Sizing of FWS CWs is usually based either on volume or area. Volume-based methods use a
hydraulic retention time to assess the pollutant removal while area-based methods assess pollutant
reduction using the overall wetland area [41]. In Table 2, the basic sizing criteria for BOD5, TSS and
TKN removal are given. Wallace and Knight [41] pointed out that FWS CWs are generally not
effective for phosphorus removal and only inflow loading less than 0.1 g P/m2 d would provide low
effluent concentrations.