IN-SITU BIOLOGICALLY MEDIATED REMEDIATION
Margy Gentile
September 30, 2016
© Arcadis 2016
Disclaimers and NoticesThe materials herein are intended to furnish viewers with a summary and overview of general information on matters that they may find to be of interest, and are provided solely for personal, non-commercial, and informational purposes. The materials and information contained herein are subject to continuous change and may not be current, correct, or error free, and should not be construed as professional advice or service. You should consult with an Arcadis or other professional familiar with your particular factual situation for advice concerning specific matters.
THE MATERIALS AND INFORMATION HEREIN ARE PROVIDED "AS IS" AND “WITH ALL FAULTS” AND WITHOUT ANY REPRESENTATION OR WARRANTY, EXPRESS, IMPLIED OR STATUTORY, OF ANY KIND BY ARCADIS, INCLUDING, BUT NOT LIMITED TO, WARRANTIES OF MERCHANTABILITY, NON-INFRINGEMENT, NO ERRORS OR OMISSIONS, COMPLETENESS, ACCURACY, TIMELINESS, OR FITNESS FOR ANY PARTICULAR PURPOSE. ARCADIS DISCLAIMS ALL EQUITABLE INDEMNITIES. ANY RELIANCE ON THE MATERIALS AND INFORMATION HEREIN SHALL BE AT YOUR SOLE RISK. ARCADIS DISCLAIMS ANY DUTY TO UPDATE THE MATERIALS. ARCADIS MAY MAKE ANY OTHER CHANGES TO THE MATERIALS AT ANY TIME WITHOUT NOTICE.
The materials are protected under copyright laws and may not be copied, reproduced, transmitted, displayed, performed, distributed, rented, sublicensed, altered, or otherwise used in whole or in part without Arcadis' prior written consent.
© Arcadis 2016
About the Presenter
c 1 510 432 6251e [email protected]
MARGARET GENTILE, PHD, PEAssociate Vice President, Principal EngineerIn-Situ Reactive Treatment Lead for Arcadis North America
16 years of experience in environmental engineering with a strong focus on in-situ remediation design, implementation, and optimization for organic and inorganic contaminants. She particularly enjoys providing technical expertise on microbial and geochemical aspects of treatment, remediation of metals, and tackling large, complex plumes.
© Arcadis 2016
Learning Objectives
After attending this session, participants should be able to:Define the keys to successful in-situ bioremediationRecognize the microbial mechanisms of treatment and which are appropriate for a given COCExplain the importance of reagent distribution and residence time for effective in-situ treatment
© Arcadis 2016
Keys to In-Situ Biologically-Mediated Remediation• Microbiology: Stimulate appropriate
biogeochemical conditions
• Achieve adequate reagent distribution in the subsurface
• Provide sufficient residence time (function of reaction kinetics and groundwater flow conditions)
© Arcadis 2016
Microbially Catalyzed
Biologically Mediated Treatment
COC = Electron Donor
Biological Oxidation
Reagent = Electron Donor
COC = Electron Acceptor
Biological Reduction
Reagent = Electron Acceptors
Microbiology
© Arcadis 2016
Engineering DistributionThere are a number of ways to deliver reagent
• Biological processes require sustained treatment
− Requires constant electron donor & acceptor supply
• Dosing design is site-specific− Volume− Frequency− Hydrogeology
SpargingGroundwater Recirculation
Land Application
Reagent Distribution
© Arcadis 2016
Injection Volumes and Injection Point Spacing
2inj inj mVol h r= π ⋅ ⋅ ⋅ θ
Injection volume
Screened interval Injection
radiusMobile porosity
For fluid injections:
Reagent Distribution
© Arcadis 2016
In-Situ Biological Treatment Design
Residence time within IRZ must be sufficient for transformationFlushing zone designed to exchange pore volumes for concentration decline
Reagent
Injection Zone
Groundwater FlowSection View
In-Situ Reactive Zone (IRZ) Flushing Zone
Residence Time
Downgradient transportof soluble reagents with
slow degradation rates
In-Situ Biological Reduction
Microbiology Design Adaptive Management
© Arcadis 2016
Microbially Catalyzed
Biologically Mediated Treatment
Reagent = Electron DonorSoluble organic compoundsSemi-soluble organic compounds
COC = Electron AcceptorChlorinated organics
Redox sensitive metalsExplosives
Biological Reduction
Microbiology
© Arcadis 2016
Reductive Dechlorination Pathways
PCETetrachloroethene
TCETrichloroethene
cis-1,2-DCEcis-1,2-dichlorethene
VCVinyl chloride
EtheneEthane
Cl
HC=C
Cl
ClCl
HC=C
Cl
H
Cl
ClC=C
Cl
Cl
Cl
HC=C
H
H
H
HC=C
H
H
Microbiology
© Arcadis 2016
Reductive Dechlorination Pathways
PCETetrachloroethene
TCETrichloroethene
cis-1,2-DCEcis-1,2-dichlorethene
VCVinyl chloride
EtheneEthane
Chlorinated Ethanes1,1,1-TCA1,1,2-TCA
1,1,2,2-TeCA1,2-DCA
Chlorinated Methanes
Carbon TetrachlorideChloroform
Methylene Chloride
MethaneEtheneEthane
Also:• Microaerobic conditions
lead to complete mineralization to CO2
• Abiotic reactions lead to acetylene/etheneendpoint
Microbiology
© Arcadis 2016
Enhanced Reductive Dechlorination Redox Conditions
Hydrogen is the primary electron donor for reductive dechlorination
Oxic
Sub-oxicAnaerobic
Sulfidic
Methanogenic
O2
H2ONO3
-
N2MnO2
SO42-
Fe(OH)3
Fe2+
Mn2+
H2SCO2
CH4
H2
H2O
Aerobes
Conditions for chlorinated ethene dechlorination
Decreasing redoxpotential
Microbiology
© Arcadis 2016
Fermentation Reactions
Hydrogen produced through the fermentation of organic carbon substrate
Microbiology
Higher fatty acidsAlcohols
Etc.
H2, CO2 Acetate
Carbohydrates (sugars)
Methane
Fermentation
Methanogenesis
© Arcadis 2016
Anaerobic Bioremediation Substrates
Gaseous
Slurry/Emulsion phases
Solid
Liquid:Water soluble
Liquid: Limited water solubility
Pure Hydrogen
MethanolEthanol
Molasses
Corn Syrup
Powdered Cheese Whey
Hydrogen Release Compound Vegetable Oil
Emulsified Vegetable Oil
Fresh Cheese Whey
ChitinBark Mulch
Peat
Rapid Acting/Quickly Consumed
Slow Releasing/ Long Lasting
Half Life (Hours)
Half Life (Days)
Lactate
Half Life (Years)
Half Life (Months)
• All produce hydrogen
• Some will be consumed faster than others
Design
© Arcadis 2016
Achieving Adequate Reagent DistributionSoluble Substrate Design
2inj inj mVol h r= π ⋅ ⋅ ⋅ θ
Need additional volume for EVO to overcome straining (15-20% more volume)
EVO Substrate Design
WATERROI
EVOROI
GW
Design
Injected substrate
ROI
GW
© Arcadis 2016
Achieving Adequate Residence Time
Carbon Footprint = IRZ
Soluble Substrate Design
Injected substrate
ROI
GW
Residence Time within IRZ(100 days)
TOC
Minimum DOC(e.g. 30 mg/L at site with background at 10 mg/L)
Injection concentration determined from substrate degradation rate, minimum DOC requirement and residence time
Design
© Arcadis 2016
Achieving Adequate Residence Time
Carbon Footprint = IRZ
Soluble Substrate Design
Injected substrate
ROI
EVO Substrate Design
WATERROI
EVOROI
•Length depends on groundwater velocity & injected ROI
Design Residence Time (100 days)
Reactive Zone within EVO ROI
GW
GW
Second barrier may be requiredResidence Time within IRZ
(100 days)
TOC
Design
•May need multiple barriers to achieve necessary residence time
© Arcadis 2016
• Reduced re-injection frequency• Guided by TOC decline and
soybean oil consumption
Sustaining IRZ: Re-injection Frequency
Re-injections guided by performance monitoring data
IRZ
Soluble Substrate Design
Injected substrate
ROI
EVO Substrate Design
WATERROI
EVOROI
IRZ
GW
GW
• Re-injection is a function of reagent degradation rate and velocity
• Routine injections conducted to sustain TOC over time
Design
© Arcadis 2016
Injection Barrier Spacing
IRZ Flushing Zone
Distance?
(based on total porosity)
Distance = (Desired Timeframe x Groundwater Velocity)/NPV
• Calculate Number of Pore Flushes to reach Treatment Objective:
−=
oPV C
CRN ln
Design
• Where: – NPV = Number of pore flushes– R = retardation factor due to sorption– C = targeted treatment concentration for
respective compound (mg/L)– Co = initial aqueous concentration (mg/L)IRZ
IRZIRZ
Flushing Zone
Flushing Zone
Flushing Zone
© Arcadis 2016
Define the Monitoring NetworkAdequate positioning is needed for optimal
performance and operational monitoring
60 to 120 days downgradient- Optimal treatment information- Demonstrates carbon transport
Immediate dose response during injection
Edge of injection radius to confirm distribution
Adaptive Management
© Arcadis 2016
Develop a Primary Decision Making Data Set
Data Discipline: collect only reliable data that can be used for decision making
Baseline Analysis:
Primary operational variables+
supplemental analyses(Fe2+, NO3
-, SO42-, alk., etc)
pH
TOC
CH4
VOCs
Remedial system design
Operational monitoring: primary variables only
Adaptive Management
© Arcadis 2016
At-a-Glance (AAG) Operational Analysis
pH• 6.2 – 8 S.U. is optimal• 5 – 9 S.U. is acceptable
VOCs and end products• Tracked in molar units• Evidence of complete treatment
TOC – target > 100 mg/LCH4 – look for increase (> 1 mg/L)
Adaptive Management
© Arcadis 2016
Additional Key Operational Considerations
Parameter Key Observations Management Solution
Secondary water quality
• Metals mobilization (Fe, Mn, As)• Gas generation• Injection well biofouling
• Regulatory communication• Monitoring demonstration
Methane • Evaluate during proposal• Include contingency
• Arcadis methane management protocol
Bioaugmentation• No evidence of complete
dechlorination pathway• Limited/slow dechlorination rates
• Confirm TOC presence• Deliver consortia concurrent with
injection
Adaptive Management
© Arcadis 2016
… and now some examples
© Arcadis 2016
Downey, CA
1Q11
Baseline
1Q12
Lubbock, TX
2004 2006
2008 2012
In-Situ Biological Oxidation
© Arcadis 2016
Biological Oxidation- Microbiology
COC = Electron Donors
Reagents = Electron Acceptors (Oxidants)
Aerobic Anaerobic
COC = Electron Donors
Electron Acceptors (Oxidants)• Anaerobic- sulfate, nitrate
• Most thermodynamically favorable fast rates• IRZ limited to injection zone
• Increased kinetics with sulfate addition• Ambient- 1st order, 10s to 100s mg/L• Engineered- zero order, 1,000s mg/L
• Treatment zone can migrate beyond radius of influence
• Petroleum hydrocarbons• MTBE
• Petroleum hydrocarbons• MTBE• Lesser chlorinated organics
• Aerobic- O2, O3, H2O2, ORM
© Arcadis 2016
Biological Oxidation StoichiometryStoichiometry (Benzene Example)
Effective Concentration in Water (mg/L)
PotentialMax Benzene Degraded (mg/L)
Potential Complications
Oxygen (ambientair sources)
C6H6 + 7.5 O2 6 CO2 + 3 H2O
0.33 g benzene/g oxygen
9-10 3.0-3.3 • Limited solubility• Numerous non-target
scavengers• Potential clogging through
biofouling and iron precipitation
Oxygen(pure)
60-70 19.8-23.1
Sulfate C6H6 + 3.75 SO42- + 10.125 H2O
→ 3.75 S2-+ 6 CO2
0.22 g benzene/ g sulfate
70,000 (Na2SO4)
250,000 (MgSO4)
9,000
25,000
• Secondary MCL for sulfate –250 mg/L
• H2S: rarely documented as issue in field
(Adapted from Cunningham et al, 2001)• These are examples• Nitrate is another common oxidant
© Arcadis 2016
Targets of Aerobic Oxidants
*Note that there will be TDC remaining when the site achieves compliance
PetroleumHydrocarbons
(all forms)
Degradable(Natural)OrganicMatter
Other Degradable
Contaminants(oxygenates)
Reduced Inorganics(Fe2+, etc)
(as C)
Total Degradable Carbon
© Arcadis 2016
Oxygen Demand Development in an Anaerobic System0.20
0.15
0.10
0.05
0
pO2 = 0.20 atm
pO2 = 0.00 atm
Soil
Che
mic
al O
xyge
n D
eman
dSoi
l Oxy
gen
Parti
al P
ress
ure,
pO
2
Oxygen depletion due to chemical oxygen demand
O2 depletion during initial shutdown due to chemical oxygen demand and biological activity
Rate of metabolic O2 depletion increases after microbial populations grow to “steady-state” levels
Air Inject Air InjectOff OffAir Inject
Off
Lag-time in free O2 due to oxidation of reactive, reduced ions
Fe2+ Fe3+
Mn2+ MnO2NO2- NO3
-
SO32- SO4
2-
H2S S(s)
© Arcadis 2016
Anaerobic Biological Oxidation Design Basis
CSM Requirements
DesignConsiderations
• Estimate contaminant mass and stoichiometric electron acceptor payload to estimate cleanup timeframe
• Sulfate utilization effective half-life (10 – 20 days @15 C)• Delivery focused on sustained electron acceptor availability
(6-12 months BTEX)
• No drainable NAPL• Target mass present in saturated zone• Mutliple lines of biogeochemical evidence of intrinsic
occurrence
© Arcadis 2016
How can we apply ABOx?
INCREASED COST
SOLID SULFATE LAND APPLICATION
SULFATE BATCH WELL INJECTION
GROUNDWATER RECIRCULATION AND
SULFATE DOSING
Other:• Using nitrate…• Excavation backfill mixing• Direct push gypsum injection
© Arcadis 2016
Sulfate Land Application
1600 920800 940920800
1.3
580 420
310 410
82
1432
48
8.64.7
0.32
3.45.9
2.23.8 4
0.0023
2.7 2.41.7
4 2.92
4.26.8
271 211119
50.1
12371.7 107
182 276
83.4
61.3 43.9
15.5 17.8
6.1
115
1130464
674
0.001
0.01
0.1
1
10
100
1000
10000
0
4
8
12
16
20
May-10 Aug-10 Nov-10 Feb-11 May-11 Aug-11 Nov-11 Feb-12 May-12 Aug-12 Nov-12 Feb-13 May-13
Mon
thly
Rai
nfal
l (in
ches
)
Benz
ene
(ug/
L), S
ulfa
te (m
g/L)
, Met
hane
(ug/
L)
Methane
Sulfate
Benzene
Hurricane Irene
Gyp
sum
Gyp
sum
Hurricane Sandy
© Arcadis 2016
Injection Well Delivery
© Arcadis 2016
Biovent and Sulfate RecirculationBenzene (5 ug/L)Benzene(50 ug/L)Benzene(500 ug/L)Benzene(1,000 ug/L)Benzene(5,000 ug/L)
Hybrid design remedy• Biovent operation to reduce smear zone mass• Sulfate recirculation for 3 years (15MM gallons treated)
© Arcadis 2016
Learning Objectives Revisited
After attending this session, participants should be able to:Define the keys to successful in-situ bioremediationRecognize the microbial mechanisms of treatment and which are appropriate for a given COCExplain the importance of reagent distribution and residence time for effective in situ treatment
© Arcadis 2016
Arcadis.Improving quality of life.