Bioreactor Landfills Promoted By Leachate Recirculation:A Full-Scale Study

Samuel T.S. Yuen B.E., M.Eng.Sc.

Thesis submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy

Department of Civil & Environmental EngineeringUniversity of Melbourne

March 1999

Dedicated to Zona,

a wife of boundless patience

and

a mother of immense love

ii

Abstract________________________________________________

_

The concept of bioreactor landfills has certainly gained a lot of attention in the past decade.

Its advantages over the conventional “dry tomb” landfills are well demonstrated by many

laboratory tests and pilot-scale studies. However, there is still further full-scale research work

required before we can truly translate this concept into everyday practical operations. Aiming

to bridge this gap, an experiment has been conducted in the Lyndhurst Landfill, Victoria,

Australia. This thesis covers:

(i) The experimental implementation of a full-scale bioreactor landfill cell (stimulated by

leachate recirculation) to quantify the stabilisation of waste in terms of leachate quality,

gas composition and production, waste temperature, and landfill settlement.

(ii) The evaluation of leachate recirculation system performance and moisture flow

mechanism in municipal solid waste.

(iii) The study of water balance in the full-scale experimental cell to identify the significance

of various water components for the purpose of leachate management.

(iv) The development of an in-situ technique for measurement of moisture in municipal solid

waste for the hydrological investigations in (ii) and (iii) above.

As pointed out in a literature review, the research committed to hydrological aspects of

bioreactor landfills has been very limited compared to the work that has been done in

biodegradation enhancement. The hydrological component of this thesis helps to address this

shortcoming.

The thesis demonstrates that there is no ideal method available for the in-situ moisture

measurement of landfills. Nevertheless, with certain limitations, the use of a neutron probe

combined with in-situ access tubes can offer acceptable indirect, non-destructive

iii

measurements. This technique has been successfully applied in this experiment to monitor

seasonal moisture change and moisture variation caused by leachate injection.

The water balance study has identified the significance of various water components in the

experimental cell. This information is important and useful in terms of leachate management

for both dry and wet landfills, especially for those located in a similar climate region.

The numeral modelling and field measurements of a leachate recirculation trial demonstrated

the limitation of the recirculation system, which failed to distribute leachate uniformly in the

waste mass. This finding is significant in terms of exposing the inadequacy of recirculation

devices and the urgent need for their improvement. Contradicting the suggestions by many

studies, this thesis demonstrates that the classical theory based on saturated/ unsaturated flow

through a homogeneous porous medium can at best be used to predict bulk leachate flow but

is not useful in predicting moisture patterns.

An enhanced biodegradation has been achieved in some parts of the experimental cell by

leachate recirculation. The biodegradation enhancement has not occurred in the entire waste

mass due to a poor leachate distribution caused by heterogeneity. This implies that the use of

limited sampling points in full-scale experiments is unlikely to be sufficient in delineating

the extremely heterogeneous nature of landfills. This explains to some extent the rather

confusing monitoring results that have been observed in this experiment and in other full-

scale studies.

The most important finding of this thesis is that a full-scale landfill is extremely

heterogeneous, a feature that tends to be misrepresented by small-scale experiments. It is for

this important reason that small-scale results in many cases could not be reproduced in full-

scale landfills. This vital point is clearly demonstrated by the thesis both in the hydrological

investigation and in the stabilisation indicator monitoring.

According to the findings of this thesis, undoubtedly the most urgent need is to improve the

current technique of leachate recirculation. Given the heterogeneous nature of landfills, it

would be practically difficult to achieve a uniform moisture distribution throughout the waste

mass. Nevertheless, this is the area that future research focus should be directed.

iv

Declaration_____________________________________________

_

To the best of my knowledge and belief, this thesis comprises only my original work and

contains no material previously written or published by another person except where due

reference is made in the text. None of the work presented in this thesis, in whole or in part, has

been accepted for the award of a degree or diploma at any other university or institution. The

length of this thesis is less than 100,000 words excluding tables, figures, references and

appendices.

Samuel T.S. Yuen

v

Acknowledgement_______________________________________

_

First I have to express my sincere gratitude to my three very talented academic supervisors,

Mr. John Styles, Prof. Tom McMahon and Dr. Q.J. Wang, for the enthusiasm they shared

with me in this research project. Without their timely stimulus, encouragement and support

throughout the prolonged study period, the completion of this thesis would still be a dream.

The privilege of enjoying their fellowship while I was also working as their colleague is also

much appreciated.

A substantial portion of the funding of this project was provided by SITA-BFI (formerly

known as Browning-Ferris Industries, Australia). Their commitment in providing the funding

and test site, their belief in research to achieve a better waste management concept, and their

credit in allowing fully independent research of the project is gratefully acknowledged.

Energy Development Limited, the contractor responsible for the collection and utilisation of

the gas at the Lyndhurst Landfill, provided most of the labour and plant in constructing the

leachate recirculation system and gas collection system in the experimental cell. They also

provided the required equipment and technical staff for the monthly landfill gas monitoring. I

am grateful to their important contribution.

Many people have offered their expert advice and critical assistance to allow the

development of this resource demanding full-scale experiment. It would be difficult for me

to remember and to thank every individual but I try to list and acknowledge all of them

below:

Messrs. Max Spedding, Daniel Fyfe, Mark D’Amore, John Ellul, Adam Martin and Miss

Justine Maher of SITA-BFI for their interest in this research project and for their patience

in coping with the inconvenience caused to their everyday operations at the Lyndhurst

Landfill.

vi

Messrs. Allen Hollier, Shane Cribbes and all the staff of EnvirEng for their work at the

front face of the construction and maintenance of the full-scale experimental cell.

Mr. Keith Knox of Keith Knox Associates Environmental Consultants, U.K., for his

expert discussion related to the leachate, gas and settlement monitoring data.

Messrs. Tony Lowe, Geoff Duke and all other technical staff members in my Department

for their advice in keeping the instrumentation working in the laboratory and in the field.

Dr. Andrew Western, Dr. Francis Chiew, Mr. Mark Wood and all other fellow staff

members and postgraduates in my Department who offered stimulating discussion and

provided information on relevant references.

Miss Fiona Thiele and Miss Kynwynn Jones who assisted in the laboratory and in the

field while they were working on their undergraduate work training/ research project.

Last but not least, I am indebted to my parents for their encouragement and for daring me to

take on the challenge of this Ph.D. study which had been in my mind for the past decade.

vii

Table of

Contents________________________________________

Page

1. Introduction

1.1 Landfill Development and Significance 1-1

1.2 Objectives and Scope of Study 1-3

1.3 Time Constraint 1-4

1.4 Thesis Layout 1-4

2. Literature Review

2.1 Landfill Degradation and Behaviour 2.22.1.1 Decomposition of Municipal Solid Waste 2-22.1.2 Evolution Sequence 2-62.1.3 Influence Factors 2-7

2.2 Process-Based Landfill Enhancement Techniques 2-142.2.1 Control/ Selection of Waste 2-142.2.2 Shredding of Waste 2-152.2.3 Waste Compaction 2-152.2.4 Buffer Addition 2-162.2.5 Sewage Sludge Addition 2-162.2.6 Pre-composting Part of Landfill Waste 2-162.2.7 Enzymes Addition 2-172.2.8 Leachate Recirculation 2-18

2.3 Developments in Leachate Recirculation 2-192.3.1 Small-Scale Studies 2-192.3.2 Full-Scale Studies 2-292.3.3 Summary of Developments in Leachate Recirculation 2-40

2.4 Landfill Hydrology 2-442.4.1 Performance of Leachate Recirculation System 2-442.4.2 Water Balance of Landfill Cells2-452.4.3 Hydraulic Properties of Municipal Solid Waste 2-462.4.4 Saturated/ Unsaturated Flow in Municipal Solid Waste Medium2-47

2.5 Research Needs 2-47

viii

3. Approach and Methodology

3.1 Bioreactor Landfill Stabilisation 3-2

3.2 In-situ Moisture Monitoring of Municipal Solid Waste 3-3

3.3 Water Balance of Experimental Cell 3-4

3.4 Performance of Recirculation System and Moisture Flow Mechanism 3-5

4. Experimental Set-up

4.1 Experimental Cell Design and Construction 4-24.1.1 General 4-24.1.2 Size of Experimental Cell 4-44.1.3 Waste Composition 4-64.1.4 Waste Moisture Content 4-84.1.5 Daily/ Interim Covers 4-114.1.6 Density and Porosity of Waste 4-124.1.7 Cell Containment System 4-134.1.8 Leachate Collection system 4-144.1.9 Gas Extraction System 4-154.1.10 Leachate Recirculation System 4-17

4.2 Instrumentation and Monitoring Program 4-204.2.1 In-situ Municipal Solid Waste Moisture Monitoring 4-214.2.2 Climatic Data 4-234.2.3 Surface Runoff 4-234.2.4 Landfill Settlement 4-254.2.5 In-situ Waste Temperature 4-254.2.6 Saturated Leachate Level/ Leachate Sampling 4-274.2.7 Volume of Leachate Collected and Recirculated 4-284.2.8 Landfill Gas Composition and Flow Rate 4-294.2.9 Groundwater Quality4-294.2.10 Monitoring Program 4-30

4.3 Leachate Recirculation Strategy 4-32

5. In-situ Moisture Monitoring of Municipal Solid Waste

5.1 Previous Work 5-2

5.2 Feasibility Assessment 5-45.2.1 Electromagnetic Technique 5-55.2.2 Electrical or Thermal Conductivity 5-55.2.3 Tensiometric Technique 5-6

ix

5.2.4 Neutron Scattering 5-75.2.5 Outcome of Feasibility Assessment 5-11

5.3 Laboratory Investigation 5-115.3.1 Quantity Potential Limitations of Neutron Scattering5-115.3.2 Test Set-up 5-135.3.3 Results and Discussions 5-14

5.4 Field Trial 5-185.4.1 Set-up and Installation 5-185.4.2 Results and Discussions 5-19

5.5 Conclusions 5-24

6. Water Balance of Experimental Cell

6.1 As-Capped Moisture Content 6-2

6.2 Meteorological Records 6-2

6.3 Hydrological Data 6-56.3.1 Runoff Measurements 6-56.3.2 Evapotranspiration 6-66.3.3 Estimated Runoff, Lateral Drainage and Percolation 6-136.3.4 Volume of Leachate Recirculated 6-166.3.5 Basal Storage 6-176.3.6 Groundwater Ingress through Liner 6-21

6.4 Pre-capping Water Balance 6-22

6.5 Post-capping Water Balance 6-26

6.6 Conclusions 6-36

7. Moisture Flow in Municipal Solid Waste and Performance of Leachate Recirculation Systems

7.1 Previous Work 7-27.1.1 Modelling Moisture Transport in MSW as Saturated/ Unsaturated Flow

Through Homogeneous Porous Media 7-27.1.2 Modelling Leachate Recirculation System 7-77.1.3 Measurements of Moisture Movement in MSW Media 7-9

7.2 Study of Leachate Recirculation System in Experimental Cell 7-137.2.1 Numerical Simulation of Experimental Recirculation System 7-147.2.2 Field Measurements 7-22

x

7.3 Discussion and Conclusions 7-287.3.1 Moisture Flow Mechanism in MSW Media 7-287.3.2 Performance of Leachate Recirculation System 7-297.3.3 Conclusions 7-30

8. Bioreactor Landfill Behaviour Simulated By Leachate Recirculation

8.1 Leachate Composition 8-28.1.1 Sampling and Testing 8-28.1.2 Physical Indicators – pH, Alkalinity and Oxidation-Reduction Potential 8-38.1.3 Leachate Strength – Total Solids and Conductivity 8-78.1.4 Dilution Indicator – Chloride 8-98.1.5 Organics – BOD, COD, TOC and VFAs 8-108.1.6 Nitrogens – Organic Nitrogen, Ammonia, Nitrite and Nitrate 8-148.1.7 Sulphate/ Sulphide 8-178.1.8 Metals – Iron, Calcium, Magnesium, Sodium and Potassium 8-188.1.9 Trace Metals – Lead, Zinc, Manganese, Copper, Chromium, Arsenic, 8-20

Cadmium and Nickel8.1.10 Summary of Leachate Composition Analysis 8-23

8.2 Gas Quality and Quantity 8-268.2.1 Implications of Collection System on Gas Measurement 8-268.2.2 Results of Monitoring 8-278.2.3 Quantifying Well Leakages 8-328.2.4 Using Methane Flow as a Biodegradation Indicator 8-348.2.5 Summary of Landfill Gas Analysis 8-37

8.3 Landfill Settlement 8-398.3.1 Mechanisms and Stages of Landfill Settlement 8-398.3.2 Quantify the Effects of Settlement due to Biodegradation 8-418.3.3 Summary of Settlement Analysis 8-50

8.4 In-situ Waste Temperature 8-518.4.1 Temperature as a Biodegradation Activity Indicator 8-518.4.2 Monitoring Results 8-518.4.3 Summary of Temperature Analysis 8-55

8.5 Conclusions 8-57

9. Summary and Conclusions

9.1 Summary 9-29.1.1 In-situ MSW Moisture Measurement Technique 9-29.1.2 Water Balance Study

9-29.1.3 Moisture Flow Mechanism and Recirculation System Performance 9-39.1.4 Monitoring of Stabilisation Indicators 9-4

xi

9.2 Conclusions 9-69.2.1 Contributions from this Thesis 9-69.2.2 Shortcomings of this Thesis 9-89.2.3 The Way Ahead for Bioreactor Landfills 9-8

9.3 Recommendations for Future Work 9-109.3.1 The Lyndhurst Experimental Cell 9-109.3.2 Other Work 9-11

References R-1 to R-13

Appendix A: Plates A-1 to A-15

Appendix B: Daily Meteorological Measurement B-1 to B-11(January 1995 to December 1997)

Appendix C: Daily Runoff Measurements C1(November 1996 to December 1997)

Appendix D: Daily Potential Evapotranspiration Estimated by D-1 to D-7Penman-Monteith Method

Appendix E: HELP Model Output (Modelling of Final Cap) E-1 to E-21

Appendix F: Output of Jensen Model Estimating Actual F-1 to F-6Evapotranspiration

Appendix G: Leachate Composition Analysis Results G-1 to G-4

Appendix H: Landfill Gas Monitoring Data H1 to H3

Appendix I: Landfill Settlement Monitoring Data I-1

Appendix J: In-situ Waste Temperature Monitoring Data J-1

Appendix K: Groundwater Monitoring Data K-1 to K-10

xii

Appendix L: Volumetric Moisture Content Isoclines L-1 to L-32Predicted by Numerical Modelling

Appendix M: Publications Related to This Thesis M-1 to M-42

xiii

List of

Figures___________________________________________

Page

Figure 2.1 – Simplified Anaerobic Degradation Processes Involving Various Bacteria Groups in a Landfill Ecosystem

2-3

Figure 2.2 - Typical landfill Evolution Sequence in Terms of Gas and Leachate Composition (after Christensen & Kjeldsen, 1989; Farquhar & Rovers, 1973)

2-5

Figure 4.1 – Location Plan of Lyndhurst Sanitary Landfill 4-3

Figure 4.2 – As Constructed Survey Plan of Experimental cell 4-5

Figure 4.3 – Record of Waste Disposed According to Waste Streams 4-6

Figure 4.4 – Waste Composition Based on Waste Stream & WMC 1995 Data (By Wet Mass) 4-7

Figure 4.5 – Waste Composition Based on Test Cell Samples (By Dry Mass) 4-7

Figure 4.6 – Variation of Moisture Content with Depth in the Seven Sampling Holes: (a) By Dry Mass; (b) By Wet Mass; (c) By Volume

4-9

Figure 4.7 – Moisture Content Range and Distribution of MSW: (a) By Dry Mass; (b) By Wet Mass; (c) By Volume

4-10

Figure 4.8 – Record of Cover Material against Total Waste Volume 4-12

Figure 4.9 – Details of Final Capping 4-13

Figure 4.10 – Schematic Plan showing Leachate Collection System 4-14

Figure 4.11 – Schematic Plan Showing Gas Extraction Wells and Combined Leachate Injection/ Gas Extraction Wells

4-15

Figure 4.12 – Details of Gas Extraction Wells 4-16

Figure 4.13 – Details of Combined Gas Extraction/ Leachate Injection Well 4-16

Figure 4.14 – Integrated Leachate Recirculation System 4-18

Figure 4.15 – Details of Sub-Surface Infiltration Trench 4-19

Figure 4.16 – Location Plan Showing Instrumentation of Experimental Cell 4-21

Figure 4.17 – In-situ Access Tubes for Monitoring Moisture Changes 4-22

Figure 4.18 – Details of RBC Long Throated Flume Employed in Experimental Cell 4-24

Figure 4.19 – Flume Calibration Curve Relating Stage Height and Flow Rate 4-24

Figure 4.20 – Location Plan Showing Settlement Plates 4-26

Figure 4.21 – Details of Settlement Plate 4-26

xiv

Figure 4.22 – Location Plan Showing Temperature Probes 4-27

Figure 4.23 - Location Plan Showing Leachate Sumps and Open Wells 4-28

Figure 4.24 – Location of Groundwater Monitoring Bores 4-31

Figure 5.1 – Effect of Bound Hydrogen on Calibration Curve 5-9

Figure 5.2 – Effect of Neutron Capture on Calibration Curve 5-10

Figure 5.3 – Calibration Curves of Tests (a) to (e) 5-15

Figure 5.4 – Composition by Dry Mass of Samples Collected from AC2 5-20

Figure 5.5 – Neutron Count Ratio against Depth (AC2) 5-20

Figure 5.6 – Volumetric Moisture and Averaged Neutron Count Ratio against Depth (AC2) 5-21

Figure 5.7 – Neutron Count Ratio against Volumetric Moisture (AC2) 5-22

Figure 5.8 – Volumetric Moisture Profile of Access Tube AT4 5-24

Figure 6.1 (First Part) – Meteorological Records: (a) Monthly Rainfall; (b) Monthly Average Temperature

6-3

Figure 6.1 (Second Part) – Meteorological Records: (c) Monthly Average Relative Humidity; (d) Monthly Average Wind Speed; (e) Monthly Average Daily Global Radiation

6-4

Figure 6.2 – A Typical Runoff Hydrograph: Corresponding to Rainfall Event on 13 June 1997

6-5

Figure 6.3 – Comparison of Monthly Rainfall and Measured Monthly Runoff 6-6

Figure 6.4 – Potential Water Deficit of (a) 1995; (b) 1996; (c) 1997 6-7

Figure 6.5 – Comparison of Monthly Actual Evapotranspiration Obtained by HELP and Jensen Models

6-10

Figure 6.6 - Jensen Model to Determine Actual Evapotranspiration 6-12

Figure 6.6A – Volumetric Moisture Monitoring along Access Tubes AC1 and AC2 6-15

Figure 6.7 – Progress of Recirculation with Volumes Recorded from Various Sources 6-16

Figure 6.8 – Saturated Leachate Levels in Sumps and Observation Wells: (a) Control Section; (b) Test Section

6-18

Figure 6.9 – Water Balance of Open cell (Pre-Capping Phase) 6-22

Figure 6.10 - Saturated Leachate Levels against Cumulative Rainfall during Pre-Capping Period

6-25

Figure 6.11 – Water Balance of Capped Cell (Post-Capping Phase) 6-26

Figure 6.12 – Monthly Percolation (PECR); Leachate Injection (LR); Leachate Pumped from Sumps (PUMP): (a) Control Section and (b) Test Section

6-29

Figure 6.13 – Variation of Cell Storage (Scell) with Time 6-30

xv

Figure 6.14 -Approach to Determine Field Capacity in Control Section 6-32

Figure 7.1 – Finite Element Grid Representing Sub-surface Horizontal trench 7-18

Figure 7.2 – Finite Element Grid Representing Vertical Injection Well 7-18

Figure 7.3 – Volumetric Moisture Content Monitoring Related to Recirculation Trench RT7 7-23

Figure 7.4 – Volumetric Moisture Content Monitoring Related to Recirculation Well RW5 7-24

Figure 7.5 – Flow Rate Recorded by Flowmeter at Recirculation Trench RT7 7-25

Figure 7.6 – Flow Rate Recorded by Flowmeter at Recirculation Well RW5 7-25

Figure 7.7 – Cumulative Leachate Volume Recorded for Individual Devices 7-26

Figure 8.1 - Results of Leachate Analysis: pH 8-4

Figure 8.2 - Results of Leachate Analysis: Alkalinity (as CaCO3) 8-6

Figure 8.3 - Results of Leachate Analysis: Acetic Acid/ Alkalinity Ratio 8-6

Figure 8.4 - Results of Leachate Analysis: Redox Potential 8-6

Figure 8.5 - Results of Leachate Analysis: Total Solids 8-7

Figure 8.6 - Results of Leachate Analysis: Total Suspended Solids 8-8

Figure 8.7- Results of Leachate Analysis: Total Dissolved Solids 8-8

Figure 8.8 - Results of Leachate Analysis: Conductivity 8-8

Figure 8.9 - Results of Leachate Analysis: Chloride 8-9

Figure 8.10 - Results of Leachate Analysis: Biological Oxygen Demand 8-11

Figure 8.11 - Results of Leachate Analysis: Chemical Oxygen Demand 8-12

Figure 8.12 - Results of Leachate Analysis: Total Organic Carbon 8-12

Figure 8.13 - Results of Leachate Analysis: Total Volatile Acids 8-12

Figure 8.14 - Results of Leachate Analysis: Propionic Acid/ Acetic Acid Ratio 8-14

Figure 8.15 - Results of Leachate Analysis: BOD/COD Ratio 8-14

Figure 8.16 - Results of Leachate Analysis: Organic Nitrogen (N) 8-15

Figure 8.17 - Results of Leachate Analysis: Ammonia (N) 8-15

Figure 8.18 - Results of Leachate Analysis: Nitrite (N) 8-15

Figure 8.19 - Results of Leachate Analysis: Nitrate (N) 8-16

Figure 8.20 - Results of Leachate Analysis: Sulphate (S) 8-17

Figure 8.21- Results of Leachate Analysis: Sulphide (S) 8-18

Figure 8.22 - Results of Leachate Analysis: Iron 8-19

xvi

Figure 8.23 - Results of Leachate Analysis: Calcium 8-19

Figure 8.24 - Results of Leachate Analysis: Magnesium 8-19

Figure 8.25 - Results of Leachate Analysis: Sodium 8-20

Figure 8.26 - Results of Leachate Analysis: Potassium 8-20

Figure 8.27 - Results of Leachate Analysis: Lead 8-21

Figure 8.28 - Results of Leachate Analysis: Zinc 8-21

Figure 8.29 - Results of Leachate Analysis: Manganese 8-21

Figure 8.30 - Results of Leachate Analysis: Copper 8-22

Figure 8.31 - Results of Leachate Analysis: Arsenic 8-22

Figure 8.32 - Results of Leachate Analysis: Chromium 8-22

Figure 8.33 – Measured Gas Flow Rate at Individual Well Heads: Control Section 8-28

Figure 8.34 – Measured Gas Flow Rate at Individual Well Heads: Test Section 8-29

Figure 8.35 – Methane Concentration at Individual Well Heads: Control Section 8-30

Figure 8.36 – Methane Concentration at Individual Well Heads: Test Section 8-31

Figure 3.37 – Not Used -

Figure 8.38 – Not Used -

Figure 8.39 – Not Used -

Figure 8.40 – Average Methane Flow Rate Per Well 8-35

Figure 8.41 – Specific Methane Production Rate 8-36

Figure 8.42 – Schematic Cross-Section Showing Arrangement of Settlement Plates 8-43

Figure 8.43 (First Part) – Monthly Monitoring Results of Settlement Plates 8-44

Figure 8.43 (Second Part) – Monthly Monitoring Results of Settlement Plates 8-45

Figure 8.43A (First Part) – Change of Strain in Various Layers against Time 8-46

Figure 8.43A (Second Part) – Change of Strain in Various Layers against Time 8-47

Figure 8.44 – Secondary Compression Index (Ca) of Individual Layers at Different Settlement Plate Group Locations

8-49

Figure 8.45 – Monthly Monitoring Results of Temperature Probes 8-52

Figure 8.46 – Average Waste Temperature Measured by Probes 8-55

xvii

List of

Tables____________________________________________

Page

Table 2.1 - Summary of Influencing Factors on Landfill Degradation 2-9

Table 2.2 – Summary of Reported Laboratory & Lysimeter-Scale Studies on Leachate Recirculation and Related Enhancement techniques

2-20

Table 2.3 - Summary of Reported Full-Scale Studies on Leachate Recirculation and Supplementary Enhancement techniques

2-30

Table 4.1 - Progress of Experiment 4-4

Table 4.2 - Compositions of Waste from Metropolitan Melbourne (WMC, 1995) 4-7

Table 4.3 - Results of Waste Moisture Content Analysis 4-11

Table 4.4 - Calculation of in-situ waste density 4-13

Table 4.5 - Instrumentation/ Method Employed To Collect Data 4-20

Table 4.6 - Monitoring Schedule 4-30

Table 5.1 – Capture Cross-Section for Thermal Neutrons of Common Soil Elements 5-10

Table 5.2 –Results of Laboratory Tests (a) to (e) 5-15

Table 5.3 – Results of Calibration Curve 5-16

Table 6.1 – Parameters used in Penman-Monteith Combination Method (Smith, 1992) 6-8

Table 6.2 – Components of Final Cap 6-8

Table 6.3 – Soil Parameters Used in HELP Final Cap Model 6-9

Table 6.4 - Other Parameters Used in HELP Final Cap model 6-10

Table 6.5 – Parameters Used in the Jensen Model 6-13

Table 6.6 – HELP Model Monthly Estimates of Runoff, Lateral Drainage and Percolation 6-14

Table 6.7 – Volume of Leachate Injected through Recirculation System (LR) and Pumped Out from Sumps (PUMP)

6-17

Table 6.8 - Monthly Volume of Leachate in Basal Storage 6-20

Table 6.9 – Quantities of Water Balance Components for the Whole Pre-capping Period 6-24

Table 6.10 – Monthly Water Balance of Capped Cell 6-27

Table 6.11 – Monthly Results From Field Capacity Calculation 6-33

Table 6.12 - Field Capacity of MSW Reported in the Literature 6-34

xviii

Table 6.13 - Calculation of Moisture Content of Waste above Basal Zone in Test Section 6-36

Table 7.1– Unsaturated Flow Hydraulic Parameters 7-19

Table 7.2 – Predicted Leachate Feeding Capacity for Sub-surface Horizontal Trench 7-20

Table 7.3 – Graphs in Appendix L Corresponding to Various Material Types/ Pressures/ Time Steps

7-20

Table 8.1 – Leachate Testing Schedule 8-3

Table 8.2 – Gas Composition Measured by GC at Individual Well Heads on 18 February 1997

8-32

Table 8.3 – Results of Static Test Measured by GC at Main Headers on 16 May 1997 8-33

Table 8.4 - Data used in the calculation of Specific Methane Production Rate 8-35

Table 8.5 – Results of Secondary Compression Ratio (Cae) 5-48

Table 8.6 - Reported Secondary Compression Ratio, Cae (after Phillips et al., 1993) 8-49

Table 8.7 – Summary of Monitoring Results/ Comments 8-57

xix

List of

Plates_____________________________________________

Page

Plate 4.1 - Aerial Photograph Showing Lyndhurst Landfill and Experimental cell (Highlighted) A-1

Plate 4.2- General View of As-Constructed Experimental cell Taken from North-Western Corner A-2

Plate 4.3 - Well Head Manifold Station A-2

Plate 4.4 - Pump Installed at top of Leachate Collection Sump A-3

Plate 4.5 - Three Storage/ Header Tanks of Total 27,000 Litres Capacity on Top of Cell A-3

Plate 4.6 - System of Pipework and Valves Controlling Flow into Wells and Trenches A-4

Plate 4.7 - Automatic Wether Station Installed on top of Experimental Cell A-4

Plate 4.8 - Flume Equipped with Water Level Probes and Real Time Logger to Measure Runoff A-5

Plate 4.9 -Flume Being Calibrated in a Hydraulic Laboratory Channel A-6

Plate 4.10 - Stainless Steel Thermocouple, Duct, Connection Cables and Portable Thermometer A-7

Plate 4.11 - A Clamp-On Type Transit-Time Ultrasonic Flowmeter to measure Flow A-7

Plate 4.12 - Using Pre-calibrated Orifice Plate to Measure Gas Flow Rate A-8

Plate 4.13 - Portable Non-Dispersive Infra-red Absorption Landfill Gas Analyser A-9

Plate 4.14 -A Portable Gas Chromatograph to Measure Gas Composition A-9

Plate 5.1 - Laboratory Experimental Set-Up A-10

Plate 5.2 - Neutron Moisture Depth Probe Used in Full-Scale Trial A-11

Plate 5.3 - A “Pin And Socket” Joint Used to Connect Assess Tube Sections A-12

Plate 5.4 - Pre-Drill Access Tube Hole with a Slightly Oversized Continuos Flight Auger A-13

Plate 5.5 - Inserting Aluminium Tube into Hole through Temporary Casing A-14

Plate 5.6 - Collecting In-Situ MSW Samples to Determine Moisture Content and Composition A-15

xx

List of

Abbreviations______________________________________

AHD Australian Hard Datum

BMP Biochemical Methane Potential

BOD Biochemical Oxygen Demand

COD Chemical Oxygen Demand

Etact Actual Evapotranspiration

Etpot Potential Evapotranspiration

HELP The Hydrological Evaluation of Landfill Performance Model

LD Lateral Drainage

LFG Landfill Gas

LR Leachate Recirculation Volume

MSW Municipal Solid Waste

ORP Oxidation-Reduction (Redox) Potential

OW Open Well

PERC Percolation

PUMP Pumped leachate Volume

RF Rainfall

RO Runoff

Sbase Moisture Stored in Waste Below Saturated Level Recorded in Sump

Swaste Moisture Stored in Waste Above Basal Storage

Scell Moisture Stored in Cell (Swaste + Sbase)

TDS Total Dissolved Solids

TOC Total Organic Carbon

TS Total Solids

TSS Total Suspended Solids

v/v Moisture Measurement By Volume

VFAs Volatile Fatty Acids

VS Volatile Solids

xxi

xxii