One of the long-standing concerns in space exploration is the presence of trace organic contaminants in recycled spacecraft water supplies. At present, water samples on the International Space Station (ISS) are collected at regular intervals, stored in Teflon™-lined containers, and returned to Earth for characterization. This approach, while effective in defining water quality, has several notable problems. First, this method of archiving removes a significant volume of the ISS water supply. Second, the archived water consumes valuable cargo space in returning Shuttle and Soyuz vehicles. Third, the organic contaminants present in the collected samples may degrade upon extended storage. The latter problem clearly compromises sample integrity. Upon return to Earth, sample degradation is minimized by refrigeration. Due to present resource constraints, however, refrigeration is not a viable option in space.
This paper describes the first findings from an investigation of solid phase extraction (SPE) as an effective approach to sample archiving. With SPE, the organic contaminants in the spacecraft water can be trapped and concentrated on a thin membrane or other extraction medium, with the resulting effluent recycled back into the water supply as opposed to being stored and returned to Earth. This approach, therefore, has the potential to: (1) dramatically reduce the amount of water removed for sampling, (2) minimize the stowage needed to return the samples to Earth, and (3) mitigate sample degradation. Results from an evaluation of this concept using synthetic spacecraft water and a range of extraction materials are described, along with the findings from a KC-135 flight evaluation of the effectiveness of and experimental challenges in implementing this concept in microgravity. Plans for the next generation of experiments, based on these results, are also briefly discussed.