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Treatment Wetlands: The Role of Emergent Vegetation

Treatment Wetlands: The Role of Emergent Vegetation. Treatment Wetlands :. The Role of Emergent Vegetation. Constructed Wetland. Simulates and uses the same treatment mechanisms as the natural environment Engineered to control substrate, vegetation, hydrology and configuration.

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Treatment Wetlands: The Role of Emergent Vegetation

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  1. Treatment Wetlands: The Role of Emergent Vegetation

  2. Treatment Wetlands : The Role of Emergent Vegetation

  3. Constructed Wetland • Simulates and uses the same treatment mechanisms as the natural environment • Engineered to control substrate, vegetation, hydrology and configuration

  4. Treatment Mechanisms • Filtration and sedimentation • Adsorption by soil colloids and O.M. • Transformation and storage of nutrients and metals • Decomposition • Denitrification • Plant uptake • Antibiotics

  5. Uses for Wetland Treatment Systems • Domestic (On-site systems) • Municipal • Mine leachates • Landfill leachates • Industrial • Agricultural • Non-point source • Urban storm-water runoff

  6. Non-Point Source Pollutants • Sediments • Nutrients (N,P) • Pathogens • Pesticides • Metals • Organic Matter (BOD)

  7. Wetland Ecosystem Functions • Sources • Sinks • Transformers

  8. Treatment of Contaminants • Uptake • Degradation • Transformations

  9. Types of Treatment Wetlands • Surface flow • FWS (Free Water Surface) • Subsurface flow • VSB (Vegetated Submerged Beds) • Vertical flow

  10. Treatment Effectiveness • Loading rate • Detention time • Capacity of the vegetation, microorganisms and substrate to transform pollutants

  11. Components of Wetland Treatment Systems • Water column • Plants • Substrate • Microbial population (aerobic and anaerobic)

  12. The Role of the Soil • A surface area for microbial attachment • A substrate for plant growth • Removal of suspended solids, pathogenic bacteria and viruses by filtration • Precipitation of phosphate by iron, aluminum and calcium

  13. The Role of Microorganisms • Degradation of organic matter (in the oxidized and reduced zones) • Nitrification • Ammonium is oxidized to nitrate in the oxidized zones (rhizosphere) • Denitrification • Nitrate is converted to nitrogen gas in anoxic zones

  14. The Role of Vegetation • Surface stabilization • Attachment surfaces for microorganisms • Filter (increases sedimentation) • Produces organic carbon that supports denitrifiers • Oxygen transport to the rhizosphere

  15. Direct uptake and storage of nutrients • Light attenuation • Insulation • Wildlife habitat • Aesthetics • Soil hydraulic conductivity • Antibiotic exudates

  16. Factors Affecting Vegetation • Hydrology - flooding depth and duration • Substrate and water chemistry • Competition

  17. Selection of Plant Species • Treatment effectiveness • Management characteristics • Ancillary benefits

  18. Frequently Used Genera • Phragmites (Reed) • Typha (Cattail) • Scirpus (Bulrush) • Juncus (Rush) • Carex (Sedge)

  19. Desirable Characteristics for Plants Used in Wetland Treatment Systems • Local ecotype adapted to hydrologic conditions of the CWWT design • Economical to propagate and manage with an available supply of propagules of local origin • Tolerant of high concentrations of nutrients and pollutants

  20. Oxygen transport capability • Ability to assimilate pollutants • Tolerance to adverse climatic conditions • Resistance to pests and diseases • Secretion of microbiocidal exudates • Plants with economic or aesthetic value • Large surface area of roots, stems and leaves

  21. Constructed Wetlands for Treatment of Swine-Lagoon Effluent

  22. Experimental Design3 x 3 factorial Plants Lagoon Effluent Concentration (%) No plants 50 Juncus effusus 75 Scirpus validus 100

  23. Objectives • Determine the effects of swine-lagoon effluent on growth of Juncus effusus and Scirpus validus • Compare evapotranspiration and nutrient removal/storage capacity of vegetated and unvegetated wetland cells

  24. Conclusions • Evapotranspiration from cells with vigorously growing wetland plants is as much as 5 times greater than evaporation from unvegetated cells. • Scirpus validus was more effective than Juncus effusus for wastewater treatment.

  25. Conclusions • Growth of plants was better in 75% strength effluent than in 50% and 100%. • Emergent macrophytes do provide important functional values in treatment wetlands.

  26. Orlando’s 480 hectare Wilderness Park.

  27. Juncuseffusus

  28. Total Evapotranspiration(24 weeks)

  29. Total NH4-N Removal/Storage (lbs/ac)(24 weeks)

  30. Total PO4-P Removal/Storage (lbs/ac)(24 weeks)

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