Groundwater Pollution

1
Groundwater Pollution

• Some sample exam questions

2

• 1. You have just started investigations at a
  hazardous waste site and you discover a drum
  nesta pile of old 200 liter drums and other
  debris. A quick check of the pile shows that it
  remains contaminated with organic chemicals. You
  cannot remove the drums and debris until you get
  further into your site cleanup, but you want to
  cover it for now to prevent rainfall from
  infiltrating the waste and spreading contaminants
  to soil and ground water. You may need to keep it
  covered for as long as a year or two. What type
  of liner material would you specify for covering
  the pile?

3

• The cover is only needed for a short time.
• Best would be a flexible membrane liner (some
  type of plastic).
• It must be able to stay in sunlight (UV).
• It must be strong and flexible to cover the
  drums.
• It must be able to stand chemicals.
• Using clay directly on the waste doesnt work
  because it could soak up waste and would need
  further disposal.

4

• 2. What is natural attenuation?
• What happens in natural attenuation?
• People say it is not a do nothing method. What
  do they mean?

5

• Natural attenuation is where there is no human
  action to remediate the pollution. The pollution
  is naturally reduced.
• Monitoring is used to make sure that the
  pollution is being reduced.

6

• 3. An underground leak (at a 3 m depth) at a gas
  station resulted in the loss of several thousands
  of liters of gasoline into subsoil. The gasoline
  then contaminated the ground water that is 4 m
  below the surface.
• Give 2 possible remediation techniques for the
  vadose zone and 2 techniques that could be used
  to clean up the ground water.
• For both the vadose zone and the ground water say
  which one of the two methods you would use and
  also say why you would use them.

7

• Vadose zone dig up the soil and incinerate, or
  wash etc.
• - use soil vapor extraction (SVE) to evaporate
  and remove the gasoline.
• - use bioremediation, adding nutrients, water air
  etc to increase microorganisms.
• If the volume is small use dig and treat, if the
  volume is big use SVE maybe with bioremediation.

8

• Groundwater pump and treat with air stripping.
• - use in-situ bioremediation, adding nutrients,
  air etc to increase microorganisms.
• In-situ bioremediation is cheaper but takes
  longer.

9

• 4. Draw a picture of showing possible groundwater
  contamination with DNAPL.
• What is DNAPL?
• What methods would you use to remediate this
  contamination?

10
A diagram showing the migration of DNAPLs
11

• The liquids with very low solubility are called
  non-aqueous phase liquids (or NAPLs)
• Dense NAPL (DNAPL) is more dense than water. It
  will move down through the groundwater.

12

• Remediation depends on the contaminant.
• eg. - could use sorption barriers
• - add methane, H2 or other electron donor to give
  reductive dechlorination.
• - deep DNAPL pools need to be removed, maybe
  using heat or detergent to flush out the
  pollutant.

13

• 5. Draw a picture of showing possible groundwater
  contamination with LNAPL.
• What is LNAPL?
• What methods would you use to remediate this
  contamination?

14
(No Transcript)
15

• The liquids with very low solubility are called
  non-aqueous phase liquids (or NAPLs)
• Light NAPL (LNAPL) is lighter than water. It will
  float on the groundwater.

16

• Treat the vadose zone and the groundwater.
• Remove the LNAPL from the surface of the
  groundwater, maybe by bioslurping.
• Use sparging, bioremediation, SVE etc.

17

• 6. Draw a picture showing possible groundwater
  contamination with metal.
• What methods would you use to treat this
  contamination?

18
(No Transcript)
19

• Possible treatments
• - Dig and treat
• - Solidification
• - Enclosing in barriers
• - Maybe precipitate with Na2S, or other compounds
• - Use a permeable reactive barrier.

20

• 7. Draw a diagram of the different electron
  acceptor zones of an oil spill.

21
Draw a diagram of the different electron acceptor
zones of an oil spill.
22

• 8. How can some metal oxides be used to remove
  organic contaminants from the soil or
  groundwater?

23

• Organic contaminants can be naturally degraded by
  redox reactions. Mn and Fe-oxides can oxidize
  aromatic pollutants.

24

• 9. What is the first and most important step of a
  typical soil and/or groundwater remediation
  project?

25

• The first and most important step of a typical
  soil and/or groundwater remediation project is to
  find out the extent of contamination.
• Site characterization determines the conditions
  at the site.

26

• 10. The pollution can occur in groundwater in a
  plume. Give three questions that could be asked
  about the contaminant plume.

27

• The questions to ask about the contaminant plume
  are
• Where is the contaminant plume?
• What is in the plume?
• How big is the plume?
• How long has it been there?
• Where is it going?
• How fast will it go?

28

• 11. What is a redox reaction?
• What do we call the chemical which gains
  electrons?
• What do we call the chemical which loses
  electrons?

29

• A redox reaction is a half-reaction of oxidation
  and a half-reaction of reduction.  
• Both half reactions involve the transfer of
  electrons between the chemicals in the system.
• The chemical gaining electrons in the
  half-reaction of reduction is the oxidizing
  agent.
• The chemical which loses electrons in the
  half-reaction of oxidation is the reducing agent.

30

• 12. Describe the difference between attenuation
  of organic compounds and attenuation of metals.

31

• The difference between attenuation of organic
  compounds and attenuation of metals is
• Naturally occurring biodegradation can completely
  convert some organic contaminants to harmless
  products.
• Metals can only be transformed to forms that are
  less mobile or less toxic.

32

• 13. Why arent Pump and Treat systems of
  groundwater remediation be used all the time?

33

• Pump and Treat systems of groundwater
  remediation arent used all the time because they
  are not very successful in removing all
  contaminants.

34

• 14. Describe two different in-situ remediation
  methods.
• Include what contaminant each is used for, what
  are some advantages and disadvantages.

35

• http//www.epa.gov/tio/download/citizens/bioremedi
  ation.pdf
• http//www.epa.gov/tio/download/citizens/chem-deha
  lo.pdf
• http//www.epa.gov/tio/download/citizens/insituflu
  shing.pdf
• http//www.epa.gov/tio/download/citizens/insituthe
  rm.pdf
• http//www.epa.gov/tio/download/citizens/mna.pdf
• http//www.epa.gov/tio/download/citizens/citprb.pd
  f
• http//www.epa.gov/tio/download/citizens/citphyto.
  pdf
• http//www.epa.gov/tio/download/citizens/citsve.pd
  f

36

• 15. Describe two different ex-situ remediation
  methods.
• Include what contaminant each is used for, what
  are some advantages and disadvantages.

37

• See handout

38

• 16. How can some metal oxides be used to remove
  organic contaminants from the soil or
  groundwater?

39

• Organic contaminants can be naturally degraded by
  redox reactions. Mn and Fe-oxides can oxidize
  aromatic pollutants.
• Another example

40

• 17. How does sorption affect the movement of
  contaminants through the groundwater?

41

• Sorption is the attraction of an aqueous chemical
  to the surface of a solid. It involves bonding
  between the contaminant and adsorption receptor
  sites on the solid.
• Sorption slows the traveling of contaminants
  though the groundwater.
• Adsorption is the attraction between the outer
  surface of a solid particle and a contaminant.
• Absorption is the uptake of the contaminant into
  the physical structure of the solid.

42

• 18. Draw a diagram showing how a reactive barrier
  works.
• What are some pollutants which can be treated
  with a reactive barrier?

43

• ABIOTIC AND BIOLOGICALLY MEDIATED ABIOTIC
  ATTENUATION METHODS
• REACTIVE BARRIERS

example
44

• 19. What is bioaugmentation?
• Give an example

45

• Bioaugmentation involves seeding aquifers with
  microorganisms.
• For example, adding halorespiring microorganisms
  in anaerobic plumes that contain electron donors
  and chlorinated solvents.
• The microorganisms should spread and grow and
  increase the natural attenuation capacity.