1) Constructed wetlands can effectively remediate contaminated groundwater plumes through natural biological processes at low operational costs. 2) A case study describes a constructed wetland built at an old railway site in Amersfoort, Netherlands, to treat a perchloroethylene (PCE) plume pumped from deep wells. 3) Over time, the wetland fully degraded PCE to ethene and ethane through reductive dechlorination processes aided by straw as a slow release substrate. Tailoring the design to local conditions like weather and contaminant levels was important.

1. Constructed wetlands for cost-
effective and energy-efficient
remediation of plumes
Nicole, June 2018
Frank Pels (HMVT) & Nanne Hoekstra (Deltares)
With the cooperation of Jasperien de Weert, Johan van Leeuwen, Bas
van der Zaan and Jan Gerritse (Deltares)

2. Constructed wetlands
A constructed wetland (CW) is an artificial swamp in
which polluted water is purified
Advantages:
• optimal use of biological processes
• energy-neutral
• fully integrated in the landscape
• low operational costs
• already common practice for waste water treatment, so
experiences can be used for innovative application as
green soil remediation measure
Nicole 2018

3. Buildingblock (1) –transport
• transport of contaminated water
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4. Buildingblock (2) – design
• wetlands are designed specifically for type of pollutant
and necessary flow
Nicole 2018

5. Buildingblock (3) – treatment
• treatment of contaminants in wetlands
Acknowledgement to KH Kempen
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6. Buildingblock (4) – biodegradation
• In the wetland, the pollutants are biodegraded
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Anaerobic

7. Buildingblock (5) – energy
• energy is generated locally
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8. Amersfoort Railway Site
Nicole 2018
Former welding workshop
from Dutch rail
Birdsview of railyard
Amersfoort
Contamination
ground and
groundwater with
perchloroethylene
(PCE)
+100m

9. Clean up effort(s)
Soil excavation in 2007
Nicole2018
Deepwells & pump volumes
Q1 8 -16 m –mv, 2 m3/hour
Q2 6 -16 m –mv, 2 m3/hour
Q3 6 -16 m –mv, 2 m3/hour
Q4 6 -16 m –mv, 8 m3/hour
Pump & treat (P&T)
over period 2009-2011
After 2 years of P&T:
design and construct
wetland

10. Final design
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Designed HRT = 8 weeks

11. Sampling locations
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influent effluent
= monitoring well 1.2 – 1.35 m
= monitoring well 1.7 - 2.1 m

12. Construction wetland
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Placing liner and maintenance drains Building wetland with scoria & straw
Finished wetland with gravel on top Helofytes planted 10 pcs/m2
2m30m
5m

13. Field test
Nicole 2018
As built June 2013 Start test September 2013
Autumn 2014 Summer 2016

14. Wind in relation to water flow
• Influent ranged from 52 to 1198 L/hr. (1.2 - 28.7 m3/day)
• Influent Average = 125 L/hr. (over a period of 19 days)
• Flow and residence time are directly coupled to local wind speed
over time  important to know local weather circumstances
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15. Biochemical conditions
• Over the flow path:
o Redox conditions optimize
o Both organisms capable of
reductive dechlorination and VC-
oxidation develop
• Conditions in winter less suitable
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16. Relative degradation for PCE
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PCE
TCE
DCE
VC
Ethene + Ethane

17. Costs
• Design of wind powered wetland: €15.000,-
• Construction of wetland €35.000,-
• Monitoring & research: €37.500,-
• Maintenance cost: €2.500,-/year
Nicole 2018

18. Conclusions Amersfoort Railway site
• Full PCE dechlorination in wind powered constructed wetland
• Ecological designed concept is self-sustaining
• Added straw as slow release compound provided suitable conditions
for reductive dechlorination
• Tailoring the design to local weather and subsurface conditions is
important (micro organisms; DOC, nitrate/sulphate, wind,
temperature, contaminant concentrations; etc)
• Seasonal variation in wind and temperature affect the system, but it
remains sufficient
• Optimizing flow paths within the wetland, to increase performance
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19. House Doorn : interception plume
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Doorn
National Monument -Refuge where Emperor Wilhelm II spent his last years
after the First World War (1918-1941)

20. Plume originating from dry-cleaner is
intercepted by extraction well for moat
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21. With purification plume remedation
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22. Moat monitoring baseline determination
PCE:
approx 200 - 300 µg/l
Oxygen:
3 - 6 mg/l
DNA for oxidative
VC-degradation
present
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23. Construction works finishd
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Groundwater
Extraction
well
anaerobic zone
aerobic zone

24. Opportunities constructed wetlands in cities
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25. Partners
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For more information, contact us:
frank.pels@hmvt.nl & nanne.hoekstra@deltares.nl