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PM08 Sediment Quality Assessment
(PM124) Development of a numerical model to predict sediment storage of fecal bacteria and transport in a river.
Davis, III, J1, Finke, J1, Paily, P.1, Sharpe, L.1, Watson, V1, Byl, T1, 2, 1 Tennessee State University, Nashville, TN, USA2 USGS, Nashville, TN, USA
ABSTRACT- Fecal pollution in surface waters is a serious water-quality problem. As a result, scientists have developed a number of models in an attempt to predict the fate and transport of fecal pollution in riverine systems. Various models predict the rate of bacteria removal from the water column based on density, settling rates and water velocity. Such models, however, do not consider survival and reproduction of bacteria in sediments, or re-suspension. Flume and stream experiments were conducted to measure the survival, reproduction and resuspension of fecal bacteria in sediments. These results will be used to modify a numerical model by incorporating survival of bacteria in bed sediments and re-suspension into the water column, in addition to other parameters such as water velocity, initial bacteria concentration, and settling rate. E. coli and Klebsiella were introduced into the circulating-water flume at known concentrations and monitored as they settled or remained suspended. Bacteria concentrations were measured in the water column and the sediment along the flume to determine bacterial fate and transport. The model accurately predicted bacteria settling from the water column. The sediment fecal bacteria population declined at an exponential rate over several weeks (experimental decay value = -0.2735). This decomposition rate was coupled to the numerical model and additional tests were done in a small stream contaminated with fecal coliform. Comparison of the model and stream data were mixed due to irregular resuspension of bacteria-contaminated sediments. Additional work is needed on factors that control resuspension of sediments.
Key words: fecal bacteria, transport model, sediments, resuspension
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