Simulation of Microbial Transport in the Unsaturated Zone

Modeling microbial matter has mostly focused on transport of viruses, which – relative to bacteria and protozoa – are the smallest particles.  As such, viruses are least likely removed by mechanical filtration processes. In fact, there are many factors influencing the transport and fate of microbial matter. In the case of viruses, their inactivation rate is considered the single most important parameter in groundwater systems, which is often slower than the rate of die-off of other pathogens, such as infectious bacteria.  However, there is not yet a consensus on which factor(s) have the greatest impact on eliminating microbial matter in general.  The presentation focuses on using the HYDRUS model in combination with laboratory virus transport studies to investigate which factors have the greatest influence on the transport of these particles in natural or engineered soil treatment units (STUs) under unsaturated flow conditions.  The HYDRUS flow domain is an approximation of a standard STU, consisting of a drainage channel that is partially surrounded by a biofilm layer, which separates it from the surrounding unsaturated sediment.  Both, the attachment/detachment model and filtration theory will be tested to delineate which approach better addresses the transport data generated in parallel laboratory experiments.