Constructed Wetlands Constructed Wetlands
ByBy
Dave LomeliDave Lomeli
Why use a Constructed Wetland• Constructed wetlands can treat wastewater from a variety of Constructed wetlands can treat wastewater from a variety of
sources. One of the more common uses is to provide additional sources. One of the more common uses is to provide additional or advanced treatment of or advanced treatment of wastewater from homeswastewater from homes, , businessesbusinesses and and even communitieseven communities. Wetlands treat wastewater that has . Wetlands treat wastewater that has already had most of the solid materials removed from it through already had most of the solid materials removed from it through some type of primary or secondary treatment. some type of primary or secondary treatment.
• Homes, businesses, farms, schools, highways and other Homes, businesses, farms, schools, highways and other individual wastewater sources in rural areas sometimes can add individual wastewater sources in rural areas sometimes can add a constructed wetland to a septic system or other onsite system a constructed wetland to a septic system or other onsite system to replace or assist a soil absorption field. to replace or assist a soil absorption field.
• Some onsite systems can be specifically designed from the start Some onsite systems can be specifically designed from the start to use a constructed wetland in addition to a soil absorption field to use a constructed wetland in addition to a soil absorption field on properties with site constraints, such as tight or saturated on properties with site constraints, such as tight or saturated soils. soils.
• Wetlands are good at handling intermittent periods of both light Wetlands are good at handling intermittent periods of both light and heavy wastewater flows. Therefore, they often work well and heavy wastewater flows. Therefore, they often work well with wastewater treatment systems that serve hotels, with wastewater treatment systems that serve hotels, campsites, resorts and recreational areas.campsites, resorts and recreational areas.
TypesTypes
• Constructed wetlands – built to mimic Constructed wetlands – built to mimic natural wetlands, not part of natural systemsnatural wetlands, not part of natural systems
• Surface-flowSurface-flow
• Subsurface-flowSubsurface-flow
• Vertical Flow SystemsVertical Flow Systems
• New design systems used to overcome New design systems used to overcome oxygen depletion problems in wetlandsoxygen depletion problems in wetlands
Wet Land Design factorsWet Land Design factors
Basic questionsBasic questions: - Geographic : - Geographic
- Economic - Economic
- - VegetationVegetation
- Substrate/soils- Substrate/soils - Chemical - Chemical input/outputinput/output
- - Compartments/cellsCompartments/cells
- Maintenance- Maintenance
- Unexpected events- Unexpected events
- Outlet - Outlet considerationsconsiderations
Design FactorsDesign FactorsOne of the most important factors affecting treatment is temperature. • Biological treatment processes tend to speed up in warm weather and slow down in cold weather. In cold climates, systems must be large enough to accommodate the longer hydraulic residence times needed for treatment.
• Plants help treatment processes in several ways. The wetland plants filter wastes, regulate flow and provide surface area for bacterial and treatment.
• Floating plants, such as water lilies and emergent plants, such as cattails, shade the water surface and control algae growth.
• Even in winter when plants are dormant, they often are contributing to treatment Plants also contribute to treatment by taking up nutrients, metals, and other substances and retaining them. Many of these substances can accumulate again in the wetland when the plants die and decompose. Therefore harvesting vegetation is a good idea.
Design
types
Surface FlowSurface Flow• Surface-Flow Treatment WetlandsSurface-Flow Treatment Wetlands
• As soon as wastewater enters a surface flow wetland cell, As soon as wastewater enters a surface flow wetland cell, natural processes immediately begin to break down and natural processes immediately begin to break down and remove the waste materials in the water. Before the remove the waste materials in the water. Before the wastewater has moved very far in the wetland small wastewater has moved very far in the wetland small suspended waste materials are physically strained out be suspended waste materials are physically strained out be submerged plants, plant stems, and plant litter in the wetland. submerged plants, plant stems, and plant litter in the wetland. The roots, stems, leaves, and litter of wetland plants also The roots, stems, leaves, and litter of wetland plants also provide a multitude of small surfaces where wastes can provide a multitude of small surfaces where wastes can become trapped and waste-consuming bacterial can attach become trapped and waste-consuming bacterial can attach themselves.themselves.
Operation & Maintenance Surface Flow Wetland
• Surface flow wetlands have few operation and Surface flow wetlands have few operation and maintenance requirements, but maintenance must be maintenance requirements, but maintenance must be performed properly to ensure system performance. performed properly to ensure system performance.
• Operation may entail alternating cells or adjusting Operation may entail alternating cells or adjusting water levels and harvesting vegetation. water levels and harvesting vegetation.
• Some systems may have banks and berms that need Some systems may have banks and berms that need to be maintained, and inlet and outlet structures that to be maintained, and inlet and outlet structures that should b cleaned periodically. should b cleaned periodically.
• Mosquitoes and burrowing animals present problems in Mosquitoes and burrowing animals present problems in some systems. Different control methods are some systems. Different control methods are available, including natural solutions, such as trapping available, including natural solutions, such as trapping and relocating animals, introducing fish that eat insect and relocating animals, introducing fish that eat insect larvae, and building bat houses. larvae, and building bat houses.
Subsurface FlowSubsurface FlowIn SSF wetlands the polluted substrate is transported through material (depends on what they want to use) where bacteria in the substrate and on the plants come in contact with the contaminated water and effectively degrade or bind the pollutant. Four basic parameters are considered when finalizing the layout and design of SSF wetlands: (1) Inlet distribution system, (2) Basin configuration, (3) Bed media, and (4) Outlet control system (Kadlec et al, 1996).
• Surface flow wetlands have few operation and Surface flow wetlands have few operation and maintenance requirements, but maintenance maintenance requirements, but maintenance must be performed properly to ensure system must be performed properly to ensure system performance. performance.
• Operation may entail alternating cells or Operation may entail alternating cells or adjusting water levels and harvesting vegetation. adjusting water levels and harvesting vegetation. Some systems may have banks and berms that Some systems may have banks and berms that need to be maintained, and inlet and outlet need to be maintained, and inlet and outlet structures that should be cleaned periodicallystructures that should be cleaned periodically
Operation & Maintenance Subsurface Flow Wetland
AdvantagesAdvantages
• Constructed wetlands are typically Constructed wetlands are typically inexpensive to build and maintain.inexpensive to build and maintain.
• They require little or no energy to operate.They require little or no energy to operate.• They can provide effective tertiary They can provide effective tertiary
treatment.treatment.• They can provide additional wildlife habitat.They can provide additional wildlife habitat.• They can be aesthetically pleasing additions They can be aesthetically pleasing additions
to homes and neighborhoods.to homes and neighborhoods.• They are viewed as an environmentally They are viewed as an environmentally
friendly technology and are generally well friendly technology and are generally well received by the public.received by the public.
DisadvantagesDisadvantages
• Constructed wetlands require more land Constructed wetlands require more land area than many other treatment options.area than many other treatment options.
• Surface flow wetlands can attract mosquitoes Surface flow wetlands can attract mosquitoes and other pests.and other pests.
• Wetlands are not appropriate for treating Wetlands are not appropriate for treating some wastewater with high concentrations of some wastewater with high concentrations of certain pollutants.certain pollutants.
• The performance of wetlands may vary based The performance of wetlands may vary based on usage and climatic conditions.on usage and climatic conditions.
• There may be a prolonged initial start-up There may be a prolonged initial start-up period before vegetation is adequately period before vegetation is adequately established.established.
Examples of Constructed Examples of Constructed WetlandsWetlands
•Mai Po Marshes, Honk Kong
•Putrajaya Lake and constructed wetlands, Malaysia
In : (1) Mai Po Marshes, Honk Kong
Mia Po MarshesMia Po Marshes• 1976 - the Mia Po Marshes were recognized as a 1976 - the Mia Po Marshes were recognized as a
protected areaprotected area
• 1983 - They were Declared a nature conservation 1983 - They were Declared a nature conservation area area
• The WWF then took over managing and The WWF then took over managing and developing the area for conservation and developing the area for conservation and education.education.
• 1995 – Mia Po Marshes and Inner Deep Bay area 1995 – Mia Po Marshes and Inner Deep Bay area were named wet lands of International importance were named wet lands of International importance under the Ramsar conventionunder the Ramsar convention
Mai Po MarshesMai Po Marshes
• The Ponds are 10ha and 1-1.5m deepThe Ponds are 10ha and 1-1.5m deep
• Largest area of vegetation in Mai Po is in the Largest area of vegetation in Mai Po is in the mangroves, reedbeds, & sedges mangroves, reedbeds, & sedges (F:cyperaceae) (F:cyperaceae)
• Mangrove forests along w/those of the Deep Mangrove forests along w/those of the Deep Bay Mia Po marshes cover an area of 400haBay Mia Po marshes cover an area of 400ha
• 45-46ha of marshes are composed of reedbeds 45-46ha of marshes are composed of reedbeds
ImportanceImportance• An estimated 2-3million water birds migrate An estimated 2-3million water birds migrate
from their breeding grounds in northern from their breeding grounds in northern China, Mongolia and Siberia, to their China, Mongolia and Siberia, to their wintering grounds in southeast Asia and wintering grounds in southeast Asia and Australasia Australasia
• In winter, up to 68,000 birds winter in these In winter, up to 68,000 birds winter in these wetlands before flying back north in spring to wetlands before flying back north in spring to their breeding grounds. During the spring and their breeding grounds. During the spring and autumn migration periods, the site is used by autumn migration periods, the site is used by an estimated 20,000 - 30,000 shorebirds. an estimated 20,000 - 30,000 shorebirds.
ImportancImportancee• Other mammals recorded from Mai Po and Inner Other mammals recorded from Mai Po and Inner
Deep Bay include the Deep Bay include the Eurasian OtterEurasian Otter (Lutra lutra (Lutra lutra chinensis)chinensis), , Pangolin Manis pentadactylaPangolin Manis pentadactyla, , Chinese Chinese Leopard CatLeopard Cat Felis bengalensis, Felis bengalensis, Crab-eating Crab-eating MongooseMongoose Herpestes urva, Herpestes urva, Seven-banded CivetSeven-banded Civet Viverricula indica and various Muridae, e.g. Viverricula indica and various Muridae, e.g. Bandicoot RatBandicoot Rat Bandicota indica, Soricidae, e.g. Bandicota indica, Soricidae, e.g. House ShrewHouse Shrew Crocidura murinus and Crocidura murinus and batsbats such as such as the Pipistrellus abramus. the Pipistrellus abramus.
• Although the Although the Chinese White DolphinChinese White Dolphin Sousa Sousa chinensis has previously been recorded up the chinensis has previously been recorded up the Shenzhen River as far as Lok Ma Chau, its Shenzhen River as far as Lok Ma Chau, its presence in Shenzhen Bay is now doubtful due to presence in Shenzhen Bay is now doubtful due to heavy boat traffic and pollution. heavy boat traffic and pollution.
ImportanceImportance
• Important for biodiversityImportant for biodiversity
• Important for agricultureImportant for agriculture
• Important Education and Economic Important Education and Economic reasonsreasons
In (2):Putrajaya Lake and constructed wetlands, Malaysia
• Created in 1998 by flooding 2 Valleys: Sungai Chau & Sungai Bisa and creating a Dam
• The Dam was constructed (across Sungai Chau) in 1998 and the valley was able to be fully flooded in 1999
• Objectives of the project: make sure it’s environmentally sustainable, water quality sustainable for recreation, and education and research.
Largest Fresh Water wetlands in tropics
Consists of 335ha
Putrajaya Wetlands
PutrajayaPutrajaya• Putrajaya was founded on Putrajaya was founded on
October 19October 19, , 19951995 and is located and is located in the middle of the Multimedia in the middle of the Multimedia Super Corridor (MSC). Super Corridor (MSC).
• It is set to be a model garden It is set to be a model garden city with sophisticated city with sophisticated information network base on information network base on multimedia technologies. multimedia technologies.
• PutrajayaPutrajaya is a planned city and is a planned city and a Federal Territory that acts as a Federal Territory that acts as a federal government a federal government administration centre of administration centre of MalaysiaMalaysia and it was moved here and it was moved here because of the overcrowding because of the overcrowding and congestion in and congestion in Kuala LumpurKuala Lumpur. .
Population: 1) Current residential population:30,0002010 target: 350,0002).Current working population:34,0002010 target: 200,000
Development Phases: i.Phase 1:1996 - 2000 (Completed) ii.Phase 2: 2000 - 2010/2020 Land Use :1).Core Area comprising Government Mixed Development, Civic & Cultural, Commercial and Sports & Recreation Precincts, 2) The Periphery comprising residential areas and Diplomatic Enclave.3) Utilities, facilities, amenities
CellsCells
• Wetland consists of 24 cells seperated by weirsWetland consists of 24 cells seperated by weirs
• Each cell has miniature wetland function that differ Each cell has miniature wetland function that differ between cellsbetween cells
• Cells have surface and subsurface flowsCells have surface and subsurface flows
HabitatHabitat
• More than 70 species of wetland plants More than 70 species of wetland plants totaling 12.3 million plants were planted totaling 12.3 million plants were planted and 24 species of indigenous fish were and 24 species of indigenous fish were introduced in the wetland. introduced in the wetland.
• The wetland performs an ecological role, The wetland performs an ecological role, as a home to a unique and rare species of as a home to a unique and rare species of birds, insects, plants, amphibians, reptiles, birds, insects, plants, amphibians, reptiles, small mammals and other invertebrates small mammals and other invertebrates including water snails. including water snails.
The Putrajaya LakeThe Putrajaya Lake
• The lake is at the southern part of the wetland. The lake is at the southern part of the wetland.
• About 60% of the lake water flow is from the About 60% of the lake water flow is from the wetland and the remaining 40% is the direct wetland and the remaining 40% is the direct discharge from bordering promenade. The 20 m discharge from bordering promenade. The 20 m width promenade is the buffer feature along the width promenade is the buffer feature along the lake shorelines. lake shorelines.
• The water surface area of the whole lake is about The water surface area of the whole lake is about 400 hectares. The total volume of the whole lake 400 hectares. The total volume of the whole lake water is about 23.5 million cubic meters and the water is about 23.5 million cubic meters and the water depth is in the range of 3 to 14 meters. water depth is in the range of 3 to 14 meters.
• The lake has been planned to cater for multi-The lake has been planned to cater for multi-functional uses, including recreation, fishing, water functional uses, including recreation, fishing, water sports and water transport. The lake and its sports and water transport. The lake and its foreshores also form Putrajaya's most popular foreshores also form Putrajaya's most popular resource for informal recreation as a waterfront city. resource for informal recreation as a waterfront city.
ConclusionConclusion
• Constructed Wetlands provide a number Constructed Wetlands provide a number of benefits for animals and humans of benefits for animals and humans
• Provide a great resource for natural Provide a great resource for natural filtering system and flood control systemfiltering system and flood control system
• Cheap alternative to conventional Cheap alternative to conventional methodsmethods
Questions?Questions?
