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Activated sludge waste water processing is one of the most common technologies used in municipal waste water treatment facilities. Bioregenerative waste water treatment research at the NASA Johnson Space Center has, however, focused on the use of attached growth bioreactors due to their advantageous solids retention capability. The development of cross flow filtration methodologies in recent years has provided a means for significantly increasing solids retention time of activated sludge reactors. The settling tank traditionally used in municipal activated sludge processes for biomass retention is replaced with a microgravity compatible cross-flow biomass filter. The resulting activated sludge reactor has entirely independent solids and hydraulic retention times that may be modified as necessary to enhance processing performance. This paper describes the development of such an activated sludge bioreactor and the performance characteristics achieved to date.

A mathematical model of a fixed-film biological waste water processor has been developed for system level simulations of the Trickle Filter Bioreactor (TPB) currently operating at the NASA Johnson Space Center (JSC Hybrid Regenerative Water Recovery System (HRWRS) laboratory. The TFB model has been compared against HRWRS lab data as well as an independently developed mathematical model of a waste water processing biofilm. On a microscopic level, the fundamental equations which describe the simultaneous diffusion and reaction within the biofilm are simplified by use of polynomial substitution to provide a solution which can be solved much more rapidly than traditional finite difference solution methods. Phenomenological transport equations are used to couple the biofilm and liquid phases as well as the gas and liquid phases.

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.

A linear displacement aerometer has been developed for the measurement of the volume percent of free and dissolved gas in water samples. This paper discusses the design and testing of the prototype linear displacement aerometer that was incorporated into the Optical Water Quality Analyzer (OWQA) breadboard, an instrument that is being developed to monitor the quality of water samples on Space Station Freedom. Consumption of liquids containing excessive amounts of free or dissolved gas in microgravity can potentially cause gastrointestinal discomfort. The OWQA aerometer will determine the free and dissolved gas contents of water samples from the Space Station processed water distribution system so that potential health impacts may be assessed prior to consumption.

The measurement of ionic contaminants in samples from the potable water system on Space Station Freedom is one of the basic functions of the Crew Health Care System (CHeCS). The U. S. Environmental Protection Agency has identified ion chromatography as the analytical method of choice for measurement of anions and cations in water as described in USEPA method numbers 300.0 and 300.7, respectively. For this reason, ion chromatography was the technology initially identified to perform the ion contaminant monitoring function in the CHeCS Water Quality Subsystem. Subsequently, mass, size, and maintenance restrictions have led to a reevaluation of method options. Capillary electrophoresis (CE) has emerged as one of the more promising alternatives. CE is inherently microgravity compatible and uses an order of magnitude less reagent volume than ion chromatography. The major drawback to CE is its present state of development.