(717b) Treatment and Mineral Recovery from Combustion Residual Leachate and Produced Water

Critical minerals are key to a successful energy transition in the United States. Domestic sources of these minerals would increase energy security and enable more rapid decarbonization. Wastewater from fossil fuel sources contains varying amounts of critical minerals. This study analyzes two of these sources: leachate from coal combustion residual landfills and impoundments and produced water from unconventional sources. Treatment scenarios to facilitate mineral recovery via volume reduction were considered. Based on total dissolved solids, a membrane treatment system was analyzed for leachate, and a mechanical vapor compression system was considered for produced water. The Water Treatment Techno-economic Assessment Platform (WaterTAP) package in Python and the costing method developed by Process Optimization and Modeling for Minerals Sustainability (PrOMMiS) were used to analyze the cost and performance of both systems, whereas OLI Studio and Flowsheet enabled detailed electrolyte chemistry and brine analyses for both systems. The Combustion Product Information database published by the Electric Power Research Institute provided detailed constituent data for landfill and impoundment leachate, and the United States Geological Survey database on produced water provided by the National Energy Water Treatment Speciation database assisted with produced water analyses.
Treatment scenarios considered in this work calculated a range of levelized cost of water values (based on the flow rate of clean water) between $1.85 and $15.45/m³ for combustion residual leachate and between $14.20 and $24.10/m³ for produced water in 2023 dollars. The value of the resultant brine was between $1.64 and $15.99/m³ for leachate and between $6.52 and $34.87/m³ for produced water. In both cases, this value was primarily dependent on the value of lithium and magnesium in the feed. Based on these values and the resultant recovery percentages (95% for leachate and 50% for produced water from the Permian Basin), treatment for the sake of recovery is suggested only for produced water. Magnesium recovery from water is already performed industrially for seawater and other brines. Direct lithium extraction will be considered in future work.