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How our precious groundwater goes grey - sources and pathways


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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.

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How our precious groundwater goes grey - sources and pathways

  1. 1. AquaConSoil 21 May 2019 How our precious groundwater goes grey Sources and Pathways Nanne Hoekstra
  2. 2. Localized sources: Historic soil contaminations and recent spills
  3. 3. Example: tar on a former industrial site
  4. 4. Example: Abandoned landfill in peat hole Made visible with geophysical measures (EM31)
  5. 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. 6. Example: Chlorinated solvents Degradation, but conditions in soil often not adequate for complete transformation to harmles products
  7. 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. 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. 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. 10. Contaminant migration is enhanced by perforation of low-permeabe layers
  11. 11. Diffuse sources
  12. 12. Example: Nutrients from manure and fertilizers
  13. 13. Strange things happen in the underground Source: Hans-Peter Broers Hydrogen sulphide hazard
  14. 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. 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. 16. Some infamous herbicides Earlier we had for instance atrazine as herbicide Now we use glyphosate So, what exactly is the progress?
  17. 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. 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. 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. 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