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Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2013-04-30.

Permanent Link: http://ufdc.ufl.edu/UFE0043051/00001

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Title: Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2013-04-30.
Physical Description: Book
Language: english
Creator: YANG,YONGQIANG
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

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

Notes

Statement of Responsibility: by YONGQIANG YANG.
Thesis: Thesis (M.S.)--University of Florida, 2011.
Local: Adviser: Townsend, Timothy G.
Electronic Access: INACCESSIBLE UNTIL 2013-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043051:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043051/00001

Material Information

Title: Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2013-04-30.
Physical Description: Book
Language: english
Creator: YANG,YONGQIANG
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

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

Notes

Statement of Responsibility: by YONGQIANG YANG.
Thesis: Thesis (M.S.)--University of Florida, 2011.
Local: Adviser: Townsend, Timothy G.
Electronic Access: INACCESSIBLE UNTIL 2013-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043051:00001


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1 FEASIBILITY OF PHOSPHOGYPSUM AS MSW LANDFILL STRUCTURAL MATERIAL AND SHEAR STRENGTH OF MSW WITH DIFFERENT FOOD WASTE CONTENT By YONGQIANG YANG A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PART IAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2011

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2 2011 Yongqiang Yang

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3 To my wife Huisuo Huang; my son Allen Yang; and my parents, Guoan Yang and Junying Xia

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4 ACKNOWLEDGMENTS I would like to thank my academic advisor and committee chairman, Dr. Timothy Townsend, for sharing his knowledge and experience. I was very lucky to work with him. He gave me the wonderful experience of work ing on these valuable projects, and his tireless endeavors tow ard academic accomplishment inspired me. He put great effort to train me as a researcher and engineer. I would also like to thank my other committee members, D r Frank Townsend, D r Michael Annable, and D r David Bloomquist for their guidance in assistin g me in completing my graduate studies. Also, I am very thankful for the Mosaic Company and Caterpillar Inc. for their support Furthermore, I would like to thank my friends and colleagues Dr. Hwidong Kim Dr. Jae Hac Ko, Dr. Yu Wang, Dr Shrawan Singh, and Dr. Young Min Cho for providing me with wonderful advice and support. I acknowledge the support from my friends, Jianye Zhang, Antonio Yaquian, Wesley G ates, and Shabnam M ostary Also I would like to thank my friend Dan Pitocchi in the Florida Depart ment of Transportation, Gainesville, FL. I would especially like to thank my parents in law. In my last semester they came to the United States to help us with the daily responsibilities of housework and caring for our son so we could have more time to work on our projects and research. At last, I would like to thank my wife, son, parents, and my brother and for their l ove, support, and encouragement

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5 TABLE OF CONTENTS ACKNOWLEDGMENTS .................................................................................................. 4 page LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 9 LIST OF ABBREVIATIONS ........................................................................................... 11 ABSTRACT ................................................................................................................... 12 CHAPTER 1 INTRODUCTION .................................................................................................... 14 Research Background ............................................................................................ 14 Research Objectives ............................................................................................... 16 Research Approach ................................................................................................ 16 Outline of Thesis ..................................................................................................... 17 2 GEOTECHNICAL ENGINEERING PROPERTIES OF PHOSPHOGYPSUM ......... 18 Materials and Methods ............................................................................................ 19 PG Samples Collection, Storage and Safety .................................................... 19 Test Methods .................................................................................................... 20 Results and Discussion ........................................................................................... 22 Test Results ..................................................................................................... 22 Comparison with Previous Studies ................................................................... 23 Summary ................................................................................................................ 25 3 COMPATIBILITY TEST OF PHOSPHOGYPSUM WITH MSW LANDFILL LEACHATE AND GEOSYNTHETIC CLAY LINERS ............................................... 39 Materials and Methods ............................................................................................ 40 Test Materials ............................................................................................ 40 Test Methods ............................................................................................. 41 Results and Discussion ........................................................................................... 43 Test Results ............................................................................................... 43 Compatibility with MSW Landfill Leachate ................................................. 45 Compatibility with GCLs ............................................................................. 46 Summary ................................................................................................................ 47 4 SHEAR STRENGTH OF MSW WITH DIFFERENT FOOD WASTE CONTENT ..... 59 Materials and Methods ............................................................................................ 60

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6 MSW Specimen Preparation ............................................................................ 60 Direct Shear Test ............................................................................................. 61 Data Analysis ................................................................................................... 62 Results and Discussion ........................................................................................... 63 Stress Displacement Response ....................................................................... 63 Change of Internal Friction Angle ..................................................................... 63 Application to Landfill Slope Stability Design .................................................... 65 Summary ................................................................................................................ 65 5 SUMMARY AND CONCLUSIONS .......................................................................... 75 APPENDIX A SUPPLEMENTAL TABLES .................................................................................... 77 B SUPPLEMENTARY FIGURES ............................................................................. 103 LIST OF REFERENCES ............................................................................................. 108 BIOGRAPHICAL SKETCH .......................................................................................... 113

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7 LIST OF TABLES Table page 2 1 PG sieve analysis test results ............................................................................. 26 2 2 PG standard compaction test results .................................................................. 27 2 3 PG direct shear test results ................................................................................ 28 2 4 PG hydraulic conductivity test results ................................................................. 29 2 5 PG hydraulic conductivity in this study and previous tests ................................. 30 3 1 Hydraulic conductivity of GCL permeant chemical properties ............................ 49 3 2 GCL Hydraulic conductivity in this study and the previous researchs ................. 50 4 1 Composition of MSW specimens ........................................................................ 67 4 2 Sizes and moisture contents of each waste component ..................................... 68 4 3 Average moisture contents and dry densities of the MSW specimens ............... 69 4 4 Mobilized internal friction angle and cohesion values ......................................... 70 A 1 PG sieve analysis test data ................................................................................ 77 A 2 PG standard compaction test data ..................................................................... 78 A 3 Hydraulic conductivity test data for SWPG ......................................................... 79 A 4 Hydraulic conductivity duplicate test data for SWPG .......................................... 80 A 5 Hydraulic conductivity test data for WWPG ........................................................ 81 A 6 Hydraulic conductivity duplicate test data for WWPG ......................................... 82 A 7 Hydraulic conductivity test data for NWPG ......................................................... 83 A 8 Hydraulic conductivity duplicate test data for NWPG .......................................... 84 A 9 Hydraulic conductivity test data for EWPG ......................................................... 85 A 10 Hydraulic conductivity duplicate test data for EWPG .......................................... 86 A 11 Cations concentration in batch leaching solution of SWPG of with MS W Leachate ............................................................................................................. 87

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8 A 12 Cations concentration in batch leaching solution of WWPG of with MSW Leachate ............................................................................................................. 88 A 13 Cations concentration i n batch leaching solution of NWPG of with MSW Leachate ............................................................................................................. 89 A 14 Cations concentration in batch leaching solution of EWPG of with MSW Leachate ............................................................................................................. 90 A 15 Cations concentration in batch leaching solution of GCL bentonite with DI water ................................................................................................................... 91 A 16 Cations concentration in batch leaching solution of GCL bentonite with MSW landfill leachate ................................................................................................... 92 A 17 Cations concentration in batch leaching solution of GCL bentonite with simulated SWPG leachate .................................................................................. 93 A 18 Cations concentration in batch leaching solution of GCL bentonite with simulated WWPG leachate ................................................................................. 94 A 19 Cations concentration in batch leaching solution of GCL bentonite with simulated NWPG leachate ................................................................................. 95 A 20 Cations concentration in batch leaching solution of GCL bentonite with simulated EWPG leachate .................................................................................. 96 A 21 GCL hydraulic cond uctivity test results with DI water ......................................... 97 A 22 GCL hydraulic conductivity test results with MSW landfill leachate .................... 98 A 23 GCL hydraulic conductivity test results with simulated SWPG leachate ............. 99 A 24 GCL hydraulic conductivity test results with simulated WWPG leachate .......... 100 A 25 GCL hydraulic conductivity test results with simulated NWPG leachate ........... 101 A 26 GCL hydraulic conductivity test results with simulated EWPG leachate ........... 102

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9 LIST OF FIGURES Figure page 2 1 PG particle size distribution ................................................................................ 31 2 2 Standard compaction curves of SWPG .............................................................. 31 2 3 Standard compaction curves of WWPG ............................................................. 32 2 4 Standard compaction curves of NWPG .............................................................. 32 2 5 Standard compaction curves of EWPG .............................................................. 33 2 6 Standard compaction and modified compaction curves of SWPG. ..................... 33 2 7 Shear strength versus horizontal displacement for the SWPG ........................... 34 2 8 Residual shear strength versus normal stress to determine the interface friction angle and cohesion for the SWPG .......................................................... 34 2 9 Shear strength versus horizontal displacement for the WWPG .......................... 35 2 10 Residual shear strength versus normal stress to determine the interface friction angle and cohesion for the WWPG ......................................................... 35 2 11 Shear strength versus horizontal displacement for the NWPG ........................... 36 2 12 Re sidual shear strength versus normal stress to determine the interface friction angle and cohesion for the NWPG .......................................................... 36 2 13 Shear strength versus horizontal displacement for the EWPG ........................... 37 2 15 Compacted PG hydraulic conductivity under different confining pressures ........ 38 3 1 Calcium concentrations in the batch leaching soultions of PG with MSW landfill leachate ................................................................................................... 51 3 2 Sulfate concentrations in the batch leaching solutions of PG with MSW landfill leachate ................................................................................................... 51 3 3 TDS in the batch leaching solutions of PG with MSW landfill leachate ............... 52 3 4 Hydraulic conductivity, pH, and specific cond uctivity of the SWPG in column test ..................................................................................................................... 53 3 5 Hydraulic conductivity, pH, and specific conductivity of the WWPG in column test ...................................................................................................................... 54

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10 3 6 Hydraulic conductivity, pH, and specific conductivity of the NWPG in column test ...................................................................................................................... 55 3 7 Hydraulic conductivity, pH, and specific conductivity of the EWPG in column test ...................................................................................................................... 56 3 8 Calcium conc entrations in batch leaching test of GCL bentonite with DI water, MSW landfill leachate, and simulated PG leachate ............................................ 57 3 9 Sodium concentrations in batch leaching test of GCL bentonite with DI water, MSW landfill leachate, and simulated PG leachate ............................................ 57 3 10 Potassium concentrations in batch leaching test of GCL bentonite with DI water, MSW landfill leachate, and simulated PG leachate ................................. 58 3 11 GCL hydraulic conductivity to simulated PG leachate, MSW landfill leachate, and DI water ....................................................................................................... 58 4 1 Stress displacement res ponse curves of direct shear tests with 0, 20, 50, and 70% of food waste specimens under 96 kPa of effective normal stress ............. 71 4 2 Stress displacement response curves of direct shear tests with 0, 20, 50, and 70% of food waste specimens under 192 kPa of effective normal stress ........... 71 4 3 Stress displacement response curves of direct shear tests with 0, 20, 50, and 70% of food waste spec imens under 287 kPa of effective normal stress ........... 72 4 4 Mohr Coulomb failure envelopes of direct shear tests ........................................ 72 4 5 Impact of food waste contents in synthetic fresh MSW on friction angles at different displacement levels .............................................................................. 73 4 6 Relationship of MSW internal friction and cohesion by direct shear test with different food waste contents .............................................................................. 73 4 7 Comparison of values of internal friction angle and cohesion values in this study to those of in previous studies ................................................................... 74 B 1 PG stack and sample location. ......................................................................... 103 B 2 PG samples were stored in solid and hazard waste management laboratory .. 104 B 3 Schematic diagram of PG column test ............................................................. 105 B 4 Compacted PG and GCL hydraulic conductivity test devices ........................... 106 B 5 Largescale direc t shear test device ................................................................. 107

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11 LIST OF ABBREVIATIONS ASTM American Society for Testing and Materials DI Deionized EPA U.S. Environmental Protection Agency EW East wall of PG stack FIPR Florida Industrial and Phosphate Research Ins titute GCL Geosynthetic clay liner MSW Municipal solid waste NW North wall of PG stack PG Phosphogypsum SW South wall of PG stack TDS Total dissolved solids WW West wall of PG stack

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12 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering FEASIBILITY OF PHOSPHOGYPSUM AS MSW LANDFILL STRUCTURAL MATERIAL AND SHEAR STRENGTH O F MSW WITH DIFFERENT FOOD WASTE CONTENT By Yongqiang Yang M ay 2011 Chair: Timothy G. Townsend Major: Environmental Engineering Sciences Research related to the potential landfill structural material of phosphogypsum (PG) and the shear strength of municipal solid waste ( MSW ) was conducted. The geotechnical engineer ing properties of PG the compatibility of PG with MSW landfill leachate and geosynthetic clay liners ( GCLs ) and t he shear strength of MSW with different food waste content s were all explored. The m aximum dry density of PG ranged from 1450 to 1560 kg/m3 i n standard compaction tests Interface friction angles of compacted PG ranged from 33 8 to 39.7 under drained conditions. PG compaction and shear test results supported the hypothesis that compacted PG has sufficient geotechnical properties to serve as a foundation base layer under landfills. In this study, the hydraulic conductivity of compacted PG ranged from 2.9 x 105 to 7.3 x 105 cm/sec under a confining pressure of 69 to 345 kPa, higher than the 105 cm/sec required by Florida Landfill Rules for double lined landfill s. Elevated c oncentrations of Ca2+, SO4 2-, and total dissolved solids ( TDS) were observed in batch leaching solutions of PG with MSW landfill leachate. Elevated concentrations of Ca2+ and SO4 2may impact landfill leachate and gas quality In

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13 column tests, the hydraulic conductivity of compacted PG with MSW landfill leachate ranged from 2.8 x 105 to 6.6 x 105 cm/sec, slightly higher than hydraulic conductivit y measured using deionized ( DI ) water, which ranged from 1.8 x 105 to 2.7 x 105 cm/sec, but they were in the same order of magnitude of 105 cm/sec. The impact of MSW landfill leachate to compacted PG hydraulic conductivity was not significant. S ignificant cation exchange of Na+ and K+ wa s found in the batch leaching solutions of GCL bentonite with MSW landfill leachate. A more significant exchange of Ca2+ occurred in the batch leaching tests of GCL bentonite with simulated PG leachate. In the GCL hydraulic conductivity tests, the hydraulic conductivit y of GCLs with simulate d PG leachate ranged from 1.2 x 106 to 3.6 x 109 cm /sec whereas with MSW landfill leachate the hydraulic conductivity ranged from 6.4 x 106 to 1.8 x 107 cm /sec. Both of these were higher than with DI water which g ave a hydraulic conductivity ranging from 2.3 x 109 to 4.1 x 109 cm /sec The impact of food waste content on the MSW shear strength was studied by largescale (430 mm430 mm) direct shear test u sing synthetic MSW with different food waste content s (0, 20, 50, and 7 0%) In the shear tests with different food waste content s, t he internal friction angle of MSW ranged from 15 to 35 and cohesion ranged from 5 to 12 kPa. The bi linear internal friction angle envelope showed that if the food waste content in MSW is higher than 50%, the internal friction angle could drop dramatically.

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14 CHAPTER 1 INTRODUCTION Research Backgrou nd Phosphogypsum (PG) is a solid by product produced during the wet manufacturi ng process of phosphoric acid. PG is composed of calcium sulfate d i hydrate (CaSO4 2 H2O), trace elements (TE), rare earth elements (REE), and naturally occurring radioactive elements such as Radium 226 (226Ra) and Uranium 238 (238U). In 1992, U.S. Environmental Protection Agency (USEPA) issued the rule prohibiting the offsite use of PG with average radium concentration greater than 10 picocuries per gram (pCi/g) requiring this PG to be placed in large piles or stacks to prevent it from entering the environment. These stacks are normally built on unused or excavated land on the processing site. According to USEPA (2010) about 30 million tons of PG are produced annually in Cent ral Florida, and are st oc kpiled indefinitely in stacks. In total, about 7.7 billion metric tons were generated in the United States from 1910 to 1981. The surface area covered by individual stacks r anges from about 5 to 740 acres In 1989, the total sur face area covered by stacks was about 8,500 acres, of which more than half is in Florida (USEPA, 2010) In 1999, US EPA m odified its regulations allowing the use of 317 to 3175 kg of PG for indoor research and development, thus giving researchers opportunities to develop practical applicati ons for PG. Many research projects have been conducted to investigate a variety of practical application s o f PG T hese included using PG as a road fill material (FIPR, 1983; FIPR, 1989; FIPR, 1990), soil stabilizer (Deg irmenci, et al. 2006), and embankment material (Moussa et al. 1984) In the PG application areas surveyed in FIPR, 1993, ( roads and parking lots in Florida and Texas ) there were no environmental or health impacts

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15 reported from exposure to radioactive mat erials in PG In the present study, a potential beneficial use for PG is explored: as part of municipal solid waste ( MSW ) landfill construction and operation activities. The options include use of PG as landfill daily cover material, and, a t new landfill sites, use as a substitute for the large volume of soil required to be placed under the liner to provide the needed grades for leachate drainage. Although the above applications would offer benefits, many technical questions have to be addressed to make sure necessary regulatory requirements are met and longterm environmental protection is ensured. The research reported here provides information helpful for making preliminary assessments of the feasibility of these approaches. The topics covered in thi s thesis include evaluating the PG geotechnical engineering properties and the compatibility of PG with MSW landfill leachate and geosynthetic clay liner s ( GCLs ) as landfill foundation and daily cover material In recent years with the rising demand for l andfill capacity there has been a drive towards vertical expansion, resulting in a number of landfill slope failures. Thus, estimating the geotechnical properties of MSW has become an ever more important need for landfill design (Stark et al. 2009 ). MSW shear strength has been evaluated by many researchers ( Kavazanjian et al. 1995; Kavazanjian et al. 1999; Machado et al. 2002; Mahler and Netto 2003; Harris et al. 2006; Gabr et al. 2007; Zhan et al. 2007; Zekkos et al. 2007; Kavazanjian 2008; Zekkos et al 2008; Reddy et al. 2009; Cho et al. 2011 ). However, m ost of these researcher s performed experiments on waste sourced from western countries. In Asian countr ies the MSW composition is typically different from w estern countries For example, the average food waste content of U.S. MSW is

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16 approximately 12.5% (USEPA, 2005), while that of China has been reported to be up to 73% (The World B ank, 1999; Wang and Nie, 2001). High food waste content MSW such as that which is found in Asian count r ies could impact the waste shear strength ( Cho et al. 2011 ) Thus it is necessary to eval uate MSW shear strength with different food waste content s to help in landfill slope stability design. Research Objectives One objective of this study was to evaluate the feasibil ity of utilizing PG as a structural material for lined MSW landfills. The applicabi lity has been judged by testing PG g eotechnical engineering properties and PG compatibility with MSW landfill leachate and GCLs Another objective was to measure t he shear strength of MS W with different food waste content s to contribute to MSW landfill slope stability design. Research Approach Objective 1. Evaluating PG geot echnical engineering properties as landfill construal material Approach. A series of classical soil g eotechnical engineering properties test s, adopted from ASTM were performed on PG. Sieve analysis was used to determine PG particle distribution; compaction test s were perform ed to evaluat e PG compaction properties ; PG shear strength was tested by direct shear test ; and hydraulic conduct ivity of compacted PG was measured in triaxial cells. Objective 2. Testing PG compatibility with MSW landfill leachate and GCL s as landfill construal material Approach. Batch leaching test s, column test s, and GCL hydraulic conductivity test s were conducted to evaluate the compatibility of PG with MSW landfill leachate and GCL s. PG leaching test s were performed to evaluate the impact of PG o n the quality of

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17 MSW landfill leachate. GCL leaching test s were used to analyz e the exchange of cations in the leaching solution with MSW landfill leachate and simulated PG leachate. Column test s were u sed for long term monitoring of PG compatibility with MSW landfill leachate. GCL hydraulic conductivity tests were performed in triaxial cell s using MSW landfill and simulated PG leachate as test liquids Objective 3. Estimating the shear strength of MSW with different food waste content s contribute to landfill slope stability design Approach. D irect shear tests were conducted on synthetic MSW samples with food waste content s of 0, 20, 50, and 70% Eight representativ e waste components were combined t o prepare a reproducible specimen: food waste, paper, plastic, metal, wood, textile, glass, and ash. These were placed in a stresscontrolled direct shear box testing device (430 mm length 430 mm width) with a maximum 16 cm horizontal displacement and n ormal pressures of 96, 192, and 287 kPa were applied. Outline of Thesis This thesis is organized into 5 Chapters Appendices and References Chapter 1 presents the introduction, objectives, and research approach. Chapter 2 presents the PG geotechnical engineering properties test s. Chapter 3 presents results from PG compatibility experiments Chapter 4 presents the shear strength of MSW wit h different food waste content C hapter 5 provides the comprehensive summary and conclusion of the entire research of this thesis. Supplementary Tables and Figures are provided in the Appendices Cited references are included at the end of this thesis

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18 CHAPTER 2 GEOTECHNICAL ENGINEERING PROPERTIES OF PHOSPHOGYPSUM The design of a MSW landfill bottom liner includes placing a low permeability barrier layer, compacted clay usually, at the bottom of the l andfill and grading the barrier layers to promote gr avity drainage of the leachate to low points from which leachate can be removed. Given the relatively flat topography in Florida, it is necessary to either excavate in order to achieve the needed grade, or to bring in extra fill material. For landfills with large base areas, the amount of soil that is needed may be very large, which may necessitate the purchase and delivery of soil from off site. Phosphogypsum ( PG ) could potentially be utilized as a base layer for a new ly lined MSW landfill in order to help reach needed grades The use of PG for this purpose w ould result in savings to the landfill operator if soils needed to be hauled in from long distances. It would also be a benefit to the PG producers as it would provide the opportunity for benefici al use of the material. To achieve these aims geochemical engineering assessments have to be conducted to evaluate whether PG has sufficient geochemical properties to serve as a foundation base layer For example, Florida Landfill Rules (F DEP, 2010) requires that in the double liner systems for a MSW landfill, t he lower geomembrane is placed directly on a subbase which is a minimum six inches thick and has a saturated hydraulic conduc tivity of less than or equal to 105 cm /sec. In this chapter, a serie s of geochemical test s, consisting of sieve analysis, c ompaction, hydraulic conductivity measurements and shear strength tests were carried out to evaluate the engineering properties of PG as sub base material for MSW landfills.

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19 Material s and Methods PG Samples Collection, Storage and S afety Collection. PG was sampled from the t op of a Mosaics Bar tow Facility, South PG stac k located in Mulberry, Florida. Samples were col lected from four locations: the south, west, north, and east, wall of the top PG st ack. (These samples are henceforth referenced as SW PG WWPG NW PG and EW PG respectively.) Samples were collected at approximately 30 to 60 cm depths from the top of the stack wall. PG samples were then transported to the University of Florida Solid a nd Hazard Waste Management R esearch L aboratory. A chain of custody record was kept from the point of sample collection to the laboratory. Storage. The PG samples were stored in closed containers in the lab at room temperature. To perform research on PG, requirements of 40 CFR 61.205 were followed; all PG samples were accompanied by certified documents that conformed to the requirements of 40 CFR 61.208. The total quantity of PG at this research facility did not exceed 3182 kg. Containers of PG were labele d with the following warning: Caution: Phosphogypsum Contains Elevated Levels of Natur ally Occurring Radioactivity. Safety U.S. Occupational Safety and Health Administration health and safety instructions were followed in all phases of the project which were involved with PG. Field and laboratory personnel were made aware of the common exposure routes for chemicals, such as, inhalation, ingestion, and contact. They were instructed in the proper use of safety equipment such as protective clothing and respiratory equipment. Basic first aid kits were made accessible to all personnel involved in this research.

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20 Test Methods Sieve analysi s Sieve analysis tests were performed to classify the grain size distribution of the PG by followi ng ASTM D 421. The smal lest sieve used in these tests was a No. 200 sieve with a 0.075 mm opening size. This size corresponds to the Unified Soil Classification System s size for distinguishing between sand and silt. Prior to sieve analysis, a 200 g of PG was dried in an oven at 60C for 24 hours. The dried PG was gently crushed by mortar and pestle. A total of 100 grams of PG were placed in the sieve stack and shaken for 10 minutes. The retained PG in each sieve was weighed to calculate the retaining and passing percent age for each grain size range. Compaction. C ompaction met hods described in ASTM method D 421 were employed to determine PG compaction properties. Ap proximately 2,500 g of PG which passed a No. 4 sieve were dried at 60C for 24 hours. The desired moisture cont ent was achieved by mixing the PG samples with a known amount of water and each sample was left undisturbed overnight before compacting. Then PG was compacted into a 10 cm diameter mold in three layers. During the compaction procedure, each la yer was subjected to 25 blows with a 2 .5 kg h ammer dropped from a height of 30.5 cm In addition, for more effort compaction tests each layer was subjected to 50 blows of a 2 .5 kg h ammer dropped from a height of 30.5 cm The compaction tests were repeated 10 time s with different values of soil water content for each PG sample. C ompaction curves were drawn of the res ulting relationship of dry weight density versus water content. Specimen w ater contents were determined by oven dry ing for 24 hours at 60C according to ASTM D2216 PG samples specific gravity were determined by ASTM D854

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21 Direct shear test Direct shear test s, adopted from ASTM D 3038, were used to determine the shear strength properties of internal friction and cohesion of compacted PG under drained c ondition. The maximum dry density and optimum water content were obtained for each PG specimen from the standard compaction tests The direct shear apparatus is a 10 cm diameter circular shear box with separated lower and upper halves. The lower half of the box is fixed to a frame while the upper half is capable of moving horizontally relative to the lower one. Each PG sample was tested at four different normal loads, 144, 287, 431, and 575 kPa. A 0.018 cm/ min shearing rate was used for the test to per mit a good drainage (Moussa et al. 1984) Horizontal displacement, vertical displacement, and shear load measurements were recorded during each test. Compacted PG internal frictions and cohesions were determined b using Mohr Coulomb E quation 21 (2 1) ; c = (Effective or apparent ) cohesion (Effective) normal stress le of internal friction. Hydraulic conductivity. Hydraulic conductivities of the c ompacted P G were measured in accordance with ASTM D5084 using a flexible wall permeameter, composed of triaxial cells and pressure providing flexpanels. DI water was used as the test liquid. PG specimens were compacted in a 7.1 cm diameter compaction mol d at optimum moisture content in three layers Three steps of back pressure saturation, consolidation, and permeation were used to complete hydraulic conductivity tests. Compacted PG specimens were set up in the flexible wall permeameter with a pair of s aturated porous stones on the bottom and top. Then, specimens were saturated using a 483 kPa backpressure, taking 7 to 10 days to

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22 achieve a complete saturation. Before permeation, specimens were consoli dated under confining pressures of 69, 207, and 345 kPa. Consolidation was completed in 35 days under each confining pressure. The hydraulic conductivity was test ed using a falling head rising tail test method. Hydraulic conductivity, k, was determined by using the Equation 22 1 2ln() ()inout inouttaaL h k aaAh (2 -2) Where, k = hydraulic conductivity (cm/s), ain = crosssectional area of the inflow stand pipe (cm2), aout = crosssectional area of the out flow stand pipe (cm2), L = height of specimen (cm), A= cross sectional area of specimen (cm2), h1 = head loss across the specimen at t1, (cm of water), h2 = head loss across the specimen at t2 (cm of water), ln = natural logarithm (base e = 2.71828), and t = interval of time (t1t2) (seconds). Results and Discussion Test R esults Sieve analysis. Sieve analysis test results for the PG samples are presented in Table 2 1 and Figure 2 1 The sieve analysis results showed that the percentage of PG passing # 200 sieve ranged from 44 to 71%. According to American Association of State Highway and Transportation Officials ( AASHTO ) M 145, PG samples were clas sified as silt clay materials as more than 35% pass a sieve # 200 (0.075mm). More sieve analysis test data was present in Table A 1. Compaction. Laboratory compaction test results of PG were presented in Table 2 2 The test results of standard compaction show ed that m aximum dry density of PG samples ranged from 1450 to 1560 kg/m3 while the optimum moisture content ranged from 16.4 to 19.0%. More effort compaction test result s showed that m aximum dry

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23 density was 1620 kg/m3 with an optimum moisture content of 14.2% for SW PG, which was only slight ly higher than in the standard compaction test (Figure 26). T hus, compaction energy defined as the potential energy of the falling hammer times the number of falls, had little influence on the values of maximum dry density and optimum water content of the PG samples Table 31 show ed that PG compaction behavior is also dependent on its fine percentage (passing sieve # 200). It was found that higher fine percentage correlates with lower maximum dry density after compaction and flatter dry density curves ( Figures 2 1 to 24 ). This indicates that PG dry density woul d be less sensitive to water content Direct shear test Direct shear test results are presented in Table 23 Test results show ed that the interface friction angle of the PG samples ranged from 33 8 to 39.7 that the cohesion ranged from 10 to 6 8 kPa. Figures 2 6 to 213 show the plot s of shear stress versus horizontal displacement and residual shear strength versus normal stress which was used to determine the interface friction angle and cohesion. Hydraulic conductivity test. Hydraulic conductivity t est results of compacted PG are presented in Table 2 4 Hydraulic conductivities of PG samples ranged from 2.9 x 105 to 7.3 x105 cm/sec under confining pressures of 69, 207, and 345 kPa. Figur e 21 4 shows that hydraulic conductivities of compacted PG sam ples slightly decreased with increasing confining pressure. More hydr aulic conductivity test data is present ed in Tables A 4 to A 11. Comparison with Previous S tudies Particle size distribution of PG test ed in this study was similar to that found in the previous investigations (FD OT, 2008). The percentage of PG passing through a # 200

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24 Sieve in this study ranged from 44.2 to 73.2%, which was similar to the results r eported by FDOT (20 08) (41.5 to 73.9% ) FDOT (2008) reported that PG samples should be classified as an A 4 material in the AASHTO Soil Classification System. A 4 material could serve well as a pavement component when properly compacted and drained. In s tandard compaction test s we f ound that PG had maximum dry density range of 1450 to 1560 kg/m3. These results are comparable to those found in the previous studies ( Moussa et al. 1984; FDO T, 2008). On the PG stack in the Mosaic Fertilizer Greenbay Facility d ry densities of undisturbed PG collected from different depths in the East and West walls ranged from 1232 to 2000 kg/m3 (Ardaman & Associates, Inc. 2007) which showed that PG under goes compression as the weight of the overlying PG increases and dry density of PG increased. Shear strength parameters determined for PG samples were also similar to the results of previous studies (Moussa et al. 1984; FDOT, 2008). In this study, PG samples internal friction angle ranged from 3 3 8 optimum water content. PG direct shear test s conducted by Moussa et al. (1984) showed internal friction angles ranging from 30 to 28%. FDOT, (2008) reported an internal friction angle of 44.34 for a compacted PG specimen on the ul timate loads in triaxial shear test s PG h ydraulic conductivity research has also been reported by some researchers ( Moussa et al. 1984; Ardaman & Associates, Inc, 2007; FDOT, 2008). Ardaman & Associates Inc. (2007) report ed vertical permeability of undis turbed PG samples collected in PG stacks at Mosaic Fertilizer Greenbay Facility, obtained from four borings on the PG stack ranged from 5.0 x 106 to 4.6 x 104 cm/sec. FDOT, ( 2008) and Moussa

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25 et al. ( 1984) reported laboratory compacted PG hydraulic conductivities ranging from 1.8 x 106 to 1.3 x 104 cm/sec. The hydraulic conductivities measured in this study, 2.9 x 105 to 7.3 x105 cm/sec, were similar to their test results PG hydraulic conductivity values from this study and previous studies are sum marized in Table 2 5 Summary In this study, PG dry densities in standard compaction tests are in the typical range of finegrained soil dry densities, 1280 to 2080 kg/m3 (Holtz and Kovacs, 1981), and shear strength parameters of the PG samples show sligh tly greater internal friction angles than t he typical 25 30 of fine grained soil These test results showed that PG had good geotechnical properties to serve as landfi ll sub base material in comparison to compacted clay. H owever, hydraulic conductivit ies of compacted PG, 2.9 x 105 to 7.3 x 105 cm/sec, were found to be higher than the typical range of hydraulic conductivities of compacted clays, which is less than 107 cm/sec (Benson et al. 1994). According to Florida Landfill Rules (FDEP, 2010), MSW landfil l subbase soil must have a saturated hydraulic conductivity of less than or equal to 105 cm/sec. Compacted PG hydraulic conductivity higher than 105 cm/sec, could not singly serve as subbase material A g eosynthetic clay liner (GCL) with a h ydrauli c conductivity not greater than 1x107 cm/sec could be placed on the top of compacted PG layer under landfill

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26 Table 2 1. PG sieve analysis test results Sample Passing # 10 (%) Passing # 20 (%) Passing # 30 (%) Passing # 50 (%) Passing # 100 (%) Passing # 200 (%) Diameter (mm) 2.000 0.850 0.420 0.250 0.150 0.075 SWPG 100.0 99.1 96.1 89.2 70.6 44.2 WWPG 99.9 98.6 95.2 88.1 69.4 44.6 NWPG 100.0 98.2 92.6 88.2 82.7 69.4 EWPG 100.0 99.0 95.7 93.0 86.4 66.3 Average 100.0 98.7 94.9 89.6 77.3 56.1

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27 Table 2 2. PG standard compaction test results Sample Maximum dry (kg/m3) Optimum water content (%) Passing # 200 sieve (%) GBSW 1560.0 16.4 43.7 GBWW 1530.0 17.0 46.7 GBNW 1460.0 19.0 71.3 GBEW 1450.0 19.0 66.5 Average 1500.0 17.9 57.1

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28 Table 2 3 PG direct shear test results Sample internal frication ( Cohesion (kPa) Passing # 200 sieve (%) SW PG 39. 7 43 43.7 WWPG 33. 8 6 8 46.7 NW PG 39. 4 1 0 71.3 EW PG 3 8.0 13 66.5 Average 37.7 33.5 57. 1

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29 Table 2 4 PG hydraulic conductivity test results Sample Hydraulic conductivity (cm/sec) P ass # 200 sieve (%) 69 kPa 207 kPa 345 kPa SWPG 5.9E 05 4.9E 05 4.1E 05 43.7 WWPG 6.2E 05 6.0E 05 5.3E 05 46.7 NWPG 3.7E 05 3.6E 05 3.2E 05 71.3 EWPG 5.7E 05 5.3E 05 4.9E 05 66.5 Average 5.4E 05 5.0E 05 4.4E 05 57.1

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30 Table 25 PG hydraulic conductivity in this study and previous tests Test method PG specimen Confining pressure (kPa) Hydraulic conductivity (cm/sec) References ASTM 5084, flexible wall Laboratory compacted 69345 2.9 x 105 7.3 x105 In this study Constant head Laboratory com p acted na* 1.8 x 1063.5 x 105 Moussa et al. 1984 ASTM 5084, flexible wall Laboratory compacted 35276 8.4 x 1051.3 x104 FDOT, 2008 ASTM 5084, flexible wall Undisturbed na 5.0 x 1064.6 x 104 Ardaman & Associates, Inc., 2007 Not available

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31 40 50 60 70 80 90 100 0.01 0.10 1.00 10.00 SWPG WWPG EWPG EWPG Percent passing (%) Grain size (mm) Figure 21. PG particle size distribution 1,400 1,500 1,600 1,700 1,800 1,900 10 12 14 16 18 20 22 24 Dry unit weight 100% saturated Water content (%) Unit weight (kg/m 3 ) Figure 2 2 Standard compaction curves of SW PG

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32 1,300 1,400 1,500 1,600 1,700 1,800 12 14 16 18 20 22 24 26 Dry unit weight 100% saturated Water content (%) Unit weight (kg/m 3 ) Figure 2 3 Standard compaction curves of W W PG 1,300 1,400 1,500 1,600 1,700 1,800 12 14 16 18 20 22 24 26 Dry unit weight 100% saturated Water content (%) Unit weight (kg/m 3 ) Figure 24 Standard compaction curves of N WPG

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33 1,300 1,400 1,500 1,600 1,700 1,800 12 14 16 18 20 22 24 26 Dry unit weight Water content (%) Unit weight (kg/m 3 ) Figure 25 Standard compaction curves of E WPG 1,400 1,500 1,600 1,700 1,800 1,900 2,000 8 10 12 14 16 18 20 22 100% saturated Dry unit weight-standard Dry unit weight-more effort Water content (%) Unit weight (kg/m 3 ) Figure 26 Stan dard compaction and modified compaction curves of SWPG, more effort compaction is done by adding more compaction effort of 50 blows per layer comparing to standard 25.

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34 0 100 200 300 400 500 600 0.0 0.5 1.0 1.5 2.0 144 kPa 144 kPa duplicate 287 kPa 287 kPa duplicate 431 kPa 431 kPa duplicate 575 kPa 575 kPa duplicate Horizontal displacement (%) Shear strength (kPa) Figure 2 7 Shear strength versus horizontal displacement for the SW PG y = 0.83x + 42.53 R = 0.99 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 Normal stress (kPa) Shear stress (kPa) Figure 2 8 Residual s hear strength versus normal stress to determine the interface friction angle and cohesion for the SW PG

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35 0 100 200 300 400 500 600 0.0 0.5 1.0 1.5 2.0 144 kPa 144 kPa duplicate 287 kPa 287 kPa duplicate 431 kPa 431 kPa duplicate 575 kPa 575 kPa duplicate Horizontal displacement (%) Shear strength (kPa) Figure 29 Shear strength versus horizontal displacement for the W WPG y = 0.67x + 67.50 R = 0.99 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 Normal stress (kPa) Shear stress (kPa) Figure 2 10 Residual s hear strength versus normal stress to determ ine the interface friction angle and cohesion for the WWPG

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36 0 100 200 300 400 500 600 0.0 0.5 1.0 1.5 2.0 144 kPa 144 kPa duplicate 287 kPa 287 kPa duplicate 431 kPa 431kPa duplicate 575 kPa 575 kPa duplicate Horizontal displacement (%) Shear strength (kPa) Figure 21 1 Shear strength versus horizontal displacement for the N WPG y = 0.82x + 9.98 R = 0.99 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 Normal stress (kPa) Shear stress (kPa) Figure 2 1 2 Residual s hear strength versus normal stress to determine the interface friction angle and cohesion for the N W PG

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37 0 100 200 300 400 500 600 0.0 0.5 1.0 1.5 2.0 144 kPa 144 kPa duplicate 287 kPa 287 kPa duplicate 431 kPa 431 kPa duplicate 575 kPa 575 kPa duplicate Horizontal displacement (%) Shear strength (kPa) Figure 21 3 Shear strength versus horizontal displacement for the E WPG y = 0.78x + 12.50 R = 0.98 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 Normal stress (kPa) Shear stress (kPa) Figure 2 1 4 Residual s hear strength versus normal stress to determine the interface friction angle and cohesion for the E W PG

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38 1.0E-05 3.0E-05 5.0E-05 7.0E-05 9.0E-05 0 100 200 300 400 SWPG WWPG NWPG EWPG Hydraulic Conductivity (cm/sec) Confining pressure (kPa) Figure 2 1 5 Compacted PG hydraulic conductivit y under different confining pressures of 69, 207, and 345 kPa

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39 CHAPTER 3 COMPATIBILITY TEST O F PHOSPHOGYPSUM WITH MSW LANDFILL LEACHAT E AND GEOSYNTHETIC CLAY LINERS PG is mainly compos ed of calcium sulfate di hydrate (CaSO4 2 H2O). Moussa, et al. (1984) reported that PG could dissolve in DI water about 2.4 g/L at pH 6. VanGulck et al. (2003) researched calcium precipitation from leachate and its accumulation within the pore space of the drainage medium causes scaling. Lee et al. (2005) reported that i n construction and demolition (C&D) landfill s a biological conversion of sulfate from disposed gypsum drywall to hydrogen sulfide ( H2S ) could happen in the anaerobic landfill environment. Concerns over this issue arise when discussing use of PG as a landfill nonstructural material such as daily cover soil. In order to address these concerns, b atch leaching and column test s on PG w ere conducted to test the compatibility of PG with MSW landfill leachate Previous test s, in Chapter 2 of this thesis, showed that compacted PG could not singly serve as subbase material under landfill Geosynthetic clay liner s ( GCLs ) could be used in MSW landfill composite bottom liners placing on compacted PG Many laboratory studies have been conducted on the evolution of GCLs i n contact with various types of chemical permeat e s containing cations that may impact the performances of the hydraulic conductivity of the GCL (Petrov and Rowe 1997; Ruhl and Daniel 1997; Shackelford et al. 2000; Jo et al. 2001). GCLs may contact with PG leachate or MSW landfill leachate, i n the case that geomembrane overlying the GCL is damaged, or the groundwater table increase and submerges compacted PG. As MSW leachate usually contains cations, cation exchange may occur in the GCL following the flow of leachate ( TouzeFoltz et al. 2006) PG dissolved in water or MSW leachate may

PAGE 40

40 cause cation exchange with GCL bentonite, which could impact GCL hydraulic conductivity performances. Here, GCL bentonite batch leaching test s with MSW landfill leachate and simulated PG leachate, and GCL hydraulic conductivity tests were conduct ed to test the PG compatibility GCLs. Materials and Methods Test Materials MSW landfill leachate. MSW landfill leachate was collected from Polk County North Central Class III landfill FL. MSW landfill leachate was stored in the University of Florida Solid Waste Management laboratory cooler s and used for batch leaching test s with PG samples, GCL bentonite batch leaching tests, and GCL hydraulic conduct ivity tests Simulation of PG lea chate. In this study PG leachate was created by mixing a 100 g PG sample with 2 L DI water in a 2.2 L glass jar. The mixture was agitated using a rotator for 16 to 20 hours After tumbling, the slurry was filtered to separate PG leachat e from the slurry Simulated samples of PG leachate was used for b entonite batch leaching tests and GCL hydraulic conductivity test s Simulated PG leachate and MSW landfill leachate chemical properties are summarized in Table 3 1. Geothynthetic clay liner s Geosynthetic clay liners (GCLs) are factory manufactured clay liners consisting of a layer of bentonite clay encased by geotextiles or glued to a geomembrane. In this study, the GCL contained granular sodium encased by two geotextiles bounded by needles The average thickness of GCL used in the hydraulic conductivity tests was 8 4 mm and the mass per unit area of air dried bentonite in the GCL was 3.64 kg/m2. GCL b entonite retrieved from GCL was used in GCL betonite batch leaching tests

PAGE 41

41 Test M ethods Batch test with MSW landfill leachate. The batch test of PG with MSW landfill leachate was conducted by adding 100 g PG to 2 L of MSW leachate and then mixing the aggregate on a rotary extractor for 18 2 hours at 30 rpm The mixture of MSW landfill leachate and PG was filtered using 0. s Sulfate (SO4 2-) concentrations in the filtered leaching solution were determined using a spectrophotometer (DR/4000 UV VIS, HACH, Loveland, CO) with HACH Method 8051. C ation concentrations were analyzed by ICP AES after acid dig estion according to USEPA test methods 6010C and 3010A. Total dissolved solids (TDS) were analyzed by USEPA test method of 160.1. Column test Column tests were conducted in accordance with ASTM D5856 and following the procedures of the drainage column tests conducted by Chapuis et al.(2006). The present test was used to evaluate the impact of MSW landfill leachate on the hydraulic conductivity and other chemical parameters of compacted PG. In this test, twelve columns were made from 10 cm diameter PVC pipes. PG samples were compacted in the column 12.7 cm deep in order obtain the optimum water content determined from previous PG standard compaction test. No confining pressure was applied for the tested PG specimens. MSW landfill leachate was used to fi ll in the columns. The test liquid in the column was maintained at 30.5 cm constant head above PG specimens in the columns. Test liquid flow direction was opposed to compaction direction. Effluent liquid passing the PG samples was collected to measure t he change of hydraulic conductivity of compacted PG and then measurements of pH and specific conductivity of the liquid were taken. Duplicate tests were performed for MSW landfill leachate filled columns,

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42 and DI water was used for a control to compare wit h MSW landfill leachate. Figure B 3 illustrated a column test. Batch test with GCL betonite. Leaching tests were conducted using bentonite from the GCL to evaluate the effect of cation exchange on GCL hydraulic conductivity. This test method was adopted from Benson and Meer (2009). MSW landfill leachate, DI water, and simulated PG leachate were used as extract solutions. For this test, 12.5 g of bentonite were mixed with 250 mL extract solutions and rotated for 18 2 hours. The mixture of extract solu tions and GCL betonite w after rotation. Cation concentrations were analyzed by ICP AES after acid digestion according to USEPA test methods 6010C and 3010A. TDS was analyzed by USEPA test method 160.1. GCL Hydraulic conductivity test Falling head rising tail hydraulic conductivity tests were conducted on GCL in flexiblewall permeameters according to methods described in ASTM D6766. An average hydraulic gradient of 170 and a confining pressure of 69 kPa were applied in this test. S imulated PG leachate, MSW landfill leachate, and DI water were used as the permeate solutions. A large backpressure of 583 kPa was used to achieve saturation in the GCL specimens. GCL specimens were prepared by using 105 mm diameter stainless steel cutting ring and a sharp cuter. The cutting edge was immediately hydrated by testing liquid to minimize bentonite loss. Bentonite paste, the permeate liquid, and silicon grease were applied around the perimeter of the GCL to reduce the potential for sidewall l eakage. A 483 kPa back pressure and a 550 kPa cell pressure were used for GCL specimens saturation, hydration, swell, and consolidation in 72 hours. During permeation, a

PAGE 43

43 pressure of 15 kPa across the specimen was maintained. The ratio of the rate of inflow to the rate of outflow was between 0.75 and 1.25 for the last three consecutive flow measurements. Hydraulic conductivity was calculated as per ASTM D 5084 using the Equation 21. Results and D iscussion Test R esults Batch leaching test with MSW landf ill leachate. Batch leaching test solutions were analyzed for cations, anions of SO4 2-, and TDS concentration changes. The results are presented in Figures 31 to 33. The quantities of most cations in the batch leaching test solutions were similar to those in MSW Landfill leachate, except calcium and strontium. Ca2+ concentrations in the batch leaching test solutions were 100 times higher than those in the MSW landfill leachate values presented in Figure 31. SO4 2concentrations in the leachate ranged from 3,000 to 3,250 mg/L, 15 times higher than those from the MSW landfill leachate, which had a sulfate concentration of 195 mg/L. TDS measured in the batch leaching test solutions ranged from 9,3509,500 mg/L, which is slightly higher than the TDS conc entrations of 6,300 mg/L found in the MSW leachate. More cations exchange data of the batch leaching solution are presented in Table A 12 to A 15. Column test. The column test results of compacted PG samples with MSW landfill leachate and DI water are presented in Figures 34 to 37. The hydraulic conductivity of compacted PG to MSW landfill leachate increased for the first four pore volumes of MSW leachate. After four pore volumes of MSW leachate passed through the columns, hydraulic conductivity of PG samples stabilized at 6.6 x 105 cm/sec or lowered into the range of 2.8 x 10 5 to 6.6 x 105 cm/sec. The hydraulic conductivity values achieved

PAGE 44

44 using DI water were relatively lower, and ranged from 1.8 x 10 5 to 2.7 x 105 cm/sec. The test results showed that the hydraulic conductivity of compacted PG specimen when using MSW landfill leachate as a permeate are higher than values achieved when using DI water as a permeate. The hydraulic conductivity of PG samples when exposed to DI water in column test s was similar to the values calculated in the triaxial permeameter tests in the Section 3 of Chapter 2. The average saturation degree of PG specimens after test, with MSW landfill leachate in the column test was 91%, and with DI water was 78%. In the column test with MSW landfill leachate, the pH and specific conductivity of the effluent solutions also changed over the range of pore volumes passing the PG specimens. In the first pore volume of MSW landfill leachate passing the PG specimen the pH was low er, at 3.1, than the MSW landfill leachate pH of 8.1. After the second pore volume passed, the effluent solution pH stabilized at 7.4, and specific conductivity The test solution of MSW landfill leachate had a specif In contrast to the results with MSW leachate, all parameters measured with DI water showed relatively stable values over the period of the test. The average pH of effluent with DI water was about 3.5. The average specific values. Batch leaching test with GCL bentonite. The concentrations of Ca2+, Na+, and K+ changed significantly after the GCL bentonite batch leaching tests with DI water, MSW landfill leachate, and simulated PG leachate. The cation exchange results for Ca2+, Na+, and K+ are presented in Tables 31, 32, and 33. The concentration of Ca2+

PAGE 45

45 in simulated the PG leachate was reduced during the batch test with GCL bentonite. Initia l Ca2+ concentrations in simulated PG leachate ranged from 745 mg/L to 861 mg/L, however as result of GCL batch leaching tests, the concentrations decreased to a range of 166 303 mg/L. In contrast, Na+, and K+ concentrations in simulated PG leachate incr eased significantly. During this test, Na+ concentrations increased by 400500 mg/L from an initial average value of 9 mg/L. Sodium concentrations increased in MSW leachate and DI water as well but the change was not as significant as in the simulated PG solutions. Additionally, potassium concentrations in increased DI water and PG leachate solutions, yet decreased in MSW leachate solutions. GCL hydraulic conductivity test. The test results of GCL hydraulic conductivities when permeated by DI water, MSW landfill leachate, and simulated PG leachate are presented in Figure 311. Compared to GCL hydraulic conductivity tested using DI water as a permeate, MSW landfill leachate and simulated PG leachate had an increased hydraulic conductivity. GCL hydraulic conductivity with DI water ranged from 2.3 x 109 to 4.1 x 109 cm/sec. GCL hydraulic conductivities with simulated PG leachate varied from 1.2 x 106 to 3.6 x 109 cm/sec. Most hydraulic conductivities with simulated PG leachate were greater than those with DI water. The highest GCL hydraulic conductivities were observed with MSW landfill leachate. GCL hydraulic conductivities with MSW leachate ranged from 6.4 x 106 to 1.8 x 107 cm/sec. Chemical properties of the permeates are summarized in Table 31. Compatibility with MSW Landfill Leachate The batch test of PG samples with MSW landfill leachate showed increased calcium, sulfate, and TDS concentrations in batch leaching solution. Increased calcium could cause scaling problems within the leachate c ollection and removal system.

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46 VanGulck et al. (2003) researched calcium carbonate (CaCO3) precipitation from leachate and its accumulation within the pore space of the drainage medium. Calcium precipitation is caused by the anaerobic fermentation of volat ile fatty acids, which adds carbonate to and raises the pH of the leachate. Another major concern in the batch test was the increased sulfate in the leaching solution. Under anaerobic conditions sulfate could be converted to hydrogen sulfide (H2S) which results in odor problems and possible health concerns at many disposal facilities. In Lee et al. (2005) research on C&D landfills showed biological conversion of sulfate from disposed gypsum drywall to H2S in the anaerobic C&D landfill environment. Howev er, Shieh (1999) reported that concentrations of calcium and sulfate were higher than in the typical landfill leachate, but no elevated level of H2S in the gas composition was found. The Increased TDS values in the batching solution showed that PG samples dissolved in MSW landfill leachate and released cations which could affect landfill leachate quality. In the column test, the hydraulic conductivity of the compacted PG with MSW landfill leachate was slightly higher than DI water after stabilization. That indicated that test liquid chemical properties, such as, pH, specific conductivity, could affect compacted PG hydraulic conductivity. I n this test the h ydraulic conductivity of PG with MSW landfill leachate and DI water were in the same order of magnit ude of 105 cm/sec. Compatibility with GCL s The key cations typically found in GCL batch leaching solutions were sodium, potassium, calcium, magnesium (Mg2+), and aluminum (Al3+). Sodium and potassium exchange in GCL bentonite in contact with simulated PG leachate and MSW landfill leachate could have an impact on hydraulic conductivity of GCLs. These changes in

PAGE 47

47 cation concentrations are influenced by multiple factors of MSW leachate and PG leachate quality such as ionic strength, pH, and the presence of organic compounds. Chemical interactions and their effect on the hydraulic conductivity of bentonite in GCLs have been studied by many researchers (Jo et al. 2001; Wang and Benson, 1999; Petrov et al. 1997; Petrov and Rowe, 1997). The results are summarize d in Table 32. Concentrations of cations in permeate are known to be very influential on hydraulic conductivity of GCLs. Kolstad et al. (2004) concluded that hydraulic conductivity of GCLs is a function of ionic strength and RMD of chemical solution or l eachate. Simulated PG leachate has a low RMD, i e a low ratio of monovalent, such as, sodium or potassium concentrations relative t o the concentration of divalent, such as, calcium. Thus high concentrations of calcium in PG leachate, and high ionic str ength of MSW landfill leachate caused adverse effects on GCL bentonite, i.e., GCL bentonite swelling, leading to effects on GCL hydraulic conductivity. However, there was no evidence, in this study, showed that PG leachate could increase hydraulic conduct ivity of GCLs greater than MSW landfill leachate did. Summary In the batch test PG with MSW landfill leachate, elevated Ca2+, SO4 2and TDS levels were observed in batch leaching solutions High concentrations of Ca2+ in landfill leachate could cause clogging in the leachate collection removal system and high levels of SO4 2could cause landfill gas odor and possible health concerns. The batch test results do not suggest that PG could be used as daily or intermediate cover soil layers as part of the operation of a MSW landfill. In the column test, hydraulic conductivity of compacted PG s amples with MSW landfill leachate are slig htly higher than those with DI water, but they are in the same order of magnitude of 105 cm /sec

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48 Hydraulic conductivities of G CL increased with simulated PG leachate (1.2 x 106 to 3.6 x 109 cm/sec) and MSW landfill leachate (6.4 x 106 to 1.8 x 107 cm/sec) compared to the tests with DI water (2.3 x 109 to 4.1 x 109 cm/sec). GCL betonite batch leaching tests showed that cati on concentrations in simulated PG leachate and MSW landfill leachate influence GCL hydraulic conductivity T hese test results showed that PG leachate could impact the hydraulic conductivity of GCLs when it applied as landfill sub base material, but no evi dence was found that PG leachate could increase hydraulic conductivity of GCLs greater than that of MSW landfill leachate.

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49 Table 3 1 Hydraulic conductivity of GCL permeant chemical properties Permeate type pH Specific Conductivity (s/cm) Ionic strengt h (M) Monovalent concentration (M) Divalent concentration (M) RMD b (mM 1/2 ) MSW Landfill Leachate 7.97 12,670 0.17 0.0894 0.0036 1.4803 SW PG leachate 6.25 2,582 0.03 0.0004 0.0203 0.0028 WW PG leachate 6.20 2,571 0.03 0.0008 0.0207 0.0053 NW PG leachat e 4.61 2,233 0.03 0.0006 0.0219 0.0038 EW PG leachate 5.55 2,256 0.03 0.0003 0.0199 0.0020 DI water 7.16 4 naa na na na a N ot available b RMD: RMD is defined as Mm/ ( Md1/2) where Mm = total molarity of monovalent cations and Md = total molarity of mult ivalent cations in the solution, and represents the relative abundance of monovalent and multivalent cations at a given ionic strength.

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50 Table 3 2 GCL Hydraulic conductivity in this study and the previous researchs Test Method Permeability (cm/sec) Perme ate type Confining pressure ( kPa ) Hydraulic gradient References ASTM D5084, D6766 2.3 x 109 4.1 x 109 DI water 69 149 194 In this study 6.4 x 106 1.8 x 107 MSW landfill leachate 1.2 x 106 3.6 x 109 Simulated PG leachate ASTM D5084 D6766 1.0x105 8.9x1010 Chemical solution n a 100 Jo et al. 2001 ASTM D6766 1 .0 x 107 simulated MSW leachate 3 5 100 200 Ruhl et al. 1997 2 .0 x 108 MSW landfill leachate 9 .0 x 1010 Tap water Constant flow rate fixed ring 2.6x105 7.3x1010 NaCl n a 18 2,142 Petrov et al. 1997 ASTM D6766 4.2x1012 2.7x109 DI water 41 175 440 Wang et al. 1999 Fixed ring Double ring 1.4x108 7.1x1010 DI/tap water 3 1 1 7 318 893 Petrov et al. 1997 N ot available

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51 Calcium (mg/L) 0 200 400 600 800 1000 1200 1400 SWPG + MSW landfill leachate WWPG + MSW landfill leachate NWPG + MSW landfill leachate EWPG + MSW landfill leachateMSW landfill leachate Figure 3 1 Calcium concentration s in the batch leaching soultions of PG with MSW landfill leachate Sulfate (mg/L) 0 1000 2000 3000 4000 5000 SWPG + MSW landfill leachate WWPG + MSW landfill leachate NWPG + MSW landfill leachate EWPG + MSW landfill leachateMSW landfill leachate Figure 3 2 Sulfate concentrations in the batch leaching solutions of PG with MSW landfill leachate

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52 TDS (mg/L) 0 2000 4000 6000 8000 10000 12000 SWPG + MSW landfill leachate WWPG + MSW landfill leachate NWPG + MSW landfill leachate EWPG + MSW landfill leachateMSW landfill leachate Figure 3 3. TDS in the batch leaching solutions of PG with MSW landfill leach ate

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53 1E-5 2E-5 3E-5 4E-5 5E-5 DI water MSW landfill leachate MSW landfill leachate-duplicate Hydraulic Conductivity (cm/sec) 1 2 3 4 5 6 7 8 pH 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 18 Accumulated pore volume Specific Conductivity (mS/cm) Figure 3 4. Hydraulic conductivity, pH, and specific conductivity of the SWPG in column test. One pore volume of the SW PG specimen equals to 344 mL.

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54 1E-5 2E-5 3E-5 4E-5 5E-5 6E-5 7E-5 DI water MSW landfill leachate MSW landfill leachate-duplicate Hydraulic Conductivity (cm/sec) 1 2 3 4 5 6 7 8 pH 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 18 20 22 Accumulated pore volume Specific Conductivity (mS/cm) Figure 3 5. Hydraulic conductivity, pH, and specific conductivity of the WWPG in column test. One pore volume of the WW PG specimen equals to 357 mL.

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55 9E-6 2E-5 3E-5 4E-5 5E-5 DI water MSW landfill leachate MSW landfill leachate-duplicate Hydraulic Conductivity (cm/sec) 1 2 3 4 5 6 7 8 pH 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 Accumulated pore volume Specific Conductivity (mS/cm) Figure 3 6. Hydraulic conductivity, pH, and specific conductivity of the NW PG in column test. One pore volume of the NWPG specimen equals to 381 mL

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56 1E-5 2E-5 3E-5 4E-5 5E-5 6E-5 7E-5 DI water MSW landfill leachate MSW landfill leachate-duplicate Hydraulic Conductivity (cm/sec) 1 2 3 4 5 6 7 8 pH 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 18 20 22 Accumulated pore volume Specific Conductivity (mS/cm) Figure 3 7. Hydraulic conductivity, pH, and specif ic conductivity of the EW PG in column test. One pore volume of the EWPG specimen equals to 387 mL

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57 10 100 1000 GCL+DI water GCL+MSW landfill leachate GCL+NWPG leachate GCL+SWPG leachate GCL+EWPG leachate GCL+ WWPG leachateCalcium (mg/L)MSW landfill leachate= 113mg/L PG leachate= 791mg/L Figure 3 8. Calcium concentration s in batch leaching test of GCL bentonite with DI water, MSW landfill leachate, and simulated PG leachate 1 10 100 1000 10000 GCL+DI water GCL+MSW landfill leachate GCL+NWPG leachate GCL+SWPG leachate GCL+EWPG leachate GCL+ WWPG leachateSodium (mg/L) MSW landfill Leachate= 1630 mg/L PG Leachate= 9 mg/L Figure 3 9 S o dium concentration s in batch leaching test of GCL bentonite with DI water, MSW landfill leachate, and simulated PG leachate

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58 1 10 100 1000 GCL+DI water GCL+MSW landfill leachate GCL+NWPG leachate GCL+SWPG leachate GCL+EWPG leachate GCL+ WWPG leachatePotassium (mg/L) MSW landfill Leachate= 744 mg/L PG Leachate= 3 mg/L Figure 3 10. P otassium concentrations in batch leaching test of GCL bentonite with DI water, MSW landfill leachate, and simulated PG leachate DI water Hydraulic conductivity (cm/sec) 1e-10 1e-9 1e-8 1e-7 1e-6 1e-5 1e-4 MSW landfill leachate SWPG leachate WWPG leachate NWPG leachate EWPG leachatePermeant type Figure 3 11 GCL hydraulic conductivity to simulated PG leachate, MSW landfill leachate, and DI water

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59 CHAPTER 4 SHEAR STRENGTH OF MSW WITH DIFFERENT FOO D WASTE CONTENT Landfill slope stability design requires the evaluation of compacted MSW shear strength properties, e.g., the internal friction angle and cohesion. Research investigating appropriate MSW internal friction angles and cohesions have been reported, with most values reported in the range of 15 to 36 (Kavazanjian et al. 1995; Kavazanjian et al. 1999; Machado et al. 2002; Mahler et al. 2003; Harris et al. 2006; Gabr et al. 2007; Zhan et al. 2007; Zekkos et al. 2007; Kavazanjian 2008; Zekkos et al. 2008; Reddy et al. 2009; Cho et al. 2011 ). The wide range of values is caused by numerous factors such as the test methods, test conditions, waste composition, waste age, decomposition degree, and preprocessing methods. The composition of MSW varies with geographical, cultural, and seasonal differences. Food waste content, for example, can vary dramatically among countries. The food waste content of U.S. MSW is approximately 12.5% as determined by its water content (USEPA, 2005), while that of China has been reported to be as high as 73% (The World Bank, 1999; Wang et al. 2001). Most of the studies referenced earlier were focused on waste from western countries. As other parts of the world with different waste compositions begin to utilize large sanitary landfills, it is important to better understand how different fac tors, such as high food waste content waste, might impact the waste shear strength properties. This study investigated the relationship between the MSW internal friction angle and food waste content. Laboratory direct shear tests were performed on synthet ic MSW with different food waste contents, under a maximum 16 cm displacement.

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60 Materials and Methods MSW Specimen Preparation Sample collection. In this study, synthetic MSW samples were prepared to represent common waste characteristics. Eight representative components were selected: food waste, paper, plastic, metal, wood, textile, glass, and ash (Table 41). Here, paper, plastic, aluminum, and glass components were collected from the University of Florida recycling center. Chipped wood mulch of appropriate sizes was collected from a local waste transfer station. Textiles used were discarded clothes. Coal ash was collected from a local coal fueled power plant (Gainesville Regional Utilities, FL US). Food waste was collected from the University of Florida dining halls. A visual observation was used to ascertain that the general characteristics of all waste components. Sample processing. The target sizes, methods of size reduction, and average moisture contents for the different waste components are summarized in Table 42. Paper components consisted of 50% office paper and 50% newspaper which were cut to 14 cm length and 22 cm width pieces. Plastics consisted of 50% plastic bottles and 50% plastic film. Plastics, aluminum beverage cans, glass and textile were reduced to less than 15 cm. Food waste consisted primarily of discarded meats, pizza, bread, and vegetables. The average food waste moisture was 63.5%. Size reduction was not performed on food waste. Specimen preparation. Direct shear test spe cimens were prepared by mixing all waste components and compacting in the shear box. All waste components were thoroughly mixed with shovels in a stainless steel tank to promote a homogenous composition for the shear tests. Then the mixture was placed an d compacted in the

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61 shear box. All test specimen and waste components were determined on a wet weight basis. Drying temperature was set at 60C to avoid combustion of volatile material (Reddy et al. 2009). The average moisture contents of each waste component and specimen are presented in Tables 42 and 43, respectively. The initial moisture content of each specimen, before consolidation occurred, was estimated by taking the weighted average moisture content of each component. Direct Shear Test Direct s hear tests were conducted to determine the angle of internal friction and cohesion of fresh MSW at different food under drained condition. Tests were performed in accordance with ASTM D3080 in a large scale rectangular shear box with dimensions 43cm width, 43 cm length, and 61cm height. The shear box includes an upper fixed shear box (43cm length 43cm width 46cm height) and a movable lower shear box (43cm length 43cm width 16cm height). The maximum displacement level of the largescale devic e is approximately 40% of the shear box length (16 cm of horizontal displacement). For normal stress and shear stress applications, hydraulic jacks equipped with hand pumps (SIMPLEX P42 and P82, Broadview, Illinois, U.S.) and pressure gauges (GD1 SIMPLEX, Broadview, Illinois) were used. The stress controlled direct shear box was designed as shown in Figure B 4 (Stewart & Associates Manufacturing Corporation, Gainesville, Florida, U.S.). Each direct shear test was initiated by placing and compacting a wellmixed MSW specimen in the shear test box. The normal stresses applied on the specimen were 96, 192, and 287 kPa, respectively. The applied normal stresses on the MSW specimens were treated as the effective normal stresses under drained conditions. Shear test specimens were consolidated under effective normal stress within a 24 hour period until

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62 vertical deformation rates were less than 0.5% per hour. The normal stress was continuously monitored and maintained at a constant value during the consolidat ion and testing procedures. Shear stress was applied at the constant shear speed 0.5 cm/min, and shear stress and horizontal displacement were monitored and recorded. Each shear test was terminated after maximum horizontal displacement of 16 cm was reached. Densities of the specimens after consolidation and before shearing are provided in Table 43. Dry density was calculated by subtracting the moisture weight from the total weight of a specimen. Data Analysis In direct shear tests internal friction angle and cohesion were estimated using peak or ultimate shear strength values produced during the test. That is to say, the highest value within the relevant range was used, although sometimes the process was terminated while the shear strength was still increasing. In this latter case, the final measured values were used. The Mohr Coulomb failure criterion expressed as Equation 21 was used to calculate the shear strength parameters. To develop a Mohr Coulomb failure criterion envelope for each set of di rect shear test data, a best fit linear regression was performed. For all 24 tests duplicates were conducted at each normal stress and food waste content. All of the replicate data points for each set of tests were used to develop the regression line. The cohesion values were also determined from shear strength vs. normal stress plots. Mobilized shear strength, cohesion, and internal friction angle at various displacements were calculated to investigate the relationship between displacement and mobilized shear strength parameters. Based on the stress displacement data, mobilized internal friction angles of MSW were estimated at horizontal displacements of

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63 22 mm (or 5% of the total), 43 mm (10%), 65 mm (15%), 86 mm (20%), 108 mm (25%), and 129 mm (30%). Results a nd Discussion StressDisplacement Response Stress displacement curves are presented in Figures 41, 42, and 43. Twelve out of 24 direct shear tests, with 50% and 70% food waste content, showed the fully mobilized, well defined peak shear strength. Under a stress of 297 kPa, peak shear strengths were achieved at 8 cm (17%) and 16 cm (27%) respectively. In the remaining 12 tests, with 0 and 20% food waste content, the stress displacement response did not reach their peak shear strengths even at the maximum displacement of 16 cm (37%) which were similar with previous results (Pelkey et al. 2001; Vilar and Carvalho 2004; Reddy et al. 2009). For these tests the maximum shear strength values at a displacement of 16 cm (37%) were considered as the peak shear strength and those were used to develop Mohr Coulomb failure criteria envelopes. Change of Internal Friction Angle Mohr Coulomb criteria envelopes were plotted using the peak or maximum shear strength values produced in the 24 direct shear test s. In Figure 44 the envelopes showed that mobilized internal friction angles decreased with increasing food waste content. The increasing degrees varied for different food waste content MSW. The internal fiction angle decreased from 35 to 33 od waste content increasing from 0 to 20%. The internal fiction angle decreased from 33 to 30 When the food waste continued increasing from 50 to 70%, internal frication dramatically dropped from 30 to 15e ratio of food to

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64 other components became more dominant, internal friction angles changed more significantly. The values of the mobilized internal friction angle and the mobilized cohesion at different displacement levels with different food waste content s were summarized in Table 45. At each displacement level from 5 to 30% the internal friction angle decreased with increasing food waste content, as shown in Figure 44. However, there was no evidence that there was an overall change of cohesion by increasing food waste content. This was different with the test results from Cho et al. (20 11) who reported that overall cohesion increased with increasing displacement level. Relationship of internal friction angle and cohesion with food waste content was attem pted to be determined based on results of this study and Cho et al. (2011 ) test results. Figure 46 showed that there was a significant trend of the internal friction angle decreasing with the food waste content increasing in MSW. The best fit internal friction angle envelope is plotted in Figure 46. To summary the relationship of the internal friction angle with the food waste content the bilinear envelope should be used. The bi linear internal friction angle envelope showed that: if food waste cont ents less than 50%, an additional 10% of food waste causes a decrease of approximately 1.7 degrees of internal friction (Equation 41) and if higher than 50%, an additional 10% of food waste cause a decrease of approximately 6 degrees of internal friction (Equation 42) = 36.5-0.17(100x) (4 -1 ) = 58.0-0.60(100x) (4 -2 ) W here, (%) by wet base.

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65 Application t o Landfill Slope Stability Design MSW Internal friction angle and cohesion in the this study were compared to those from previous tests (Kavazanjian et al. 1999; Machado et al. 2002; Harris et al. 2006; Reddy et al. 2009; Cho et al. 201 1). Reported internal friction angles ranged from 7 to 39 and cohesion ranged from 0 to 65 kPa as shown in Figure 4 7. This wide range of values can be caused by numerous factors which influenced the test results including the test methods, test conditions, waste composition, waste age, decomposition degree, and preprocessing methods. Internal friction angle values of 20 to 40 for MSW from western countries where the waste is more dominated by packaging materials and discarded domestic goods, and less by food waste. The design engineer would use an internal friction angle estimate as an input for a landfill slope stability design. Considering the food waste content in some regions has been reported as high as 70% (The World Bank, 1999; Wang et al. 2001) the typical friction angle values used for the design of a landfill in the U.S. could not be used properly. At very high food waste contents, internal friction angle does decrease to levels lower than expected for wastes with lower food contents. The results suggest that at food waste contents up to 50%, the friction angle will be close to the lower end of the typical range, with contents up to 70% the angle will be lower than the typical ranges used for design. Summary The shear strength properties of MSW with different food waste contents were investigated by conducting di rect shear tests with largescale direct shear testing devices. In the direct shear tests, the stress displacement response plots showed relatively welldefined peak shear strengths for all tested MSW with high food waste

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66 contents. Test results showed that the peak shear strength decreased with the increasing in food waste content under a given normal stress. Also, increasing food waste content resulted in a decreasing of the internal friction angles. The internal friction angle decreased down to 15 th an increased food waste content of up to 70%. The relationship of internal friction angle decrease with food waste content increase was summarized as bi linear relationship. The bi linear internal friction angle envelope showed that if the food waste c ontent in MSW is higher than 50%, the internal friction angle could drop more significant. These results suggest that the impact of high food waste content MSW on the internal friction angle should be considered when designing for landfill slope stability

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67 Table 4 1. Composition of MSW specimens Component Content (%) by wet weight Food 0.0 20.0 50.0 70.0 Paper 24.0 19.2 12.0 7.2 Plastic 22.7 17.8 11.2 6.8 Metal 4.0 3.2 2.0 1.2 Wood 11.3 8.9 5.6 3.4 Glass 6.0 5.0 3.1 1.8 Textile 8.7 6.9 4.3 2.6 A sh 23.3 19.0 11.8 7.0 Total 100.0 100.0 100.0 100.0

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68 Table 4 2. Sizes and moisture contents of each waste component Component Size limit Size reduction method Moisture content (%) Food No reduction 63.5 Paper 140 mm x 220mm Scissors 5.8 Plastic < 1 50 mm Scissors 3.7 Metal < 150 mm Scissors 1.8 Wood < 150 mm Hammer 32.5 Glass < 150 mm Hammer 2.9 Textile < 150 mm Scissors 6.0 Ash No reduction 27.2

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69 Table 4 3. Average moisture contents and dry densities of the MSW specimens Food waste content Moisture content (%) Dry density (kg/m3)c Initiala Finalb 96 kPa 192 kPa 287 kPa 0% 13.0 9.8 242 321 269 20% 23.1 25.1 282 356 403 50% 38.3 41.3 327 396 472 70% 48.4 51.6 319 457 550 a Measured before consolidation b Measur ed after testing shear str ength c Measured after consolidation and before shearing

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70 Table 4 4. Mobilized internal friction angle and cohesion values Relative displacementa Parameter Food waste content (%) 0 20 50 70 5% Internal friction ( 21 24 21 16 Cohesion (kPa) 4 0 4 0 10% Internal friction ( 27 29 27 16 Cohesion (kPa) 6 1 2 6 15% Internal friction ( 30 31 29 16 Cohesion (kPa) 6 1 2 9 20% Internal friction ( 33 32 30 16 Cohesion (kPa) 3 3 0 10 25% Internal friction ( 35 34 29 15 Cohesion (kPa) 0.5 2 5 11 30% Internal friction ( 36 34 27 16 Cohesion (kPa) 0.5 3 9 8 Peakb Internal friction ( 35 33 30 15 Cohesion (kPa) 6 7 5 12 a Relative displacement represents the relative horizontal displacement of a specimen b Peak represents the peak shear strength v alues or maximum shear strength

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71 0 20 40 60 80 100 0 2 4 6 8 10 12 14 16 18 0% 0% duplicate 20% 20% duplicate 50% 50% duplicate 70% 70% duplicate Horozontal displacement (cm) shear stress (kPa) Figure 41. Stress displacement response curves of direct shear tests with 0, 20, 50, and 70% of food waste specimens under 96 kPa of effective normal stress 0 40 80 120 160 200 240 0 2 4 6 8 10 12 14 16 18 0% 0% duplicate 20% 20% duplicate 50% 50% duplicate 70% 70% duplicate Horozontal displacement (cm) shear stress (kPa) Figure 42. Stress displacement response curves of direct shear tests with 0, 20, 50, and 70% of food waste specimens under 192 kPa of effective normal stress

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72 0 50 100 150 200 250 300 0 2 4 6 8 10 12 14 16 18 0% 0% duplicate 20% 20% duplicate 50% 50% duplicate 70% 70% duplicate Horozontal displacement (cm) shear stress (kPa) Figure 43. Stress displacement response curves of direct shear tests with 0, 20, 50, and 70% of food waste specimens under 287 kPa of effective normal stress c = 6, = 35 c = 7, 3 c = 5, 0 c = 12, 12 0 50 100 150 200 250 300 0 100 200 300 400 0% Food waste 20% Food waste 50% Food waste 70% Food waste Normal stress (kPa) shear stress (kPa) Figure 44. Mohr Coulomb failure envelopes of direct shear tests. Data points correspond to peak shear strengths under each effective normal stress and at each waste composition; each line was derived by a best fit linear regression

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73 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 80 5% 10% 15% 20% 25% 30% Internal friction ( Food waste content (%) Relative displacement Figure 45. Impact of food waste contents in synthetic fresh MSW on friction angles at different displacement levels y = 0.17x + 36.49 R = 0.75 y = 0.60x + 58.00 R = 0.86 0 10 20 30 40 50 0 10 20 30 40 50 60 70 80 90 100 Internal friction ( in this study Internal friction ( Cho et al. 2011 Internal friction ( Food waste content (%) Figure 46. Relationship of MSW internal friction and cohesion by direct shear tes t with different food waste contents

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74 0 10 20 30 40 50 60 70 0 10 20 30 40 50 0% food waste, in this study 20% food waste, in this study 50% food waste, in this study 70% food waste, in this study Cho et al. 2011, fresh waste, 0%-80% food waste Reddy et al. 2009, fresh waste Harris 2008, < 2 years Harris et al. 2006, >10 years Machdo et al. 2002, about 15 years, at 20% strain Kavazanjian et al. 1999, 11-35 years Internal friction angles ( Cohesion (kPa) Figure 47. Comparison of values of internal friction angle and cohesion values in this study to those of in previous studies

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75 CHAPTER 5 SUMMARY AND CONCLUSI ONS In Chapter s 2 and 3 of this thesis, the feasibility of utilizing phosphogypsum ( PG ) in lined MSW landfills structural material was evaluated. Applications could include use of PG as daily landfill cover material, and, at new landfill sites, compacted PG could possibly substitute for the large volume of soil r equired to be placed under the liner to provide the needed grades for leachate drainage. The applicability has been judged by testing PG geotechnical engineering properties and PG compatibility with MSW landfill leachate and geosynthetic clay liners ( GCLs ) Test results of PG geotechnical properties showed that PG has the geotechnical properties to serve as landfill foundation material as compared to compacted clay. PG dry unit densities are in the typical range of finegrained soil unit dry densities, and the internal friction angles of compacted PG are slightly greater than those typical of compacted clay. However, PG hydraulic conductivity test results didnt support the idea that compacted PG could singly serve as subbase soil. A GCL with a hydrauli c conductivity not greater than 1x107 cm/sec could be used on top of PG. The batch leaching test results didnt suggest that PG could be used as daily cover soil layers as part of the operation of a MSW landfill. In the PG with MSW landfill leachate solution, elevated calcium, sulfate, and TDS concentrations were observed which could clog landfill leachate collection systems, causing landfill gas odor or possible health concerns. In the column test, the hydraulic conductivity of compacted PG when permeat ed with MSW landfill leachate is slightly higher than that of DI water, but is in the same order of magnitude of 105 cm/sec. GCL batch leaching tests with PG leachate results showed that calcium cation exchange with GCL bentonite could impact

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76 the GCL hydraulic conductivity. Hydraulic conductivities of GCLs increased with simulated PG leachate (1.2 x 106 to 3.6 x 109 cm/sec), and this range overlapped with Florida Landfill Rules (FDEP, 2010) required limit of the 107 cm/sec. These test results showed that PG leachate could impact the hydraulic conductivity of GCLs when it applied as landfill sub base material, but no evidence showed that PG leachate could increase hydraulic conductivity of GCLs greater than that of MSW landfill leachate. In Chapter 4 the impacts of food waste content on the shear strength properties of MSW were investigated by conducting largescale direct shear tests. In the 24 direct shear tests, the residual shear strength decreased with increasing in food waste contents for a given normal stress. Also, increases in food waste content resulted in decreases in the internal friction angles. The internal friction angle decreased to 15 with an increased food waste content of 70%. The bi linear internal friction angle envelope showed that if the food waste content in MSW is higher than 50%, the internal friction angle could drop dramatically.

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77 APPENDIX A SUPPLEMENTAL TABLES Table A 1. PG sieve analysis test data Sample Sieve No. Diameter (mm) Mass of sieve (g) Mass of sieve +soil (g) Retained Soil (g) Retained percent (%) Passing percent (%) SWPG 10 2.000 416.9 417.0 0.1 0.0 100.0 20 0.850 399.5 402.1 2.6 0.8 99.1 4 0 0.420 462.9 472.4 9.5 3.1 96.1 60 0.250 328.7 349.9 21.2 6.8 89.2 100 0.150 343.6 401.3 57.7 18.6 70.6 200 0.075 339.0 420.8 81.8 26.4 44.2 Pan 0 370.8 507.9 137.1 44.2 0.0 WWPG 10 2.000 417.0 417.7 0.7 0.2 99.8 20 0.850 399.6 404.4 4.8 1.5 98 .2 30 0.420 409.5 412.5 3.0 1.0 97.3 50 0.250 364.5 375.4 10.9 3.5 93.8 100 0.150 343.8 401.4 57.6 18.4 75.4 200 0.075 339.0 422.0 83.0 26.5 48.9 Pan 0 370.9 523.9 153.0 48.9 0.0 NWPG 10 2.000 417.0 417.0 0.0 0.0 100.0 20 0.850 399.6 403.0 3.4 1.0 99.0 30 0.420 409.5 414.3 4.8 1.5 97.5 50 0.250 364.5 374.5 10.0 3.1 94.4 100 0.150 343.7 364.5 20.8 6.4 88.0 200 0.075 339.0 387.0 48.0 14.8 73.2 pan 0 370.9 608.0 237.1 73.1 0.0 EWPG 10 2.000 417.0 417.1 0.1 0.0 100.0 20 0.850 399.6 404 .2 4.6 1.4 98.6 30 0.420 409.4 413.5 4.1 1.2 97.4 50 0.250 364.5 370.4 5.9 1.8 95.6 100 0.150 343.8 368.1 24.3 7.3 88.4 200 0.075 339.0 411.4 72.4 21.6 66.7 pan 0 371.0 593.5 222.5 66.5 0.0

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78 Table A 2. PG standard compaction test data Sample S pecimen No. 1 2 3 4 5 6 7 8 9 10 SWPG Weight of mold (g) 2018 2018 2018 2018 2018 2018 2018 2018 2019 2018 Weight of mold + soil (g) 3620 3646 3678 3703 3738 3722 3705 3711 3672 3685 Weight of soil in mold (g) 1602 1629 1660 1686 1720 1704 1687 1693 1 653 1667 Dry unit weight (kg/m3) 1520 1548 1536 1507 1457 1512 1535 1559 1509 1464 Zero air void (kg/m3) 1768 1711 1650 1622 1580 1809 1737 1670 1617 1571 Water content (%) 13.8 15.6 17.8 18.9 20.5 12.5 14.8 17.1 19.0 20.9 WWPG Weight of mold (g) 2016 2018 2016 2018 2016 2018 2016 2018 2019 2016 Weight of mold + soil (g) 3618 3646 3664 3703 3708 3722 3702 3705 3672 3649 Weight of soil in mold (g) 1602 1629 1648 1686 1691 1704 1686 1687 1653 1633 Dry unit weight (kg/m3) 1497 1504 1516 1494 1450 1498 1517 1534 1505 1406 Zero air void (kg/m3) 1769 1709 1657 1615 1572 1782 1727 1677 1627 1517 Water content (%) 13.9 15.9 17.8 19.3 21.0 13.5 15.3 17.0 18.9 23.3 NWPG Weight of mold (g) 2017 2017 2018 2017 2018 2017 2018 2018 2018 2018 Weight of mold + soil (g) 3544 3588 3600 3632 3648 3668 3657 3651 3633 3636 Weight of soil in mold (g) 1526 1570 1582 1615 1630 1650 1639 1633 1615 1618 Dry unit weight (kg/m3) 1424 1436 1454 1464 1429 1439 1455 1436 1393 1376 Zero air void (kg/m3) 1714 1649 1 603 1558 1518 1633 1576 1524 1479 1442 Water content (%) 13.8 16.1 17.9 19.7 21.4 16.7 18.9 21.1 23.1 24.8 EWPG Weight of mold (g) 2018 2017 2018 2017 2017 2017 2017 2017 2017 2017 Weight of mold + soil (g) 3543 3567 3580 3616 3614 3656 3654 3640 3644 3621 Weight of soil in mold (g) 1525 1551 1563 1599 1597 1639 1637 1623 1627 1604 Dry unit weight (kg/m3) 1422 1432 1436 1453 1423 1425 1444 1461 1429 1381 Zero air void (kg/m3) 1712 1657 1600 1559 1517 1665 1612 1572 1536 1475 Water content (%) 1 3.9 15.8 18.0 19.6 21.4 15.6 17.5 19.1 20.6 23.3

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79 Table A 3. Hydraulic conductivity test data for SWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pr essure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 91.1% 72.0 0.0 6.3 70.0 24.0 17.7 184 15.06 5.7E 05 2 80.0 70.0 91.1% 72.0 6.3 11.9 70.0 17.7 12.1 184 13.93 5.5E 05 3 80.0 70.0 91.1% 72.0 11.9 17.0 70.0 12.1 6.9 184 12.91 5.5E 05 Average 5.6E 05 4 100.0 70.0 91.1% 72.0 0.0 5.0 70.0 24.0 19.0 183 15.18 4.5E 05 5 100.0 70.0 91.1% 72.0 5.0 9. 7 70.0 19.0 14.3 183 14.26 4.5E 05 6 100.0 70.0 91.1% 72.0 9.7 14.0 70.0 14.3 10.0 183 13.40 4.4E 05 Average 4.5E 05 7 120.0 70.0 91.1% 72.0 0.0 4.4 70.0 24.0 19.6 183 15.24 4.0E 05 8 120.0 70.0 91.1% 72.0 4.4 8.5 70.0 19.6 15.5 1 84 14.43 3.9E 05 9 120.0 70.0 91.1% 72.0 8.5 12.3 70.0 15.5 11.7 183 13.68 3.8E 05 Average 3.9E 05 a PG specimen final water content (%), 20.2; length (cm), 10.52; and diameter (cm), 7.10 b W ater height in burette

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80 Table A 4 H ydraulic conductivity duplicate test data for SWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 91.1% 72.0 0.0 7.0 70.0 24.0 17.1 185 14.67 6.5E 05 2 80.0 70.0 91.1% 72.0 7.0 13.2 70.0 17.1 10.8 186 13.44 6.3E 05 3 80.0 70.0 91.1% 72.0 13.2 18.7 70.0 10.8 5.3 184 12.35 6.1E 05 Average 6.3E 05 4 100.0 70.0 91.1% 72.0 0.0 5.7 70.0 24.0 18.3 182 14.78 5.4E 05 5 100.0 70.0 91.1% 72.0 5.7 10.9 70.0 18.3 13.1 183 13.77 5.2E 05 6 100.0 70.0 91.1% 72.0 10.9 15.7 70.0 13.1 8.3 182 12.84 5.2E 05 Average 5.3E 05 7 120.0 70.0 91.1% 72.0 0.0 4.7 70.0 24.0 19.2 183 14.87 4.4E 05 8 120.0 70.0 91.1% 72.0 4.7 9.1 70.0 19.2 14.8 183 14.02 4.3E 05 9 120.0 70.0 91.1% 72.0 9.1 13.2 70.0 14.8 10.7 184 13.23 4.3E 05 Average 4.3E 05 a PG specimen final water content (%), 19.3; length (cm), 10.75; and diameter (cm), 7.09 b W ater height in burette

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81 Table A 5 Hydraulic conductivity test data for WWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 92.0% 72.0 0.0 7.8 70.0 24.0 16.2 121 21.79 7.4E 05 2 80.0 70.0 92.0% 72.0 7.8 14.5 70.0 16.2 9.5 120 19.77 7.0E 05 3 80.0 70.0 92.0% 72.0 14.5 20.5 70.0 9.5 3.6 121 18.02 6.8E 05 Average 7.1E 05 4 100.0 70.0 92.0% 72.0 0.0 7.4 70.0 24.0 16.5 120 21.84 7.1E 05 5 100.0 70.0 92.0% 72.0 7.4 14.0 70.0 16.5 9.9 120 19.89 6.9E 05 6 100.0 70.0 92.0% 72.0 14.0 19.8 70.0 9.9 4.1 120 18.16 6.6E 05 Average 6.9E 05 7 120.0 70.0 92.0% 72.0 0.0 6.8 70.0 24.0 17.2 121 21.93 6.4E 05 8 120.0 70.0 92.0% 72.0 6.8 12.8 70.0 17.2 11.1 120 20.14 6.2E 05 9 120.0 70.0 92.0% 72.0 12.8 18.2 70.0 11.1 5.7 121 18.55 6.0E 05 Average 6.2E 05 a PG specimen final water content (%), 21.5; length (cm), 7.20; and diameter (cm), 7.15 b W ater height in burette

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82 Table A 6 Hydraulic conductivity duplicate test data for WWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conduct ivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 85.0% 72.0 0.0 5.9 70.0 23.0 17.1 121 21.96 5.5E 05 2 80.0 70.0 85.0% 72.0 5.9 11.2 70.0 17.1 11.8 121 20.41 5.3E 05 3 80.0 70.0 85.0% 72.0 11.2 16.1 70.0 11.8 6.9 120 18.99 5.4E 05 Average 5.4E 05 4 100.0 70.0 85.0% 72.0 0.0 5.7 70.0 24.0 18.2 121 22.13 5.4E 05 5 100.0 70.0 85.0% 72.0 5.7 10.9 70.0 18.2 13.0 121 20.60 5.2E 05 6 100.0 70.0 85.0% 72.0 10.9 15.6 70.0 13.0 8.3 120 19.22 5.1E 05 Average 5.2E 05 7 120.0 70.0 85.0% 72.0 0.0 4.8 70.0 24.0 19.1 120 22.25 4.5E 05 8 120.0 70.0 85.0% 72.0 4.8 9.3 70.0 19.1 14.6 120 20.95 4.5E 05 9 120.0 70.0 85.0% 72.0 9.3 13.4 70 14.6 10.5 120 19.75 4.3E 05 Average 4.4E 05 a PG specimen final water content (%), 21.6; length (cm), 7.18; and diameter (cm), 7.15 b W ater height in burette

PAGE 83

83 Table A 7 Hydraulic conductivity test data for NWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Satur ation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 92.2% 72.0 0.0 4.3 70.0 24.0 19.7 121 22.45 4.0E 05 2 80.0 70.0 92.2% 72.0 4.3 8. 3 70.0 19.7 15.7 122 21.28 3.9E 05 3 80.0 70.0 92.2% 72.0 8.3 12.0 70.0 15.7 11.9 120 20.20 3.9E 05 Average 3.9E 05 4 100.0 70.0 92.2% 72.0 0.0 4.3 70.0 24.0 19.6 120 22.44 4.0E 05 5 100.0 70.0 92.2% 72.0 4.3 8.4 70.0 19.6 15.5 120 21.26 4.0E 05 6 100.0 70.0 92.2% 72.0 8.4 12.1 70.0 15.5 11.7 121 20.16 3.8E 05 Average 4.0E 05 7 120.0 70.0 92.2% 72.0 0.0 3.7 70.0 24.0 20.3 120 22.53 3.4E 05 8 120.0 70.0 92.2% 72.0 3.7 7.2 70.0 20.3 16.8 120 21.52 3.4E 05 9 120.0 70.0 92.2% 72.0 7.2 10.4 70.0 16.8 13.6 122 20.58 3.2E 05 Average 3.3E 05 a PG specimen final water content (%), 23.7; length (cm), 7.15; and diameter (cm), 7.13 b W ater height in burette

PAGE 84

84 Table A 8 Hydraulic conductivit y duplicate test data for NWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 91.0% 72.0 0.0 3.9 70.0 24.0 20.1 120 22.55 3.6E 05 2 80.0 70.0 91.0% 72.0 3.9 7.6 70.0 20.1 16.4 120 21.48 3.6E 05 3 80.0 70.0 91.0% 72. 0 7.6 11.1 70.0 16.4 12.9 120 20.47 3.5E 05 Average 3.6E 05 4 100.0 70.0 91.0% 72.0 0.0 3.5 70.0 24.0 20.4 121 22.60 3.2E 05 5 100.0 70.0 91.0% 72.0 3.5 6.9 70.0 20.4 17.0 121 21.62 3.2E 05 6 100.0 70.0 91.0% 72.0 6.9 10.1 70.0 17.0 13.8 121 20.70 3.2E 05 Average 3.2E 05 7 120.0 70.0 91.0% 72.0 0.0 3.3 70.0 24.0 20.6 120 22.63 3.1E 05 8 120.0 70.0 91.0% 72.0 3.3 6.4 70.0 20.6 17.5 120 21.72 3.0E 05 9 120.0 70.0 91.0% 72.0 6.4 9.4 70.0 17.5 14.6 120 20.87 2 .9E05 Average 3.0E 05 a PG specimen final water content (%), 21.6; length (cm), 7.13; and diameter (cm), 7.16 b W ater height in burette

PAGE 85

85 Table A 9 Hydraulic conductivity test data for EWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 89.0% 72.0 0.0 7.0 70.0 24.0 17.0 120 21.62 6.7E 05 2 80.0 70.0 89.0% 72.0 7.0 13.4 70.0 17.0 10.6 120 19.78 6.7E 05 3 80.0 70.0 89.0% 72.0 13.4 19.0 70.0 10.6 5.0 120 18.14 6.4E 05 Average 6.6E 05 4 100.0 70.0 89.0% 72.0 0.0 6.5 70.0 24.0 17.5 121 21.69 6.2E 05 5 100.0 70.0 89.0% 72.0 6.5 12.3 70.0 17.5 11.7 120 20.00 6.0E 05 6 100.0 70.0 89.0% 72.0 12.3 17.5 70.0 11.7 6.5 120 18.50 5.8E 05 Average 6.0E 05 7 120.0 70.0 89.0% 72.0 0.0 5.9 70.0 24.0 18.1 121 21.77 5.6E 05 8 120.0 70.0 89.0% 72.0 5.9 11.2 70.0 18.1 12.8 121 20.24 5.4E 05 9 120.0 70.0 89.0% 72.0 11.2 16.1 70.0 12.8 7.9 121 18.84 5.4E 05 Average 5.4E 05 a PG specimen fi nal water content (%), 25.0; length (cm), 7.29; and diameter (cm), 7.25 b W ater height in burette

PAGE 86

86 Table A 1 0 Hydraulic conductivity duplicate test data for EWPGa Test No. Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydrau lic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Saturation degree (%) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1 80.0 70.0 89.0% 72.0 0.0 5.4 70.0 24.0 18.6 121 22.24 5.0E 05 2 80.0 70.0 89.0% 72.0 5.4 10.4 70.0 18.6 13.6 120 20.79 5.0E 05 3 80.0 70.0 89.0% 72.0 10.4 14.8 70.0 13.6 9.2 121 19.48 4.6E 05 Average 4.9E 05 4 100.0 70.0 89.0% 72.0 0.0 5.1 70.0 24.0 18.9 121 22.28 4.7E 05 5 100.0 70.0 89.0% 72.0 5.1 9.7 70.0 18.9 14.2 121 20.92 4.6E 05 6 100.0 70.0 89.0% 72.0 9.7 14.0 70.0 14.2 9.9 121 19.67 4.5E 05 Average 4.6E 05 7 120.0 70.0 89.0% 72.0 0.0 4.9 70.0 24.0 19.1 121 22.31 4.5E 05 8 120.0 70.0 89.0% 72.0 4.9 9.4 70.0 19.1 14.6 120 21.00 4.4E 05 9 120.0 70.0 89.0% 72.0 9.4 13.6 70.0 14.6 10.3 120 19.78 4.4E 05 Average 4.5E 05 a PG specimen final water content (%), 24.5; length (cm), 7.16; and diam eter (cm), 7.16 b W ater height in burette

PAGE 87

87 Table A 1 1 Cations concentration in batch leaching solution of SWPG of with MSW Leachate (mg/L) Cation MSW landfill leachate Leaching test 1 Leaching test 2 Leaching test 3 Ag BDL BDL BDL BDL Al 0.2 0.19 0. 23 0.24 As 0.16 0.15 0.15 0.16 B 6.47 6.76 6.93 6.99 Ba 0.05 0.03 0.04 0.04 Be BDL BDL BDL BDL Ca 85 1061 1175 1217 Cd BDL BDL BDL BDL Co 0.03 0.03 0.03 0.03 Cr 0.08 0.08 0.08 0.08 Cu 0.02 0.05 BDL 0.02 Fe 5.96 2.57 3.50 3.66 K 847 903 903 933 Mg 36.43 37.2 37.11 38.13 Mn 0.14 0.12 0.12 0.13 Mo BDL 0.02 BDL 0.03 Na 1558 1639 1638 1700 Ni 0.11 0.10 0.10 0.12 Pb BDL BDL BDL BDL Sb 0.11 BDL BDL BDL Se BDL BDL BDL BDL Sn BDL 0.05 BDL 0.06 Sr 0.27 2.95 3.19 3.32 V 0.05 0.06 0.05 0.05 Zn 0. 05 0.03 0.03 0.04 *BDL = below detection limit

PAGE 88

88 Table A 1 2 Cations concentration in batch leaching solution of WWPG of with MSW Leachate (mg/L) Cation MSW landfill leachate Leaching test 1 Leaching test 2 Leaching test 3 Ag BDL BDL BDL BDL Al 0.2 0. 19 BDL 0.14 As 0.16 0.14 0.13 0.15 B 6.47 6.79 6.27 6.3 Ba 0.05 0.04 0.06 0.03 Be BDL BDL BDL BDL Ca 85 1169 1034 903 Cd BDL BDL BDL BDL Co 0.03 0.03 0.02 0.02 Cr 0.08 0.07 0.06 0.07 Cu 0.02 BDL BDL BDL Fe 5.96 2.62 2.41 2.75 K 847 889 819 816 Mg 36.43 36.9 34.34 34.36 Mn 0.14 0.1 0.09 0.1 Mo BDL BDL BDL BDL Na 1558 1620 1485 1480 Ni 0.11 0.1 0.17 0.12 Pb BDL BDL BDL BDL Sb 0.11 BDL BDL BDL Se BDL BDL BDL BDL Sn BDL BDL BDL BDL Sr 0.27 3.22 2.87 2.56 V 0.05 0.05 0.05 0.05 Zn 0.05 0.04 0.16 0.13 B elow detection limit

PAGE 89

89 Table A 1 3 Cations concentration in batch leaching solution of NWPG of with MSW Leachate (mg/L) Cation MSW landfill leachate Leaching test 1 Leaching test 2 Leaching test 3 Ag BDL BDL BDL BDL Al 0.2 BDL BDL BDL As 0.16 0.14 0.16 0.15 B 6.47 6.59 6.97 6.43 Ba 0.05 0.05 0.04 0.04 Be BDL BDL BDL BDL Ca 85 1051 1170 1080 Cd BDL BDL BDL BDL Co 0.03 0.03 0.03 0.03 Cr 0.08 0.08 0.08 0.07 Cu 0.02 BDL BDL BDL Fe 5.96 2.60 3.53 2.99 K 847 858 928 853 Mg 36.43 36.09 38.76 35.86 Mn 0.14 0.12 0.13 0.17 Mo BDL 0.07 0.08 0.09 Na 1558 1574 1711 1558 Ni 0.11 0.11 0.12 0.13 Pb BDL BDL BDL BDL Sb 0.11 BDL 0.04 0.04 Se BDL BDL 0.03 BDL Sn BDL BDL BDL 0.04 Sr 0.27 3.16 3.48 3.2 V 0.05 0.05 0.05 0.04 Zn 0.05 0.03 0. 02 0.03 B elow detection limit

PAGE 90

90 Table A 1 4 Cations concentration in batch leaching solution of EWPG of with MSW Leachate (mg/L) Cation MSW landfill leachate Leaching test 1 Leaching test 2 Leaching test 3 Ag BDL BDL BDL BDL Al 0.2 0.18 0.13 BDL As 0.16 0.16 0.14 0.14 B 6.47 7.00 6.34 6.37 Ba 0.05 0.06 0.05 0.03 Be BDL BDL BDL BDL Ca 85 1119 1154 1157 Cd BDL BDL BDL BDL Co 0.03 0.03 0.03 0.03 Cr 0.08 0.08 0.07 0.07 Cu 0.02 BDL BDL BDL Fe 5.96 2.96 2.74 2.51 K 847 917 869 855 Mg 36.43 37.72 36.06 35.57 Mn 0.14 0.11 0.1 0.1 Mo BDL BDL 0.02 0.03 Na 1558 1670 1577 1550 Ni 0.11 0.11 0.10 0.09 Pb BDL BDL BDL BDL Sb 0.11 BDL BDL BDL Se BDL BDL BDL BDL Sn BDL BDL BDL 0.03 Sr 0.27 3.32 3.38 3.38 V 0.05 0.05 0.04 0.04 Zn 0.05 0.03 0.03 BDL B elow detection limit

PAGE 91

91 Table A 1 5 Cations concentration in batch leaching solution of GCL bentonite with DI water (mg/L) Cation Test 1 Test 2 Ag BDL BDL Al 245.37 234.67 As BDL BDL B 0.79 0.77 Ba 0.16 0.16 Be 0.01 0.01 Ca 21.23 21.65 Cd BDL BDL Co 0.01 BDL Cr BDL BDL Cu 0.12 0.31 Fe 48.4 46.66 K 9.23 4.92 Mg 53.49 50.86 Mn 0.05 0.05 Mo 0.09 0.10 Na 159.51 145.20 Ni 0.04 0.06 Pb 0.06 0.06 Sb BDL BDL Se BDL BDL Sn 0.07 0.07 Sr 0.51 0.47 V BDL BDL Zn 0.14 0.30 B elow detection limit

PAGE 92

92 Table A 1 6 Cations concentration in batch leaching solution of GCL bentonite with MSW landfill leachate (mg/L) Cation Test 1 Test 2 Ag BDL BDL Al 1.05 1.10 As BDL BDL B 5.40 5.32 Ba 0.17 0.18 Be BDL BDL Ca 134.82 124.35 Cd BDL BDL Co 0. 04 0.04 Cr 0.22 0.22 Cu 0.16 0.13 Fe 2.06 2.01 K 537.45 496.31 Mg 61.84 62.46 Mn 0.08 0.07 Mo 0.04 0.04 Na 1828.65 1823.42 Ni 0.26 0.41 Pb 0.07 0.08 Sb BDL 0.03 Se BDL BDL Sn BDL BDL Sr 3.3 3.45 V 0.05 0.04 Zn 0.24 0.19 *B elow detection li mit

PAGE 93

93 Table A 1 7 Cations concentration in batch leaching solution of GCL bentonite with simulated SWPG leachate (mg/L) Cation Test 1 Test 2 Test 3 Ag BDL BDL BDL Al 2.88 1.23 0.86 As BDL BDL BDL B 0.3 0.48 0.36 Ba 0.05 0.05 0.04 Be BDL BDL BDL Ca 235.92 187.32 271.81 Cd BDL BDL BDL Co BDL BDL BDL Cr BDL BDL BDL Cu 0.08 0.07 0.07 Fe 1.1 BDL BDL K 19.06 19.03 18.39 Mg 21.83 19.03 22.12 Mn BDL BDL BDL Mo 0.03 0.04 0.03 Na 415.36 434.91 394.98 Ni 0.01 0.02 BDL Pb BDL BDL BDL Sb BDL BDL BDL Se BDL BDL BDL Sn 0.04 0.03 BDL Sr 2.26 1.95 2.42 V BDL BDL BDL Zn 0.09 0.06 0.08 B elow detection limit

PAGE 94

94 Table A 1 8 Cations concentration in batch leaching solution of GCL bentonite with simulated WWPG leachate (mg/L) Cation Test 1 Test 2 Test 3 Ag BDL BDL BDL Al 0.92 0.8 0.62 As BDL BDL BDL B 0.41 0.37 0.27 Ba 0.05 0.05 0.05 Be BDL BDL BDL Ca 193.38 214.44 302.83 Cd BDL BDL BDL Co BDL BDL BDL Cr BDL BDL BDL Cu 0.06 0.07 0.08 Fe BDL BDL BDL K 18.32 18.4 16.45 Mg 19.18 20.1 22.1 Mn BDL BDL BDL Mo 0.03 0.03 0.03 Na 437.23 442.74 380.49 Ni BDL BDL BDL Pb BDL BDL BDL Sb BDL BDL BDL Se BDL BDL BDL Sn BDL BDL BDL Sr 2.05 2.17 2.6 V BDL BDL BDL Zn 0.06 0.06 0.09 B elow detection limit

PAGE 95

95 Table A 19 Cations concentration in bat ch leaching solution of GCL bentonite with simulated NWPG leachate (mg/L) Cation Test 1 Test 2 Test 3 Ag BDL BDL BDL Al 0.6 0.97 1.7 As BDL BDL BDL B 0.3 0.36 0.66 Ba 0.04 0.05 0.07 Be BDL BDL BDL Ca 204.3 189.95 189.23 Cd BDL BDL BDL Co BDL BDL BDL Cr BDL BDL BDL Cu 0.08 0.09 0.07 Fe BDL BDL BDL K 18.07 21.36 18.23 Mg 19.77 19.28 19.42 Mn BDL BDL BDL Mo 0.04 0.03 0.03 Na 433.47 512.24 438.08 Ni 0.02 BDL BDL Pb 0.02 BDL BDL Sb BDL BDL BDL Se 0.02 BDL BDL Sn BDL BDL BDL Sr 2.14 2.07 2 .09 V BDL BDL BDL Zn 0.08 0.07 0.09 B elow detection limit

PAGE 96

96 Table A 2 0 Cations concentration in batch leaching solution of GCL bentonite with simulated EWPG leachate (mg/L) Cation Test 1 Test 2 Test 3 Ag BDL 0.34 BDL Al 0.99 1.55 0.76 As BDL BDL BDL B 0.43 0.53 0.32 Ba 0.05 0.05 0.04 Be BDL BDL BDL Ca 166.36 181.25 182.02 Cd BDL BDL BDL Co BDL BDL BDL Cr BDL BDL 0.01 Cu 0.09 0.08 0.07 Fe BDL BDL BDL K 17.82 18.21 18.9 Mg 17.21 18.55 18.16 Mn BDL BDL BDL Mo 0.04 0.03 0.08 Na 440.5 451 .83 479.29 Ni 0.02 BDL BDL Pb BDL 0.02 BDL Sb BDL BDL 0.04 Se BDL BDL BDL Sn BDL BDL 0.06 Sr 1.82 1.93 1.92 V BDL BDL BDL Zn 0.08 0.07 0.06 B elow detection limit

PAGE 97

97 Table A 2 1 GCL hydraulic conductivity test results with DI water Test Chamber r eadings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1a 80.0 70.0 72.0 13.4 18.3 70.0 17.8 13.5 76500 162.19 4.5E 09 80.0 70.0 72.0 18.3 19.8 70.0 13.5 12.2 28440 155.26 3.8E 09 80.0 70.0 72.0 10.0 13.4 70.0 20.0 17.1 57600 170.33 3.9E 09 Average 4.0E 09 2b 80.0 70.0 72.0 10.0 1 1.1 70.0 20.0 19.2 61200 188.33 2.1E 09 80.0 70.0 72.0 11.1 12.9 70.0 19.2 17.8 93120 185.12 2.4E 09 Average 2.3E 09 3c 80.0 70.0 72.0 0.0 3.2 70.0 24.0 20.7 84360 175.89 2.5E 09 80.0 70.0 72.0 3.2 7.2 70.0 20.7 16.7 109560 167.99 2.5E 09 80.0 70.0 72.0 7.2 10.5 70.0 16.7 13.4 69900 160.03 3.3E 09 Average 2.8E 09 a Duplicate test 1, specimen final water content (%), 105.1; thickness (cm), 0.87; diameter (cm), 10.30 b Duplicate test 2, specimen final water content (%), 111.2; thickness (cm), 0.80; diameter (cm), 7.04 c Duplicate test 3, specimen final water content (%), 127.0; thickness (cm), 0.92; diameter (cm), 10.60

PAGE 98

98 Table A 2 2 GCL hydraulic conductivity test results with MSW landfill leachate Test Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final ( cm) 1a 80.0 70.0 72.0 10.0 13.2 70.0 20.0 16.8 1200 175.94 1.8E 07 80.0 70.0 72.0 13.2 16.5 70.0 16.8 13.5 1200 168.19 1.9E 07 80.0 70.0 72.0 16.5 19.8 70.0 13.5 10.8 1290 160.67 1.7E 07 Average 1.8E 07 2b 80.0 70.0 72.0 0.0 7 .1 70.0 24.0 16.8 61 219.15 6.3E 06 80.0 70.0 72.0 7.1 14.0 70.0 16.8 9.9 63 199.60 6.4E 06 80.0 70.0 72.0 14.0 20.4 70.0 9.9 3.5 61 181.10 6.8E 06 Average 6.5E 06 3c 80.0 70.0 72.0 5.0 10.9 70.0 20.0 14.1 60 180.88 6.2E 06 80.0 70.0 72.0 10.9 16.6 70.0 14.1 8.4 60 166.87 6.5E 06 80.0 70.0 72.0 16.6 21.9 70.0 8.4 3.2 60 153.65 6.5E 06 Average 6.4E 06 a Duplicate test 1, specimen final water content (%), 95.0; thickness (cm), 0.84; diameter (cm), 10.35 b Du plicate test 2, specimen final water content (%), 105.1; thickness (cm), 0.72; diameter (cm), 10.42 c Duplicate test 3, specimen final water content (%), 83.1; thickness (cm), 0.83; diameter (cm), 10.54

PAGE 99

99 Table A 2 3 GCL hydraulic conductivity test result s with simulated SWPG leachate Test Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure ( psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1a 80.0 70.0 72.0 0.0 3.0 70.0 24.0 20.9 1260 170.60 1.7E 07 80.0 70.0 72.0 3.0 6.1 70.0 20.9 17.8 1260 164.11 1.8E 07 Average 1.7E 07 2b 80.0 70.0 72.0 11.0 12.7 70.0 19.0 17.3 1242 161.18 2.1E 07 80.0 70.0 72.0 12.7 14.4 70.0 17.3 15.6 1202 157.46 2.2E 07 Average 2.1E 07 3c 80.0 70.0 72.0 5.0 10.8 70.0 20.0 14.2 600 170.87 6.6E 07 80.0 70.0 72.0 10.8 15.0 70.0 14.2 10.0 600 159.47 5.2E 07 80.0 70.0 72.0 15. 0 18.1 70.0 10.0 6.9 605 151.15 4.0E 07 Average 5.3E 07 a Duplicate test 1, specimen final water content (%), 118.5; thickness (cm), 0.95; diameter (cm), 10.42 b Duplicate test 2, specimen final water content (%), 122.8; thickness (cm ), 0.91; diameter (cm), 7.24 c Duplicate test 3, specimen final water content (%), 104.4; thickness (cm), 0.88; diameter (cm), 10.42

PAGE 100

100 Table A 2 4 GCL hydraulic conductivity test results with simulated WWPG leachate Test Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1a 80.0 70.0 72.0 10.0 20.4 70.0 20.0 10.4 600 179.82 1.1E 06 80.0 70.0 72.0 10.0 21.0 70.0 20.0 9.0 603 178.54 1.2E 06 80.0 70.0 72.0 10.0 21.6 70.0 20.0 8.4 602 177.77 1.3E 06 Average 1.2E 06 2b 80.0 70.0 72.0 10.0 11.5 70.0 20.0 18.5 601 173.25 3. 5E 07 80.0 70.0 72.0 11.5 13.5 70.0 18.5 16.4 602 169.13 4.9E 07 80.0 70.0 72.0 13.5 15.8 70.0 16.4 14.1 602 164.07 5.7E 07 Average 4.7E 07 3c 80.0 70.0 72.0 10.0 11.1 70.0 20.0 18.9 1800 188.34 3.8E 08 80.0 70.0 72.0 11.1 12.1 70.0 18.9 17.9 1830 185.70 3.5E 08 80.0 70.0 72.0 10.0 10.7 70.0 20.0 19.2 1808 188.78 2.6E 08 Average 3.3E 08 a Duplicate test 1, specimen final water content (%), 115.0 thickness (cm), 0.78; diameter (cm), 10.42 b Duplicate test 2, specimen final water content (%), 108.4; thickness (cm), 0.86; diameter (cm), 7.24 c Duplicate test 3, specimen final water content (%), 104.4; thickness (cm), 0.88; diameter (cm), 10.42

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101 Table A 2 5 GCL hydraulic conductivity test results with simulat ed NWPG leachate Test Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1a 80.0 70.0 72.0 5.0 6.6 70.0 20.0 18.4 9600 153.57 1.2E 08 80.0 70.0 72.0 6.6 9.7 70.0 18.4 15.4 29640 148.94 7.8E 09 Average 1.0E 08 2b 80.0 70.0 72.0 5.0 5.9 70.0 20.0 19.3 39600 166.14 3.0E 09 80.0 70.0 72.0 5.9 6.9 70.0 19.3 18.1 65760 164.11 2.6E 09 Average 2.8E 09 3c 80.0 70.0 72.0 5.0 8.5 70.0 20.0 16.7 66780 165.61 3.5E 09 80.0 70.0 72.0 8.5 12.8 70.0 16.7 12.6 85260 157.35 3.6E 09 Average 3.6E 09 a Duplicate test 1, specimen final water content (%), 93.6 thickness (cm), 1.03; diameter (cm), 10.63 b Duplicate test 2, specimen final water content (%), 98.8; thickness (cm), 0.93; diameter (cm), 7.13 c Duplicate test 3, specimen final water content (%), 98.7; thickness (cm), 0.92; diameter (cm), 10.54

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102 Table A 2 6 GCL hydraulic conductivity test results with simulated EWPG leachate Test Chamber readings Inflow burette Outflow burette Test time (sec) Gradient Hydraulic conductivity, K, (cm/sec.) Cell pressure (psi) Back pressure (psi) Pressure (psi) Ht. H2O initial (cm)b Ht. H2O final (cm) Pressure (psi) Ht. H2O initial (cm) Ht. H2O final (cm) 1a 80.0 70.0 72.0 5.0 8.3 70.0 20.0 16.7 180 173.38 1.2E 06 80.0 70.0 72.0 8.3 11.6 70.0 16.7 13.4 180 165.87 1.3E 06 80.0 70.0 72.0 11.6 14.9 70.0 13.4 10.1 180 158.36 1.3E 06 Average 1.3E 06 2b 80.0 70.0 72.0 5.0 8.4 70.0 20.0 16.6 182 194.44 1.1E 06 80.0 70.0 72.0 8.4 12.7 70.0 16.6 12.3 189 184.61 1.4E 06 80.0 70.0 72. 0 12.7 17.4 70.0 12.3 7.5 182 173.05 1.7E 06 Average 1.4E 06 3c 80.0 70.0 72.0 10.0 13.2 70.0 20.0 16.8 1200 175.94 1.8E 07 80.0 70.0 72.0 13.2 16.5 70.0 16.8 13.5 1200 168.19 2.0E 07 80.0 70.0 72.0 16.5 19.8 70.0 13.5 10.8 1290 1 60.67 1.7E 07 Average 1.8E 07 a Duplicate test 1, specimen final water content (%), 102.5 thickness (cm), 0.88; diameter (cm), 10.61 b Duplicate test 2, specimen final water content (%), 106.4; thickness (cm), 0.78; diameter (cm), 10. 57 c Duplicate test 3, specimen final water content (%), 114.1; thickness (cm), 0.84; diameter (cm), 10.33

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103 APPENDIX B SUPPLEMENTARY FIGURES Figure B 1. PG stack and sample location, Mosaics Batow Facility South PG stack l ocated in Mulberry, Florida. ( Provided by Mosaic Fertilizer, LLC. )

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104 Figure B 2 PG samples were stored for research purposes in solid and hazard waste management laboratory

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105 Compacted PG 12.7 cm 10.2 cm 30.5 cm constant head above PG Influent Effluent Liquid Figure B 3 Schematic diagram of PG column test

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106 Figure B 4 Compac ted PG and GCL hydraulic conductivity test devices

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107 Figure B 5 Largescale direct shear test device

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108 LIST OF REFERENCES ASTM ( American Society of Testing and Material s), 2004. Standard test method for direct shear test of soils under consolidated d rained conditions. West Conshohocken, Pennsylvania. ASTM (American Society of Testing and Materials), 2004. Standard test methods for laboratory compaction characteristics of soil using standard effort West Conshohocken, Pennsylvania. ASTM (American Socie ty of Testing and Materials), 2004. Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter West Conshohocken, Pennsylvania. ASTM (American Society of Testing and Materials), 2004. S tandard test method for evaluation of hydraulic properties of geosynthetic clay liners permeated with potentially incompatible liquids West Conshohocken, Pennsylvania. ASTM (American Society of Testing and Materials), 2004. Standard test method for measurement of hydraulic conductivity of porous material using a rigidwall, compaction mold permeameter West Conshohocken, Pennsylvania. Ardaman & Associates, Inc., 2007. Gypsum consolidation and drainage volume estimates for the unlined and lined phosphogypsum stacks Mosaic Fertilizer, LLC Green Bay Facility Polk County, Florida. Provided by Mosaic Fertilizer, LLC. Benson, C.H. John. M.T., 1994. Hydraulic conductivity of thirteen compacted clays, Clays and Clay Minerals 43 (6) 669681. Benson, C.H., Meer, S.R., 2009. Relative abundance of monovalent and divalent cations and the impact of desiccation on geosynthetic clay liners. Geotechnical & Geoenvironmental Engineering, 135 (3), 349358. Chapuis, C., Masse, I., Aubertin, M., 2006. A drainage column test f or determining unsaturated properties of coarse materials. Geotechnical Testing Journal, 30 (2) 17 Cho Y. M., Ko, J. H., Chi. L., Townsend, T.G., 2011. Food waste impact on municipal solid waste angle of internal friction. Waste Management, 31(1), 2632. Degirmenci, N., Okucu, A., Turabi, A., 2006. Application of phosphogypsum in soil stabilization. Building and Environment, 42(9) 33933398. FDEP (Florida Department of Environmental Protection), 2010. Solid waste management facilities: chapter 62701 soli d waste management facilities table of contents. http://www.dep.state.fl.us/waste/quick_topics/rules/documents/62701.pdf

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109 FDOT (Florida Department of Transportation), 2008. Summary of Phosphogypsum Laboratory Test Results. Provided by Mosaic Fertilizer, LLC. FIPR (Florida Institute of Phosphate Research), 1983. Use of Florida phosphogypsum in synthetic construction aggregate. http://fipr1.state.fl.us/fipr/fipr1.nsf/a1380a2dc3df745f85256b4b006398eb/5487682 14d42a80a85256b25006cf204/$FILE/01008026Final.pdf FIPR (Florida Ins titute of Phosphate Research), 1989. Phosphogypsum for secondary road construction. http://www1.fipr.state.fl.us/fipr/fipr1.nsf/129fc2ac92d337ca85256c5b00481502/3e4 ac1d74250acc085256b2e005b1632/$FILE/01033077Final.pdf FIPR (Florida Institute of Phosphate Research), 1990. Proceedings of the third international symposium on phosphogypsum. http://www1.fipr.state.fl.us/FIPR/FIPR1.nsf/.../01 060083v1Final.pdf FIPR (Florida Institute of Phosphate Research), 1993. Environmental monitoring of Polk and Columbia counties experimental phosphogypsum roads Bartow (FL). http://fipr1.state.fl.us/fipr/fipr1.nsf/9bb2fe8f45c4945e85256b58005abaec/d6a0b295 84170e7685256b2f005bfeff/$FILE/05033101Final.pdf Gabr, M.A., Hossain, M.S., Barlaz, M.A., 2007. Shear strength parameters of municipal solid waste with leachate recirculation, Geotechnical and Geoenvironmental Engineering, 133(4), 478484. Harris, J. M., Shafer, A. L., DeGroff, W., Hater G. R., Gabr M., and Barlaz, M. A., 2006. Shear strength of degraded reconstituted municipal solid waste, Geotechnical Testing 29 (2), 1 8. Holtz, R.D., Kovacs W.D.,1981. An Introduction to Geotechnical Engineering, Prentice Hall, Englewood Cliffs, NJ. Jo, H.Y., Katsumi,T., Benson,C.H., Edil, T.B., 2001. Hydraulic conductivity and swelling of nonprehydrated GCL s permeated with single species salt solutions Geotechnical And Geoenvironmental Engineering, 127 (7), 557567. Kavazanjian, E. 2008. The impact of degradation on MSW shear strength. Proceedings of GeoCongress 2008, Geotechnics of Waste Management and Remediation, ASCE, New Orleans, Louisiana, 224231. Kavazanjian, E. JR., Matasovic, N. Bachus, R.C. 1999. Largediameter static and cyclic laboratory testing of municipal solid waste. Proceedings of Sardinia 99, 7th Int. Waste Management and Landfill Symposium, CISA Environ. Sanitary Engineering, Cagliari, Italy, 437 445. http://www.infomine.com/publications/docs/Kavazanjian1999b.pdf

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110 Kavazanjian, E., Matasovic, N., Bonaparte, R., Schmertmann, G. 1995. Evaluation of MS W properties for seismic analysis. Proceedings of Specialty Conference, Geoenvironmental 2000, ASCE Geotechnical Special Publication No. 46(2), 11261141. Kolstad, D., Benson, C., Edil, T., 2004. Hydraulic conductivity and swell of nonprehydrated GCLs perm eated with multispecies inorganic solutions. J. Geotech. Geoenviron. Eng., 130(12), 12361249. Lee S., Xu Q., Booth M., Townsend T.G., Chadik P., Bitton G. 2006. Reduced sulfur compounds in gas from construction and demolition debris landfills. Waste Management, 26 (5), 526533. Machado, S.L., Carvalho, F.M., Vilar, O.M., 2002. Constitutive Model for municipal solid waste. Journal of Geotechnical and Geoenvironmental Engineering, 128 (11), 940951. Mahler, C.F., Netto, A.D.L., 2003. Shear resistance of mec hanical biological pretreated domestic urban waste. Proceedings of Sardinia 2003, 9th International Waste Management and Landfill Symposium, CISA Environ. Sanitary Engineering, Cagliari, Italy http://www.getres.ufrj.br/artigos/Mahler%20et%20Neto%20(2003b).pdf Moussa, D., Crispel, J.J., Legrand, C. Thenoz, B., 1984. Laboratory study of the structure and compactibility of T unisian phosphogypsum (SFAX) for use in embankment construction, Resources and Conservation, 11 (2) 95 116. Pelkey S.G., Valsangkar A.J., Landva A., 2001. Shear displacement dependent strength of municipal solid waste and its major constituent. Geotech Test J ASTM 24(4):381390 Petrov, R.J., Rowe, R.K., 1997. Geosynthetic clay liner (GCL) chemical compatibility by hydraulic conductivity testing and factors impacting its performance, Can. Geotech. J. 34, 863885. Petrov, R.J., Rowe, R.K., Quigley, R.M., 1997. Selected factors influencing GCL hydraulic conductivity, Journal of geotechnical and geoenvironmental engineering, 123 (8) 683 695. Reddy, K. R., Hettiarachchi, H., Parakalla, N. S., Gangathulasi, J., Bogner J. E. 2009. Geotechnical properties of fresh municipal solid waste at Orchard Hills landfill USA. Waste Management, 29, 952959. Ruhl, J.L., Daniel, D.E., 1997. Geosynthetic clay liners permeated with chemical solutions and leachates. Journal of Geotechnical and Geoenvironmental Engineering, ASCE 123 (4), 369 381.

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111 Shackelford C.D., Benson C.H., Katsumi T., Edil T.B., Lin L., 2000. Evaluating the hydraulic conductivity of GCLs permeated with nonstandard liquids. Geotextiles and Geomembranes, 18 (24), 133161. Shieh, C. S. 1999. Application of Phosphogypsum in Landfills http://www.fipr.state.fl.us/5b_Shieh_testimony.pdf Stark, T. D., Huvaj Sarihan, N., Li, G., 2009. Shear strength of municipal solid waste for stability analyses, Environmental Geology, 57(8), 19111923. The Wor ld Bank, 1999. Urban development sector unit and east asia and pacific region, what a waste: solid waste management in Asia. The International Bank for Reconstruction and Development, 424. http://web.mit.edu/urbanupgrading/urbanenvironment/resources/references/pdfs/W hatAWasteAsia.pdf TouzeFoltz, N., Duquennoi, C., Gaget, E., 2006. Hydraulic and mechanical behavior of GCLs in contact with leachat e as part of a composite liner. Geotextiles and Geomembranes, 24 (3), 188197. USEPA, 2007. Municipal solid was in the United States : 2007 Facts and Figures. http://www.epa.gov/ epawaste/nonhaz/municipal/pubs/msw07rpt.pdf USEPA, 2010. About p hosphogypsum. http://www.epa.gov/rpdweb00/neshaps/subpartr/about.html VanGulck, J.F., Rowe, K.R., Rittmann B. E., Coo ke A. J. 2003. Predicting biogeochemical calcium precipitation in landfill leachate collection systems Biodegradation, 14 (5), 331346. Vilar O.M., Carvalho M.F., 2004. Mechanical properties of municipal solid waste. Geotech Test J ASTM 32(6):1 12 Wang, H. Nie, Y. 2001. Municipal solid waste characteristics and management in China, Air & Waste Management Association, 51, 250263. Wang, X.D., Benson, C.H., 1999. Hydraulic conductivity testing of geosynthetic clay liners (GCLs) using the constant volume m ethod, Geotechnical Testing Journal, 22(4): 277283. Zekkos, D., Bray, J.D., Stokoe, K., Kavazanjian, E., Rathje, E., Athanasopoulos, G.A., Riemer, M., Matasovic, N., Lee, J.J., Seos, B., 2008. Recent findings on the static and dynamic properties of munici pal solid waste. http://www.infomine.com/publications/docs/Zekkos2008.pdf Zekkos, D., Bray, J. D., Athanasopoulos, G.A., Riemer, M.F., Kavazanjian, E. Jr., Founta, P.A., Grizi, A.F., 2007. Compositional and loading rate effects on the shear strength of municipal solid waste. http://waste.geoengineer.org/files/1525_zek.pdf

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112 Zhan, T.L.T., Chen, Y.M., Ling, W.A., 2008. Shear strength characterization of municipal solid waste at the Suzhou landfill, China, Engineering Geology, 97, 97111.

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113 BIOGRAPHICAL SKETCH Yongqiang Yang was born in 1979 in China to Guoan Yang and Junying Xia. He enrolled in the Heibei Normal University of Science and Technology, Qinhuangdao, China in September 2001, and graduated with a Bachelor of Science in Food S cience & Engineering in July 2005. He also enrolled in the University of Findlay, Ohio in fall of 2007 and graduated with a Master of Science i n Environmental, Health a nd Safety Management in spring of 2009. He received his Master of Science in Environmental Engineering Sciences from the University of Florida in spring of 2011.