EVALUATION AND PREDICTION OF METAL REMOVAL BY NATURAL AQUATIC SYSTEMS

Pilot-scale surface-flow (SF), subsurface-flow (SSF), and floating aquatic plant (FAP) constructed wetland system designs were installed and evaluated to determine the effectiveness of constructed wetlands to remove metals such as cadmium, zinc, copper, chromium, lead and nickel in tertiary effluent wastewater in a Midwestern U.S. climate (central Illinois). Following wetland treatment, average concentrations of copper decreased from 45.6 μg/l in influent to 6.5 μg/l (85.7% reduction) in the FAP system, 6.7 μg/l (85.3% reduction) in the SSF system and 6.1 μg/l (86.6% reduction) in the SF system, respectively. Results of ANOVA indicated that differences in concentration reduction of copper among the three wetlands were not statistically significant. The average concentration of chromium and lead decreased at 50% or more in all system designs. Phospholipid fatty acid (PLFA) analysis was used to characterize microbial communities within each wetland system. Artificial neural networks were also trained to model metal removals under different flow and loading conditions. The determination coefficient (R2) between measured and predicted C/Co was found to be 0.67, 0.68, 0.72, 0.67, and 0.65 for copper, zinc, chromium, lead and nickel, respectively.