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A Microwave Enhanced Solid Waste Freeze Drying Prototype system has been developed for the treatment of solid waste materials generated during extended manned space missions. The system recovers water initially contained within wastes and stabilizes the residue with respect to microbial growth. Dry waste may then be safely stored or passed on to the next waste treatment process. Operating under vacuum, microwave power provides the energy necessary for sublimation of ice contained within the waste. This water vapor is subsequently collected as relatively pure ice on a Peltier thermoelectric condenser as it travels en route to the vacuum pump. In addition to stabilization via dehydration, microwave enhanced Freeze Drying reduces the microbial population (∼90%) in the waste.

The on-demand production of Medical Grade Water (MGW) is a critical biomedical requirement for future long-duration exploration missions. Potentially, large volumes of MGW may be needed to treat burn victims, with lesser amounts required to reconstitute pharmacological agents for medical preparations and biological experiments, and to formulate parenteral fluids during medical treatment. Storage of MGW is an untenable means to meet this requirement, as are nominal MGW production methods, which use a complex set of processes to remove chemical contaminants, inactivate all microorganisms, and eliminate endotoxins, a toxin originating from gram-negative bacteria cell walls. An innovative microgravity compatible alternative, using a microwave-based MGW generator, is described in this paper. The MGW generator efficiently couples microwaves to a single-phase flowing stream, resulting in super-autoclave temperatures.

The active control of problematic microbial populations aboard spacecraft, and within future lunar and planetary habitats is a fundamental Advanced Life Support (ALS) requirement to ensure the long-term protection of crewmembers from infectious disease, and to shield materials and equipment from biofouling and biodegradation. The development of effective antimicrobial coatings and materials is an important first step towards achieving this goal and was the focus of our research. A variety of materials were coated with antibacterial and antifungal agents using covalent linkages. Substrates included both granular media and materials of construction. Granular media may be employed to reduce the number of viable microorganisms within flowing aqueous streams, to inhibit the colonization and formation of biofilms within piping, tubing and instrumentation, and to amplify the biocidal activity of low aqueous iodine concentrations.

Small, highly polar organics such as urea, alcohols, acetone, and glycols are not easily removed by the International Space Station's Water Recovery System. The current design utilizes the Volatile Removal Assembly (VRA) which operates at 125°C to catalytically oxidize these contaminants. Since decomposition of these organics under milder conditions would be beneficial, several ambient temperature biocatalytic and catalytic processes were evaluated in our laboratory. Enzymatic oxidation and ambient temperature heterogeneous catalytic oxidation of these contaminants were explored. Oxidation of alcohols proceeded rapidly using alcohol oxidase; however, effective enzymes to degrade other contaminants except urea were not found. Importantly, both alcohols and glycols were efficiently oxidized at ambient temperature using a highly active, bimetallic noble metal catalyst.

A Microwave Powered Solid Waste Stabilization and Water Recovery Prototype system has been developed for the treatment of solid waste materials generated during extended manned space missions. The system recovers water initially contained within wastes and stabilizes the residue with respect to microbial growth. Dry waste may then be safely stored or passed on to the next waste treatment process. Using microwave power, water present in the solid waste is selectively and rapidly heated. Liquid phase water flashes to steam and superheats. Hot water and steam formed in the interior of waste particles create an environment that is lethal to bacteria, yeasts, molds, and viruses. Steam contacts exposed surfaces and provides an effective thermal kill of microbes, in a manner similar to that of an autoclave. Volatilized water vapor is recovered by condensation.

Solid wastes can be separated from aqueous streams and concentrated by filtration in a magnetically assisted fluidized bed. In this work the filtration of solid waste materials using filter beds consisting of granular ferromagnetic media is demonstrated. The degree of bed consolidation (or conversely fluidization) is controlled by the application of magnetic forces. In the Magnetically Assisted Gasification (MAG) process, solids are first entrapped by filtration, and then fluidized and transferred to a high temperature reactor where they are thermally decomposed. The maximum particle loading for the filter bed is determined by the intergranular void space. Using magnetic methods, it is possible to manipulate the degree of compaction as the filtration progresses to increase the void space and thereby maximize the loading capacity and efficiency of the filter. This process is completely compatible with operation in microgravity and hypogravity.

Novel mesoporous bimetallic oxidation catalysts are described, which are currently under development for the deep oxidation (mineralization) of aqueous organic contaminants in wastewater produced on-board manned spacecraft, and lunar and planetary habitats. The goal of the ongoing development program is to produce catalysts capable of organic contaminant mineralization near ambient temperature. Such a development will significantly reduce Equivalent System Mass (ESM) for the ISS Water Processor Assembly (WPA), which must operate at 135°C to convert organic carbon to CO2 and carboxylic acids. Improvements in catalyst performance were achieved due to the unique structural characteristics of mesoporous materials, which include a three-dimensional network of partially ordered interconnected mesopores (5-25 nm).

The electrosynthesis of expendable reagents including acids, bases, and oxidants from simple salts or salt mixtures has been demonstrated using a variety of electrochemical cells. A five chambered electrodialytic water splitting (EDWS) cell with bipolar membranes was utilized to efficiently convert sodium sulfate, sodium chloride, potassium nitrate, and potassium chloride to conjugate acids and bases. With the same cell, selective segregation of cations and anions from mixed salt solutions occurred, resulting in relatively pure acids and bases. These results suggest that pure acids and bases can be produced from composite spacecraft brines. Chemical oxidants such as sodium and ammonium persulfate were also synthesized with high current efficiencies by the electrooxidation of salts and acids in a two chambered electrochemical cell.