Associate professor, Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, China

Speech Title: Using constructed wetlands for the treatment of saline wastewater
Abstract
Saline wastewater originating from sources such as agriculture, aquaculture, and many industrial sectors usually contains high salts and other contaminants, which adversely affect both aquatic and terrestrial ecosystems. Therefore, the treatment of saline wastewater, for both salts and specific contaminant removal, has become a necessary task in many countries. Constructed wetlands (CWs) have been successfully used for treating a wide variety of wastewaters, and are eco-friendly and cost effective, and provide a potential alternative technology for saline wastewater treatment. The objectives of this current study is to evaluate the potential use of CWs for removing N, P, and heavy metals (Cu, Zn, Cd, Cr, and Pb) from saline wastewater with different salinity levels, to clarify the impacts of different factors on the performance of CWs, and to optimize the operation parameters for obtaining an intensified performance of CWs. A series of CWs mesocosms differing in specific designs (plant species, structure and size of the mesocosms, etc) were set up, and synthetic wastewater was used in the experiments. The results were as follows: 1) CWs planted with Canna (Canna indica L.) outperformed the CWs planted with all the other tested plant species in the removal of nitrogen. There were no significant differences among plant species in the removal of P and heavy metals. However, considering the better response of growth and physiological characters of Canna to salt and pollutants stress, Canna can still be selected as the optimizing plant species. 2) The removal of N was significantly inhibited (P＜0.05) when the EC value increased by 30 mS/cm. While, the change of salinity levels didn't show significant influence on the removal of P. The change of salinity levels didn't significantly affect the removal of most of the heavy metals, either, except for Cd. 3) The removal efficiencies of CWs to some of the target contaminants was decreased when multiple contaminants were co-existed, as compared to existing in isolation. 4）The different structures of CWs lead to different removal efficiencies of each respective contaminants. In conclusion, CWs showed very promising removal efficiencies of nutrient and heavy metals from the saline wastewater, especially when the EC value of the wastewater was below 15 mS/cm. CWs were proved to be a good alternative strategy for treating saline wastewater containing high levels of nutrient and heavy metals.