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item White, Kathryn

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2009
Publication Date: 1/5/2010
Citation: White, J.W., Coale, F.J., Sims, J., Shober, A.L. 2010. Phosphorus runoff from wastewater treatment biosolids and poultry litter applied to agricultural soils. Journal of Environmental Quality. 39:314-323.

Interpretive Summary: Nonpoint source pollution of surface waters by agricultural phosphorus (P) is a major environmental concern in many areas of the United States. This problem has been caused in part by applications of organic P sources such as manures and biosolids which have increased soil P concentrations above agronomic levels. In contrast to most manures which are not chemically treated, wastewater treatment plant (WWTP) processes, such as metal salt amendment or lime stabilization, may influence soil P solubility and affect the risk of P loss in surface runoff. Data is needed on the effect of WWTP amendments on the risk for P transport from agricultural soils following biosolids application. We conducted a two year field rainfall simulation study to compare the effects of biosolids produced by different WWTP processes (lime stabilization, iron (Fe) salt amendment, or Fe salt amendment with lime stabilization) and poultry litter (PL) on soil P solubility and runoff P losses from conventional corn production systems in Delaware and Maryland. Application of biosolids and PL affected all forms of soil P measured. However, the magnitude of the changes varied depending on the P source, despite the fact that all sources added approximately 270 lb total P (TP) per acre. The greatest increases in soil P occurred with application of lime stabilized biosolids and PL, followed by the Fe amended and lime stabilized biosolids. The Fe amended biosolids never increased any measured form of soil P relative to the unamended soil. The differences in soil P solubility were generally mirrored in runoff P concentrations. Dissolved and bioavailable P concentrations were initially most elevated by PL application but by the second year lime stabilized biosolids amended soils contributed the highest concentrations, likely due to the dissolution of calcium P minerals from the biosolids over time. Soils that received Fe amended biosolids consistently produced the lowest concentrations of dissolved and bioavailable P in runoff. Differences in P solubility in biosolids from differing WWTP processes clearly influenced P solubility in amended soils, as well as the magnitude of soluble and bioavailable P concentrations in surface runoff. The results of this study indicate that nutrient management plans must account for both the differences in the properties of treated biosolids and their effect on soil P saturation and solubility. This will allow for effective management of biosolids application to protect water quality without unnecessarily restricting the beneficial reuse of these materials.

Technical Abstract: Differences in the properties of organic phosphorus (P) sources, particularly those that undergo treatment to reduce soluble P, can affect soil P solubility and P transport in surface runoff. This two year field study investigated soil P solubility and runoff P losses from two agricultural soils in the Mid-Atlantic region following land application of biosolids derived from different wastewater treatment processes and poultry litter. Phosphorus speciation in the biosolids and poultry litter differed due to treatment processes and significantly altered soil P solubility and dissolved reactive P (DRP) and bioavailable P (FeO-P) concentrations in surface runoff. Runoff total P (TP) concentrations were closely related to sediment transport. Initial runoff DRP and FeO-P concentrations varied among the different biosolids and poultry litter applied. Over time, as sediment transport declined and DRP concentrations became an increasingly important component of runoff FeO-P and TP, total runoff P was more strongly influenced by the type of biosolids applied. Throughout the study, application of lime-stabilized biosolids and poultry litter increased concentrations of soil soluble P, readily desorbable P and soil P saturation resulting in increased DRP and FeO-P concentrations in runoff. Land application of biosolids generated from wastewater treatment processes that used amendments to reduce P solubility (e.g., FeCl3) did not increase soil P saturation and reduced the potential for DRP and FeO-P transport in surface runoff. These results illustrate the importance of wastewater treatment plant process and determination of specific P source coefficients to account for differential P availability among organic P sources.