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EVALUATION OF WHOLE WASTE TIRES AS BEDDING MEDIA FOR LIQUID INJECTION LINES IN MUNICIPAL SOLID WASTE LANDFILLS
By
JOSE ANTONIO YAQUIAN LUNA
A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2012
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© 2012 Jose Antonio Yaquian Luna
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To my parents
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ACKNOWLEDGMENTS
I would like to express my gratitude to my advisor, committee chairman Professor
Timothy Townsend, for his unconditional support through this endeavor. He shared
valuable knowledge and instructed me on how to become a presenter, teacher, and
researcher. He inspired me with his work ethics and devotion towards academic
accomplishment. I would like to thank Professor Michael Annable and David Bloomquist
for their guidance and knowledge. I would also like to thank Dr. Rafael Munoz Carpena
and Dr. Robert Gilbert for their support and advice throughout this process.
I am very thankful to Darrell O’Neal, Executive Director, Perry Kent from NRRL for
their guidance, trust and friendship.
I would like to thank Dr. Hwidong Kim, Dr. Youngmin Cho and Dr. Pradeep Jain for
sharing their knowledge and experience. Also my friends, Dr. Ravi Kadambala, Dr.
Shrawan Singh, James Lloyd, Adrian Gale, Max Krause, Saraya Sikora and Wesley
Oehmig for their cooperation.
At last, to my family and Julie McLaughlin for their love and unconditional support
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TABLE OF CONTENTS page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 7
LIST OF FIGURES .......................................................................................................... 8
LIST OF ABBREVIATIONS ........................................................................................... 10
ABSTRACT ................................................................................................................... 11
CHAPTER
1 INTRODUCTION .................................................................................................... 13
1.1 Background ................................................................................................... 13
1.2 Problem Statement ....................................................................................... 14 1.3 Objectives ..................................................................................................... 16 1.4 Research Approach ...................................................................................... 17
1.5 Organization of Thesis .................................................................................. 18
2 LITERATURE REVIEW .......................................................................................... 19
2.1 Bioreactor Landfill ......................................................................................... 19 2.2 New River Bioreactor Project ........................................................................ 20
2.3 Horizontal Liquids Addition System ............................................................... 24 2.4 Previous Leachate Injection Lines Experiences ............................................ 25 2.5 Fluid Conductance ........................................................................................ 26
2.6 Tires Reuse and Disposal ............................................................................. 28
3 METHODS AND MATERIALS ................................................................................ 30
3.1 Site Description ............................................................................................. 30 3.2 Innovative Recycling Grant Development and Permit ................................... 30 3.3 Surface Infiltration Lines Experiment ............................................................. 31
3.4 Horizontal Injection Lines Location ................................................................ 32
3.5 Leachate Recirculation System Construction ................................................ 34 3.5.1 Configuration A ................................................................................... 37 3.5.2 Configuration B ................................................................................... 38
3.5.3 Configuration C ................................................................................... 38 3.6 Waste Placement Above Injection Lines ....................................................... 40 3.7 System Operation and Monitoring ................................................................. 41 3.8 Experiments .................................................................................................. 44 3.9 Injection Schedule ......................................................................................... 45
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4 RESULTS AND DISCUSSION ............................................................................... 47
4.1 Construction and Operational Observations.................................................. 47 4.2 Total Volume Added ...................................................................................... 50
4.3 Individual Line Performance .......................................................................... 51 4.4 Measurement of Fluid Conductance ............................................................. 54
5 CONCLUSSIONS AND RECOMMENDATIONS .................................................... 67
5.1 Summary ....................................................................................................... 67 5.2 Conclusions ................................................................................................... 68
5.3 Recommendations ........................................................................................ 69
LIST OF REFERENCES ............................................................................................... 71
BIOGRAPHICAL SKETCH ............................................................................................ 73
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LIST OF TABLES
Table page 2-1 Research on liquid distribution systems developed in NRRL. ............................ 20
2-2 Fluid conductance values obtained on previous research. ................................. 26
2-3 Different uses for recycled tires .......................................................................... 28
3-1 Timeline of tire project experiment in NRRL. ...................................................... 35
3-2 Timeline detailing different stages of tire project................................................. 44
4-1 Labor and amount of tires used on the construction of injection lines. ............... 47
4-2 Issues associated with the construction of different tire configurations for horizontal lines. ................................................................................................... 50
4-3 Hours of operation and injected volume on each operational section of the tires project. ........................................................................................................ 51
4-4 Main highlights of horizontal injection lines individual performance .................... 52
4-5 Average flows and applied pressure. .................................................................. 57
4-6 Fluid conductance (m/s) fluctuation during injection, contrast of early and later injection events. .......................................................................................... 59
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LIST OF FIGURES
Figure page 2-1 Typical leachate recirculation rates (Lm-2) in several bioreactor landfills ............ 27
2-2 Landfill injection line diagram to illustrate fluid conductance measurement and equation ....................................................................................................... 28
3-1 Cross section of Cell V, New River Regional Landfill ......................................... 33
3-2 Plan View NRRL with injection lines and infrastructure. ..................................... 36
3-3 Configuration A horizontal injection line being built on top of Cell V of NRRL .... 37
3-4 Configuration B, under construction, injection line can be appreciated on top of the first two layers of tires. .............................................................................. 38
3-5 Configuration C. Line III of Phase II as it was being constructed. ....................... 39
3-6 Injection line with the geocomposite installed. .................................................... 40
3-7 Injection lines being covered with waste. ............................................................ 41
3-8 Monitoring setup for the horizontal injection lines. .............................................. 43
3-9 Pressure transducer inserted and attached into horizontal injection lines. ......... 44
4-1 Injection line being pushed inside of the trench during Phase I construction. ..... 48
4-2 Cover soil being removed from the surface of Cell V for line I construction. ....... 48
4-3 Landfill gas relief devices installed on the solid pipe section of horizontal injection lines. ..................................................................................................... 55
4-4 Pressure and flow into horizontal injection line under two different venting scenarios ............................................................................................................ 57
4-5 Typical water level behavior during leachate injection (Feb 1st, 2012) ............... 58
4-6 Typical water level inside injection lines during experiment (Line I). ................... 58
4-7 Fluid conductance values of Phase I (Jan-Feb, 2012) ........................................ 60
4-8 Fluid conductance values of Line I (Jan-Feb, 2012) ........................................... 60
4-9 Fluid conductance values of Line IV (Jan-Feb, 2012) ......................................... 61
4-10 Fluid conductance values of Line V (Jan-Feb, 2012) .......................................... 61
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4-12 Volume of leachate per unit of length of horizontal injection lines using different materials as bedding media .................................................................. 63
4-13 Typical leachate volume recirculated per unit of area (Lm-2) in several bioreactor landfills throughout the United States. ............................................... 66
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LIST OF ABBREVIATIONS
ACSWL Alachua County South West Landfill
EPA Environmental Protection Agency
FAC Florida Administrative Code
FDEP Florida Department of Environmental Protection
HDPE High Density Polyethylene
HIL Horizontal Injection Lines
MSW Municipal Solid Waste
NRRL New River Regional Landfill
PCNCL Polk County North Central Landfill
PVC Polyvinyl Chloride
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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science
EVALUATION OF WHOLE WASTE TIRES AS BEDDING MEDIA FOR LIQUID
INJECTION LINES IN MUNICIPAL SOLID WASTE LANDFILLS
By
Jose Antonio Yaquian Luna
May 2012
Chair: Timothy G. Townsend Major: Environmental Engineering Sciences
Development of liquid addition systems is a crucial factor in the improvement of
bioreactor landfill technology. Research on this topic aims to improve liquids distribution
within the landfill, while operating it under safe conditions. More homogenously
distributed liquids will lead to higher decomposition rates of the degradable fraction of
the waste, and will increase in landfill gas generation which consequently generates
gains in airspace.
The installed system consisted on a set of horizontal injection on which whole
waste tires were used as bedding media. Lines were installed on the surface of an
active cell and later covered with two lifts of municipal solid waste, each of the lifts was
6 m thick. Six injection lines were constructed; two of them were lost within the first six
months of operation. Leachate was injected in the four remaining lines. Overall, a total
10,700 m3 of leachate were injected over a 19 month period. Performance of the
injection lines was evaluated in terms of fluid conductance on the remaining injection
lines. Leachate flow and applied water pressure inside of the injection lines were
measured for the last three months of operation. Typical responses during this period
varied from 6.7x10-7 ms-1 to 1.2x10-6 ms-1. Fluid conductance values reported on this
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paper were found to be similar to previous research with the exemption of one
experiment. This was attributed to site specific conditions, such as higher compaction of
the waste and the placement of the injection lines on top of a 0.3 m thick layer of clayey
soil, unlike previous studies where injection lines were surrounded by waste only. The
overall performance of whole tires as bedding media for horizontal injection lines was
found to be satisfactory and comparable with other medias. Even though fluid
conductance values were not outstandingly high, the volume of leachate injected per
unit of length of injection line was found to be substantially higher than other
experiments. From an operational perspective, the amount of leachate injected per cell
was higher than several other bioreactors using horizontal injection lines as liquids
addition method. Finally, by constructing injection lines using whole tires costs in waste
excavation, relocation of the waste and bedding media acquisition costs were avoided.
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CHAPTER 1 INTRODUCTION
1.1 Background
Nationwide 243 million tons of MSW were generated in 2009; this amount of waste
has remained more or less constant for the last decade. After a steady increase for
more than three decades, recycling and waste combustion with energy recovery are
experiencing a slower growth. Waste combustion has become prohibitively costly in
some regions. Land disposal is currently the most practiced municipal solid waste
disposal method in the U.S.; fifty five percent of the waste generated was landfilled in
2009. Consequently, as waste generation has increased and the number of operating
landfills declined, each landfill, on average, receives a substantially higher amount of
waste than in the past (EPA, 2009). This increase in waste acceptance together with
tighter environmental regulation has driven engineers and operators to make
improvements on landfill design and management. Conventional landfill design and
operation aims to store waste in a manner that reduces any inputs, encapsuling it by
using landfill liners and caps, hence the amount of water that enter the unit is
minimized. Consequently, the decomposition rate of the MSW’s biodegradable fraction
is slowed.
During the last decade, a significant amount of research has explored the
enhancement of the landfilling process. Being bioreactor landfill one of the biggest
achievements of these efforts. Bioreactor, in contrast with conventional landfills, uses
liquid addition to accelerate decomposition processes within the organic portion of the
waste. By taking this approach landfills become a treatment, rather than a storage
facility. Biological decomposition of waste accelerates gas production and air space
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recovery. In addition, leachate management costs diminish as it is being continuously
recirculated. Research on the improvement of liquid distribution systems has become
fundamental for the development of the bioreactor technology.
1.2 Problem Statement
The development of bioreactor technology in recent decades has lead researchers
to focus on the improvement of liquid addition systems (Pohland, 1975). Extensive
research has been conducted on this subject due to its vital importance for bioreactor
operation. Liquid addition design is used fundamentally to properly enhance biological
activity and prevent deleterious consequences of incorrect operation such as landslides
and slope failures. It is vital for researchers to provide designers and operators with
reliable data for the safe implementation of such technology. Injection of liquids has
been performed by various methods; The use of ponds and spraying liquids on the
landfills surface was explored, however these methods presented some operational
disadvantages related to smell and lack of feasibility; further explanation of these
technologies can be found elsewhere (Townsend, 1995; Reinhart and Townsend, 1997;
Miller and Emge, 1997; Townsend and Miller, 1998; Mehta et al., 2002). Vertical
injection lines gained popularity as they were used to retrofit fully constructed cells in
conventional landfills for liquids injection. Jain (2005) carried out extensive research on
the use of vertical wells; resulting in some valuable lessons. Surface seeps were likely
to occur if the hydrostatic injection head was above the surface of the landfill. There was
an uneven liquid distribution of liquid due to the different levels of compaction on the
waste profile. Moreover, differential settlement was observed around injection lines as
consequence of the heterogeneity of the liquids distribution. Finally, the injection of
liquids at a constant pressure required continuous monitoring for possible seeps.
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Presently, due to operational practicality horizontal injection lines are the most
commonly used technique for liquids injection. Horizontal injection lines have been
adopted in pre-existing operational landfills as well as in the design for new landfills.
Different types of bedding material have been used in the construction of horizontal
injection systems. The election of such materials depends mostly on the availability and
cost. Previous bioreactor studies have used a variety of materials such as crushed
glass, shredded tires, and mulch (Townsend and Miller 1998, Larson 2007, Kumar
2009). The mentioned materials have a low market value which makes them attractive
to be used for this purpose.
Scrap tires are widely available and although there are some beneficial uses for
them; disposal options are still needed. Shredding tires represents an opportunity for
the disposal of tires in class I landfills, since whole tires are banned from being disposed
in such facilities (Florida FAC). Shredding tires generally represents a financial cost,
implies the acquisition of gridding machinery and the construction of tire handling units.
Currently, whole tires are either used as fuel for incinerators, landscape material,
as a base for land application, or they are stockpiled (U.S. EPA 2006), the later being
considered a fire hazard. The U.S. EPA has estimated that roughly 270 million of the
300 million scrap tires generated each year are recycled or allocated for other beneficial
uses, the remaining tires are either stockpiled or placed in landfills (either landfills or
monofills). Since whole tires are banned, in most states, from disposal in class I
landfills, their use as a bedding material has not been explored. However, previous
research efforts using shredded tires as bedding media (Townsend 1995, Larson 2007,
Kumar 2009) produced satisfactory results. The durability, geometry and availability of
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whole scrap tires, together with positive experiences using shredded tires, motivated the
investigators to request a permit to use whole scrap tire as part of a liquids injection
system in an operational Florida landfill. The investigators received an Innovative
Recycling Grant from the FDEP (Florida Department of Environmental Protection) in
2007 to do research on the use of whole tires as bedding material on horizontal injection
lines in landfills. After receiving the permit and funding from FDEP; Singh 2010
performed the first out of two phases on this project. Singh constructed four surface
infiltration trenches and operated them for 16 days. This was the second phase of the
project, it aimed to build upon those previous experiences and examine the
performance of whole tires as bedding material for horizontal injection lines and
compare it with previously used medias.
1.3 Objectives
This master’s research explores the improvement of a basic operational aspect of
a bioreactor landfill by performing a full-scale experiment on the use of whole scrap tires
in three different configurations as the bedding media of horizontal liquid injection lines.
The bioreactor landfill that was the subject of this experiment is located in North Florida.
The construction of the horizontal injection lines went from May to December of 2010.
Research consisted of two phases. Phase I was the experiment performed by Singh
(2010) on surface infiltration trenches. Phase II consisted on five horizontal injection
lines, lines constructed by Singh were added as a single line after they were all
connected to a common manifold. Both phases of the project were covered with two lifts
of 6m thick each. Operation of the injection lines was started as the lines were
constructed and later covered with waste. By January 2011 all the lines were
constructed and covered with waste. The project was operated for a 20 month period,
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starting on May 2010 until February 2012.This paper makes an emphasis on the last
two months of operation as monitoring equipment of the project was improved, thus the
amount of compiled data increased allowing a deeper analysis of the results.
The project was monitored using in-situ instrumentation to measure hydraulic head
and volume of liquids injected into the landfill unit. The first objective on this experiment
was to measure the fluid conductance on horizontal injection lines constructed with
whole scrap tires. Liquid flow and water level inside of the injection lines were measured
with an analog signal flow meter and a pressure transducer, respectively. Additionally
the second objective was to provide an evaluation of whole tires as a bedding material
for the construction of horizontal injection lines in different configurations. The
comparison was made between lines constructed with whole tires in several
configurations and other bedding materials using fluid conductance as the main
parameter.
1.4 Research Approach
Objective 1. Evaluate the use of whole tires as bedding material for the
construction of liquids injection lines
Approach. Four injection lines were operated on top of a landfill active cell, such
lines were constructed using perforated pipe surrounded by whole tires in different
configurations. Tires were attached to each other using polyethylene rope and were
covered with geocomposite to protect the conduit’s integrity. Moreover, two lifts of waste
with a 6 m thickness were placed on top of the lines. Data was collected on an hourly
basis during leachate injection. Flow and water pressure were monitored.
Objective 2. Measure fluid conductance on horizontal injection lines constructed
with whole tires in different configurations
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Approach. Injection lines were constructed using three different tire
arrangements; length, pipe diameter and the use of geocomposite as protective media
were kept constant in all three configurations. Two lifts of waste were placed on top of
all the injection lines. All the lines were operated simultaneously. Flow and pressure
data were monitored on an hourly basis.
1.5 Organization of Thesis
This thesis is presented in five chapters. Chapter 1 presents introductory material,
problem statement, objectives, and research approach. Chapters 2 through 5 provide
the literature review, methods and materials, results and discussion and conclusions. A
literary review on liquids addition into landfills is presented in Chapter 2. Chapter 3 is a
description of the materials and methods used to plan, construct, operate and monitor
horizontal injection lines into bioreactor landfills. Chapter 4 presents a discussion of the
findings of this research as well as a comparison with other experiences on the
performance of horizontal injection lines using different bedding medias. Chapter 5
presents a comprehensive summary and conclusions together with a final
recommendation of this experiment. Cited references are included at the end.
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CHAPTER 2 LITERATURE REVIEW
This chapter contains a literary review on the fundamentals of bioreactor landfills
as well as a summary of bioreactor experiences in the New River Regional Landfill with
an emphasis on leachate recirculation research. Horizontal injection line experiments
using different bedding medias such as crushed glass and shredded tires are visited
and compared. An evaluation on fluid conductance development and its usage as a
hydraulic parameter on the evaluation of horizontal injection lines will be discussed.
Lastly the current tire disposal situation and their use as bedding material for injection
lines will be visited.
2.1 Bioreactor Landfill
Conventional sanitary landfill was developed as a method to store waste while
preventing the entrance of moisture in the unit. By using this approach, decomposition
rates are slower, leachate as well as landfill gas generation is minimized. In contrast to
traditional landfills, bioreactor landfills accelerate the decomposition of the
biodegradable faction of the waste by adding liquids in a controlled fashion. As moisture
accumulates and becomes more uniformly distributed with leachate recirculation, waste
stabilization in each compartment of a landfill bioreactor progresses through
decomposition phases (Pohland 1999). Leachate recirculation appears to be the most
effective method to increase moisture content in a controlled fashion (Reinhart 1995,
Pohland 1975). This practice provides leachate volume management and offers the
potential to accelerate the decomposition of biodegradable waste in a landfill
(Townsend and Miller 1998).
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2.2 New River Bioreactor Project
In an effort to increase knowledge on bioreactor landfills FDEP ( Florida
Department of Environmental Protection) provided funding to the Florida Center for
Solid and Hazardous Waste Management to conduct the demonstration of a full-scale
bioreactor landfill. New River Regional Landfill was chosen as the site to conduct the full
scale bioreactor project. During the project, exhaustive studies on liquids injection
systems were performed. The most relevant studies in terms of liquids recirculation in
this facility were performed by Jain (2005),Kadambala (2009) and more recently Singh
(2010). This paper’s research aims to build upon research conducted by Singh as both
used whole tires as bedding material in the construction of horizontal injection lines in
this facility. Listed below is a more detailed description of those projects and Chapter 3
offers a deeper description of the site. Table 2-1 presents research done in NRRL on
leachate injection systems.
Table 2-1. Research on liquid distribution systems developed in NRRL.
Author Date of
Construction Cell Configuration
Number of Lines
Dimensions
Operational Period
Amount of
Injected Leachate
(m3)
Length (m)
Diameter (inches)
Jain 2003 I and II
Vertical 134 3 2 17 months 17,700
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Kadambala 2006 IV Vertical 18 6 2 153 days 8,431
9
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2006 IV Vertical 2 12.2 2 122 days 1,422
Singh 2010 V Horizontal 4 15 3 16 days 365
30
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Jain (2005) installed 45 clusters of vertical wells during the spring of 2001 in cells
1 and 2. Each of the clusters consisted of three wells with approximate depths of 6, 12
and 18 meters. The depths were selected according to a survey data and the height of
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the bottom liner. Constant moisture addition was conducted for a 2.5 year period, at an
average rate of 6.5 m3/ day. Injection of liquids in wells at a greater pressure than the
depth of the well would result in seep. No advantages were found on the use of wells of
different length to homogenize liquids distribution. Shallow wells could not be operated
under higher pressure; however waste at that depth presented a higher hydraulic
conductivity. Flux in the three different depths was comparable as shallower depths had
higher conductivity and deeper wells could be operated under higher pressure. The
extent of moisture movement was estimated to range from 8 to 10 meters around the
injection clusters. Results showed that a single screened well would have been
sufficient for an even liquid distribution along the waste profile. A total of 17,700 m3 of
liquids, (leachate and groundwater) were added to the bioreactor.
Kadambala’s (2009) experiment in Cell IV consisted on six clusters of vertical
wells. Each one of the clusters had nine vertical wells with three lines of 6, 9 and 12
meters in depth respectively. This experiment was divided into two sections, with each
section containing three clusters. All the lines in a cluster were connected to a single
liquid distribution line. The experiment was monitored with thermocouples and vibrating
wire piezometers which were installed in the bottom of injection lines and used to
measure temperature and pressure respectively. The system was operated for a total of
153 days; during the first 103 days the system was operated 9 hours daily after which it
was operated continuously for 48 days. The regulatory agency set 121 m3 per day
(32,000 gallons) as the maximum amount of leachate to be injected in that cell,
consequently flow rates were kept bellow it, adding between 80 and 120 m3. A
cumulative volume of 8,431 m3 of liquid was injected. Leachate flow rate per unit screen
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length of the buried vertical well was the same or higher than the ones obtained by Jain
(2005). Monitoring of the leachate recirculation system was not necessary and the
ability to inject leachate in the buried vertical wells at a pressure higher than the screen
length of the well were the biggest advantages over vertical injection lines installed on
the landfill surface by Jain. The exposed advantages and the need of fewer leachate
conduction lines going inside of the landfill made this system more practical from an
operational perspective.
Another experiment by Kadambala (2009) during the summer of 2006 on Cell IV
consisted of two injection lines of 12.2 m deep at a distance of 7.6 m from each other.
All the lines in a cluster were connected to a single liquid distribution line, which in turn
was connected to the main liquid injection system. A total of 18 multi level piezometers
were installed around both of these injection lines. Each multi-level piezometer well had
five piezometers at three meter intervals in height, the deepest located at 15 and the
shallowest at 3 meters under the ground. The piezometers were connected to a data
logger to measure and record pore pressure and temperature spatially from the buried
vertical wells in the surrounding waste. A pressure transducer, pressure gauge, flow
meter and a globe valve were attached to both of the lateral leachate recirculation lines
on the west side slope of the cell. The experiment was operated intermittently for a 122
day period; it was operated Monday through Friday during operational hours of the
facility and later operated continuously for several days. As liquids were injected large
pressures developed in the bottom of the vertical injection wells, pressures were
significantly reduced in the surrounding waste. Pore water pressure in the surrounding
waste did not increase proportionally to the increment of hydrostatic head on the deeper
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sections of the well, presumably due to a lower permeability of the waste in this section
of the landfill. A significant reduction in the pore water pressure bellow the bottom of
the buried well compared to its counterpart on the bottom of the well was an indicator of
the anisotropic nature of the waste.
More recently, Singh (2010) conducted an experiment on surface infiltration lines,
this experiment was the first of two phases of the innovative tire recycling grant given to
NRRL. The experiment discussed in this paper is the second section of such grant.
Construction took place on the top of Cell V, which was being filled at that point in time.
Four lines were built: trenches number 1 and 2 had a length of 45 meters; while
trenches 3 and 4 were 30 and 15 meters long, respectively. Trenches were constructed
using an excavator, having 1 m by 1.2 m dimensions of height and width. Along the
side of the recently excavated trench whole scrap tires were positioned vertically. With
all tires positioned in the same fashion it was possible to pass 3 inch perforated HDPE
pipe through them. The tires were fastened together using a polyethylene rope and the
entire linkage was later pushed with tractors into the trench. Once in the trench, the
lines were covered with geotextile to prevent the migration of fines into the lines. Lines
were immediately covered with clay mined on site and later compacted using a road
roller. A solid section of 3” in diameter HDPE pipe was welded to each end of the
perforated liquid injection pipe and was extended to the top of the trench and out to the
surface. These solid sections of pipe were connected to a leachate recirculation hydrant
on one end and capped on the other end. A 3“ valve and a paddlewheel flow meter
(Sea Metrics IP80 ) were installed at the hydrant connection to control the flow rate and
to monitor flow rate at each trench. The water column was measured with a portable
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water level meter together with the flow rate, which was recorded on hourly basis. The
system was operated for 16 days, during June and July of 2010. The hydrostatic head
was always kept 0.3 m below the top surface of the landfill to avoid the seeps. As
expected the pressure increased in the early stages of liquids addition and it was kept
constant during the experiment. The sectional flux was higher in early stages and
decreased throughout the operation of the system. The performance of the infiltration
trenches was measured in terms fluid conductance (unit flux per unit pressure head),
which ranged from 8.9×10-6
m/s to 1.2×10-5 m/s. A total of 365 m3 of liquids were
injected during that stage of the project. The mentioned lines were connected to a
common header and then covered with two lifts of waste, each one of the lifts had a
thickness of approximate 6 meters. After waste was placed on top of the lines, these
lines were considered as a single line. Results of the operation of phase I are presented
as part of this paper.
2.3 Horizontal Liquids Addition System
Horizontal injection lines are the most common liquid addition methods in
bioreactor landfills operation. This method does not create offensive odors and has a
minimum interference with normal landfill operation and traffic. Also, horizontal injection
lines allow a better distribution of the liquids both vertically and horizontally than other
liquid distribution methods like infiltration ponds and spray irrigation. It allows better
control of liquid distribution at different depths within the landfill than does the use of
vertical wells, where moisture may not distribute along the entire well screen length due
to consolidation of MSW at lower depths. In addition horizontal injection lines can be
constructed as a landfill cell is actively accepting waste.
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2.4 Previous Leachate Injection Lines Experiences
Larson (2007) conducted research on fluid conductance values for 16 horizontal
injection lines using three different bedding medias monitored over a large range of
cumulative linear-injected volumes. Medias used were crushed glass, shredded tires
and municipal solid waste. Fluid conductance was defined as the flow rate per unit
length of HIL per unit of applied pressure head. Different applied flow rates were found
to have little to no influence over the fluid conductance of an injection line. Fluid
conductance on lines using shredded tire chips or lightly crushed glass as bedding
media were found to be comparable. At lower cumulative linear-injected volumes,
injection lines with bedding media had significantly higher fluid conductance values than
those without bedding media and HILs buried deeper within the landfill were found to
have significantly lower fluid conductance values than those buried less deep within the
landfill. The observation of this decreasing trend of fluid conductance was attributed
either to a decrease of the waste’s hydraulic conductivity due to landfill gas presence;
structural changes on the waste matrix due to degradation of the organic fraction of the
waste or clogging due to fines entering the injection lines. The performances of HILs
were reported on a range of 1.9×10-7 m/s to 7.5×10-7 m/s with an average of 5.3×10-7
m/s.
Kumar (2009) evaluated the fluid conductance values of 31 injection lines of
various bedding medias, length, and overburden depth of waste. These lines were
monitored over a large range of cumulative linear-injected volumes. This project was
developed on the same facility as Larson developed his research; all the parameters
measured were the same as in that project. In general, the HILs with bedding media
had higher fluid conductance values than those without bedding media. Fluid
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conductance values presented in this experiment range from 1.6×10-7 m/s to 3.4×10-6
m/s with an average of 7.8×10-7 m/s. Table 2-2 compares fluid conductance values
obtained on previous experiments using different bedding medias on three different
landfill sites.
Table 2-2. Fluid conductance values obtained on previous research. Author Year Facility No. of lines Material Average K (ft/s) Average K (m/s)
Townsend 1994 ACS 9 Shredded tires 1.46E-05 4.45E-06
2 MSW 3.12E-06 1.02E-05
Larson 2006 PCNCL 16 Shredded tires 4.15E-05 1.26E-05
Crushed glass 4.26E-05 1.30E-05
MSW 3.02E-05 9.20E-06
Kumar 2007 PCNCL 31 Shredded tires 3.32E-05 1.01E-05
Crushed glass 2.70E-05 8.23E-06
MSW 2.06E-05 6.27E-06
Cho 2010 PCNCL 15 Shredded tires 4.59E-05 1.40E-05
Crushed glass 2.57E-05 7.83E-06
Singh 2010 NRRL 4 Whole tires 1.72E-05 5.25E-06
(Townsend and Miller 1998; Larson 2007: Kumar 2009; Cho 2010; Singh 2010)
Benson et al. (2006) reviewed five bioreactor landfills across the nation, several
design and operational aspects were analyzed. Typical volume of leachate recirculated
into the landfill was one of the evaluated parameters. Figure 2-1 presents data reported
by Benson et al. on bioreactor landfills and it compares it with the amount of liters
recirculated per square meter of area of cell V.
2.5 Fluid Conductance
The term of fluid conductance was formulated by Townsend and Miller (1998) as
an effort to evaluate horizontal injection line performance for their flow-pressure
relationships (denoted as κ). This term is a flow-to-pressure ratio normalized by the
length of the injection line and is meant to help design engineers better understand the
amount of flow per applied pressure that these types of systems can achieve.
Townsend and Miller (1998) did not coin the term; it was simply derived from analogous
electrical flow terms where flow and pressure are analogous to current and voltage.
27
According to Ohm’s law, the current-to-voltage ratio is equal to the inverse of the
resistance; this is the conductance. Physically, the fluid conductance is the amount of
flow able to be injected per unit of applied pressure head per 1-foot section of HIL
trench (Larson, 2007).
Landfill ID
S D Q C E
Leachate
volu
me r
ecircula
ted p
er
year
(L/m
2)
0
20
40
60
80
100
120
140
160
180
Figure 2-1. Typical leachate recirculation rates (Lm-2) in several bioreactor landfills
(Benson et al. 2006)
Fluid conductance is denoted as κ with units of m3min-1m-1 per meter (water
column) and is a flow to pressure ratio normalized by the length of the injection line.
This parameter sets the pressure head occurring at the inlet of the injection trench as
the defining pressure, and is described in Figure 2-2.
Where Q = flow rate, [L3T-1]; L = length of a horizontal pipe, [L]; and Hp =
injection pressure head at the inlet of the HIL, [L] (Townsend and Miller 1998). By using
fluid conductance one can compare different aspects such as bedding media,
configuration and length of horizontal lines. Fluid conductance will be used to evaluate
28
whole tires as an alternative media and compare it with previously used materials,
namely crushed glass and shredded tires.
Figure 2-2. Landfill injection line diagram to illustrate fluid conductance measurement
and equation
2.6 Tires Reuse and Disposal
According to the Rubber Manufactures Association, during 2003 approximately
290 million tires were produced nationwide. The EPA calculates that there is market for
80% of the scrap tires produced and the remaining tires are being stockpiled or in very
few states landfilled. Scrap tires that are processed are either recycled or employed for
a beneficial use outlined below:
Table 2-3. Different uses for recycled tires
Amount (millions)
Percentage
Fuel 130 45 Civil Engineering 56 19 Asphalt 12 4 Exported 9 3 Punched products 6.5 2 Agriculture 3 2 Retreaded 16.1 7 Ground rubber 18 8 Total 250 100
It is also worth mentioning that the amount of pilled tires have diminish significantly
from more than 900 million in 1990 to 300 million in 2003.
Q
Q
ℓ*hℓ Ƙ =
h
29
Tires are believed to cause uneven settlement in landfills. In order to minimize
these problems some states require tires to be shredded prior to disposal.
The use of monofills for the disposal of whole tires has become more common.
These landfills are used where there is a lack of markets for scrap tires. States like
Alabama allows the disposal of whole tires in class I landfills.
The disposal of whole tires in Class I landfills is prohibited under the Florida
Administrative Code section 62-701, hence whole tires have not been used as bedding
material for horizontal injection lines. This ban originated during the perceived landfill
capacity shortage at the time on which such regulation was implemented. Also the
common observation that tires tend to rise to the surface of the landfill was in part the
reason for the mentioned ban. Alternate materials such as gravel, shredded tires,
crushed glass among others have been used as bedding materials in previous research
efforts.
30
CHAPTER 3 METHODS AND MATERIALS
3.1 Site Description
The experiment on horizontal injection lines being discussed in this paper was built
on top of Cell V of the New River Regional Landfill. This facility is located in Union
County, Florida. At the time on which the experiment took place, NRRL received
approximately 800 tons of MSW daily. The landfill consist of six contiguous lined class I
landfill cells, Cells 4 and 5 have an area of 7.8 and 6.9 hectares respectively. Florida
DEP allowed NRRL to inject liquids in the landfill, at a daily rate of 122 m3 on Cell V.
The density of the landfilled waste is 710 kg/m3 (Jain, 2005).
3.2 Innovative Recycling Grant Development and Permit
Use of horizontal injection lines as a method for liquids distribution is customary
practice in bioreactor landfills. This technique typically involves excavating a trench in
the waste, placing a perforated pipe surrounded by a bedding media, and covering the
trench with soil. The most common bedding material used in Florida is shredded tires,
the use of other bedding medias such as crushed glass, mulch, and excavated waste
has also been have been explored. Although shredded tires are widely used there are
some concerns regarding reduction of hydraulic conductivity over time. Using whole
tires presents several advantages over shredded tires. The use of whole tires as
bedding media for horizontal injection lines would eliminate concerns regarding
hydraulic conductivity. No shredding process is required, which saves costs and
emissions. Whole tires are readily available throughout the State, and handling of tires
is simpler then dealing with a bulk material. Tire geometry also allows building injection
lines on the landfill’s surface in contrast with bulk materials that need to be placed in
31
trenches and later covered. As later described on this paper, construction of injection
lines using whole tires does not requires trench construction.
With the aim to increase recycling rates the Florida Legislature instructed the
Florida Department of Environmental Protection (DEP) in 1997 to institute a competitive
grant that would fund counties to develop innovative recycling programs. In 2007 New
River Landfill received the grant to conduct research on an innovative technique to
reuse whole tires in landfill applications. Later, New River applied for a Research
Development and Demonstration (RD&D) permit to be allowed to place tires
permanently in its landfill. After several iterations (requests for additional information)
the permit was given on May 2010 by Florida DEP.
For the proposed study, whole tires were used in place of traditional bedding
media. Whole tires maintained open spaces around the perforated pipe, which allowed
migration of liquids during injection. Three configurations of tire placement were used
on this project. These types of configuration vary in the laying of the tire. In Type A
configuration tires were placed vertically and the liquids injection line went through the
center of the tire. In Types B and C tires were laid horizontally in layers and the liquids
injection line was placed in between two layers.
3.3 Surface Infiltration Lines Experiment
The research project carried out by Singh (2010), together with the project
discussed on this paper, was part of the innovative recycling grant given by the FDEP to
conduct a RD&D project in New River landfill. The first phase, performed by Sigh,
evaluated the performance of superficial infiltration trenches constructed with whole
tires. Four trenches with lengths 15 m, 30 m, and two at 45 m in length were installed
using tires as bedding media. Lines were installed in the surface of the third lift of cell V
32
in late May 2010.The tire layout of this cell was configuration A, which is explained later
in the chapter. Injection lines were assembled on the surface of the landfill, afterward a
1.2 m deep trench was excavated adjacent to the lines, with the mentioned lengths.
Injection lines were pushed into the trenches with the use of landfill equipment. After
that injection lines were covered with a layer of geocomposite, later a 0.3 m layer of
clay was placed and compacted. Injection trenches were operated for a 16 day period.
Performance was measured in terms of fluid conductance, results ranges from 8.9 x10-
6 to 1.2 x10-5 m/s. Following operation as surface infiltration lines the four lines were
connected to a common 3” HDPE conduction pipeline. After which it was considered a
single injection line with a length of 135m. Phase I was covered with waste and
operated for a 15 month period.
3.4 Horizontal Injection Lines Location
The area in which the injection lines were constructed is located 14.5 meters
above the landfill liner. During the experiment’s duration the lines were covered with
two lifts of waste, each one with an average thickness of 6 meters. An onsite mined
clayey-sand is used as daily cover. Waste on Cell V was placed on a series of five lifts,
the experiment was constructed on top of the third lift, later two lifts were placed on top
of the injection lines. The first three lifts of waste were placed using an east-west
fashion while the remaining lifts were placed using a south-north fashion. This was
done in order to ease the construction of the injection lines. Instrumentation and
controls were on top of the fifth lift of a contiguous fully constructed cell. Figure 3-1
depicts the location of the experiment and the waste placement process.
Cell V was chosen to construct the horizontal injection lines, as that was the active
cell in the landfill. At that point , each line was covered in within a month.
33
Figure 3-1. Cross section of Cell V, New River Regional Landfill
34
3.5 Leachate Recirculation System Construction
The construction of horizontal injection lines began in May 2010 on top of the third
lift of Cell V. Phase I was constructed and operated during May and June of that year.
After being operated phase I lines were clustered and covered with two lifts of waste.
Lines I through IV of phase II were constructed from August to December of the
mentioned year. Lines were constructed obeying the waste placement pattern, which
was on a north-south direction. Landfill operators modified the working face width to be
15 meters and 6 meters in height in order to cover the HIL’s as they were being
constructed. Since the distance between each HIL was 15 meters, researchers had a
window of time to construct the next line as the previous was being covered with waste.
35
Table 3-1. Timeline of tire project experiment in NRRL. 2010 2011 2012
May
Jun
.
Jul.
Au
g.
Sep
t.
Oct
.
No
v.
Dec
.
Jan
Feb
Mar
Ap
r
May
Jun
Jul
Au
g
Sep
Oct
No
v
Dec
Jan
Feb
Phase I
Construction
Tran
sdu
cer
inst
alla
tio
n
Waste placement
Operation
Analyzed data
Ph
ase
II
Line I
Construction
Waste placement
Operation
Analyzed data
Line II
Construction
Waste placement
Operation
Analyzed data
Line III
Construction
Waste placement
Operation
Analyzed data
Line IV
Construction
Waste placement
Operation
Analyzed data
Line V
Construction
Waste placement
Operation
Analyzed data
36
Leachate injection lines were connected to the main liquid recirculation pipeline
which ran along the eastern outer landfill berm to the leachate aeration basins. Each
injection line was valved separately, which allowed to control one independently.
Figure 3-2. Plan View NRRL with injection lines and infrastructure.
All the lines had a butterfly valve (Asahi, USA) and were connected to a
paddlewheel flow meter (IP80 Seametrics, Washington USA), a gas release
mechanism, and a pressure transducer. Data loggers recorded data from the pressure
transducers. Since the valves and monitoring equipment were located at a higher point,
(Figure 3-2) a 80 m solid section of pipe was extended down the side slope of Cell IV to
the surface of Cell V, where the injection lines were constructed.
Five HIL’s had a length of 91 meters and phase I was considered a single line with
a length of 135m.
37
Each one of the lines was constructed using previously perforated HDPE with 3” in
diameter and a fusion welder was used to add the pipe segments. Injection lines were
constructed using three different tire configurations.
3.5.1 Configuration A
As it can be appreciated on Figure 3-3 configuration A consisted of standing tires
with pipe running through the center of them. To construct lines with this configuration,
tires were unloaded from roll off boxes on several points along the length of the future
line. Immediately after that tires were attached between each other with polyethylene
rope in groups of around ten. The last tire on each group was attached to the next group
of tires in an effort to increase the structure’s cohesion. HDPE pipe would be introduced
into the conduit as it was being constructed. For practical purposes pieces of pipe with a
length of 15 m were welded to the end of the pipe as it was being introduced inside of
the tires.
Figure 3-3. Configuration A horizontal injection line being built on top of Cell V of NRRL. (Picture taken by author.)
38
3.5.2 Configuration B
A 91 meter long HDPE pipe line was placed along the side where the injection line
was going to be constructed. Tires were placed horizontally and later attached between
each other with rope, later a second layer of tires was placed on top .Tires were placed
on brick pattern as an effort to add strength to the structure. Figure 3-4 depicts this
configuration. After two layers of tires were placed and securely attached, the pipe was
placed on top of those tires. Later a second set of two layers of tires were placed and
attached on top. This configuration proved to be relatively easy in terms of tire placing,
however attaching the tires became time consuming as rope had to be cut in 0.60 meter
sections and use to attach two tires at a time. Layers were also attached between each
other.
Figure 3-4. Configuration B, under construction, injection line can be appreciated on top of the first two layers of tires. (Picture taken by author.)
3.5.3 Configuration C
Configuration C construction was similar to Configuration B with the only variance
that it was composed of two rows. This configuration was the most labor intensive of the
three because of the amount of attachments needed. Nevertheless, from a structural
39
perspective it had a width-to-height ratio of 2, which added stability, compared with
Configuration B with a ratio of 1. Also, this configuration was not displaced during waste
placement unlike the other configurations. The lines of Configuration A were slightly
displaced as they went under horizontal stress while waste was being placed on top of
them (Figure 3-5).
Figure 3-5. Configuration C. Line III of Phase II as it was being constructed. (Picture taken by author.)
During construction, loads of tires were transported in a 40 cubic yard container,
each of these containers had around 250 tires. Tires were selected and the ones that
didn’t have the required size or integrity were put back in the container and later hauled
to a tire disposal facility. Most tires were in good condition and only a small portion of
them were returned. Around 4,000 tires were used to construct the horizontal injection
lines. Tire diameter ranged from 0.5 to 1 meter, only tires that comply with these
requisites were used to ensure structural strength of the injection lines. All the tires were
attached between each other using stranded polyethylene rope. After each line was
40
constructed, a 3.2 m wide geocomposite layer was used to cover the lines in order to
prevent the intrusion of fines.
Figure 3-6. Injection line with the geocomposite installed. (Picture taken by author.)
As earlier mentioned injection lines were constructed on top of Cell’s V third lift;
located 15 meters above the liner. The forth lift of waste was placed on top of the
injection lines from August to December 2010. An additional lift of waste was placed
from January to December of 2011. Each one of the lifts was 6 meters thick. Figure 3-6
portrays the construction process. The valve cluster together with the monitoring
equipment was installed on top of a contiguous fully constructed cell, as cell V was
under construction at that point
3.6 Waste Placement Above Injection Lines
Injection lines were installed on the surface of an active cell, later, two lifts of
waste were placed on top of them. To protect the integrity of the injection lines, these
41
were constructed adjacent to the toe of the lift, thus it was possible to push waste from a
higher point and pile it on top of the lines without machinery interference. Waste was
piled on top of the lines until the thickness of the waste reached about 2 meters,
thereupon waste was compacted as routinely. It has to be noticed that the coverage of
Line I was more elaborated than the other lines since that line was not located on the
toe of the slope as were all the other lines. Figure 3-7 shows how lines were covered
with a thick layer of waste before running heavy landfill equipment over them.
Figure 3-7. Injection lines being covered with waste. (Picture taken by author.)
Injection Lines Integrity Testing. With the intent of testing the integrity of the
injection lines a 3/4” diameter pipe was introduced to the injection lines. This line was
170 meters long as this was the cumulative length of the solid and perforated sections
of the injection pipeline. Lines were tested on January 2011, no line presented
obstructions. However, later in the year, two lines were detected to be obstructed
making any further operation of those lines impossible.
3.7 System Operation and Monitoring
Injection lines were constructed in a six month span. Even when some of the lines
were constructed and covered with waste, operation was irregular due to time
42
constraints derived from the construction of other injection lines. On January 2011, after
construction was finalized, all the lines were operating. Injection was carried out on
weekdays during landfill operational hours. At this stage water level inside of the
injection lines did not raise to the surface which made impossible to determine fluid
conductance values as water table was an unknown.
Leachate flow and water level, when visible, were recorded manually on hourly
basis. Flow was monitored with a digital flow meter (IP80 Seametrics). Water pressure
was measured whenever it was visible, as it rose above ground level and migrated into
gas relieve devices made of clear piping. This allowed to record data for a narrow
period only, making impossible to appreciate increases on the water level, thus there
was a big gap of information missing.
In order to increase accuracy and to be able to monitor the system during the
whole injection process, pressure transducers (PDCR 1230, Campbell Scientific) were
installed inside of the injection lines. A data logger (CR10X, Campbell Scientific)
received analog signals every 30 seconds. Datalogger recorded the average of the
readings taken every 30 seconds, over a five minute period.. Data was downloaded
using a portable computer.
Due to the inhability to consistently record water level inside of the injection lines
on every injection run data produced before installation of the transducers was not
analyzed in this paper. Pressure transducers were encased on ¾” PVC lines, as a way
to protect the line and ease the introduction of the transducer on the injection line.
Figure 3-8 depicts the instrumentation setup for this experiment.
43
Figure 3-8. Monitoring setup for the horizontal injection lines.
Pressure Transducers Installation. Pressure transducers were used to
measure the water column inside of the injection line. Previously acquired transducers
were inserted 20 meters inside of the injection line (Figure 3-9). A settlement profiler
(Geokon, New Hampshire) was inserted inside each injection line to assess at what
height the transducer was located. The height of the injection line was known, thus
water level inside of the injection line was determined by adding the difference in height
between the injection line and the location of the transducer plus the water column
registered by the transducer. To secure the physical integrity and to ease the insertion
44
of the transducers in the injection lines, transducers were inserted into perforated
¾” PVC pipe.
Figure 3-9. Pressure transducer inserted and attached into horizontal injection lines.
3.8 Experiments
From January 7 to February 19 injection of liquids was carried out for 20 days. A
first intent to inject leachate for 24 hours continuously was made, however it required
continuous monitoring which proved to be unpractical. Injection was reschedule to be
performed during weekdays for five hours daily.
Table 3-2. Timeline detailing different stages of tire project. Aug-Dec 2010
Jan-Nov 2011
Dec- 11
Jan-Feb 2012/ Days of Operation
Construction and
preliminary
injection
Injection
without
pressure
transducer
Pressure
transducer installation
7-J
an
8-J
an
10-J
an
12-J
an
12-J
an
25-J
an
26-J
an
27-J
an
28-J
an
29-J
an
1-F
eb
2-F
eb
3-F
eb
6-F
eb
7-F
eb
8-F
eb
9-F
eb
10-F
eb
16-F
eb
18-F
eb
The amount of hours of operation was determined on several iterations, being five
hours the amount of time on which water level in most of the lines would rise close to
the surface. Leachate was pumped to the lines at 0.18 m3 (74 gal.) per minute rate.
Flow would experience slight decreases as a product of increments on the water level
CELL V CELL IV
Injection line
Pressure tranduce
45
inside of the injection lines. Water level average was recorded every five minutes by the
datalogger, while leachate flow was recorded manually on hourly basis. Within every
renewed injection run, fluid conductance values rebounded and later decreased to a
lower amount than previously reached for the same volume of leachate previously
injected. Water level did not recede below 6.9 meters during the experiment, even after
several days without liquids injection. Every injection run, the change in water level
during injection decreased as the initial water level increased continuously during the
experiment period. Although there was a continuous increase on the initial water level,
final water level remained constant throughout the experiment.
3.9 Injection Schedule
Injection lines were constructed over a seven month period (May-December,
2010). Singh 2010, constructed four surface infiltration lines that were operated during a
two month period, these lines were covered with two lifts of waste, this experiment was
analyzed as a single injection line on this paper. From July to December 2010 five
injection lines were constructed. Operation of the lines was started as they were being
covered with waste. Some exploratory injection was conducted during the construction
period however it was irregular due to time constraints. On December 2011 pressure
transducers were introduced inside of the line in pursuance of measuring water level in
the lines in a more accurate way. Data presented on this paper was compiled after the
pressure transducers were installed inside of the four injection lines being analyzed.
Line Recovery. A hydraulic spreader jaw, connected to a hydraulic pump through
high pressure hoses was introduced inside of the injection line. Hoses were inserted on
a ¾” PVC pipeline as a way to add sturdiness and to ease the introduction of the jaw
through the line. When the jaw reached the obstruction point it was pumped until it
46
reached 10 000 PSI, as that was the maximum pressure such equipment was designed
for. In both cases it was not possible to clear the obstruction. Differential settlement was
attributed as the reason for line III to be obstructed, since waste was placed over the
line several months before the obstruction’s occurrence.
Line II was found to be obstructed close to the surface; it is believed that the line was
crushed by landfill machinery.
47
CHAPTER 4 RESULTS AND DISCUSSION
4.1 Construction and Operational Observations
Construction of the injection lines was carried out by the researcher with landfill
personnel assistance. A 3” HDPE leachate conduction pipeline 80m in length was
constructed and laid on the side slope of cell IV for each of the injection lines. These
leachate conduction lines were not buried, which later became an operational issue.
Before starting construction, a thick layer of diesel contaminated soil had to be removed
from the surface of the landfill in order to avoid short circuiting of liquids through that
media. This media was present only where line I was later constructed; cover soil
underneath the later constructed lines was not removed. Table 4-1 provides a
description of the amount of work (man-hours) and tires required to build each line.
Table 4-1. Labor and amount of tires used on the construction of injection lines.
Configuration Date of
Construction Length
(m) Number of
Tires Man-hours
Tires/m Man-
hour/m
Phase I A May-10 135 900 64 6 0.5 Line II A Oct-10 90 600 32 6 0.4 Line IV A Nov-10 90 600 32 6 0.4 Line V A Dec-10 90 600 32 6 0.4 Line I B Sep-10 90 600 96 6 1.1 Line III C Oct-10 90 1200 128 12 1.4
Totals 585 4500 384
Tires were transported from surrounding counties on a daily basis and discharged at
several points along the injection line construction site.
Configuration A was the most widely used as it was used to construct four out of
six lines (Phase I, Line I, IV, and V). Phase I was constructed on the surface of the
landfill (Figure 4-1), and later pushed by landfill machinery inside of the constructed
48
trench. This procedure would not have been possible with any of the other
configurations.
Figure 4-1. Injection line being pushed inside of the trench during Phase I construction. (Picture taken by author.)
Later in the year, as lines from phase II of the project were being constructed, the
previously mentioned layer of soil was removed in order to construct line I. Rainy
weather prevailed during soil removal and construction of line I which delayed the
construction process. Figure 4-2 illustrates how the soil was removed; this area had no
drainage. Storm water pooled in the area where line I was being constructed; the tires
also contained water. These issues made the attachment of the tires more difficult
resulting in a more labor intensive process.
Figure 4-2. Cover soil being removed from the surface of Cell V for line I construction. (Picture taken by author.)
49
Construction of the remaining lines was dictated by tire availability and the pace of
waste placement. Line II was constructed using configuration A, which was the least
time consuming design; construction of this line took one day for a crew of eight
workers. The construction of Line III was delayed for one week as it required a larger
number of tires, almost 1,500, including defective tires. This line was constructed as
tires were transported to the site. The act of tying the tires between each other was the
most difficult and time consuming process of this line’s construction. The line was
constructed over levelled waste in contrast to uneven waste in the case of line I. Table
4-2 presents disadvantages associated with construction of the different lines.
Configurations B and C were the most labor intensive due to the amount of knots
needed to attach tires within the lines. Furthermore, the amount of tires required for
these configurations was higher than the amount of tires needed for configuration A.
Later in the construction process, a class III landfill adjacent to the class I landfill
was being mined and the waste was subsequently placed on cell V. Thus there was a
significant increase in the rate of waste placement compared to what was previously
experienced in the project. Constructing a duplicate set of the three configurations (A, B
and C) became impossible due to time constraints. It was decided to construct the last
two lines following configuration A, as this configuration was the least labor intensive of
the three.
A total of 4,500 tires were used to construct 585 m (1950 ft) of injection lines. After
the lines were constructed, a geocomposite layer 3.6 m wide was placed and attached
around injection lines as an effort to prevent fines from migrating into the line and to
ensure cohesion of the structure. The placement of this protective media was crucial to
50
preserve the integrity of the injection lines as they were under stress from the waste
being placed on top of them.
Table 4-2. Issues associated with the construction of different tire configurations for horizontal lines.
Construction Waste Placement
Phase I, Line I, IV and V (Conf.A)
HDPE Pipe introduced through the tires. Lines were displaced as waste was placed around them. Assembly of HDPE pipeline during
construction of the injection line.
Lines II and III (Conf.B and C)
Structure affected by soil irregularities. Tying tires was difficult as they were laid horizontally.
During January 2011, after all the lines were fully constructed, a ¾” PVC pipe line
was introduced inside the injection lines. This was done to assess the structural integrity
of the individual lines. If the lines were damaged, the PVC pipe would not go through
the injection lines. No signs of damage were found at that time.
Compactor operators were instructed to place waste over the lines from a higher
point in the landfill and to be observant of the amount of waste placed above the lines
before operating equipment on top of them. In order to avoid seeps, a minimum
distance of 50 m between the injection lines and the side slopes was established.
Placing monitoring equipment and controls on top of cell IV rather than on the
side slope was instrumental to the release of gas pressure from the injection lines. The
pressure inside the lines was therefore not influenced by landfill gas and is believed to
be primarily driven by the water level inside of the lines.
4.2 Total Volume Added
Leachate was injected into the lines during all stages of the project (May 2010 to
February 2012). From May to July 2010, Phase I lines were operated independently as
surface infiltration trenches; during this period 365 m3 of leachate was injected.
51
From September 2010 to November 2011, as phase I was covered with waste and
the other five injection lines were constructed and operated; 8,800 m3 of leachate was
added to the landfill. Flow data generated during this period was collected manually and
water column data was only possible to obtain during peaks when the water level inside
of the line was high enough to migrate into the gas relief devices where it was observed
and recorded. Hence, data collected during this time was found to be inaccurate and
could not be added to this paper. Due to the large gaps in collected water pressure
data, it was decided to install pressure transducers in the lines whereby data could be
recorded and collected. Transducers were installed in early December 2011. The
system was then operated for a total of 20 days from January to February 2012 during
which 1,600 m3 of leachate was injected. Only data from those 20 operational days of
the project is being reported in this paper. Table 4-3 presents the total amount of
leachate injected into the lines during each stage of this experiment.
Table 4-3. Hours of operation and injected volume on each operational section of the tires project.
Phase I (May-July 2010)
Early operation (Sep 2010-Nov 2011)
Experiment Stage (Jan-Feb 2012)
Total
HIL
Hours of Operation
Volume Injected
(m3)
Hours of Operation
Volume Injected
(m3)
Hours of Operation
Volume Injected
(m3)
Hours of Operation
Volume Injected
(m3)
Phase I 58 365 445 1587 106 444 609 2397 Line I 562 1353 105 271 667 1624 Line II 318 663 -- -- 318 663 Line III 303 1516 -- -- 303 1516 Line IV 511 1894 106 387 617 2280 Line V 443 1606 106 465 549 2071 Total 58 365 2582 8618 424 1567 3064 10551
4.3 Individual Line Performance
As previously explained, injection lines II and III were operated for six months only.
For this reason the total amount of leachate injected into those lines is substantially
lower than most of the other lines. Table 4-4 presents values based on the amount of
52
hours of operation for each line and its respective linear flow. These parameters allow
for a comparison between all the injection lines during the early stages of the project.
Table 4-4. Main highlights of horizontal injection lines individual performance
HIL Start
injection
Status on February
2012
Total hours of injection
Total volume injected
(m3)
Flow rate (m
3min
-1)
Flow rate (gal min
-1)
Average linear flow
rate (m3min
m-1
)
Phase I 27-May-10 Working 603 2359 0.07 17 5E-04
Line I 30-Sep-10 Working 662 1620 0.05 12 5E-04
Line II 15-Oct-10 Obstructed 318 663 0.03 9 4E-04
Line III 11-Nov-10 Obstructed 303 1504 0.08 22 9E-04
Line IV 23-Nov-10 Working 612 2280 0.06 16 7E-04
Line V 14-Dec-12 Working 544 2060 0.06 16 7E-04
Total 3042 10486
Phase I was operated for an extended period. It was operated as a horizontal
infiltration trench for two months and later for another 17 months as a horizontal
injection line. This line received the largest amount of leachate (2359 m3); however it
was a cluster of lines that totalled 135 m in length. Thus, the average linear flow rate
5x10-4 m3min-1 m-1) was lower compared to other injection lines. The integrity of Phase I
was not assessed. However since it was covered with a layer of soil before waste was
placed on top of it, integrity of the line was assumed.
Line I had a consistent low flow rate throughout the experiment 0.05 m3min-1 (12
galmin-1). Even though this line had the greatest amount of operational hours, the total
volume of leachate injected into the landfill was the second lowest in the experiment. In
comparison, Line III was operated for six months only and had almost as much volume
as Line I in a third of the operational period. Although the line integrity of Line I was
tested, it was probably exposed to more stress from the compactors since it was
constructed above ground and was not located at the toe of the slope. Also, the width-
53
to-height ratio was approximately 1, which makes the structure less stable than the
other configurations.
Line II consistently presented the lowest flow rate among all the lines in the
experiment; 0.03 m3min-1 (9 galmin-1). Even in the early stages its performance was
substantially lower than lines IV and V which had an average linear flow rate of 0.06
m3min-1 (16 galmin-1) throughout the experiment. The possibility of low flow in Line II
due to settlement or decomposition of the surrounding waste was discarded. Gas
pressure was also discarded as a reason for such a low flow rate. It is believed that an
obstruction occurred while the line was still being operated. This assumption was based
on the fact that several other lines with configuration A (Lines IV and V) were operated
for many more hours at higher flow rates. Line II was eventually found to be obstructed
(i.e. no flow was achieved) on May 2010. As discussed earlier a hydraulic jaw was
introduced inside the line as an effort to clear the obstruction but the procedure was not
successful. A total of 662 m3 was injected into this line. No fluid conductance value was
obtained from this line.
Line III was the only injection line constructed following configuration C. This line’s
performance was remarkably higher than the other configurations as shown in Table 4-
4. The use of this configuration allowed the disposal of the largest amount of tires per
linear meter. During only 303 hours of operation, 1504 m3 of leachate was injected into
this line. This line had an average flow rate of 0.08 m3 min-1; while the average of the
rest of lines’ flow rates were 0.05 m3 min-1. Tires used in this design were laid
horizontally and pipe was surrounded by tires, unlike configuration B in which the pipe
was placed in-between layers. It is believed that the larger amount of tires cushioned
54
the stress created by waste overburden. Line III was obstructed in the solid pipe section
at a 60 m distance from the valve. That section of the pipe was located at the top of Cell
V’s surface, a considerable distance from any possible landfill equipment damage. The
collapsing of line III was attributed to waste settlement. No fluid conductance value was
obtained from this line. Lines IV and V presented an average flow rate of 0.06 m3min-1.
In both cases average flow remained consistent for the duration of the experiment.
4.4 Measurement of Fluid Conductance
Fluid conductance values were obtained by measuring injection pressure and flow
on four horizontal injection lines in NRRL for 20 operational days during January and
February 2012. Previous research efforts have found landfill gas pressure as an
obstacle for leachate injection. Townsend (1998) observed a decrease in fluid
conductance values over time as a general trend for all injection lines. Landfill gas back
pressure was thought to be responsible for this reduction in fluid conductance values. At
times, gas pressures as high as 5.0 m (water column) were recorded after injection.
Kadambala (2009) experienced uneven liquid distribution in a previously discussed
experiment on clustered vertical injection wells. This heterogeneity of liquid distribution
was attributed to increases in landfill gas back pressure on lines located further inside of
the landfill.
Gas Relief Devices. During construction and early injection stages, it was noticed
that flow in newly constructed injection lines would peak for around two months and
then decline. Such decreases in flows were due to the back pressure created by landfill
gas generated in the injection lines. As liquids were being injected, they would displace
gas and consequentially pressure would rise in the lines, preventing higher volumes of
leachate to flow through the waste.
55
With the intent to prevent gas from disrupting the injection process, gas relief
devices (Figure 4-3) were installed on each line. Such device consisted of a 0.75 m
clear pipe (2” in diameter) vertically mounted on a wooden stake. The base was
connected to a barb hose installed on the injection line through a (¼”) clear hose and
the top was open to the atmosphere.
Figure 4-3. Landfill gas relief devices installed on the solid pipe section of horizontal injection lines. (Picture taken by author.)
By using these devices, gas pressure was successfully released from the injection
lines. These devices prevented the pressure transducers from collecting data on
atmospheric pressure and allowed the collection of water pressure data only.
Furthermore, the gas relief devices prevented unwanted pressure buildup inside the
landfill.
To ensure the functionality of the devices, two injection scenarios were compared:
injection under vented and injection under non-vented conditions. This experiment was
performed in February 2012.
56
Line IV was operated under non-vented conditions for five hours. This line’s initial
pressure of 12 PSI was due to standing water inside of the line. In less than 15 minutes
of operation, pressure increased to 18 PSI while a negligible amount of leachate was
injected into the line. This rise in pressure was attributed solely to an increase in the
landfill gas pressure. Figure 4-4 shows a contrast between typical pressure observed
during normal injection conditions and under non-vented conditions. Flow of leachate
during both scenarios is also compared. Pressure under vented conditions increased
significantly at the beginning of the injection process and increased steadily until a
plateau was reached. On the other hand, pressure under non-vented conditions,
increased drastically to a point where liquids were not allowed into the line. The
pressure then gradually decreased with time. Cumulative flow into the line under non-
vented conditions was 7x10-2 m3 (20 gal), while the same line under vented conditions
received 17.7m3 (4670 gal) over the five hour period.
Injection Lines Operation. Injection of liquids was performed for five hours per
day during a 20 day period. Cumulatively the system was operated for 118.8 hours with
an average of 5.9 hours per day. Leachate was injected at a 0.25 m3/min (64 gal/min)
flow rate. Table 4-5 presents average injection flows and applied pressure throughout
the experiment.
Behavior of the water level followed the same trend in all the evaluated lines. As
can be seen in Figure 4-5 water level inside of the lines would experience a 3 m
increase on average during injection. A steady increase was maintained for 3 hours.
The water level would then plateau for the last hour. As expected, water level in lines
that were operated for longer periods reached higher levels.
57
Time in the day (hours)
9:00 11:00 13:00 15:00 17:00
Pre
ssu
re (
PS
I)
12
13
14
15
16
17
18
19
Flo
w (
m3/m
in)
0.00
0.02
0.04
0.06
0.08
Pressure Non-Vented
Pressure Vented
Flow non-vented
Flow Vented
Figure 4-4. Pressure and flow into horizontal injection line under two different venting scenarios.
Table 4-5. Average flows and applied pressure.
HIL Average Flow rate
(m3/min) Linear flow rate (10-
3m3min-1m-1) Average water
column (m) Average K
(m/s)
Phase I 0.07 0.5 12.3 6.50E-07 Line I 0.04 0.5 11.4 6.60E-07 Line IV 0.06 0.7 10.4 1.10E-06 Line V 0.06 0.7 10.6 1.10E-06
In general, final water levels were stable during the course of the experiment
(Figure 4-6). This occurred independently of the amount of hours operated or the rest
period of the injection line.
With each injection run, fluid conductance values peaked briefly before the water
level rose inside the lines. Afterwards, fluid conductance values decreased
proportionally to the rapid increase of the water level inside of the injection line.
58
Figure 4-5. Typical water level behavior during leachate injection (Feb 1st, 2012).
Date
1/9 1/16 1/23 1/30 2/6 2/13 2/20
Wa
ter
colu
mn
(m
)
7
8
9
10
11
12
13
14
Line I
Figure 4-6. Typical water level inside injection lines during experiment (Line I).
Each time injection was renewed, the initial water level would be at a higher point than
the previous run. Thus fluid conductance values progressively decreased during the
59
course of the experiment. Table 4-6 shows initial and final fluid conductance values
from an early injection event (Jan 7th) contrasted with one of the final events (Feb 16th).
There is an order of magnitude of absolute difference between initial and final fluid
conductance values from these two events.
Table 4-6. Fluid conductance (m/s) fluctuation during injection, contrast of early and later injection events.
K (m/s) 7-Jan 16-Feb
Initial 5.8E-05 6.0 E-05 Final 4.4E-05 6.2E-05 Difference 1.4E-05 1.4E-06
Fluid conductance results obtained in this paper follow the same trend of
previously reported experiments. Larson (2007) observed high initial fluid conductance
values followed by slight decreases with time. Peaks in fluid conductance values are
due to a lower initial water level which, at equal flow, generated higher values.
Landfill gas back pressure did not affect flow, as gas was evacuated from the
lines. Flow values had slight variations during injection of liquids, and changes in fluid
conductance were primarily driven by water pressure.
Fluid conductance values were higher in injection lines IV and V compared with
Phase I and Line I. It is believed that lines IV and V performed better as they were
constructed later in the project. For instance, line V was constructed six months after
phase I. Line performances tend to decrease as waste surrounding them is in a more
advanced state of decomposition, hence void spaces are limited.
Lines IV and V presented the highest fluid conductance values, 1.1 x10-6 m/s on
average, throughout the experiment.
Fluid conductance values in this research were similar to the ones obtained in
previous experiments (Figure 4-11) on PCNCL (Larson 2007, Kumar 2009 and Cho
60
2010) and more recently by Singh (2010) at NRRL. However it must be noted that there
are several fundamental differences between those experiments and the experiment
being discussed in this paper.
Injection time (day)
0 1 2 3 4 5 6 7
Flo
w t
o p
ressure
ratio (
m/s
)
0.0
2.0e-7
4.0e-7
6.0e-7
8.0e-7
1.0e-6
1.2e-6
Phase I
Figure 4-7. Fluid conductance values of Phase I (Jan-Feb, 2012).
Injection time (days)
0 1 2 3 4 5 6 7
Flo
w t
o p
ressure
ratio (
m/s
)
0.0
2.0e-7
4.0e-7
6.0e-7
8.0e-7
1.0e-6
1.2e-6
1.4e-6
Line I
Figure 4-8. Fluid conductance values of Line I (Jan-Feb, 2012).
61
Injection time (days)
0 1 2 3 4 5 6 7
Flo
w t
o p
ressure
ratio (
m/s
)
2.0e-7
4.0e-7
6.0e-7
8.0e-7
1.0e-6
1.2e-6
1.4e-6
1.6e-6
1.8e-6
Line IV
Figure 4-9. Fluid conductance values of Line IV (Jan-Feb, 2012).
Injection time (days)
0 1 2 3 4 5 6 7
Flo
w t
o p
ressure
ratio (
m/s
)
0.0
5.0e-7
1.0e-6
1.5e-6
2.0e-6
2.5e-6
Line V
Figure 4-10. Fluid conductance values of Line V (Jan-Feb, 2012).
Research conducted at PCNCL was performed over a four year period where all
experiments consisted of a significant amount of leachate injected over a short time
frame.
62
To
wn
se
nd
/Sh
red
de
d t
ire
s
To
wn
se
nd
/MS
W
Lars
on-K
um
ar-
Ch
o/G
lass
Lars
on-K
um
ar-
Ch
o/M
SW
Lars
on-K
um
ar-
Ch
o/T
ire
Sin
gh
-wh
ole
tir
es
Ph
ase
I
Lin
e I
Lin
e I
V
Flu
id C
onducta
nce (
m/s
)
1e-7
1e-6
1e-5
1e-4
Figure 4-12. Variation of the fluid conductance values in MSW landfills using different bedding medias for the construction of horizontal injection lines.
Liquids were not injected in the lines for extended periods which allowed the water
level and gas pressure surrounding the injection lines to recede. Operation of the
injection lines under this regime allowed for injection at low pressures as the permit for
such facility requires (3.5 meters of water column), whereas injection lines in this
experiment reached almost 13 meters of water column inside of the lines. The amount
of liquids injected in PCNCL lines that used shredded tires and MSW as bedding media
was bellow 3 m3 per meter of length of the injection line (Figure 4-12), while lines in this
experiment received almost ten times more the amount of leachate per unit of length.
Moreover, phase I of this experiment, performed by Singh (2010), was carried out on
63
newly constructed infiltration trenches that had not received any previous liquids. Also
pressure applied to inject the leachate was less than a meter of water table.
To
wn
se
nd
/Sh
redd
ed
tir
es
To
wn
se
nd
/MS
W
Lars
on-K
um
ar-
Cho
/Gla
ss
Lars
on-K
um
ar-
Cho
/Tir
e
Lars
on-K
um
ar-
Cho
/MS
W
Sin
gh
/wh
ole
tir
es
Ph
ase
I
Lin
e I
Lin
e I
V
Lin
e V
Vo
lum
e/le
ng
th (
m3m
-1)
0
5
10
15
20
25
30
Figure 4-12. Volume of leachate per unit of length of horizontal injection lines using
different materials as bedding media.
The experiment performed by Townsend and Miller (1996) was operated under
similar conditions as the experiment being presented. Both experiments were operated
over a 19 month period; injection lines were operated for a similar amount of time and
injection of liquids was performed at similar pressures. Nevertheless results of this
experiment were considerably lower than ones found by the mentioned authors.
Several site specific conditions can be attributed as the reasons for values of this
experiment to be lower. Jain (2005) determined that waste in NRRL had a density, on
average, of 710 kg/m3. This was assumed to be due to a well performed waste
compaction process. Jain et al. (2006) reported the field saturated hydraulic conductivity
64
of this same site to range from 5.4x10-6 to 6.1x10-5 cm s-1, this being on the lower end
with respect to previously reported data. This can be attributed to several factors, such
as depth of waste, thorough compaction of waste, and also to the clayey soil used for
daily cover in the site.
Another variation in the discussed experiments is the fact that the lines
constructed by Townsend and Miller (1996) were trenches dug in waste after removing
cover soil and later covered with “fresh” waste that was being placed on the cell. Lines
in the present experiment were constructed above a 0.30 m thick layer of clayey cover
soil. This layer of soil was the top cover of a previous lift of waste, considerably thicker
than daily cover soil. Also, the toe of the lift was adjacent to the injection lines. Cover
soil was placed next to the injection lines in order to cover the previously placed
waste.Yang et al. (2001) found that an increase in the degree of compaction of the
intermediate cover soil decreased hydraulic conductivity of the media. Cover soil can
become a barrier, reducing vertical movement of the leachate within the waste matrix. It
is believed that, for the present experiment, constructing the injection lines on top of the
cover soil layer was detrimental for the injection lines performance.
It is widely accepted that, generally, a decrease in the hydraulic conductivity of
waste is observed as overburden pressure increases in deep locations of landfills. Data
for the present experiment was collected after the injection lines were bellow two lifts of
waste (each 6 m thick). Therefore, it is hypothesized that fluid conductance values in
early stages of this project, if measured, would have been substantially higher than the
ones reported. Townsend and Miller (1996) calculated fluid conductance values during
the entire 19 months of operation, while this project began data collection after injection
65
lines had been operated for prolonged periods (13 to 18 months). Fluid conductance
values in the early stages of their experiment were several orders of magnitude higher
than the final values.
The other objective of this research was to evaluate the suitability of whole tires for
the construction of horizontal injection lines. For this purpose, lines’ performances were
compared in terms of volume of leachate injected into the landfill per unit of length of the
line and by the volume of leachate injected per unit of area of the cell on which injection
was taking place. Injection lines in the present experiment received a larger volume of
liquids per unit of length of line when compared to previously published results.
Although two lines were lost at the beginning of the injection process, a large amount of
leachate was injected into the landfill by using the remaining four injection lines.
Benson et al. (2006) analyzed five active bioreactor landfills (Figure 4-13). Data on
the different technical and operational issues was compiled from those landfills which
are located in the eastern region of the United States. Landfills, in that paper, were not
identified by name and a letter was given to each one of them as identification. One of
the analyzed parameters was the amount of leachate per unit of area that was injected
into the bioreactor cells per year. Data from 2011obtained from the present experiment
was compared with the landfills analyzed in the mentioned publication.
As can be appreciated, only landfill Q with a rate of 163 Lm-2 had a higher injection
rate than NRRL (104 Lm-2). In all cases liquids were injected using horizontal injection
lines. Authors did not list the bedding media used for the injection of liquids in those
landfills. Performance of injection lines using whole tires as bedding media was
comparable with other full scale bioreactors.
66
Landfill ID
S D Q C E NRRL
Le
acha
te v
olu
me r
ecir
cula
ted
pe
r year
(L/m
2)
0
20
40
60
80
100
120
140
160
180
Figure 4-13. Typical leachate volume recirculated per unit of area (Lm-2) in several bioreactor landfills throughout the United States.
67
CHAPTER 5 CONCLUSSIONS AND RECOMMENDATIONS
5.1 Summary
Research on horizontal injection lines to evaluate the use of tires as bedding
media and compare different tire arrangements was conducted on a full-scale bioreactor
landfill. This thesis presents data on the development, construction and operation of the
described experiments. Furthermore a hydraulic analysis of the injection system as an
evaluation parameter to verify mentioned research objectives is presented.
Five horizontal injection lines were successfully constructed (configurations A, B,
and C). In addition, the remnants of a previous experiment (Singh 2010) on infiltration
trenches were turned into a horizontal injection line (configuration A) and incorporated
as part of the experiment. Leachate was injected for a 20 month period, during which
11,000 m3 (2,900,000 gallons) of leachate were recycled into the landfill. Two injection
lines were lost due to obstruction leaving four injection lines including the reconfigured
line from previous work. After approximately 18 months of operation pressure
transducers were effectively installed into the lines. Lechate was injected into the four
remaining injection lines (Line types A and B) for five hours a day on weekdays. The
system was closely monitored while data was collected and analyzed for a two month
period. Pressure and leachate flow rates were individually measured. Fluid conductance
values (flow rate to applied pressure ratio) were determined using the measured values.
Landfill gas relief devices were installed to prevent any gas back pressure effect on fluid
conductance values. Fluid conductance values varied from 4.02 x10-5
ms-1 to 6.84x10-5
ms-1 and when compared to values from the literature (Larson 2007; Kumar 2009; Singh
2010) the fluid conductance values obtained from whole tire bedded lines are
68
comparable to fluid conductance values obtained from shredded tire bedded lines and
crushed glass bedded lines.
The effect of the tire arrangements (Configuration A vs. B) on injection line
performance was found to be inconclusive. The two different lengths of the injection
lines showed no difference in the effect on fluid conductance values or the flow rates of
injected liquids. Using fluid conductance as a measure of performance, whole tires as
bedding media for injection lines was compared to other materials (i.e. crushed glass,
shredded tires, and MSW) used in previously published studies. All but one study
yielded results that were comparable to results presented in this thesis. Results
obtained by Townsend and Miller (2006) showed a considerably higher performance
than the present study by using shredded tires as bedding media.
From an operational perspective, lines in this experiment outperformed previous
experiments in terms of volume of leachate per unit of length of injection line. Moreover
the amount of leachate injected per unit of area during the execution of this project was
on the higher end when compared to other bioreactor landfills in the United States.
5.2 Conclusions
Fluid conductance values among injection lines built using configuration A were
considerably different. There was only one line built using configuration B and the only
line that was constructed using configuration C was lost early on in the project due to
differential settlement of the waste in the landfill. Due to these circumstances it was not
possible to make a valid comparison of the performance of the different configurations.
When comparing configurations A and B, configuration A generated the highest fluid
conductance values as well as the best performance in terms of volume of leachate per
unit length of the line.
69
Fluid conductance values, in this experiment, were not affected by the length of
the lines. Phase I and lines IV and V were constructed using the same configuration;
these lines were operated for a similar period and the amount of injected leachate per
unit of length was similar. However, Lines IV and V produced higher fluid conductance
values even though they were 45 m shorter than phase I.
Gas relief devices were installed in each injection line in order to avoid increases
in pressure derived from landfill gas. Installation of gas relief devices proved successful
and allowed for uncomplicated addition of liquids into the horizontal injection lines.
Performance of horizontal injection lines using whole tires as bedding material was
comparable with previously used medias. Although the discussed lines presented lower
fluid conductance values when compared with other materials, the amount of leachate
injected into the lines per unit of length exceeded what was achieved by previous
experiments. Also the amount of leachate injected per unit of area was comparable with
values produced in other bioreactor landfills.
Constructing injection lines on the landfill surface reduced the amount of labor
required for the construction of leachate injection systems. Other issues such as smell
from uncovered MSW and the cost associated with digging trenches for lines were
avoided with the use of this technology.
5.3 Recommendations
Based upon the obtained results and the obstacles encountered in this research,
there are a few noteworthy recommendations for further work on this site and for
horizontal injection line work in general. It is evident that, as done in this work, installing
the monitoring and control equipment at a higher elevation than the injection lines is a
necessary precaution in order to effectively evacuate landfill gas from the injection lines.
70
The installation of gas relief equipment yielded positive results as it allowed larger
volumes of liquids to be injected into the landfill without unnecessary increases in
pressure due to gas. After assessing the method of injection line placement done in this
research it is advisable to place leachate conduction lines in trenches as a way to
prevent mechanical damage caused by landfill compactors. It is equally important for
monitoring equipment to be installed in the early stages of any future experiments so
that the behavior of the injections lines can be better understood. Even though varying
the configuration of whole tires as the bedding media did not give results significantly
different from each other, the performance of the whole tires was comparable to that of
other media used in the literature for protecting landfill injection lines. This research was
an expansion on the first attempt to use whole tires as bedding media for horizontal
injection lines (Singh 2010) and by implementing the above recommendations whole
tires could prove to be an alternative to other bedding medias. Based on this research
and in comparison to similar projects, it is apparent that further research on the
development of the use of whole tires as bedding media for injection lines in landfill
should be explored.
71
LIST OF REFERENCES
Bareither, C. A., Benson, C. H., Barlaz, M. A., Edil, T. B., and Tolaymat, T. M. 2010. Performance of North American bioreactor landfills leachate hydrology and waste settlement. Journal of Environmental Engineering, 136(8), 824-838.
Benson, C. H., Barlaz, M. A., Lane, D. T., and Rawe, J. M. 2007. Practice review of five bioreactor/recirculation landfills. Waste Management, 27(1), 13-29.
Cho, Y. M. 2010. Landfill settlement and food waste impact on the MSW angle of internal friction, Doctoral dissertation, University of Florida, Gainesville, FL.
Hanson, J. L., Yesiller, N., Von Stockhausen, S. A., and Wong, W. W. 2010. Compaction characteristics of municipal solid waste. Journal of Geotechnical and Geoenvironmental Engineering, 136(8), 1095-1102.
Hinkley Center, University of Florida (UF), University of Central Florida (UCF). 2008. Florida bioreactor landfill demonstration project. Gainesville, FL, 4-8.
Jain, P. 2005. Moisture addition at bioreactor landfill using vertical wells: Mathematical modeling and field application, Doctoral dissertation, University of Florida, Gainesville, FL.
Jain, P., Townsend, T. G., and Tolaymat, T. M. 2010. Steady-state design of horizontal systems for liquids addition at bioreactor landfills. Waste Management, 30(12), 2560-2569.
Jain, P., Powell, J., Townsend, T. G., and Reinhart, D. R. 2006. Estimating the Hydraulic Conductivity of Landfilled Municipal Solid Waste Using the Borehole Permeameter Test. Journal of Environmental Engineering, 132(6), 645-652.
Jang, Y. S., Kim, Y. W., and Lee, S. I. 2002. Hydraulic properties and leachate level analysis of Kimpo metropolitan landfill, Korea. Waste Management, 22(3), 261-267.
Kadambala, R. 2009. Evaluation of buried vertical well leachate recirculation system and settlement resulting from moisture addition using vertical wells for municipal solid waste landfills, Doctoral dissertation, University of Florida, Gainesville, FL.
Kumar, S. 2009. Study of pore water pressure impact and fluid conductance of a landfill horizontal liquids system, M.S. thesis, Universtiy of Florida, Gainesville, FL.
Larson, J. A. 2007. Investigations at a bioreactor landfill to aid in the operation ad design of horizontal injection liquid addition systems," M.S. Thesis, University of Florida, Gainesville, FL.
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Pohland, F. G. 1973 . Sanitary landfill stabilization with leachate recycle and residual treatment. Georgia Institute of Technology (GT) and U.S. Environmental Protection Agency(USEPA), Rep. No. EPA-600/2-75-043, Cincinnati, Ohio.
Pohland, F. G., and Kim, J. C. 1999. In situ anaerobic treatment of leachate in landfill bioreactors. Water Science and Technology, 40(8), 203-210.
Reddy, K. R., Hettiarachchi, H., Parakalla, N., Gangathulasi, J., Bogner, J., and Lagier, T. 2009 . Hydraulic conductivity of MSW in landfills. Journal of Environmental Engineering, 135(8), 677-683.
Reinhart ,Debra R. 1996. Full-scale experiment with leachate recirculating landfills: Case studies. Waste Management & Research, 14(4), 347-365.
Reinhart, D. R., McCreanor, P. T., and Townsend, T. 2002. The bioreactor landfill: Its status and future. Waste Management & Research, 20(2), 172-186.
Rubber Manufacturers Association (RMA). 2004. U.S. Scrap Tire Markets 2003 Edition. Washington, DC, 3-15.
Singh, K. 2010. Performance evaluation of surface infiltration trenches and anisotropy determination of waste for municipal solid waste landfills, M.S. thesis, University of Florida, Gainesville, FL.
Townsend, T. G., and Miller, W. L. 1998. Leachate recycle using horizontal injection. Advances in Envioronmental Research, 2(2), 129-138.
Townsend, T. G., Miller, W. L., Hyung-Jib, L., and Earle, J. F. K. 1996. Acceleration of landfill stabilization using leachate recycle. Journal of Environmental Engineering, 122(4), 263-268.
U.S. Environmental Protection Agency (USEPA). 2006. Scrap tire cleanup guidebook. Rep. No. EPA-905-B-06-001, Region 5 Waste Program, Chicago, IL, 2-11.
U.S. Environmental Protection Agency (USEPA). 2009. Municipal solid waste in the United States. EPA530-R-10-012. Office of Solid Waste, Washington D.C.,2-5.
73
BIOGRAPHICAL SKETCH
Jose Antonio Yaquian Luna was born in Guatemala to Rafael Yaquian Perdomo and
Rosario Luna de Yaquian. He enrolled in EARTH University, Costa Rica, and graduated on
December 2008. He joined the University of Florida in August 2009 to be a research
assistant under the guidance of Dr. Timothy Townsend.