Transcript Lecture #3 - Bioremediation

Bioremediation
Hydraulic Fracturing
Why do we even need
it?
• We can’t seem to stop polluting
– Inorganics
• Uranium, technetium, sulfur, sulfuric
acid
– Explosives
• RDX, TNT
– Polyaromatic hydrocarbons
• creosote
– Chlorinated hydrocarbons
• Trichloroethylene, PCBs,
pentachlorophenol
– Petroleum hydrocarbons
• Gas, gas additives (MTBE), diesel
•
From mid-1980’s up to 90’s numerous attempts
were made to design GMO for environmental
release for pollutants and heavy metals
(USGS).
– Failures to program: bacteria doesn’t
behave in a predictable fashion from the
lab.
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
What are environmental
contaminants?
• Pollutants
– naturally-occurring compounds
in the environment that are
present in unnaturally high
concentrations.
• Xenobiotics
– chemically synthesized
compounds that have never
occurred in nature.
– Examples:
– Examples:
•
•
•
•
crude oil
refined oil
phosphates
heavy metals
• pesticides
• herbicides
• plastics
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 2014, EPA confirmed that 42 states
had various amounts of 260 different
pesticides in their groundwater
• Most Polluted States: California,
Wisconsin, Arizona, Florida, North Carolina,
Texas, New York, Nevada, Pennsylvania and
Illinois
Groundwater contamination
• Cost of cleanup is in the $ trillions
• Issues that are still hotly debated
– How clean is clean?
What Makes Bioremediation a Promising
Approach?
• permanence
– contaminant is degraded
• potentially low cost
– 60-90% less than other technologies
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.
Contaminants Potentially Amenable to Bioremediation
____________________________________________
Readily
degradable
____________
_
Somewhat
Difficult to
Generally
degradable
degrade
recalcitrant
_____________ _____________ _____________
fuel oils, gasoline creosote, coal
tars
chlorinated
solvents (TCE)
dioxins
ketones and
alcohols
pentachlorophenol (PCP)
some pesticides
and herbicides
polychlorinated
biphenyls (PCB)
monocyclic
aromatics
bicyclic aromatics
(naphthalene)
What challenges exist for bioremediation of
pollutants and xenobiotics?
• Pollutants
– 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
Phytoremediation
• Drawbacks
– Only surface soil (root zone) can be treated
– Cleanup takes several years
Environmental Consequences of Large Oil Spills
Center rectangular plot (arrow) was
treated with inorganic nutrients to
stimulate bioremediation
Petroleum Biodegradation
•
•
•
Diverse bacteria, fungi, and some
cyanobacteria and green algae can oxidize
petroleum products aerobically
Oil-oxidizing activity is best if temperature
and inorganic nutrient concentrations are
optimal
Hydrocarbon-degrading bacteria attach to
oil droplets and decompose the oil and
dispense the slick