Wastewater treatment, with emphasis on nitrogen removal, in a constructed wetland planted with Phragmites australis and Glyceria maxima

Two parallel series (cascades), each of two small subsurface flow constructed wetlands designed for treatment of wastewater, were built at the highland village of Benesov (Czech Republic) during 1993. One series was planted with Phragmites australis, the other one was with Glyceria maxima. Inflow-outflow monitoring from 1997 to 1998 revealed a high hydraulic load which was connected with low removal efficiencies for organic pollution and nitrogen in this constructed wetland. No distinction could be established between the series with Phragmites and Glyceria in daily and seasonal removal efficiencies for organics and NH4-N. The efficiency of NO2-N and NO3-N removal was significantly better in summer in both series. Seasonal dynamics of removal efficiency for total N was clear only in the beds planted with Phragmites, with better removal in summer. Although aboveground biomass and nitrogen concentrations in it were high both in Phragmites and Glyceria, nitrogen standing stock represented only a small fraction of the total annual nitrogen loading of either series of treatment beds.