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Modeling Bacterial Transport and Removal in a Constructed Wetland System

E. Engström, B. Balfors, and R. Thunvik
Royal Institute of Technology, Stockholm, Sweden

In this study we evaluate transport, retention and subsistence of Escherichia coli (E. coli), a common fecal indicator bacteria, in a model (2x1m) of a constructed wetland. Transport occurs in the unsaturated and saturated zone. Inactivation is accounted for as a kinetic first-order process. Retention is assumed to be dominated by solid-air-water interface straining and is modeled with a kinetic equation. The relative effluent concentration (C/C0) equals 1.8 log10 at the system outlet. A forward sensitivity analysis shows that results are highly dependent on water infiltration rates and assumptions on E. coli retention rates. The governing, coupled equations of unsaturated media flow and bacterial transport were solved using COMSOL Multiphysics.