aquatic plants and the environment (swes, ecol, wfsc 474/574) constructed wetlands dr. kevin...
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Aquatic Plants and the Environment (SWES, ECOL, WFSc 474/574)
Constructed Wetlands
Dr. Kevin FitzsimmonsProfessor – University of Arizona
Terminology of constructed wetlands
• 1. Restored wetlands - those under rehabilitation. Put back into working order (fixed) hydrology of wetland either by dredging or by taking out a dike (common in small areas).
• 2. Constructed wetlands - built where none existed before (usually for water treatment). Usually well engineered.
• 3. Created wetlands - developed where none existed before (usually for wildlife habitat). Normally done with little engineering.
Reasons for constructed wetlands
• 1. Waste Treatment • 2. Hydraulic modification - for flood control, water
storage • 3. Water quality changes • 4. Erosion protection • 5. Open spaces and aesthetics • 6. Mitigation • 7. Habitat for wildlife
1. Waste Treatment
• Municipal waste (sewage): secondary/tertiary treatment of wastewaters. To reduce the nitrogen, phosphorus, TSS (Total Suspended Solid), BOD (Biological Oxygen Demand), TFC (Total Fecal Coliforms).
• CAFO treatments (Concentrated Animal Feeding Operations): treat wastes from dairies, feedlots, hog sheds, chicken ranches, and fish farms.
1. Waste Treatment
• Acid Mine Drainage: Absorb heavy metals and increase the pH.
• Highway Runoffs: Effective for cleaning the water that runs off roads carrying oil, gas, dirt, etc.
• Specific Pollutants: Wetlands put in to treat or absorb a heavy metal or organic. Often, the plants will accumulate chemicals inside the plant stem and leaves (concentrating the pollutants). The plant can then be disposed of.
• Storm Water: Handle storm waters in developed areas where runoff is a problem. Cleans up runoff as well.
2. Hydraulic modification
• Flood control – reduce flood waters and impacts
• Water storage – reservoir• Groundwater recharge
3. Specific water quality changes
• Reduce sediment loading• Raise or lower extremes of pH• Add or remove organics (remove in the case of
paper mills, add in acid mine drainage).
4. Erosion and flood protection
• Bank or shoreline stabilization• Dissipation of wave energy• Dissipation of flood flows• Alter flow patterns of stream or river
5. Open spaces and aesthetics
• Used by resorts or new developments to increase land value.
• Adds nature values• Property owners will pay extra for sounds, smells
and sights of wildlife and wetland plants
6. Mitigation
• Intended to replace the function of lost wetlands.• In US, when developers destroy wetlands they
must replace them by a 1 to 2 or 1 to 3 ratio.• The developer is not only responsible for
replacement, but the function as well. • Usually replaced wetlands do not function as well.
Lots of problems occur with how to build and maintain them.
7. Habitat as life support
• Habitat specifically for threatened and endangered species
• Habitat for other wildlife.
Design of constructed wetlands
• A. Free water surface systems (FWS): have open water surfaces, water is exposed, covering the substrate, submerged and emergent plants.
• B. Subsurface flow systems (SFS): water below surface level, the substrate is exposed to air at the surface. Only emergent plants
Design of constructed wetlands
• A. Free water surface systems (FWS): have open water surfaces, water is exposed, covering the substrate, submerged and emergent plants.
• B. Subsurface flow systems (SFS): water below surface level, the substrate is exposed to air at the surface. Only emergent plants
Constructed wetlands can be customized for the task
• Select submerged flow or free surface• Determine volume of anaerobic vs aerobic
needed• Select plants that will accomplish task
- fast growing plants that scour nutrients- plants that bio-accumulate heavy metals- plants that accumulate or break down organics- plant community that drops leaves to add organics to water
Typical subsurface flow systems
Treating grey water from a house in Italy
Treating municipal waste in Virginia, USA