1

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

2

© 2012 Jose Antonio Yaquian Luna

3

To my parents

4

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

5

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

6

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

7

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

8

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

9

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

10

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

11

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

12

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.

13

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

14

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.

15

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

16

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,

17

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

18

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.

19

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).

20

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

12

18

Kadambala 2006 IV Vertical 18 6 2 153 days 8,431

9

12

2006 IV Vertical 2 12.2 2 122 days 1,422

Singh 2010 V Horizontal 4 15 3 16 days 365

30

45

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

21

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

22

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

23

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

24

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.

25

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

26

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.

72

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.