Quality of Water Supplied by Shuttle to ISS

The water supply for the International Space Station (ISS) consists partially of excess fuel-cell water that is treated on the Shuttle and stored on ISS in 44 L collapsible Contingency Water Containers (CWCs). Iodine is removed from the source water, and silver biocide and mineral concentrates are added by the crewmember while the CWCs are filled. Potable (mineralized) CWCs are earmarked for drinking and food hydration, and technical (non-mineralized) CWCs are reserved for waste system flushing and electrolytic oxygen generation. Representative samples are collected in Teflon^® bags and returned to Earth for chemical analysis. The parameters typically measured include pH, conductivity, total organic carbon, iodine, silver, calcium, magnesium, fluoride, trace metals, formate and alcohols. The Nylon monomer caprolactam is also measured and tracked since it is known to leach slowly out of the plastic CWC bladder material. This paper provides an overview of Shuttle supplied water quality from the first transfer on STS-96 (2A.1) through STS-110 (8A). Water sample data are presented and discussed. Results demonstrate that CWC water is of consistent high quality, the hardware and methods for water treatment and sampling are reliable, and the shelf life of CWC water exceeds 1 year.