Generation of Iodine Disinfection By-Products (IDP's) in a Water Recycle System

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. As we increase the complexity of the water matrix, eventually studying recycled shower wastewater, the flask experiment data will allow understanding of the reactions of iodine disinfectant with the organic compounds found in space water recycle systems.