| As fossil-fueled power plants attempt to comply with the Clean Air Act and Clean Water Act, cost-effective and ecologically-sound wastewater treatment systems such as constructed wetlands are being utilized across the nation. This research evaluated the partitioning and toxicity of Hg, Se, and As in a constructed wetland treatment system (CWTS) used to treat flue gas desulfurization (FGD) wastewater. The overall objective of the constructed wetland was to remove Hg, Se, and As from the receiving inflow by immobilizing these constituents within the wetland in order to achieve discharge limitations established by the National Pollution Discharge Elimination System (NPDES). In addition to treatment performance, it is essential to understand how performance is achieved, and the overall risks associated with the system and the incorporated processes to the surrounding ecosystem after treatment. Objectives were to (1) characterize the partitioning of Hg, Se, and As between water and detritus from the CWTS and consequent toxicity to Hyalella azteca Saussure, a common aquatic detritivore, (2) characterize sorption, root:shoot transfer, and bioconcentration of Hg, Se, and As in Schoenoplectus californicus and Typha angustifolia, (3) characterize the partitioning of Hg, Se, and As to sediment and consequent toxicity to H. azteca, and (4) categorize sediment-associated Hg, Se, and As into operationally-defined geochemical fractions using previously-developed sequential extraction procedures. In addition to contributing to the fundamental knowledge of the biogeochemistry of Hg, Se, and As, this research is essential to understanding the intricacies of constructed wetland treatment systems, as well as properly implementing these systems in the environment to effectively treat industrial wastewater. |
