Modeling Biofilm Dynamics in a Constructed Wetland Wastewater Treatment System

A review of modeling approaches for simulation of wastewater treatment in vegetated subsurface bed (VSB) systems is presented. A multi-scale biofilm-based model that includes substrate utilization both in bulk liquid and the biofilm is formulated and described. The model accounts for transport of substrate in the liquid phase, and growth and decay of biomass in suspension and in the biofilm. Dynamic changes in porous media hydraulic flow, combined with attachment and detachment of biomass are considered. Natural precipitation and evapotranspiration are also considered. Field application of the model along with a survey of the parameters is presented and performance of the model for simulation of organic matter removal and clogging is assessed. The mechanistic model simulates the performance of a constructed wetland treating wastewater very well, and has potential for use in design of constructed wetland systems.