Microcosm fill-and-drain constructed wetlands for the polishing of synthetic electroplating wastewater

This paper presents the results of experiments on the polishing of synthetic electroplating wastewater in microcosm fill-and-drain constructed wetlands. The experimental system consisted of two types of columns (in duplicate): filled with gravel or peat/gravel mixture. All the columns were vegetated. The feed of the system contained metals (Cu, Ni, Pb and Zn), cyanides and sulfates, and was prepared to simulate the treated or pretreated electroplating wastewater. The experiment was designed to study the effect of batch duration (1 or 2 weeks), wastewater strength and the type of organic carbon source used to stimulate the activity of sulfate-reducing bacteria. It was found that the use of constructed wetlands filled with gravel and amended with external carbon source (lactates) is more advantageous than the use of system filled with peat as internal carbon source. The former type of system offers high removal efficiency for metals and cyanides. It was found that the extended batch duration promotes the removal of metals. The obtained results suggest that the increased concentration of metals in the influent corresponds to the increased removal efficiency for these metals, with the opposite observation for metals at a constant concentration in the effluent.