A Chemical Treatment to Reduce P Desorption From Manure Exposed Fluvial Sediments.

The current remediation methods for manure spills that have reached surface waters give no attention to the P enriched ditch sediments that remain in the fluvial system and continue to impair the water column. Consequently, no method exists to treat P contaminated sediments to reduce their ability to be a P source to the overlying water column. Therefore, the objectives of this study were to determine the impact of a manure spill on sediment adsorption properties and to evaluate the effectiveness of chemically treating manure exposed sediments. These objectives were accomplished using mini-flumes packed with sediment that received the following treatments: (1) no manure and no treatment; (2) manure spill without treating sediment; (3) manure spill followed by 1:1 molar ratio (Al:P) application of aluminum sulfate (alum); and (4) manure spill followed by 2:1 molar ratio (Al:P) application of alum. Phosphorus desorption was monitored using a 24 hr circulation of P free water. Clayey and sandy untreated sediments desorbed 0.09 and 0.23 mg P L-1 within the 24 hour desorption period, respectively. However, treating sediments with a 2:1 application rate of alum and CaCO3 reduced P desorption to soluble P concentrations near background concentrations recorded before the spill occurred. This study suggests that when a manure spill reaches surface waters, sediment P accumulation does occur and untreated sediments become a source of P to the overlying water column. However, treating sediments following a manure spill mitigates P desorption.