Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

First Advisor

Chris Schmit


Phosphorus is the limiting nutrient in the eutrophication of most of our lakes and rivers. Phosphorus can enters our lakes and rivers by means of runoff and erosion from agricultural land. Therefore, the fate of phosphorus from long-term biosolids application to agricultural land is of interest. The primary goal of this study is to determine the fate of phosphorus after many years of biosolids application to nearby farmland by the City of Sioux Falls' wastewater Treatment Plant. The secondary goal is to then give further recommendations to the city of Sioux Falls regarding their current biosolids application practices based on results of the primary goal. Two sites were selected that have had 10 years of surface application of biosolids. One site was a grass pasture the other an alfalfa field. Soil samples were collected starting at the summit and continuing down slope to the toe taking samples at various landscape positions. This pattern of sampling allowed for the tracking of phosphorus down slope. At each landscape position samples were collected in 6-inch increments to a depth of 48 inches, which allowed for the tracking of phosphorus down through the soil depth. The soil samples were then analyzed for the following parameters; total phosphorus, organic phosphorus, inorganic phosphorus, plant available phosphorus, phosphorus buffering, free Fe and Mn, inorganic carbon, bulk density and pH. Results of the soil analysis show little movement of total phosphorus down slope at either site, however, with Olsen phosphorus it was clear that some phosphorus was accumulating down slope. Results also show an increase in Olsen phosphorus in the surface 12 inches at both sites. A mass balance of the total phosphorus was attempted on the alfalfa site V and was able to account for all of the applied phosphorus, which would indicate that no phosphorus has left the site. Based on the results, current application practices preformed by the City of Sioux Falls are sufficient to prevent the movement of total phosphorus off site.

Library of Congress Subject Headings

Land treatment of wastewater -- South Dakota.
Sewage sludge -- South Dakota.
Soils -- Phosphorus content -- South Dakota.
Sewage disposal plants -- South Dakota -- Sioux Falls -- Management.


South Dakota State University



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In Copyright