Natural Attenuation of Landfill Leachate: a Combined

2,08

MB

Biogeochemical Process Analysis and Microbial Ecology

154

stron

Approach

3552

ID

Faculty of Earthand Life Sciences, Vrije Universiteit Amsterdam

2003

rok

CONTENTS

1 General introduction 1

1.1 Background 1

1.2 The act of natural attenuation: degradation and redox reactions 3

1.3 Monitoring and evaluating MNA 5

1.4 Specific objectives 8

1.5 Outline and general methodology 9

2 Biogeochemistry and isotope geochemistry of the Banisveld landfill leachate plume 11

2.1 Introduction 12

2.2 Field site description 13

2.3 Methods 13

2.3.1 Geophysical methods 13

2.3.2 Groundwater sampling and analysis 13

2.3.3 Sediment sampling and analysis 16

2.3.4 Geochemical calculations 17

2.4 Delineation of the leachate plume 17

2.5 Hydrogeochemistry 18

2.5.1 Composition of the leachate and pristine groundwater 18

2.5.2 Fate of organic carbon in the plume 18

2.5.3 Distribution of redox species 19

2.5.4 Gibbs free energy of hydrogen-oxidizing redox reactions 22

2.5.5 Distribution of dissolved gases and degassing 25

2.6 Isotope geochemistry 26

2.6.1 13C of dissolved organic carbon 26

2.6.2 13C of dissolved inorganic carbon 27

2.6.3 13C and 2H of methane 27

2.6.4 34S of sulfate 28

2.7 Quantification of redox and geochemical processes in the plume 28

2.8 Conclusions 31

3 Physiological pro ling of microbial communities in the contaminated aquifer

3.1 Introduction 34

3.2 Methods 34

3.3 Results and discussion 35

3.4 Conclusions 40

4 Relationships between microbial community structure and hydrogeochemistry 41

4.1 Introduction 42

4.2 Materials and methods 43

4.2.1 Site description and installation of observation wells 43

4.2.2 Sampling 44

4.2.3 Chemical analysis 44

4.2.4 DGGE Pro ling 44

4.2.5 Cloning and sequencing of 16S rDNA 45

4.2.6 MPN-PCR 45

4.2.7 Nucleotide sequence accession numbers 46

4.3 Results 46

4.3.1 Hydrogeochemistry of the landfill leachate plume 46

4.3.2 Microbial community structure within the aquifer 47

4.3.3 Composition of microbial communities in groundwater 49

4.3.4 Geochemistry and microbial community structure of sediment 54

4.4 Discussion 54

4.4.1 Comparison between microbial community structures from groundwater and sediment 55

4.4.2 Groundwater community structure in relation to pollution and redox processes 55

4.4.3 Community structure and degradation in the leachate plume 57

5 Reactive transport modelling of biogeochemical processes within the leachate plume 59

5.1 Introduction 60

5.2 Construction of the reactive transport model 61

5.2.1 Banisveld landfill research site 61

5.2.2 Model code 62

5.2.3 Simulation of transport 62

5.2.4 Composition of leachate and pristine groundwater 62

5.2.5 Simulation of the biogeochemical processes 64

5.2.6 Calibration of the reactive transport model using PEST 67

5.3 Results of reactive transport modelling 68

5.3.1 Cation-exchange and proton-buffering 68

5.3.2 Degradation of DOC coupled to iron reduction 70

5.3.3 Precipitation of calcite and siderite 70

5.3.4 Degassing 73

5.3.5 Modelling of the carbon isotope geochemistry 74

5.4 Discussion 76

5.4.1 Model improvement by simulating microbial growth? 76

5.4.2 Kinetics of carbonate mineral precipitation 77

5.4.3 Determination of redox rates by geochemical modelling 79

5.4.4 Factors controlling iron reduction kinetics in leachate plumes 79

5.5 Conclusion 81

6 Biogeochemical processes at the fringe of the plume 83

6.1 Introduction 84

6.2 Material, methods and eld work 86

6.2.1 Overview of multi-level-sampler (MLS) systems 86

6.2.2 MLS designed for the present study 87

6.2.3 Installation of the MLS 88

6.2.4 Groundwater sampling and analysis 90

6.3 Results 90

6.3.1 Mixing between leachate and pristine groundwater 90

6.3.2 Upward movement of leachate plume 91

6.3.3 Distribution of redox species and occurrence of redox processes across the fringe 94

6.3.4 Impact of cation-exchange reactions and proton-buffering 96

6.3.5 Fate of methane: degassing and anaerobic methane oxidation 97

6.4 Reactive transport modelling of the rising plume fringe 98

6.4.1 Model set-up and calibration 98

6.4.2 Model results 99

6.4.3 General model for secondary redox reactions at the fringe of a landfill leachate plume 100

6.5 Discussion and conclusion 102

7 Synthesis 105

7.1 Biogeochemistry and microbial ecology of the Banisveld landfill leachate plume: summary and

conclusions 105

7.1.1 Determination of redox conditions in the aquifer 105

7.1.2 Modelling the downstream change in leachate composition 106

7.1.3 Biogeochemical processes at the top fringe of the plume 107

7.1.4 Development of redox conditions in the plume 107

7.1.5 Microbial ecology of the aquifer 108

7.2 Natural attenuation potential for the Banisveld land ll leachate plume109

7.3 Development of the redox sequence and associated degradation potential in landfill leachate

plumes 110

7.4 Availability of Fe(III)-oxide for iron reduction in leachate plumes 112

7.5 Molecular microbial ecology research: perspectives for MNA 113

7.6 Directions for future research to natural attenuation of landfill leachate115

7.7 Current needs in MNA as remediation strategy for landfill leachate plumes 117

References 121

Samenvatting 135

Dankwoord 139