AWWA WQTC62537

Long-term space missions pose a number of challenges, including provision of safe potable water for the crew. Bringing water from earth sources for long-term space missions beyond near-Earth orbit is not practical for several reasons, including costs on the order of $40,000/gallon. Therefore, the National Aeronautics and Space Administration (NASA) has focused on developing closed-loop water treatment processes, which do not require water resupply. The use and reuse of water in a closed-loop system poses a number of challenges for water disinfection, including poor "source" water quality, diverse microorganism populations, and evolution of microogransisms, which may result in the emergence of more resistant strains. To overcome the hurdles of a close-loop treatment system, a complementary disinfection process has been developed to target a wide range of microorganisms. The disinfection process uses ultraviolet (UV) radiation as the primary disinfectant and a chemical disinfectant (iodine) as the residual disinfectant. UV radiation was selected as the primary disinfectant because it is effective at inactivating a broad spectrum of microorganisms and has minimal potential for the formation of disinfection byproducts. Iodine, which is effective at inactivating many microorganisms, was selected as the residual disinfectant because it has the potential for dual use as an on-line UV monitor and a disinfectant. Also, iodine has been used as a water disinfectant in NASA space missions since the 1970s. NASA chose iodine as the disinfectant of choice because it has a low vapor pressure and a relatively long-lasting residual (Columbo 1987). Includes 7 references, figures.