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Bioregenerative resource recovery components for Advanced Life Support systems will need to be reliable and stable for long duration space travel. Since 1989, bioregenerative life support research at the ALS Breadboard Project has examined processing of inedible crop residues in bioreactors for recovery of nutrients for replenishment of crop hydroponic solutions. Bioreactor operation has been reliable as demonstrated by continuous operation for up to 418 days with long periods of steady state conditions. Bioreactors have demonstrated stability following unplanned, non-lethal perturbations in pH, temperature, dissolved oxygen, and inedible residue supply. In each instance, a rapid return to steady state conditions was observed.

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.

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 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.

The KSC Breadboard Scale Aerobic Bioreactor (B-SAB) was used to bioprocess inedible wheat crop residues to provide recycled nutrients to support crop growth in the JSC Variable Pressure Growth Chamber (VPGC) as part of the 91 day JSC-Lunar/Mars Life Support Test Project Phase III. To meet the wheat nutrient demand at JSC, the KSCB-SAB was operated at both a higher loading rate (35 gdw L-1 compared with 20 gdw L-1) and at a slower retention time (21 days compared with 8 days) than we had used in previous bioreactor (continuous stirred tank reactor - CSTR) studies. The bioreactor operated for 19 weeks-8 weeks startup and steady state stabilization then 11 weeks of operation with the broth harvested weekly. Filtered broth was amended with nutrients and transported to JSC for integration into the VPGC wheat growth component of L/MLSTP Phase III. Biodegradation of JSC wheat residues was a constant 45% during steady state bioreactor operation, and similar to previous B-SAB runs.