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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.

This work describes the microbiological assessment and materials compatibility of a silver-based biocide as an alternative to iodine for the Crew Exploration Vehicle (CEV) and future spacecraft potable water systems. In addition to physical and operational anti-microbial counter-measures, the prevention of microbial growth, biofilm formation, and microbiologically induced corrosion in water distribution and storage systems requires maintenance of a biologically-effective, residual biocide concentration in solution and on the wetted surfaces of the system. Because of the potential for biocide depletion in water distribution systems and the development of acquired biocide resistance within microbial populations, even sterile water with residual biocide may, over time, support the growth and/or proliferation of bacteria that pose a risk to crew health and environmental systems.

Shortly after installation of the service and performance heat exchanger (SPCU HX) in 2001, samples collected from the coolant fluid indicated the presence of nickel accompanied by a subsequent decrease in phosphate concentration along with a high microbial load. When the SPCU HX was replaced and evaluated post-flight, it was expected that the heat exchanger would have significant biofilm and corrosion present given the composition of the coolant fluid; however, there was no evidence of either. Early results from two experiments imply that the heat exchanger materials themselves are inhibiting biofilm formation. This paper discusses the results of one set of experiments and puts forward the inhibition of quorum sensing as a possible mechanism for the lack of biofilm formation.

The Lunar Mars Life Support Test Project (LMLSTP) Phase III test was the final test in a series of tests conducted to evaluate regenerative life support systems performance over increasingly longer durations. The Phase III test broke new ground for the U.S. Space Program by being the first test to look at integration of biological and physical-chemical systems for air, water and solid waste recovery for a crew of four for 91 days. Microbial bioreactors were used as the first step in the water recovery system (WRS). This biologically based WRS continuously recovered 100% of the water used by the crew consistent with NASA's strict potable standards. The air revitalization system was a combination of physical-chemical hardware and wheat plants which worked together to remove and reduce the crew's metabolically produced carbon dioxide and provide oxygen.

An integrated water recovery system was operated for 91 days in support of the Lunar Mars Life Support Test Project (LMLSTP) Phase III test. The system combined both biological and physical-chemical processes to treat a combined wastewater stream consisting of waste hygiene water, urine, and humidity condensate. Biological processes were used for primary degradation of organic material as well as for nitrification of ammonium in the wastewater. Physical-chemical systems removed inorganic salts from the water and provided post-treatment. The integrated system provided potable water to the crew throughout the test. This paper describes the water recovery system and reviews the performance of the system during the test.

Bioreactor studies and microcosm experiments were conducted to determine the degradation potential of a commercial cleansing formulation. With the possible replacement of the current cleansing formulation under consideration (Ecolab whole body shampoo containing Igepon TC-42™ as an active ingredient), determination of the degradation characteristics of the alternative formulation is necessary. The commercial formulation currently being evaluated is a modified version of Pert Plus® for Kids (PPK). The degradation potential of the PPK and main surfactant Sodium Laureth Sulfate (SLES) was determined in a packed bed denitrifying bioreactor. Results from the bioreactor studies led to the development of stoichiometric relationships to help predict and monitor SLES degradation. In addition to the degradation rates of Ecolab, the PPK formulation, as well as the four leading constituents contained in the PPK formulation was determined under denitrifying conditions in microcosm studies.

The objective of this study was to evaluate the treatment efficiency and reliability of a small-scale (1/20th) replica of the JSC biological treatment system over an extended period of time (18 months of operation). The two biological reactor components were an anaerobic packed bed for denitrification and an aerobic tubular reactor for nitrification. A recycle line (20X) linked the two biological reactors. Effectiveness of the biological system to treat a waste stream (1 L/day) containing water, urine, and soap (Igepon T42) was quantified by monitoring total nitrogen and organic carbon. Distribution of nitrogen in the effluent was measured and consisted of ammonium, nitrite, and nitrate. Daily concentrations of total nitrogen in the influent varied greatly. The system achieved 50% removal of total nitrogen and 80% removal of the influent organic carbon. The results indicate improved treatment effectiveness and resiliency with time.

Biological water processors are currently being developed for application in microgravity environments. Work has been performed to develop a single-phase, gravity independent anoxic denitrification reactor for organic carbon removal [1]. As a follow on to this work it was necessary to develop a gravity independent nitrification reactor in order to provide sufficient nitrite and nitrate to the organic carbon oxidation reactor for the complete removal of organic carbon. One approach for providing the significant amounts of dissolved oxygen required for nitrification is to require the biological reactor design to process two-phase gas and liquid in micro-gravity. This paper addresses the design and test results overview for development of a tubular, two-phase, gravity independent nitrification biological water processor.

The work presented in this paper summarizes the performance of subsystems used during an integrated advanced water recovery system test conducted by the Crew and Thermal Systems Division (CTSD) at NASA-Johnson Space Center (JSC). The overall objective of this test was to demonstrate the capability of an integrated advanced water recovery system to produce potable quality water for at least six months. Each subsystem was designed for operation in microgravity. The primary treatment system consisted of a biological system for organic carbon and ammonia removal. Dissolved solids were removed by reverse osmosis and air evaporation systems. Finally, ion exchange technology in combination with photolysis or photocatalysis was used for polishing of the effluent water stream. The wastewater stream consisted of urine and urine flush water, hygiene wastewater and a simulated humidity condensate.

The work presented in this paper summarizes the early results of an integrated advanced water recovery system test conducted by the Crew and Thermal Systems Division (CTSD) at NASA-Johnson Space Center (JSC). The system design and the results of the first two months of operation are presented. The overall objective of this test is to demonstrate the capability of an integrated advanced water recovery system to produce potable quality water for at least six months. Each subsystem is designed for operation in microgravity. The primary treatment system consists of a biological system for organic carbon and ammonia removal. Dissolved solids are removed by reverse osmosis and air evaporation systems. Finally, ion exchange technology in combination with photolysis or photocatalysis is used for polishing of the effluent water stream. The wastewater stream consists of urine and urine flush water, hygiene wastewater and a simulated humidity condensate.

Biological wastewater processing has been under investigation by AlliedSignal Aerospace and NASA Johnson Space Center (JSC) for future use in space. Testing at JSC in the Hybrid Regenerative Water Recovery System (HRWRS) in preparation for future closed human testing has been performed. Computer models have been developed to aid in the design of a new four-person immobilized cell bioreactor. The design of the reactor and validation of the computer model is presented. In addition, the total organic carbon (TOC) computer model has been expanded to begin investigation of nitrification. This model is being developed to identify the key parameters of the nitrification process, and to improve the design and operating conditions of nitrifying bioreactors. In addition, the model can be used as a design tool to rapidly predict the effects of changes in operational conditions and reactor design, significantly reducing the number and duration of experiments required.

A series of studies examined bacterial diversity and consortial stability in an anoxic bioreactor and correlated diversity and stability with functional performance, mechanical reliability, and stability. The evaluation was divided into four studies. During Study 1, replicate biological water processor (BWP) systems were operated to evaluate variability in the microbial diversity over time as a function of the initial consortia used for inoculation of the BWP reactors. Study 2 was designed to investigate the impact of an inoculum source on BWP performance. Study 3 was a modification of Study 2 where the primary focus was BWP performance and consortia change from inoculation until steady state operations. In Study 4, the reactors were divided into three different operational periods, based on the operational periods of the integrated water recovery test at the Johnson Space Center (JSC) in 2001.

Ground-based laboratory and closed-chamber human tests have demonstrated the ability of microbial-based biological processors to effectively remove carbon and nitrogen species from regenerable life support wastewater streams. Application of this technology to crewed spacecraft requires the development of gravity-independent bioprocessors due to a lack of buoyancy-driven convection and sedimentation in microgravity. This paper reports on the development and testing of membranebased biological reactors and addresses the processing of planetary and International Space Station (ISS) waste streams. The membranes provide phase separation between the wastewater and metabolically required oxygen, accommodate diffusion-driven oxygen transport, and provide surface area for microbial biofilm attachment. Testing of prototype membrane bioprocessors has been completed.