biodegradation petroleum
TRANSCRIPT
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 1/22
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 2/22
Natural vs. Anthropogenic
Domestic waste Herbicides/pesticidesPaper Plastics
Acid mine drainage DetergentsOil Chlorinated solventsMetals
Points of concern:
1. natural vs. anthropogenic
Cl
OH
Cl
O – CH2 - COOH Cl
Cl
There are many different organic contaminants that are spilled into theenvironment.
2. quantity added or spilled
- carrying capacity or self purification
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 3/22
Extent of problem
• 300 million metric tons/yr
• > 1,200 Superfund sites
• Cleanup costs estimated to exceed 1 trillion $
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 4/22
In most cases there are two steps required for biodegradation:
1) uptake and transport of the contaminant into the cell and 2) metabolism.Compounds with low solubility and/or high sorption are not in the aqueous
solution surrounding the cell and therefore their uptake is limited.
Example:
Compound Solubility (mg/L) Biodegradation in 5 days
C7H16 2.93 complete
C16H34 0.0063 ~ 64%
C40H82 very, very low ~ 5%
Factors affecting biodegradability
1. Bioavailability
low water solubilitysorption
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 5/22
A
B
C
D
Hydrocarbon phase
Aqueous phase
How do microbes increase bioavailability in the environment?
A - Uptake of solubilized hydrocarbonB – Uptake of hydrocarbon at the oil-water interfaceC – Uptake of dispersed droplets of oil
D –
Production of biosurfactants to increase the oil-water interfacial area
Scenario –an ocean oil spill
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 6/22
2. Genetic makeup - lack of appropriate degrading genes
Each step in a biodegradation reaction is catalyzed by an enzyme. If theappropriate enzymes are not present, biodegradation will not occur. Sinceeach enzyme is encoded by a gene, the genetic makeup of the microbial
population is a critical factor in determining whether biodegradation willoccur.
3. Contaminant structure (steric hindrance or unusual functional groups)
The presence of the following structures generally inhibit biodegradation
unusual atoms (halogens) R - CH2 - Cl
aromatic ring systems
high molecular weight -(CH2 – CH2 – CH2 – CH2)n-
branching R - C - CH3
CH3
CH3
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 7/22
Increasing biodegradation rate (mg/g sludge dry solids/ hr)
94.8 55.0 55.0 25.0 13.9
COO- CH3 OH Cl NO2
How different substituents influence biodegradation of phenol
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 8/22
2,2,5,5-tetramethylhexane
CH3 - C - CH2 - CH2 - C - CH3
CH3
CH3
CH3
CH3
CH3 – CH2 – CH2 – CH2 – CH2 – CH3
vs.
hexane
Given a pair of structures you should be able to predict which of
the pair will degrade more rapidly.
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 9/22
Benzene
Benzo(a)pyrene
vs.
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 10/22
CH2 - COOH
Cl
Cl
CH2 - COOH
Cl
Cl
Cl
2, 4- D
2, 4, 5 - T
vs.
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 11/22
ethanol
TCE
CH3 - CH2 - OH
C = CH
ClCl
Cl
vs.
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 12/22
4. Environment (biotic and abiotic)
• moisture content (too much limits oxygen availability, too little
inhibits microbial activity in general)
• oxygen (required for rapid biodegradation processes)
• pH (extremes limit microbial activity)
• nutrient availability (includes mineral nutrients and organic matter) • competition (are the microbes of interest active, do added microbes
survive?)
All of these need to be with acceptable ranges to allow optimal
biodegradation activity.
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 13/22
Biodegradation terminology
Transformation - any single biodegradation step in a pathway is a transformationreaction. A transformation can result in partial or complete detoxification of acontaminant or can create a compound even more toxic than the parentcompound.
Mineralization - the parent compound is completely degraded to CO2, new cellmass, and water. This is a highly desirable result for toxic contaminants.
Cl
Cl
N NH - CH
CH 3 CH 3
CH 3 - CH 2 - NH N N
Atrazine transformationproduct is notdegraded further
Cl
Cl
N NH - CH
CH 3
CH 3 N
N H
CH 3 - CH 2 -NH2
+ mineralization
CO2 + cell mass + H2O
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 14/22
Biodegradation terminology (cont.)
Cometabolism - Sometimes an enzyme can act nonspecifically on a
substrate leading to a transformation reaction that does not provideenergy to the microbe. A good example is oxidation of TCE bymethane-utilizing microbes.
lack of enzyme specificity detoxification
OH
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 15/22
Biosynthesis - partial or incomplete degradation can also result inpolymerization or synthesis of compounds more complex and stablethan the parent compound.
Cl NH2 Cl
Cl NH Cl
– C – CH2 – CH3
=
O
Propanil
Abiotic/biotic polymerization Binding to humus
Cl N Cl
Cl = N Cl
Cl N Cl
= N Cl
Cl Cl
N
H
tetrachloroazobenzenedichloroanilino - trichloroazobenzene
– C – CH2 – CH3
= OHO
CO2 + cell mass + H2O
Mineralization
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 16/22
CH3 – (CH2 – CH2 )n – CH3 Aliphatics:
Alicyclics:
Aromatics:
OH
Biodegradation pathways
Most contaminants can be categorized into one of three structure types, allcommonly found in petroleum products. Some contaminants contain a
combination of these structures.
Note to instructors: No actual pathways are presented in this slide show.You will have to decide what pathways (aerobic and anaerobic) you want
to present.
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 17/22
Bioremediation
For successful and cost-effective bioremediation, there need to be degradingmicrobes, adequate bioavailability, and suitable environmental conditions. For
petroleum spills, there are normally degrading microbes present so the issuesbecome bioavailability and environmental conditions.
In ocean oil spills, access to the oil is limited to the surface area between the oil-water interface. In general oxygen is not limiting but as shown below, nitrogenand phosphorus are limiting.
1. oil alone 0
2. oil + microorganisms 53. oil + micro. + P 5-10
4. oil + micro. + N 5-10
5. oil + micro. + N + P 75
Treatment in seawater % biodegradation
From Atlas and Bartha studying degradation constraints in an oil spill:
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 18/22
In the subsurface, the most limiting factor is generally oxygen. Therefore,
addition of oxygen is one of the most common approaches to cleanup ofsubsurface contamination.
In addition, nutrients such as N and P may be added.
In some cases, natural activities are fast enough to control the contaminantplume. This is called intrinsic bioremediation or natural attenuation. This
approach is desirable because it requires only monitoring of the contaminantplume. Must address the questions:
In subsurface terrestrial environments, there are many options. These includeboth in situ and ex situ treatment.
Is intrinsic activity fast enough?
Will the plume impact human or ecological health?
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 19/22
If a more aggressive approach is required, there are several optionsavailable:
In situ treatments
• Bioventing
• Air sparging
• Permeable reactive barriers
Ex situ treatments
• Biofiltration
• Soil vapor extraction and treatment
• Groundwater extraction and treatment
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 20/22
In situ bioremediation in the vadose zone and groundwater. Nutrient andoxygen are being pumped into the contaminated area to promote in situprocesses. Water is being pumped to the surface for ex situ treatment in anaboveground bioreactor. Following treatment, an injection well is returning thecontaminant-free water to the aquifer.
Example 1
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 21/22
Bioventing and biofiltration in the vadose zone. Air is slowly drawn through thecontaminated site (bioventing) which stimulates in situ aerobic degradation.Volatile contaminants removed with the air can be treated biologically using abiofilter as shown or by adsorption on activated carbon, or by combustion.
Example 2
8/12/2019 Biodegradation Petroleum
http://slidepdf.com/reader/full/biodegradation-petroleum 22/22
Bioremediation in groundwater by air sparging. Air is pumped into thecontaminated site to stimulate aerobic biodegradation Volatile contaminantsbrought to the surfaced are treated by biofiltration, activated carbon, orcombustion.
Example 3