Relating Wetland Functions to Stormwater Nitrogen Load Removal in Bioretention Areas

1
Relating Wetland Functions to Stormwater Nitrogen
Load Removal in Bioretention Areas
Non-point Pollution Control
Sharkey 2001
NC STATE UNIVERSITY
2
The Problem
Increased Runoff
Short Circuit Groundwater
3
Nutrient Addition From Stormwater
Concentrations in Runoff
Annual Loadings

• NH3-N .22mg/L
• NO3-N .25mg/L
• TKN .88mg/L
• OP .10mg/L
• TP .14mg/L
• From J.S. Wu (1996),
• Greensboro data.

Research By Hunt (2003)
4
Addition to Surface Water

• Particulate Organic Nitrogen (PON)
• Soluble Organic Nitrogen (SON)
• Ammonia-N (NH4-N)
• Ammonium-N (NH3-N)
• Nitrate-N (NO3-N)
• Vegetative N

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
(No Transcript)
7
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
8
Site Excavation
Elbow used to induce anoxic conditions
Overflow Drain
Drainage Layer/ Washed Stone
Backfill Soil
Photos Bill Lord, 2001
9
Greensboro Bio-retention Sites
Cell 1
Cell 2
August, 2003
Sharkey 03
10
Reductions by Bioretention Areas
Lab Studies of Induced Anaerobic Layer Conclude
Higher Reductions Complications in relating
these to Field studies.
11
The Problem
12
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 Unpublished Thesis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.
13
QUESTIONS?
Sharkey 2000
14
Nitrogen Model for Wetland Soil
15
Reactions

• NH4 OH- ? H2O NH3
• NH4 O2 ? NO3
• 2NO3 ? N2O ? N2