Performance of vertical sub-surface flow constructed wetlands planted with Thallia dealbata for mercury removal

This study focused on evaluating the efficacy of vertical sub-surface flow constructed wetlands for mercury (Hg) removal. Aquatic plants were investigated through the hydroponic tests for their Hg enrichment efficacy in three experimental solutions containing nutrients and Hg (50 mu g/L, 100 mu g/L, 200 mu g/L). Thalia dealbata revealed the best results among investigated plant species and selected for further experiments. Results revealed effective absorption of Hg in Thalia dealbata roots, accounted for over 50 % the total Hg uptake by plants. Removal efficiency of total mercury (THg) and particulate mercury (PHg) from planted and unplanted wetlands (CW-1 and CW-2) with similar filter media and hydraulic conditions such as hydraulic retention time (HRT) was further investigated in this study. Results revealed that THg and PHg removal mainly occurred in first quarter section of the CW-1 (82.1-87.3 % and 80-89.5 %, respectively). Dissolved mercury (DHg) decreased uniformly along the substrate in CW-1, with a removal rate of 81.1-94.1 %. Overall, removal rates of THg, PHg and DHg in CW-1 were quite higher as compared to CW-2. Current study could provide an alternative for the eco-restoration of Hg contaminated water bodies.