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Chlorinated solvents (e.g., PCE & TCE) are Chlorinated solvents (e.g., PCE & TCE) are used for industrial vapor degreasingused for industrial vapor degreasing
Problem:Problem:Improper disposal of chlorinated solventsImproper disposal of chlorinated solvents
• DoDDoD • 22,089 identified contaminated sites (1995)22,089 identified contaminated sites (1995)• 49% contaminated with chlorinated solvents.49% contaminated with chlorinated solvents.• Estimated cost of remediation - $28.6 billion.Estimated cost of remediation - $28.6 billion.
• DOE DOE • 10,500 identified contaminated sites (1996) 10,500 identified contaminated sites (1996) • 25% contaminated with chlorinated solvents.25% contaminated with chlorinated solvents.• Estimated cost of remediation - $63 billionEstimated cost of remediation - $63 billion• Estimated time for remediation - 75 yearsEstimated time for remediation - 75 years
NEED - Development of technologies to reduce NEED - Development of technologies to reduce remediation costs.remediation costs.
To develop a semi-passive membrane To develop a semi-passive membrane permeable reactive barrier (PRB) remediation permeable reactive barrier (PRB) remediation technology that fosters biological destruction of technology that fosters biological destruction of chlorinated organic compounds by the controlled chlorinated organic compounds by the controlled delivery of soluble methane & oxygen gas into delivery of soluble methane & oxygen gas into the subsurface.the subsurface.
EPA, 2003EPA, 2003
DNAPL ContaminationDNAPL Contamination
EPA, 2003EPA, 2003
Recovery of “Free Product”Recovery of “Free Product”
Olaf Cirpka at Stanford has modeled Olaf Cirpka at Stanford has modeled different strategies for minimizing different strategies for minimizing biofouling in aquifers.biofouling in aquifers.
Two obstaclesTwo obstacles
• How can “capture zone” for each well How can “capture zone” for each well be increased? - Balabe increased? - Bala
• Will presence of copper in groundwater Will presence of copper in groundwater repress expression of operative TCE-repress expression of operative TCE-degrading enzyme (sMMO)? - Vipindegrading enzyme (sMMO)? - Vipin
Research Topic:Research Topic:
Characterizing effect of superimposed Characterizing effect of superimposed transverse flow on well capture zone.transverse flow on well capture zone.
Decreasing CHDecreasing CH44 “zone of influence” “zone of influence”
due to microbial accumulationdue to microbial accumulation
GW flow
Research ObjectivesResearch Objectives
Phase 1Phase 1: Characterize relationship between : Characterize relationship between well-spacing, inter-well pumping rate, and well-spacing, inter-well pumping rate, and capture zone.capture zone.
Phase 2Phase 2: Characterize relationship between : Characterize relationship between well-spacing, inter-well pumping rate, and well-spacing, inter-well pumping rate, and DCE removal efficiency.DCE removal efficiency.
Time taken for a particle to travelTime taken for a particle to travelt = LnA/Qt = LnA/Q
t-Time ,L-Length of the Sample, n-Aquifer t-Time ,L-Length of the Sample, n-Aquifer porosity, A-Area, Q-Flow Rateporosity, A-Area, Q-Flow Rate
Capture Zone:Capture Zone:
The capture zone defines the area The capture zone defines the area of an aquifer that will contribute of an aquifer that will contribute water to an extraction well within a water to an extraction well within a specified time period.specified time period.
Conceptualized flow field % Conceptualized flow field % capture vs. # of wells & pumping capture vs. # of wells & pumping
raterate
Research Topic:Research Topic:
Characterizing effect of copper loading Characterizing effect of copper loading on sMMO expression in membrane-on sMMO expression in membrane-attached methanotrophic biofilms.attached methanotrophic biofilms.
Copper Loading Effect on sMMO Expression in Copper Loading Effect on sMMO Expression in Membrane-Attached Methanotrophic BiofilmsMembrane-Attached Methanotrophic Biofilms
They are of two types – Type 1 and Type 2.They are of two types – Type 1 and Type 2.
Methane is oxidized by methanotrophs to COMethane is oxidized by methanotrophs to CO22 via via intermediates like methanol and formaldehyde.intermediates like methanol and formaldehyde.
Two enzymes sMMO and pMMO play an Two enzymes sMMO and pMMO play an important role for the oxidation of important role for the oxidation of CHCH44..
sMMO co-oxidizes a wide range of alkanes & sMMO co-oxidizes a wide range of alkanes & alkenes, including chlorinated hydrocarbons.alkenes, including chlorinated hydrocarbons.
Cu inhibits sMMO activity.Cu inhibits sMMO activity.
Problems associated with Problems associated with “copper repression of sMMO”“copper repression of sMMO”
low copper high copper
Type I pMMO
Type II pMMOsMMO
CHCH4 4 OxidationOxidation and TCE and TCE
Degradation PathwaysDegradation Pathways
HypothesesHypotheses
Methanotrophic biofilms can express sMMO Methanotrophic biofilms can express sMMO at higher copper loading rates than at higher copper loading rates than planktonic cultures.planktonic cultures.
Copper will adsorb to the inactive biomass Copper will adsorb to the inactive biomass near the biofilm surface.near the biofilm surface.
High cell growth rates will dilute copper High cell growth rates will dilute copper present in the biofilm interior & thus sMMO present in the biofilm interior & thus sMMO expression will not be repressed.expression will not be repressed.
membrane membrane wallwall
biofilmbiofilm liquidliquidfilmfilm
Copper will adsorb to surface of Copper will adsorb to surface of counter-diffusional biofilms?counter-diffusional biofilms?
TCETCE
CHCH44flux of new flux of new cellscells
CuCu
Research ObjectivesResearch Objectives
Characterize sMMO expression as function of:Characterize sMMO expression as function of:
3.3. Time (hard to predict at this moment).Time (hard to predict at this moment).
Experimental MethodsExperimental Methods
Membrane-attached methanotrophic biofilms Membrane-attached methanotrophic biofilms will be cultivated.will be cultivated.
A nitrate mineral salts medium with will be A nitrate mineral salts medium with will be used to supply nutrients (N, P, etc.).used to supply nutrients (N, P, etc.).
High CHHigh CH44 and O and O22 partial pressures will partial pressures will
promote development of thick biofilms.promote development of thick biofilms.