Long-Term Performance of Permeable Reactive Barriers (eBook)

T. Meggyes, K.E. Roehl, F.G. Simon, D.I. Stewart (Herausgeber)

eBook Download: EPUB

2005 | 1. Auflage
244 Seiten
Elsevier Science (Verlag)
978-0-08-053561-6 (ISBN)

Infos

While extensive research has been performed on many technological aspects of permeable reactive barriers and a number of contaminants have so far been successfully treated by PRB systems, long-term performance has not been extensively considered and little is known about the processes influencing long-term behaviour. This gap in our knowledge is all the more disadvantageous as design life has a decisive influence on the economic viability of PRBs.

The book describes methods for evaluation and enhancement of the long-term performance of PRB systems, especially of those targeting heavy metals, specifically uranium, and organic contaminants by sorption and/or precipitation mechanisms. Major topics in the book are:

• Selection and characterisation of suitable reactive materials


• Characterisation of the relevant contaminant attenuation processes


• Developing new contaminant-binding chemical compounds (ligands)


• Accelerated testing methods to assess the long-term performance of the attenuation mechanisms in PRBs


• Evaluation of the influence of site characteristics on PRB performance


• Monitoring of existing and new field installations


• Coupling of electrokinetic techniques and PRB systems


• Large-scale laboratory and field tests and their results

It addresses the long-term performance of PRBs, an important feature of this novel remediation technology, systematically. It deals extensively with heavy metal removal, with special emphasis on uranium. A number of case studies, experiences with large-scale modelling and test site experiments provide insight into the practical application of the results. This volume will contribute to the science underpinning groundwater remediation, and this will result in the improvement of quality of life and health and safety.

* A systematic approach to investigating the long-term performance of permeable reactive barriers
* Development of new contaminant-binding chemical compounds (ligands), accelerated testing methods to assess the long-term performance, and efficiency enhancing electrokinetic techniques
* Extensive data and information on a Hungarian uranium mining facility, once a carefully kept secret of the Soviet Union

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While extensive research has been performed on many technological aspects of permeable reactive barriers and a number of contaminants have so far been successfully treated by PRB systems, long-term performance has not been extensively considered and little is known about the processes influencing long-term behaviour. This gap in our knowledge is all the more disadvantageous as design life has a decisive influence on the economic viability of PRBs. The book describes methods for evaluation and enhancement of the long-term performance of PRB systems, especially of those targeting heavy metals, specifically uranium, and organic contaminants by sorption and/or precipitation mechanisms. Major topics in the book are:- Selection and characterisation of suitable reactive materials- Characterisation of the relevant contaminant attenuation processes- Developing new contaminant-binding chemical compounds ("e;ligands"e;)- Accelerated testing methods to assess the long-term performance of the attenuation mechanisms in PRBs- Evaluation of the influence of site characteristics on PRB performance- Monitoring of existing and new field installations- Coupling of electrokinetic techniques and PRB systems- Large-scale laboratory and field tests and their results It addresses the long-term performance of PRBs, an important feature of this novel remediation technology, systematically. It deals extensively with heavy metal removal, with special emphasis on uranium. A number of case studies, experiences with large-scale modelling and test site experiments provide insight into the practical application of the results. This volume will contribute to the science underpinning groundwater remediation, and this will result in the improvement of quality of life and health and safety.* A systematic approach to investigating the long-term performance of permeable reactive barriers* Development of new contaminant-binding chemical compounds ("e;ligands"e;), accelerated testing methods to assess the long-term performance, and efficiency enhancing electrokinetic techniques* Extensive data and information on a Hungarian uranium mining facility; once a carefully kept secret of the Soviet Union

Inhalt

Front Cover 1
Long-term Performance of Permeable Reactive Barriers 4
Copyright Page 5
Contents 6
Preface 12
Contributors 16
About the editors 18
Acknowledgements 19
Chapter 1. Permeable Reactive Barriers 20
A Introduction 20
B Concept of permeable reactive barriers 20
C Reactive materials for contaminant attenuation 24
D Application and long-term performance of PRBs 28
E Outlook 38
References 38
Chapter 2. Construction Methods of Permeable Reactive Barriers 46
A Introduction 46
B Construction of cut-off walls 46
C Construction of reactive barriers 53
References 68
Chapter 3. Materials and Processes for Uranium Removal from Contaminated Water 72
A Introduction 72
B Materials and experimental procedures 72
C. Attenuation processes 74
D. Summary and conclusions 91
References 92
Chapter 4. Behaviour of Uranium in Elemental Iron and Hydroxyapatite Reactive Barriers: Column Experiments 96
A. Introduction 96
B. Initial laboratory column test systems 100
C. Experiments with radiotracers 105
D Conclusions 118
References 119
Appendix 4A 123
Chapter 5. Laboratory Tests Using Natural Groundwater 130
A Introduction 130
B Column experiments 130
C Floor-scale tests 135
D Conclusions 148
References 149
Appendix 5A 150
Appendix 5B 151
Chapter 6. On-site Column Experiments 156
A Introduction 156
B Columns in monitoring wells 157
C Large-scale field column experiments 158
D Conclusions 169
Acknowledgement 170
References 170
Chapter 7. New Barrier Materials: The Use of Tailored Ligand Systems for the Removal of Metals from Groundwater 172
A Introduction 172
B Concept and development 173
C The preparation of PANSIL 174
D Efficiency of contaminant attenuation 175
E Technological applicability 197
F Conclusions 199
References 200
Chapter 8. Electrokinetic Techniques 202
A Introduction 202
B Scope and approach 204
C Experimental set-ups and methods 205
D Theoretical model 209
E Results 212
F Discussion and conclusions 222
G Outlook 226
References 226
Chapter 9. Mecsek Ore, Pécs, Hungary Case Study 230
A Historical overview 230
B Waste characterisation 234
C Monitoring 237
D Site characterisation, site selection 243
E Detailed investigation of Sites II and III 248
F Conclusions 261
Acknowledgements 261
References 261
Appendix 9A 262
Appendix 9B 272
Appendix 9C 276
Chapter 10. Experimental Iron Barrier in Pécs, Hungary 280
A Introduction 280
B Design of the permeable reactive barrier 280
C Construction phase 281
D Results of operation 286
E Conclusions 299
References 300
Chapter 11. Installation and Operation of an Adsorptive Reactor and Barrier (AR& B) System in Brunn am Gebirge, Austria
A Introduction 302
B General description 303
C Site assessment 305
D Concept of project implementation 308
E Assessment of system- and site-specific suitabilities 310
F AR& B system implementation
G System operation - hydraulics and water chemistry 314
H Perspectives and outlook 326
References 327
Chapter 12. Regulatory and Economic Aspects 330
A Introduction 330
B Regulatory aspects 330
C Economic aspects 335
D Outlook 339
References 339
Index 342

Textauszug

Chapter 1

Permeable reactive barriers

Karl Ernst Roehl; Kurt Czurda; Tamás Meggyes; Franz-Georg Simon; D.I. Stewart

A Introduction

The problem of anthropogenic groundwater contamination is widespread throughout Europe. Due to the large number of contaminated sites that require treatment, and in light of the incorporation of eastern European countries with their sometimes appalling ecological problems into the European Union, there is an urgent need for cost-effective risk management. In the field of contaminated groundwater, risk management typically involves remediation technologies for the control of the contaminant source and the management of contaminants along the pathway (CLARINET, 2002). The objective of the risk management is to break the link between pollutant source and receptor (such as drinking water resources) by managing or blocking the pathway.

Groundwater remediation schemes are widely used to achieve this objective, mainly based on active methods such as pump-and-treat techniques. Recently, passive treatment methods have become more widely accepted as cost-effective and sustainable solutions to various types of water and soil pollution problems. These methods include:

• natural attenuation, suitable primarily for the control of organic pollutants;

• wetland systems, as used especially for the management of mine effluents;

• permeable reactive barriers (PRBs) for groundwater remediation.

This introductory chapter intends to give a brief overview of the application of PRBs to groundwater remediation. It is also the objective of the authors to encourage further reading by giving a selection of references covering the already quite extensive literature in the field of PRB research and application.

B Concept of permeable reactive barriers

Passive in situ groundwater remediation using PRBs is a relatively new and innovative technology with a high potential to significantly reduce the cost of treating contaminated shallow aquifers and therefore contribute to the preservation of groundwater resources. A PRB is a subsurface structure situated across the groundwater flow path downstream of a contaminant plume (Fig. 1.1). The barrier is constructed totally or in part from material that is hydraulically permeable and reacts with the passing groundwater to remove the contaminants from the groundwater. Processes taking place in the reactive material of the barrier include physical, chemical or biological contaminant retention reactions and the reactions of other groundwater constituents with the material. Suitable materials for use as reactive components in PRBs are elemental iron, activated carbon, zeolites, iron oxides/oxyhydrates, phosphates, clay minerals and others. The most commonly used mechanisms are redox and sorption reactions. The choice of reactive materials and retention mechanisms are dependent on the type of contamination to be treated by the barrier system.

Figure 1.1 Schematic depiction of the PRB concept (GW, groundwater flow direction).

The concept of PRBs was first developed in North America, with pioneering work conducted at the University of Waterloo in Canada. Initially the activities, including first pilot field tests, focussed on “funnel-and-gate” systems and the abiotic reductive dehalogenation of chlorinates and recalcitrant compounds by elemental iron (Gillham and O’Hannesin, 1992, 1994; Starr and Cherry, 1994; Tratnyek, 1996; Vidic and Pohland, 1996; Sivavec et al., 1997; Tratnyek et al., 2003). During the 1990s, research activities on PRBs increased significantly leading to a number of new approaches in terms of PRB design, suitable reactive materials and target contaminants.

Amongst the first and most widely studied metal compounds treated by PRBs are chromate (Powell et al., 1995; Blowes et al., 1997) and uranyl (Cantrell et al., 1995; Bostick et al., 1997; Dwyer and Marozas, 1997) which are usually treated by reductive processes using, for example, elemental iron. The use of PRBs for groundwater protection or remediation has also been studied in other fields, e.g. the treatment of metals-containing mine waters (Morrison and Spangler, 1992, 1993; Thombre et al., 1997; Waybrant et al., 1998; Benner et al., 1999; Naftz et al., 1999; Younger, 2000; Waybrant et al., 2002). According to Blowes et al. (2000), the treatment of inorganic anions and cations can be grouped into abiotic reduction and immobilisation (mostly by elemental iron), biologically mediated reduction and immobilisation (bacterial sulphate reduction and precipitation of metals as sulphide), and adsorption and precipitation reactions.

PRBs are defined by the US Environmental Protection Agency as “passive in-situ treatment zones of reactive material that degrades or immobilises contaminants as ground water flows through it. PRBs are installed as permanent, semi-permanent, or replaceable units across the flow path of a contaminant plume. Natural gradients transport contaminants through strategically placed treatment media. The media degrade, sorb, precipitate, or remove chlorinated solvents, metals, radionuclides, and other pollutants” (EPA, 1999). The substantial deviation from common remediation techniques is that the contaminant plume, and not its source, is treated (Schad and Grathwohl, 1998).

The selection of the reactive material to be used in a PRB depends on the type of contaminant and the remediation approach (contaminant removal mechanism). In general, contaminants can be removed from polluted water by the following processes:

• Degradation. Application of chemical or biological reactions that lead to the decomposition of contaminants and the formation of harmless compounds which are either retained in the barrier or released downstream.

• Precipitation. Immobilisation of contaminants by formation of insoluble compounds (minerals), often after first reducing the contaminant to a less-soluble species. The immobilised contaminants remain in the barrier material.

• Sorption. Immobilisation of contaminants by adsorption or complex formation. The immobilised contaminants remain in the barrier material.

Frequently, groundwater treatment can involve a combination of these processes which cannot be individually distinguished. Nowadays the most widely used approaches for PRBs can be grouped into two categories: reductive barriers and sorption barriers. Reductive barriers employ mechanisms that lead to the reduction of the target compound, or parts thereof, to achieve decomposition or immobilisation of that compound. Barriers utilising surface reactions that lead to immobilisation of the target contaminants by adsorption, ion exchange, co-precipitation, solid-solution formation, etc. without altering the chemical state of the contaminant are usually termed as sorption barriers.

To date, two main types of PRB have been used in the field. These are (i) continuous reactive barriers enabling a flow through its full cross-section, and (ii) “funnel-and-gate” systems (Starr and Cherry, 1994) in which only special “gates” are permeable to the contaminated groundwater. The continuous PRB configuration is characterised by a single reactive zone installed across the contaminant plume, while the “funnel-and-gate” system consists of an impermeable wall that directs the contaminated plume through one or more permeable gates within the wall (Fig. 1.2).

Figure 1.2 Basic types of PRB configuration: (a) continuous barrier, (b) “funnel-and-gate” system.

The choice between the two configurations depends on the hydrogeological characteristics of the site, the technical applicability of the barrier placement, and on the cost of the reactive material. When a high-cost reactive material is used, the “funnel-and-gate” configuration is preferable since the reactive zone requires less material. If a cheap material can be used, it is more profitable to avoid the construction of the impermeable side-walls by employing a continuous barrier.

New approaches to the PRB concept can be imaginable which modify the initial ideas. Containment of a contaminated site can be coupled with “gates” comprising reactors treating contaminants leached from the soil by infiltrating rain water. Contaminated surface and ground water from polluted sites could be collected in trenches or drains and treated in underground reactors before being discharged into a nearby river or sewer. Another option using in situ reactive zones is the so-called Geosyphon system, which utilises gravitational hydraulic gradients in pipes to draw contaminated groundwater through a treatment reactor filled with suitable reactive material (Jones et al., 2002). For greater depths, where conventional PRBs cannot be easily constructed, Freethey et al. (2002) have proposed the deep aquifer remediation tool (DART) which consists of non-pumping wells filled with reactive material. These examples show that a variety of approaches and solutions exist that make it possible to adapt the PRB technique to specific site conditions and...

Produkt-Details

• Erscheint lt. Verlag: 27.4.2005
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geologie
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geophysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie
• Themenwelt: Technik ► Umwelttechnik / Biotechnologie
• ISBN-10: 0-08-053561-5 / 0080535615
• ISBN-13: 978-0-08-053561-6 / 9780080535616