Fundamental challenges and engineering opportunities in flue gas desulfurization wastewater treatment at coal fired power plants

In November 2015, the United States Environmental Protection Agency (EPA) promulgated the Effluent Limitations Guidelines (ELGs) for the Steam Electric Power Generating Sector. These guidelines either eliminate or lower permissible discharge limits for six wastewater streams produced at coal fired power plants (CFPPs), including flue gas desulfurization (FGD) wastewater. This paper summarizes the state of the art, describes fundamental challenges, and highlights critical research needs in FGD wastewater treatment. We begin by describing the processes that influence FGD wastewater production and composition. We then critically evaluate the best available technologies for treating FGD wastewater identified by the EPA during the regulatory process. Finally, we identify four critical challenges and research needs in complying with the 2015 ELGs including (1) removing selenium species from FGD wastewater, (2) achieving zero liquid discharge of pollutants from FGD wastewater while enabling water reuse at CFPPs, (3) developing water treatment systems that can respond to short-term fluctuations in CFPP electricity generation and wastewater production, and (4) optimizing the balance of capital and operational costs for FGD treatment when the power plant lifespan is uncertain.