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Reclamation of Contaminated Land 5 > Options Appraisal > Flashcards

Options Appraisal Flashcards

1
Q

What are the 4 primary types of remediation?

A

Physical
Biological
Chemical
Civil Engineering

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2
Q

Why are contaminants harder to remove from fine-grained soils?

A

Electrostatics mean that contaminants bond more readily to fine particles

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3
Q

What are the 3 most significant factors when choosing initial options?

A

Type of contaminant
Acceptable outcome
Location of treatment

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4
Q

How is a conceptual site model used in options appraisal?

A

Potential options are mapped onto the CSM with indications of how they will break pollutant linkges

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5
Q

How is a decision matrix constructed and used?

A

Create and explain decision criteria
Weight criteria based on their relative importance
Score each option based on its performance in the criteria
Sum the weighted scores and compare

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6
Q

What does it mean for an option to be sustainable?

A

It is environmentally, socially and economically sustainable

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7
Q

How can a conceptual site model be changed during options appraisal?

A

The CSM can be reduced if certain features of it are thought to be insignificant

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8
Q

What regulations affect the selection of options?

A

WHO safe levels of contaminants
SEPA safe levels
Regulations around handling of radioactive material
Protection status of the site and adjacent land

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9
Q

What should always be included in an options appraisal?

A

Managed Attenuation/ Doing Nothing

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10
Q

In what 2 ways can contaminants be inhaled?

A

As gaseous vapours
As disturbed fine dust

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11
Q

Why are gas exposures a risk for houses with basements?

A

The pressure difference in the basement can draw gases in

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12
Q

What are the conditions for aquifers being considered ‘receptors of note’?

A

They are already notably polluted
They are used for water abstraction

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13
Q

What should be included in the strategy of a potential option?

A

The means by which it will be carried out consistently

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14
Q

What is Bioaugmentation?

A

Moving microbes of proven efficacy on one site to another site with similar contaminants

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15
Q

Why is biostimulation preferred to bioaugmentation?

A

It is preferred to use microbes which are already present at a site over importing microbes

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16
Q

Why is enrichment a proof of natural attenuation?

A

C13 carbon reacts slower than C12 carbon, so an increase in the ratio of C13 to C12 shows that the carbon is reacting to more stable forms

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17
Q

How is verification structured?

A

In 2 stages: The plan, carried out before remediation, and the report, carried out after

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18
Q

Aside from proving the efficacy of a treatment, what can verification help with?

A

Identifying cost savings
Demonstrating the sustainability of the techniques

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19
Q

What must a successful verification include?

A

Lines of evidence to prove the treatment efficacy
A proof that the option objectives were met

20
Q

How can you test the accuracy of verification techniques?

A

Comparing them to surrogate (artificially contaminated) soil

21
Q

What must be considered at the end of a verification report?

A

Provisions for the potential of the land to be recontaminated, or for immobilised contaminants to become mobile again

22
Q

Why is the format of a verification report important?

A

It must be easily understood by laymen with the remediation target clearly presented

23
Q

What are the 4 categories of groundwater contaminant remediation?

A

Containment
Extraction
Injection
Reactive Barriers

24
Q

Why are pumping treatments a poor choice in permeable, cohesionless soil?

A

Pumping will destabilise the soil leading to localised collapse

25
Q

If permanent groundwater control or excavation is required in an area of unstable soil, what techniques can be employed to maintain stability?

A

Grouting
Sheet Piles

26
Q

How does Air Sparging work?

A

Uncontaminated air is injected into the saturated zone to encourage the vaporisation of in-situ hydrocarbons which can be vented out

27
Q

When should Air Sparging NOT be used?

A

Free product is present
Basements or sewers are in close proximity
The contaminated aquifer is confined

28
Q

How does Soil Flushing affect the local groundwater?

A

The water table is raised near the injection well and lowered at the extraction well

29
Q

In what type of soil is Soil Flushing suitable?

A

High permeability
Low clay and silt

30
Q

How can removal of DNAPLs be expediated?

A

Enhancing the treatment with the injection of surfactants

31
Q

What type of chemical additive can be used to remove metal contamination from soils?

A

Chelating agents form the metals into stable, soluble complexes

32
Q

How are permeable reactive barriers designed to maximise treatment?

A

The barrier is more permeable than the surrounding aquifer material to encourage throughflow

33
Q

When is in-situ chemical oxidation used?

A

To reduce contaminant mass and concentration
To encourage contaminant flux in pump-and-treat systems
To reduce clean-up times for MNA and other methods

34
Q

What are the 4 most common oxidising agents?

A

Permanganate
Catalysed Hydrogen Peroxide
Ozone
Persulfate

35
Q

How do MnO4- and H2O2 compare as oxidising agents?

A

Permanganate (MnO4-) persists longer and so is better for longer term or wider spread applications

36
Q

What types of contaminants can be treated by oxidation?

A

Organic contaminants

37
Q

What types of contaminants can be treated by bioremediation?

A

Organic contaminants

38
Q

When is capping used?

A

To prevent contact with the contaminants
To reduce precipitation infiltration and associated mobilising of contaminants

39
Q

When is stabilisation/solidification unsuitable?

A

When contaminants include anions like Chromium 6 or arsenic, mercury or a mix of varied waste such as metals and volatile organics
When contamination is at significant depth

40
Q

What is the name for forming the soil into a glass-like substance?

A

Vitrification

41
Q

What limits the scale of vitrification treatment?

A

Volume (max 1000 tons per melt)
Depth (only soil close to the surface)

42
Q

Why is soil washing often used in combination with other technologies?

A

Soil washing separates coarse and fine grains, reducing the treatment volume but not directly providing treatment

43
Q

How does soil vapour extraction affect soil biological activity?

A

Vaporising contaminants causes bio stimulation

44
Q

Why is simultaneous extraction of water and vapour useful for treating LNAPL spills?

A

Removing water lowers the groundwater level, exposing more of the soil for vapour extraction

45
Q

How can organics be desorbed from soils in-situ without decomposing them?

A

Heating the soil to temperatures between 100 and 400^C

46
Q

When are electrokinetic treatments employed?

A

When the soil is too low-permeability for soil flushing or other similar mobilisation strategies

Reclamation of Contaminated Land 5 (3 decks)

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