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Denitrification in Constructed Wetlands Used for Treatment of Swine Wastewater Presented in the Jour

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Title: Denitrification in Constructed Wetlands Used for Treatment of Swine Wastewater Presented in the Jour


1
Denitrification in Constructed Wetlands Used for
Treatment of Swine WastewaterPresented in the
Journal of Environmental Quality, March-April 2003
  • Authors P. Hunt, T. Matheny, and A. Szogi

2
Denitrification in Constructed Wetlands Used for
Treatment of Swine Wastewater
  • Presented by
  • Patty Madigan

3
Traditional Method of Treatment
  • storage and treatment in anaerobic lagoon
  • then application to cropland
  • Advantages natural treatment nitrogen
    utilization low cost
  • Disadvantages needs large areas of cropland
    close by pumping long distances is costly

4
Alternative Method Constructed Wetlands
  • Used for municipal wastewater for more than 20
    years.
  • Recently begun to treat animal wastewater.
  • Purpose is to remove nitrogen before land
    application lowers amount of cropland necessary.

5
Problem What is the primary nitrogen loss
mechanism?
  • Ammonia volatilization accounts for only a small
    portion of nitrogen loss.
  • Denitrification could be the primary loss
    mechanism, but it is affected by many conditions.

6
Objective of This Study
  • Assess denitrification and denitrification enzyme
    activity (DEA) in relation to
  • plant communities
  • N loading
  • carbon and nitrogen limitations
  • water depth

7
Methods
8
Methods
  • Soil samples were collected from four quadrants
    of each cell on 12 dates over four years
  • Samples received the following treatments
  • Non-amended
  • NO3
  • Glucose
  • NO3 and glucose, with and without acetylene

9
Methods
  • Acetylene was added to block conversion of N20 to
    N
  • Rates of N20 accumulation were measured using gas
    chromatography

10
Results
  • The first and second cells showed no significant
    difference, so data was pooled.
  • There was no significant difference by season.
  • Denitrification in the bulrush wetland was
    significantly higher than the cattail wetland.
  • Disturbed soil sample had higher values than
    intact soil cores.

11
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13
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14
Water Depth
  • One of the most influential factors in
    denitrification in the wetlands.
  • More dramatic in bulrush cells than cattail
    cells.

15
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16
Conclusions
  • Denitrification was active in both intact and
    disturbed soil samples.
  • Bulrush wetlands had higher DEA rates.
  • DEA rates increased over time as applied N
    increased and wetlands matured.
  • Nitrate was generally the limiting factor, but
    carbon provided by the plants was sufficient
    unless high additions of nitrate were made.

17
More
  • Water depth was significant in bulrush wetlands
    (avg. depth 150 300mm).
  • Decreased DEA with depth is probably caused by
    decreased O2, and increased diffusion path.
  • Cattail wetlands did not show as much response to
    depth change probably due to cattails
    inability to establish oxidative conditions for
    nitrification.

18
  • Denitrification an be very significant in
    removel of N from constructed wetlands used for
    treatment of swine wastewater.
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