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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.

A Total Organic Carbon (TOC) Analyzer has been developed for a Life Sciences Risk Mitigation Flight Experiment to be conducted on Spacehab and the Russian space station, Mir. Initial launch is scheduled for December 1996 (flight STS-81). The analyzer will be tested on the Orbiter in the Spacehab module, including when the Orbiter is docked at the Mir space station. The analyzer is scheduled to be launched again in May 1997 (STS-84) when it will be transferred to Mir. During both flights the analyzer will measure the quality of recycled and ground-supplied potable water on the space station. Samples will be archived for later return to the ground, where they will be analyzed for comparison to in-flight results. Water test samples of known composition, brought up with the analyzer, also will be used to test its performance in microgravity. Ground-based analyses of duplicates of those test samples will be conducted concurrently with the in-flight analyses.

On the International Space Station (ISS), humidity condensate will be collected from the atmosphere and treated by multifiltration to produce potable water for use by the crews. Ground-based development tests have demonstrated that multifiltration beds filled with a series of ion-exchange resins and activated carbons can remove many inorganic and organic contaminants effectively from wastewaters. As a precursor to the use of this technology on the ISS, a demonstration of multifiltration treatment under microgravity conditions was undertaken. On the Space Shuttle, humidity condensate from cabin air is recovered in the atmosphere revitalization system, then stored and periodically vented to space vacuum. A Shuttle Condensate Adsorption Device (SCAD) containing sorbent materials similar to those planned for use on the ISS was developed and flown on STS-68 as a continuation of DSO 317, which was flown initially on STS-45 and STS-47.

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.

Controlling microbial growth and biofilm formation in spacecraft water-distribution systems is necessary to protect the health of the crew. Methods to decontaminate the water system in flight may be needed to support long-term missions. We evaluated the ability of iodine and ozone to kill attached bacteria and remove biofilms formed on stainless steel coupons. The biofilms were developed by placing the coupons in a manifold attached to the effluent line of a simulated spacecraft water-distribution system. After biofilms were established, the coupons were removed and placed in a treatment manifold in a separate water treatment system where they were exposed to the chemical treatments for various periods. Disinfection efficiency over time was measured by counting the bacteria that could be recovered from the coupons using a sonication and plate count technique. Scanning electron microscopy was also used to determine whether the treatments actually removed the biofilm.

The objective of this study was to investigate combining GC/MS and CE methods to allow sub-mg/L levels of organic acids to be determined in various water samples. This study also served as a basis for evaluating these instruments for in-flight spacecraft water-quality monitoring and to help determine the modifications needed to convert terrestrial hardware for use in microgravity environments. This paper reports on current GC/MS and CE method development and data generated from some recent spacecraft-related water samples. Plans for further method development are also discussed.

Iodine depletion in a simulated water storage tank and distribution system was examined to support a larger research program aimed at developing disinfection methods for spacecraft potable water systems. The main objective of this study was to determine the rate of iodine depletion with respect to the surface area of the stainless steel components contacting iodinated water. Two model configurations were tested. The first, representing a storage and distribution system, consisted of a stainless steel bellows tank, a coil of stainless steel tubing and valves to isolate the components. The second represented segments of a water distribution system and consisted of eight individual lengths of 21-6-9 stainless tubing similar to that used in the Shuttle Orbiter. The tubing has a relatively high and constant surface area to volume ratio (S/V) and the bellows tank a lower and variable S/V.

The Microbial Check Valve (MCV) is a reloadable flow-through canister containing iodinated ion exchange resin, which is used aboard the Shuttle Orbiter as a disinfectant to maintain water potability. The MCV exhibits a significant contact kill and imparts a biocidal residual I2 concentration to the effluent. MCVs in current use have nominal 30 day lives. MCVs baselined for Space Station Freedom will have 90 day lives, and will require replacement 120 times over 30 years. Means to extend MCV life are desirable to minimize resupply penalties. New technology has been developed for fully autonomous in situ regeneration of an expended MCV canister. The Regenerative Microbial Check Valve (RMCV) consists of an MCV, a packed bed of crystalline I2, a flow diverter valve, an in-line iodine monitor and a microcontroller. During regeneration, flow is directed first through the packed I2 bed and then into the MCV where the resin is replenished.

When construction of Space Station Freedom reaches the Permanent Manned Capability stage, plans call for the Water Recovery and Management Subsystem to treat distilled urine, spent hygiene water, and humidity condensate in order to reclaim water of potable quality. The reclamation technologies currently baselined to process these wastewaters include adsorption, ion exchange, catalytic oxidation, and disinfection. To ensure that baselined technologies will be able to effectively remove those compounds that present health risks to the crew, the National Research Council has recommended that additional information be gathered on specific contaminants in wastewaters representative of those to be encountered on Space Station. This paper reports the efforts by the Water and Food Analytical Laboratory at the Johnson Space Center to enlarge the database of potential contaminants in humidity condensate.

Reference cultures of 16 microorganisms obtained from the American Type Culture Collection and four clinical isolates were used in standardized solutions to inoculate 60 cards for each test strain. A set of three ID and three susceptibility cards was processed in the Vitek AutoMicrobic System (AMS) immediately after inoculation. The remaining cards were refrigerated at 4°C, and sets of six cards were removed and processed periodically for up to 17 days. The preinoculated AMS cards were evaluated for microorganism identification, percent probability of correct identification, length of time required for final result, individual substrate reactions, and antibiotic minimal inhibitory concentration (MIC) values. Results indicate that 11 of the 20 microbes tested withstood refrigerated storage up to 17 days without detectable changes in delineating characteristics. MIC results appear variable, but certain antibiotics proved to be more stable than others.

Until 1989, ion chromatography (IC) was the baseline technology selected for the Specific Ion Analyzer, an in-flight inorganic water quality monitor being designed for Space Station Freedom. Recent developments in capillary electrophoresis (CE) may offer significant savings of consumables, power consumption, and weight/volume allocation, relative to IC technology. A thorough evaluation of CE's analytical capability, however, is necessary before one of the two techniques is chosen. Unfortunately, analytical methods currently available for inorganic CE are unproven for NASA's target list of anions and cations. Thus, CE electrolyte chemistry and methods to measure the target contaminants must be first identified and optimized. This paper reports the status of a study to evaluate CE's capability with regard to inorganic and carboxylate anions, alkali and alkaline earth cations, and transition metal cations.

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 STS water system is treated with iodinated water in order to prevent microbial contamination. This water is prepared by adding a concentrated solution of iodine to Ground Service Equipment (GSE) before adding the water in that unit to the spacecraft system. The solution is prepared by dissolving iodine in ethanol to make a tincture stock solution. While this procedure is rapid, the ethanol increases the carbon levels in the STS potable water and may produce unpleasant odors. The resulting high carbon levels preclude the use of total organic carbon measurements as a water quality monitoring tool. The use of triiodide solutions was studied as a substitute for using ethanol solutions. Two dissolution agents, sodium iodide and hydriodic acid, were investigated. Sodium iodide was studied at molar concentration ratios ranging from 1:1 to 2.5:1 sodium iodide to molecular iodine.

Two simulated spacecraft water systems are being used to evaluate the effectiveness of iodine for controlling microbial contamination within such systems. An iodine concentration of about 2.0 mg/L is maintained in one system by passing ultrapure water through an iodinated ion exchange resin. Stainless steel coupons with electropolished and mechanically-polished sides are being used to monitor biofilm formation. Results after three years of operation show a single episode of significant bacterial growth in the iodinated system when the iodine level dropped to 1.9 mg/L. This growth was apparently controlled by replacing the iodinated ion exchange resin, thereby increasing the iodine level. The second batch of resin has remained effective in controlling microbial growth down to an iodine level of 1.0 mg/L. Scanning electron microscopy indicates that the iodine has impeded but may have not completely eliminated the formation of biofilm.

With the restructure and funding changes for Space Station Freedom, the Environmental Health System (EHS)/Microbiology Subsystem revised its scheduling and operational requirements for component hardware. The function of the Microbiology Subsystem is to monitor the environmental quality of air, water, and internal surfaces and, in part, crew health on board Space Station. Its critical role shall be the identification of microbial contaminants in the environment that may cause system degradation, produce unsanitary or pathogenic conditions, or reduce crew and mission effectiveness. EHS/Microbiology operations and equipment shall be introduced in concert with a phased assembly sequence, from Man Tended Capability (MTC) through Permanently Manned Capability (PMC). Effective Microbiology operations and subsystem components will assure a safe, habitable, and useful spacecraft environment for life sciences research and long-term manned exploration.

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.