Evaluation of Whole Waste Tires as Bedding Media for Liquid Injection Lines in Municipal Solid Waste Landfills

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Title:
Evaluation of Whole Waste Tires as Bedding Media for Liquid Injection Lines in Municipal Solid Waste Landfills
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1 online resource (73 p.)
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english
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Yaquian-Luna, Jose A
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University of Florida
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Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Environmental Engineering Sciences
Committee Chair:
Townsend, Timothy G
Committee Members:
Annable, Michael D
Bloomquist, David G

Subjects

Subjects / Keywords:
bioreactor -- fluid-conductance -- horizontal-injection-lines -- landfill -- leachate -- leachate-recirculation -- whole-tires
Environmental Engineering Sciences -- Dissertations, Academic -- UF
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Environmental Engineering Sciences thesis, M.S.
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theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

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Abstract:
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 paper were found to be similar to previous research with the exemption of one experiment. This was attributed to site specific conditions, such as higher compaction of the waste and the placement of the injection lines on top of a 0.3 m thick layer of clayey soil, unlike previous studies where injection lines were surrounded by waste only. The overall performance of whole tires as bedding media for horizontal injection lines was found to be satisfactory and comparable with other medias. Even though fluid conductance values were not outstandingly high, the volume of leachate injected per unit of length of injection line was found to be substantially higher than other experiments. From an operational perspective, the amount of leachate injected per cell was higher than several other bioreactors using horizontal injection lines as liquids addition method. Finally, by constructing injection lines using whole tires costs in waste excavation, relocation of the waste and bedding media acquisition costs were avoided.
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In the series University of Florida Digital Collections.
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Includes vita.
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Includes bibliographical references.
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Description based on online resource; title from PDF title page.
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This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Jose A Yaquian-Luna.
Thesis:
Thesis (M.S.)--University of Florida, 2012.
Local:
Adviser: Townsend, Timothy G.
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RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-05-31

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1 E VALUATION OF WHOLE WASTE TIRES AS BEDDI NG MEDIA FOR LIQUID INJECTION LINES IN M UNICIPAL SOLID WASTE LANDFILLS By JOSE ANTONIO YAQUIAN LUNA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2012

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2 2012 Jose Antonio Yaquian Luna

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3 To my parents

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4 ACKNOWLEDGMENTS I would like to express my gratitude to my advisor, committee chair man Pro fessor 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 accomplish ment. 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 thankf 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 Kada mbala, Dr. Shrawan Singh, James Lloyd, Adrian Gale, Max Krause, Saraya Sikora and Wesley Oehmig for their cooperation. At last, to my family and Julie McLaughlin for their love and unconditional support

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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 Backgrou nd ................................ ................................ ................................ ... 13 1.2 Problem Statement ................................ ................................ ....................... 14 1.3 Objectives ................................ ................................ ................................ ..... 16 1.4 Research A pproach ................................ ................................ ...................... 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 Reu se 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 Inject ion Lines Location ................................ ................................ 32 3.5 Leachate Recirculation System Construction ................................ ................ 34 3.5.1 Configuration A ................................ ................................ ................... 37 3.5.2 Configuration B ................................ ................................ ................... 38 3.5.3 Configuration C ................................ ................................ ................... 38 3.6 Waste Placement Above Injection Lines ................................ ....................... 40 3.7 System Operation and Monitoring ................................ ................................ 41 3.8 Experiments ................................ ................................ ................................ .. 44 3.9 Injection Schedule ................................ ................................ ......................... 45

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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

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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 t he 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 e vents. ................................ ................................ .......................... 59

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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 tr ansducer 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 inje ction lines. ................................ ................................ ................................ ..... 55 4 4 Pressure and flow into horizontal injection line under two different venting scenarios ................................ ................................ ................................ ............ 57 4 5 Typical water le vel 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 Flu id conductance values of Line IV (Jan Feb, 2012) ................................ ......... 61 4 10 Fluid conductance values of Line V (Jan Feb, 2012) ................................ .......... 61

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9 4 12 Volume of leac hate 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 landf ills throughout the United States. ................................ ............... 66

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10 LIST OF ABBREVIATION S ACSWL Alachua County South West Landfill EPA Environmental Protection Agency FAC Florida Administrative Code FDEP Florida Department of Environmental Protectio n HDPE High Density Polyethylene HIL Horizontal Injection Lines MSW Municipal Solid Waste NRRL New River Regional Landfill PCNCL Polk County North Central Landfill PVC Polyvinyl Chloride

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11 Abstract of Thesis Presented to the Graduate School of th e University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science E VALUATION OF WHOLE WASTE TIRES AS BEDDI NG MEDIA FOR LIQUID INJECTION LINES IN M UNICIPAL SOLID WASTE LANDFILLS By Jose Antonio Yaquian L una May 2012 Chair: Timothy G. Townsend Major: Environmental Engineering Sciences Development of liquid addition system s is a crucial fact or i n the improvement of bioreactor landfill technology Research on this topic aims to improve liquids distributio n within the landfill, while operating it under safe conditions More homogenously distributed liquids wi l l lead to higher decomposition rates of the degradable fraction of the waste, and will incre ase in landfill gas generation which consequently generate s 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, eac h of the lifts was 6 m thick. Six injection lines were constructed; two of them were lost within the first six months of operation. L eachate w as injected in the four remaining lines. Overall, a total 10,700 m 3 of leachate were injected over a 19 month peri od 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 respon ses during this period varied from 6.7 x10 7 m s 1 to 1.2x10 6 m s 1 Fluid conductance values reported on this

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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 h igher 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 wh ole tires costs in waste excavation relocation of the waste and bedding media acquisition costs were avoided

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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 curr ently 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 pas t (EPA, 2009) This increase in waste acceptance together with tighter environmental regulation has driven engineers and operators to make improvements on landfill design and managemen t. 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 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 acceler ates gas production and air space

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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 te chnology. 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 prov ide 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 pr esented 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 l essons. 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 set tlement was observed around injection lines as consequence of the heterogeneity of the liquids distribution. Finally, the injection of liquids at a constant pressure required continuous monitoring for possible seeps.

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15 Presently, due to operational practic ality 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 (T ownsend 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 opt ions 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, impl ies 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 b eing 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 (eit her 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, L arson 2007, Kumar 2009) produced satisfactory results. The durability, geometry and availability of

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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 th e 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 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 bioreact or 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 si ngle line after they were all connected to a common manifold. Both phases of the project were covered with two lifts of 6m t hick each. Operation of the injection lines was started as the lines were constructed and later covered with waste. By January 2011 all the lines were constructed and covered with waste. The project was operated for a 20 month period,

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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 f low 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 constructi on 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 O bjective 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 with a 6 m thickness were placed on top of the lines. Da ta was collected on an hourly basis during leachate injection. Flow and water pressure were monitored. Objective 2. Measure fluid conductance on horizontal injection lines constructed with whole tires in different configurations

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18 Approach. Injection line s 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 lin es were operated simultaneously. Flow and pressure data were monitored on an hourly basis. 1.5 Organization of Thesis This thesis is p resented in five chapters. Chapter 1 presents introductory material, problem statement, objectives, and research approa ch. 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 u sed 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 lin es using different bedding medias. Chapter 5 presents a comprehensive summary and conclusions together with a final recommendation of this experiment Cited references are included at the end.

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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 s uch 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 situ ation 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 u sing this approach d ecomposition 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 fas hion. 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 (T ownsend and Miller 1998).

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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 re levant studies in terms of liquids recirculation in this facility w ere performed by Jain (2005),Kadambala (2009) and more recently Singh used whole tires as bedding materi al 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 syste ms. Table 2 1. Research on liquid distribution systems developed in NRRL. Author Date of Construction Cell Configuration Number of Lines Dimensions Operationa l Period Amount of Injected Leachate (m3) Length (m) Diameter (i n ches) 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 J ain (2005) installed 45 clusters of vertical wells during the spring of 2001 in cells 1 and 2. Each of the clusters consisted of three wells with approximate depths of 6, 12 and 18 meters. The depths were selected according to a survey data and the height of

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21 the bottom lin er Constant moisture addition was conducted for a 2.5 year period, at an average rate of 6.5 m 3 / 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 shallow er 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 m 3 of liquids, (leachate and groundwater) were added to the bioreactor. 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 dis tribution 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 m 3 per day (32,000 gallons) as the maximum amount of leachate to be injected in that cell, consequently flo w rates were kept bellow it, adding between 80 and 120 m 3 A cumulative volume of 8,431 m 3 of liquid was injected. Leachate flow rate per unit screen

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22 length of the buried vertical well was the same or higher than the ones obtained by Jain (2005). Monitorin g 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 land fill 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 C ell 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 mu lti 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 da ys. 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 increme nt of hydrostatic head on the deeper

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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 counter part 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 g iven 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 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 valve and a paddlewhe el flow meter (Sea Metrics IP80 ) were installed at the hydrant connection to control the flow rate and to monitor flow rate at each trench. The water column was measured with a portable

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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 additi on 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 un it pressure head), which ranged from 8.910 6 m/s to 1.210 5 m/s. A total of 365 m 3 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 Horizo ntal 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 allo w 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 t he use of vertical wells, where moisture may not distribute along the entire well screen length due to consolidation of MSW at lower depths. In addition horizontal injection lines can be constructed as a landfill cell is actively accepting waste.

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25 2.4 Pr evi ous Leachate Injection Lines E xperiences 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 we re 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 condu ctance 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 highe r 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 structural changes on the waste matrix due to degradation of the organic fraction of the waste or clogging due to fines entering t he injection lines. The performances of HILs were reported on a range of 1.910 7 m/s to 7.510 7 m/s with an average of 5.310 7 m/s. Kumar (200 9 ) evaluated the fluid conductance values of 31 injection lines of various bedding medias, length, and overbur den 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 gene ral, the HILs with bedding media had higher fluid conductance values than those without bedding media. Fluid

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26 conductance values presented in this experiment range from 1.610 7 m/s to 3.410 6 m/s with an average of 7.810 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 (Towns end and Miller 1998; Larson 2007: Kumar 2009; Cho 2010; Sing h 2010) Benson et al. (2006) reviewe d 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 conduct ance was formulated by Townsend and Miller (1998) as an effort to evaluate horizontal injection li ne performance for their flow pressure 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 t hese 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.

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27 to voltage rat io 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). Figure 2 1. Typical leachate recirculation rates (L m 2 ) in several bioreactor landfills (Benson et al 2006) 3 min 1 m 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 pressu re, and is described in Figure 2 2. Where Q = flow rate, [L3T 1]; L = length of a horizontal pipe, [L]; and Hp = injec tion 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

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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 R eu se and D isposal Acco rding 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 stat es 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.

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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. Thes e landfills are used where there is a lack of markets for scrap tires. States like Alabama allow s 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 tir es 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.

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30 CHAPTER 3 METHO DS AND MATERIALS 3.1 Site Description The experiment on h orizontal injection line s 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 e xperiment 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 m 3 on Cell V. The density of the landfilled waste is 710 kg/m 3 (Jain, 2005). 3.2 Innovative Recycling Grant Development and P ermit Use of horizontal injection lines as a method for liquids distribution is customary practic e 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 tire s are readily available throughout the State, and handling of tires is simpler then dealing with a bulk material. Tire geometry also allows building injection

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31 trenche s 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 Environmen tal 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 F lorida 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 w ere 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 E xperiment The research project carried out by Singh (2010), together with the project discussed on this paper, was part of the innovative recycling gr ant 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 i n length were installed using tires as bedding media. Lines were installed in the surface of the third lift of cell V

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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. F ollowing operatio n as surface infiltration lines the four lines were connected to a common 3 single injection line with a length of 135m. Phase I was covered with waste and operated for a 15 month period. 3.4 Hor izontal Injection Lines L ocation The area in which the injection lines were constructed is located 14.5 meters above the landfill liner the lines were covered with two lifts of waste, each one with an average thickness of 6 meters. A n 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 lift s 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 co ntiguous 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 li ne was co vered in within a mont h.

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33 Figure 3 1. Cross section of Cell V, New River Regional Landfill

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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 cons tructed obeying the waste placement pattern, which was on a north south direction. Landfill operators modified the working face width to be constructed. Since the distance betw een each HIL was 15 meters, researchers had a window of time to construct the next line as the previous was being covered with waste.

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35 Table 3 1 Timeline of tire project experiment in NRRL. 2010 2011 2012 May Jun. Jul. Aug. Sept. Oct. Nov Dec. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Phase I Construction Transducer installation Waste placement Operation Analyzed data Phase 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 W aste placement Operation Analyzed data Line V Construction Waste placement Operation Analyzed data

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36 Leachate injection lines were connected to the main liquid recirculation pipeline which ran along the eastern outer landfill berm to the leacha te 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 padd lewheel 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. a length of 135m.

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37 Each one of the 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 c an be appreciated on Figu re 3 3 configuration A consisted of s tanding tires with pipe running through the center of them To construct lines with this configuration tires were unloaded from roll off boxes on several p oints along the length of the future line. I mmediately a fter 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 struct HDPE pipe would be introduced in to 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. Config uration A horizontal injection line being built on top of Cell V of NRRL (Picture taken by author.)

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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 lat er attached betwe en each other with rope, later a second layer of tires was placed on top .T ires 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 wer e 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 pro v ed to be relatively easy in terms of tire placing, however attaching the tires became time consuming as rope had t o 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 Configurati on 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 structu ral

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39 perspective it had a width to height ratio of 2 which added stability, compared with Configuratio n B with a ratio of 1 Also this configuration was not displaced during waste placement unlike the other configurations. The lines of Configuration A we re 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 were put back in the container and later hauled to a tire disposal facility Most tires were in good c ondition 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 strengt h of the injection lines All the tires were attached between each other using stranded polyethylene rope. After each line was

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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 i njection lines located 15 meters above the liner. The forth lift of waste was placed on top of the injection lines from August to Dec ember 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 L ines Injection lines were installed on the surface of an active cell, later, two lifts of waste were placed on top of them. To protect t he i ntegrity of the injection lines, these

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41 were constructed adjacent to the toe of the lift, thus it was possible to push wa ste from a higher point and pile it on top of the lines without machinery interference Waste was piled on top of the lines until th e 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 o ther 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 T esting With the intent of test ing the i ntegrity of the injection lines a diameter pipe was introduced to the injection lines. This line was 1 70 meters long as this was the cumulative length of the solid and perforated sections of the injection pipe line 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 O pe ration and M onitoring Injection lines were constructed i n a six month span. Even wh en some of the lines were constructed and covered with waste, operation was irregular due to time

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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 appreci ate 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 du ring 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 D atalogger recorded the average of th e 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. to protect the line and ease the introduction of the transducer on the injection line. Figure 3 8 depicts the instrumentation setup for this experi ment.

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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

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44 of the transducer s in the injection lines, transducers were inserted into perforated 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 de tailing different stages of tire project. Aug Dec 2010 Jan Nov 2011 Dec 11 Jan Feb 2012/ Days of Operation Constr uction and prelimi nary injectio n Injecti on witho ut press ure trans ducer Press ure trans ducer install ation 7 Jan 8 Jan 10 Jan 12 Jan 12 Jan 25 Jan 26 Jan 27 Jan 28 Jan 29 Jan 1 Feb 2 Feb 3 Feb 6 Feb 7 Feb 8 Feb 9 Feb 10 Feb 16 Feb 18 Feb 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 m 3 (74 gal.) per minute rate. F low would experience slight decreases as a product of increments on the water level

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45 inside of the injection lines. Water level average was recorded every five m inutes 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 tha n previously reached for the same volume of leachate previo usly injected. Water level did not re cede 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 continuousl y 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 S chedule Injection lines were constructed over a seven month period (May Dec ember, 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 Decemb er 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 Dec ember 2 011 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 line s 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 PVC pipeline as a way to add sturdiness and to ease the introduc tion of the jaw through the line. When the jaw reached the obstruction point it was pumped until it

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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. Differenti al settlement was attributed as the reason for line III to be obstructed, since waste was placed over the Line II was found to be obstructed close to the surface; it is believed that the line was cru shed by landfill machinery.

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47 CHAPTER 4 RESULTS AND DISCUSSI ON 4.1 Construction and Operational Observations C onstruction of the injection lines was carried out by the researcher with landfill personnel assistance. A 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 contaminat ed 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 5 85 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 (Phas e 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

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48 trench. This procedure would not have been possible with any of the other configurations. Fig ure 4 1. Injection line being pushed inside of the trench during Phase I construction (Pictu re 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 tire s 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.)

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49 Construction of the remaining lin es 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 cons 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. Constru cting 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 i ntensive 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 ensur e cohesion of the structure. The placement of this protective media was crucial to

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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 dif ferent 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. Assembl y of HDPE pipeline during constructi on 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 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 op erators 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 betwe en 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 w as 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 m 3 of leachate was injected.

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51 From September 2010 to November 2011, as phase I was covered with waste and the other five injection lines were cons tructed and operated; 8,800 m 3 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 mi grate 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. T he system was then operated for a total of 20 days from January to February 2012 during which 1,600 m 3 of leachate was injec ted. 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 (m 3 ) Hours of Operation Volume Injected (m 3 ) Hours of Operation Volume Injected (m 3 ) Hours of Operation Volume Injected (m 3 ) 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

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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 (m 3 ) Flow rate (m 3 min 1 ) Flow rate (gal min 1 ) Average l inear flow rate (m 3 min 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 Wor king 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 month s as a horizontal injection line. This line received the largest amount of leachate (2359 m 3 ); however it was a cluster of lines that totalled 135 m in length. Thus, the average linear flow rate 5x10 4 m 3 min 1 m 1 ) was lower compared to other injection lin es. 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 m 3 min 1 (12 gal min 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 vol ume 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

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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 m 3 min 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 m 3 min 1 ( 16 galmin 1 ) throughout the experiment. The possibility of low flow in Line II due to settlement or decomposition of the surrounding waste w as 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 (Li nes 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 obstr uction but the procedure was not successful. A total of 662 m 3 was injected into this line. No fluid conductance value was obtained from this line. performance was rema rkably 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 m 3 of leachate was injected into this line. This line had an average flow rate of 0.08 m 3 min 1 ; while the average of the 3 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 i n between layers. It is believed that the larger amount of tires cushioned

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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 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 m 3 min 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 2 0 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 inje ction 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 distribu tion 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. Duri ng 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 inje ction 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

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55 With the intent to prevent gas from disrupting the injection proces s, gas relief devices (Figure 4 3) were installed on each line. Such device consisted of a 0.75 m ose and the top was open to the atmosphere. Figure 4 3. Landfill gas relie f de vices installed on the solid pipe section of horizontal injection lines. (Pi cture taken by author.) By using these devices, gas pressure was successfully released from the injection line s These devic es 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 functiona lity of the devices, two injection scenarios were compared: injection under vented and injection under non vented conditions. This experiment was performed in February 2012.

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56 Line IV was operated under non vented conditions for five hours. This line ial 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 incr ease in the landfill gas pressure. Figure 4 4 shows a contrast between typical pressure observed during normal inj ection conditions and under non vented conditions. Flow of leachate during both scenarios is also compared. Pressure under vented conditions i ncrease d significantly at the beginning of the injection process and increased steadily until a plateau was reached. On the other hand, p ressure 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 m 3 (20 gal ), while the same line under vented conditions received 17.7m 3 (4670 gal) over the five hour period. Injection Lines Operation In jection 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 m 3 /min (64 gal /min ) flow rate. Table 4 5 presents ave rage 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 dur ing 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.

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57 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 (m 3 /min) Linear flow rate (10 3 m 3 min 1 m 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 o f 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 o f the water level inside of the injection line.

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58 Figure 4 5. Typical water level behavior during leachate injection (Feb 1st, 2012) Figure 4 6. Typical w ater 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

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59 course of the experiment. Table 4 6 shows initial and final fluid conductance value s from an early injection event (Jan 7 th ) contrasted with one of the final events (Feb 16 th ). 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 pre viously 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. Lan dfill 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 decre ase 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

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60 2010) and more recently by Singh (2010) at NRRL. H owever it must be noted that there are several fundamental differences between tho se experiments and the experiment being discussed in this paper. Figure 4 7. Fluid conductance values of Phase I (Jan Feb, 2012 ) Figure 4 8. Fluid conductance values of Line I (J an Feb, 2012)

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61 Figure 4 9. Fluid conductance values of Line IV (Jan Feb, 2012) Figure 4 10. Fluid conductance values of Line V (Jan Feb, 2012 ) Research conducted at PCNCL was perfo rmed over a four year period where all experiments consisted of a significant amount of leachate injected over a short time frame.

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62 Figure 4 12. Variation of the fluid conductance values in MSW landfills using differen t bedding medias for the construction of horizontal injection lines. L iquids 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 unde r 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 injec ted in PCNCL lines that used shredded tires and MSW as bedding media was bellow 3 m 3 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

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63 newly constructed infiltration trenches that had not received any previous liquids A lso pressure applied to inject the leachate was less than a meter of water table. 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 experi ment 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 l ower 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/m 3 This was assumed to be due to a well performed waste compaction process Jain et al. (2006) reported the field saturated hydraulic conductivity

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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 resp ect to previously reported dat a. 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 Towns end and Miller (1996) were trenches dug in waste after removing in th e 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, considerabl y 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 wast e. 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 ob served as overburden pressure increases in deep locations of landfill s Data for the present experiment was collected after the injection lines were bellow two lifts of waste (each 6 m thick) Therefore, i t is hypothesized that fluid conductance values in early stages of th is project, if measured, would ha ve 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

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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 compared in terms of volume of leachate injected into the landfill per unit of length of the line and by the volume of leachate i njected 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 a t 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 p arameters 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, on ly 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. Perfor mance of injection lines using whole tires as bedding media was comparable with other full scale bioreactors.

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66 Figure 4 13. Typical leachate volume recirculated per unit of area (Lm 2 ) in several bioreactor landfills th roughout the United States.

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67 CHAPTER 5 CONCLUSSIONS AND REC OMMENDATIONS 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 la ndfill. 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 m 3 (2,900,000 gallons) of leachate were recycled into the landfill. T wo injection lines were lost due to obstruction leaving four injection lines including the reco nfi gured line from previous work. After approximately 18 months of operation pressure transducers were effectively installed into the lines. Lechate was injected into t he 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 v alues. 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; Kuma r 2009; Singh 2010 ) the fluid conductance values obtained from whole tire bedded lines are

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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 o f 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 experim ents 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 inject ion 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 t he 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 gen erated the highest fluid conductance values as well as the best performance in terms of volume of leachate per unit length of the line.

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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 sh orter 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 in jection 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 o f 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 i njection 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.

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70 The installation of gas relief equ ipment yielded positive results as it allowed larger volumes of liquids to be injected into the landfill without unnecessary incr eases in pressure due to gas. After assessing the method of injection line placement done in this research it is advisable to p lace 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 injec tions 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 t he 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 ( Sing h 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 explor ed.

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71 LIST OF REFERENCES Bareither, C. A., Benson, C. H., Barlaz, M. A., E d il, 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 83 8. Benson, C. H., Barlaz, M. A., Lan e, 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 s ettlement and f ood w aste i mpact on the MSW a ngle of internal friction Doctoral d issertation, University of Florida, Gainesville, FL. Hanson, J. L., Yesiller, N., Von Stoc khausen, 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: Math ematical modeling and field application Doctoral d issertation, 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 lan dfills. Waste Manag ement 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 Kimp o metropolitan landfill, Korea. Waste Management 22(3), 261 267. Kadambala, R. 2 009. Evaluation of buried vertical well leachate recirculation system a nd settlement resulting from moisture addition using vertical wells for municipal solid waste landfills Doctoral d issertation, 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. t hesis, 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 Flori da, Gainesville, FL.

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72 Pohland, F. G. 19 73 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. Pohl and, 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 co nductivity of MSW in landfills. Journal of Environmental Engineering 135(8), 677 683. R einhart ,Debra R 1996. Full scale experiment with leachate recirculating landfills : Case studies Waste Management & Research 14(4), 347 365. Reinhart, D. R., McCrean or, P. T., and Townsend, T. 2002. The bioreactor landfill: Its status and future. Waste Management & Research 20(2), 172 186. Rubber Manufacturers Association (RMA). 2 004 U.S. Scrap Tire Marke ts 2003 Edition. Washington, DC, 3 15. Singh, K. 2010. Perform ance evaluation of surface infiltration trenches and anisotropy determination of waste for municipal solid waste landfills, M.S. t hesis, University of Florida, Gainesville, FL. Townsend, T. G., and Miller, W. L. 1998. Leachate recycle using horizontal inje ction. 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 (USEP A). 2009 Municipal solid waste in the United States. EPA530 R 10 012. Office of Solid Waste Washington D.C.,2 5.

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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.