Treatment strategies for displaced waters from the planned Rock Springs Uplift carbon dioxide (CO2) geologic sequestration site

Developing effective management strategies for greenhouse gases, such as carbon dioxide (CO2), is receiving growing interest as concerns over their role(s) in affecting global climate change develop. Geologic sequestration has been identified as one possible avenue for storing CO2, which would otherwise have been discharged to the atmosphere. The Rock Springs Uplift (RSU) in southwestern Wyoming has been identified as a candidate site for geologic sequestration of CO2. The RSU site contains two deep saline aquifers into which CO2 can be injected and stored: The Weber Sandstone and Upper Madison Limestone Formations. Sequestration of CO2 into these two formations is expected to displace approximately 700,000 gallons per day of highly saline water (avg. total dissolved solids ~95,000 mg L -1). For geologic sequestration to be successful, or even a practical option at the RSU site, the displaced water must be managed in such a way so that the carbon balance (CO2 sequestered -- CO2 produced during treatment) is favorable and economics affordable. Three distinct water treatment alternatives were developed for managing and facilitating the beneficial reuse of the displaced water at the RSU site and included: desalination using forward osmosis, desalination using mechanical distillation and disposal using wind-aided evaporation. A present worth cost calculation for each alternative was developed which included the capital cost and the yearly operation and maintenance cost. The carbon footprint expected from each alternative was also evaluated. Both the present worth cost and carbon footprint should be considered when determining the most appropriate treatment alternative for this water.