Polishing of Real Electroplating Wastewater in Microcosm Fill-and-Drain Constructed Wetlands

This chapter presents a study of the performance of metals removal mechanisms in microcosm fill-and-drain constructed wetlands used for polishing of real-life electroplating wastewater. Two types of columns were used in the experiment: with compost or sand bed media. All the columns were planted with common reed. The main design goal of the experimental system was to promote precipitation of metals with biogenic sulfides. The feed of the system contained mainly metals (Al, Cu, Ni, Zn), B, and cyanides. The substrate from the columns was sampled after cessation of the experiment (56 weeks) and was analyzed using a sequential extraction procedure and a scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS) method. The studied columns were found to remove Al, Cu, and cyanides to a high extent, but were less efficient for other metals and B. The obtained results showed that the intended process for metals removal, which was the precipitation of metal sulfides, was responsible for binding only a minor fraction of metals. The major portion of metals was present as exchangeable or reducible fraction.