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Performance Evaluation of Surface Infiltration Trenches and Anisotropy Determination of Waste for Muncipal Solid Waste L...

Permanent Link: http://ufdc.ufl.edu/UFE0042313/00001

Material Information

Title: Performance Evaluation of Surface Infiltration Trenches and Anisotropy Determination of Waste for Muncipal Solid Waste Landfills
Physical Description: 1 online resource (88 p.)
Language: english
Creator: Singh, Karamjit
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Liquids addition is sometimes practiced at landfills as method to accelerate waste stabilization, and at times, simply for leachate management. A variety of liquids addition methods are utilized, from surface application to pressurized injection in horizontal trenches or vertical wells. However further research is required to make these leachate addition systems more effective. The present research evaluated specific issues related to vertical wells and shallow horizontal trenches; both studies were conducted at the New River Regional Landfill (NRRL). This thesis is organized into two main research objectives. The first objective was to estimate anisotropy (i.e., ratio of lateral to vertical hydraulic conductivity) of MSW at different depths inside a landfill using pressure transducers in the waste surrounding a vertical well. Liquids addition was performed at a constant injection pressure for 14 days; the flow rate of added liquids and the resulting pore pressures in the surrounding waste were closely monitored. The flow rate and the pore pressures were assumed to reach steady state by the end of injection period. Numerical fluid flow modeling software was used to simulate the pore pressures expected to occur under the conditions operated. Nine different simulations were performed: three different lateral hydraulic conductivity values (i.e. 1times10-3, 1times10-4 and 1times10-5 cm/s) and three different anisotropy values (i.e. 1, 10 and 100). The field data (i.e., approximate steady state flow rate and pore pressures) were compared with the simulation results to estimate the hydraulic conductivity and the anisotropy. The anisotropy values were found ranging from 2 to 100 with an average value of 36. The second objective was to evaluate the performance of surface infiltration trenches (SITs). Four SITs, with different lengths, were installed at NRRL with whole tires as a bedding media. To construct the SITs, whole scrap tires were tied together face to face with nylon rope and then installed in 1.2 m deep excavated trenches by placing a 7.6 cm perforated HDPE pipe in the middle of tied tires. The perforated pipe was connected to the header pipe and liquids addition was performed for 16 days after covering the trench with 0.3 m of compacted clay. The performance of the SITs was measured in terms of the unit flux (flow rate per unit length), infiltration rate (unit flux per unit width of trench) and fluid conductance (unit flux per unit pressure head). The unit flux was found in a range of 8.0times10-6 m2/s to 1.1times10-5 m2/s, the infiltration rate ranged from 8.0times10-6 m/s to 1.1times10-5 m/s, and fluid conductance ranged from 8.9times10-6 m/s to 1.2times10-5 m/s. The hydraulic conductivity of the waste surrounding the trenches was also estimated by comparing the field results with modeling results. The modeling was performed under the conditions similar to the field conditions and the average vertical hydraulic conductivity was found as 2.0times10-5 cm/s at an anisotropy ratio of 100.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: 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 Karamjit Singh.
Thesis: Thesis (M.E.)--University of Florida, 2010.
Local: Adviser: Townsend, Timothy G.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042313:00001

Permanent Link: http://ufdc.ufl.edu/UFE0042313/00001

Material Information

Title: Performance Evaluation of Surface Infiltration Trenches and Anisotropy Determination of Waste for Muncipal Solid Waste Landfills
Physical Description: 1 online resource (88 p.)
Language: english
Creator: Singh, Karamjit
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Liquids addition is sometimes practiced at landfills as method to accelerate waste stabilization, and at times, simply for leachate management. A variety of liquids addition methods are utilized, from surface application to pressurized injection in horizontal trenches or vertical wells. However further research is required to make these leachate addition systems more effective. The present research evaluated specific issues related to vertical wells and shallow horizontal trenches; both studies were conducted at the New River Regional Landfill (NRRL). This thesis is organized into two main research objectives. The first objective was to estimate anisotropy (i.e., ratio of lateral to vertical hydraulic conductivity) of MSW at different depths inside a landfill using pressure transducers in the waste surrounding a vertical well. Liquids addition was performed at a constant injection pressure for 14 days; the flow rate of added liquids and the resulting pore pressures in the surrounding waste were closely monitored. The flow rate and the pore pressures were assumed to reach steady state by the end of injection period. Numerical fluid flow modeling software was used to simulate the pore pressures expected to occur under the conditions operated. Nine different simulations were performed: three different lateral hydraulic conductivity values (i.e. 1times10-3, 1times10-4 and 1times10-5 cm/s) and three different anisotropy values (i.e. 1, 10 and 100). The field data (i.e., approximate steady state flow rate and pore pressures) were compared with the simulation results to estimate the hydraulic conductivity and the anisotropy. The anisotropy values were found ranging from 2 to 100 with an average value of 36. The second objective was to evaluate the performance of surface infiltration trenches (SITs). Four SITs, with different lengths, were installed at NRRL with whole tires as a bedding media. To construct the SITs, whole scrap tires were tied together face to face with nylon rope and then installed in 1.2 m deep excavated trenches by placing a 7.6 cm perforated HDPE pipe in the middle of tied tires. The perforated pipe was connected to the header pipe and liquids addition was performed for 16 days after covering the trench with 0.3 m of compacted clay. The performance of the SITs was measured in terms of the unit flux (flow rate per unit length), infiltration rate (unit flux per unit width of trench) and fluid conductance (unit flux per unit pressure head). The unit flux was found in a range of 8.0times10-6 m2/s to 1.1times10-5 m2/s, the infiltration rate ranged from 8.0times10-6 m/s to 1.1times10-5 m/s, and fluid conductance ranged from 8.9times10-6 m/s to 1.2times10-5 m/s. The hydraulic conductivity of the waste surrounding the trenches was also estimated by comparing the field results with modeling results. The modeling was performed under the conditions similar to the field conditions and the average vertical hydraulic conductivity was found as 2.0times10-5 cm/s at an anisotropy ratio of 100.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: 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 Karamjit Singh.
Thesis: Thesis (M.E.)--University of Florida, 2010.
Local: Adviser: Townsend, Timothy G.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042313:00001


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1 PERFORMANCE EV ALUATION OF SURFACE INFILTRATION TRENCHES AND ANISOTROPY DETERMINATION OF WASTE FOR MUNCIPAL SOLID WASTE LANDFILLS By KARAMJIT SINGH A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIR EMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010

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2 2010 Karamjit Singh

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3 To my parents and my loving girlfriend

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4 ACKNOWLEDGMENTS I would like to thank my committee chairman Dr. Timothy G. Townsend for his guidance and encouragement though the research I am and will always be indebted to him for training me for the professional world. I wou ld also like to thank Dr. Michael D. Annable and Dr. Louis H. Motz for their participation and guidance in completing my research I am thankful to Darrell ONeal, Executive Director, Perry Kent and Lydia Greene of NRSWA for their guidance, support and s pe cial thanks go to Richard Crews and David Mckinney for their support throughout the construction of my project. I would like to thank Dr. Pradeep Jain, Dr. Ravi Kadambala, Antonio, Youngmin Cho, Shrawan Singh, Dr. Hwidong Kim, Dr. Jae Hac and Dr. Qiyong Xu for their assistance and cooperation in this work. I would also like to thank Mark G. Roberts for his support during the last phase of thesis writing. Last, but not least, I would like to thank my girlfriend Loveenia Gulati for her understanding and love during the past few years. Her support and encouragement was in the end what made this thesis possible. My parents, Harmeet Singh and Tejinder Kaur receive my deepest gratitude and love for their dedication and the many year s of support during my undergraduate studies that provided the foundation for this work.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................................... 4 LIST OF TABLES ................................................................................................................................ 7 LIST OF FIGURES .............................................................................................................................. 7 A BSTRACT .......................................................................................................................................... 8 CHAPTER 1 INTRODUCTION ....................................................................................................................... 11 1.1 Background ........................................................................................................................... 11 1.2 Problem Statement ................................................................................................................ 12 1.3 Research Objectives .............................................................................................................. 14 1.4 Research Approach ............................................................................................................... 15 1.5 Organi zation of Thesis .......................................................................................................... 16 2 ANISOTROPY DETERMINA TION OF LANDFILLED M UNCIAL SOLID WASTE ...... 17 2.1 Introduction ........................................................................................................................... 17 2.2 Materials and Methods ......................................................................................................... 19 2.2.1 Experimental Approach ............................................................................................. 19 2.2.2 Field Experiments ....................................................................................................... 20 2.2.3 Modeling ..................................................................................................................... 21 2.2.4 Anisotropy E stimation ............................................................................................... 23 2.3 Results and Discussions ........................................................................................................ 24 2.3.1 Field Results ............................................................................................................... 24 2.3.2 Simulation Results ...................................................................................................... 25 2.3.3 An isotropy Estimation ............................................................................................... 27 2.3.4 Verification of Results ............................................................................................... 29 2.4 Conclusions ........................................................................................................................... 30 3 PERFORMANCE EV ALUATION OF SURFACE INFILTRATION TRENCHES WITH WHOLE TIRES AS A BEDDING MEDIA.................................................................. 42 3.1 Introduction ........................................................................................................................... 42 3.2 Materials and Methods ......................................................................................................... 43 3.2.1 Site Description .......................................................................................................... 43 3.2.2 Installation and Operation of SITs ............................................................................ 44 3.2.3 Modeling ..................................................................................................................... 45 3.2.4 Hydraulic Conductivity Estimation ........................................................................... 47 3.2.5 Model Limitations ...................................................................................................... 47 3.3 Results and Discussion ......................................................................................................... 47

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6 3.3.1 Performance of SITs .................................................................................................. 47 3.3.2 Hydraulic Conductivity Estimation ........................................................................... 49 3.3.3 Pros and Cons of SITs ................................................................................................ 50 3.4 Conclusions ........................................................................................................................... 51 4 SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS ........................................... 60 4.1 Summary................................................................................................................................ 60 4.2 Conclusions ........................................................................................................................... 61 4.3 Recommendations ................................................................................................................. 61 APPENDIX A SUPPLE MENTAL FIGURES FOR CHAPTER 2 ................................................................... 63 B CONSTRUCTION PHOTOGRAPHS FOR CHAPTER 3 ...................................................... 74 LIST OF REFERENCES ................................................................................................................... 84 BIOGRAPHICAL S KETCH ............................................................................................................. 88

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7 LIST OF TABLES Table page 2 1 Parameters used for the numerical modeling ....................................................................... 32 2 2 Hydraulic conductivity of different layers with respect to layer 2 ...................................... 32 2 3 Comparison of field data and simulation data for the first scenario ................................... 33 2 4 Comparison of field data and simulation data for the second scenario .............................. 33 3 1 Parameters used for numerical modeling .............................................................................. 52 3 2 Compilation of field and modeling results ........................................................................... 52

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8 LIST OF FIGURES Figure page 2 1 A) New River Regional Landfill (NRRL) showing the area which contains the moisture addition and the piezometer wells; B) the close up of the liquids addition wells and piezometer wells in the research area ................................................................... 34 2 2 Cross Sectional View of the liquids addition wells and the piezometer wells ................... 35 2 3 Simulated landfill showing different layers of the media/waste ......................................... 36 2 4 Pore Pressure Vs Time for the piezometers located at A) 7.8m depth; B) 10.8 m depth; C) 13.8 m depth; (from field data) ............................................................................. 37 2 5 Plots generated through modeling results for first scenario A) at landfill depth of 7.8 m; B) at landfill depth of 10.8 m; and C) at landfill depth of 13.8 m. The plots also include field data points ......................................................................................................... 38 2 6 Plots generated through modeling results for second scenario A) at landfill depth of 7.8 m; B) at landfill depth of 10.8 m; and C) at landfill depth of 13.8 m. The plots also include field data points ................................................................................................. 39 2 7 Comparison of anisotropy results for two different scenarios ............................................. 40 2 8 Comparison of pore pressures field results with results of the simulation carried out for the verification of results ................................................................................................. 41 3 1 Plan View of Cell 5 of New River Regional Landfill showing locations of the Surface Infiltration Trenches ................................................................................................. 53 3 2 Configuration of whole scrap tires used as a bedding media in the surface infiltration trenches: (a) Plan View; (b) Cross Sectional View along width; and (c) Cross Sectional View along length of the trench ............................................................................ 54 3 3 Simulated landfill with showing A) dimensions of the simulated landfill and location of the SIT; B) closer look of the SIT .................................................................................... 55 3 4 Flow rate and pressure head data with respect to time for A) 15 m trench; B) 30 m trench; C) 45 m trench; and D) the second 45 m trench. ..................................................... 56 3 5 Flow rate and pressure head data with respect to cumulative volume for A) 15 m trench; B) 30 m trench; C) 45 m trench; and D) the second 45 m trench. .......................... 57 3 6 Plot generated from the modeling results ............................................................................. 58 3 7 Flux values from field data plotted on the plot generated by modeling results for A)15 m trench; B) 30 m trench; C) 45 m trench; and D) the second 45 m trench. ............ 59

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9 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Master of Science PERFORMANCE EVALUATION OF SURFACE INFILTRATION TRENCHES AND ANISOTROPY DETERMINATION OF WASTE FOR MUNCIPAL SOLID WASTE LANDFILLS By Karamjit Singh December 2010 Chair: Timothy G. Townsend Major: Environmental Engineering Sciences Liquids addition is sometimes practiced at landfills as method to accelerate waste stabilization, and at times, simply for leachate management. A variety of liquids addition methods are utilized, from surface application to pressurized injection in horizontal trenches or vertical wells. However further research is required to make these leachate addition systems more effective The present research evaluated specific issues related to vertical wells and shallow horizontal trenches; both studies were conduct ed at the New River Regional Landfill (NRRL). This thesis is organized into two main research objectives. The first objective was to estimate anisotropy (i.e., ratio of lateral to vertical hydraulic conductivity) of MSW at different depths inside a landfil l using pressure transducers in the waste surrounding a vertical well. Liquids addition was performed at a constant injection pressure for 14 days; the flow rate of added liquids and the resulting pore pressures in the surrounding waste were closely monito red. The flow rate and the pore pressures were assumed to reach steady state by the end of injection period. Numerical fluid flow modeling software was used to simulate the pore pressures expected to occur u nder the conditions operated. Nine differen t simu lations were performed: three different lateral hydraulic conductivity values (i.e. 1103, 1104 and 1105

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10 cm/s) and three different anisotropy values (i.e. 1, 10 and 100). The field data (i.e., approximate steady state flow rate and pore pressures) wer e compared with the simulation results to estimate the hydraulic conductivity and the anisotropy. The anisotr opy values were found ranging from 2 to 100 with an average value of 36. The second objective was to evaluate the performance of surface in filtrati on trenches (SITs). F our SITs, with different lengths, were installed at NRRL with whole tires as a bedding media. To construct the SITs, whole scrap tires were tied together face to face with nylon rope and then installed in 1.2 m deep excavated trench es by placing a 7.6 cm perforated HDPE pipe in the middle of tied tires. The perforated pipe was connected to the header pipe and liquids addition was performed for 16 days after covering the trench with 0.3 m of compacted clay. The performance of the SITs wa s measured in terms of the unit flux (flow rate per unit length), infiltration rate (unit flux per unit width of trench) and fluid conductance (unit flux per unit pressure head). The unit flux was found in a range of 8.0106 m2/s to 1.1105 m2/s, the inf iltration rate ranged from 8.0106 m/s to 1.1105 m/s and fluid conductance ranged from 8.9106 m/s to 1.2105 m/s. The hydraulic conductivity of the waste surrounding the trenches was also estimated by comparing the field results with modeling results. The modeling was performed under the conditions similar to the field conditions and the average vertical hydraulic co nductivity was found as 2.0105 cm/s at an anisotropy ratio of 100.

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11 CHAPTER 1 INTRODUCTION 1.1 Background Municipal solid waste (MSW) generation in the United States increased from 88.1 million tons in the year 1960 to 254.1 million tons in 2007 (an 188% increase in 47 years ; U S EPA 2007). Approximately 93% of MSW was disposed of in landfills in 1960, and while this has decreased over time ( 54% of MSW was landfilled in 2007), well over 1 00 million tons of MSW remains landfill ed in the U S every year ( U.S. EPA 2008). In the last two decades, engineered landfills have evolved from being open dumps with negligible control, to controlled and sophisticated containment systems (Kadambala 2009) Typically, the landfills in the United States are designed and o perated in accordance with the requirements of Subtitle D of the Resource Conservation and Recovery Act (RCRA). These landf ills are equipped with a liner and a leachate collection and removal system. The waste in these landfills may take a long time to degrade or decompose and hence such landfills may require indefinite maintenance. The concept of bioreactor landfills was introduced to increase the rate of waste degradation in such landfills (Reinhart and Townsend 1997). A bioreactor landfill operates to rapidly transform and degrade organic waste. The increase in waste degradation and stabilization is accomplished through the addition of liquid (and in some cases, air) to enhance microbial processes ( U.S. EPA 2007). Bior eactor landfill configurations include anaerobic bioreactors (moisture is added to the waste mass in the form of recirculated leachate and other sources, in the absence of oxygen, to obtain optimal moisture levels), aerobic bioreactors (adding liquids alon g with air into the landfill in a controlled manner) and hybrid bioreactors (accelerates waste degradation by employing a sequential aerobic anaerobic treatment to rapidly degrade organics ).

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12 P otential bioreactor landfill advantages include faster decomposi tion and biological stabilization of waste, a decrease in toxicity and mobility of waste, a reduction in leachate disposal costs, a gain in landfill space due to decomposition of waste, an increase in landfill gas production (energy source) and reduced post -closure care effort and costs (Jain 2005) Bioreactor landfills also have several possible problems, including a reduction in MSW shear strength (and possible slope stability concerns) leachate breakouts from the sides of the landfill, an increase in t he leachate head build up on the liner and an increase in uncontrolled landfill gas emissions (Khire et al 2006, Reinhart and Townsend 1997). Over the past several decades investigat ors have researched various aspects of bioreactor processes to make the se systems a more viable option for solid waste management (Pohland 1975, 1980, Pohland et al 1986, Townsend et al 1996, Reinhart et al 1997, 2002, Mehta et al 2002). Even though a significant amount of research has been performed on bioreactor landfil ls, additional research is required to make this technology more efficient. 1.2 Problem Statement Several full -scale operations have been implemented in U.S. to evaluate the performance of bioreactor landfills (Pacey et al 1999, Jain et al 2005 and Benson et al 2007). One such full scale bioreactor is at the New River Regional Landfill (NRRL) located in Union County, Florida. The landfill currently consists of five contiguous lined landfill cells totaling approximately 25 hectares. A detailed des cription of the site and the bioreactor can be found elsewhere ( Jain 2005, Kadambala 2009). Jain et al (2005) evaluated the performance of vertical wells for landfill leachate recirculation and several lessons were learned that prompted this research. In 2 007, nine v ertical well clusters (each having nine vertical wells) were constr ucted in cell 4 and part of cell 2 and Kadambala (2009) evaluated the performance of modified vertical wells for landfill leachate recirculation. In 2007, another two 12.2 m deep modified ver tical wells were

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13 constructed and surrounded by 18 multi -level piezometers ; Kadambala (2009) evaluated the lateral and spatial moisture moment by injecting liquids through one of the two constructed vertical wells. There have been a number of laboratory and field studies conducted to measure hydraulic conductivity of MSW (Shank 1993, Townsend 1995, Gabr 1995, Jain 2005, Koerner and Eith 2005 and Durmusoglu 2006); however, not much information is available on anisotropy of landfilled waste, defi ned as the ratio of lateral (horizontal) to vertical h ydraulic conductivity Landva et al. (1998) reported anisotropy value as 8 and Hudson et al. (1999) reported anisotropy value in a range of 2 to 5. However, both the studies were conducted on lab scale and may not represent the actual anisotropy values for a full scale operating landfill. Anisotropy is an important design parameter because radial (horizontal) and vertical impact zones, created due to liquids addition, are closely associated with it. When designing a subsurface moisture addition system, the spacing between vertical wells or horizontal injection lines (HILs) is based upon impact zones created by moisture addition and thus, anisotropy is one of the most important parameter to determine spaci ng. Additional efforts are needed to better determine anisotropy of landfilled waste. Both surface and subsurface liquids addition system s are practiced at bioreactor landfills. Horizontal injection lines and vertical wells are two examples of subsurface liquids additions systems and considerable research has been conducted on various aspects of these systems (McCreanor et al. 1996 and 2000, Townsend et al. 1998, McCreanor 1998, Haydar et al. 2004 and 2005, Jain 2005, Larson 2007, Kadambala 2009). Surface infiltration ponds and surface infiltration trenches are two types of surface liquids addition systems less research has been conducted (Townsend et al. 1995). Surface infiltration trenches (SITs) are an inexpensive option

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14 for liquids addition and SITs can possibly eliminate some problems associated with surface infiltration ponds such as generation of additional leachate due to rainfall runoff, vectors at traction, odor and aesthetic issues. Moreover, the SITs may perform better than the subsurface liquids addition system as hydraulic conductivity of waste is higher near the surface as compared to the deep regions (Bleiker et. al. 1993) Therefore, it requi res some efforts to explore the viability of using SITs as a liquids addition system. Many different types of bedding materials have been used in past for uniform distribution of liquids like shredded t ires, mulch, and crushed glass (Larson 2007 and Kuma r 2009), but whole scrap tires have never been reported as bedding material. S crap tire management is a challenge i n solid waste management field. Approximately 300 million scrap tires (4.4 million tons) were generated in 2005 and these scrap tires were ma naged by using them as fuel for incinerators, land application a nd stockpiling them ( U.S. EPA 2006). Another option for the management of scrap tires is to use shredded tires as a bedding material and this option has been practiced at some operating landfi lls (Larson 1997, Kumar 2009) If whole scrap tires can be used as a bedding material instead of shredded tires, then no processing is required, an economical and environmental benefit. Research to evaluate the option of using whole tires as a bedding mate rial is thus warranted 1.3 Research Objectives The purpose of this research was to explore some of the specific aspects of bioreactor design and operation. All the experiments were conducted at the New River Regional Landfill (NRRL). The objectives of the research herein were to accomplish the following: To estimate anisotropy of landfilled waste and its magnitude at different depths within the landfill. To examine performance of surface infiltration trenches with whole tires as a bedding material.

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15 1.4 Research Approach Objective 1. To estimate anisotropy of landfilled waste at different depths within the landfill Approach. Leachate recirculation was carried out intermittently and continuously in a buried vertical well at NRRL for a period of 14 days. The flow rate, leachate injection pressure, and cumulative volume of leachate injected were closely monitored ; the change in pore pressure was monitored in surrounding piezometers (installed 1.5 m away from the well and at different depths). The flow rate in the injection well and the pore pressures at piezometer locations were assumed to achieve steady state by the end of injection period, and SEEP/W software was used to simulate a landfill with conditions similar to the field conditions. Anisotropy and hydr aulic conductivity of landfilled waste were estimated by comparing field data with simulation results. Objective 2. To determine performance of surface infiltration trenches with whole tires as a bedding material Approach. At NRRL, four Surface Infiltrat ion Trenches (SITs) were installed with whole scrap tires as a bedding media. L eachate recirculation was performe d for 16 days such that the leachate level always remained 0.3 m below the top surface of the landfill. The flow rate cumulative volume and t he pressure head (measured at the bottom of trench) we re closely monitored during leachate recirculation. The performance of the SITs was measured in terms of the unit flux (flow rate per unit length), infiltration rate ( unit flux per unit width of trench) and fluid conductance (unit flux per unit pressure head) SEEP/W software was used to simulate the SITs with the conditions similar to the field conditions. The hydraulic cond uctivity of waste was estimated by comparing the field data with the simulation results.

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16 1.5 Organization of Thesis Chapter 2 presents the flow rate and pore pressure results for the field research conducted on a liquids addition well. The chapter also reports the modeling results performed under the conditions similar to the field co nditions. In the end of the chapter, field and modeling results are compared to estimate anisotropy of landfilled waste. Chapter 3 discusses flux, infiltration rate and fluid conductance of the four SITs The flux, infiltration rate and fluid conductance are calculated by the flow -pressure field data based on liquids addition experimen ts on the surface infiltration trenches The chapter also reports the hydraulic conductivity of landfilled waste. The thesis ends with Chapter 4, a summary and a set of concl usions from Chapters 2 and 3, and includes recommendations for future research. Appendix A presents supplemental figures of Chapter 2 and Appendix B presents the photographs for the installation of surface infiltration trenches

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17 CHAPTER 2 ANISOTROPY DETER MINATION OF LANDFILL ED MUNCIAL SOLID WAS TE 2.1 Introduction Due to increased popularity and demand of bioreactor landfill technology, engineers and landfill managers have focused on efficient design and operation of these systems. Townsend (1995), McCreano r and Reinhart (1996), Al Yousfi and Pohland (1998), Maier (1998) and Jain (2005) outlined the design procedures for subsurface moisture addition systems. The important parameters required to design subsurface moisture addition systems are achievable moist ure addition rates, associated pumping pressure requirements, hydraulic conductivity and anisotropy of compacted MSW (Landva et al. 1998 and Jain 2005). For the present study, anisotropy of waste is defined as the ratio of lateral (horizontal) hydraulic co nductivity to vertical hydraulic conductivity. Anisotropy is an important design parameter because radial and vertical impact zones, created due to liquids addition, are closely associated with it While designing a subsurface moisture addition system, the spacing between vertical wells or horizontal injection lines (HILs), is based upon impact zones created by moisture addition and therefore, anisotropy is one of the most important parameter to decide spacing. There have been a number of laboratory and fi eld studies conducted to measure hydraulic conductivity of MSW (Shank, 1993; Townsend 1995; Gabr 1995; Jain 2005; Koerner and Eith 2005; Durmusoglu 2006); however, not much information is available on anisotropy. Landva et al. (1998) researched on two wast e samples, one from a landfill in Canada and the other was artificially fabricated in lab. The waste samples were loaded in two different consolidometers (a cylindrical vessel with an option to apply vertical stress on the loaded sample) to determine horiz ontal and vertical hydraulic conductivities separately through constant head permeability

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18 test. The anisotropy value was reported approximately 8 for the landfill waste sample and ranging from 0.5 to 1 for the artificial refuse sample. Another study was conducted by Hudson et al. (1999) research ing household waste in a compression cell with 2 m diameter and 3 m h eight The compression cell was used to investigate vertical and horizontal hydraulic conductivities separately at a series of vertical stress es ranging from 40 to 603 kPa. The vertical hydraulic conductivity was determined by an upward or downward constant head flow test. The compression cell was modified with 18 new water inlet and outlet ports to estimate horizontal hydraulic conductivity. The t est was performed under constant head at inlet and outlet ports and recording inflow and outflow, and pressure head at different points inside the cell. The inlet and outlet ports were simulated under the conditions similar to the compression cell with MODFLOW, a modeling software; the measured vertical hydraulic conductivity (from constant head test) was assigned to the simulated media. The horizontal hydraulic conductivity was estimated by comparing the modeling results with the test results. The anisotropy ratio was calculated from the estimated hydraulic conductivity values and it was reported in a range of 2 to 5. However, the two studies were performed at lab scale, not at any full scale operating landfill. The anisotropy values, reported by previous studies, may be different from the results obtained from a full scale operating facility because: (a) The waste samples may or may not be the representative samples to estim ate anisotropy as a slight disturbance can change hydraulic conductivity of the waste sample in any direction; (b) The anisotropy results obtained from a small scale compacted cell, created in lab, may or may not represent accurate values because the waste is highly heterogeneous and is unevenly compacted at different places inside an actual landfill.

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19 Kadambala (2009) installed one liquids addition well, surrounded with several piezometers to estimate pore pressures, and estimated lateral and vertical exten t of liquids movement inside the landfill. One of the observations was that liquids did not reach the piezometers installed 3 m below the bottom of the well but did reach the piezometers installed at an elevation similar to the bottom of the well, which showed that landfilled waste was highly anisotropic. However, Kadambala (2009) focused on extent of liquids movement and did not report any anisotropy values. The present study used the same liquids addition system and reports the results of an experiment de signed to measure the degree of anisotropy of MSW at different depths inside the landfill. The research included addition of liquids into the vertical well and monitoring flow rate and injection pressure. Several piezometers were installed around the verti cal liquids addition well and pore pressures at the piezometer locations were continuously monitored until steady approximate state was approached. Another part of the research was to simulate the vertical well with conditions similar to the field conditio ns. The modeling results were compared with the field data to estimate MSW anisotropy. Hydraulic conductivity of MSW was also eva luated through this study. 2.2 Materials and Methods 2. 2.1 Experimental Approach The experiment included field research along with modeling to estimate anisotropy of landfilled waste. In the field research, liquids addition was performed through a buried vertical well installed at New River Regional Landfill (NRRL). The vertical well was used to add liquids in the past (Kadambal a 2009) and therefore the area was already wetted. Several piezometers were installed around the injection well to monitor pore pressures. The liquids addition was performed under constant injection head. The flow rate, cumulative volume and pore pressures were recorded on an hourly basis during the liquids addition. SEEP/W software was used as a

PAGE 20

20 modeling tool to simulate the landfill conditions similar to the field research. The modeling was performed under a constant head and nine different simulations we re performed by considering three different lateral hydraulic conductivity values and three different anisotropy values. The steady state flow rate and the steady state pore pressures were calculated for each of the nine simulations. The steady state flow rates were plotted against steady state pore pressures for all the nine simulations. Anisotropy was estimated by plotting the steady state field research results (i.e., flow rate and pore pressures) on the plots generated through simulations results. 2.2.2 Field Experiments Kadambala (2009) installed two vertical liquids addition wells in Cell 4 of the NRRL. The length (depth) of each well was 12.0 m with the lower 10.5 m screened. Approximately10.5 m of compacted waste was present below the bottom of verti cal well. Ninety vibrating wire piezometers were installed in the 18 piezometer wells at five different depths. Figure 2 1 show s the plan view locations of two moisture addition wells and 18 piezometer wells. At each piezometer well location, five piezomet ers were installed at diffe rent depth as shown in Figure 2 2. On top of the installed wells, 4.8 m of compacted waste was placed. Other construction details can be found in Kadambala, 2009. As part of the earlier injection tests, approximately 1,422 m3 of liquids were added through the vertical well 2. For the present study, the same vertical well was used to add liquids. The piezometers located at a distance of 1.5 m from the liquids addition well (i.e., piezometers at C, F, G and J piezometer well locatio ns) were used to monitor pore pressure. However, out of the twenty installed piezometers, only nine piezometers were in working condition before the liquids addition was started. Liquids addition was started on Feb. 5, 2010. The goal was to find an approximate steady state flow rate into the injection well at a constant injection pressure, and to measure the resulting pore pressures. Liquids addition was performed intermittently for 11 days and

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21 continuous injection (24 hour injection) was performed for 3 days. Approximately 56 m3 of leachate was added in the first 11 days and approximately 95 m3was added in rest of the three days. The injection pressure was maintained constant at 16.4 m of water column (measured at the bottom of the recirculation well) for the period of continuous injection by adjusting the flow control valve. The pore pressures at the piezometers located at a distance of 1.5 m from the injection well were used for the anisotropy calculation. The flow rate (in the well) and pore pressures at the piezometer locations were considered to approach steady state by the end of the injection period. 2.2.3 Modeling SEEP/W software ( GEO SLOPE International Ltd., Calgary, Canada ) was used as a modeling tool to simulate the liquids addition well with conditions similar to the field conditions. SEEP/W has been used in the past to simulate subsurface moisture m ovement (Woyshner et al. 1995, Ardejani et al. 2006 and Jain et at. 2010). The simulation work was carried out to find steady state flow rate in the simulated liquids addition well at a constant injection pressure (i.e., 16.4 m of water column measured at bottom of the well), and to find steady state pore pressures in the simulated landfill at the same locations where piezometers were located in the fi eld research. T he landfill depth and width were adopted as 50 m and 100 m respectively for modeling purpose The media/waste in the simulated landfill was divided in to 8 differ ent layers as shown in Figure 2 3 The layers were created such that the middle of layers 2 through 6 contains one piezometer location each at a distance of 1.5 m from the injection well. All the layers had the same waste characteristics (listed in Table 2 1) except hydraulic conductivity. The hydraulic conductivity of waste decrease s with increase in depth (Bleiker et al. 1993, Powrie et al. 1999 and Jain et al. 2006) and therefore, the media was assigned hydraulic conductivity as a function of

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22 depth. The layers of the media were assigned different hydraulic conductivities based on th e plot generated by Powrie and Beaven (1999) i.e., the plot showing hydraulic conductivity as a function of depth. The hydraulic conductivity (Kr) for different layers was calculated with respect to hydraulic conductivity of the layer 2 ( Kr2) as listed in Table 2 2. The waste was assumed to be homogenous porous medium. T he parameters related with the waste characteristics are listed in Table 2 1. Nine different simulations were conducted by taking three different values of hydraulic conductivity of layer 2 (Kr 2), i.e., 103, 104 and 105 cm/s, and three different values of anisotropy, i.e., 1, 10 and 100. The injection pressure head was kept same as the field conditions for all the simulations (i.e., 16.4 m, measured at the bottom of the well). For conducting simulations, the axis -symmetric case was considered. A boundary condition with a total head (pr essure head + elevation) of 49. 6 m was defined along the screened length of the vertical well. The pressure head at the bottom of the vertical well was defined as 16.4 m as the bottom of the well was at an elevation of 33.2 m (as shown is Figure 2 3 ). The landfill top and bottom were assumed as zero flux boundaries. The compacted waste is covered with a layer of compacted clay to promote runoff; hence moi sture due to rainfall does not penetrate into the landfill. Therefore, the top of the landfill can be assumed as a zero flux boundary (Jain et al. 2010) In reality, the bottom of the landfill is not a zero flux boundary as the leachate collection system i s installed at the bottom of the landfill. However, to support the assumption of zero flux boundary, enough space was provided below the bottom of the vertical well so that the pore pressure at all piezometer locations reached steady state before the moist ure reached the bottom of the simulated landfill. Moreover, enough space was provided in lateral direction of the simulated landfill so that added moisture did not reach the outer boundary of the

PAGE 23

23 waste (Jain et al. 2010) An initial moisture content of 15% (v olume /v olume ) was assigned for the simulation purpose. In the horizontal direction, discretization of 5 cm for 0 m discretization of 1 .2 m was used for 0 0 cm for 30 m 4 5 m. An initial time step of 105 sec was adopted for all the simulations with a multiplication factor of 1.5. As the time reached 3600 sec time, a new time step of 3600 sec was u sed for rest of the simulation until the pore pressures at piezometer locations reached steady state. Another set of 9 simulations was conducted by assigning a single value to the whole media/waste. For this scenario, the waste/media constituted of a sing le layer with the same properties throughout. Nine different simulations were conducted by taking three different Kr values (103, 104 and 105 cm/s) and three different values of anisotropy (1, 10 and 100). All other parameters besides the hydraulic conductivity remained same as the previous set of simulations. The goal behind this second set of simulations was to evaluate the magnitude of change in the results for the two scenarios. It should be noted that the results of the first scenario are used for reporting purpose because this scenario presented the condition close to the landfill conditions, i.e., hydraulic conductivity decreasing with increase in depth. 2.2.4 Anisotropy Estimation The simulation results were plotted by taking steady state flow rate along the xaxis and steady state pore pressures along y axis for the set of nine different simulations. As the pore pressures changed with change in the landfill depth for the set of simulations, three different plots were generated for three diffe rent landfill depths. The points with the same anisotropy value were fitted on a best fit curve. Similarly the points with the same lateral hydraulic conductivity were also fitted on a best fit curve. Therefore, each plot represented three different

PAGE 24

24 anisot ropy value curves and three different lateral hydraulic conductivity value curves. For each piezometer location, the observed steady state field parameters (i.e., flow rate and pore pressure) were plotted on the simulation plot to estimate the anisotropy value at the respective depth of the piezometer. In the end, a last simulation was carried out to check the reported results. The anisotropy results and the hydraulic conductivity results were used to assign anisotropy and hydraulic conductivity for the me dia. The media was divided into 8 different layers and all other conditions were kept similar to the conditions for the first scenario. A graph was generated by taking pore pressure results at different depths along yaxis and landfill depths along xaxis. A curve was generated by joining all the pore pressure points at different depths. The graph provided a check for the results as all the field data points were supposed to fall on the curve generated through the simulation results. 2.3 Results and Discussions 2.3.1 Field Results Liquids addition was performed at a pressure head of 18.1 m (measured from the bottom of the well) during the first five days. The associated flow rate dropped from 2.4 103 m3/s to 8.0 04 m3/s. For the next six days the liquids addition was performed at a pressure head of approximately 16.4 m and the associated flow rate dropped from 8.0 104 m3/s to 3.8104 m3/s. The liquids were added continuously (24 hours) for rest of the three days at a constant pressure head of 16.4 m a nd the associated flow rate remained stable, i.e., 2.7104 m3/s, throughout the three days period. Therefore, by the end of the injection period this flow rate, i.e., 2.7104 m3/s was assumed as approximate steady state flow rate at pressure head of 16.4 m. Kadambala (2009) researched on the same liquids addition well and during the last ten days of his research, flow rates were reported in a range of 2.0104 m3/s to 6.0104 m3/s. The

PAGE 25

25 associated pressure head was reported in a range of 13.8 m to 19.8 m water column, measured at the bottom of the well. However, by looking at his data closely the flow rate of 3.0104 m3/s was observed at approximately 16.4 m pressure head and therefore, the flow rate value of 2.7104 m3/s is close to the expected value. Jain (2005) researched on the same landfill and installed 134 vertical wells with different depths. From the plots provided by Jain (2005), the steady state flow rate was found in a range of 7.0105 m3/s to 1.2104 m3/s at approximately 15 m pressure hea d. As liquids were added at a pressure head greater than 15 m for the present research, therefore higher flow rate was expected than the range of 7.0105 m3/s to 1.2104 m3/s. Figure 2 4 shows change of pore pressure at various piezometer locations wit h respect to time. The piezometers located at a landfill depth of 7.8 m responded quickly with liquids addition as compared to the piezometers located at landfill depths of 10.8 m and 13.8 m respectively. However, by the end of liquids addition pore pressures at all the piezometer locations were observed relatively stable than the earlier period of liquids addition and therefore, it was assumed that the pore pressures reached approximate steady state, i.e., pseudo steady state. The average pseudo steady sta te pore pressures at landfill depths of 7.8 m, 10.8 m and 13.8 m were o bserved as 3.85 m, 4.4 m and 5.5 m water column respectively (listed in Table 2 3). The piezometers located at a depth of 19.8 m did not respond to leachate recirculation which supports anisotropic nature of landfill waste with an anisotropy value of greater than one. 2.3.2 Simulation Results The simulation results for the first scenario (hydraulic conductivity decreasing as a function of depth) are presented by three plots, at differe nt landfill d epths, as shown in the Figure 2 5. Plot 2 5 (a) shows nine data points for nine different simulations with flow rates on the xaxis and pore pressures (at a landfill depth of 7.8 m and at a distance of 1.5 m from the well) on

PAGE 26

26 the y axis. Thre e different anisotropy value curves (for a = 1, 10 and 100) were generated by fitting the same anisotropy points on a best fit curve. Similarly, three different lateral hydraulic conductivity curves (Kr 2=105, 104 and 103 cm/s) were generated by combinin g same hydraulic conductivity point s on a best fit curve. Figure 25 (b) was plotted similarly with pore pressures (y axis) correspond to the middle of layer 3, i.e., 10.8 m landfil l depth. Similarly the Figure 2 5 (c) w as generated with pore pressure valu es defined at middle of layer 4, i.e., 13.8 m landfill depth. The simulation results for the second scenario (hydraulic conductivity independent of depth) are presented by three plots, at different landfill d epths, as shown in the Figure 2 6. The plots we re generated similarly as the Figure 2 5 but the hydraulic conductivity curve values were same at all the three depths, i.e., Kr=105, 104 and 103 cm/s. Figures 2 5 and 26 reflected that the pore pressures and flow rates increased with the increase in anisotropy and hydraulic conductivity. It was expected because the higher is the hydraulic conductivity, the media/waste can conduct higher amount of liquids resulting increa se in the pore pressures. Increase in the value of anisotropy results increased flow rates in the lateral/horizontal direction as compared to vertical direction. Therefore the pore pressures at the piezometer locations, i.e., 1.5 m away from the liquids ad dition source, increased because of the increased flow in the lateral/horizontal direction. From the results, it was observed that the pore pressures were higher for the first scenario as compared to the second scenario. It was expected in as the hydrauli c conductivity decreased with depth in the first scenario. Because of the lower hydraulic conductivity in the regions below the bottom of the liquids addition well, liquids starts building up in the upper regions as the bottom layers acts as a comparativel y impermeable media. However, in second scenario the media was assigned same hydraulic conductivity throughout which resulted in uniform

PAGE 27

27 movement of liquids in the vertical direction and no liquids build up was expected. Because of this reason the pore pre ssure values in the first scenario were higher as compared to the second scenario. Another observation was that the flow rates were slightly higher for the second scenario as compared to the first. It can be justified based on the same hydraulic conductivi ty in the second scenario. Because of the same hydraulic conductivity the media conducted higher amounts of liquids as compared to the scenario where hydraulic conductivity decreased with increase in depth. 2.3.3 Anisotropy Estimation The anisotropy of the landfilled waste was estimated by plotting the pseudo steady state field results (flow rates and pore pressures) on the simulation plots at different landfi ll depths as shown in Figures 2 5 and 2 6. The anisotropy values were estimated from the anisotropy curves generated through simulation results. The anisotropy re sults at different landfill depths are listed in Table 2 3 for the first scenario and in Table 2 4 for the second scenario and a comparison is shown in Figure 2 7 For the first scenario, anis otropy values were estimated in a range of 2 to 100 with average value of 36. The anisotropy values were estimated in a range of 90 to 100 with an average value of 95 at 7.8 m depth, 7 to 30 with an average value of 16 at 10.8 m depth, and 2 to 8 with an a verage value of 5 at 13.8 m depth. Similarly, the lateral hydraulic conductivity for layer 2 (Kr 2) was estimated in a range of 3.4 04 cm/s to 4.0104 cm/s with an average value of 3.7104 cm/s For the second scenario, anisotropy value s were estimated in a range of 8 to 105 with average value of 44. The anisotropy values were estimated in a range of 95 to 105 with an average value of 100 at 7.8 m depth, 9 to 50 with an average value of 26 a t 10.8 m depth, and 8 to 20 with an average value of 14 at 13.8 m depth. Similarly, the lateral hydraulic conductivity (Kr) values were estimated in a range of 2.5104 cm/s to 3.0104 cm/s with an average value of

PAGE 28

28 2.8104 cm/s. One of the observations from the results was that the anisotropy of landfilled waste sho wed decreas ed with the increase in depth. The anisotropic nature of waste is a result of the fibrous nature of waste along with the waste compaction techniques, i.e., waste is compacted in layers As the landfill depth increases, the layers come closer because of the self weight of waste This compaction of laye rs reduces hydraulic conductivity on a higher scale as compared to vertical hydraulic conductivity and therefore, the anisotropy decreases with depth. The anisotropy values were estimated higher for the second scenario as compared to the first scenario. It was resulted because of the higher pore pressures for the simulations of the second scenario as discussed in the previous section. Howev er, the hydraulic conductivity decreases with increase in landfill depth ( Bleiker et. al. 1993 and Jain 2005). Therefore, the first scenario represented better estimates of the anisotropy as compared to second scenario because the media/waste was assigned hydraulic conductivity decreasing as a function of depth for the fi rst scenario simulations and therefore, the results of the first scenario are used for reporting the anisotropy values. The anisotropy values determined through the present research are hi gher than the values reported by Landva et al. (1998) and Hudson et al. (1999) Landva et al. (1998) researched on waste samples collected from some landfills in Canada and reported anisotropy value of 8. Hudson et al. (1999) conducted research on a waste sample in a 2 m diameter and 3 m high column and anisotropy was reported in a range of 2 to 5. The higher anisotropy values estimated through the present study can be justified as both the studies ( Landva et al., 1998 and Hudson et al. 1999) were carried o ut on a lab scale and the conditions differ inside a full scale bioreactor landfill. Another study was conducted by Tchobanoglous et al. (1993) and suggested 1010 m2 for landfilled waste permeability in the horizontal direction, and 1012 1011 m2 in ver tical direction

PAGE 29

29 but the source did not reported any anisotropy values. Based on the suggested permeability values, the anisotropy ratio is expected to be in a range of 10 to 100, and the average anisotropy value determined through the present research is a lso found in the expected range. The hydraulic conductivity of landfilled waste at 7.8 m depth w as estimated in the range of 3.4 04 cm/s to 4.0104 cm/s. In the previous studies, the hydraulic conductivity values have been reported in the range of 6.7 105 cm/s to 9.8104 cm/s by Shank 1993; 105 cm/s to 103 cm/s by Gabr 1995; 2.9104 cm/s to 2.9103 cm/s by Jang et al., 2002; 5.4106 cm/s to 6.1105 cm/s Jain 2005; 1.2102 cm/s to 6.9102 cm/s by Koerner et al., 2005; and 1.2104 cm/s to 1.2102 cm/s by Durmusoglu 2006. Therefore the estimated values of the hydraulic conductivity falls in the range of the reported values of the hydraulic conductivity of landfilled MSW. 2.3.4 Verification of Results For modeling purposes the wast e was assumed to be homogeneous media but the landfilled waste is heterogeneous in nature because the municipal solid waste consists of different sizes and types of wastes. Also the landfill gas resistance was assumed zero for modeling purpose however, ga s may significantly impact the liquid phase flow (Powrie et al. 2008). For the present research, steady state was assumed near the end of liquids addition period whereas the simulations results were the steady state results. Because of these limitations an d assumptions, the model results would not truly match field results but rather provides some estimates to determine anisotropy of landfilled waste. To verify results, a simulation was carried out with anisotropy and hydraulic conductivity results assigned as the media properties for the simulation purpose. The layer 2 of the media was assigned hydraulic conductivity of 3.7104 cm/s and hydraulic conductivities for rest of the layers were assigned on the basis of Table 2 2. The layers 2, 3 and 4 were assigned anisotropy values of 95, 16 and 5 respectively. The anisotropy values for layers 1, 5, 6, 7 and 8 were

PAGE 30

30 assumed as 95, 3, 2, 1 and 1 respectively. All other conditions were kept similar to the conditions of first scenario simulations. The simulation res ults were plotted by taking pore pressures along y axis and landfill depth along xaxis as shown in Figure 2 8. The fi eld data points were plotted on the plot generated through simulation res ults. The field data points lay on the curve which showed that the modeling results (used as input parameters for the last simulation) represented the best set of anisotropy and hydraulic conductivity values for the different layers of the simulated media. 2.4 Conclusions This study reports the values o f anisotropy of landfilled MSW by comparing field results of liquids addition with simulation results. The anisotropy value was estimated in a range of 2 to 100 and decreased with increase in landfill depth with an average value of 36. The anisotropy value was reported in a range of 2 to 8 by Landva et al. (1998) and Hudson et al. (1999). Therefore, the average anisotropy value is found higher than the values reported by the previous studies. This can be justified as both the studies were carried out at a l ab scale and the conditions differ inside a full scale bioreactor landfill. The radial and vertical impact zones, created due to liquids addition, are closely associated with the anisotropy values associated with landfilled MSW. The higher is the anisotropy value, the longer will be the radial impact zone. In a subsurface moisture addition system the spacing between vertical wells or horizontal injection lines is based upon radial and vertical impact zones created by moisture addition. The spacing between l iquids addition vertical wells and/or horizontal lines is a critical parameter to know because if it is shorter than the optimum value then the associated cost increases and if it is longer than the optimum value than there will be dry areas in between ver tical wells and/or horizontal lines. Therefore, the anisotropy values estimated through this study will help landfill designers to design effective liquids addition system by calculating optimum spacing. The

PAGE 31

31 associated lateral hydraulic conductivity was fo und in a range of 3.4 04 cm/s to 4.0104 cm/s with an average value of 3 .7 04 cm/s. The value falls in the range of hydraulic conductivities reported by previous studies.

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32 Table 2 1 Parameters used for the numerical modeling Parameter Value Hydraulic Conductivity for layer 2 (K r2 ) ( c ms 1 ) 10 3 10 4 and 10 5 Anisotropy Ratio 1, 10 and 100 Van Genuchten parameter, a 1 (m 1 of water column) Van Genuchten parameter, n 4 Van Genuchten parameter, m 0.75 Porosity (Vol/Vol) a 0.5 0 m (KPa 1 ) 3 10 3 Landfill Depth, (m) 50 Well Radius (m) 0.3 Well Depth (m) 12 Screen Length (m) 10. 5 Injection Pressure (m) 16.4 a 50% porosity is assumed on the basis of the porosity range (45.5% to 55.5%) determined by Hudson et. al. (2004). Table 2 2 Hydraulic conductivity of different layers with respect to layer 2 Layer Average Depth (m) Hydraulic Conductivity (m/s) a Lateral Hydraulic Conductivity w.r.t. layer 2 b 1 3.2 8.910 5 1.25 K r2 2 7.8 7.110 5 K r2 3 10.8 6.010 5 K r2 / 1.18 4 13.8 4.710 5 K r2 / 1.51 5 16.8 3.510 5 K r2 / 2.03 6 19.8 2.510 5 K r2 / 2.84 7 25.7 6.510 6 K r2 / 10.92 8 40.0 5.010 7 K r2 / 178 a Vertical hydraulic conductivity, calculated on basis of hydraulic conductivity as a function of depth of landfi lled waste plot by Powrie and Beaven (1999) b The vertical hyd. conductivity ratio at two different depths will be equal to the ratio of lateral hyd. conductivity as all the layers have same anisotropy.

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33 Table 2 3 Comparison of field data and simulation data for the first scenario Piezometer Well Depth of Piezometer Inside Landfill (m) Steady State Pore Pressure, m water column (fiel d data)a Anisotropy (comparing field data with simulation data)b Hydraulic Conductivity, Kr 2 (comparing field data with simulation data)b C 7.8 3.9 100 4.010 4 cm/s J 7.8 3.8 90 4.010 4 cm/s C 10.8 4.4 10 3.7 0 4 cm/s G 10.8 4.1 7 3.5 0 4 cm/s J 10.8 4.7 30 4 .0 0 4 cm/s C 13.8 5.2 2 3.6 0 4 cm/s G 13.8 5 .8 8 3.4 0 4 cm/s a From Figure 2 4. b Calculated by overlapping steady state flow rate and steady state pore pressure (at piezometer locations; Figure 2 4) with t he simulation results (Figure 2 5). Table 2 4 Comparison of field data and simulation data for the second scenario Piezometer Well Depth of Piezometer Inside Landfill (m) Steady State Pore Pressure, m water column (field data)a Anisotropy (comparing field data with simula tion data)b Hydraulic Conductivity, Kr (comparing field data with simulation data) b C 7.8 3.9 105 3.010 4 cm/s J 7.8 3.8 95 3.010 4 cm/s C 10.8 4.4 2 0 2.710 4 cm/s G 10.8 4.1 9 2.510 4 cm/s J 10.8 4.7 50 3.010 4 cm/s C 13.8 5.2 8 2.710 4 cm/s G 13.8 5 .8 20 2.510 4 cm/s a From Figure 2 4. b Calculated by overlapping steady state flow rate and steady state pore pressure (at piezometer locations; Figure 2 4) with t he simulation results (Figure 2 6).

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34 A B Figure 2 1 A ) New River Regional Landfill (NRRL) showing the area which contains the moisture addit ion and the piezometer wells; B ) the close up of the liquids addition wells and piezometer wells in the research area

PAGE 35

35 Figure 2 2 Cross Sectional View of the liquids addition wells and the piezometer wells

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36 Figure 2 3 Simulated landfill showing different layers of the media/waste

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37 Pore Pressure (m water column) 1 2 3 4 5 6 Piezometer located in Piezometer Well "C" Piezometer located in Piezometer Well "J" Pore Pressure (m water column) 1 2 3 4 5 6 Piezometer located in Peizometer Well "C" Piezometer located in Piezometer Well "G" Piezometer located in Piezometer Well "J" Days (Day 1: Feb 5, 2010) 0 2 4 6 8 10 12 14 Pore Pressure (m water column) 2 3 4 5 6 Peizometer located in Piezometer Well "C" Peizometer located in Piezometer Well "G" B A C Figure 2 4 Pore Pressure Vs Time for the piezometers located at A ) 7.8m depth; B) 10.8 m depth; C ) 13.8 m depth; (from field data)

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38 Pore Pressure (m) 0 2 4 6 8 Anisotropy=1 Anisotropy= 10 Anisotropy= 100 Kr2 = 10-5 cm/s Well "C" Piezometer (Field Data Point) Well "J" Piezometer (Field Data Point)Kr2 = 10-4 cm/s Kr2 = 10-3 cm/s Pore Pressure (m) 0 2 4 6 8 Anisotropy=1 Anisotropy= 10 Anisotropy= 100 Kr2 = 10-4 cm/s Kr2 = 10-3 cm/s Kr2 = 10-5 cm/s Well "C" Piezometer (Field Data Point) Well "J" Piezometer (Field Data Point) Well "G" Piezometer (Field Data Point) Flowrate (m3/s) 1e-6 1e-5 1e-4 1e-3 1e-2Pore Pressure (m) 0 2 4 6 8 Anisotropy=1 Anisotropy= 10 Anisotropy= 100 Well "C" Piezometer (Field Data Point) Well "G" Piezometer (Field Data Point) Kr2 = 10-5 cm/s Kr2 = 10-4 cm/s Kr2 = 10-3 cm/s A B C Figure 2 5 Plots generated through modeling results for first scenario A ) at landfill depth of 7.8 m; B) at landfill depth of 10.8 m; and C ) at landfill depth of 13.8 m. The plots also include field data points

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39 Pore Pressure (m) 0 2 4 6 8 Anisotropy=1 Anisotropy= 10 Anisotropy= 100 Well "C" Piezometer (Field Data Point) Well "J" Piezometer (Field Data Point)Kr = 10-5 cm/s Kr = 10-4 cm/s Kr = 10-3 cm/s Pore Pressure (m) 0 2 4 6 8 Anisotropy=1 Anisotropy= 10 Anisotropy= 100 Kr = 10-5 cm/s Well "C" Piezometer (Field Data Point) Well "J" Piezometer (Field Data Point) Well "G" Piezometer (Field Data Point) Kr = 10-4 cm/s Kr = 10-3 cm/s Flowrate (m3/s) 1e-6 1e-5 1e-4 1e-3 1e-2 Pore Pressure (m) 0 2 4 6 8 Anisotropy=1 Anisotropy= 10 Anisotropy= 100 Well "C" Piezometer (Field Data Point) Well "G" Piezometer (Field Data Point) Kr = 10-5 cm/s Kr = 10-4 cm/s Kr = 10-3 cm/sA B C Figure 2 6 Plots generated through modeling results for second scenario A) at landfill depth of 7.8 m; B ) at landfill depth of 10.8 m; and C ) at landfill depth of 13.8 m. The plots also include field dat a points

PAGE 40

40 Landfill Depth (m) 7 8 9 10 11 12 13 14 15 Anisotropy 0 20 40 60 80 100 Mean Value (Scenario 1) Mean Value (Scenario 2) Figure 2 7 Comparison of anisotropy results for two different scenarios

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41 Landfill Depth (m) 7 8 9 10 11 12 13 14 15 Pore Pressure (m water column) 0 1 2 3 4 5 6 Field Data Simulation Results Figure 2 8 Comparison of pore pressures field results with results of the simulation carried out for the verification of results

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42 CHAPTER 3 PERFORMANCE EVALUATI ON OF SURFACE INFILT RATION TRENCHES WITH WHOLE TIRES AS A BED DING MEDIA 3.1 Introduction Liquids addition is the most important tool for bioreacting landfilled waste. Surface and s ubsurface liquids addition systems are two of the most commonly practiced systems. Horizontal injection lines and vertical wells are two examples of subsurface liquids additions systems and considerable research has been conducted on various aspects of these systems ( McCreanor et al. 1996 and 2000, Townsend et al. 1998, McCreanor 1998, Haydar et al. 2004 and 2005, Jain 2005, Larson 2007, Kadambala 2009). Surface infiltration ponds and surface infiltration trenches are two types of surface liquids addition systems; Townsend et al. (1995) reported results from surface infiltration ponds but after this study, little research has been conducted on surface infiltration sys tems. Townsend et al. (1995) conducted research on four surface infiltration ponds and oper ated the system for 28 -month period. The performances of the infiltration ponds were reported in terms of the infiltration rates, defined as flow rate per unit wetted bottom area. The infiltration rates were reported in a rage of 6.0108 m/s to 9.0108 m/s Larson (2007) researched on 16 subsurface horizontal injection lines (HILs) with different bedding materials around the perforated pipe. The performance the HILs was reported in terms of fluid conductance, defined as pseudo steady state flow rate per unit applied pressure per unit length. The performances of HILs were reported in a range of 1.9107 m/s to 7.5107 m/s with an average of 5.3107 m/s. Kumar (2009) researched on 31 HILs with different bedding materials and reported fluid conductance va lues in a range of 1.6107 m/s to 3.4106 m/s with an average of 7.8107 m/s. This study aims to continue and build upon these past studies by examining the performance of

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43 surface infiltration trenches (SITs) and comparing the results with these studie s on surface and subsurface liquids addition systems. Another aspect of this research is to provide an innovative way to use whole scrap tires a bedding material. The management of whole scrap tires is a challenge in solid waste management field. Approxim ately 290 million scrap tires are generated annually and approximately 275 million scrap tires were present in stockpiles in 2003. The stockpiled tires pose threat to the environment because of fire breakouts and vectors. Tire fires typically cause air, su rface water, soil, groundwater, and residual contamination. Scrap tires are managed by using tires as fuel for incinerators, and land application besides stockpiling. Another option for the management of scrap tires is to use shredded tires as a bedding ma terial and this option has been practiced at some operating landfills (Larson 1997, Kumar 2009). However, processing is required for the shredded tires and thus, the use of whole tires provides an economical and environmental benefit. 3.2 Materials and Me thods 3.2.1 Site Description The research was carried out in Cell 5 at the New River Regional Landfill (NRRL) located in Union County, Florida. The NRRL receives 800 metric tons per day of waste consisting of mixed residential and commercial waste. The landfill currently consists of five class I contiguous lined landfill cells totaling approximately 25 hectares. Cell 5 is approximately 6.9 hectares in area and is equipped with a double liner system. The average height of the waste from the surface of th e landfill to the leachate collection system at the time of construction was approximately 13 m. The density of the landfilled waste was approximated to be 710 kg/m3. A clayey -sandy soil mined on site was used as daily cover. Leachate recirculation was per mitted in Cell 5 at the time of operation; however the maximum amount of leachate recirculated should

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44 not have exceeded a total volume 122 m3 per day. A detailed description of the site and the bioreactor can be found elsewhere (Jain 2005 and Kadambala 200 9). 3.2.2 Installation and Operation of SITs Four surface infiltration trenches were installed in Cell 5 of the NRRL as shown in Figure 3 1. The trenches 1 and 2 were 45 m long, the trench 3 was 30 m long and the trench 4 was 15 m long. The trenches were installed inside 1 m by 1.2 m trenches excavated in the waste with an excavator. Inside the excavated trench 7.6 cm perforated HDPE pipe was installed surrounded with the whole scrap tires arranged in the configuration shown in Figure 3 2. The automobile t ires with size less than 1 m were used for the research. The whole tires were tied together with 6.35 mm nylon rope to ensure the stability of the trench. A solid section of 7.6 cm HDPE pipe was welded to each end of the perforated liquids injection pipe a nd was extended to the top of the trench and out to the surface. These solid sections of pipe were connected to a leachate recirculation hydrant on one end and capped with a Fernco cap on the other end as shown in Figure 3 2. The trench was covered with a layer of geotextile and 0.3 m of compacted clay was placed on top of it. A flow control valve (7.62 cm butterfly), a flow meter (SeaMetrics IP80 flow meters) were installed at the hydrant connection to control the flow rate and to monitor flow rate at each trench. The hydrostatic head was measured by dropping a water sensor through the solid HDPE pipe at the ends of the trench by removing the Fernco cap. The leachate recirculation was performed during the operational hours of the landfill for 16 days start ing from May 27, 2010. The hydrostatic head was always kept 0.3 m below the top surface of the landfill to avoid the seeps. The flow rate, cumulative volume and the hydrostatic head were manually recorded on hourly basis during the leachate recirculation. The flow rate was assumed to reach steady state by end of the recirculation period.

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45 The performance of the SITs was measured in terms of the unit flux (q), infiltration rates (I) and the fluid conductance ( ) given by following equations: = (3 1) = (3 2) = (3 3) Where, q= Sectional Flux of SIT, m2/s; Qs = Steady state flow rate, m3/s; L = Length of SIT, m; I= Infiltration Rate, m/s; W= Width of SIT, m (constant value of 1 m for all the SITs); = Fluid conductance, m/s; and P= Pres sure head, m. 3.2.3 Modeling SEEP/W software (GEO SLOPE International Ltd., Calgary, Canada) was used as a tool to simulate landfill with the SITs as a liquids addition source. The simulation work was carried out with the goal to find steady state unit flow rate (flux) in the SITs at a constant injection pressure (i.e., 0.9 m of water column measured at bottom of the trench). Steady state unit flow rates, through field results and through simulation results, were compared to find hydraulic conductivity of compacted waste. The landfill depth and width were adopted as 50 m and 40 m respectively for modeling purposes. The waste was assumed to be homogenous porous medium. The elevation of the bottom of the trench was fixed at 35 m. The axis -symmetric case was considered and therefore half of the cross section (along width) was considered as a liquids addit ion source as shown in Figure 3 3. The parameters related with the waste characteristics are listed in Table 3 1. Th e clay layer, shown in Figure 3 3, wa s assigned hydraulic conductivity of 105 cm/s. All other properties for the clay layer were assumed to be similar with the waste properties. Nine different simulations were conducted by taking three different values of horizontal hydraulic conductivity

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46 (Kx), i.e., 102, 103 and 104 cm/s, and three different values of anisotropy, i.e., 1, 10 and 100. The anisotropy of waste was defined as ratio of the horizontal hydraulic conductivity (Kx) to the vertical hydraulic conductivity (Ky). The injection pressu re head was kept same as the field conditions for all the simulations (i.e., 0.9 m, measured at the bottom of the trench) A boundary condition with total head (pressure head + elevation) of 35.9 m was defined along the width and the effective depth of the SIT (i.e. bottom 0.9 m of the trench). The landfill top and bottom were assumed as zero flux boundaries. The top of the landfill was assumed as a zero flux boundary as moisture due to rainfall does not penetrate into the landfill because a layer of compac ted clay was installed on the top of compacted waste, which promoted runoff. In reality, the bottom of the landfill is not a zero flux boundary as the leachate collection system is installed at the bottom of the landfill. However, to support the assumption of zero flux boundary, enough space was provided below the bottom of the SIT so that the flow rate through the trench reached steady state before the moisture reached the bottom of the simulated landfill (Jain et al. 2010) Moreover, enough space was prov ided in lateral direction of the simulated landfill so that added moisture did not reach the outer boundary of the waste. An initial moisture content of 15% (v olume /v olume) was assigned for the simulation purpose (Jain et al. 2010) In horizontal direction, discretization of 5 cm for 0 m 50 cm for 5 m of 1.2 m was used for 0 cm for y 5 sec was adopted for all the simulations with a multiplication factor of 1.5. As the time reached 3600 sec time, a new time step of 3600 sec was used for rest of the simulation until the unit flow rate through the trench reached steady state.

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47 3.2.4 Hydraulic Conductivity Estimation The simulation results were plotted by taking hydraulic conductivity values along the xaxis and steady state flux along y axis for nine different simulations. The points with the same anisotropy value were fitted on a best fit curve and therefore, the plot represented three different anisotropy value curves. The observed pseudo steady state flux values (from field data) were plotted on the simulation plot to estimate the hydraulic conductivity of the landfilled waste. 3.2.5 Model Limitations For the modeling purpose the waste was assumed to be homogeneous media but the landfilled waste is heterogeneous in nature. Also the landfill gas resistance was assumed zero for modeling purpos e however, gas may significantly impact the liquid phase flow (Powrie et al. 2008). The model simulated the scenario where liquids addition system was operated on a continuous basis; however, the SITs were operated on an intermittent basis. Because of th ese limitations and assumptions, the model results would not truly match field results but rather provides some close estimates to determine hydraulic conductivity of landfilled waste. 3.3 Results and Discussion 3.3.1 Performance of SITs The leachate reci rculation was performed for 16 days and approximately 365 m3 of liquids were added into the four SITs. Figures 3 4 and 3 5 show the change of flux and pressure head for the four SITs with respect to time and cumulative volume. The pressure increased in the earlier stage of liquids addition and it was kept constant in the later stage of the experiment by adjusting the flow control valve. The sectional flux was higher in the earlier stage of liquids addition and it decreased continuously during the remaining period of liquids addition. However the flux values did not change significantly near the end of liquids addition and therefore, the sectional flux values were assumed to reach pseudo steady state at the end of liquids addition. The pseudo

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48 steady state sec tional flux value for 15 m, 30 m, 45 m and the second 45 m trench was found 8.0106 m2/s, 8.8106 m2/s, 1.1105 m2/s and 9.1106 m2/s respectively. The magnitude of pseudo steady state infiltration rates (I) remained as the sectional flux (q) because t he width of all four SITs was 1 m. The fluid conductance values were observed in a range of 8.9106 m/s to 1.2105 m/s with an average value of 1.0105 m/s. Townsend et al. (1995) reported infiltration rates ranged from 6.0108 m/s to 9.0108 m/s. The surface infiltration rates, through the present research, were observed in a range of 8.0106 m/s to 1.1105 m/s which is 120 to 130 times higher than the values of infiltration rates reported by Townsend et al. (1995). Therefore the performance of the SITs was observed better than the performance of the infiltration ponds. Townsend et al. (1995) added approximately 3 m3/m2 (cumulative volume added/surface area of ponds) of liquids in a period of 140 to 385 days whereas for the present research 2.7 m3/m2 (cumulative volume added/surface areas of SITs) in a period of 16 days. Therefore the SITs conducted approximately the same amount of liquids but in smaller duration of time which supports the higher infiltration rates for the present research. Townsend et al. (1995) researched at Alachua County SW Landfill (ACSWL) which was an old landfill as compared to research site used for the present research (i.e., NRRL) and therefore, the landfill waste for the ACSWL is expected to have higher density th an the waste density of the NRRL. Because of these differences, i.e., different liquids addition times and research sites, the performance comparison is not accurate but only provides some close estimates. Larson (2007) conducted research on 16 subsurface horizontal injection lines (HILs) and fluid conductance values were reported in a range of 1.9107 m/s to 7.5107 m/s with an average of 5.3107 m/s. Kumar (2009) also researched on 31 HILs and fluid conductance values were reported in a range of 1.6107 m/s to 3.4106 m/s with an average of 7.8107 m/s.

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49 Therefore, the average fluid conductance was observed 13 to 19 times higher than the values reported values by Larson (2007) and Kumar (2009). This is justifiable because the hydraulic conductivity is higher near the surface of the landfill and it decreases with depth (Bleiker et al. 1993, Powrie et al.1999 and Jain et al. 2006) and therefore, the surface liquids addition system was expected to perform better than the subsurface liquids addition system. 3.3.2 Hydraulic Conductivity Estimation The modeling results were plotted by taking hydraulic conductivity values along xaxis and steady state sectional flux (q) values along y axis for nine different si mu lations as shown in Figure 3 6. Steady state flux decreased with the decrease in the hydraulic conductivity and vice versa. The hydraulic conductivity of waste decreases with the increase in density of landfilled waste ( Bleiker et. al. 1993). The void sp ace, available for the movement of liquids, is reduced with the increase in the density of landfilled waste, resulting in the reduced flux. Steady state flux also show decrease with the increase in the anisotropy value, at a constant horizontal hydraulic c onductivity. The increase in the value of anisotropy results in the decrease of vertical hydraulic conductivity, at constant horizontal hydraulic conductivity as anisotropy is defined as Kx/Ky. Therefore, the decrease in the Ky results in the reduced flux. Steady state flux values from the field data were plotted on the plot generated by modeli ng results as shown in Figure 3 7. Assuming anisotropy value of waste ranging from 10 to 100 (based upon Chapter 2); the hydraulic conductivity was estimated at anisotropy values 10 and 100. The hydraulic conductivity values are listed in Table 3. 2 separately for four SITs. The average h orizontal hydraulic conductivity value was found as 1.1103 cm/s for anisotropy value 10 and 2.0103 cm/s for anisotropy value 100; average vertical hydraulic conductivity value was calculated as 1.1104 cm/s for anisotropy value 10 and 2.0105 cm/s fo r anisotropy value 100.

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50 Townsend et al. 1995 calculated vertical hydraulic conductivity of 3.0106 cm/s to 4.0106 cm/s. For the present research, the vertical hydraulic conductivity was estimated in a rage of 8.5105 cm/s to 2.0104 cm/s for anisotrop y value of 10 and 1.4105 cm/s to 3.7105 cm/s for anisotropy value of 100. The hydraulic conductivity at anisotropy value of 100 is more realistic estimate as the anisotropy value is high near the top surface of the landfill. The estimated values of hyd raulic conductivity are observed higher than the values calculated by Townsend et al. (1995). The difference of hydraulic conductivities between the two studies can be a result of the different research sites and the modeling limitations. 3.3.3 Pros and Cons of SITs The whole scrap tires proved to be a good bedding material because of the high infiltration rates. During the research, tires did not create any surfacing problem (springing back of tires to the top surface of the landfill), i.e., the problem due to which landfilling of whole tires is banned in many states within the U.S. It is not expected that tires will create the surfacing problem in future as well because the tires were tied together which made it a heavy and stable single unit of whole s crap tires. There are some economical benefits associated with the use of whole tires as a bedding media because it is available for free. It costs approximately $13 to produce one cubic meter shredded tires; the unit cost is based on the information provi ded by CM Tire Recycling, Sarasota Florida. Therefore, the present research saved approximately $1,800 by preferring whole scrap tires over shredded tires for a total SIT length of 135 m. Besides the economic benefit the whole tires as bedding media is a b etter option as compared to shredded tires because it reduces the fuel requirements and CO2 emissions which would have been caused by shredding the whole scrap tires. The SITs performed better than the infiltration ponds and one subsurface liquids addition system (HILs). The SITs eliminated some problems associated with surface infiltration ponds

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51 such as generation of additional leachate due to rainfall runoff, vectors attraction, odor and aesthetic issues. The construction of SITs was easier and economical as compared to installation of vertical wells as no drilling was required. However, the SITs have some disadvantages as well. The construction of SITs was relatively complicated as compared to surface infiltration ponds. In the subsurface liquids addition systems liquids can be injected under pressure and therefore, larger volume of liquids can be added into landfill as compared to the SITs in a given time. The SITs did not allow pressurized injection and require close monitoring for the pressure head to a void seeps. The SITs also create soft points on the landfill surface due to settlement of the waste and it can negatively impact the traffic and the operating equipment. 3.4 Conclusion s The present research focused on estimating the performance of SITs with whole scrap tires as a bedding media. The sectional flux, infiltration rates and the fluid conductance were found higher than surface infiltration trenches and subsurface horizontal injection lines. Besides better performance the SITs are a better opt ion for liquids addition because it eliminates some problems associated with surface infiltration ponds. Also, the present research provided an innovative option to manage whole scrap tires with economic and environmental benefits.

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52 Table 3 1. Parameters used for numerical modeling Parameter Value Horizontal Hydraulic Conductivity (K x ) (cms 1 ) 10 2 10 3 and10 4 Anisotropy Ratio 1, 10 and 100 Van Genuchten parameter, a 1 (m 1 of water column) Van Genuchten parameter, n 4 Van Genuchten parameter, m 0.75 Porosity (Vol/Vol) a 0.50 m (KPa 1 ) 3 10 3 Landfill Depth, (m) 40 Width of SIT (m) 0.5 Depth (or Height) of SIT (m) 1.2 Effective Depth of SIT (m) b 0.3 Injection Pressure (m) 0.9 a 50% porosity is assumed on the basis of the porosity range (45.5% to 55.5%) determined by Hudson et. al. (2004). bEffective Depth (of Height) is the depth of SIT without the 0.3 m of clay layer. Table 3 2 Compilation of field and modeling results Trench Pseudo Steady State Flux (Field Data) (m2/s) Fluid Conductance (Field Data) ( m/s ) Horizontal Hydraulic Conductivity a (cm/s) Vertical Hydraulic Conductivity b (cm/s) a=10 a=100 a=10 a=100 SIT 1 (15 m) 8.0 6 8.9 6 7.8 4 1.4 3 7.8 5 1.4 5 SIT 2 (30 m) 8.8 6 9.8 6 8.2 4 1.6 3 8.2 5 1.6 5 SIT 3 (45 m) 1.1 5 1.2 5 2.0 3 3.7 3 2.0 4 3.7 5 SIT 4 (45 m) 9.1 6 1.1 5 8.5 4 1.6 3 8.5 5 1.6 5 a The values are based upon Figure 3 7. bVertical Hydraulic conductivity (Ky) is the calculated by dividing horizontal hydraulic conductivity with anisotropy value.

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53 Figure 3 1. Plan View of Cell 5 of New River Regional Landfill showing locations of the Surface Infiltration Trenches

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54 A B C Figure 3 2 Configuration of whole scrap tires used as a bedding media in the s urface infiltration trenches: A) Plan View; B ) Cross Se ctional View along width; and C ) Cross Sectional View along length of the trench

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55 A B Figure 3 3 Si mulated landfill with showing A ) dimensions of the simulated landfill and location of the SIT; B ) closer look of the SIT

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56 Days (Day 1: May 27, 2010) 0 2 4 6 8 10 12 14 16 18 Fllux (m /s) 1e-6 1e-5 1e-4 Pressure head (in m water column) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head 2 A Days (Day 1: May 27, 2010) 0 2 4 6 8 10 12 14 16 18 1e-6 1e-5 1e-4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head Pressure head (in m water column) Fllux (m /s)2 B Days (Day 1: May 27, 2010) 0 2 4 6 8 10 12 14 16 18 1e-6 1e-5 1e-4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head Pressure head (in m water column) Fllux (m /s)2 C Days (Day 1: May 27, 2010) 0 2 4 6 8 10 12 14 16 18 1e-6 1e-5 1e-4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head Pressure head (in m water column) Fllux (m /s)2 D Figure 3 4 Flow rate and pressure head data with respect to time for A) 15 m trench; B) 30 m trench; C ) 45 m trench; and D ) the second 45 m trench.

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57 Cumulative Volume (m ) 0 10 20 30 40 50 Fllux (m /s) 1e-6 1e-5 1e-4 Pressure head (in m water column) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head 23 A 0 20 40 60 80 1e-6 1e-5 1e-4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head Pressure head (in m water column)Cumulative Volume (m )3Fllux (m /s)2 B 0 20 40 60 80 100 120 140 160 1e-6 1e-5 1e-4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head Pressure head (in m water column)Cumulative Volume (m )3Fllux (m /s)2 C 0 20 40 60 80 100 120 1e-6 1e-5 1e-4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Flowrate Pressure Head Pressure head (in m water column)Cumulative Volume (m )3Fllux (m /s)2 D Figure 3 5 Flow rate and pressure head data with res pect to cumulative volume for A) 15 m trench; B) 30 m trench; C ) 45 m trench; and D ) the second 45 m trench.

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58 Horizontal Hydraulic Conductivity (Kx), cm/s 1e-5 1e-4 1e-3 1e-2 1e-1 Flux (q), m /s 1e-7 1e-6 1e-5 1e-4 1e-3 a=1 a=10 a=100 2 Figure 3 6. Plot generated from the modeling results

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59 Horizontal Hydraulic Conductivity (Kx), cm/s 1e-5 1e-4 1e-3 1e-2 1e-1 Flux (q), m /s 1e-7 1e-6 1e-5 1e-4 1e-3 a=1 a=10 a=100 2 Flux = 8.010 m /s-6 2Kx = 7.810 cm /s-4Kx = 1.410 cm /s-3 A Horizontal Hydraulic Conductivity (Kx), cm/s 1e-5 1e-4 1e-3 1e-2 1e-1 Flux (q), m /s 1e-7 1e-6 1e-5 1e-4 1e-3 a=1 a=10 a=100 2 Flux = 8.810 m /s-6 2Kx = 8.210 cm /s-4Kx = 1.610 cm /s-3 B Horizontal Hydraulic Conductivity (Kx), cm/s 1e-5 1e-4 1e-3 1e-2 1e-1 Flux (q), m /s 1e-7 1e-6 1e-5 1e-4 1e-3 a=1 a=10 a=100 2 Flux = 1.110 m /sKx = 2.010 cm /s-3Kx = 3.710 cm /s-3-5 2 C Horizontal Hydraulic Conductivity (Kx), cm/s 1e-5 1e-4 1e-3 1e-2 1e-1 Flux (q), m /s 1e-7 1e-6 1e-5 1e-4 1e-3 a=1 a=10 a=100 2 Flux = 9.110 m /sKx = 8.510 cm /s-4Kx = 1.610 cm /s-3-6 2 D Figure 3 7. Flux values from field data plotted on the plot gen erated by modeling results for A)15 m trench; B) 30 m trench; C ) 45 m trench; and D) the second 45 m trenc h.

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60 CHAPTER 4 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 4.1 Summary Anisotropy (the ratio of lateral to vertical hydraulic conductivity) of waste is an important parameters required to design liquids addition systems and the present research wa s carried out to estimate this parameter. A buried liquids addition well surrounded by several piezometers installed at a full scale bior eactor landfill in Florida was used for the present research. Liquids addition was performed at a constant injection pr essure for 14 days, while the flow rate and pore pressures were closely monitored. The flow rate and the pore pressures were assumed to reach approximate steady state by the end of injection period. SEEP/W software was used to simulate liquids addition conditions. The modeling was performed under constant head; nine different simulations were performed by considering three different lateral hydraulic conductivity values (i.e. 1103, 1104 and 1105 cm/s) and three different anisotropy values (i.e. 1, 10 and 100). The field data (i.e., approximate steady state flow rate and pore pressures) were compared with the simulation results to estimate the hydraulic conductivity and the anisotropy. The anisotropy value was estimated in a range of 2 to 100 and with an average value of 38 and the associated lateral hydraulic conductivity was found in a range of 9.5105 cm/s to 4.0104 cm/s with an average value of 2.3104 cm/s. Another part of the research aimed to evaluate performance of surface infiltration trenc hes (SITs) and four SITs, with different lengths, were installed at the same landfill with whole tires as a bedding media. Liquids addition was performed for 16 days and t he performance of the SITs was estimated in terms of the unit flux (flow rate per uni t length), infiltration rate (unit flux per unit width of trench) and fluid conductance (unit flux per unit pressure head). The unit flux was found in a range of 8.0106 m2/s to 1.1105 m2/s, the infiltration rate ranged from 8.0106 m/s

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61 to 1.1105 m/s and fluid conductance ranged from 8.9106 m/s to 1.2105 m/s. The hydraulic conductivity of the waste surrounding the trenches was also estimated by comparing the field results with modeling results. The modeling was performed under the conditions simi lar to the field conditions and the average vertical hydraulic conductivity was found as 2.0105 cm/s at anisotropy ratio of 100. 4.2 Conclusions The conclusions from this research are the following: Anisotropy and lateral/horizontal hydraulic conductiv ity of waste were found decreasing with increase in depth of waste. Anisotropy values were found higher for the scenario where hydraulic conductivity was assigned constant for the entire media/waste as compared to scenario where hydraulic conductivity was assigned as a function of depth. Average anisotropy was found higher than the values reported by some previous studies. Performance of SITs was found better as compared to surface infiltration ponds in terms of infiltration rates. Performance of SITs was found better than the subsurface horizontal injection lines in terms of fluid conductance. Whole tires proved to be a better option than shredded tires because of economical and environmental benefits. 4.3 Recommendations More studies should be undertaken to estimate anisotropy of waste as it is an important parameter for design of liquids addition systems. One of the drawbacks in the present research was that the modeling results would not truly match the field results due to the limitations of the model. Future research should focus on finding in situ hydraulic conductivity of waste in both lateral and vertical directions so that more realistic estimates of anisotropy can be made. Some research should be undertaken to inquire the impact of landfill gas on liquids movement in landfill. Through the present research, SITs and whole tires as bedding material were proved to

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62 be viable options for liquids addition with economic and environmental benefits. One of the problems associated with the operation of SITs w as that it required intense monitoring of pressure head to avoid seeps. The monitoring can be much easier if some automatic switch or equipment was installed in the SITs which can turn on/off the pump if leachate levels reach a particular height.

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63 APPENDIX A SUPPLE MENTAL FIGURES FOR CHAPTER 2 This appendix presents the supplemental figures for Chapter 2. The figures are based on the field results and simulation results for the first scenario where hydraulic conductivity was assigned as a function of depth. It should be noted that second scenario simulations (hydraulic conductivity independent of depth) were performed to compare the results for the two scenarios only and first scenario simulations presents more realistic results.

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64 Days (Day 1: Feb 5, 2010) 0 2 4 6 8 10 12 14 Flow Rate 10^(-4) (m3/s) 0 5 10 15 20 25 30 Injection Pressure (m water column) 13 14 15 16 17 18 19 20 21 Flow Rate Injection Pressure Figure B 1 Flow rate and Injection Pressure Vs Time (from field data)

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65 Cumulative Volume (m3) 0 2000 4000 6000 8000 10000 12000 Flow rate (m3/s) 0.001 0.002 0.003 0.004 0.005 0.006 0.007 Flow Rate at Kr2=10-3 cm/s A Cumulative Volume (m3) 0 20 40 60 80 100 120 140 160 180 Flow rate (m3/s) 0.00000 0.00002 0.00004 0.00006 0.00008 0.00010 0.00012 Flow Rate at Kr2=10-4 cm/s B Cumulative Volume (m3) 0 5 10 15 20 25 Flow rate (m3/s) 2.0e-6 4.0e-6 6.0e-6 8.0e-6 1.0e-5 1.2e-5 Flow Rate at Kr2=10-5 cm/s C Figure B 2 Flow rate vs Cumulate Volume data for the simulations performed at anisotropy 1 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C) 105 cm/s

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66 Cumulative Volume (m3) 0 1000 2000 3000 4000 5000 6000 7000 Flow rate (m3/s) 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 Flow Rate at Kr2=10-3 cm/s A Cumulative Volume (m3) 0 200 400 600 800 Flow rate (m3/s) 0.00000 0.00002 0.00004 0.00006 0.00008 0.00010 0.00012 Flow Rate at Kr2=10-4 cm/s B Cumulative Volume (m3) 0 20 40 60 80 100 Flow rate (m3/s) 0.0 2.0e-6 4.0e-6 6.0e-6 8.0e-6 1.0e-5 1.2e-5 Flow Rate at Kr2=10-5 cm/s C Figure B 3 Flow rate vs Cumulate Volume data for the simulations performed at anisotropy 10 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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67 Cumulative Volume (m3) 0 10000 20000 30000 40000 Flow rate (m3/s) 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 Flow Rate at Kr2=10-3 cm/s A Cumulative Volume (m3) 0 1000 2000 3000 4000 Flow rate (m3/s) 0.00000 0.00002 0.00004 0.00006 0.00008 0.00010 0.00012 Flow Rate at Kr2=10-4 cm/s B Cumulative Volume (m3) 0 100 200 300 400 500 Flow rate (m3/s) 0.0 2.0e-6 4.0e-6 6.0e-6 8.0e-6 1.0e-5 1.2e-5 Flow Rate at Kr2=10-5 cm/s C Figure B 4 Flow rate vs Cumulate Volume data for the simulations performed at anisotropy 100 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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68 Time (hours) 0 500 1000 1500 2000 2500 Cumulative Volume (m3) 0 2000 4000 6000 8000 10000 12000 Cumulative Volume at Kr2=10-3 cm A Time (hours) 0 500 1000 1500 2000 2500 Cumulative Volume (m3) 0 200 400 600 800 1000 1200 Cumulative Volume at Kr2=10-4 cm B Time (hours) 0 500 1000 1500 2000 2500 Cumulative Volume (m3) 0 20 40 60 80 100 120 140 Cumulative Volume at Kr2=10-5 cm C Figure B 5 Cumulate Volume vs Time data for the simulations performed at anisotropy 1 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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69 Time (hours) 0 2000 4000 6000 8000 10000 12000 Cumulative Volume (m3) 0 10000 20000 30000 40000 50000 Cumulative Volume at Kr2=10-3 cm A Time (hours) 0 2000 4000 6000 8000 10000 12000 Cumulative Volume (m3) 0 1000 2000 3000 4000 5000 Cumulative Volume at Kr2=10-4 cm B Time (hours) 0 2000 4000 6000 8000 10000 12000 Cumulative Volume (m3) 0 100 200 300 400 500 600 Cumulative Volume at Kr2=10-5 cm C Figure B 6 Cumulate Volume vs Time data for the simulations performed at anisotropy 10 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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70 Time (hours) 0 20000 40000 60000 80000 Cumulative Volume (m3) 0.0 5.0e+4 1.0e+5 1.5e+5 2.0e+5 2.5e+5 Cumulative Volume at Kr2=10-3 cm A Time (hours) 0 20000 40000 60000 80000 Cumulative Volume (m3) 0 5000 10000 15000 20000 25000 30000 Cumulative Volume at Kr2=10-4 cm B Time (hours) 0 20000 40000 60000 80000 Cumulative Volume (m3) 0 500 1000 1500 2000 2500 3000 Cumulative Volume at Kr2=10-5 cm C Figure B 7 Cumulate Volume vs Time data for the simulations performed at anisotropy 100 and Kr2 A ) 103 cm/s ; B ) 104 cm/s; and C) 105 cm/s

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71 Cumulative Volume (m3) 0 2000 4000 6000 8000 10000 12000 Pore Pressure (m water column) 0 1 2 3 4 5 6 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth A Cumulative Volume (m3) 0 200 400 600 800 1000 1200 Pore Pressure (m water column) 0 1 2 3 4 5 6 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth B Cumulative Volume (m3) 0 20 40 60 80 100 120 140 Pore Pressure (m water column) 0 1 2 3 4 5 6 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth .C Figure B 8 Pore Pressure vs Cumulative Volume data for the simulations performed at anisotropy 1 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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72 Cumulative Volume (m3) 0 10000 20000 30000 40000 50000 Pore Pressure (m water column) 0 2 4 6 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth A Cumulative Volume (m3) 0 1000 2000 3000 4000 5000 Pore Pressure (m water column) 0 2 4 6 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth B Cumulative Volume (m3) 0 100 200 300 400 500 600 Pore Pressure (m water column) 0 2 4 6 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth C Figure B 9 Pore Pressure vs Cumulative Volume data for the simulations performed at anisotropy 10 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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73 Cumulative Volume (m3) 0.0 5.0e+4 1.0e+5 1.5e+5 2.0e+5 2.5e+5 Pore Pressure (m water column) 0 2 4 6 8 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth A Cumulative Volume (m3) 0 5000 10000 15000 20000 25000 30000 Pore Pressure (m water column) 0 2 4 6 8 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth B Cumulative Volume (m3) 0 500 1000 1500 2000 2500 3000 Pore Pressure (m water column) 0 2 4 6 8 Pore Pressure at 7.8 m depth Pore Pressure at 10.8 m depth Pore Pressure at 13.8 m depth C Figure B 10. Pore Pressure vs Cumulative Volume data for the simulations performed at anisotropy 100 and Kr2 A ) 103 cm/s; B ) 104 cm/s; and C ) 105 cm/s

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74 APPENDIX B CONSTRUCTION PHOTOGR APHS FOR CHAPTER 3 This appendix presents the construction photographs for the installation of surface infiltration trenches with whole tires as a bedding material.

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75 A B Figure C 1 Laying the header 7.6 cm HDPE pipe to transport leachate from coll ection ponds to the trenches, A ) We lding pipes on top of Cell 4; B ) Laying and burying header pipe on side slope of Cell 1.

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76 A B Figure C 2 Welding the perforated pi pe near the tr ench locations; A ) Four perforated pipes after welding (one 15 m, one 30 m and two 45 m); B ) Welding the solid pipe to the perforated pipe which was used to monitor leachate levels.

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77 A B Figure C 3 Preparing the Geotextile with the required dimens ions; A ) Cutting the Geotextile in 15 m by 1.2 m pieces; B ) Geotextile piece after cutting.

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78 Figure C 4 A truck unloading whole scrap tires near the location of the proposed trenches. Figure C 5 Manual selection of right size tires.

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79 Figure C 6 Constructing the geoconduit (perforated pipe surrounded by whole tires) near the trench location by stacking the whole scrap tires together, passing the perforated pipe from the middle and tying the tires with nylon rope Figure C 7 Internal vie w of stacked whole tires with perforated pipe in middle.

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80 A B Figure C 8 Trenching: A ) Excavation of t rench at the marked location; B ) Trench view (1 m by 1.2 m)

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81 A B Figure C 9 Placement of geoconduit inside the excavated trench; A ) Pushing the constructed geoconduit in to trench with three loaders; B ) Geoconduit placed inside the trench.

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82 Figure C 10. Placement of Geotextile over the installed geoconduit. Figure C 11. Placement of clay over the Geotextile.

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83 Figure C 12. Connection with the header pipe; a butterfly valve in the connection and a flow meter in 2.5 cm PVC section were installed. Figure C 13. The connection after installing the flowneter and valve; u traps were installed in 2.5 cm PVC section for proper functioning of the flowmeters.

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8 4 LIST OF REFERENCES Al Yousfi, A.B. and and Pohland, F.G. (1998). Strategies for simulation, design, and management of solid wastes disposal sites as landfill bioreactors. Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management, 1321. Ardejani, F.D., Badii, Kh., Limaee, N.Y., Mahmoodi, N.M., Arami, M., Shafaei, S.Z., Mirhabibi, A.R., (2006). Numerical modelling and laboratory studies on the removal of Direct Red 23 and Direct Red 80 dyes from textile e ffluents using or ange peel, a low -cost adsorbent. Dyes and Pigments 73 (2007) 178e185. Benson, C. H., Barlaz, M. A., Lane, D. T., and Rawe, J. M., B.E. (2007). Practice review of five bioreactor/recirculation landfills. Waste Management 27,1329. Bleik er, E.D., McBean, E., and Farquhar, G. (1993). Refuse Sampling and Permeability Testing at the Brock Westand Keele Valley Landfills. Proceedings, Sixteenth International Madison Waste Conference: municipal & industrial waste September 22-23, 1993. 5485 67. Durmusoglu, E., Sanchez, M. Itza and Corapcioglu, Y. M. (2006). Permeability and compression characteristi cs of Municipal solid waste. Environ Geol ., 50, 773789. Gabr, M. A., and Valero, S. N. (1995). Geotechnical Prop erties of Municipal Solid Waste. Geotechnical Testing Journal 18(2), 241255. Haydar, M and Khire, M. (2004). Evaluation of heterogeneity and anisotropy of waste properties on leachate recirculation in bioreactor landfills. Journal of Solid Waste Technology and Management 30(4), 233 242. Haydar, M., and Khire, M. (2005). Leachate recirculation using horizontal trenches in bioreactor landfills. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 131(7), 837 847. Hudson, A. P., Beaven, R. P., and Powrie, W. (1999). Measurement of the horizontal hydraulic conductivity of household waste in a large scale compression cell. Proceedings Sardinia 99, Seventh International Waste Management and Landfill Symposium S. Margherita di Pula, Cagliari, Italy; 4 8 October 1999. H udson A. P., White J. K., Beaven R. P., Powrie W. (2004). Modelling the compression behaviour of landfilled domestic waste. Waste Management 24, 259269. Jain, P. (2005). Moisture addition at bioreactor landfills using vertical wells: Mathematical model ing and field application. Ph.D. Dissertation. University of Florida, Gainesville, FL, U S A.

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85 Jain, P., Farfour, W. M., Jonnalagadda, S., Townsend, T. G., and Reinhart, D. R. (2005a). Performance evaluation of vertical wells for landfill leachate recirc ulation. Proceedings of Geo Frontier 2005, ASCE conference, January 2426, Austin, TX, U S A. Jain, P., Powell, J. P., Townsend, T. G., and Reinhart, D. R. (2005b). Air permeability of waste in a municipal solid waste landfill. Journal of Environmental Engineering ASCE, 131(11) 15651573. Jain, P., Powell, J., Townsend, T. G., and Reinhart, D, R. (2006). Estimating The Hydraulic Conductivity of Landfilled Municipal Solid Waste Using Borehole Permeameter Test. Journal of Environmental engineering, ASCE 132(6), 645653. Jain, P., Townsend, T. G., and Tolaymat, T. M. (2010). Steady -state design of vertical wells for liquids addition at bioreactor landfills. Waste Management Elsevier in press. Jang, Y.S., Kim Y.W., and Lee S.I. (2002). Hydraulic properties and leachate level analysis of Kimpo metropolitan Landfill, Korea Waste Management 22, 261267. Kadambala, R. (2009). Evaluation of a buried vertical well leachate recirculation system and settlement resulting from moisture additio n using vertical wells for municipal solid waste landfills. Ph.D. Dissertation. University of Florida, Gainesville, FL, U S A. Khire, M. and Mukherjee, M. (2006). Leachate Injection Using Vertical Wells in Engineered Landfills. Waste Management Elsevie r in press. Koerner, R. G., and Eith, W. A. (2005). Drainage capability of fully degraded MSW with respect to various leachate collection and removal systems. Geotechnical special publication 130, 42334237. Landva, A. O., Pelkey, S. G., and Valsangkar A. J. (1998). Coefficient of permeability of municipal refuse. Proceedings of the Third International Congress on Environmental Geotechnics Balkema, Rotterdam, 16367. Larson, J. A. (2007). Investigations at a Bioreactor Landfill to Aid in the Operation and Design of Horizontal Injection Liquids Addition Systems. Masters Thesis, University of Florida, Gainesville, FL, U S A. Maier, T.B. (1998). Analysis procedures for design of leachate recirculation systems. Water Quality International Nov Dec 1998, 3740. McCreanor, P.T. and Reinhart, D.R (1996). Hydrodynamic modeling of leachate recirculating landfills. Wat Sci. Tech ., 34(7 8), 46370. McCreanor, P.T. (1998). Landfill Leachate Recirculation Systems: Mathematical Modeling and Validation. P h.D. Dissertation. University of Central Florida. McCreanor, P.T. and Reinhart, D.R. (2000). Mathematical Modeling of Leachate Routing in a Leachate Recirculating Landfill. Water Research 34(4), 12851295.

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86 Mehta, R., Barlaz, M.A., Yazdani, R., Augenste in, D., Bryars, M., and Sinderson, L. (2002). Refuse Decomposition in the Presence and Absence of Leachate Recirculation. Journal of Environmental Engineering, March 2002, 228236. Pacey, J. P., Ramin Yazdani, D. Reinhart, R. Morck, D. Augenstein (1999). The Bioreactor Landfill: An Innovation in Solid Waste Management. SWANA Silver Springs, Maryland. Pohland, F.G. (1975). Sanitary landfill stablization with leachate recycle and residual treatment EPA 600/275 043. U S EPA, Washington DC, U S A. Pohland, Fredrick (1980). Leachate recycle as landfill management option. Journal of Environmental Engineering, ASCE, 106 (EE6), 1057 1069. Pohland, F.G. and Harper, S.R. (1986). Critical review and summary of leachate and gas production from landfills EPA/600/2 86/073. Cincinnati, OH, U.S.A.: U.S. Environmental Protection agency. Powrie, W and Beaven R.P. (1999). Hydraulic Properties of Household Waste and Applications for Landfills. Proceedings Institution of civil Engineers Geotechnical Engineering 137, 235247. Powrie, W., Beaven, R., Hudson, A., 2008. The influence of landfill gas on the hydraulic conductivity of waste. Geotechnical Special Publication No. 177, Geocongress 2008, Geotechnics of Waste Management and Remediaton, March 9, 2008, New Orleans, Louisiana, pp. 264 271. Reinhart D.R. and Townsend T.G. (1997). Landfill Bioreactor Design and Operation. Lewis Publishers, Boca Raton FL. Reinhart, D.R., McCreanor, P.T., and Townsend, T.G. (2002). The bioreactor landfill: Its status and future Waste Management and Research. 20: 172186. Shank, K.L. (1993). Determination of hydraulic conductivity of the Alachua County Southwest Landfill Master's thesis, University of Florida. Tchobanoglous, G., Theisen, H., and Vigil, S. (1993). Integrated solid waste management McGraw -Hill, New York, U S A. Townsend, T. G., (1995). Leachate recycle at solid waste landfills using horizontal injection. Ph.D. Dissertation, University of Florida, Gainesville, FL, U S A. Townsend, T. G., Miller W. L., and Ear le, J. F. K (1995). Leachate recycle infiltration ponds. Journal of Environmental Engineering, ASCE, 121(6), 465 471. Townsend, T. G., Miller, W. L, Lee, H. J., and Earle, J. F. K (1996). Acceleration of landfill stabilization using leachate recycle. J ournal of Environmental Engineering, ASCE, 122(4), 263268.

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87 Townsend, T. G. and Miller W. L. (1998). Leachate recycle using horizontal injection. Advances of Environmental Research, 2(2) 1995, 129 138. U S EPA (2006). Scrap tire cleanup guidebook January 2006. U S EPA (2007). Bioreactor Landfills June 2007. U S EPA (2008). Municipal Solid Waste in the United States: 2007 Facts and Figures Office of Solid Waste and Emergency Response EPA530R 08 010, November 2008. Woyshner, M.R. and Yanful, E .K. (1995) Modelling and field measurements of water percolation through an experimental soil cover on mine tailings. Canadian Geotechnical Journal 32(4): 601 609 (1995).

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88 BIOGRAPHICAL SKETCH Karamjit Singh was born in Punjab India, to Harmeet Singh a nd Tejinder Kaur He graduated with a Bachelor of Engineering in c ivil e ngineering from Punjab Engineering College Chandigarh, India in July, 2008. In August 2008, he enrolled in graduate school in the Environmental Engineering Sciences Department at the University of Florida, to study solid and hazardous waste management under the advisement of Dr. Timothy Townsend