Open-File Report 2007–1040

Methods for Estimating Annual Wastewater Nutrient Loads in the Southeastern United States

U.S. Geological Survey Open-File Report 2007–1040

By Gerard McMahon, Larinda Tervelt, and William Donehoo

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This report describes an approach for estimating annual total nitrogen and total phosphorus loads from point-source dischargers in the southeastern United States. Nutrient load estimates for 2002 were used in the calibration and application of a regional nutrient model, referred to as the SPARROW (SPAtially Referenced Regression On Watershed attributes) watershed model. Loads from dischargers permitted under the National Pollutant Discharge Elimination System were calculated using data from the U.S. Environmental Protection Agency Permit Compliance System database and individual state databases. Site information from both state and U.S. Environmental Protection Agency databases, including latitude and longitude and monitored effluent data, was compiled into a project database. For sites with a complete effluent-monitoring record, effluent-flow and nutrient-concentration data were used to develop estimates of annual point-source nitrogen and phosphorus loads. When flow data were available but nutrient-concentration data were missing or incomplete, typical pollutant-concentration values of total nitrogen and total phosphorus were used to estimate load. In developing typical pollutant-concentration values, the major factors assumed to influence wastewater nutrient-concentration variability were the size of the discharger (the amount of flow), the season during which discharge occurred, and the Standard Industrial Classification code of the discharger. One insight gained from this study is that in order to gain access to flow, concentration, and location data, close communication and collaboration are required with the agencies that collect and manage the data. In addition, the accuracy and usefulness of the load estimates depend on the willingness of the states and the U.S. Environmental Protection Agency to provide guidance and review for at least a subset of the load estimates that may be problematic.




Purpose and Scope

Use of Point-Source Nutrient Load Estimates in SPARROW

Challenges in Developing Point-Source Nutrient Load Estimates


Methods of Investigation

Developing a Site File by Using the Permit Compliance System and State Databases

Retrieving Monitoring Data from the Permit Compliance System and State Databases

Importing Data into a Common Database

Preparing Data for Load Estimation

Estimating Annual Nutrient Load in Wastewater Discharge

Quality Assuring Estimates of Nutrient Load in Wastewater Discharges


References Cited

Attachment 1: PCS Data Retrieval Routine

Attachment 2: PCS Data Import Program

Attachment 3: North Carolina Data Import Program

Attachment 4: Data Preparation Program

Attachment 5: Typical Pollutant-Concentration Program

Attachment 6: Load Calculation Program

Attachment 7: Load Summary Program

Attachment 8: Flow Magnitude Checking Program

Suggested Citation: McMahon, Gerard, Tervelt, Larinda, and Donehoo, William, 2007, Methods for estimating annual wastewater nutrient loads in the southeastern United States: U.S. Geological Survey Open-File Report 20071040, 81 p.


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