Removal of Heavy Metal Elements and Nutrients by Pontederia cordata and Phragmites australis Constructed Wetlands

For studying the potential applications of Pontederia cordata L.as a constructed wetland plant,the removal effects of P.cordata and Phragmites australis Trin.ex Steud.on nutrients and heavy metal elements in the wetlands were compared.Mono-cultivated small-scale wetlands were constructed using pots(80 cm-50 cm-45 cm,the upper diameter-bottom diameter-high).The results showed that the removal rates for TN and BOD5 by P.cordata was significantly higher than those by P.australis(P 0.05).But there was no significant difference between them for the removal of Cd2 + and Pb2+.Content distribution of Cd2+and Pb2+ in both plants was as follows: root stem leaf.For both the wetlands,there was little difference in nutrient removal between hydraulic retention time(HRT) of 2 d and 7 d,but heavy metal removal rate at HRT of 7 d was significantly higher than that at HRT of 2 d,indicating that the removal of heavy metals was slower than that of nutrients in the constructed wetlands.These results suggest that P.cordata has a good application potential in constructed wetlands because of its good visual effects and high removal rates for wastewater pollutants.