Spacecraft cabin air quality control and its application to tight buildings

Perry, Jay L.; Graf, John

doi:10.2514/6.1995-1050

Cited by 2 publications

(10 citation statements)

References 2 publications

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“…Regardless, the studies reported herein utilized perlite, rather than leaf compost, in order to observe nitrification in detail without the complicating effects of organic matter. Such complications include an added buffering capacity, assimilation of NH 3 as a nitrogen source by heterotrophic populations, loss of NO 3 -through denitrification in anoxic zones, and ammonification of organic nitrogen. This use of an inert matrix (perlite) helped clarify the changes that occurred with respect to NH 4 + , NO 2 -, NO 3 -, and pH in the material exclusively as a result of NH 3 addition and nitrification.…”

Section: Resultsmentioning

confidence: 99%

“…The gas exiting the biofilter passed through a knockout trap and subsequently through three sequential gas washing bottles (Figure 1a, 7), each containing 200 mL of 1 N H 2 SO 4 in order to trap any NH 3 . This NH 3 trapping system was highly efficient in removing all the NH 3 delivered to it, with most removal occurring in the first bottle.…”

Section: Methodsmentioning

confidence: 99%

“…3 The SMAC values for NH 3 for exposure periods of 1 and 24 hr are 30 and 20 ppm, respectively. For an exposure period of 1 week to 6 months, the SMAC value is 10 ppm.…”

Section: Introductionmentioning

confidence: 99%

“…For an exposure period of 1 week to 6 months, the SMAC value is 10 ppm. 3,4 The recommended industrial workplace time-weighted average threshold limit value based on an 8-hr work day is 25 ppm, whereas the shortterm exposure limit value (15 min) is 35 ppm. 5 In contrast, the threshold odor concentration ranges between 0.66 and 49 ppb, 6 indicating that odor concerns, rather than health issues, may realistically determine treatment requirements.…”

Section: Introductionmentioning

confidence: 99%

“…[15][16][17] Although removal of NH 3 in biofilters has been demonstrated, the removal mechanism is uncertain. 18,19 Togashi et al 20 reported biological removal of NH 3 at a 20-ppm-inlet concentration in laboratory-scale peat biofilters seeded with nitrifiers.…”

Section: Introductionmentioning

confidence: 99%

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Biological Removal of Gaseous Ammonia in Biofilters: Space Travel and Earth-Based Applications

Joshi

Hogan

Cowan

et al. 2000

Journal of the Air & Waste Management Association

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Gaseous NH 3 removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH 3 concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH 3 for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH 3 removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH 3 could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO 3 -early in the operation, but later both NO 2 -and NO 3 -accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20-and 50-ppm biofilters, respectively. A partial IMPLICATIONS Biofilters are becoming an acceptable and economical air pollutant control technology for treating air contaminated with low concentrations of certain gaseous volatile organic compounds (VOCs) and inorganic sulfur compounds. Although NH 3 removal in biofilters has also been demonstrated, the mechanism of removal has been unclear. This research demonstrates the mechanisms of NH 3 removal in biofilters and also some of the associated problems. Potential applications include improved treatment of waste gas streams containing NH 3 , such as those from wastewater treatment systems, animal houses, and composting facilities. Another specialized application considered here is the treatment of cabin air and exhaust gas streams from waste treatment, food processing, and plant growth operations for long-duration space missions, where it is important not only to treat the waste gases but also, if possible, to recover nutrients for recycling into biomass production.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…3 The SMAC values for NH 3 for exposure periods of 1 and 24 hr are 30 and 20 ppm, respectively. For an exposure period of 1 week to 6 months, the SMAC value is 10 ppm.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%