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Lee Clapp Bala Veerasekaran Vipin Sumani February 5, 2003

A Semi-Passive Permeable Reactive Barrier (PRB) Remediation Technology Using Membrane-Attached Biofilms. Lee Clapp Bala Veerasekaran Vipin Sumani February 5, 2003. Chlorinated solvents (e.g., PCE & TCE) are used for industrial vapor degreasing. Problem:

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Lee Clapp Bala Veerasekaran Vipin Sumani February 5, 2003

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  1. A Semi-Passive Permeable Reactive Barrier (PRB) Remediation Technology Using Membrane-Attached Biofilms Lee Clapp Bala Veerasekaran Vipin Sumani February 5, 2003

  2. Chlorinated solvents (e.g., PCE & TCE) are used for industrial vapor degreasing

  3. Problem: Improper disposal of chlorinated solvents

  4. Magnitude of Problem: • DoD • 22,089 identified contaminated sites (1995) • 49% contaminated with chlorinated solvents. • Estimated cost of remediation - $28.6 billion. • DOE • 10,500 identified contaminated sites (1996) • 25% contaminated with chlorinated solvents. • Estimated cost of remediation - $63 billion • Estimated time for remediation - 75 years NEED - Development of technologies to reduce remediation costs. (Ref: EPA-542-R-96-005)

  5. Hollow-Fiber Membrane Semi-Passive Permeable Reactive Barrier DCE CO2 + Cl- VC CO2 + Cl- CH4 Water Table CH4 Groundwater flow CH4 Confining Contaminant Biofilm Bacterium Layer Plume Hollow Fiber Membrane Overall Research Goal To develop a semi-passive membrane permeable reactive barrier (PRB) remediation technology that fosters biological destruction of chlorinated organic compounds by the controlled delivery of soluble methane & oxygen gas into the subsurface.

  6. DNAPL Contamination EPA, 2003

  7. Recovery of “Free Product” EPA, 2003

  8. Pump & Treat EPA, 2003

  9. Wells loaded with HRC or ORC Permeable Reactive Barrier (PRB) Remediation Technology Regenesis, 2003

  10. GeoprobeTM Direct Push Technology

  11. hydrogen added to these wells H2initially detected in these wells & a sampling well 6 ft downstream direction of groundwater flow Passive Membrane PRB System at TCAAP Superfund Site

  12. H2 HCl H2 HCl H2 HCl H2 HCl PCE TCE cis-DCE VC ETH O2 TCE  CO2 + Cl- CH4 Two processes for chlorinated solvent biodegradation • (1) Reductive dechlorination removes one chlorine at a time (anaerobic). • (2) Cometabolic oxidation results in >99% mineralization (aerobic).

  13. (1) Previous research with reductive dechlorination processes

  14. H2 gas 4H2 2H2O Geoprobe well H2 HCl H2 HCl hollow-fiber membranes PCE plume CO2 CH4 CH4 H2 DCE VC PCE TCE TCE DCE VC ETH ~ 4 cm Using hollow-fiber membranes to supply H2 to contaminated aquifers flow aquaclude

  15. Problems with enhanced reductive dechlorination for CAH remediation. • Accumulation of intermediate transformation products (DCE & VC). • Microbial competition for H2. • MCLs below threshold concentrations required for dechlorinator growth. • Aquifer biofouling. • Adverse impact on groundwater quality.

  16. soil column reactors

  17. Membrane Module (single fiber)

  18. Concentrations of PCE & byproducts in test column (H2 added) after ~1 year

  19. Concentrations of PCE & byproducts in control column (no H2) after ~1 year

  20. Concentrations of PCE & byproducts in test column after ~1 year

  21. Concentrations of H2 in control column after ~1 year

  22. Model predictions for H2 concentrations over time

  23. Simulated aquifer studies

  24. Previous research with cometabolic (aerobic) degradation processes

  25. atmospheric discharge blower air compressor vapor treatment compressed CH4 tank CH4 explosion hazard, vapor-phase TCE gas extraction well TCE Cl- TCE plume gas-channeling thru porous media CH4 CO2

  26. air compressor compressed CH4 tank TCE Cl- TCE plume CH4 CO2 CH4 O2 What if CH4-utilizing bacteria grew as biofilms on surface of membranes?

  27. growing cells utilizing CH4 non-growing cells cometabolizing TCE inactivated cells CH4 & O2 continuous flux of new cells erosion Biofilm stratification membrane

  28. flux of new cells SEM of biofilm cross-section

  29. cells with compromised membranes stained red with propidium iodide viable cells stained green with “Syto 9” Biofilm viability staining

  30. Other modeling studies • Olaf Cirpka at Stanford has modeled different strategies for minimizing biofouling in aquifers.

  31. Two obstacles • How can “capture zone” for each well be increased? - Bala • Will presence of copper in groundwater repress expression of operative TCE-degrading enzyme (sMMO)? - Vipin

  32. Research Topic: • Characterizing effect of superimposed transverse flow on well capture zone.

  33. Decreasing CH4 “zone of influence” due to microbial accumulation GW flow

  34. Research Objectives • Phase 1: Characterize relationship between well-spacing, inter-well pumping rate, and capture zone. • Phase 2: Characterize relationship between well-spacing, inter-well pumping rate, and DCE removal efficiency.

  35. Modeling Methods: • GMS (Groundwater Modeling System) • ModFlow • ModPath • RT3D

  36. Basic Concepts in Groundwater Flow • Darcy’s Law: Qx = -KxA (h2 – h1)/L • Time taken for a particle to travelt = LnA/Q • t-Time ,L-Length of the Sample, n-Aquifer porosity, A-Area, Q-Flow Rate

  37. Capture Zone: The capture zone defines the area of an aquifer that will contribute water to an extraction well within a specified time period.

  38. Well capture zone

  39. Assumed Parameter Values • Grid: 20 ft  20 ft. • Aquifer Hydraulic Conductivity =8.42ft/day • Head: Left=10ft , Right=9.57ft • Aquifer Porosity=0.35 • Well Hydraulic Conductivity=842 ft/day • Well Porosity=1.0 • Unconfined Aquifer ref: Wilson & MacKay, 1997.

  40. Isopotential Lines

  41. Particle Paths (Flow Direction)

  42. Capture zone without pumping Unpumped Well Unpumped Well

  43. Capture zone with pumping injection well extraction well injection well extraction well

  44. Conceptualized flow field % capture vs. # of wells & pumping rate

  45. Research Topic: • Characterizing effect of copper loading on sMMO expression in membrane-attached methanotrophic biofilms.

  46. Copper Loading Effect on sMMO Expression in Membrane-Attached Methanotrophic Biofilms • Methanotrophs - methane oxidizing bacteria. • They are of two types – Type 1 and Type 2. • Methane is oxidized by methanotrophs to CO2 via intermediates like methanol and formaldehyde. • Two enzymes sMMO and pMMO play an important role for the oxidation of CH4. • sMMO co-oxidizes a wide range of alkanes & alkenes, including chlorinated hydrocarbons. • Cu inhibits sMMO activity.

  47. Problems associated with “copper repression of sMMO”

  48. CH4 Oxidationand TCE Degradation Pathways

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