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Removal of low-molecular weight, polar, non-ionic contaminants such as urea and alcohols from aqueous solution is being accomplished using immobilized enzyme technology. Immobilized urease is used to catalyze urea hydrolysis for subsequent removal as ammonia. An alcohol oxidase enzyme-based catalyst is used to catalyze oxidation of alcohols, aldehydes, and similar compounds to organic acids, which are removed by ion exchange. Fixed bed reactors were successfully developed and delivered to NASA-MSFC for a segment of the Phase III Core Module Integrated Facility (CMIF) Water Recovery Test. Wastewater generated in the End-use Equipment Facility (EEF) was purified using a combination of Multifiltration Unibeds and Enzyme Unibeds. The enzyme beds effectively removed the targeted organics to levels below detection limits (<100-400 ppb). Also, based on the amount of TOC removed, the enzyme beds removed unidentified organic contaminants beyond those specifically targeted.

The investigation and development of a chemiluminescence based ethanol detection concept into a biosensor system is described. The biosensor uses alcohol oxidase to catalyze the reaction of short chain primary alcohols with elemental oxygen to produce hydrogen peroxide and the corresponding aldehyde. The reaction of hydrogen peroxide with an organic luminophore in the presence of a sufficient electric field results in emission of blue light with peak intensity at 425nm. The chemiluminescent light intensity is directly proportional to the alcohol concentration of the sample. The aqueous phase chemistry required for sensor operation is implemented using solid phase modules which adjust the pH of the influent stream, catalyze the oxidation of alcohol, provide the controlled addition of the luminophore to the flowing aqueous stream, and minimize the requirement for expendables. Precise control of the pH has proven essential for the long-term sustained release of the luminophore.

On the International Space Station (ISS), humidity condensate will be collected from the atmosphere and treated by multifiltration to produce potable water for use by the crews. Ground-based development tests have demonstrated that multifiltration beds filled with a series of ion-exchange resins and activated carbons can remove many inorganic and organic contaminants effectively from wastewaters. As a precursor to the use of this technology on the ISS, a demonstration of multifiltration treatment under microgravity conditions was undertaken. On the Space Shuttle, humidity condensate from cabin air is recovered in the atmosphere revitalization system, then stored and periodically vented to space vacuum. A Shuttle Condensate Adsorption Device (SCAD) containing sorbent materials similar to those planned for use on the ISS was developed and flown on STS-68 as a continuation of DSO 317, which was flown initially on STS-45 and STS-47.

The initial development effort is described for an electrochemical hydrogen peroxide generator and pervaporation module capable of producing and delivering hydrogen peroxide to a contaminated waste water stream as an oxidant or to a pure water stream for use as a disinfectant. A three chambered cell is used to generate hydrogen peroxide by a combined electrodialysis and electrochemical process. Each chamber is separated from its neighbor by a membrane allowing selective production of peroxide anions and hydrogen ions under controlled pH conditions followed by migration to form hydrogen peroxide. Concentrations greater than 6,500mg/L have been produced in this manner. The effects of voltage, pH, membranes, electrode materials, and method of oxygen introduction are delineated. Hydrogen peroxide is then transferred to the end-use stream by pervaporation. The impact of pH, relative flow rates, and ionic strength of sink and source solutions on pervaporation rates is detailed.