The concept for the “Biological Air Filter” (BAF) is based onto the property of certain selected microorganisms for the complete oxidation to water, carbon dioxide and salts, of gaseous contaminants.
The EXEMSI manned space mission simulation campaign offered a good opportunity for testing the performances of an experimental BAF on a real confined atmosphere.
Major obtained results are:
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confirmation of the validity of the fundamental concepts selected for the BAF, i.e.
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the use of an engineered microbial population and,
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the immobilisation of this population in a membrane reactor,
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confirmation of the applicability of microbial conversion to a very wide range of contaminants concentrations from SMAC values (usually ppm range; working range for previous laboratory testing) to extremely low concentrations (ppb range) observed during the campaign,
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identification of complementary bioconversion capability as compared to what was known before the campaign for the microbial population used; this applies for a number of still unidentified compounds (C3.7, C4.8, C6.2, C10.3 and C13.2), for ethyne, ethene, propene and propane, and for isopropanol and methane for which the population was not adapted in the preparatory laboratory phase.
Among the degraded contaminants, elimination yield for the identified contaminants ranges around 10 to 40% for methane, 50 to 90% for acetone, 80 to 99% for isopropanol and above 99.9% for toluene. Computer modelling show that such a methane conversion efficiency (obtained for a single passage through a BAF) is sufficient to maintain the methane concentration in a space cabin below the SMAC value.
As a side result, the trace contamination regime in EXEMSI was experienced being characterised by very sharp and large changes in concentrations; a further conclusion regarding confinement experiments is hence the need for continuous or integrating monitoring of trace contaminants.