Organic pollutants: Bioremediation

Question 1

What is surface soil called when it comes to bioremediation?

Answer 1

Efficient and robust biogeochemical filter

Question 2

What happens to organic pollutants as they travel through the soil and into groundwater?

Answer 2

Topsoil:
↓↓↓↓↓ OC & OP
→ Extracellular degradation
→ Mobile OC

↓↓↓↓ OC & OP
→ Adsorption & biodregradation
→ ↓ vertical transport

Subsoil:
↓↓↓ OC & OP
↓↓ OC & OP
↓ OC & OP
→ Very little OC & OP reached subsoil
→ Groundwater ready for consumption and vertical transport

Question 3

Incomplete biodegradation is caused by:
(8 reasons)

Answer 3

• Appropriate enzym is not present
• Partially degraded molecules are more complex or stable than parent compount
• Too low / high concentrations of OP
• High sorption
• Low solubility
• Level of microbial activity
• Steric hindrance (branching or functional groups)
• Cometabolism

Question 4

What is cometabolism?
(3 answers)

Answer 4

• Not a nutrient or energy source for the microbe
• May only partially break down the pollutant
• Primary function: Side-effect of microbial metabolism
• Pollutant use: Not used for energy or growth
• Enzymes involved: Broad-specificity (can act on structurally similar pollutants; often oxygenases)

Question 5

Difference between nutrients and energy

Answer 5

Nutrients: Building blocks

Energy: Needed to pull building blocks appart and put them together

Question 6

Which biodegradation reaction provide energy for the organism?

Answer 6

Energy sources: Oxidation of organic molecules

Question 7

What is steric hindrance?

Answer 7

Slower degradation because reaction sites are blocked by branching or functional groups.

The hindrance increase as size of functional groups increase

Question 8

How does electrons effect biodegradation?

Answer 8

↑ electron density at reaction site
↑ biodegradation rates

↓ electron density at reaction site
↓ biodegradation rates

Question 9

Appart from steric hindrance, how can functional groups affect biodegradation?

Answer 9

Functional groups can be:
- electron donating (CH3), or;
- electron-withdrawing (Cl)

Affecting electron density of the reaction site.

Question 10

How does very low contaminant concentration affect biodegradation?

Answer 10

No enzyme activation

Question 11

How does low contaminant concentration affect biodegradation?

Answer 11

Slow degradation:

Enzyme activation
But no energy generated → No growth

Question 12

How does medium contaminant concentration affect biodegradation?

Answer 12

• Growth
• Energy production
• Good degradation

Question 13

How does high contaminant concentration affect biodegradation?

Answer 13

Less rapid degradation

High toxicity

Question 14

How does solubility and sorption affect biodegradation?

Answer 14

To be degraded, a comound needs to be:

• Physically available, so contact with enzyme is possible
• Dissolved in water
• Dispersed into “tiny droplets” in water phase

Question 15

Which are electron donors/acceptors?

Answer 15

Donors:
Organic matter
Organic pollutants

Acceptors:
Non-organic compounds

Question 16

Which are electron acceptors?

Question 17

The redox-ladder

Answer 17

O₂ + 4e⁻ → H₂O

NO₃⁻ + 10e⁻ → N₂

Mn⁴⁺ + 2e⁻ → Mn²⁺

Fe³⁺ + e⁻ → Fe²⁺

SO₄²⁻ + 8e⁻ → S²⁻

Cl in organics + 2e⁻ → dechlorinated product

OM + 8e⁻ → CH₄

Question 18

What is it called when these are used as electron acceptor?

Oxygen
Nitrogen
Organic matter

Answer 18

• Aerobic respiration
• Denitrification
• Methanogenesis

Question 19

The order for balancing out a chemical equation

Answer 19

• Redoxs element
• Oxygen/water
• Proton
• Electrons

Question 20

Two names for reduction of Cl containing compounds

Answer 20

• Reductive dechlorination
• Dehalogenation