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+ | The adjacent table describes the relative effectiveness of different stormwater runoff practices in treating dissolved phosphorus. Many of the practices shown in the adjacent table can be used in urban and agricultural settings. The following generalizations can be made. | ||
+ | *Pollution prevention and source control are among the most effective ways to decrease phosphorus loads to receiving waters. In particular, the following practices are effective. | ||
+ | **Residential practices, including composting organic material such as leaves (either on-site or off-site at a disposal facility), retaining water on site, removing leaves and grass clippings from impervious surfaces, avoiding use of detergents in vehicle washing, native landscaping, and lawn maintenance | ||
+ | **Controlling pet waste and waste from other animal sources | ||
+ | **Street sweeping using appropriate methods at appropriate times of the year | ||
+ | *Infiltration practices move water from the land surface to shallow groundwater. Phosphorus is generally attenuated in soil, the vadose zone, and within the groundwater system, though in some situations shallow groundwater may discharge locally to surface water and increase phosphorus loading. Proper location of infiltration practices based on an understanding of the local hydrology is necessary if surface waters are at risk. | ||
+ | *Filtration practices are generally ineffective unless they are designed to prevent loss of or retain dissolved phosphorus. Examples of designed systems include use treatment media with a low organic matter content, use of phosphorus-retaining amendments such as iron, and vegetated systems where the vegetation is removed annually. Filtration practices include systems having an underdrain, or tiled systems in agricultural settings. | ||
+ | *Sedimentation practices are generally ineffective at retaining dissolved phosphorus unless amended with aluminum, spent lime, or other iron-sequestering chemicals. |
This page provides a discussion of dissolved phosphorus in stormwater runoff, its sources, and strategies for managing dissolved phosphorus. While the focus is on urban runoff, the basic principles are applicable to agricultural runoff.
Phosphorus in water is often classified as dissolved (soluble) or particulate (attached to or a component of particulate matter) phosphorus. This nomenclature is somewhat ambiguous, however, as dissolved phosphorus consists of multiple forms of phosphorus, including phosphorus attached to other materials.
References for phosphorus forms and testing includes the following.
Dissolved phosphorus is considered to be more bioavailable than particulate forms of phosphorus. Below is a summary of some studies on bioavailability of phosphorus.
There are insufficient data to support recommended event mean concentrations (emcs) of dissolved phosphorus for different land uses. The following table provides a summary of data we felt is appropriate for selecting an emc for dissolved phosphorus. The table does not include data for runoff from agricultural systems. Agricultural runoff is not the focus of this manual and the dynamics of phosphorus transport in agricultural systems are likely to vary widely with soil, crop, season, and phosphorus inputs. See the discussions below on dissolved phosphorus fractions in runoff and management strategies.
Summary of dissolved phosphorus event mean concentrations from various studies. There is inadequate information to provide recommended emcs for different land uses.
Link to this table
Study | Land cover/land use | Range (mg/L) | Mean | Median | Number of samples |
---|---|---|---|---|---|
Dallas-Fort Worth1 | Commercial | 0.01-0.47 | 0.09 | 0.06 | 42 |
Dallas-Fort Worth | Industrial | 0.03-0.45 | 0.14 | 0.09 | 63 |
Dallas-Fort Worth | Residential | 0.04-0.84 | 0.25 | 0.21 | 77 |
Forth Worth2 | Transportation | 0.11 | 28 | ||
Twin Cities3 | Mixed | 0.01-1.4 | 0.2 | 0.15 | 147 |
Madison4 | Medium density residential | 0.52 | 0.61 | 25 | |
Madison4 | Medium density residential | 0.4 | 0.14 | 25 | |
Madison4 | Medium density residential | 0.14 | 0.04 | 25 | |
Madison4 | Medium density residential | 0.05 | 0.03 | 25 | |
Madison4 | Medium density residential | 0.04 | 0.02 | 25 | |
Madison4 | Medium density residential | 0.03 | 0.02 | 25 | |
Madison4 | Medium density residential | 0.04 | 0.02 | 25 | |
Madison4 | Medium density residential | 1.54 | 0.81 | 25 | |
Madison4 | Medium density residential | 0.12 | 0.08 | 25 | |
Madison4 | Medium density residential | 0.11 | 0.07 | 25 | |
Madison4 | Medium density residential | 0.11 | 0.07 | 25 | |
US EPA Nurp Study5 | Residential | 0.143 | |||
US EPA Nurp Study5 | Mixed | 0.056 | |||
US EPA Nurp Study5 | Commercial | 0.08 | |||
US EPA Nurp Study5 | Open | 0.026 | |||
New York6 | Residential | 0.20 | 738 | ||
New York6 | Commercial | 0.18 | 323 | ||
New York6 | Industrial | 0.16 | 325 | ||
New York6 | Open | 0.16 | 44 | ||
Capitol Region Watershed District7 | Mixed | 0.020 - 0.888 | 0.073 | 0.052 | 89 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.565 | 0.108 | 0.087 | 120 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.506 | 0.074 | 0.059 | 112 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.361 | 0.073 | 0.053 | 121 |
Capitol Region Watershed District7 | Mixed | 0.005 -- 0.182 | 0.019 | 0.012 | 195 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.758 | 0.102 | 0.072 | 69 |
Capitol Region Watershed District7 | Mixed | 0.020 - 1.10 | 0.072 | 0.053 | 115 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.60 | 0.099 | 0.057 | 113 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.499 | 0.071 | 0.046 | 138 |
1Urban Stormwater Quality, Event-Mean Concentrations, and Estimates of Stormwater Pollutant Loads, Dallas-Fort Worth Area, Texas. 1992–93 Stanley Baldys III, T.H. Raines, B.L. Mansfield, and J.T. Sandlin U.S. Geological Survey Water-Resources Investigations Report 98–4158.
2Computed and Estimated Pollutant Loads, West Fork Trinity River, Fort Worth, Texas, 1997. United States Geological survey. Water Resources Investigations Report 01–4253
3Brezonik and stadelman. 2002. Analysis and predictive models of stormwater runoff volumes, loads, and pollutant concentrations from watersheds in the Twin Cities metropolitan area, Minnesota, USA. Water Research Volume 36, Issue 7, Pages 1743-1757
457.Waschbusch, R.J., W.R. Selbig, and R.T. Bannerman. 1999. Sources of phosphorus and street dirt from Two Urban Residential Basins in Madison, Wisconsin, 1994-95. USGS Water-Resources Investigation Report 99-4021
5U.S. EPA. Results of the Nationwide Urban Runoff Program. 1983. Volume I: Final Report. PB84-185552
6New York State Department of Environmental Conservation. August 2003. Stormwater Management Design Manual. Chapter 5 - Acceptable Stormwater Management Practices.
7Outfall monitoring data for Villa Park, Trout Brook East, Trout Brook West, Trout Brook Outlet, St. Anthony, Phalen Creek, Como 3, Como 7, and East Kittsendale
Another consideration is the fraction or percent of total phosphorus in runoff that is in dissolved form. A more complete discussion of this is found here, including literature references. The data on phosphorus fractionation is limited, but the following general statements can be made.
Effectiveness of stormwater BMPs in treating dissolved phosphorus (DP) | ||
BMP | Effectiveness | Comment |
Infiltration practices | Effective | DP may be transported to groundwater, but this generally represents a low risk to aquatic environments |
Biofiltration (includes tree trenches) | Ineffective | Some DP removal occurs through plant uptake but phosphorus is typically released from the media |
Enhanced biofiltration | Effective | In properly designed and maintained systems, iron, aluminum, and calcium adsorb DP |
Swales designed for filtration | Ineffective | Addition of engineered media with a low phosphorus concentration may enhance removal through infiltration and biological uptake |
Constructed ponds | Limited | Some biological uptake may occur, but as sediment builds in ponds, DP release may occur |
Constructed wetlands | Limited | Some biological uptake and immobilization in sediment may occur |
Green roofs | Ineffective | Typically leach DP from engineered media during the first several years after construction |
Street sweeping | Effective | Most effective when done at times when coarse organic particles (e.g. from leaves) are targted |
Pollution prevention | Effective | Focus on organic sources (e.g. yard debris), animal waste, detergents, fertilizer |
The adjacent table describes the relative effectiveness of different stormwater runoff practices in treating dissolved phosphorus. Many of the practices shown in the adjacent table can be used in urban and agricultural settings. The following generalizations can be made.