to restrict flow through the geotextile.
9.4 Insert the upper and lower tubes into the containment ring and create a seal. If polyvinyl
chloride (PVC) tubing and fittings are being used, first a cleaner and then a solvent wipe is
used to make the bond.
9.5 If a screen or gravel of approximately 50 mm (2 in.) size is necessary to support the
geotextile it must be placed with the device in an inverted position.
9.6 Place the lower end cap on the device and make its seal.
9.7 If soil is to be placed over the geotextile, place it at this time. Place the soil at its targeted
moisture content and density taking care not to dislodge or damage the geotextile beneath.
9.8 Place the upper end cap on the device and make a permanently seal.
9.9 Connect flexible plastic tubing from the flow column's top and bottom to the head
control devices. At this point the system should appear as shown in the photograph of
Figure 2.
9.10 Adjust the total head lost to 50 mm (2.0 in.) and initiate flow via the introduction of the
permeating fluid to the system. When using leachate, proper safety and health precautions
must be maintained depending upon the nature of the leachate itself.
Note 3—It is suggested to use 50 mm (2 in.) total head difference since this is the
prescribed value used in the permittivity test of ASTM D4491. Other values of
head or hydraulic gradient, as mutually decided upon by the parties involved,
could also be used.
9.11 Convert the liquid collected from the discharge tube to flow rate (liters/min or
gaJ./min.) and repeat the measurement three times. Report the average of this value.
9.12 Increase the total head lost if desired. Heads of 100 mm (4.0 in.), 200 mm (8.0 in.),
and 300 mm (12.0 in.) might be considered. These relatively high values of total head may
be required if the geotextile begins to clog.
141
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9.] 3 Afier readings are completed, disconnect the head control devices. If non-saturated
(aerobic) conditions are desired, the bottom end cap outlet is allowed to vent to the
atmosphere. If saturated conditions are desired, the flexible plastic rubing from the bottom
end cap must remain in position and be brought higher than the elevation of the geotextile or
soil within the test column. This will maintain saturated conditions between readings.
9.14 Use fresh liquid for each set of measurements since changes, either biological or
particulate in nature, may influence the test results.
10. Procedure "B" - Falling Head Test
10.1 Select and properly prepare the geotexdle test specimen. Trim the specimen to the exact
and full diameter of the inside of the flow column.
10.2 Fix the geotextile test specimen to the inside of the containment ring. If a water
insoluable glue is used be sure that an excess amount does not extend into the flow area of
the geotexule.
10.3 Caulk the upper surface of the geotextile to the inside of the containment ring using a
silicon based caulk and allow it to completely cure. The caulk must be carefully placed so as
not to restrict flow through the geotextile.
10.4 Insert the upper and lower tubes into the containment ring and create a permanent seal.
If polyvinyl chloride (PVC) tubing and fittings are being used, first a cleaner and then a
solvent wipe is used to make the bond.
10.5 If a screen or a gravel of approximately 50 cm (2 in.) size is necessary to support the
geotextile it must be placed with the device in an inverted position.
10.6 Place the lower end cap on the device and make its seal.
10.7 If soil is to be placed over the geoiextile, place it at this time. The soil should be placed
at its targeted moisture content and density taking care not to dislodge or damage the
geotextile beneath.
10.8 Place the upper end cap on the device and make a seal.
10.9 Attach a clear, rigid plastic standpipe to the upper end cap. The standpipe should have
clearly visible markings at regular intervals to monitor the movement of liquid. At this point
the system should appear as shown in the photograph of Figure 3.
10.10 Fill the standpipe to a level above its upper mark.
10.11 Allow for flow through the system until the liquid level reaches the upper mark and
then stan a stopwatch.
10.12 Allow flow to continue unimpeded until the liquid level reaches the lower standpipe
mark and immediately stop the stopwatch so as to record the elapsed rime.
10.13 Repeat this measurement procedure three times. The average of this value is to be
reported.
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10.14 After readings are completed, disconnect the head control devices. If nonsaturated
conditions are desired, the bottom end cap outlet is allowed to vent to the atmosphere. If
saturated conditions are desired, the flexible plastic tubing from the bottom end cap must
remain in position and be brought higher than the elevation of the geotextile or soil within the
test column. This will maintain saturated conditions between readings.
10.15 Use fresh liquid for each set of measurements since changes, either biological or
particulate in nature, may influence the test results.
11 . Calculations for Procedure "A" - Constant Head Test
11.1 Flow Rate per Unit Area is calculated on the basis of the average flow rate measured
during conducting of the test. This value is then divided by the cross sectional area of the
geotextile for the flow rate per unit area, or "flux". The units are liters/min-cm2 or gal/min-
ft2.
11.2 Permittivity can be calculated using Darcy's formula for a constant head flow test.
q
= k i A
q_
= ki
A
Ah
= k —
t
q
k
A(Ah)
and — = V
t T A(Ah)
where
q = flow rate (LVr)
A = cross sectional area (L2)
k = coefficient of permeability (L/T)
t = geotextile thickness (L)
i = hydraulic gradient (L/L)
Ah = change in total head (L)
V = permittivity (T^1)
11.3 Plotting of the results is very descriptive of the process as it is ongoing. Figure 4
presenis a number of possible trends in the resulting behavior.
12. Calculation for Procedure "B" - Falling Head Test
12.1 Permittivity is calculated when using the geotextile by itself with no soil. It is based on
Darcy's formula which is integrated over the head lost during the arbitrary time interval At
and results in the following equation.
k h
t=V-23_ l„8l0^
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k = coefficient of permeability (L/T)
t = thickness (L)
V = permittivity (T^1)
a = area of liquid supply standpipe (L2)
A = area of test specimen (L2)
AT = time change between hg and/y (T)
hQ = head at beginning of test (L)
/zy - head at end of test (L)
12.2 The permeability coefficient is calculated when using soil and geotextile together. It
uses the exact formulation as above in the following form.
, ax i ho
A AT g10 hf
12.3 Plotting of the results is very descriptive of the process as it is ongoing. Figure 4
presents a number of possible trends in the resulting behavior.
13. Report
13.1 State that the specimens were treated as directed in this Test Method or state what
modifications were made.
13.2 Report on the following information:
13.2.1 The method of holding the test specimen in the containment ring.
13.2.2 The use or nonuse of soil above the geotextile.
13.2.3 The type, style and description of the geotextile test specimen
13.2.4 The type of permeating liquid.
13.2.5 Whether nonsaturated or saturated test conditions.
13.3 Report on trends in the results:
13.3.1 The behavior of the curves (see Figure 4 for possible trends).
13.3.2 The reasons for terminating the tests.
13.3.3 The temperature of the liquid used in the tests.
13.3.4 Possible remediation schemes if clogging occurred.
13.4 Identify the microorganisms which caused the clogging if it occurred (optional).
14. Precision and Bias
14.1 Precision — The precision of the procedure in this test method for measuring the
biological clogging of geotextiles is being established.
14.2 Bias — The procedure in this test method for measuring the biological clogging of
geoiextiles has no bias because the value of that property can be defined only in terms of a
test method.
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Flow
r Sr
Geotextile
Test
Specimen
Upper End Cap
Soil
(Optional)
Upper Tube
100 mm
Containment Ring
<4 Lower Tube
100 mm
V
Lower End Cap
100 mm
Figure 1 - Flow Column to Contain Geotextile Test Specimen
145
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Geotextile
Test Specimen
Outlet
Head
Control
Inlet Liquid
Inlet Head Control
Overflow
Flow Column
- Flow Column with Inlet and Outlet Hydraulic Head Control Devices For Constant Head Test
-------
Clear
Plastic
Standpipe
Geotextile
Test Specimen
Flow Column
Figure 3 - Flow Column with Standpipe For Variable (Falling) Head Test
-------
Flow Rate
or
Permittivity
Flow Rate
or
Permittivity
Moderate
Time
Time
(a) No, or Nominal, Clogging
(b) Various Degrees of Clogging
- cw Rate
or
Permittivity
Flow Rate
or
Slow Permittivity
Moderate
Time
Biocide Backtlush
Time
(c) Retarded Clogging
(d) Biocide and/or Backflushing
Treatment
Figure 4 - Possible Long-Term Flow Behavior of Geotextile Filters
Subjected to Liquids Containing Biological Microorganisms
148
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