Browsing by Author "Wallace, William T."
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Item Chemical Characterization and Identification of Organosilicon Contaminants in ISS Potable Water(46th International Conference on Environmental Systems, 2016-07-10) Straub, John E. I I; Plumlee, Debrah K.; Gazda, Daniel B.; Wallace, William T.2015 marked the 15th anniversary of continuous human presence on board the International Space Station. During the past year crew members from Expeditions 42-46, including two participating in a one-year mission, continued to rely on reclaimed water as their primary source of potable water. This paper presents and discusses results from chemical analyses performed on ISS water samples returned in 2015. Since the U.S. water processor assembly (WPA) became operational in 2008, there have been 5 instances of organic contaminants breaking through the treatment process. On each occasion, the breakthrough was signaled by an increase in the total organic carbon (TOC) concentration in the product water measured by the onboard TOC analyzer (TOCA). Although the most recent TOC rise in 2015 was not unexpected, it was the first time where dimethylsilanediol (DMSD) was not the primary compound responsible for the increase. Results from ground analysis of a product water sample collected in June of 2015 and returned on Soyuz 41 showed that DMSD only accounted for 10% of the measured TOC. After considerable laboratory investigation, the compound responsible for the majority of the TOC was identified as monomethysilanetriol (MMST). MMST is a low-toxicity compound that is structurally similar to DMSD.Item Chemical Characterization of ISS Potable Water Collected in 2017(48th International Conference on Environmental Systems, 2018-07-08) Straub, John E. II; Plumlee, Debrah K.; Wallace, William T.; Alverson, James T.; Benoit, Mickie J.; Gillispie, Robert L.; Hunter, David; Kuo, Mike; Rutz, Jeffrey A.; Hudson, Edgar K.; Loh, Leslie J.; Gazda, Daniel B.This paper presents and discusses results from chemical analyses performed on archive potable water samples collected in the U.S. Segment of the International Space Station (ISS) during Expeditions 50-53. The sixth increase in the total organic carbon (TOC) concentration of the water produced by the U.S. water processor assembly (WPA) began during Expedition 50. Despite an initially precipitous climb, the TOC trend reversed several times and levels remained well below the potability limit. There have been five prior instances of organic contaminants breaking through the treatment process into the WPA product water since the system became operational in 2008. Contaminant breakthrough was signaled each time by an increase in TOC measured by the onboard TOC analyzer (TOCA). In all previous instances, the WPA multifiltration beds were replaced and the TOC concentration returned to nominal levels. The archival sample results discussed herein indicate that dimethylsilanediol (DMSD) was the primary compound responsible for the latest increase.Item ISS Potable Water Sampling and Chemical Analysis Results for 2016(47th International Conference on Environmental Systems, 2017-07-16) Straub, John E. I I; Plumlee, Debrah K.; Wallace, William T.; Alverson, James T.; Benoit, Mickie J.; Gillispie, Robert L.; Hunter, David; Kuo, Mike; Rutz, Jeffrey A.; Hudson, Edgar K.; Loh, Leslie J.; Gazda, Daniel B.This paper continues the annual tradition, at this conference, of summarizing the results of chemical analyses performed on archival potable water samples returned from the International Space Station (ISS). 2016 represented a banner year for life aboard the ISS, including the successful conclusion for 2 crewmembers of a record 1-year mission. Water reclaimed from urine and/or humidity condensate remained the primary source of potable water for the crewmembers of ISS Expeditions 46-50. The year was also marked by the end of a long-standing tradition of U.S. sampling and monitoring of Russian Segment potable water sources. Two water samples, taken during Expedition 46 and returned on Soyuz 44 in March 2016, represented the final Russian Segment samples to be collected and analyzed by the U.S. side. Although anticipated for 2016, a rise in the total organic carbon (TOC) concentration of the product water from the U.S. water processor assembly due to breakthrough of organic contaminants from the system did not materialize, as evidenced by the onboard TOC analyzer and archival sample results.Item Monitoring of the Atmosphere on the International Space Station with the Air Quality Monitor(47th International Conference on Environmental Systems, 2017-07-16) Wallace, William T.; Limero, Thomas F.; Loh, Leslie J.; Mudgett, Paul D.; Gazda, Daniel B.During the early years of human spaceflight, short duration missions allowed for monitoring of the spacecraft environment to be performed via archival sampling, in which samples were returned to Earth for analysis. With the construction of the International Space Station (ISS) and the accompanying extended mission durations, the need for enhanced, real-time monitors became apparent. The Volatile Organic Analyzer (VOA) operated on ISS for 7 years, where it assessed trace volatile organic compounds in the cabin air. The large and fixed-position VOA was eventually replaced with the smaller Air Quality Monitor (AQM). Since March 2013, the atmosphere of the U.S. Operating Segment (USOS) has been monitored in near real-time by a pair of AQMs. These devices consist of a gas chromatograph (GC) coupled with a differential mobility spectrometer (DMS) and currently target detection list of 22 compounds. These targets are of importance to both crew health and the Environmental Control and Life Support Systems (ECLSS) on ISS. Data is collected autonomously every 73 hours, though the units can be controlled remotely from mission control to collect data more frequently during contingency or troubleshooting operations. Due to a nominal three-year lifetime on-orbit, the initial units were replaced in February 2016. This paper will focus on the preparation and use of the AQMs over the past several years. A description of the technical aspects of the AQM will be followed by lessons learned from the deployment and operation of the first set of AQMs. These lessons were used to improve the already-excellent performance of the instruments prior to deployment of the replacement units. Data trending over the past several years of operation on ISS will also be discussed, including data obtained during a survey of the USOS modules. Finally, a description of AQM use for contingency and investigative studies will be presented.Item Search for a Real-Time Measurement of Dimethylsilanediol in the International Space Station Atmosphere using the Air Quality Monitor(45th International Conference on Environmental Systems, 2015-07-12) Wallace, William T.; Limero, Thomas F.; Gazda, Daniel B.; Macatangay, Ariel V.The discovery of dimethylsilanediol (DMSD) as a recurring contaminant in the U.S. segment of the International Space Station (ISS) water supply has exhibited the need to accurately determine the levels of this compound in-flight. Currently, the only real-time water quality monitoring systems on the ISS are the total organic carbon analyzer (TOCA) and the colorimetric water quality monitoring kit (CWQMK). These systems both provide important water quality data, but neither can provide compound-specific information for organic contaminants, requiring the use of archival analysis to determine if elevated total organic carbon (TOC) levels are due to a relatively benign compound like DMSD or to other, more toxic compounds. One potential method for indirect monitoring on board the ISS could be the use of the Air Quality Monitor (AQM) to determine if DMSD is present in the atmosphere. However, introducing DMSD samples into the AQM for a determination of analytical parameters has previously proven challenging. Recently, a prototype inlet based on electrothermal vaporization (ETV) was coupled with a ground-based AQM to evaluate its potential for in-flight water quality monitoring. This inlet has allowed us to remove volatile organics from a water matrix and analyze them using the AQM. Based on the parameters determined in this ground-based testing, we have discovered that it may be possible to monitor DMSD in the atmosphere of the ISS with the AQM. This paper will discuss the use of this novel sample inlet to analyze DMSD as well as the methods used to find DMSD in the ISS atmosphere. Additionally, a comparison of atmospheric DMSD data with in-flight TOC data will be presented to determine if changes in atmospheric concentration can be correlated with the periodic TOC increases.