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Geomicrobiology > Bioremediation > Flashcards

Bioremediation Flashcards

1
Q

What is bioremediation?

A

The utilisation of microorganisms to transform contaminants into benign, harmless, and/or less mobile forms.

Aims: Remove, degrade and immobilise contaminant

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2
Q

What are 3 bioremediation strategies?

A
  1. Stimulate natural microbial communities
    - aeration to increase oxygen
    - adding nutrients and PEDs/TEAs
  2. Add surfactants (soaps)
    - Enchance microbial attachment to contaminant
    - Disperse microbes over wide area
  3. Add microorganisms
    - Specifically bred/engineered/selected
    - known as Bioaugmentation
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3
Q

What is in-situ bioremediation?

A

When the contaminant is treated in place.

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4
Q

What are two in-situ bioremediation techniques?

A
  1. Permeable reactive barrier
    - Works with organic and inorganic contaminants
    - Can be with or without microbes
  2. Injection wells
    - Air injected stimulates aerobic organisms
    - Can idealise groundwater conditions for the microorganisms you want to be active
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5
Q

What is ex-situ bioremediation?

A

Pumping out/extracting contaminated materials and treating off-site.

e.g., Pump (extraction wells) and treat, Constructed wetlands, Slurry bioreactors

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6
Q

What are some types of organic contaminants?

A
  • Petroleum hydrocarbons
  • Chlorinated hydrocarbons
  • Plasticisers
  • Solvents
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7
Q

What is the main goal for bioremediating organic contaminants?

A

To degrade the organic contaminant.

Want to oxidise it (use as PED).

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8
Q

What is the main strategy used in organic contaminant bioremediation?

A

Aeration (to stimulate natural microbial communities):

  • Use organic carbon as PED (contaminant)
  • Want aerobic chemoheterotrophs
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9
Q

What does aeration involve in organic contaminant bioremediation?

A

Organic contaminants are degraded (oxidised) fastest via aerobic respiration.
Can either be done by pumping or in-situ.

Bioventing: Adds O2 to vadose zone (unsaturated)
Air Sparging: Adds O2 below water table (saturated)

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10
Q

What can be done to bioremediate organic contaminants if aeration is not feasible?

A
  1. Stimulate anaerobic chemoheterotrophs e.g., Shewanalla
    - Acts as Fe(III)-reducer
  2. Add nutrients and electron shuttles to stimulate anaerobic chemoheterotrophs
    - will speed up reaction as not as thermodynamically favourable
  3. Add surfactants
    - help disperse microorganisms and attach to contaminants
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11
Q

What are natural sources of metals?

A

Rock and minerals

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12
Q

What are anthropogenic sources of metals?

A

Agriculture, mining, sewage, waste

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13
Q

How do terrestrial ecosystem relate to contaminants?

A

Soils are a major sink for metal contaminants.

Contaminants bound to OM and then transported by ground water.

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14
Q

How do aquatic ecosystem relate to contaminants?

A

Sediments are major sink for metal contaminants.
e.g., via runoff, leaching etc.

Mobility and metal toxicity depends on concentration and speciation.

Hard to clean up contaminated GW.

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15
Q

What are the 4 bioremediation strategies for metals?

A
  1. Bioreduction
  2. Biosorption
  3. Bioaccumulation
  4. Biomineralisation
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16
Q

What is the process of bioreduction?

bioremediation of metals

A

Enzymatic reduction of U(6+) to U(4+)

Type of biomineralisation process:

  • stimulate by adding electron donors and increasing the organic carbon.
  • want microbes to use U as TEA
17
Q

What are the problems associated with bioreduction?

bioremediation of metals

A
  • Competition from other TEAs more energetically favourable
  • If stop adding PED, sulphate reduction takes over
  • Too much U can inhibit growth
18
Q

What is the process of biosorption?

bioremediation of metals

A

Uranyl UO22+ cation, U(6+), sorbed to cell (-ve).

  • passive process where the biosorptant (dead or live cells) can be regenerated.
19
Q

What are the problems associated with biosorption?

bioremediation of metals

A
  • Can get fast U desorption from cell
  • Other cations compete for surface sites
  • Cell surfaces quickly saturated
  • Not used for in-situ treatment
20
Q

What is the process of bioaccumulation?

bioremediation of metals

A

UO22+, U(6+), cells uptake contaminant

  • Organisms bioaccumulate U, Cs, Te etc. in low level nuclear waste
  • Not well known how useful it is
21
Q

What is the process of biomineralisation?

(bioremediation of metals) + Problems

A

U(6+) and PO43- compound.
No change in oxidation state (induced biomineralisation)

Problems:
Phosphate is highly reactive and can ppt. quickly with other cations

22
Q

What is the goal at nuclear sites for bioremediating U?

A

Want to prevent uncontrolled dispersion and transport of U in ground water.
Don’t want U in oxidised U6+ form as very mobile.

Geomicrobiology (14 decks)

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