Groundwater Remediation Flashcards

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Flashcards related to groundwater remediation.

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35 Terms

1
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What is the formula for the saturation index (SI)?

SI = log(products/Keq)

2
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What does it mean if SI > 0?

Supersaturated conditions

3
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What does it mean if SI = 0?

Equilibrium

4
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What does it mean if SI < 0?

Undersaturated conditions

5
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How does surface area affect the rate of precipitation-dissolution reactions?

Greater surface area leads to a greater reaction rate.

6
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How does the saturation index affect reaction rates?

Rates slow close to saturation.

7
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What does redox potential (Eh) indicate?

A system's tendency to gain or lose electrons.

8
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Low Eh indicates what type of conditions?

Reducing conditions

9
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What is a redox couple?

Pairs of oxidized and reduced species that participate in electron exchange

10
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How do environmental factors influence redox processes?

Oxygen availability and pH influence which redox processes dominate in natural systems.

11
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Name the electron acceptor in denitrification.

NO3- (nitrate), reduced to N2

12
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Name the electron acceptor in aerobic respiration.

O2

13
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Name the electron acceptor in sulfate reduction.

SO42- (sulfate), reduced to H2S (hydrogen sulfide)

14
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What does the Monod equation model?

How microbial reaction rates depend on substrate concentration.

15
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What is Dual Monod kinetics?

Kinetics that account for both electron donor and acceptor availability.

16
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What does a small Damköhler number (Da < 1) imply?

The reaction is slow compared to transport.

17
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What does a large Damköhler number (Da > 100) imply?

The reaction is fast relative to transport, and local equilibrium assumption is valid.

18
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How does Da help in designing remediation systems?

It helps identify the reactive zone length and residence time needed for remediation.

19
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For what type of contaminants do pump and treat systems often work well?

Non-aqueous phase liquids (NAPLs)

20
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What is a Light NAPL (LNAPL)?

A NAPL less dense than water that floats on the water table surface.

21
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What is a Dense NAPL (DNAPL)?

A NAPL more dense than water that is typically more difficult to remediate.

22
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What is the tailing phase in pump and treat systems?

The long period of slow release of contaminants to groundwater.

23
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What is pulsed pumping?

Turning wells off and allowing concentrations to rebound before pumping again.

24
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Define the zone of influence.

The zone around the well.

25
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Define the zone of capture.

The zone within which all water flows to the pumping well.

26
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Define the zone of travel.

An area defined by some chosen travel time (e.g., 10 years).

27
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In anisotropic media, how does hydraulic conductivity vary?

Hydraulic conductivity varies by direction.

28
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How many components does the hydraulic conductivity tensor have in 3D?

9

29
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What is intrinsic bioremediation?

Naturally occurring bioremediation without augmentation.

30
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What is engineered bioremediation?

Bioremediation involving biostimulation from the addition of electron acceptors or substrate.

31
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How do redox conditions affect contaminant degradation?

Redox conditions control which contaminants can be degraded and how fast.

32
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What are key design considerations for PRB systems?

PRB permeability, hydraulic capture, thickness, and lifespan.

33
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What is zero-valent iron (ZVI) used for in PRBs?

To reduce contaminants by supplying an electron donor (Fe0 → Fe2+).

34
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What are the advantages of PRBs?

No active pumping required (low maintenance costs), treats plume in place, minimal above-ground infrastructure.

35
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What are the limitations of PRBs?

Plume depth, ability to only remediate certain contaminants, reliance on natural groundwater flow, and clogging.