This document discusses bioremediation, which uses microorganisms to reduce pollution. It defines bioremediation and explains that microorganisms degrade contaminants to obtain energy. Certain contaminants like hydrocarbons, chlorinated compounds, and explosives can be amenable to bioremediation through direct metabolism or cometabolism. Factors like the contaminant properties, environmental conditions, and presence of microorganisms can limit bioremediation. Engineering strategies include intrinsic bioremediation, enhanced bioremediation through nutrient addition, and bioaugmentation by introducing organisms. The EPA conducts research on bioremediation technologies to clean up sediments, groundwater and soil contaminated by spills and leaks.

1. Microbial Inorganic chemistry –
Bioremediation uses micro-organisms to
reduce pollution control
Arunamaheswari.C
Assistant Professor
KCG College of Technology

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