Numerical simulation of bacteria and virus transport in mobile bed channels

Pathogen transport in irrigation canals was simulated via a one-dimensional hydrodynamic and sediment transport model. The governing equations are St. Venant for sediment-laden flow and convection and a diffusion equation for pathogen transport in water and sediment. The first-order kinetic theory was applied to estimate the die-off and growth of a pathogen in water and sediment. The coupled equations were solved numerically via the HLLC approximate Riemann solver. The model was verified via laboratory experimental data from Escherichia coli (E. coli), Bacteriophage MS2 (MS2), and Enterobacteria phage PhiX174 (PhiX174). A comparison of the simulated and measured pathogen concentrations revealed that the number of pathogens in the water increased sharply with increasing shear stress and reached a constant value at a given flow discharge. These results suggest that pathogen concentrations in water are influenced by flow dynamics and sediment on the bed, especially pathogen entrainment and transport with sediment load.