Flue Gas Desulfurization Wastewater Composition and Implications for Regulatory and Treatment Train Design

The U.S. Environmental Protection Agency is currently revising its regulations on trace element discharges from flue gas desulfurization (FGD) wastewater. In this work, we expand a predictive model of trace element behavior at coal-fired power plants (CFPPs) to estimate the trace element concentration of FGD wastewater at the plant level. We demonstrate that variation in trace element concentrations in FGD wastewater can span several orders of magnitude and is a function of both coal rank and installed air pollution control devices. This conclusion suggests that the benefits and costs of FGD wastewater treatment for the median plant will poorly describe the actual benefits and costs over the full range of existing CFPPs. Our model can be used to identify different "classes" of CFPPs for future regulatory and technology development efforts and to evaluate the robustness of proposed treatment technologies in light of large intraplant variability. The model can also elucidate new compliance pathways that exploit empirical and mechanistic relationships between coal concentration, trace element partitioning, and FGD wastewater composition.