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.