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Model assessment of reductive dechlorination as a remediation technology for contaminant sources in fractured clay: Modeling tool

Contents

Preface

Sammenfatning

Summary and conclusion

1 Background information

• 1.1 Overview of contamination in fractured clay-till
• 1.2 Modeling objectives

2 Modeling approach

• 2.1 Conceptual model
  • 2.1.1 Different fracture network scenarios – different conceptual models
  • 2.1.2 Single fracture/matrix model and aquifer model
  • 2.1.3 Expected outputs from the model
• 2.2 Description of processes - Use of “sub-models”
• 2.3 Modeling tool – Comsol Multiphysics

3 Modeling TCE dechlorination

• 3.1 Reductive sequential dechlorination
• 3.2 Experimental data
  • 3.2.1 “Ideal conditions” microcosm experiments
• 3.3 Model implementation
• 3.4 Model parameters optimization
  • 3.4.1 Optimization on Friis et al. [2007] experimental data
  • 3.4.2 Simulation of treatability study data– sand samples
• 3.5 Coupling to the transport model

4 Transport in the clay matrix

• 4.1 Theory
• 4.2 Experimental data
• 4.3 Modeling approach
  • 4.3.1 Conceptual model
  • 4.3.2 Parameters
  • 4.3.3 Model results
  • 4.3.4 Degradation in the clay matrix
• 4.4 Summary of the matrix sub-model

5 Coupling of the “sub-models”

• 5.1 Theory
  • 5.1.1 Transport equations in matrix and fracture
  • 5.1.2 Determination of flow through fracture
• 5.2 Single fracture/matrix model
  • 5.2.1 Model set-up
  • 5.2.2 Model outputs
  • 5.2.3 Advective/Diffusive transport through fracture and matrix
  • 5.2.4 Degradation scenarios
  • 5.2.5 Sensitivity analysis
• 5.3 Aquifer model
  • 5.3.1 Presentation of model
  • 5.3.2 Model outputs
• 5.4 Improving the modeling tool

6 Modeling tool - case-study

• 6.1 Introduction
• 6.2 Presentation of the site
  • 6.2.1 Characterization of the clay system
  • 6.2.2 Characterization of the source
  • 6.2.3 Characterization of the secondary aquifer
• 6.3 Results from 2D
  • 6.3.1 Model with a homogenous source
  • 6.3.2 Distributed source concentration and transient model
• 6.4 Application of the modeling tool to other real cases
• 6.5 Application of the modeling tool to real cases

List of references

Appendix A List of abbreviations

Appendix B Processes and modeling of TCE sequential dechlorination

• B.1 Kinetics models
  • B.1.1 Competition between chlorinated ethenes
  • B.1.2 Haldane inhibition
  • B.1.3 Limiting substrate conditions
  • B.1.4 Biomass growth
  • B.1.5 Other competitive processes
  • B.1.6 Fermentation process
  • B.1.7 Conclusion

Appendix C Results from treatability study experiments

Appendix D Assessment of the different processes

• D.1 Limiting substrate conditions
• D.2 Competitive inhibition between chlorinated ethenes
• D.3 Haldane inhibition
• D.4 Biomass growth/decay

Appendix E Sensitivity analysis

• E.1 Estimation of X2o
• E.2 Sensitivity assessment
  • E.2.1 Parameter value range in literature
  • E.2.2 Sensitivity analysis results
• E.3 Experimental data from [Friis et al., 2007]

Appendix F Model verification – analytical solution

Appendix G Three different scenarios (advective dominant, diffusive dominant and no fracture)

• G.1 Scenario presentation
• G.2 Assessment of relative importance of advective vs. diffusive flux

Appendix H Impact of the choice of initial condition

Appendix I Different degradation scenarios

Appendix J Sensitivity analysis

• J.1 Sensitivity to fracture aperture and spacing
• J.2 Global sensitivity analysis

Appendix K Aquifer model - Sensitivity analysis

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Version 1.0 July 2009, © Danish Environmental Protection Agency