Date of Award
Doctor of Philosophy (PhD)
Engineering Science (Interdepartmental Program)
Richard L. Bengtson
A biological model, ECOLI, is developed that is capable of continuously simulating E. coli concentration in surface runoff from agricultural land applied with manure. The model was calibrated and validated by using data from field-scale studies at Franklinton, Louisiana. During validation the model was interfaced with GLEAMS-SWT model to obtain the necessary hydrologic and erosion variables as input to the ECOLI model. The ECOLI model was found to perform best when simulating runoff concentration following the first application of waste. For reapplication of waste within 50 days, the trend of decrease over time was well-simulated but simulated E. coli concentrations were lower than the observed concentrations. The correlation coefficient of the simulated E. coli concentration versus the observed concentration was found to be 0.85. The regression intercept is significantly different from zero. The regression slope is 1.06 and is not significantly different from 1.0. The ECOLI model is not recommended for reapplied waste until more research is done on the effect of applied waste on subsequent E. coli density and decay. The ECOLI model is also not recommended for use in simulating fecal coliform concentration unless methods of enumerating fecal coliforms that exclude false positive counts are used. Two experiments were carried out to investigate E. coli adsorption in soil-water system of Tangi Silt Loam and Commerce Clay Loam. The adsorption of E. coli in Tangi Silt Loam was found to be significantly lower than that of Commerce Clay Loam. The distribution coefficient of loose adsorption of E. coli in Tangi soil water system was found to be significantly lower than that of tight adsorption. The distribution coefficient of loose adsorption of E. coli in Commerce soil-water system was found to be significantly higher than that of tight adsorption. Soil with higher clay content was found to adsorb significantly more E. coli than soil with lowerer clay content. Together with literature data, a high correlation (R2 = 0.89) was found between adsorption and clay content. Significant correlation (R2 = 0.67) was found between distribution coefficient and clay content. The relationships developed may be used in modeling purposes.
Ling, Teck Yee, "Modeling Escherichia Coli Concentration in Surface Runoff: the ECOLI Model." (2000). LSU Historical Dissertations and Theses. 7279.