Analysis for Sequential ExSitu Remediation of an Encapsulated Contaminated Soil Pile

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Analysis for Sequential Ex-Situ Remediation of an
Encapsulated Contaminated Soil Pile

• By
• Fehmidakhatun A. Mesania
• Department of Civil Engineering
• Case Western Reserve University
• April 1st, 1999
• Ph.D. Defense Presentation

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Acknowledgments

• NSF Gateway Coalition Grant CID-U-05-CW
• NSF Grant CMS 97-13570 Design Analysis for
  Sequential Ex-situ Soil Remediation

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Presentation Outline

• Sequential Ex-Situ Remediation
• Research Objectives
• Soil Pile Treatment
• Remediation Process Modules
• Summary Conclusions
• Recommendations Future Research

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Sequential Ex-situ Approach

• Terrestrial Remediation
• Ex-Situ Remediation
• Basic Concept of Soil Pile Treatment
• . Excavation
• . Place contaminated soil atop a liner
• . Encapsulation
• . Sequential treatment processes

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Terrestrial Remediation
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Objectives

• Develop a design tool to analyze an arbitrary
  sequence of remedial actions applied to an
  ex-situ soil pile
• Develop a set of remediation modules which can be
  built into sequences
• Develop a complete set for bioremediation

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Illustration of a Soil Pile
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Soil Pile Treatment

• Soil pile contains waste
• Closed System yields higher operational control
• Apply any in-situ treatment technique
• High performance efficiency
• Low cost (gradual long term)
• Aggressive Remediation

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Analytical Domain of Soil Pile
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Process Modules

• Fluid Flow (solvent mass transport)
• Thermal Enhancement (heat transfer)
• CDMT (convective, dispersive mass transport)
• B-MCMT (biological reactions CDMT)

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Fluid Flow Model

• Simulate fluid flows in the soil pile
• Governing Equation

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Space Boundary Segment Discretization
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Solutions of the Fluid Flow Model

• Solution technique CCC finite-difference
• Solution yields potential as function of xi
• Alternatives for Plotting
• - Potential contours
• - Color graphics
• - Velocity vector fields

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Potential Contour Plots
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Velocity Vector Field
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Potential Contour Plots
K0.3
K0.1
Homogenous
Heterogeneous
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Thermal Enhancement Model

• Simulate impact of ambient temperature
• Simulate impact of heat sources
• Conduction mechanism

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Boundary Conditions

• Similar to the fluid flow module
• Along radius
• CCC finite difference in space and backward
  finite difference in time was implemented

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Impact of Ambient Temperature
Time2.5days
Time100 days
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Impact of Heat Sources
Time10 days
Time100 days
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CDMT Model

• Ogata and Banks, 1961
• Convection
• Diffusion
• Dispersion

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CDMT Equation

• A mass balance on species C1 yields

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CDMT Boundary Condition

• Initial condition
• Boundary conditions
• Along x2 Boundary
• Along x1 Boundary
• At the Radius

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Numerical Solution for CDMT

• Solution by CCC finite difference approximation
  in space and a backward finite difference
  approximation in time
• Space discretization check by Cell Peclet number
  (Pe qi?x/D)
• Time discretization check by Courant number (C
  qi?t/?x)

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CDMT Simulations
Time 0.5 day
Time2.0 days
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Impact of Sorption on CDMT
Kd0.0
Kd0.5
Time1.5 days
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CDMT Two Layered Soil Pile
K0.3
K0.1
Time0.5 day
Time1.5 days
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B-MCMT Module

• Use of microorganisms to destroy organic
  contaminants
• Involves physical, chemical, and biological
  processes
• Apply multi-component convective, dispersive,
  sorptive, reactive mass transport

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How Bioremediation Works
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M-CDMT Chemical Reaction
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B-MCMT Physical Sorption
Linear Equilibrium Sorption
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B-MCMT Bio-Chemical Interactions
Monod Kinetics
Modification required for multiple
solutes
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Modified Monod Kinetics

• Inclusion of Cimin reduces metabolism to zero
  when substrate concentration CiltCimin (no
  biological reaction if there is not enough food
  to sustain life)
• Inclusion of rate-limiting oxygen (Omin)
  utilization under aerobic conditions (no aerobic
  metabolism without sufficient oxygen)

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Modified Monod Kinetics

• Aerobic condition
• Anaerobic condition

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B-MCMT Equation Solute C2
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B-MCMT Equation Solute C3
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B-MCMT Equation Oxygen
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Numerical Solution

• Example averaging rule for solute C2

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B-MCMT Results
Oxygen Concentration
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B-MCMT Results
Substrate C2
Substrate C3
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B-MCMT Results
Substrate Concentration
Time 2.0 days
Time 1.0 day
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B-MCMT Results
Oxygen Concentration
Time 1.0 day
Time 2.0days
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Fluid Flow Module
C O N C L U S I O S

• A finite-difference solution was implemented to
  simulate fluid flow in the soil pile for flexible
  boundary conditions
• Contour plots help users visualize the potential
  field solution,?(xi)
• Velocity vector plots for q(xi) help users
  improve designs for source/sink locations
• Velocity vector field also helps quantify
  convection for CDMT Eqs.

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Thermal Enhancement
C O N C L U S I O S

• Analysis allows consideration of ambient air
  temperature and solar radiation on the soil pile
• Engineered heat sources can also be considered
• Temperature profiles u(xi,t) can be used to
  adjust physical properties and rate constants in
  another remediation modules

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B-MCMT
C O N C L U S I O S

• Handles several biodegradation options for
  aerobic and anaerobic metabolism
• Simulates chemical reactions and physical
  sorption
• Offers a great deal of mechanistic flexibility
• Numerical solution generates simultaneous
  predictions of C2(xi,t), C3(xi,t) and O2(xi,t)

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Future Research Recommendations

• Construct a ASVE and PSVE Modules
• Construct an unsaturated fluid flow model
• Implement a soil leaching model with more
  inorganic chemistry and non-linear sorption
• Develop a process sequence optimization module
• Design a bench or full scale remediation sequence
  test

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