This document discusses bioremediation, including what it is, how it works, contaminants it can treat, limiting factors, engineering strategies, and research being conducted on it by the EPA. Bioremediation uses microorganisms to degrade environmental contaminants and can treat a variety of compounds including hydrocarbons, chlorinated solvents, pesticides, explosives and some metals. Factors like contaminant properties, environmental conditions, and microbial presence can limit its effectiveness. The EPA conducts research to better understand bioremediation and alternative remediation technologies.

1. Bioremediation-From the Lab to the Field
Mitch Lasat, Ph.D.
NCER/ORD
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2. •What is Bioremediation?
•Why Bioremediation works?
•Contaminants amenable to Bioremediation
•Limiting factors (why bioremediation doesn’t work?)
•Engineering strategies for Bioremediation
•Is bioremediation a “hot” research topic for the EPA?
•Bioremediation research
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Presentation Outline

3. What is Bioremediation?
 the use of biota to degrade/mitigate environmental contamination
-bioremediation- by microorganisms (soil, groundwater-organic
contaminants)
-phytoremediation- by plants (mostly soil and surface water)
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4. Why Bioremediation works?
 microorganisms obtain energy for growth by degrading organic contaminants
in an enzyme-mediated process- direct metabolism
-aerobic biodegradation of BTEX in the presence of an oxygenase
(Pseudomonas)
 some enzymes are not very specific and in addition to the growth substrate
transform other compounds-cometabolism
-oxygenases are not very substrate-specific and can also degrade TCE
(however TCE cannot be used as a growth substrate)
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5. Contaminants amenable to Bioremediation I
 Hydrocarbons:
- BTEX (aerobic and anaerobic biodegradation)
- PAH (less amenable)
- aerobic degradation via cometabolism
- anaerobic biodegradation (naphtalene-denitrification)
 Chlorinated Aliphatic Hydrocarbons
- aerobic electron donor (DCM, CM, DCA)
- anaerobic electron donor (TCE, DCE)
- anaerobic acceptor (PCE, TCE)- dehalorespiration
- cometabolism (aerobic, anaerobic-reductive dechlorination)
 Chlorinated aromatic hydrocarbons
- PCB (in general bioremediation recalcitrant)
-aerobic, less chlorinated
-anaerobic (dehalorespiration)
- PCP; aerobic, anaerobic (groundwater-reductive dechlorination)
- Dioxins; highly resistant to Bioremediation
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6. Contaminants amenable to Bioremediation II
Pesticides
-chlorinated; highly resistant to aerobic transformation
-phosphorus based and carbamate; quickly hydrolyzed
-triazine; biodegradable
Explosives
-biotransformation is partial (TNT) or slow (RDX)
Inorganics
-bacterial reduction of Hg2+ to Hg0
-bacterial reduction of Cr6+ to Cr3+
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7. Factors that limit the potential for Bioremediation
(why Bioremediation doesn’t work)
1) Contaminant-related limitations:
 Synthetic vs. natural contaminants
-bioremediation potential greater for natural compounds
 Physical characteristics
-density, Henry’s constant, solubility, octanol/water partition coefficient
 Molecular structure of the contaminant
-extent of chlorination, linear vs. branched structure, saturated vs.
unsaturated compounds
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8. Factors that limit the potential for Bioremediation
(why Bioremediation doesn’t work)
2) Environmental conditions:
Hydrogeology: permeability/hydraulic conductivity, heterogeneity,
fracture bed rocks, soil properties, pH
 Nutrients: C:N:P-100:10:1
Electron acceptor: oxygen (3 parts of oxygen to converts 1 part of
hydrocarbon to CO2), nitrate, sulfate, ferric iron
3) Microorganisms presence:
Assessment of microbial activity, introduced microorganisms
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9. Engineering Strategies for Bioremediation
Intrinsic bioremediation/natural attenuation
Enhanced/engineered bioremediation
-addition of nutrients, oxygen
Bioaugmentation
-introduction of appropriate organisms
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10. Phytoremediation
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 Phytoextraction (removal/extraction of toxic metals- Pb)
 Phytodegradation (organics degradation in roots and shoots-
TPH, PAHs, BTEX, pesticides, CAHs)
 Phytovolatilization (CAHs, Hg, Se)
 Evapotranspiration/Hydraulic control (plume reduction)

11. Is bioremediation a “hot” research topic for the EPA?
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 Cross-agency research advisory workgroup for Goal 3; Bioremediation- a
priority technology for remediation of contaminated sediments,
groundwater and soil
 ORD GOAL 3 MYP-long-term goal oriented with annual progress measured
by completion of APG/APM-of the approximately 70 remediation-related
APMs, approximately half pertain to bioremediation:
- Report on biodegradation of PAHs in sediments
- Report on solvent-enhanced residual biotreatment of residual DNAPL
- Develop and evaluate microbial populations for effective TCE
biodegradation
- Develop and evaluate cost-effective methods for nutrient mixing and
delivery for bioremediation of chlorinated aliphatic hydrocarbons
- Synthesis report on 5 DNAPL remediation technologies

12. •Bioremediation research I
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 ORD’s Goal 3research program is designed to provide a better understanding
of the traditional risk management options (dredging, capping, pump and
treat), and to investigate alternative options (bioremediation, MNA)
 Problem-driven research program, supporting research needs of:
- Office of Solid Waste
- Superfund
- Leaking Underground Storage Tank Corrective Action
- Oil Spills
 Contacts: NPD-Randy Wentsel
NRMRL-Trish Erickson
NCER-Mitch Lasat

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 NCER Bioremediation research:
- 1997-2001; several RFAs on Bioremediation and Phytoremediation
- 2001; HSRC program was recompeted, research focus on contaminated
sediments, VOC-contaminated groundwater, mine wastes,
phytoremediation
http://es.epa.gov/ncer/grants/
 Case studies/performance data:
http://clu-in.org/techfocus/
- site general information
- contaminants
- site hydrology
- media
- cleanup goals
- technology used
- results/costs
- lessons learned
•Bioremediation research II