Treatment Wetlands

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Treatment Wetlands Constructed Wetlands

• Chapter 20

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History

• German scientists used constructed basins with
  macrophytes to purify wastewater
• US researchers in the 1970s examined use of
  natural wetlands to treat wastewater
• EPA provides strong support for treatment wetlands

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Approaches

• Natural wetlands dump wastewater into existing
  wetlands natures kidneys
• Before legal protection of wetlands
• Constructed wetlands built to mimic natural
  wetlands, not part of natural systems
• Surface-flow standing water most of the year
• Subsurface-flow water flows through porous
  substrate supporting one or two macrophytes

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Classification by Vegetation

• 1. Free-floating macrophyte systems water
  hyacinth, duckweed
• 2. Emergent macrophyte Phragmites, Typha
• 3. Submerged macrophyte
• 4. Forested
• 5. Multispecies algal systems

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Early Studies

• Max-Planck Institute, Germany 1950s created
  gravel bed macrophyte system, reduced bacteria,
  inorganic and organic chemicals, led to
  subsurface constructed wetlands across Europe
• University of Florida early 1970s secondarily
  treated wastewater added to cypress domes at 2.5
  cm/week. Lowered nutrients, heavy metals,
  microbes and viruses. Productivity increased.
• University of Michigan mid-1970s dumped up
  to 5,000 m3/d of secondarily treated wastewater
  into a fen. Lowered ammonia N and total
  dissolved P, Cl didnt change

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Wetland Types by Source

• Municipal wastewater
• Mine drainage low pH, high iron, sulfate,
  aluminum, and trace metals
• Stormwater and nonpoint source seasonal,
  sporadic, variable flows.
• Landfill leachate collect and treat runoff from
  lined landfills, to reduce ammonium and COD
• Agricultural wastewater wastewater from
  concentrated animal feeding operations (CAFOs),

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Ohio State Wetland Research Center
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Treatment for Arizona CAFO (Feedlot)
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Wetland Design

• to integrate natural processes as much as
  possible
• Hydrology basis for biological and chemical
  conditions response
• Hydroperiod and depth
• Seasonal pulses
• Hydraulic loading and detention rate
• Optimum detention time from 5-14 days for
  municipal water

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Basin morphology

• slopes of 61 to 101
• Variety of depths allows multiple treatments
• Deep denitrification, increase sediment
  retention
• Shallow - allows for more soil/water
  interaction and emergent vegetation
• Series of cells can be used to enhance treatment

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Other Wetland Design Factors

• Chemical loading
• Important for nutrients and other chemicals Fe,
  Selenium
• Substrate/Soils
• Organic matter important due to cation exchange
  capacity
• Texture important in determining if it will be
  subsurface or overflow
• Vegetation few plants thrive in high nutrient
  conditions
• Typha, Scipus, Phragmites, Lemna, Eichhornia
  crassipes

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Management

• Plant removal several times a year increases
  nutrient/chemical removal, stimulates growth
• Mosquito control use of mosquito fish (Gambusia
  affinis) and bacterial insecticides (Bacillus
  thuringensis (Bt), Bacillus sphaericus and
  Lagenidium giganteum)
• Pathogen transmission chlorination of municipal
  water, sampling

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Other benefits

• Surface flow increases wildlife, may help in land
  building
• Costs
• Cost/ha decreases as size of wetland increases
  (200,000/ha for 1-ha, 60,000/ha for 10-ha,
  19,000/ha for 100-ha)
• Generally cheaper than chemical treatments
• Release much less CO2 than chemical treatment
  (Table 20-10)

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Developing country model
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Wetlands in Arizona
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Links

• For treatment of manure waste
• www.epa.gov/seahome/ manure/src/wetlands.htm
• Constructed wetland CADD drawings
• www.sc.nrcs.usda.gov/ technical/constwet.html
• Images from Purdue
• www.ces.purdue.edu/ onsite/alternatives.htm
• Wetlands for farm waste
• msa.ars.usda.gov/.../ nsl/wqe_unit/wetlands.html 
• For fecal sludge treatment in Thailand
• www.sandec.ch/FaecalSludge/ pages/FSM-construc...
• In Arizona
• http//ag.arizona.edu/OALS/ALN/aln45/wetlands.html
  wetlands6anchor
• Remediation of mine tailings
• www.uc.edu/news/ wetlands.htm
• www.enviromine.com/ wetlands/Welcome.htm