DESIGN AND CONSTRUCTION OF WETLANDS FOR AQUEOUS TRANSFERS AND TRANSFORMATIONS OF SELECTED METALS

Two pilot-scale wetland cells (6.1 x 30.5 m) were integratively design ed and constructed to emphasize and enhance transfers and transformati ons of selected metals (Cu, Pb, and Zn) in an aqueous matrix. A series of preliminary experiments and analyses were conducted to select macr ofeatures (hydroperiod, hydrosoil, and vegetation) of the constructed wetland system. These wetland cells were designed to operate in series or parallel with nominal hydraulic retention times of 24-48 hr, respe ctively. With water at a depth of 30 cm, both wetland cells had hydros oil (45 cm) planted with Scirpus californicus. After 250 days of wetla nd operation, average hydrosoil redox potentials in each wetland cell decreased from +90 mV to -165 mV, and average plant height increased f rom 0.3 to 2.7 m. Aqueous samples were collected over a 4.5-month peri od at the inflow and outflow sites of the wetland cells. Average inflo w concentrations of total recoverable Cu, Pb, and Zn were 22.4, 10.5, and 565.9 mu g/L, respectively. After a 46-hr HRT, average outflow con centrations of total recoverable Cu, Pb, and Zn were 15, 2.2, and 85.9 mu g/L, resulting in removals of 33, 79, and 85%, respectively. Initi al results suggest that these constructed wetlands can be designed to remove targeted metals in wastewater. (C) 1997 Academic Press.