Groundwater is a precious natural resource. Often overlooked to protect and to care for because it is so easy to use, cheap and abundant. However, this is changing: the groundwater is turning grey. The groundwater quality slowly started to be impacted by decades of industrial and agricultural activities. At several water production wells, the quality has dropped below acceptable levels. This means that additional treatment steps are required before the groundwater can be used for industrial processes or drinking water purposes. With significant -financial- consequences for users. In this session we are zooming into the origin of the problem, parties confronted with the problem and solutions. The origin of the problem may be easily summarized as a result of industrial and agricultural activities. Pollution migrates downwards over time, deteriorating the water quality. This is only one part of the story. As awareness on environmental issues evolved in the end of the last century, many successful programs were carried out to protect the groundwater. Soil and groundwater remediation, emissions restrictions, they all contributed to protect the groundwater. However, due to enormous projected future costs, many needed actions were not taken. Policy changes sometimes replaced actual remedial and protection measures, however they did not resolve the problem. And now we realize that our groundwater is going grey. What are the solutions? How can we protect the groundwater and repair the impacts? The classical technological solutions are all their, however we cannot afford them. So we want to conclude with affordable solutions that already exist and can contribute. We look in detail in the development of biological remediation of groundwater based on the constructed wetland methodology. How do they work and what have recent projects learned us? Why are they a viable -financial- solution to treat contaminated groundwater? We present some in-depth know-how that holds a lot of promise for the future.

1. AquaConSoil 21 May 2019
How our precious groundwater goes grey
Sources and Pathways
Nanne Hoekstra

2. Localized sources: Historic soil contaminations and recent spills

3. Example: tar on a former industrial site

4. Example: Abandoned landfill in peat hole
Made visible with geophysical measures (EM31)

5. stagnantbulk
preferentialchannel
Fast migration
of contaminants
Fast biodegradation
of contaminants
High concentrations of contaminants
Immobile?
Conceptual model valid for both saturated and unsatured waste disposal sites?
How landfills exactly behave as sources of groundwater
contaminants is still subject of research

6. Example: Chlorinated solvents
Degradation,
but conditions in soil
often not adequate for
complete transformation
to harmles products

7. Example: Oil
Degradation in soil,
but often not sufficient for
complete removal
Example degradation of benzene
By oxygen:
C6H6 + 7.5 O2 → 6 CO2+ 3 H2O
By nitrate:
C6H6 + 6 NO3
-+ 6 H + → 6 CO2 + 6H2O + 3N2
By iron:
C6H6 + 30 Fe(OH)3+ 60H + → 6CO2 + 78 H2O + 30 Fe2+
By sulphate:
C6H6 + 3.75 SO4
2-+ 7.5 H+ → 6CO2 + 3H2O + 3.75 H2S
Methanogenesis:
C6H6 + 4.5 H2O → 2.25 CO2 + 3.75 CH4

8. Example: ‘New’ compounds
PFOA perfluoro-octanoic acid
PFOS perfluoro-octanesulfonate
Replacement GenX compounds, e.g.
2,3,3,3-tetrafluoro-2-
(heptafluoropropoxy)propanoic acid
Used for
Fire-fighting
Foam
And
Teflon

9. Areal groundwater management does not necessarily help
Holocene
tussenzandlaag
Holocene
kleilaag
Holocene klei/veen laag
Eerste watervoerende pakket
Terrein bedrijf A Terrein bedrijf B
Vlek A Vlek B
Holocene
tussenzandlaag
Holocene
kleilaag
Holocene klei/veen laag
Eerste watervoerende pakket
Terrein bedrijf A Terrein bedrijf B
Vlek A Vlek B
Outside the
megasite
Compa
ny A
Compa
ny B
Only when it includes
trend reversal measures
based on degradation
process monitoring

10. Contaminant migration is enhanced by
perforation of low-permeabe layers

11. Diffuse sources

12. Example: Nutrients from manure and fertilizers

13. Strange things happen in the underground
Source:
Hans-Peter Broers
Hydrogen sulphide hazard

14. Example: Pesticides
Type Action
Algicides Control algae in lakes, canals, swimming pools, water tanks, and other sites
Antifouling agents Kill or repel organisms that attach to underwater surfaces, such as boat bottoms
Antimicrobials Kill microorganisms (such as bacteria and viruses)
Attractants
Attract pests (for example, to lure an insect or rodent to a trap). (However, food is
not considered a pesticide when used as an attractant.)
Biopesticides
Biopesticides are certain types of pesticides derived from such natural materials as
animals, plants, bacteria, and certain minerals
Biocides Kill microorganisms
Disinfectants and sanitizers Kill or inactivate disease-producing microorganisms on inanimate objects
Fungicides Kill fungi (including blights, mildews, molds, and rusts)
Fumigants Produce gas or vapor intended to destroy pests in buildings or soil
Herbicides Kill weeds and other plants that grow where they are not wanted
Insecticides Kill insects and other arthropods
Miticides Kill mites that feed on plants and animals
Microbial pesticides
Microorganisms that kill, inhibit, or out compete pests, including insects or other
microorganisms
Molluscicides Kill snails and slugs
Nematicides Kill nematodes (microscopic, worm-like organisms that feed on plant roots)
Ovicides Kill eggs of insects and mites
Pheromones Biochemicals used to disrupt the mating behavior of insects
Repellents Repel pests, including insects (such as mosquitoes) and birds
Rodenticides Control mice and other rodents
Source: Wikipedia

15. Some infamous insecticides
In the past we used DDT against insects,
and in the fields of Jan Dirk van de Voort
in Lunteren it is still there,
after 30 year of organic farming…
Now we have neonicotionoids, like
imidacloprid

16. Some infamous herbicides
Earlier we had for instance atrazine
as herbicide
Now we use glyphosate
So, what exactly is the progress?

17. Example: Everything that goes down the sewer, through the
treatment plant and via surface water into the soil
• Medicines
• Antibiotics
• Hormones
• Microplastics (from the
washing machine)
• Teflon (from the dish washer)
• Etc.

18. Migration from diffuse sources
Calculated vertical migration by rain infiltration after 60 and 200 years; and via surface water infiltration after 200 years

19. Contaminants have spread widely and deeply already
Groundwater < 60 years old is affected by nitrate, sulfate, Ni, H2S, antibiotics, pesticides
and more compounds that are penetrating further en further
Aquitards protect old groundwater resources, hopefully
Source:
Hans-Peter Broers

20. Contaminated surface water
Soil contamination
ATES systems
Upper aquifer
Deeper aquifer
Migration after years
Migration after decades
Vertical / horizontal groundwater flow
Groundwater extractions
Purifying con-
structed wetland
Summary and Continuation
In NL: ¾ contaminated, ½ of
drinking water wells influenced
Still, there is
something
we can do!
Taking away the sources
helps a lot, but is no
solution for what is
already in the soil
Could
help
also:
see next
session
in
Gorilla 5