Effectiveness of a Full-Scale Constructed Wetland for the Removal of Metals from Domestic Wastewater

The main objective of this study was to examine the efficacy and capacity of constructed wetlands for metal removal. Between January 2006 and December 2008, removal of Cr, Cu, Cd, Zn, Pb, B, Ni, As, Fe, Hg, and Mn was measured on a monthly basis at a hierarchical mosaic of artificial ecosystems which has been in operation since 1998. The results showed a great variety of average removal efficiencies, in the range of 55% for chromium and -73% for manganese. Four elements presented negative removal: nickel, iron, arsenic, and manganese. Seasonal removal efficiencies were also studied for each element. Moreover, a correlation assessment among metal removal efficiencies and different parameters of each basin in the hierarchical mosaic of artificial ecosystems was performed. Negative significant correlations were found among Fe, Zn, Cu, Mn, As, Ni, Cd, and Hg removal and the inlet concentrations. In general, the treatment system was not a good system for removal of metals from wastewater as, in relation to other constructed wetlands, the system was not able to provide efficient removal of metals.