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Silver biocide offers a potential advantage over iodine, the current state-of-the-art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. As such, silver may reduce the overall complexity and mass of future spacecraft potable water systems, particularly those used to support long duration missions. A primary technology gap identified for the use of silver biocide is one of material compatibility. Wetted materials of construction are required to be selected such that silver ion concentrations can be maintained at biocidally effective levels.

Extension of human habitation into space requires that humans carry with them many of the microorganisms with which they coexist on Earth. Whether microbes are present by design as constructed communities in bioregenerative life support systems or by accident as hitchhikers attached to human, plant, and spacecraft surfaces, the microbial ecosystems of Earth will be present in space. But how may the space environment affect the interaction of microbial communities? Given the potential for rapid change in populations of microorganisms through mutation, recombination, and natural selection (processes accelerated under space conditions of variable microgravity and elevated background radiation), it will be necessary to understand both the pattern and process of community assembly and evolution in the space environment.

Microbiological sampling and analysis was performed on the wet waste returned from the STS-105 and STS-108 shuttle missions servicing the International Space Station (ISS). Samples were collected from a variety of materials including plate waste and associated food packaging (which composed the majority of the collected waste), sanitary waste, and loose liquid inside the waste container. Analyses of the microbial loads cultured on both selective and non-selective media and through total bacterial counts by acridine orange direct count (AODC) methods showed high microbial densities in the waste container liquid. Isolates identified included Klebsiella pneumoniae, Serratia marcescens, Bacillus spp., Salmonella spp., and Escherichia coli (E.coli). Dry and ash weights were collected for each sample to determine water and organic content of the materials.

As part of NASA’s continued interest in the feasibility of Bioregenerative Life Support Systems (BLSS), research has focused on increasing the efficiency of bioregenerative technology. To reduce the costs associated with recovery of plant nutrients from inedible crop biomass, composting combined with leaching appears to be an attractive alternative to continuously stirred tank reactors. Tests at Kennedy Space Center investigating the effects of pre-processing of inedible wheat biomass composted for 21 days prior to leaching on nutrient recovery and growth of a subsequent wheat crop have been performed. In long-term hydroponic tests, pre-processed compost leachate was amended with reagent grade nutrients to approximate half-strength Hoagland’s solution. Although reductions in growth and yield were observed for plants grown on pre-processed compost leachate compared to the control, the differences were not statistically significant.