Variability of inorganic and organic constituents in lime spray dryer ash

Flue gas desulfurization (FGD) by-products, including lime spray dryer (LSD) ash, have many demonstrated uses. However, concern about the temporal variability in the chemical properties of this material has limited widespread utilization. To determine the variability in inorganic and representative model organic constituents, this study measured elemental composition, leaching properties, polycyclic aromatic hydrocarbon (PAH) concentrations, available lime index (ALI), calcium carbonate equivalent (CCE), and total neutralization potential (TNP) for a representative LSD ash. All parameters investigated showed little variability over different time periods (e.g., daily to yearly) and little variability between samples collected from different particle collection hoppers. Metal concentrations including As, Se, and Hg in LSD ash and in the leachate did not surpass limits for land application (EPA 503 Rule) or limits for the determination of hazardous waste as specified in the Resource Conservative and Recovery Act (RCRA). While a number of PAHs were detected, including naphthalene and phenanthrene, the levels were low and in the range of natural soils. The low variability in ALI, CCE, TNP, and inorganic and organic composition suggests that LSD ash is a consistent and environmentally benign material for agricultural and other engineering applications.