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Another treatment option which is in experimental stages is the use of halogen-impregnated resins.
Halogens, as a group, are strong oxidizing agents. They include fluorine, chlorine, bromine and iodine. Experimentation with disinfection by iodine- and bromine-impregnated resins is underway. Disinfection of water in emergency situations has long been recommended with iodine. For routine disinfection, however, control has been a problem. Iodine is normally a solid and bromine a liquid. They may be dissolved in water or other liquids but are not nearly as easily lost from solution as chlorine, ozone and other gases are. Because of this there is no need to determine a breakpoint for the process.If too much is added it is very difficult to remove the excess and even small amounts of free iodine produce a strong taste. But if the iodine reacts with pathogens or other contaminants in the water, it is no longer free and the taste is gone. Resin promises to solve the problem of free iodine by releasing only the amount of iodine needed for reaction.
Iodine and bromine resins are used much like an activated carbon filter. Water is passed through the media and contaminants react with the iodine or bromine, but the iodine or bromine is not free to move into solution easily. The system looks promising, but the treatment is so new that little information is available. Questions concern how long the resin would last in a particular situation and the potential health hazard the procedure might pose for certain individuals. Persons on restricted-iodine diets may not be able to drink iodine-treated water on a routine basis, and similar problems may exist for bromine.
The advantage of these other halogens is that they have been found to be more effective killing agents than chlorine derived reagents. The disadvantages are that they are more expensive to use and tend to impart certain color, taste and odor problems if used in excess.