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Constructed Wetlands

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Constructed wetlands are small artificial wastewater treatment systems consisting of one or more shallow treatment cells, with herbaceous vegetation that flourish in saturated or flooded cells.

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Constructed Wetlands Presented By : Zainab Arshad BS Hons, Environmental Sciences University Of Gujrat, Pakistan 1

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Contents:  Wetlands  Wetland Function and Values  Constructed wetlands  Components of Constructed Wetlands  Mechanism to Improve water quality  Advantages of constructed wetlands  Limitations of constructed wetlands  Types of constructed wetlands o Subsurface flow wetland o Surface flow wetland o Horizontal Flow Constructed Wetland  contaminants removal  References 2

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Wetland ■ A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. ■ The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. 4

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Wetland Function and Values: Under appropriate circumstances. wetlands can provide: ■ water quality improvement ■ flood storage and the desynchronization of storm rainfall and surface runoff ■ cycling of nutrients and other materials ■ habitat for fish- and wildlife ■ passive recreation, such as bird watching and photography ■ active recreation, such as hunting ■ education and research ■ aesthetics and landscape enhance merit. 5

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Constructed Wetlands

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What are Constructed wetlands Constructed wetlands are small artificial wastewater treatment systems consisting of one or more shallow treatment cells, with herbaceous vegetation that flourish in saturated or flooded cells. They are usually more suitable to warmer climates. In these systems wastewater is treated by the processes of sedimentation, filtration, digestion, oxidation, reduction, adsorption and precipitation. 7

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Components of Constructed Wetlands: These components can be manipulated in constructing a wetland. ■ Water ■ Substrates, Sediments and Litter ■ Vegetation ■ Aesthetics and landscape enhancement ■ Microorganisms ■ Animals 8

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Mechanism to Improve water quality ■ Settling of suspended particulate matter. ■ Filtration and chemical precipitation through contact of the water with the substrate and litter Chemical transformation. ■ Adsorption and ion exchange on the surfaces of plants, substrate, sediment, and litter. ■ Breakdown and transformation of pollutants by microorganisms and plants. ■ Uptake and transformation of nutrients by microorganisms and plants. ■ Predation and natural die-off of pathogens. 9

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Schematic layout of a constructed wetland 10

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Advantages of constructed wetlands: ■ Wetlands can be less expensive to build than other treatment options. ■ Operation and maintenance expenses (energy and supplies) are low. ■ Operation and maintenance require only periodic, rather than continuous, on-site labor. ■ Wetlands are able to tolerate fluctuations in flow. ■ They facilitate water reuse and recycling. ■ They provide habitat for many wetland organisms. ■ They can be built to fit harmoniously into the landscape.. ■ They are an environmentally-sensitive approach that is viewed with favor by the general public. 11

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Limitations of constructed wetlands: ■ Wetland treatment may be economical relative to other options only where land is available and affordable. ■ Performance may be less consistent than in conventional treatment. ■ The biological components are sensitive to toxic chemicals, such as ammonia and pesticides ■ wetlands can tolerate temporary drawdowns, they cannot withstand ■ There is yet no consensus on the optimal design of wetland systems nor is there much information on their long-term performance. 12

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Types of constructed wetlands 13 Constructed wetlands Subsurface flow constructed wetland Surface flow constructed wetland Floating treatment wetland

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Subsurface flow wetland ■ Subsurface flow wetlands can treat a variety of different wastewaters, such as household wastewater, agricultural, paper mill wastewater, mining runoff, tannery or meat processing wastes, storm water. ■ The quality of the effluent is determined by the design and should be customized for the intended reuse application (like irrigation or toilet flushing) or the disposal method. 14

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Subsurface flow wetland ■ Subsurface flow wetlands can be further classified as horizontal flow and vertical flow constructed wetlands. ■ In the vertical flow constructed wetland, the effluent moves vertically from the planted layer down through the substrate and out (requiring air pumps to aerate the bed). ■ In the horizontal flow CW the effluent moves horizontally via gravity, parallel to the surface, with no surface water thus avoiding mosquito breeding. ■ Subsurface flow systems have the advantage of requiring less land area for water treatment than surface flow. 15

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Subsurface flow wetland 16

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Surface flow wetland: ■ Surface flow wetlands, also known as free water surface constructed wetlands, can be used for tertiary treatment or polishing of effluent from wastewater treatment plants. They are also suitable to treat storm water drainage. ■ Surface flow CWs are characterized by the horizontal flow of wastewater across the roots of the plants. They require a relatively large area to purify water compared to subsurface flow CWs and may have increased smell and lower performance in winter. 17

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Surface flow wetland 18

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Horizontal Flow Constructed Wetland ■ In hybrid or multistage systems, different cells are designed for different types of reactions. Effective wetland treatment of mine drainage may require a sequence of different wetland cells to promote aerobic and anaerobic reactions. as may the re- moral of ammonia from agricultural wastewater 19

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Horizontal Flow Constructed Wetland 20

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Contaminants removal: 21

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Reference's: ■ Abdel-Hady, M., (Ph.D. thesis) 2014. “Hydraulic Study of Drainage System” Constructed Subsurface Wetlands. Mansoura Faculty of Engineering. ■ Nilsson, E., Sha, L., Qian, W., Leedo, M., 2012. Constructed Wetlands “Wastewater Treatment”. VVA No. 1 Decentralized Water and Wastewater Treatment. ■ Powell, J., Homer, J., Glassmeyer, C., Sauer, N., 2009. Alternative wastewater treatment: on-site biotreatment wetlands at the Fernald Preserve Visitors Center. In: WM Conference, Phoenix, Arizona. ■ Xing, A., (M.Sc. thesis) 2012. Recent Developments in Wetland Technology for Wastewater Treatment. Applied Environmental Science, School of Business and Engineering, Halmstad University. ■ Zidan, A.A., El-Gamal, M.A., Rashed, A.A., Abd El-Hady, M.A., 2013. BOD treatment in HSSF constructed wetlands using different media (set-up stage). Mansoura Eng. J. 38 (3.). 22

More Related Content

Constructed Wetlands

  • 1. Constructed Wetlands Presented By : Zainab Arshad BS Hons, Environmental Sciences University Of Gujrat, Pakistan 1
  • 2. Contents:  Wetlands  Wetland Function and Values  Constructed wetlands  Components of Constructed Wetlands  Mechanism to Improve water quality  Advantages of constructed wetlands  Limitations of constructed wetlands  Types of constructed wetlands o Subsurface flow wetland o Surface flow wetland o Horizontal Flow Constructed Wetland  contaminants removal  References 2
  • 3. 3
  • 4. Wetland ■ A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. ■ The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. 4
  • 5. Wetland Function and Values: Under appropriate circumstances. wetlands can provide: ■ water quality improvement ■ flood storage and the desynchronization of storm rainfall and surface runoff ■ cycling of nutrients and other materials ■ habitat for fish- and wildlife ■ passive recreation, such as bird watching and photography ■ active recreation, such as hunting ■ education and research ■ aesthetics and landscape enhance merit. 5
  • 7. What are Constructed wetlands Constructed wetlands are small artificial wastewater treatment systems consisting of one or more shallow treatment cells, with herbaceous vegetation that flourish in saturated or flooded cells. They are usually more suitable to warmer climates. In these systems wastewater is treated by the processes of sedimentation, filtration, digestion, oxidation, reduction, adsorption and precipitation. 7
  • 8. Components of Constructed Wetlands: These components can be manipulated in constructing a wetland. ■ Water ■ Substrates, Sediments and Litter ■ Vegetation ■ Aesthetics and landscape enhancement ■ Microorganisms ■ Animals 8
  • 9. Mechanism to Improve water quality ■ Settling of suspended particulate matter. ■ Filtration and chemical precipitation through contact of the water with the substrate and litter Chemical transformation. ■ Adsorption and ion exchange on the surfaces of plants, substrate, sediment, and litter. ■ Breakdown and transformation of pollutants by microorganisms and plants. ■ Uptake and transformation of nutrients by microorganisms and plants. ■ Predation and natural die-off of pathogens. 9
  • 10. Schematic layout of a constructed wetland 10
  • 11. Advantages of constructed wetlands: ■ Wetlands can be less expensive to build than other treatment options. ■ Operation and maintenance expenses (energy and supplies) are low. ■ Operation and maintenance require only periodic, rather than continuous, on-site labor. ■ Wetlands are able to tolerate fluctuations in flow. ■ They facilitate water reuse and recycling. ■ They provide habitat for many wetland organisms. ■ They can be built to fit harmoniously into the landscape.. ■ They are an environmentally-sensitive approach that is viewed with favor by the general public. 11
  • 12. Limitations of constructed wetlands: ■ Wetland treatment may be economical relative to other options only where land is available and affordable. ■ Performance may be less consistent than in conventional treatment. ■ The biological components are sensitive to toxic chemicals, such as ammonia and pesticides ■ wetlands can tolerate temporary drawdowns, they cannot withstand ■ There is yet no consensus on the optimal design of wetland systems nor is there much information on their long-term performance. 12
  • 13. Types of constructed wetlands 13 Constructed wetlands Subsurface flow constructed wetland Surface flow constructed wetland Floating treatment wetland
  • 14. Subsurface flow wetland ■ Subsurface flow wetlands can treat a variety of different wastewaters, such as household wastewater, agricultural, paper mill wastewater, mining runoff, tannery or meat processing wastes, storm water. ■ The quality of the effluent is determined by the design and should be customized for the intended reuse application (like irrigation or toilet flushing) or the disposal method. 14
  • 15. Subsurface flow wetland ■ Subsurface flow wetlands can be further classified as horizontal flow and vertical flow constructed wetlands. ■ In the vertical flow constructed wetland, the effluent moves vertically from the planted layer down through the substrate and out (requiring air pumps to aerate the bed). ■ In the horizontal flow CW the effluent moves horizontally via gravity, parallel to the surface, with no surface water thus avoiding mosquito breeding. ■ Subsurface flow systems have the advantage of requiring less land area for water treatment than surface flow. 15
  • 17. Surface flow wetland: ■ Surface flow wetlands, also known as free water surface constructed wetlands, can be used for tertiary treatment or polishing of effluent from wastewater treatment plants. They are also suitable to treat storm water drainage. ■ Surface flow CWs are characterized by the horizontal flow of wastewater across the roots of the plants. They require a relatively large area to purify water compared to subsurface flow CWs and may have increased smell and lower performance in winter. 17
  • 19. Horizontal Flow Constructed Wetland ■ In hybrid or multistage systems, different cells are designed for different types of reactions. Effective wetland treatment of mine drainage may require a sequence of different wetland cells to promote aerobic and anaerobic reactions. as may the re- moral of ammonia from agricultural wastewater 19
  • 22. Reference's: ■ Abdel-Hady, M., (Ph.D. thesis) 2014. “Hydraulic Study of Drainage System” Constructed Subsurface Wetlands. Mansoura Faculty of Engineering. ■ Nilsson, E., Sha, L., Qian, W., Leedo, M., 2012. Constructed Wetlands “Wastewater Treatment”. VVA No. 1 Decentralized Water and Wastewater Treatment. ■ Powell, J., Homer, J., Glassmeyer, C., Sauer, N., 2009. Alternative wastewater treatment: on-site biotreatment wetlands at the Fernald Preserve Visitors Center. In: WM Conference, Phoenix, Arizona. ■ Xing, A., (M.Sc. thesis) 2012. Recent Developments in Wetland Technology for Wastewater Treatment. Applied Environmental Science, School of Business and Engineering, Halmstad University. ■ Zidan, A.A., El-Gamal, M.A., Rashed, A.A., Abd El-Hady, M.A., 2013. BOD treatment in HSSF constructed wetlands using different media (set-up stage). Mansoura Eng. J. 38 (3.). 22