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Constructed wetlands for costeffective and energy-efficient remediation of plumes

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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.

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Constructed wetlands for costeffective and energy-efficient remediation of plumes

  1. 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. 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. 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. 4. Buildingblock (1) –transport • transport of contaminated water
  5. 5. Buildingblock (2) – design • wetlands are designed specifically for type of pollutant and necessary flow
  6. 6. Buildingblock (3) – treatment • treatment of contaminants in wetlands Acknowledgement to KH Kempen
  7. 7. Buildingblock (4) – biodegradation • In the wetland, the pollutants are biodegraded Anaerobic
  8. 8. Buildingblock (5) – energy • energy can be generated locally
  9. 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. 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. 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. 12. Final design Designed HRT = 8 weeks
  13. 13. Sampling locations influent effluent = monitoring well 1.2 – 1.35 m = monitoring well 1.7 - 2.1 m
  14. 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. 15. Field test As built June 2013 Start test September 2013 Autumn 2014 Summer 2016
  16. 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. 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. 18. Relative degradation for PCE PCE TCE DCE VC Ethene + Ethane
  19. 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. 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. 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. 22. Plume originating from dry-cleaner is intercepted by extraction well for moat
  23. 23. With purification plume remedation Nicole 2018 topview
  24. 24. Moat monitoring baseline determination PCE: approx 200 - 300 µg/l Oxygen: 3 - 6 mg/l DNA for oxidative VC-degradation present
  25. 25. Construction works finished Groundwater Extraction well anaerobic zone aerobic zone
  26. 26. current situation
  27. 27. AuqaConSoil 2019 Topview Zwolle (case 3) groundwaterwells public drinking water source contaminated groundwater below the city center interception well and wetland Zwolle
  28. 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. 29. Photo Impression construction apply sand applying plants renewable energy purified water infiltration impression
  30. 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. 31. Opportunities constructed wetlands in cities Nicole 2018
  32. 32. Partners Nicole 2018 For more information, contact us: frank.pels@hmvt.nl & nanne.hoekstra@deltares.nl

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