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

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Presentation on theme: "The Use of Constructed Wetlands for Treatment of Landfill Leachate and Other Wastewaters Herwig Goldemund, Ph.D. Geosyntec Consultants Atlanta Regional."— Presentation transcript:

1 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 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 Constructed Wetlands

4 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 N 2 reductive dechlorination of chlorinated organics precipitation of metals as sulfides

5 Constructed Wetlands Primary uses –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 Common Reeds (Phragmites) Bulrush (Scirpus) Cattails (Typha) Popular Wetland Plant Species

7 What Do the Plants Actually Do? Maintain voids Provide insulation Provide habitatSome 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

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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 –Oxygen demand (BOD, COD) –Synthetics (volatiles, pesticides) Nutrients (nitrogen, phosphorus) –NH 3 /NH 4 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

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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


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