Effects of Sediment Resuspension and Oxygenation on Oxygen Uptake Rate

Abstract

<abstract> <bold>Abstract.</bold> This lab-scale study examined a method to potentially decrease sediment oxygen demand (SOD) in eutrophic reservoirs by forced resuspension and resettling of sediments. Resuspension of sediments under oxygenated conditions may rapidly oxidize organic matter, dissolved nutrients, and dissolved metals thereby decreasing the long term SOD once resettled. SOD is a key cause for anoxic hypolimnia in reservoirs that can cause fish kills, odors, and release of dissolved phosphorus and metals to the water column. A decrease in SOD may delay or eliminate the onset of anoxia. Sediments were collected from a eutrophic reservoir, moved to the lab and placed into aquarium tanks. Sediments were resuspended for 3 hours under both aerobic and anaerobic conditions, and then allowed to settle. SOD was then measured and samples of sediment and water were collected for component analysis. This process was repeated for additional resuspension times of 24 and 120 hours. SOD results were highly variable, but statistical analysis indicated no significant difference between aerobic and anaerobic resuspension treatments. SOD decreased an average of 39% after the 3 hour treatment, then no further decrease in SOD was observed with additional treatment. Sediment components were unchanged throughout treatment. Water quality components with the exception of Manganese increased over the course of the treatment. Nitrification was observed in the water samples of anaerobic treatment indicating some oxygen reached the intended anaerobic sediments. This indicates resuspension treatments adding very little oxygen may have caused SOD to decrease supporting further study of this proposed method.