2. What is bioremediation?
The use of bacteria and fungi and plants to break down or degrade toxic chemical compounds that have accumulated in the environment

3. What are environmental contaminants?
Pollutants
naturally-occurring compounds in the environment that are present in unnaturally high concentrations.
Examples:
crude oil
refined oil
phosphates
heavy metals
Xenobiotics
chemically synthesized compounds that have never occurred in nature.
Examples:
pesticides
herbicides
plastics

4. Early examples of bioremediation
Outhouse→Centralized engineered wastewater treatment systems
Microorganisms oxidize organic waste molecules to carbon dioxide and water
Why do we want to use engineered man-made for this?

5. More recent examples
By 1970s it became apparent that we were polluting the environment faster than the natural microbial processes could degrade the pollutants
Congress established the Environmental Protection Agency
Identified “Superfund Sites” that had priority over other polluted systems for special funding and cleanup in 1980
1 in 5 Americans lives within 3-4 miles of a polluted site treated by the EPA
Not much progress has been made even though $billions has been spent

6. Groundwater contamination
Groundwater constitutes 96% of available freshwater in U.S.
95% of potable water in rural areas of U.S. comes from groundwater
In 1988, EPA confirmed that 26 states had various amounts of 44 different pesticides in their groundwater
Cost of cleanup is in the $ trillions
Issues that are still hotly debated
How clean is clean?

8. Most recent
National Institute of Environmental Health Sciences established the Environmental Genome Project
Study impact of environmental chemicals on human disease
Identify genes and their products that are sensitive to toxic chemicals in the environment
Identify genes that encode for products that detoxify the chemicals

9. What types of treatment technologies are in use to remove contaminants from the environment?
Soil vapor extraction
air sparging
bioremediation
thermal desorption
soil washing
chemical dehalogenation
soil extraction
in situ soil flushing

10. What Makes Bioremediation a Promising Approach?
permanence
contaminant is degraded
potentially low cost
60-90% less than other technologies

11. Economics of in-situ vs. ex-situ remediation of contaminated soils
Cost of treating contaminated soil in place $80-$100 per ton
Cost of excavating and trucking contaminated soil off for incineration is $400 per ton.
Over 90% of the chemical substances classified as hazardous today can be biodegraded.

12. Contaminants Potentially Amenable to Bioremediation ____________________________________________

13. What challenges exist for bioremediation of pollutants and xenobiotics?
may exist at high, toxic concentrations
degradation may depend on another nutrient that is in limiting supply
Xenobiotics
microbes may not yet have evolved biochemical pathways to degrade compounds
may require a consortium of microbial populations

14. Fundamentals of cleanup reactions
Aerobic metabolism
Microbes use O2 in their metabolism to degrade contaminants
Anaerobic metabolism
Microbes substitute another chemical for O2 to degrade contaminants
Nitrate, iron, sulfate, carbon dioxide, uranium, technicium, perchlorate

17. ATP Fe(III) CO2 Fe(II) Metabolism of a Pollutant-degrading Bacterium
ACETATE
*U(VI)
*Co(III)
*Cr(VI)
*Se(VI)
*Pb(II)
*Tc(VII)
*Benzoate
*Toluene
*Phenol
*p-Cresol
*Benzene
ATP
CO2
Fe(II)
*CCl4
*Cl-ethenes
*Cl-aromatics
*Nitro-aromatics

18. Uranium reduction leads to uranium precipitation and immobilization
U6+sol
U4+insol

19. Volatile organic compounds (VOC)
These are major contributors to air pollution
Paint industry
Pharmaceutical industry
bakeries
printers
dry cleaners
auto body shops

20. Cometabolism
Bacterium uses some other carbon and energy source to partially degrade contaminant (organic aromatic ring compound)
degradation
products
contaminant
bacterium
corn
starch
CO2 + H2O

21. Hard to degrade contaminants
Chlorinated hydrocarbons
solvents
lubricants
plasticizers
insulators
herbicides and pesticides.

23. Degradation of chlorinated hydrocarbons
Degradation of organic toxins requires the participation of entire biochemical pathways involving many enzymes coded for by many genes.
Some of the genes exist on the chromosome while other genes reside on plasmids.

24. CO2 + H2O
Phenol-degrading dmp operon is regulated by DmpR, a NtrC-like positive regulator.

25. The layout of the genes involved in chlorocatechol-degradation on the plasmid is similar to the layout of the catechol-degrading genes on the chromosome

26. Genetic engineering of bacteria to remove toxic metals from the environment
E. coli bacterium
New gene/transport proteins
Hg2+-metallothein
Hg2+→Hgo
Hg2+
New gene/enzyme
Hgo (less toxic form of metal)

27. Phytoremediation ≈350 plant species naturally take up toxic materials
Sunflowers used to remove radioactive cesium and strontium from Chrenobyl site
Water hyacinths used to remove arsenic from water supplies in Bangladesh, India

29. Phytoremediation Drawbacks
Only surface soil (root zone) can be treated
Cleanup takes several years

30. Transgenic plants Royal Demolition eXplosive Gene from bacterium
moved to
plant genome
Stimulates plant growth!

31. Careers in Bioremediation
Outdoor inspection
Lab testing
Administration
Government
Employee
Regulatory oversight
Company employee

32. Summary
Many factors control biodegradability of a contaminant in the environment
Before attempting to employ bioremediation technology, one needs to conduct a thorough characterization of the environment where the contaminant exists, including the microbiology, geochemistry, mineralogy, geophysics, and hydrology of the system