Common reed (Phragmites spp.), or called in short ?reed?, is widely used as dominant vegetation in constructed treatment wetlands. In the context of the debate about the role of the reed in removing phosphorous and nitrogen, this paper presents the result of two parallel experiments. The first experiment is aimed at surveying the biomass increase of reed in time and the percentage of accumulated total phosphorous (P) and total Kjeldahl nitrogen (N) in their body. In the second experiment the P and N balances are established in pots. The wastewater used in the experiments was taken from different treatment stages of an experimental subsurface flow wetland located at the Can Tho University, Vietnam.

The experiment results have shown that more than 60% of the total phosphorous and 90% of the total Kjeldahl nitrogen is removed through adsorption in the sand (23 to 48% P and 0.8 to 1% N) and through up-take in common reed plant and root systems (1 to 12% P and 22 to 76% N). These removal percentages fit the results of previous reports. It may be concluded that reed as a macrophyte species plays a certain treatment role wastewater in constructed wetland, but predominantly for nitrogen removal.