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SELENIUM REMOVAL FROM DRINKING WATER BY ION EXCHANGE
Maneval, J., G. Klein, AND J. Sinkovic. SELENIUM REMOVAL FROM DRINKING WATER BY ION EXCHANGE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-85/074.
Strong-base anion exchangers were shown to remove selenate and selenite ions from drinking water. Because selenium species are usually present at low concentrations, the efficiency of removal is controlled by the concentration of the common drinking water anions, the most important being sulfate. The ion-exchange behavior of selenate was found to be identical to that of sulfate, while the behavior of selenite was found to be similar to that of nitrate. The local-equilibrium theory for ion-exchange columns produced good results in predicting selenium removal capacities. Two alternative methods of selenium removal were also investigated. Attempts to find reagents, compatible with water treatment, that were capable of reducing selenate to selenite (for which there are selective removal methods) were unsuccessful. Screening experiments showed that a weak-acid cation exchanger in the ferric form selectively removed selenite from water containing the common drinking-water anions.