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Constructed Treatment Wetlands

2. What is a Constructed Wetland? (1/6). Wetlands are transitional areas between water and land. The 1977 Clean Water Act Amendments provide a broad definition of wetlands: "The term 'wetlands' means those areas that are inundated or saturated by surface or groundwater at a frequency and duration s

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Constructed Treatment Wetlands

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    1. 1 Constructed Treatment Wetlands Special Topics on Environmental Engineering (I)

    2. 2 What is a Constructed Wetland? (1/6) Wetlands are transitional areas between water and land. The 1977 Clean Water Act Amendments provide a broad definition of wetlands: "The term 'wetlands' means those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.“ Water, Soil, Vegetation.

    3. 3 What is a Constructed Wetland? (2/6)

    4. 4 What is a Constructed Wetland? (3/6)

    5. 5 What is a Constructed Wetland? (5/6) In brief, a constructed wetland is a water treatment facility. Duplicating the processes occurring in natural wetlands, constructed wetlands are complex, integrated systems in which water, plants, animals, microorganisms and the environment-sun, soil, air-interact to improve water quality. Whereas geology, hydrology and biology create natural wetlands, constructed wetlands are the result of human skill and technology. Humans design, build and operate constructed wetlands to treat wastewater.

    6. 6 What is a Constructed Wetland? (6/6) Advantage of constructed wetlands is that operation and maintenance costs are likely to be less than a conventional treatment plant. Less energy and supplies are needed, and constructed wetland facilities can get by with periodic on-site labor, rather than continuous, full-time attention.

    7. 7 Wetlands: engineers applying natural purifying abilities of wetland systems emulate and enhance for human benefit (possibly for wildlife/nature benefit). What is a Constructed Wetland? (4/6)

    8. 8 Wastewater treatment Traditional environmental engineering:large, centralized facilities are resource and energy intensive solutions to pollution problems Ecological engineering:minimize environmental stress (e.g. effluent discharge with nutrients to water bodies)

    9. 9 How do treatment wetlands work? (1/3)

    10. 10 How do treatment wetlands work? (2/3)

    11. 11 How do treatment wetlands work? (3/3)

    12. 12 Design and Planning Considerations: (1/2)

    13. 13 Design and Planning Considerations: (2/2)

    14. 14

    15. 15 The primary physical and chemical processes: settling, sedimentation sorption Chemical oxidation/ reduction —precipitation photodegradation/ oxidation volatilization

    16. 16 biodegradation and plant uptake are major contributors for contaminant removal: aerobic/anaerobic biodegradation phytoaccumulation/ phytostabilization phytodegradation/ rhizodegradation phytovolatilization/ evapotranspiration

    17. 17 Primary Contaminant Removal Mechanisms

    18. 18 Summary of contaminant removal efficiency in treatment wetlands

    19. 19

    20. 20 Types of constructed wetland systems The two main types :surface flow (SF) and subsurface flow (SSF). SF wetlands require more land than SSF wetlands for the same pollution reduction but are easier and cheaper to design and build. SSF systems are often more efficient but can cost significantly more than equivalent SF wetlands. ( ** however, recent data may show efficiencies are more equitable) SF systems are preferred in the United States ( SF: SSF=2:1 );in Europe the reverse is true.

    21. 21 Surface Flow (SF) Systems

    22. 22 Subsurface Flow (SSF) Systems

    23. 23 Riparian Buffer System (1/2)

    24. 24 Riparian Buffer System (2/2)

    25. 25 Constructed Wetland at Gao-Ping River, Taiwan

    26. 26 Constructed Wetlands at Chu-Nan Coast

    27. 27 Hong Kong Wetland Park (1/2)

    28. 28 Hong Kong Wetland Park (2/2)

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