Search Results

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.

The purpose of this research is to determine the feasibility of a unique denitrifying composter to stabilize trash from space-habitation (STS, ISS, ALS) life support activities. Design criteria were derived from variables to be manipulated and those to be held constant. A pre-existing aerobic composter was used and engineering tests run to ensure that requirements were met. Key experimental variables were identified: NO3- concentration and rate of addition, O2 concentration, mixing duration and frequency, and inoculum. Independent variables were pH, temperature, moisture, C:N ratio, feed material, size reduction, feed addition rate, and mode of operation. Important performance parameters included: maximization of desired outcomes – BOD5 removal, CO2 production, waste stabilization, and denitrification – and minimization of undesired products – N2O, NH3, and volatile organic compounds.

Microorganisms will be an integral part of biologically based waste processing systems used for water purification or nutrient recycling on space flights. Establishment of these systems with a defined group of microorganisms will provide a standardized means for conferring specific properties to the system. The purpose of this study was to develop microbial inocula (a defined, constructed community and an undefined community) for initiation of plant-based graywater waste processing systems. To this end, small-subunit 16S rDNA sequence analysis was used to describe the population composition of microbial communities from a plant-based graywater waste treatment system and from an industrial wastewater treatment plant (WWTP). The clonal library of organisms from the graywater-degrading rhizosphere community suggested that members of the Cytophagales and Proteobacteria phylogenetic groups dominated. The clonal library of organisms from industrial WWTP was taxonomically more diverse.

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.

Ground studies are continuing at Kennedy Space Center to define the performance of the Immobilized Microbe Microgravity Water Processing System (IMMWPS), a denitrifying, fixed-bed reactor designed for shuttle flight-testing. The goal of these experiments was to define organic compounds that could be used as indicators of changes in reactor performance as to the removal of surfactant and to evaluate additional flight and sampling protocols. While changes in the breakthrough concentration of surfactant would provide insight into performance changes during the flight experiment, this breakthrough of surfactant in the flight system is undesirable due to operational problems resulting from foaming of the undegraded surfactant. By monitoring a degradation intermediate instead of the surfactant in the effluent, this problem could be avoided while monitoring any effects of microgravity on bioreactor performance during space flight.

A multitude of personal cleaning products, each of which typically contains multiple surfactants, are available for terrestrial use. Selection of surfactant(s) for use in extended space missions should consider, in addition to human comfort and cleansing power, potential impacts on biological processing systems under consideration for such missions. This paper reviews the surfactants present in commercial formulations, their proper nomenclature, and relevant properties such as foaming, biodegradability of organic fractions (both with respect to rate and pathway), presence of inorganic components (e.g., sulphate or counter ions such as sodium), and analytical methods for monitoring their concentrations in waste stream. The background information and results from preliminary testing are used to draw conclusions about the proper approach for selecting surfactants for use in space missions containing biological waste treatment systems.

Ground studies at Kennedy Space Center were done to define and optimize performance of the Immobilized Microbe Microgravity Water Processing System (IMMWPS), a denitrifying, fixed-bed reactor designed for Shuttle flight-testing. The purpose of the current studies was to evaluate additional flight protocol issues, including microbial backgrowth in the influent tubing and concomitant reduction of influent Igepon levels prior to bioreactor treatment, and the effects of bioreactor shutdown for loading and launch. Experiments were done to evaluate sterilization procedures and the effect of delivery tubing diameter on microbial backgrowth. Analytical methods employed included ion-pairing reversed phase chromatography coupled with suppressed conductivity detection for monitoring Igepon concentrations in the influent and effluent, and acridine orange direct count (AODC) technique for quantifying microbial growth in influent lines.

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.

The use of composting technology is attractive to NASA’s Bioregenerative Life Support System (BLSS) research because it offers a potential reduction in system costs when compared to other waste recycling approaches. Water-soluble leachates from 28-day composted fresh or oven-dried inedible wheat biomass were amended with reagent-grade nutrients to be inorganically equivalent to ½-strength Hoagland’s (control) replenishment solution. A portion of the fresh and oven-dried compost leachate was filtered to remove large organic particles and a majority of the microflora, and wheat plants were grown hydroponically on these amended leachates. For both the fresh and oven-dried compost leachate treatments, filtering the leachate had no effect on plant response. No significant difference was observed between the fresh compost leachate treatments and the control.

Ground studies at Kennedy Space Center were conducted to determine microbial requirements of the Immobilized Microbe Microgravity Water Processing System (IMMWPS), a denitrifying, fixed-bed reactor designed for Shuttle flight-testing. The reactor was operated with a simulated graywater “waste stream” containing the surfactant Igepon TC-42TM as the sole carbon source. Experiments were conducted to determine the effect of hydraulic retention time (HRT) and feed nutrient composition on surfactant degradation. The source of inoculum as well as procedure for inoculating the reactor was also examined. A complete nutrient mix in the feed formulation was required for sustained Igepon degradation throughout the reactor runs at the short (1.4 days) and intermediate (1.9 days) hydraulic retention time (HRT), regardless of inoculum source.

The inclusion of bioregenerative life support elements (i.e., plant growth systems and bioreactors) will significantly increase the total abundance of microorganisms in extraterrestrial facilities. If the microbial communities associated with these systems (e.g., biofilms attached to plant roots or hardware surfaces) serve as reservoirs for potentially pathogenic human-associated bacteria, then bioregenerative systems may represent a human health risk. Research at the Kennedy Space Center during the past several years has attempted to quantify this risk by assessing the capacity of different human-associated bacteria to survive in prototype ALS systems.

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.

Bioreactor technology for bioprocessing graywater solutions in microgravity is under development by NASA at Johnson Space Center and at major aerospace companies. Inoculum sources have been inconsistent. Startup and subsequent operation of ground-based bioreactors may have been adversely affected by this inconsistency and/or by inoculation procedures. The goal of the research reported in this paper is to develop an inoculum that will completely biodegrade Igepon T42 soap to carbon dioxide and water under anaerobic, denitrifying conditions and with process conditions set by bioreactor design requirements for microgravity operation. Potential inoculum sources from two habitats within the KSC-ALS breadboard project were developed for potential use. The effects of pH (7.2 vs. 9.0, buffered) on soap degradation by the two inocula was determined in a flask study. Nearly all of the soap was degraded at pH 7.2 while nearly none was degraded at pH 9.0. Both inocula behaved similarly.

The National Aeronautics and Space Administration (NASA) intends to continue the human exploration of outer space. Long duration missions will require the development of reliable regenerative life support processes. The intent of this paper is to define the Kennedy Space Center Controlled Ecological Life Support System (CELSS) research plan for the development and testing of three candidate biological processors for a hybrid biological and physical-chemical waste recycling system. The system would be capable of reclaiming from inedible plant biomass, human metabolic waste, and gray water those components needed for plant growth (carbon dioxide, water, and inorganic salts), while eliminating noxious compounds and maximizing system closure. We will colaborate with AMES Research Center (ARC), Johnson Space Center (JSC), and academia, to design a functional biological-based waste processing system that could be integrated with the planned Human Rated Test Facility (HRTF) at JSC.

The coupling of plant growth and waste recycling systems is an important step toward the development of bioregenerative life support systems. This research examined the effectiveness of two alternative methods for recycling nutrients from the inedible fraction (residue) of candidate crops in a bioregenerative system; 1) extraction in water, or leaching, and 2) combustion at 550 °C, with subsequent reconstitution of the ash in acid. The effectiveness of the different methods was evaluated by 1) comparing the percent recovery of nutrients, and 2) measuring short- and long-term plant growth in hydroponic solutions, based on recycled nutrients.