Influence of hydraulic loading rate and recirculation on oxygen transfer in a vertical flow constructed wetland.

The oxygen transfer rate (OTR) has a significant impact on the design and operation of vertical flow constructed wetlands (VFCWs) intended for organic matter removal and nitrification. Despite its key role, the information on real oxygen input in VFCWs is limited, being usually estimated by mass balance (stoichiometry), through which is calculated only the oxygen consumption rate (OCR). In this study, for the first time, the gas tracer method was applied to evaluate the oxygen transfer capacity of a real-scale VFCW (24.