Removal of Trace Uranium from Groundwaters Using Membrane Capacitive Deionization Desalination for Potable Supply in Remote Communities: Bench, Pilot, and Field Scale Investigations

The performance of membrane capacitive deionization (MCDI)desalinationwas investigated at bench, pilot, and field scales for the removalof uranium from groundwater. It was found that up to 98.9% of theuranium can be removed using MCDI from a groundwater source containing50 & mu;g/L uranium, with the majority (94.5%) being retained onthe anode. Uranium was found to physiochemically adsorb to the electrodewithout the application of a potential by displacing chloride ions,with 16.6% uranium removal at the bench scale via this non-electrochemicalprocess. This displacement of chloride did not occur during the MCDIadsorption phase with the adsorption of all ions remaining constantduring a time series analysis on the pilot unit. For the scenariostested on the pilot unit, the flowrate of the product water rangedfrom 0.15 to 0.23 m(3)/h, electrode energy consumption from0.28 to 0.51 kW h/m(3), and water recovery from 69 to 86%.A portion (13-53% on the pilot unit) of the uranium was foundto remain on the electrodes after the brine discharge phase with conventionalcleaning techniques unable to release this retained uranium. MCDIwas found to be a suitable means to remove uranium from groundwatersystems though with the need to manage the accumulation of uraniumon the electrodes over time. Theuse of membrane capacitive deionization (MCDI) for theremoval of uranium from groundwater is examined with attention givento the impact of varying groundwater compositions and MCDI operationalconditions on uranium removal.