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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.

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.

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.

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 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.

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.