Growth of three wetland plant species under single and multi-pollutant wastewater conditions

Constructed wetlands are increasingly being used to treat wastewater, yet most remediation studies only focus on single pollutants (e.g. nitrogen [N] or phosphorus [P]) or pollutant classes (e.g. nutrients). For wetland remediation to be useful in urban systems, where storm generated wastewater often contains many different pollutant types (e.g. nutrients and metals), wetlands must be able to both tolerate and remediate these pollutant cocktails. Since plants are often integral to this treatment ability, the objective of our study was to evaluate the growth of three common wetland plants (Glyceria grandis, Typha latifolia and Sagittaria latifolia) treated with single and multi-pollutant wastewater types. We planted six replicate blocks within the research greenhouse at Binghamton University located in Binghamton, NY, USA. Each block contained 12 five-gallon pots filled with homogenized wetland sediment collected from a natural wetland on campus. Four pots were planted with G. grandis, four with T. latifolia and four with S. latifolia. Plants from each of the three species were assigned with one of four treatment solutions (dionized water [control], nitrate [NO ₃ ^-], metal mixture [Zn, Cu, Pb, Cd], or nitrate and metal mixture), and watered weekly for a total of seven weeks. Effluent was collected weekly and analyzed to determine weekly NO ₃-N efflux. At peak standing biomass, all roots and shoots were harvested to determine total aboveground and belowground biomass and N and P accumulation. Sediment was also collected to determine net N mineralization rates. We found that the NO ₃ ^- treatment, metal treatment and the combined NO ₃ ^- and metal treatment had no negative effect on plant growth and nutrient (N and P) content. However, G. grandis produced a greater amount of aboveground biomass (33.09±0.72g) and had a greater amount of N (450.9±25.3mg) in the aboveground biomass than T. latifolia (22.25±1.54g; 300.0±21.8mg) and S. latifolia (24.30±1.53g; 297.1±21.3mg). While S. latifolia sequestered a greater amount of P (181.6±11.1mg) than G. grandis (127.6±8.6mg) and T. latifolia (97.1±8.9mg). In addition, efflux NO ₃-N was substantially reduced by both plants and sediment, but plant presence caused a significantly greater NO ₃-N reduction than sediment alone. These findings indicate that wetland plants can grow well under single and multi-pollutant conditions, like those commonly found in urban systems, and that optimal ecosystem function would more likely occur in systems with multiple plant species assemblages.