A novel ion exchange process for As removal

The major drawback to the use of ion exchange for removal of arsenate [As(V)] from potable water is that other ions, especially sulfate (SO 4 ), compete with the As(V) for exchange sites, leading to early As breakthrough and As chromatographic peaks in the effluent. This article describes a novel approach for operating an ion exchange process in which an As(V)‐rich zone is semipermanently retained in the operating columns so that only SO 4 ‐rich resin is regenerated. When the process was used in this study, essentially all the As(V) fed to the system was retained during treatment of >36, 000 bed volumes of influent. This study also investigated the use of calcium or barium chloride salts to precipitate calcium sulfate or barium sulfate from the brine and the subsequent reuse of the brine solution. Overall, results indicate that the combination of modified column operation and brine recovery can dramatically reduce the brine requirement for As treatment by ion exchange.