1. Herwig Goldemund, Ph.D. Geosyntec Consultants Atlanta Regional Office
The Use of Constructed Wetlands for Treatment of Landfill Leachate and Other Wastewaters
Herwig Goldemund, Ph.D.
Geosyntec Consultants
Atlanta Regional Office

2. Overview Constructed Wetlands Technology Overview
Types of Wastewater Treated
Pilot Study Results
Leachate Treatment Using Constructed Wetlands
Conclusions
Q&A

3. Constructed Wetlands
Wetlands have a long and successful history in treating a variety of waste streams
Vast experience from 40+ years of research and practical applications throughout the world
Main treatment mechanisms are microbiological processes mediated by plants

4. Constructed Wetlands Plant uptake plays a minor role
Redox conditions can be manipulated to facilitate certain processes
aerobic processes
nitrification of ammonia
aerobic biodegradation of organics (including many contaminants)
precipitation of metals as carbonates, oxides and hydroxides
anaerobic processes
denitrification of nitrate to N2
reductive dechlorination of chlorinated organics
precipitation of metals as sulfides

5. Constructed Wetlands Primary uses Low cost, simple
effluent polishing in advanced treatment systems
treating mild leachate from older sites
treating contaminated groundwater
Low cost, simple
Very low maintenance or even self-regulating
Environmentally friendly
Robust (plants are hardy)

6. Popular Wetland Plant Species
Common Reeds (Phragmites) Bulrush (Scirpus) Cattails (Typha)

7. What Do the Plants Actually Do?
Maintain voids Provide insulation Provide habitat Some uptake

8. Types of Constructed Wetlands
Two main wetland types
Surface-flow wetland
Subsurface-flow wetlands
Two types within subsurface-flow wetlands
Horizontal flow
Vertical flow

9. Traditional Surface Flow Wetlands
Mimics natural wetland systems / vegetation cultivated in shallow channels
Wastewater/leachate flows through at low velocity
Potential problems
poor winter performance
requires significant land area
potential for direct contact with wastewater/leachate
mosquitoes, odors

10. Horizontal Sub-Surface Flow Wetlands
Sand or gravel medium supports aquatic plants
Water level maintained below the sand/gravel
Wastewater/leachate flows horizontally
Potential limitations
insufficient aerobic zones to allow for ammonia reduction
plugging of sand media may lead to ‘short circuiting’

11. Vertical Flow Wetlands
Water percolates vertically down through medium
Draws oxygen through the medium
Allows for increased contact between wastewater/leachate, sand and aerobic bacteria = good nitrification and phosphorus removal
Efficient treatment, even in winter
System termed “Wetland Biofilter System” (WBS)

12. WBS Overview
Commercialized constructed wetland system (installed at over 40 sites in North America)
Originally developed by Aqua Treatment Technologies in conjunction with USEPA, Environment Canada, and Ontario Ministry of the Environment (SWAMP)
Geosyntec helped refine and adapt system for leachate treatment
Vertical Flow Wetland System
Small footprint
Treatment throughout the year (can change inflow depth)
Can be above or below grade (even on top of landfill cap)

13. WBS

14. WBS

15. Types of Wastewaters Treated
Waste streams that can be treated in a biological wastewater treatment plant can be treated in constructed wetlands
Agricultural waste streams
Liquids from waste lagoons, leachate from composting facilities and greenhouses, winery wastes, slaughterhouse effluent, etc.

16. Types of Wastewaters Treated
Residential Applications
Sanitary sewage
Contaminated Groundwater
Aerobically and anaerobically degradable contaminants
Municipal/industrial waste streams
Municipal/industrial wastewater
Hazardous waste (listed and/or characteristic) should not be treated (permitting issues), even if it is technically treatable
Landfill leachate

17. Leachate Composition Organics Nutrients (nitrogen, phosphorus)
Oxygen demand (BOD, COD)
Synthetics (volatiles, pesticides)
Nutrients (nitrogen, phosphorus)
NH3/NH4 most problematic
Inorganics
Metals
Anions (chloride, sulfate, alkalinity)
Others
Total suspended solids (TSS)
Total dissolved solids (TDS)

18. Case Study Pilot Project at Active Landfill Site in Southern Alabama
Site recirculates leachate, trucks excess leachate offsite
Goal is to design full-scale system with treated effluent discharged to stormwater pond and subsequently, through NPDES outfall

19. Pilot Study Results

20. Pilot Study Results

21. Pilot Study Results

22. Pilot Study Results

23. Pilot Study Results

24. Pilot Study Results

25. Pilot Study Results

26. Pilot Study Results

27. Pilot Project Conclusions
High treatment efficiencies for ammonia, BOD/COD, iron, TSS, and P
Variability in ammonia concentrations likely due to analytical issues
Some acclimatization of microbes needed
Organic pollutants effectively removed
Chloride (and TDS) removal is limited
has been expected: conservative ion
Arsenic removal about 50-75%
Denitrification quite impressive
Additional carbon source (e.g., compost) may need to be added
Treated effluent appears to meet surface water criteria

28. Overall Conclusions
Good success with constructed wetlands treatment of ammonia, BOD, COD, iron, phosphorous, many VOCs, pesticides, TSS, E. coli, and some trace metals
Challenges include chloride, TDS, high ammonia concentrations, and effective nitrification of several hundred ppm of nitrate
CW costs for leachate treatment
1-3 ¢/gal depending on scale (includes capital cost and O&M over 20-year design life)
Compared to 5-15 ¢/gal for offsite trucking
Can also help minimize POTW surcharges
Costs can be much lower if flow is increased (e.g., contaminated groundwater)

29. Q&A