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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.

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.

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 TIMES system was evaluated to determine its ability to process reverse osmosis (RO) brine as one of the Advanced Water Processor steps. Since preliminary testing performed in 1998 showed that the membrane typically used in the process (Nafion 117) offered a very poor ammonia rejection, a search for an alternate membrane exhibiting high ammonia rejection capability was initiated under NASA-JSC funding. This investigation has resulted in the selection of a PolyVinylAlcohol (PVA) composite membrane as a replacement. When processing RO brine and untreated human urine as feeds, the Pervap 2201 membrane showed a 96% ammonia rejection over a large range of ammonia concentration. The water permeation rates in both laboratory-scale and pilot scale testings were also similar to the Nafion. The water permeance of the Pervap 2201 was approximately 7.5 kg/h/m2/atm (1.1 lb/h/m2/psi).

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.

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.

Technologies for the recycling of water are a primary goal of NASA’s advanced life support programs. Biological processes have been identified as an attractive method for wastewater processing. A fundamental new bioreactor based on a traditional activated sludge process is demonstrated that treats hygiene wastewater using magnetic iron oxide particles agglomerated with microbial cells. In this bioreactor, microbes are suspended in magnetic flocs in a wastewater medium. Instead of a traditional gravity separator used in activated sludge operations, a magnetic separator removes the microbial flocs from the outlet stream. The reactor separation operates continuously, independent of gravitational influences. The reactor has been able to simultaneously remove 98% of high levels of both nitrogenous and organic carbon impurities from the wastewater as well as achieve acceptably low levels of total suspended solids.

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.

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.

The Early Human Testing Initiative (EHTI) Phase I Human Test, performed by the Crew and Thermal Systems Division at Johnson Space Center, demonstrated the ability of a crop of wheat to provide air revitalization for a human test subject for a 15-day period. The test demonstrated three different methods for control of oxygen and carbon dioxide concentrations for the human/plant system and obtained data on trace contaminants generated by both the human and plants during the test and their effects on each other. The crop was planted in the Variable Pressure Growth Chamber (VPGC) on July 24, 1995 and the test subject entered the adjoining airlock on day 17 of the wheat's growth cycle. The test subject stayed in the chamber for a total of 15 days, 1 hour and 20 minutes. Air was mixed between the plant chamber and airlock to provide oxygen to the test subject and carbon dioxide to the plants by an interchamber ventilation system.

As part of its integrated system test bed capability, NASA's Advanced Life Support Program has undertaken the development of a large-scale advanced life support facility capable of supporting long-duration testing of integrated, regenerative biological and physicochemical life support systems. This facility--the Advanced Life Support Human-Rated Test Facility (HRTF) is currently being built at the Johnson Space Center. The HRTF is comprised of a series of interconnected chambers with a sealed internal environment capable of supporting a test crew of four for periods exceeding one year. The life support system will consist of both biological and physicochemical components and will perform air revitalization, water recovery, food production, solid waste processing, thermal management, and integrated command and control functions. Currently, a portion of this multichamber facility has been constructed and is being outfitted with basic utilities and infrastructure.

Computer models are currently being developed by NASA and major aerospace companies to characterize regenerative life support waste water reclamation bioreactors. Detailed models increase understanding of complex processes within the bioreactors and predict performance capabilities over a wide range of operating parameters. Bench-top scale bioreactors are contributing to the development and validation of these models. The purpose of the detailed bioreactor model is to simulate the complex water purification processes as accurately as possible by minimizing the use of simplifying assumptions and empirical relationships. Fundamental equations of mass transport and microbial kinetics were implemented in a finite-difference model structure to maximize accuracy and adaptability to various bioreactor configurations. The model development is based upon concepts and data from the available literature and data from the bench top bioreactor investigations.

Bioreactor technology is currently being developed by a team of NASA and major aerospace companies to provide capabilities for water reclamation within a Regenerative Life Support System (RLSS). An integrated approach is being used for this development process consisting of fundamental laboratory studies, full-scale experimental studies and mathematical modeling. The laboratory studies are focused on a series of identical bioreactors which are being used to develop an understanding of the kinetics, growth characteristics, and viability of the microbial population in the reactors through variation of key parameters. These studies have provided insight into system control issues, development of advanced reactor design concepts, and establishment of key parameter values for the mathematical modeling effort. The full-scale experimental studies are being used to develop a complete water reclamation system founded on a biologically-based primary water processor.

Development of bioreactor technology for a regenerative life support primary water processor is ongoing by a team, composed of NASA and major aerospace companies, using a concurrent integrated approach. This approach consists of performing small-scale reactor experimental investigations, large-scale experimental studies, and computer modeling efforts on both the bioprocessor subsystem level and on the integrated water recovery system level. Bench-top experimental studies are aimed at developing an understanding of the biological process and the effect of key parameters on the process, determining the operational envelope for the regenerative life support application, and addressing process control issues. The large-scale experimental studies, in which a bioprocessor is one subsystem of an overall water recovery system, address the full-scale system integration and operational issues.

The design and operation of hybrid physical/chemical and biological life support systems for space application is a complex and difficult process. This paper describes the approach and results of an effort to characterize wheat growth, under various environmental conditions, at the Johnson Space Center's (JSC) Ambient Pressure Growth Chamber (APGC). Using a designed experiment, a test plan was developed for varying environmental parameters during a wheat growth experiment. The test plan was developed using a Central Composite approach to experimental design. As a result of the experimental runs, an empirical model of both the transpiration process and carbon dioxide assimilation for wheat growth over specified ranges of environmental parameters has been developed. The environmental parameters include carbon dioxide concentration, ambient chamber temperature, vapor pressure deficit, and air velocity.

Reclamation of purified water from waste water will be a necessity for self-sufficiency on Lunar and Martian outposts. Biological waste water treatment is advantageous because it has low temperature, low pressure, and low power requirements. Four different media were tested for use as biological growth substrates in bench-top aerobic trickling filter bioreactors in the Hybrid Regenerative Water Recovery Lab at Johnson Space Center. The four media tested included a mixture of open skeleton polypropylene spheres and cylinders, ceramic berl saddles, solid glass beads, and small rocks. The media were tested to characterize the organism inoculation rate; the steady state performance; the response to system upsets; and the column characteristics like flooding and channeling. Results indicate that the ceramic berl saddles performed best with respect to inoculation rate, steady state performance, and response to system upsets.