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nrsc 333 > 6. Biodegradation and Water Pollution > Flashcards

6. Biodegradation and Water Pollution Flashcards

1
Q

Sources of organic pollutants (8)

A
  • domestic waste
  • pulp and paper
  • agriculture
  • food processing
  • mining
  • textile industry
  • chemical, pharmaceutical industries
  • internal combustion engines
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2
Q

Types of organic pollution (11)

A
  • proteins, fats
  • carbohydrates
  • lignin
  • cellulosics
  • chloro-organics
  • dyes, solvents
  • paints, resin, pigments
  • fluorocarbons
  • antibiotics
  • hydrocarbons
  • plastics
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3
Q

Contaminants associated with the chemical industry (7)

A
  • acids
  • alkalis
  • metals
  • solvents
  • phenols
  • organic compounds
  • chlorophenols
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4
Q

Contaminants associated with the petrochemical industry (5)

A
  • hydrocarbons
  • phenols
  • acids
  • alkali
  • asbestos
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5
Q

Contaminants associated with the metal industry (~1 → 7)

A

Metals like:
* Fe
* Cu
* Ni
* Cr
* Zn
* Cd
* Pb

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6
Q

Contaminants associated with the energy industry (4)

A
  • phenols
  • cyanides
  • sulphur compounds
  • coal and coke dust
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7
Q

Contaminants associated with the mineral extraction industry (3)

A
  • metals: Cu, Zn, Pb
  • gas
  • lecheate
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8
Q

Contaminants associated with water supply and sewage (3)

A
  • metals in sludge
  • micro-organisms
  • methane
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9
Q

How many deaths are caused by pollution (1 in how many)?

A

1 in 6 (~17%)

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10
Q

What are the fates of contaminants when they enter the environment (4)?

A
  • water pollution
  • groundwater pollution
  • soil/sediment pollution
  • air pollution
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11
Q

Characteristics that determine a compounds fate (2)

A
  • volatile VS non volatile
  • soluble VS non soluble
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12
Q

What is biomagnification?

A
  • The increase in a pollutant in tissues or organisms at successive levels of a food chain
  • Results in bioaccumulation at higher trophic levels
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13
Q

What is bioaccumulation?

A

The increase in concentration of a compound within an organism compared to the level found in the environment

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14
Q

What is biodegradation?

A

Degradation of a pollutant(s) by a living organisms, usually a microorganism

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15
Q

What is bioremediation?

A

Remediation of a contaminated site by using the biodegradative capacity of biology, usually microbiology

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16
Q

For biodegradation/bioremediation to occur, what are the three essential interactions that need to overlap?

A
  1. The contaminant must be biodegradable
  2. Environment physical/chemical parameters must allow biodegradation
  3. Biodegradive microorganisms must be present and active in the contaminated soil
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17
Q

What are xenobiotic compounds? (2)

A
  • Xenobiotic compounds are compounds alien to existing enzyme systems
  • They are not naturally occurying → man made
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18
Q

Examples of xenobiotic compounds (7)

A
  • DDT
  • 2,4-D
  • Malathion
  • Atrazine
  • Monuron
  • Chlorinated biphenyl (PCB)
  • Trichloroethylene (TCE)
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19
Q

Are xenobiotics really foreign to life?

A
  • No, some can actually be made naturally, albeit in minute quantities
  • It more the concentration of these man made compounds that are foreign to life
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20
Q

Can microbes bioremediate xenobiotic compounds? (3 points)

A
  • If these new xenobiotic compounds are similar to existing natural compounds, microbes might be able to easily switch to metabolism of these new compounds
  • This is bc of the time-scale of microbial evolution that indicates that microbes can — or can evolve/adapt the ability to — degrade almost anything (eventuallt)
  • Basically, we can expect to find microbes able to degrade practically any organic compound, it might just take a long time
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21
Q

What is recalcitrance?

A

A compound is recalcitrant if it is attacked poorly, or not at all, by microbial enzyme systems because of its molecular compelxity

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22
Q

What are some examples of recalcitrance? (6)

A
  • Oligomerization (i.e. cellulose, polystyrene, plastics)
  • Halogen substitution (H replaced by chlorine, fluorine, bromine)
  • Other substitutions: H replaced by nitro-, sulfo-groups
  • Branching (alkylation etc.)
  • Molecules are too large to fit into enzyme pockets containing the catalytic sites
  • Large molecular organic contaminants are more hydrophobic, less water soluble, therefore less bioavailable → i.e., plastics, large molecular weight PAHs
23
Q

Which is biodegradable and which is recalcitrant?
2,4-D VS 2,4,5-T

A
  • Biodegradable: 2,4-D
  • Recalcitrant: 2,4,5-T
24
Q

Which is biodegradable and which is recalcitrant?
Propachlor VS Propham

A
  • Biodegradable: Propham
  • Recalcitrant: Propachlor
25
Q

Which is biodegradable and which is recalcitrant?
Carbaryl VS Aldrin

A
  • Biodegradable: Carbaryl
  • Recalcitrant: Aldrin
26
Q

Which is biodegradable and which is recalcitrant?
Methoxychlor VS DDT

A
  • Biodegradable: Methoxychlor
  • Recalcitrant: DDT
27
Q

Which is biodegradable and which is recalcitrant?
Alkanes VS PAHs

A

Alkanes easier to biodegrade than PAHs

28
Q

What makes an alkane harder to biodegrade?

A

The bigger it is, the harder it is to biodegrade

29
Q

Effect of the number of PAH rings on the difficulty to biodegrade them

A

The more rings there are, the harder the compound will be to biodegrade

30
Q

Where can we look for microbes for biodegradation?

A

Look for biodegrading strains in soils where the previous contamination occured.
* Soil is one environment where we tend to spill pollutants
* In soil (compared to water) pollutants and microbes are easily located
* Once isolate, strains could perhaps be improved via genetic engineering

31
Q

How much do microbes need to degrade before the environment is safe again?

A

Depends on the compound!

32
Q

Is the contaminant bioavailable?

A

Available to biological systems for utilization as energy and C sources or to be biotransformed

33
Q

What are the 6 important environmental parameters that bioremediation of contaminants depend on?

A
  1. Aeration
  2. pH
  3. Temperature
  4. Soil moisture
  5. Soil type
  6. Redox potential
34
Q

Aeration: impact on bioremediation

A
  • O2 is required as both a terminal electron acceptor and a substrate in oxygenase-catalyzed biodegradative reactions
  • O2 is often limiting in soil and aqueous systems. O2 concentration is often the rate-limiting variable in petroleum degradation in soil and of gasoline in groundwater
35
Q

How can we increase aeration? (3)

A

By tilling, adding bulking agents in polluted soils, venting in aquifers

36
Q

Bioremediation under anaerobic conditions (4)

A
  • Biodegradation of organic contaminants under anoxic conditions occurs under denitrifying, methanogenic, sulphate-reducing, and iron-reducing conditions
  • Allows for reductive dechlorination (substitution of Cl with H) reactions
  • Halogenated hydrocarbons act as an alternative electron acceptor
  • Anaerobic degradation in subsoils and aqueous systems can be enhanced by supplying the appropriate electron acceptors
37
Q

pH: impact on bioremediaton(2)

A
  • pH can affect water solubility and sorption of contaminants to soil and sediments
  • microbial activity dependent on pH
  • e.g. bacteria: 6-9 ; yeast: 5-9 ; acidophiles: as low as 1
38
Q

How can we increase pH?

A

Add lime to acid soils to bring up pH

39
Q

Temperature: impact on bioremediation

A
  • Q10 value: a change of 10 degrees Celsius will generally increase or decrease an enzyme’s activity by 2-fold
  • Raising temperatures of contaminated soils (waters) can increase the rate of degradation by increasing microbial activity and solubility of contaminants
40
Q

How can we manipulate temperature?

A
  • Difficult to manipulate in the field except for biopiles, bioreactors
  • Compost Materials - thermophilic biodegradation
41
Q

Soil Moisture Content (%) or Water Content (WC)

A
  • amount of water present in soil
  • expressed as the ratio of dry weight / wet weight
42
Q

Water activity (Aw)

A

Measures the water actually available for microbial use

(Microbes require available water for growth and metabolism)

43
Q

Water Holding Capacity (WHC)

A

Amount of water a soil can holf before becoming saturated

44
Q

Optimal soil moisture for aerobic microbial acitivty (in terms of WHC)

A

60-80%

45
Q

Optimal soil moisture for hydrocarbon degradation (in terms of WHC)

A

30-90%

46
Q

Low soil moisture content (dry soils): impact on bioremediation

A

Makes for a low Aw (water activity), so decreases microbial activity

47
Q

Waterlogged soils (WHC > 100%): Impact on bioremediation

A

Anoxic conditions:(

48
Q

How can we increase soil moisture content?

A

Adding water :D

49
Q

How can we decrease soil moisture content?

A

By drying or amending the soil with agents that bind to free water such as gypsum, or bulking agents such as alfalfa

50
Q

Nutrient supply: impact on bioremediation

A

Rate-limiting nutrients N and P
So if there isn’t enough bioremediation will be slowed/stopped

51
Q

What is adding N and P to contaminated sites called?

A

biostimulation

52
Q

What are the required C:N and C:P ratios?

A
  • C:N = 20:1
  • C:P = 50:1
53
Q

Oleophilic fertilizers

A
  • used in aqueous systems
  • are hydrophobic compounds containing N, P
  • remain associated with oil contaminants

nrsc 333 (23 decks)

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