Determination of the total iodide content in desalinated seawater permeate

An investigation was conducted to determine the iodide content of permeate collected from several operating facilities reliant upon synthetic membrane processes for seawater desalination. A possible, yet unintentional impact for communities that employ synthetic membrane processes for seawater desalination is the introduction of permeate streams containing iodide into their water supply, that then may result in the formation of iodinated disinfection by-products. To evaluate this potential, the iodide content of desalinated seawater permeate streams were measured using an analytical procedure based on the catalytic reduction of ceric sulfate by arsenious acid in a sulfuric acid solution. It was determined that iodide concentrations in permeate samples collected from seawater desalination facilities were less than the catalytic reduction method detection limit of 4.0 μg/L for membrane feed seawaters that ranged between 51.1 μg/L and 35.8 μg/L of total iodide. Results of this investigation indicated that synthetic membrane processes can remove greater than 89% of the total iodide from the feedwater of seawater based on an iodide detection limit of 4.0 μg/L.