Performance predictions of mature experimental constructed wetlands which treat urban water receiving high loads of lead and copper

The treatment efficiencies of vertical-flow wetland filters containing macrophytes and granular media of different adsorption capacities were investigated. Different concentrations of lead and copper sulphate were added to urban stream inflow water in order to simulate pre-treated (pH adjustment assumed) mine wastewater. After 1 year of operation, the metal mass load rate was increased by a factor of approximately 4.6. No breakthrough of metals was recorded. The use of macrophytes and adsorption media did not enhance heavy metal reduction significantly after 13 months of operation. A correlation analysis indicated strong positive correlations between conductivity on one side and other variables including temperature, total solids, dissolved oxygen and the redox potential on the other side. Some expensive or time-consuming variables (e.g., biochemical oxygen demand) can be predicted with less expensive ones (e.g., dissolved oxygen and temperature). The associated absolute mean errors were <10%.