Biogeochemical Cycling of Mercury, Selenium, and Arsenic in a Pilot Constructed Wetland for Wastewater Treatment

EPA Grant Number: F5A17255
Title: Biogeochemical Cycling of Mercury, Selenium, and Arsenic in a Pilot Constructed Wetland for Wastewater Treatment
Investigators: Sundberg, Sarah E.
Institution: Clemson University
EPA Project Officer: Zambrana, Jose
Project Period: August 1, 2005 through August 1, 2007
Project Amount: $111,000
RFA: GRO Fellowships for Graduate Environmental Study (2005) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


The purpose of this doctoral research project is to evaluate the complex biogeochemical cycling of mercury, selenium, and arsenic in a constructed wetland treatment system (CWTS) specifically designed to treat flue-gas desulfurization (FGD) wastewater from fossil-fueled power plants. These three constituents of FGD wastewater are recognized as toxicants of concern, and their discharge into the environment is monitored by the National Pollution Discharge Elimination System (NPDES). Prior to field application, a pilot-scale study must be completed to determine the effectiveness and reliability of the treatment system as well as to develop rate coefficients and other information needed to scale-up to the full-scale treatment system.

The overall objective of this project is to utilize the various biogeochemical processes occurring in the pilot-scale system to decrease mercury, selenium, and arsenic concentrations in simulated and actual FGD wastewater to achieve discharge limitations established by the NPDES and Clean Water Act (CWA).


Pilot-scale wetland treatment systems provide excellent research opportunities in areas of the biogeochemical behavior in sediments, plant uptake, concentration, and distribution, and toxicity of sediment and detritus contaminated with FGD wastewater. The specific objectives are:

  1. To characterize the operationally-defined fractions of Hg, Se, and As associated with sediment in the CWTS using sequential fractionation procedures,
  2. To estimate the non-competitive and competitive binding potentials of Hg, Se, and As in a sediment with similar characteristics as the sediment utilized in the CWTS,
  3. To measure the concentrations of Hg, Se, and As in roots, submerged shoots, emerged shoots, and seeds of representative Schoenoplectus californicus and Typha angustifolia collected from the CWTS,
  4. and To measure the responses of Hyalella azteca Saussure, an aquatic detritivore, to sediment and non-living plant biomass from S. californicus and T. angustifolia contaminated with FGD wastewater in the CWTS over a 10-day exposure duration.

Expected Results:

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. In addition to contributing to the fundamental knowledge of the biogeochemistry of mercury, selenium, and arsenic, t his 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.

Supplemental Keywords:

constructed wetland, mercury, selenium, arsenic, wastewater,, Scientific Discipline, Water, TREATMENT/CONTROL, Wastewater, Environmental Chemistry, Environmental Engineering, Water Pollution Control, wastewater treatment, industrial wastewater, mercury, flue gas desulfurization, biogeochemical cycling, Selenium, fossil fuel plants, constructed wetlands, aqueous waste stream

Progress and Final Reports:

  • 2006
  • Final