Disinfection capacity of seven constructed wetlands and ponds

The disinfection performance of three subsurface flow constructed wetlands (SSF), a free-water surface-constructed wetland and three ponds were investigated. They functioned as advanced treatment stage following treatment in a large municipal wastewater treatment plant equipped with nutrient removal. Despite low influent concentrations of 10^3.9/100 mL, Escherichia coli underwent a reduction of 1.7 (ditch) to 2.3 (sandy loamy SSF) orders of magnitude. After passing through these treatment plants E. coli was lowered sufficiently to within the permitted levels thus allowing it to be used in drip irrigation of fruits and vegetables. The change of seasons and hydraulic loading (in the range of 50–150 mm/day) as well as short-term overloadings did not impact the effluents' quality.