Parametric Study of Fate and Transport Model of E. coli in the Nearshore Region of Southern Lake Michigan

Forecasting the level of waterborne bacterial pathogens (E. coli as indicator) in recreational waters using a deterministic model has been a very effective tool for water quality prediction and management. The fate and transport of pathogens in water is a complex process controlled by various factors of hydrodynamics, hydrology, chemistry, and microbiology. To better understand the importance of these factors and their roles in the inactivation, transport, and removal of pathogens, it is extremely important to enhance the reliability and effectiveness of a model by increasing the accuracy of simulation and prediction. This paper reports the results of sensitivity analyses on each of these factors using a calibrated hydrodynamic model coupled with a water quality model for temperature variation and E. coli transport. A nearshore region in southern Lake Michigan was used as the modeling domain in this research. Based on the sensitivity analysis method of differential analyses coupled with one-at-a-time design, the results show that the sensitivity of the different parameters can be ranked in decreasing order as follows: solar insolation, temperature correction factor, dispersion coefficients, tributary loading, wind velocity, and settling velocity. More detailed investigation of sunlight-related parameters using Chapra's formula shows that t(90) is predominant over other factors on E. coli inactivation caused by insolation. The sensitivity of sunlight-related parameters can be ranked in decreasing order as follows: t(90), theta(d), k(e), alpha, and theta(l). The model used in this study, together with the sensitivity analysis results, can be used as a reference for similar pathogen transport investigations in other freshwater bodies. (C) 2013 American Society of Civil Engineers.