Wetland Creation and Restoration

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Wetland Creation

• Why?
• Can it be done?
• Does a created wetland serve the same ecological
  purposes as a natural wetland?

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Why Build Treatment Wetlands?

• Improve water quality
• Secondarily, provide wildlife and other wetland
  functions.

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Ecological Services

• biological filters
• natures kidneys
• yada-yada-yada-fact or more environmental hype
  from tree huggers?
• Not a new concept
• Germany in early 1950s
• US in late 60s, dramatically increasing in 1970s

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Whats the Goal?

• Removal of contaminants from water
• contaminant-any undesirable constituent in the
  water that may directly or indirectly affect
  human or environmental health
• anything that degrades the water so that it
  cannot be used for its natural or intended
  purpose.
• might include
• toxic organics and metals
• non-toxics-nutrients
• thermal pollution

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Uses

• Municipal wastewater
• Acid mine drainage (AMD)
• Landfill leachate
• Nonpoint urban/agriculture runoff

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Acid Mine Drainage
Municipal Wastewater Wetland
Landfill Leachate Wetland
Agricultural Runoff Wetland
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Types of Treatment Wetlands

• natural wetlands-use for this often prohibited by
  laws created to protect them
• surface flow wetlands
• subsurface flow wetlands

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What Can Be Treated?

• municipal wastewater (sewage)-residential and
  commercial sources may range from single homes
  to regional scale
• Iron Bridge wetland (FL) is 1200 A (480 ha)
• agricultural wastewater-runoff from cropland,
  pasture, milking and washing barns, and feedlots.
• industrial wastewater-pulp paper manufacturing,
  food processing, slaughtering and rendering,
  chemical manufacturing, refining, and landfill
  leachate

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Overview of Mechanisms of Contaminant Removal
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Contaminant Removal Mechanisms

• Physical
• especially good for sedimentation of
  particulates low velocity laminar flow
• results in accumulation of solids
• may be resuspended by wind-driven turbulence,
  bioturbation (by humans or animals), and gas
  lifting (bubbling of methane, CO2, etc.)
• Biological
• Chemical

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Contaminant Removal Mechanisms

• Biological-perhaps most important?
• Plant uptake
• nutrients (NO3, PO4, ammonium)
• toxics (bioremediation) e.g., lead, cadmium
• rate of removal dependent on growth rate and
  concentration of the contaminant in the tissue
• woody plants sequester more and for longer times
• herbaceous plants (e.g., Typha) have higher rates
• Algae can be significant but are more susceptible
  to toxicity of metals however, have rapid
  turnover
• where does the contaminant go?
• re-release accumulation in peat

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Contaminant Removal Mechanisms

• Biological (continued)
• Microbial processes
• may uptake contaminants in their biomass
• conversions by metabolic processes probably more
  important
• carbon -gt CH4 or CO2 offgassing removes this C
• inorganic Nitrogen (nitrate ammonium)
• nitrate denitrification facilitated by
  Pseudomonas spp.
• NO3 -gt N2 offgassing removes this N
• ammonium nitrification and denitrification
  facilitated by Nitrosomonas and Nitrobacter spp
• NH4 -gt NO3 (aerobic) -gt N2 (anaerobic)

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Contaminant Removal Mechanisms

• Chemical
• sorption (most important)
• transfer of ions from solution phase (water) to
  solid phase (soil)
• includes adsorption and precipitation
• adsorption-attachment of ions to soil particles,
  either by cation exchange (weak attachment to
  negatively charged clay or organic particles)
  effective with ammonium and most trace metals
  (e.g., Cu2)
• or chemisorption-stronger bonding attachment of
  some metals and organics to clays, iron or
  aluminum oxides, and organic matter effective
  with phosphate
• precipitation-combine with iron and aluminium
  oxides forming new, stable, solid compounds also
  production of highly insoluble metal sulfides, a
  way of immobilizing many toxic metals

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Contaminant Removal Mechanisms

• Chemical
• volatilization-diffusion from water to atmosphere
• e,g, ammonia (NH3) (aq) -gt ammonia (gas)
• iff pH gt 8.5 if pH is less than that, N is in
  the form of ammonium which is not volatile
• many other organics are volatile
• increases air pollution?

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Examples and Case Studies
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Olentangy River Wetlands at The Ohio State
University
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Its Good to be a Buckeye!
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