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Space Station Freedom (SSF) will be operational for up to 30 years with missions lasting up to 180 days. Because of the need for large amounts of potable and hygiene water for the crews, it will not be practical to supply water from the ground (as was done for Skylab) or to generate water from fuel cells (as is done for the Shuttle). Hence, waste and metabolic waters will be reclaimed and recycled in SSF. Because of the unique nature of the water sources and the closed loop recycling processes, providing safe water will be a challenging task. Developing a program for the verification of SSF water quality to ensure crew health is the responsibility of NASA's Medical Sciences Division at the Johnson Space Center (JSC). This program is being implemented through the Environmental Health System (EHS). This paper will describe the strategy for the development of water quality criteria and standards, and the associated monitoring requirements.

On the International Space Station (ISS), atmospheric humidity condensate and other waste waters will be recycled and treated to produce potable water for use by the crews. Space Station requirements include an on-orbit capability for real-time monitoring of key water quality parameters, such as total organic carbon (TOC), total inorganic carbon (TIC), total carbon (TC), pH, and conductivity, to ensure that crew health is protected during consumption of reclaimed water. The Crew Health Care System (CHeCS) for ISS includes an analyzer that has been designed to meet this requirement. The analyzer is adapted from commercially successful technology, and it measures TOC and TIC throughout the range from 1 to 50,000 μg/L, and TC from 1 to 100,000 μg/L. It measures pH between 2.0 and 12.0 pH units, and conductivity from 0.1 to 300 μmho/cm. The analyzer is scheduled for launch to ISS on mission 2A.1.

An approach to the isolation and concentration of volatile organic compounds from a water sample prior to chemical analysis in a microgravity environment has been previously described (Reference 1). The Volatile Organics Concentrator (VOC) system was designed for attachment to a gas chromatograph/mass spectrometer (GC/MS) for analysis of the volatile organics in water on Space Station Freedom. The VOC concept utilizes a primary solid sorbent for collection and concentration of the the organics from water, with subsequent transfer using nitrogen gas through a permeation dryer tube to a secondary solid sorbent tube. The secondary solid sorbent is thermally desorbed to a gas chromatograph for separation of the volatiles which are detected using a mass spectrometer.

An approach to the isolation and concentration of volatile organic compounds from a water sample prior to chemical analysis in a microgravity environment has been previously described (Reference 1). The Volatile Organics Concentrator (VOC) system was designed to attach to a gas chromatograph/mass spectrometer (GC/MS) for analysis of volatile organic compounds in water on Space Station Freedom. The VOC utilizes a primary solid sorbent for collection and concentration of the volatile compounds, transfer of the volatiles through a permeation dryer to a secondary solid sorbent, followed by thermal desorption of volatiles from the secondary sorbent onto a GC/MS system. Fabrications and preliminary testing of the VOC breadboard using a gas chromatography equipped with flame ionization detector has been previously described (Reference 2). These results have indicated that the VOC will meet or exceed the goals set for the program.

A shower test was conducted recently at NASA-JSC in which waste water was reclaimed and reused. Test subjects showered in a prototype whole body shower following a protocol similar to that anticipated for Space Station. The waste water was purified using reverse osmosis followed by filtration through activated carbon and ion exchange resin beds. The reclaimed waste water was maintained free of microorganisms by using both heat and iodine. This paper discusses the test results, including the limited effectiveness of using iodine as a disinfectant and the evaluation of a Space Station candidate soap for showering. In addition, results are presented on chemical and microbial impurity content of water samples obtained from various locations in the water recovery process.

The lessons of past and present manned space programs are clear. Successful design and operation of a spacecraft water system is contingent upon consideration of traditional sanitary engineering principles in the context of unique mission requirements. However, the aerospace solution to the traditional terrestrial problem often requires an innovative design approach to succeed in the spacecraft environment. Future long duration space missions will require the same attention to basic principles, the same degree of innovation, and an extra measure of caution, because of the lack of terrestrial experience with direct human reuse of reclaimed water.

One of the unique aspects of the Space Station is that it will be a totally encapsulated environment and the air and water supplies will be reclaimed for reuse. The Environmental Health System, a subsystem of CHeCS (Crew Health Care System), must monitor the air and water on board the Space Station Freedom to verify that the quality is adequate for crew safety. Specifically, the Water Quality Subsystem will analyze the potable and hygiene water supplies regularly for organic, inorganic, particulate, and microbial contamination. The equipment selected to perform these analyses will be commercially available instruments which will be converted for use on board the Space Station Freedom. Therefore, the commercial hardware will be analyzed to identify the gravity dependent functions and modified to eliminate them.

The crews of Expeditions 12 and 13 aboard the International Space Station (ISS) continued to rely on potable water from two different sources, regenerated humidity condensate and Russian ground-supplied water. The Space Shuttle launched twice during the 12-months spanning both expeditions and docked with the ISS for delivery of hardware and supplies. However, no Shuttle potable water was transferred to the station during either of these missions. The chemical quality of the ISS onboard potable water supplies was verified by performing ground analyses of archival water samples at the Johnson Space Center (JSC) Water and Food Analytical Laboratory (WAFAL). Since no Shuttle flights launched during Expedition 12 and there was restricted return volume on the Russian Soyuz vehicle, only one chemical archive potable water sample was collected with U.S. hardware and returned during Expedition 12. This sample was collected in March 2006 and returned on Soyuz 11.

On the International Space Station (ISS), atmospheric humidity condensate and other waste waters will be recycled and treated to produce potable water for use by the crews. Space station requirements include an on-orbit capability for real-time monitoring of key water quality parameters, such as total organic carbon, total inorganic carbon, total carbon, pH, and conductivity, to ensure that crew health is protected for consumption of reclaimed water. The Crew Health Care System for ISS includes a total organic carbon (TOC) analyzer that is currently being designed to meet this requirement. As part of the effort, a spacecraft TOC analyzer was developed to demonstrate the technology in microgravity and mitigate risks associated with its use on station. This analyzer was successfully tested on Shuttle during the STS-81 mission as a risk mitigation experiment. A total of six ground-prepared test samples and two Mir potable water samples were analyzed in flight during the 10-day mission.

Throughout the history of manned space flight the supply of potable water to the astronauts has presented unique problems. Of particular concern has been the microbiological quality of the potable water. This has required the development of both preflight water system servicing procedures to disinfect the systems and inflight disinfectant addition and monitoring devices to ensure continuing microbiological control. The disinfectants successfully used to date have been aqueous chlorine or iodine. Because of special system limitations the use of iodine has been the most successful for inflight use and promises to be the agent most likely to be used in the future. Future spacecraft potable, hygiene, and experiment water systems will utilize recycled water. This will present special problems for water quality control. NASA is currently conducting research and development to solve these problems.

The Microbial Check Valve (MCV) is a canister containing an iodinated ion exchange resin and is used on the Shuttle Orbiter to provide microbial control of potable water. The MCV provides a significant contact kill, and imparts a biocidal iodine residual to the water. The Orbiter MCV has a design life of 30 days. For longer duration applications, such as Space Station Freedom, an extended life is desirable to avoid resupply penalties. A method of in situ MCV regeneration with elemental iodine is being developed. During regeneration water en route to the MCV first passes through a crystalline iodine bed where a concentration between 200 - 300 mg/L I2 is attained. When introduced into the MCV, this high concentration causes an equilibrium shift towards iodine loading, effecting regeneration of the resin. After regeneration normal flow is re-established. Life cycle regeneration testing is currently in progress.

The Microbial Check Valve (MCV) is used on the Space Shuttle to impart an iodine residual to the drinking water to maintain microbial control. Approximately twenty MCV locations have been identified in the Space Station Freedom design, each with a 90 day life. This translates to 2400 replacement units in 30 years of operation. An in situ regeneration concept has been demonstrated that will reduce this replacement requirement to less than 300 units based on data to date and potentially fewer as further regenerations are accomplished. A totally automated system will result in significant savings in crew time, resupply requirements and replacement costs. An additional feature of the device is the ability to provide a concentrated biocide source (200 mg/liter of I2) that can be used to superiodinate systems routinely or after a microbial upset. This program was accomplished under NASA Contract Number NAS9-18113.

Iodine is the disinfectant used in U.S. spacecraft potable water systems. Recent long-term testing on human subjects has raised concerns about excessive iodine consumption. Efforts to reduce iodine consumption by Shuttle crews were initiated on STS-87, using hardware originally designed to deiodinate Shuttle water prior to transfer to the Mir Space Station. This hardware has several negative aspects when used for Shuttle galley operations, and efforts to develop a practical alternative were initiated under a compressed development schedule. The alternative Low Iodine Residual System (LIRS) was flown as a Detailed Test Objective on STS-95. On-orbit, the LIRS imparted an adverse taste to the water due to the presence of trialkylamines that had not been detected during development and certification testing. A post-flight investigation revealed that the trialkylamines were released during gamma sterilization of the LIRS resin materials.

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.

To satisfy a requirement to supply water to Mir station, a process for treating iodinated water on the Shuttle was developed and implemented. The treatment system consists of packed columns for removing iodine and a syringe-based injection system for adding ionic silver, the biocide used in Mir water. Technical and potable grade water is produced and transferred in batches using collapsible 44-liter contingency water containers (CWCs). Silver is added to the water via injection of a solution from preloaded syringes. Minerals are also added to water destined for drinking. During the previous four Shuttle-Mir docking missions a total of 2781 liters (735 gallons) of water produced by the Shuttle fuel cells was processed using this method and transferred to Mir. To verify the quality of the processed water, samples were collected during flight and returned for chemical analysis.

We are developing a drinking water test kit based on colorimetric-solid phase extraction (C-SPE) for use onboard the International Space Station (ISS) and on future Lunar and/or Mars missions. C-SPE involves measuring the change in diffuse reflectance of indicator disks following their exposure to a water sample. We previously demonstrated the effectiveness of C-SPE in measuring iodine in microgravity. This analytical method has now been extended to encompass the measurement of total I (i.e., iodine, iodide, and triiodide). This objective was accomplished by introducing an oxidizing agent to convert iodide and triiodide to iodine, which is then measured using the indicator disks previously developed for iodine. We report here the results of a recent series of C-9 microgravity tests of this method. The results demonstrate that C-SPE technology is poised to meet the total I monitoring requirements of the international space program.

One of the proposed methods for monitoring the microbial quality of the water supply aboard the International Space Station is membrane filtration. We adapted this method for space flight by using an off-the-shelf filter unit developed by Millipore. This sealed unit allows liquid to be filtered through a 0.45 μm cellulose acetate filter that sits atop an absorbent pad to which growth medium is added. We combined a tetrazolium dye with R2A medium to allow microbial colonies to be seen easily, and modified the medium to remain stable over 70 weeks at 25°C. This hardware was assembled and tested in the laboratory and during parabolic flight; a modified version was then flown on STS-66. After the STS-66 mission, a back-up plastic syringe and an all-metal syringe pump were added to the kit, and the hardware was used successfully to evaluate water quality aboard the Russian Mir space station.

Phase separation is one of the most significant obstacles encountered during the development of analytical methods for water quality monitoring in spacecraft environments. Removing air bubbles from water samples prior to analysis is a routine task on earth; however, in the absence of gravity, this routine task becomes extremely difficult. This paper details the development and initial ground testing of liquid metering centrifuge sticks (LMCS), devices designed to collect and meter a known volume of bubble-free water in microgravity. The LMCS uses centrifugal force to eliminate entrapped air and reproducibly meter liquid sample volumes for analysis with Colorimetric Solid Phase Extraction (C-SPE). Previous flight experiments conducted in microgravity conditions aboard the NASA KC-135 aircraft demonstrated that the inability to collect and meter a known volume of water using a syringe was a limiting factor in the accuracy of C-SPE measurements.

Collapsible bladder tanks called Contingency Water Containers (CWCs) have been used to transfer water from the Shuttle to the Mir and the International Space Station (ISS). Because their use as potable water storage on the ISS is planned for years, efforts are underway to improve the containers, including the evaluation of new materials. Combitherm®, a multi-layer plastic film, is a material under evaluation for use as the CWC bag material. It consists of layers of linear low density polyethylene, ethylene-vinyl alcohol copolymer, nylon, and a solvent- free adhesive layer. Long term studies of the quality of water stored in Combitherm bladders indicate a gradual but steady increase in the total organic carbon value. This suggests a leaching or breakdown of an organic component of the Combitherm.

The Crew Health Care System (CHeCS) is responsible for providing environmental monitoring to protect crew health, including in-flight chemical water quality analysis. To meet this objective, Total Organic Carbon Analyzer (TOCA) Serial Number (SN) 1002 was launched to the International Space Station (ISS) in April of 2001 as part of the CHeCS hardware. Since that time it has been used to evaluate the quality of the potable water supplies consisting of reprocessed atmospheric condensate water, Shuttle-transferred water, and ground-supplied water. Potable water is available for crew use from the Service Module System for Regeneration of Water from Condensate (SRV-K) galley hot and warm ports and the Stored Potable Water System (SVO-ZV) port. Potable water samples are periodically collected from each of these ports for in-flight analysis with the TOCA.