1. Bioremediation-From the Lab to the Field
Mitch Lasat, Ph.D.
NCER/ORD 1

2. Presentation Outline 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 2

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) 3

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) 4

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 5

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+ 6

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 7

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 8

9. Engineering Strategies for Bioremediation
Intrinsic bioremediation/natural attenuation
Enhanced/engineered bioremediation
-addition of nutrients, oxygen
Bioaugmentation
-introduction of appropriate organisms 9

10. Phytoremediation
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) 10

11. Is bioremediation a “hot” research topic for the EPA?
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 11

12. Bioremediation research I
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 12

13. Bioremediation research II
NCER Bioremediation research:
; several RFAs on Bioremediation and Phytoremediation
- 2001; HSRC program was recompeted, research focus on contaminated
sediments, VOC-contaminated groundwater, mine wastes,
phytoremediation
Case studies/performance data:
- site general information
- contaminants
- site hydrology
- media
- cleanup goals
- technology used
- results/costs
- lessons learned 13