In the Netherlands, often only contaminated source locations are remediated, while pollution plumes keep growing as natural conditions do not always support natural (bio) degradation. Gradually, large areas will be (lightly) polluted. Traditional approaches of remediating those plumes are very costly and will cause a lot of CO2-emissions. With an alternative nature-based approach, plume remediation can be achieved in a cost-effective and energy-efficient way, by using constructed wetlands. Such biological groundwater treatment plants could be situated in green public areas. In three cases, results and costs of the implementation of constructed wetlands will be presented. With these project examples we will show that this application is a promising sustainable way of future plume remediation, which can be incorporated in urban groundwater management and other schemes of sustainable land management and land stewardship. The three case studies are briefly introduced below and will be further elucidated in final abstract and presentation.

1. Constructed wetlands for cost-
effective and energy-efficient
remediation of plumes
AquaConSoil, may 2019
Frank Pels (HMVT)
With the cooperation of Nanne Hoekstra (Deltares)

2. Content
1. Constructed wetlands
• what is a constructed wetland?
• Building blocks : transport, design, treatment,
biodegradation;
2. 3 cases
• Amersfoort ; railwaystation
• Doorn ; large contamination plume from a drycleaner
• Zwolle ; interception of multiple plumes from
downtown to protect the public drinking water source

3. Constructed wetlands
A constructed wetland (CW) is an artificial swamp in
which polluted (ground)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

4. Buildingblock (1) –transport
• transport of contaminated water

5. Buildingblock (2) – design
• wetlands are designed specifically for type of pollutant
and necessary flow

6. Buildingblock (3) – treatment
• treatment of contaminants in wetlands
Acknowledgement to KH Kempen

7. Buildingblock (4) – biodegradation
• In the wetland, the pollutants are biodegraded
Anaerobic

8. Buildingblock (5) – energy
• energy can be generated locally

9. 3 cases
1. Amersfoort ; railwaystation
2. Doorn ; large contamination plume from a
drycleaner
3. Zwolle ; interception of multiple plumes form
downtown to protect a the public drinking water
source

10. Amersfoort Railway Site (case 1)
Former welding workshop
from Dutch rail
Birdsview of railyard
Amersfoort
Contamination
ground and
groundwater with
perchloroethylene
(PCE)
+100m

11. Clean up effort(s)
Soil excavation in 2007
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

12. Final design
Designed HRT = 8 weeks

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

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

15. Field test
As built June 2013 Start test September 2013
Autumn 2014 Summer 2016

16. 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

17. 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

18. Relative degradation for PCE
PCE
TCE
DCE
VC
Ethene + Ethane

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

20. 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

21. House Doorn : interception plume (Case 2)
Doorn
National Monument -Refuge where Emperor Wilhelm II spent his last years
after the First World War (1918-1941)

22. Plume originating from dry-cleaner is
intercepted by extraction well for moat

23. With purification plume remedation
Nicole 2018
topview

24. Moat monitoring baseline determination
PCE:
approx 200 - 300 µg/l
Oxygen:
3 - 6 mg/l
DNA for oxidative
VC-degradation
present

25. Construction works finished
Groundwater
Extraction
well
anaerobic zone
aerobic zone

26. current situation

27. AuqaConSoil 2019
Topview Zwolle (case 3)
groundwaterwells
public drinking water
source
contaminated
groundwater below the
city center
interception well and
wetland
Zwolle

28. Het Engelse Werk
Interceptie bemaling
‘Helofytenfilter Zwolle’
Interception
• 1 well, 50-90 m-bgl
• Flow 8m³/u.
• Start construction 2010.
Waterzuivering
• Influent: ca. 20µg/l VC
• wetland
• park: green and sustainable
urban development
• integrated in an urban
environment
energy saving and water saving
• extracted groundwater is used
for cooling and heating a shelter
for homeless people

29. Photo Impression
construction apply sand applying plants
renewable energy purified water infiltration impression

30. Lessons Learned ?
• robust solution for moderate concentrations
• applicable for plumes (multiple sources) under city centers
• low in maintenance
• when changing from anaerobic to aerobic: risk of iron precipitation
• excessive plant growth: mow periodically
• regular site maintenance: tree pruning, Japanese knotweed, etc.
• combination of functions
• in addition to groundwater protection:
• local supply of heat / cold for buildings
• public parks, more attractive urban environment
• bringing natural cooling into an urban environment
• By combining functions you can have multiple sources of financing
A cost-effective solution to prevent that our precious groundwater
goes gray
.

31. Opportunities constructed wetlands in cities
Nicole 2018

32. Partners
Nicole 2018
For more information, contact us:
frank.pels@hmvt.nl & nanne.hoekstra@deltares.nl