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Impact of Point Sources on Nutrient Interactions in Ozark Streams

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  032282,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13827) @2003
Authors:   S. A. Ekka, B. E. Haggard, M. D. Matlock, I. Chaubey
Keywords:   Wastewater treatment plants; phosphorus; sediments; equilibrium P concentration

An investigation was carried out in three streams of the Illinois River Basin, northwest Arkansas, to examine the impact of wastewater treatment plant (WWTP) phosphorus (P) additions on stream water and sediments. We selected a reference (upstream) site and four sites downstream of the WWTP discharge in each stream; water and sediment samples were collected from July 2002 through January 2003. Water samples were analyzed for soluble reactive phosphorus (SRP) and chloride concentrations; sediment extractions included exchangeable phosphorus (EXP), equilibrium phosphorus concentration (EPC) and phosphorus sorption index (PSI). The results obtained show that SRP concentrations were relatively low at reference sites but increased significantly at sites downstream of the WWTP as high as 7.6mg/L at Spring Creek. SRP concentrations decreased exponentially with increasing distance from WWTP, suggesting temporary storage within the streams. However, it was apparent that dilution, not assimilation, was responsible for the decline in SRP concentrations when chloride concentrations were used to correct for subsurface and tributary flow contributions. The loosely exchangeable phosphorus (EXP) in sediments increased at sites downstream from WWTP suggesting greater bioavailability of sediment bound P. The P concentration at which sediments are in equilibrium with the stream water (EPC) was greater downstream of WWTP compared to reference site. The EPC indicated that sediments were a source, sink, and in equilibrium at different streams. Sediment phosphorus buffering capacity (PSI) decreased at sites below the WWTP compared to the reference sites. The municipal WWTPs significantly impacted stream water SRP concentrations and sediment bound-P.

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