Increased phosphate concentrations in rivers and streams throughout the Great Lakes region have been of major concern for decades. Along with the non-point source of agricultural runoff that adds excess nutrients (nitrogen and phosphorus) into surface water, the sewage treatment plant (STP) acts as a major point source, which discharges effluent with a significant amount of phosphates into creeks and streams that comprise the watersheds of the Great Lakes region. Prior research showed that utilizing aquatic species is a promising alternative to control eutrophication by retaining nutrients before its discharge to surface water. Our ultimate goal is to create a low cost, ecologically safe treatment system for the STP effluents by developing phytoengineered constructed wetlands with native plant species, which have high potential for retaining phosphates. The current study, which is the logical first step towards achieving this long-term goal, aims to i) determine the concentration gradient of total phosphorus (TP) upstream and downstream of a sewage treatment plant in Lima, N.Y. along Spring Brook stream, a tributary of the Genesee River, which feeds Lake Ontario; and ii) investigate the comparative effectiveness of two native cattail species, Typha latifolia and Typha angustifolia in removing TP from the Spring Brook water.
Results/Conclusions
Results showed that water samples collected from Spring Brook, both upstream and downstream of the STP, showed a significant (p=0.0002) elevation in the total phosphorus (TP) level immediately downstream of the discharge point. Although the surroundings of the stream are mostly rural with some farmland, a non-point source for phosphorus and nitrogen, the increase in phosphates just after the sewage treatment plant outfall suggest that this is a point-source of excess phosphate in the stream, which eventually leads to the Great Lakes. The second part of the study, which aims to determine the comparative effectiveness of broad leaf and narrow leaf cattail species, is currently ongoing in our plant growth chamber under controlled conditions. Three replicates of either of these two species, along with no-plant controls, are set up in 27 hydroponic tanks with three initial TP concentrations, a no P control, and Spring Brook water collected from the upstream and the downstream of the STP. The comparative effectiveness of these species in retaining TP from highly trophic water is an important part of helping to determine an economic and feasible solution for municipalities to decrease phosphate concentrations in waters that receive STP effluents, and reduce the potential for eutrophication.