For inland brackish water desalination facilities using reverse osmosis, management and disposal of reject brine is a constant issue and can contribute to a significant portion of the plant operational costs. Increasing the recovery of the desalting plant would reduce the volume of produced brine, but this is not immediately possible due to the potential for precipitation of calcium sulfate on the surface of the membrane. We investigated a Hybrid Ion Exchange-Reverse Osmosis (HIX-RO) process, shown in Figure 1, to eliminate the threat to CaSO4 scaling and achieve increased recovery. Feedwater is passed through an anion exchange column in chloride form where sulfate is selectively replaced by chloride. After sulfate removal, the water can then be desalinated at higher recoveries since calcium chloride does not pose any threat to membrane scaling. Now, the concentrate stream from the RO process, concentrated chloride brine, is used to regenerate the resin. By properly designing the ion exchange column to ensure high sulfate affinity during normal operation, and high chloride affinity during regeneration, no additional chemical input is required. Results show that the HIX-RO process is able to remove greater than 90% of the influent sulfate and eliminate any threat to CaSO4 scaling all while operating the process at a previously unachievable recovery. Finally, the HIX-RO process is not limited to one type of feedwater and may be adapted to suit any composition. Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/se_sw_rm/uploads/62058_p2971j.jpg' alt='' />

Reducing the volume of produced concentrate from inland brackish water desalination plants using a Hybrid Ion Exchange-Reverse Osmosis (HIX-RO) process

248th National Meeting (2014)

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