Sequential water disinfection using UV irradiation and iodination for long-term space missions
As part of the NASA Specialized Center of Research and Training for Advanced Life Support (NSCORT-ALS), a disinfection process, which uses ultraviolet (UV) radiation as the primary disinfectant and iodine as the secondary disinfectant, was investigated.
The purpose of this research was to support NASA's goal of long-term space missions to destinations such as Mars. Long-term space missions typically refer to missions with durations of one (1) to five (5) years. For a hypothetical mission to Mars, the length of the mission is estimated to be 600 days. All of the items required for survival of the six person crew would need to be readily available during the mission, including safe potable water.
Due to cost and logistical considerations associated with supplying the crew with earth-based potable water for the entire mission duration, closed-loop water treatment processes, in which a finite amount of water is continuously used and re-used, are being considered. Closed-loop treatment systems are comprised of many individual processes. The subject research is focused on the water disinfection process using ultraviolet (UV) radiation as the primary disinfectant and a chemical disinfectant (iodine) as the residual disinfectant.
The four main research objectives completed as part of this research are summarized below. (1) Developed a tool that allowed iodine species and concentrations to be predicted based on system characteristics, such as pH and redox potential. (2) Investigated the disinfection efficacy of UV radiation and iodine using a challenge microorganism (Bacillus subtilis spores). Effort was placed on characterizing the response of B. subtilis spores to sequential disinfection (i.e. UV then iodine). Inactivation models were developed to describe the inactivation kinetics. (3) Evaluated a chemical actinometer to monitor the minimum dose within a UV reactor. A continuous-form irradiance field model was developed to estimate the output of a cylindrical non-mercury containing UV source. (4) Developed a means to utilize the photoproduct of the actinometer as a residual disinfectant. Emphasis was placed on providing a beneficial chemical residual and minimizing chemical requirements.
0775: Environmental engineering
0538: Aerospace materials