Evaluation and Management of the Impact of FGDs on Wastewater

摘要

Volatile trace elements such as mercury and selenium may be captured in a wet flue gas desulfurization (FGD) system, and would be eventually discharged in either the FGD solids and/or water discharge. EPRI is characterizing trace element concentrations in FGD water. Mercury can be present as either a dissolved and/or a particulate phase. The "dissolved" phase may include mercury associated with fine particles, and the fraction of dissolved mercury may vary significantly from site to site. The fraction of dissolved mercury is critical in developing water treatment options for mercury. Selenium is present in multiple forms, including selenite, selenate, and unknown selenium compounds. Selenate and the unknown selenium compounds appear to be more difficult to treat using traditional iron coprecipitation. EPRI is evaluating various treatment options to remove all forms of selenium as well as to effectively remove mercury. Laboratory studies evaluated a number of treatment approaches. The results from two iron-based approaches have shown promise for selenium and/or mercury removal from FGD wastewaters.