Bioremediation-From the Lab to the Field

Mitch Lasat, Ph.D.NCER/ORD

1

•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

Presentation Outline

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

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

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

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

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

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

Engineering Strategies for Bioremediation

Intrinsic bioremediation/natural attenuation

Enhanced/engineered bioremediation -addition of nutrients, oxygen

Bioaugmentation -introduction of appropriate organisms

9

Phytoremediation

10

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)

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

11

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

•Bioremediation research I

12

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

13

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