PARENT SESSION
1E Biologically based risk assessment and risk management
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/EH044) Constructed wetland design for decreasing bioavailable copper in an aqueous matrix.

Rodgers, John¹, Murray-Gulde, Cynthia¹, Heatley, John¹, Schwartzman, Adam¹, Huddleston, George¹, ¹

ABSTRACT- This study provided design information for a wetland system recently constructed for treatment of copper-contaminated wastewater. Design involved theoretical and physical modeling of the constructed wetland system, with the primary objective of poising the system to limit copper bioavailability. The physical model (wetland mesocosm system) consisted of five pairs of wetland cells (378 L), each pair arranged in series with a 48-h hydraulic retention time (HRT). Four pairs received municipal water amended with CuSO₄⋅5H₂O at a nominal concentration of 50 g/L, while one pair received only municipal water. Wetland hydrosoil was 85% sand, 15% silt, and 5% organic matter. Hydrosoil depth and overlying water depth were 30 cm each. Wetland vegetation was giant bulrush, Scirpus californicus (C. Meyer) Steud. Performance objectives for the system were to decrease total acid soluble copper to <22 g/L and to eliminate toxicity (Ceriodaphnia dubia; 7-d/static/renewal). Parameters indicative of wetland function included hydrosoil redox potential and acid volatile sulfide (AVS) formation. Evaluation of the wetland mesocosm system began in spring 1999 and continues. Total acid soluble copper concentrations in wetland inflow averaged 46 (±9) g/L, while outflow concentrations were 12 (±7) g/L following a 48-h HRT. Overall copper removal from water was 73% (±14). Copper in inflow water was toxic to C. dubia, while no toxicity was observed in outflow water after the system stabilized. Hydrosoil redox potential and AVS indicated that the system was poised to limit bioavailable copper, with no adverse seasonal effects on wetland performance.

Key words: constructed wetland, copper, acid-volatile sulfide, Scirpus californicus