Spacecraft Water Exposure Guidelines for Selected Contaminants Volume 2 (2007) / Chapter Skim
Currently Skimming:
Appendix 10 Total Organic Carbon
Appendix 10 Total Organic Carbon
Pages 453-464
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 453... ...
NASA-Johnson Space Center Habitability and Environmental Factors Office Houston, Texas GOALS OF A TOTAL ORGANIC CARBON STANDARD Because NASA probably will not have the real-time capability to quantify all individual organics that might break through the water recovery system (WRS) , a spacecraft water exposure guideline (SWEG)
|
From page 454... ...
For example, the WRS would not process humidity condensate immediately after a serious fire or after leakage of certain air pollutants such as ammonia from the U.S. Laboratory Module of the International Space Station (ISS)
|
From page 455... ...
The average concentration of TOC during the test was 0.30 mg/L, and the TOC component averages were as follows: 2-propanol, 0.14 mg/L; acetone, 0.12 mg/L; ethanol, 0.16 mg/L; and methanol, 0.21 mg/L, accounting for 100% of the TOC concentration. The concentrations of each of these components in the water were well below concentrations that would pose a health risk.
|
From page 456... ...
(mg/L) Taken Comments Phase I 15 0.24 0.43 2 Public water supply Phase II 30 0.10 0.24 7 Humidity condensate and reprocessed urine Phase IIa 60 0.14 0.53 51 Was most like ISS processor Phase III 91 0.06 0.29 45 Biologic recovery system added Abbreviations: ISS, International Space Station; No., number.
|
From page 457... ...
. It is essential to note that the potable water consisted of reprocessed water supplemented with water obtained from municipal ground sources and on-orbit sources that had magnesium and calcium formate salts added, as well as an iodine tincture containing ethanol.
|
From page 458... ...
Acetone could break through if combustion products enter the humidity condensate, and acetic acid also is a possible early contaminant in the recovered water. Because ethylene glycol is not used in the thermal loops of the ISS, the concerns over its possible leakage into the air, capture in the condensate, and breakthrough of the water purification system are negligible when compared with the situation aboard Mir.
|
From page 459... ...
ESTIMATION OF AN UPPER-LIMIT SWEG FOR TOC Basically, the task of the WRS is to reduce contaminants in influent water from a TOC concentration of a few hundred mg/L to one that is safe for human consumption. The weight of evidence is that any organic compound that initially breaks through the purification beds and increases the TOC concentration is unlikely to pose an immediate threat to crew health.
|
From page 460... ...
(EPA 2004) Methanol 0.21 0.27 0.49 0.31 -- -- Ethanol 0.16 -- 2.4 16.1 -- -- 2-Propanol 0.14 0.18 -- -- -- -- Ethylene glycol -- -- 45.5 -- [23]
|
From page 461... ...
i Source was water brought to Mir from the ground. Abbreviations: ISS, International Space Station; JSC, Johnson Space Center; MSFC, Marshall Space Flight Center; RfD, reference dose.
|
From page 462... ...
Thus, the product water's TOC concentration would be below 2.25, 3.90, and 5.4 mg/L, respectively. Although the nature of the compounds comprising the TOC will be markedly different in space WRSs, these target values suggest that our TOC safe concentration limit of 3 mg/L is reasonable.
|
From page 463... ...
The committee recommends that some form of statistical process control be implemented for monitoring TOC concentrations to ensure effective operation of the WRS. CONCLUSIONS The upper limit of the standard for a TOC concentration was set at 3 mg/L, assuming that the TOC comes entirely from formaldehyde, which is the most toxic component found at concentrations above 0.05 mg/L in the TOC of potable water.
|
From page 464... ...
SAE Technical Paper Series 961569. Pierre, L.M., J.R.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.