Clemson University is evaluating specifically designed pilot-scale constructed wetland treatment systems for treatment of targeted constituents in coal-fired power plant flue gas desulfurization (FGD) wastewater. Relatively large volumes of wastewater (0.5 – 3 MGD) are generated by coal-fired power plants during the process of FGD. During this process, potentially problematic elements (e.g. selenium (Se), mercury (Hg), arsenic (As), etc.) are entrained in the water in both particulate and aqueous phases. After separation of gypsum (CaSO₄, formed in the scrubbing process), the residual wastewater or process water contains constituents that must be treated prior to discharge of the water to receiving aquatic systems. Physical or chemical alternatives for treatment may not be effective from the perspective of capital, operating, or maintenance costs as well as sustained performance. A pilot-scale constructed wetland treatment system is being designed and constructed at Clemson University to evaluate removal of mercury, selenium, and other constituents from FGD wastewater.

The overall objective of this project is to decrease targeted constituents, Hg, Se, and As, in FGD wastewater to achieve discharge limitations established by NPDES and CWA. Specific objectives of this research include: measuring performance of the treatment system in terms of decreases in targeted constituents; determining how the treatment is achieved (determining reactions and rates); and measuring the performance in terms of decreased bioavailability of these elements.