Space Station Water Recovery Trade Study—Phase Change Technology

Space Station water recovery involves five separate reprocessing loops: potable water from cabin humidity condensate and carbon dioxide reduction water, hygiene water from crew hygiene activities, hygiene water from crew urine, animal cage wash water and experiment waste water. The magnitudes of the separation tasks involved differ substantially, as do the waste and product water qualities. Three different phase change water recovery technologies are being considered for Space Station use. They include Air Evaporation, Thermoelectric Integrated Membrane Evaporation and Vapor Compression Distillation (VCD). The potential application of these technologies to each reprocessing loop is considered. Comparisons are drawn for urine processing based on a range of evaluation criteria, including product water quality, specific energy, percent recovery, power, weight, resupply needs, reliability, technological maturity, zero-gravity compatibility and contamination potential. Vapor Compression Distillation was found to be the most cost-effective method for reclaiming water from urine. Recommendations are made to consider applying VCD to hygiene water, cage washer water and experiment water processing also.