WATER: PRODUCTION, RECLAMATION, DISINFECTION


Aboard current spacecraft such as the Mir, water is used for drinking, food preparation, personal hygiene, oxygen generation, and scientific experiments. In the future, water will be supplied to plant growth chambers for the production of both oxygen and food. Water may also be used in the destruction of solid wastes by techniques based upon supercritical water oxidation (SCWO) or steam reforming reactions in Advanced Life Support Systems (ALSS).

 In a closed loop life support system wastewater must be purified so that it can be used again. The costs of resupply from the ground are prohibitive. Water which has been transported to the cabin atmosphere through evaporation and through breathing is recovered as humidity condensates using condensing heat exchangers. Water which has been used for personal hygiene (containing a variety of substances including salts, soaps, hair and other particulate matter) is collected for purification. Urine is also collected for treatment. Currently, these three sources form the primary inputs to life support water reclamation systems. Disinfectants must be added to the reclaimed waters to prevent the growth of pathogenic microorganisms. Water contained in feces and other solid waste is lost from the system and must be made up by onboard water production facilities or by resupply.

 Three separate water purification loops are used onboard the Russian Mir space station. Urine is purified as a feed to the electrolysis cells which generate oxygen. Hygiene water is reprocessed for re-use only as hygiene water. All potable (drinking and food preparation) water aboard Mir comes from the purification of humidity condensate or from resupply. This is similar to the original water reclamation scheme for the Space Station Freedom program. Subsequent reconfigurations of Freedom resulted in a single water processor to treat a composite stream containing the three sources (humidity condensate, hygiene water, and urine distillate). This has carried over to the water processor design for the International Space Station Alpha (ISSA), due to begin construction in late 1997.


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Author: Tugrul Sezen
sezen@nas.nasa.gov

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