PRESENTATION ON BIOREMEDIATION FOR TREATMENT OF ... · • Aquifer is comprised of fractured basalt...
65
Kent S. Sorenson, Jr.; Ryan A. Wymore; Jennifer P. Martin Enhanced Bioremediation for Treatment of Chlorinated Solvent Source Areas œ Case Studies and Implications
Transcript of PRESENTATION ON BIOREMEDIATION FOR TREATMENT OF ... · • Aquifer is comprised of fractured basalt...
Kent S. Sorenson, Jr.; Ryan A. Wymore; Jennifer P. Martin
Enhanced Bioremediation for Treatment of Chlorinated Solvent
Source Areas œ Case Studies and Implications
Bioremediation Background
• In Situ Bioremediation of chlorinated solvents: œ Solvents utilized as electron acceptors by
indigenous microorganisms œ Chlorine atoms sequentially replaced with
hydrogen through —reductive dechlorination“
Microbial Metabolism
Food
Electron DonorElectron Acceptor
O2
Electron Donor
Respiration Products
Electron Acceptor+ + Energy
Bioremediation Metabolism
BTEX
Food (Organic Compound)
Electron Donor
Electron Donor
Electron Acceptor
Electron Acceptor
Chlorinated Solvents
O etc.2, 3NO ,
Reductive Dechlorination
Pathway
PCE
C I
CC
ClCl
ClCl
TCE
C I
C
H
Chlorine Atom
Carbon Atom
Hydrogen Atom
Single Chemical Bond Double Chemical Bond
CC
H
Cl Cl
Cl
1,1 - DCE cis - 1,2 - DCE trans - 1,2 - DCE H
C C
H
Cl
Cl
H
C C
H Cl
Cl
C C
H H
Cl Cl
Vinyl Chloride H
C C
H H
Cl
O O
C
Complete Mineralization O
H H
Ethene H H
C C
H H
Cl
Ethane
Modified from Wiedemeier et al., 1996
H H
CC
H H
HH
A Paradigm Shift?
• Conventional applications for in situ bioremediation limited to dissolved phase for two primary reasons: œ Concerns about toxicity œ Impact on nonaqueous sources thought to be no better
than pump and treat
• New research reveals that in situ bioremediation may be extremely effective for chlorinated solvent source areas
Enhanced Mass Transfer
• In situ bioremediation can enhance mass transfer, addressing the concerns previously thought to limit bioremediation applications: œ Many investigators have shown that
dechlorinating bacteria actually have an ecological niche in high concentration areas
œ Several studies have shown that in situ bioremediation enhances mass transfer of contaminants through at least three mechanisms
Mechanisms of Enhanced Mass Transfer
• Mechanisms for enhanced mass transfer œ Bioremediation removes contaminants from the
aqueous phase, thereby increasing the driving force for mass transfer = k(Cs-C)
œ Increasing solubility of reductive dechlorination degradation products greatly increases the maximum aqueous contaminant loading
œ The electron donor solution can be used to decrease interfacial tension, thereby increasing the effective solubility
Enhanced Mass Transfer: Mechanisms 1 and 2
• Enhanced mass transfer of chlorinated solvent NAPLs due to reductive dechlorination has been demonstrated in at least two laboratory batch studies: œ Yang and McCarty (2000) showed enhanced PCE
dissolution up to a factor of 5 higher than without reductive dechlorination
œ Carr et al. (2000) showed reductions in NAPL longevity of 83% due to reductive dechlorination in continuously stirred tank reactors
Enhanced Mass Transfer: Mechanisms 1 and 2
• Enhanced mass transfer of chlorinated solvent NAPLs due to reductive dechlorination has been demonstrated in at least one laboratory column study: œ Cope and Hughes (2001) demonstrated total
chlorinated ethene removal was 5 to 6 times higher with reductive dechlorination as compared to abiotic washout
Enhanced Mass Transfer: Mechanisms 1 and 2
• Enhanced chlorinated ethene removal due to reductive dechlorination in columns with PCE DNAPL (Courtesy of Joe Hughes)
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T ime, days
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'abiotic'
Enhanced Mass Transfer: Mechanism 3
• The impact of sodium lactate and other electron donor solutions on water-TCE interfacial tension was investigated in unpublished laboratory studies
• The results supported a pending patent for the Idaho National Engineering and Environmental Laboratory
• The process is referred to as Bioavailability Enhancement TechnologyTM (B.E.T.TM)
• Bioavailability Enhancement TechnologyTM (B.E.T.TM) can accelerate removal of residual source material, while retaining the benefits of in situ bioremediation
TAN-26
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Ethe
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MW-25 Reductive Dechlorination Results
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ETH VC DCE TCE PCE
Test Area North
Seal Beach
Interfacial Tension
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Decreases in IFT caused by some electron donor solutions appear to increase effective solubility of residual nonaqueous contaminants, thereby enhancing bioavailability and accelerating mass removal
Cou
rtesy
Bec
htel
Env
ironm
enta
l, In
c.
Impact of Electron Donor Solutions
Enhanced Mass Transfer: Mechanism 3
• Enhanced mass transfer due to electron donor solution interaction with nonaqueous TCE, followed by complete reductive dechlorination has been observed in at least one field study: œ Sorenson (2002) showed that TCE
concentrations were greatly enhanced due to facilitated transport associated with the electron donor solution (concentrated sodium lactate)
œ This work will serve as the first of two case studies
Test Area North (TAN) Background • Industrial wastewater (including solvents), low-
level radioactive wastes, and sanitary sewage were injected directly to the Snake River Plain Aquifer from the late 1950s to 1972
• TCE plume is nearly 2 miles long • Residual source area is about 200 ft in diameter • Contaminated aquifer is about 200-400 ft deep • Aquifer is comprised of fractured basalt
Groundwater Flow Direction
Groundwater Flow Direction
Approximate Plume Boundary
Record of Decision (1995)
• Pump and treat selected as default remedy • Treatability studies established for
alternative technologies: œ zero-valent iron œ monolithic confinement œ in situ chemical oxidation œ in situ bioremediation œ natural attenuation
• 100-year remedial time frame
Objectives for the 1-year In Situ Bioremediation Field Evaluation
• Primary Objective: Demonstrate that biodegradation of TCE can be significantly enhanced through electron donor addition
• Create hydraulic —treatment cell“ to maintain hydraulic containment of the source area and control residence time
• Determine controls on process efficiency through extensive monitoring
Electron Donor Distribution Electron Donor in TAN-37A
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Electron Donor in TAN-37B (275') and C (379')
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Electron Donor In TAN-25
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Electron Donor in TAN-26
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Chemical Oxygen Demand Sept. 13, 1999
Impermeable Interbed
TSF-05 37 28 29
200-ft Fractured Basalt Aquifer
???
210-ft Fractured Basalt Unsaturated Zone (Not to Scale)
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Redox Conditions
Redox Indicators in TAN-37B (275') and C (379')
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Redox Indicators in TAN-25
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TCEIsoplethsTAN-D2
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TAN-28
TAN-30A
TAN-10A
TAN-29
TAN-49
TAN-27
Pre-Lactate
March 29, 1999
TAN-D2TAN-9
TAN-31
TSF-05
TAN-25TAN-26
TAN-37 TAN-28
TAN-30A
TAN-10A
TAN-29
TAN-49
TAN-27
July 20, 1999
TAN-D2TAN-9
TAN-31
TSF-05
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TAN-37 TAN-28
TAN-30A
TAN-10A
TAN-29
TAN-49
TAN-27
October 11, 1999
TAN-D2TAN-9
TAN-31
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TAN-25TAN-26
TAN-37 TAN-28
TAN-30A
TAN-10A
TAN-29
TAN-49
TAN-27
January 10, 2000
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TAN-31
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TAN-25TAN-26
TAN-37 TAN-28
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April 10, 2000
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July 5, 2000
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October 23, 2000
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TAN-31
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TAN-37B and TAN-37C
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Long-Term Dechlorination
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Enhanced Mass Transfer from DNAPL Source Area
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Status of Enhanced In Situ Bioremediation at TAN
• Formal regulatory approval to implement bioremediation at the TAN DNAPL source area as a replacement for the default remedy has been granted. signed in 2001.
A ROD amendment was
Ft. Lewis ESTCP Demonstration • The project will use two in situ treatment cells
to quantitatively demonstrate the enhanced mass transfer and degradation that occurs due to in situ bioremediation in a chlorinated solvent source area
• One cell will be operated to test the first two mass transfer mechanisms, while the other will add the third mechanism
• Drilling has been completed and construction is underway with a tracer test to begin in May
Case Study 2: Chitin as a Slow Release Electron Donor
• Application of bioremediation for a lower concentration, low permeability, variably saturated chlorinated solvent source area
• Soil fracturing required for contaminant contact
• Long-lived electron donor desirable due to remoteness of site
Distler Brickyard Site • Former waste recycling and storage facility • CAH (mainly TCE and 1,1,1-TCA) and
MAH (BTEX) contamination in soil and groundwater
• 1986 ROD selected soil excavation and pump and treat in the source area
• Pump and treat ineffective due to low permeability of formation
Distler Background (cont.) • 2 Aquifer system:
œ Fine Grained Alluvium (FGA): silts and clays, ~ 40 ft thick
œ Coarse Grained Alluvium (CGA): coarse sand and gravel, 1.5-20 ft thick, local drinking water source
• Reductive dechlorination occurring in the FGA, but not sufficient to prevent migration of contaminants to the CGA
• Redox conditions and contaminant concentrations are impacted by seasonal fluctuations in recharge
Distler Site Map
Goals for Remediation • Prevent migration of contamination to the
CGA • Enhance naturally-occurring biodegradation • Accelerate residual source removal • Low cost, low maintenance technology (in
situ is preferred) • NSF SBIR Project: Phase I Research Goal:
œ Evaluate chitin as a long-term, cost-effective amendment for accelerating reductive dechlorination in a low permeability, variably saturated chlorinated solvent source area
Summary of Lab Study Results
• Acetate and butyrate were the dominant VFAs from chitin: œ Average acetate = ~700 mg/L œ Average butyrate = ~300 mg/L
• Sustained concentrations of VFAs over 3 months • VFAs from chitin enhanced dissolution of PCE œ
after 101 days, ~35% more PCE was removed from chitin column
• VFAs from chitin supported reductive dechlorinaton of PCE
Lab Dechlorination Results
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Note: Lab culture used was only capable of dechlorination to VC
Field Test Activities • Hydraulic Fracturing
œ Created highly permeable sand- and chitin-filled fractures in the CAH source area using the FRAC RITETM process
œ Fracture zones propagated at 25, 33, and 38 ft below ground surface
• Geophysical Monitoring œ Tiltmeter monitoring and modeling of fracture
propagation and geometry • Hydrologic Monitoring
œ Pre- and post-fracing slug tests and a pumping test • Geochemical Monitoring
œ 4 monitoring wells and the fracing well œ Baseline and 4 post-chitin monitoring events
Field Test Layout
North Wind‘s Drill Rig
Monitoring the —Fracing“
The Chitin-Sand Slurry
Tilt-Meter Monitoring Results
Fracing Well Data
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VFAs:
Redox Constituents:
Chloroethenes:
Monitoring Well Data
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VFAs:
Redox Constituents:
Chloroethenes:
Conclusions • Chitin can be delivered effectively using the
fracing technique to distances of at least 13 ft (4 m) in silts and clays.
• Fracture propagation is influenced by site-specific in situ soil stress conditions.
• Chitin is degraded in situ to produce VFAs to support ARD of CAHs.
• After 9 months, significant concentrations of VFAs persisted, and CAHs were reduced below MCLs in 3 of the 5 monitoring wells, indicating that chitin is a relatively long-lived electron donor.
Future Work • NSF Phase II objectives (currently
underway): œ Implement at full-scale for protection of the
CGA œ Evaluate cost-effectiveness, including testing of
three different chitin products œ Optimize chitin distribution œ Monitor longevity of chitin in subsurface œ Monitor performance under variably saturated
conditions
Distler Acknowledgements
• NSF SBIR Phase I (Contract DMI-0109868 ).
• Collaboration among multiple federal agencies, academia, and private industry: U.S. EPA Region 4 (Femi Akindele), U.S. EPA NERL (Ken Brown), U.S. EPA TIO (Rich Steimle), U.S. DOE INEEL (Ken Moor), the State of Kentucky (Ken Logsdon), U.S.G.S. (Doug Zettwoch), University of Illinois at Urbana-Champaign
What Does All This Mean?
• What are the driving factors for effectiveness of bioremediation in source zones?
• What are the likely impacts on cleanup timeframe?
Delivery, Delivery, Delivery • Distribution of donor is critical: presence of donor ‚ reducing conditions ‚ dechlorination
• Many factors affect the ease of delivery, and with it, the selection of an appropriate electron donor: œ Volume Requiring Treatment œ Depth to Water œ Aquifer Permeability œ Ambient Aquifer Flow Rates œ Aquifer Dispersivity œ Potential for Preferential Flow (Heterogeneity) œ Viscosity of Donor Solution (including temperature
dependence) œ Solubility of Donor/Transport Characteristics
Importance of Radius of Influence • Newell (2003) estimated the number of
wells required per acre as a function of the radius of influence:
Radius of Influence (cont.)• Disparity may be even higher than
estimated by Newell as shown by the examples below
TCEIsoplethsTAN-D2
TAN-9
TAN-31
TSF-05
TAN-25TAN-26 TAN-37
TAN-28
TAN-30A
TAN-10A
TAN-29
TAN-49
TAN-27
Pre-Lactate
October 23, 2000
TAN-D2TAN-9
TAN-31
TSF-05
TAN-25TAN-26
TAN-37 TAN-28
TAN-30A
TAN-10A
TAN-29
TAN-49
TAN-27
Test Area North:
Single injection well provided treatment for an area approximately 200 ft in diameter (TCE contours shown)
Air National Guard Site:
Nine manifoldedinjection wells provided treatment for an area approximately 1800 ft long and 900 ft wide (COD concentrations shown are almost 2 months after an injection)
Courtesy SAIC
Cleanup Timeframe
Courtesy C. Newell, Groundwater Services, Inc.
Abiotic Source Lifetime
Courtesy C. Newell, Groundwater Services, Inc.
Courtesy C. Newell, Groundwater Services, Inc.
Lifetime With Biodegradation
Courtesy C. Newell, Groundwater Services, Inc.
Reality Check
Summary
• Bioremediation shows significant promise for accelerating chlorinated solvent source removal under a variety of conditions
• A —treatment train“ approach may make sense for sites with large quantities of free-phase product
• Bioremediation alone may be sufficient for sites with residual saturation conditions
