A Laboratory Experiment System for Developing Mine Drainage Treatment Technologies Using Constructed Wetlands—Sequencing Batch Treatment of Cd-Containing Neutral Mine Drainage—

A lab-scale experimental system accommodating soil and plants was designed to evaluate the applicability of constructed wetlands (CWs) to mine drainage treatment. Synthetic wastewater containing Cd (0.11 mg/L) and other minerals (pH 6.8) was prepared based on the chemical composition of an actual neutral mine drainage (NMD). In lab-scale CWs consisted of a column (ID 12.5 cm, H 50 cm) filled with pumice stones and loamy soil were planted reed (Reed-CW) or cattail (Cattail-CW) plants. Some were left unplanted (Unplanted CW). The synthetic NMD (2.0 L) was treated in a 1-week cycle sequencing batch mode in the CWs in a greenhouse. The unplanted CW removed cadmium sufficiently to satisfy the effluent standard (0.03 mg/L) from the NMD, mainly by soil adsorption. Presence of the emergent plants, especially cattail, enhanced metal removal possibly by filtration with their elongated roots and metal sulfide precipitation by sulfate-reducing bacteria in the rhizosphere of the Cattail-CW.