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This paper discusses the recent developments in water quality monitoring for Space Station reclaimed wastewaters. A preprototype unit that contains an ultraviolet absorbance organic carbon monitor integrated with pH and conductivity sensors is presented. The preprototype has provisions for automated operation and is a reagentless flow-through system without any gas/liquid interfaces. The organic carbon monitor detects by ultraviolet absorbance the organic impurities in reclaimed wastewater which may be correlated to the organic carbon content of the water. A comparison of the preprototype organic carbon detection values with actual total organic carbon measurements is presented. The electrolyte double junction concept for the pH sensor and fixed electrodes for both the pH and conductivity sensors are discussed. In addition, the development of a reagentless organic carbon analyzer that incorporates ultraviolet oxidation and infrared detection is presented.

The purification of reclaimed water is essential to water reclamation technology life-support systems in lunar/Mars habitats. Lynntech, Inc., working with NASA-JSC, is developing an electrochemical UV reactor which generates oxidants, operates at low temperatures and requires no chemical expendables. The reactor is the basis for an advanced oxidation process, in which electrochemically generated ozone and hydrogen peroxide are used, in combination with ultraviolet light irradiation, to produce hydroxyl radicals. Results from this process are presented which demonstrate concept feasibility for removal of organic impurities and disinfection of water for potable and hygiene reuse. Power, size requirements, Faradaic efficiency and process reaction kinetics are discussed. At the completion of this development effort, the reactor system will be installed in JSC's regenerative water recovery test facility for evaluation to compare this technique with other candidate processes.

Electrooxidation is a means of removing organic solutes directly from waste waters without the use of chemical expendables. Research sponsored by NASA Johnson Space Center is currently being pursued at Texas A&M University to demonstrate the feasibility of the concept for oxidation of organic impurities common to urine, shower waters and space habitat humidity condensates. Electrooxidation of urine and waste water ersatz was experimentally demonstrated. This paper discusses the electrooxidation principle, reaction kinetics, efficiency, power, size, experimental test results and water reclamation applications. Process operating potentials and the use of anodic oxidation potentials that are sufficiently low to avoid oxygen formation and chloride oxidation are described. The design of a novel electrochemical system that incorporates a membrane-based electrolyte based on parametric test data and current fuel cell technology is presented.

A single cell electrochemical reactor that utilizes a proton exchange membrane (PEM) as a solid electrolyte is being investigated and developed at Texas A&M University for post-treatment of reclaimed waters with low or negligible electrolyte content. Post-treatment is a final polishing of reclaimed waste waters prior to reuse and constitutes removing organic impurities at levels as high as 100 ppm to <500 ppb total organic carbon (TOC) content and provides disinfection. The system does not utilize or produce either expendable hardware components or chemicals and has no moving parts. This paper discusses a single cell reactor concept; test system design; the role of the proton exchange membrane; and the principle of organic impurity oxidation at PEM interfacial reaction zones. The fabrication performance evaluation; design and sizing of a prototype system are discussed. Test data and kinetic analysis are presented.

An aqueous phase catalytic oxidation system (APCOS) was designed, tested and delivered to NASA/Johnson Space Center (JSC). The APCOS removes residual organic impurities in reclaimed water to a level acceptable for potable use and to provide disinfection. The reactor, which contains a heterogeneous catalyst consisting of a noble metal on an inert support medium, operates at 120 - 150 °C and at fluid pressures of several atmospheres to maintain an aqueous liquid phase. Pressurized gaseous oxygen, used as the oxidant, is directly injected into the liquid phase. A description of the subsystems process hardware is presented. The APCOS was demonstrated to mineralize organic impurities at concentrations of 100 mg/L total organic carbon (TOC) to < .5 mg/L (<500 μg/L TOC). In addition, disinfection features were demonstrated with microbial challenge tests.

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.

Long duration manned space missions will require integrated biological and physicochemical processes for recovery of resources from wastes. This paper discusses a hybrid regenerative biological and physicochemical water recovery system designed and built at NASA's Crew and Thermal Systems Division (CTSD) at Johnson Space Center (JSC). The system is sized for a four-person crew and consists of a two-stage, aerobic, trickling filter bioreactor; a reverse osmosis system; and a photocatalytic oxidation system. The system was designed to accommodate high organic and inorganic loadings and a low hydraulic loading. The bioreactor was designed to oxidize organics to carbon dioxide and water; the reverse osmosis system reduces inorganic content to potable quality; and the photocatalytic oxidation unit removes residual organic impurities (part per million range) and provides in-situ disinfection. The design and performance of the hybrid system for producing potable/hygiene water is described.