a semi-passive permeable reactive barrier (prb) remediation technology using membrane-attached...
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A Semi-Passive A Semi-Passive
Permeable Reactive Barrier (PRB) Permeable Reactive Barrier (PRB)
Remediation Technology Using Remediation Technology Using
Membrane-Attached BiofilmsMembrane-Attached Biofilms
Lee ClappLee Clapp
Bala VeerasekaranBala Veerasekaran
Vipin SumaniVipin Sumani
February 5, 2003February 5, 2003
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.
(Ref: EPA-542-R-96-005)(Ref: EPA-542-R-96-005)
Magnitude of Problem:Magnitude of Problem:
Water Table
Groundwaterflow
ContaminantContaminantPlumePlume
ConfiningConfiningLayerLayer
Overall Research GoalOverall Research Goal
Hollow-Fiber MembraneHollow-Fiber MembraneSemi-Passive Semi-Passive
Permeable Reactive BarrierPermeable Reactive Barrier
BacteriumBacterium
Hollow FiberHollow Fiber
CH4
CH4
Biofilm
MembraneMembrane
CH4
DCE
CO2 + Cl-
VC
CO2 + Cl-
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”
EPA, 2003EPA, 2003
Pump & TreatPump & Treat
Permeable Reactive Barrier (PRB) Remediation Technology
Regenesis, 2003Regenesis, 2003
Wells loaded with Wells loaded with HRC or ORCHRC or ORC
GeoprobeGeoprobeTMTM Direct Push Technology Direct Push Technology
H2 initially detected in these wells& a sampling well 6 ft downstream
direction of groundwater flow
Passive Membrane PRB System Passive Membrane PRB System at TCAAP Superfund Siteat TCAAP Superfund Site
hydrogen added to these wells
Two processes for chlorinated Two processes for chlorinated solvent biodegradationsolvent biodegradation
• (1)(1) Reductive dechlorination Reductive dechlorination removes one removes one chlorine at a time (anaerobic).chlorine at a time (anaerobic).
• (2)(2) Cometabolic oxidation Cometabolic oxidation results in >99% results in >99% mineralization (aerobic).mineralization (aerobic).
TCE TCE CO CO22 + Cl + Cl--
OO22
CHCH44
H2 HCl H2 HCl H2 HCl H2 HCl
PCE TCE cis-DCE VC ETH
(1) Previous research with (1) Previous research with reductive dechlorination reductive dechlorination
processesprocesses
Using hollow-fiber membranes to supply H2 to contaminated aquifers
Geoprobewell
~ 4 cmaquaclude
H2
flow
PCEplume
H2 HCl
PCE
TCE
H2 gas
hollow-fibermembranes
TCEDCE VC ETH
CH4
H2 HCl
DCE VC
4H2 2H2O
CO2
CH4
Problems with enhanced reductive Problems with enhanced reductive dechlorination for CAH remediation.dechlorination for CAH remediation.
• Accumulation of intermediate Accumulation of intermediate transformation products (DCE & VC).transformation products (DCE & VC).
• Microbial competition for HMicrobial competition for H22..
• MCLs below threshold concentrations MCLs below threshold concentrations required for dechlorinator growth.required for dechlorinator growth.
• Aquifer biofouling.Aquifer biofouling.
• Adverse impact on groundwater quality.Adverse impact on groundwater quality.
soilsoil
columncolumn
reactorsreactors
Membrane Module (single fiber)Membrane Module (single fiber)
Concentrations of PCE & byproducts in Concentrations of PCE & byproducts in test columntest column (H (H22 added) after ~1 year added) after ~1 year
0
2
4
6
8
-10 0 10 20 30 40 50 60
distance from membrane module (cm)
co
nc
en
tra
tio
n (
uM
)
0.00
0.05
0.10
0.15
0.20
0.25
VC
co
nc
en
tra
tio
n (
uM
)
PCE TCE cis-DCE VC
Concentrations of PCE & byproducts in Concentrations of PCE & byproducts in control columncontrol column (no H (no H22) after ~1 year) after ~1 year
0
2
4
6
8
-10 0 10 20 30 40 50 60
distance from membrane module (cm)
co
nc
en
tra
tio
n (
uM
)
0.00
0.05
0.10
0.15
0.20
0.25
VC
co
nc
en
tra
tio
n (
uM
)
PCE TCE cDCE VC
Concentrations of PCE & byproducts in Concentrations of PCE & byproducts in test columntest column after ~1 year after ~1 year
0
200
400
600
800
1000
-10 0 10 20 30 40 50 60distance from membrane module (cm)
con
cen
trat
ion
(u
M)
H2 CH4
Concentrations of HConcentrations of H22 in in
control columncontrol column after ~1 year after ~1 yearH2
0.0
0.1
0.2
0.3
-10 0 10 20 30 40 50 60
distance from membrane module (cm)
Co
nc
en
tra
tio
n (
uM
)
H2
Model predictions for HModel predictions for H22
concentrations over timeconcentrations over time
0.00
0.10
0.20
0.30
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7distance from H2-delivery membranes (cm)
H2 (m
M)
2 days
6 days
8 days
10 days
12 days
14 days
16 days
20 days40 days40 days2 days
FLOW
Simulated aquifer studiesSimulated aquifer studies
Previous research with Previous research with cometabolic (aerobic) cometabolic (aerobic)
degradation processesdegradation processes
TCE plume
compressed
CH4 tank
aircompresso
r CH4 explosion hazard,
vapor-phase TCE
gas-channelingthru porous media
vapor treatment
bloweblowerr
atmospheric atmospheric dischargedischarge
gas extraction well
TCE
Cl-
CO2CH4
TCE plume
compressed
CH4 tank
aircompresso
r
What if CHWhat if CH44-utilizing-utilizing
bacteria grew as bacteria grew as biofilms on surfacebiofilms on surface
of membranes?of membranes?
CHCH44
OO22TCE
Cl-
CO2CH4
growing cells growing cells utilizing CHutilizing CH44
non-growing cells non-growing cells cometabolizing TCEcometabolizing TCE
Biofilm stratificationBiofilm stratification
inactivated cellsinactivated cells
erosionerosion
continuous flux of continuous flux of new cellsnew cells
membrane
CHCH4 4 & & OO22
SEM of biofilm cross-sectionSEM of biofilm cross-section
flux of new flux of new cellscells
Biofilm viability stainingBiofilm viability staining
cells with compromised
membranes stained red with propidium
iodide
viable cells stained green with “Syto 9”
Other modeling studiesOther modeling studies
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.
Modeling Methods:Modeling Methods:
GMS (Groundwater Modeling System)GMS (Groundwater Modeling System)
– ModFlowModFlow
– ModPathModPath
– RT3DRT3D
Basic Concepts in Basic Concepts in Groundwater FlowGroundwater Flow
Darcy’s Law: QDarcy’s Law: Qxx = -K = -KxxA (hA (h22 – h – h11)/L)/L
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.
Well capture zoneWell capture zone
Assumed Parameter ValuesAssumed Parameter Values
Grid: 20 ft Grid: 20 ft 20 ft. 20 ft.
Aquifer Hydraulic Conductivity =8.42ft/dayAquifer Hydraulic Conductivity =8.42ft/day
Head: Left=10ft , Right=9.57ftHead: Left=10ft , Right=9.57ft
Aquifer Porosity=0.35Aquifer Porosity=0.35
Well Hydraulic Conductivity=842 ft/dayWell Hydraulic Conductivity=842 ft/day
Well Porosity=1.0Well Porosity=1.0
Unconfined AquiferUnconfined Aquifer
ref: Wilson & MacKay, 1997.ref: Wilson & MacKay, 1997.
9.99
9.99
9.95
9.95
9.91
9.91
9.88
9.88 9.84
9.84
X
Y
Z
Isopotential LinesIsopotential Lines
9.99
9.99
9.95
9.95
9.91
9.91
9.88
9.88 9.84
9.84
X
Y
Z
Particle Paths (Flow Direction)Particle Paths (Flow Direction)
9.99
9.99
9.95
9.95
9.91
9.91
9.88
9.88 9.84
9.84
X
Y
Z
Capture zone without pumpingCapture zone without pumping
Unpumped Well
Unpumped Well
Capture zone with pumpingCapture zone with pumping
10.01
9.96
9.96
9.96
9.96
9.91
9.919.91
9.91
9.86
9.86
9.86
9.86
9.81
9.81
9.81
9.81Extraction Well 1
Extraction Well 2
Injection Well 2
Injection Well 1
X
Y
Z
extraction well
extraction well
injection well
injection well
36.876 43.753 50.629 57.505 64.382 71.258 78.134 85.011 91.887 98.763 above
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
Methanotrophs - methane oxidizing bacteria.Methanotrophs - methane oxidizing bacteria.
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:
1.1. Copper loading.Copper loading.
2.2. CHCH44/O/O2 2 partial pressures.partial pressures.
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.
Membrane-attached methanotrophic Membrane-attached methanotrophic biofilm formationbiofilm formation
Analytical MethodsAnalytical Methods
Headspace GC/ECD (electron capture Headspace GC/ECD (electron capture detector) for TCE.detector) for TCE.
Headspace GC/TCD (thermal conductivity Headspace GC/TCD (thermal conductivity detector) for detector) for CHCH44..
IC for chloride ion.IC for chloride ion.
DO meter.DO meter.
pH meter, etc.pH meter, etc.
Expected ResultsExpected Results
TC
E d
egra
datio
n r
ate
TC
E d
egra
datio
n r
ate
YJYJCH4CH4 /J /JCUCU
pMMOpMMO
sMMOsMMO
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