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Relating Wetland Functions to Stormwater Nitrogen Load Removal in Bioretention Areas

Relating Wetland Functions to Stormwater Nitrogen Load Removal in Bioretention Areas. Non-point Pollution Control:. Sharkey 2001. NC STATE UNIVERSITY. The Problem. Increased Runoff. Short Circuit Groundwater. Nutrient Addition From Stormwater. NH3-N .22mg/L NO3-N .25mg/L*

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Relating Wetland Functions to Stormwater Nitrogen Load Removal in Bioretention Areas

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  1. Relating Wetland Functions to Stormwater Nitrogen Load Removal in Bioretention Areas Non-point Pollution Control: Sharkey 2001 NC STATEUNIVERSITY

  2. The Problem Increased Runoff Short Circuit Groundwater

  3. Nutrient Addition From Stormwater • NH3-N .22mg/L • NO3-N .25mg/L* • TKN .88mg/L • OP .10mg/L • TP .14mg/L From J.S. Wu (1996), *Greensboro data. Concentrations in Runoff Annual Loadings Research By Hunt (2003)

  4. Particulate Organic Nitrogen (PON) Soluble Organic Nitrogen (SON) Ammonia-N (NH4-N) Ammonium-N (NH3-N) Nitrate-N (NO3-N) Vegetative N Addition to Surface Water

  5. Nitrogen Transformations In Wetland Soils • Enzymatic Hydrolosis of Organic N • Mineralization • Nitrification in Aerobic Zone (NO3 Reduction) • Adsorption/Desorption of NH4-N • Volatization of NH3-N • Denitrification in Anaerobic zone • Vertical Flux by Vegetative Assimilation and Decay, Settling of PON

  6. Bottom portion of bio-retention i anaerobic due to elbow in drain pipe. Aerobic zone throughout. Water freely drains from entire soil profile. Allowable Ponding 24 mm Concrete Drop Box with Standard Inlet 350 mm Top layer: Mulch 8 – 16 mm Sandy loam – Loamy Sand fill soil 1 – 1.2 m 5 – 10 mm Outlet pipe (RCP or CMP typ) for overflow and drainage. Washed Gravel Envelope Corrugated Plastic Underdrain (typically 4” diameter) Soil Surface Cross Sections of Bioretention Area From Hunt 2003 Soil Surface Aerobic Zone: Nitrification (NH4 to NO3) Anaerobic Zone: Denitrification (NO3 to N2) From Hunt 2003

  7. Site Excavation Elbow used to induce anoxic conditions Overflow Drain Drainage Layer/ Washed Stone Backfill Soil Photos: Bill Lord, 2001

  8. Greensboro Bio-retention Sites Cell #2 Cell #1 August, 2003 Sharkey ‘03

  9. Reductions by Bioretention Areas Lab Studies of Induced Anaerobic Layer Conclude Higher Reductions Complications in relating these to Field studies.

  10. The Problem

  11. SOURCES Martin, Jay F, Reddy, K R. 1997. Interaction and Spatial Distribution of Wetland Nitrogen Processes. Ecological Modeling. 105: 1-21. Hunt, WF. 2003. Pollutant Removal Evaluation and Hydraulic Characterization for Bioretention Stormwater Treatment Devices. Unpublished Thesis Document. Wu, Jy S., Allen, C. J. 1998. Characterization and Pollutant Loading for Highway Runoff. J. of Environmental Engineering. July, 1998: 584-592.

  12. QUESTIONS? Sharkey 2000

  13. Nitrogen Model for Wetland Soil

  14. Reactions • NH4+ + OH-  H2O + NH3 • NH4+ + O2  NO3 • 2NO3  N2O  N2

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