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Investigations of iodine species distribution of various aqueous solutions of iodine disinfectants and water from equilibrated suspensions of triiodide and pentaiodide resins were done at the University of Colorado for the Center for Space Environmental Health during 1992 and 1993. Direct measurements of three individual iodine species: I-, I2 and I3-, were made. In addition three measures of total titratable iodine species were used. It has been found that I2 and I3- solutions produce a significant fraction of the non-disinfecting species iodide (I-), ranging from 50 to 80% of added iodine, respectively, at pH values of approximately 5. Correspondingly, I2 solutions produce more than twice the concentration of disinfecting iodine species per mass iodine dose than I3- solutions. Both I- and I2 species were found in aqueous extracts of pentaiodide resin, although no soluble species were detected with triiodide resin.

The reaction of iodine, a potential disinfectant for use in the treatment of recycled water during long-duration manned space missions, and several organic substrates that are expected chemical constituents in a closed-loop recycle water system, yields iodinated disinfection by-products. The reactions were studied using procedures analagous to those developed by the U. S. Environmental Protection Agency for evaluation of chlorinated disinfection by-products in water. The iodinated products formed in these studies were identified using gas chromatography with both electron capture and mass spectrometric detection. Aqueous solutions of acetic acid and of dextran produce iodinated alkyl-compounds when treated with iodine, as triiodide ion, at neutral pH. Similar treatment of phenol yields iodine-substituted phenols at appreciable concentrations.

Iodine is being considered for disinfection of recycled hygiene and potable water in Space Station Freedom. Like chlorine, the halogen iodine can form disinfection by-products (DBPs) when used as a disinfectant in waters with dissolved or colloidal organic compounds. Recycled shower and laundry wastewater, urine and condensate from the space cabin atmosphere all have large amounts of dissolved and colloidal organic compounds and may generate iodinated DBP's which can be toxic to humans. We have investigated the formation of iodinated DBP's (IDP's) in model compounds typical of shower wastewater and condensate. The selection of these model compounds and flask experiments to test for IDP formation have been described. Methods for reaction, extraction and analysis for IDP's also have been developed. We have tentatively identified likely organic precursors from recycled water and several iodinated organic compounds formed during the reaction with iodine.