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