Modelling pollutant removal in a pilot-scale two-stage subsurface flow constructed wetlands

The hydraulic behaviour and effluent pollutant concentrations in a pilot-scale two-stagesubsurface flowconstructedwetland for treatment ofmunicipalwastewater have been simulated.The experimental pilot plant is located in San Michele di Ganzaria (Eastern Sicily)and consists of four lines of two-stage subsurface flow constructed wetlands for secondaryor tertiary treatment of municipal wastewater. The first stage, for each line, consists of ahorizontal flow bed, while in the second stage a vertical flow bed operates for two linesand a horizontal flow bed for the other two. Phragmites sp. was used as vegetation in twolines while the other two lines are without plants. The HYDRUS-2D software was appliedto describe flow and single-solute transport, while the multi-component reactive transportmodule CW2D was used to model the transformation and elimination processes of organicmatter, nitrogen and phosphorus. Tracer studies and chemical wastewater analyses werecarried out to calibrate and validate the transport model. In general, the simulation resultsobtained show a good match with the measured data for water flow, tracer experiments andpollutant removal processes.