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Electrochemical oxidant generation has been combined with UV photolysis to provide a highly effective means of water purification, decomposition of bacterial organic substances, microbiological control and sterilization. Ozone is an oxidant with many unique features that make it a valuable tool for biomedical applications. It is an excellent bactericidal, virucidal and sporicidal agent making it ideal for use as a sterilant. Combining O3 with UV radiation stimulates formation of hydroxyl radicals (OH·) which accelerates a wide range of organic oxidations. While in some instances maintenance of an oxidant residual is necessary, the residual can be rapidly removed by UV light at the point of use (i.e., Water For Injection). Test results on pyrogen decomposition, bacterial organic decomposition, microbiological sterilization, residual removal and water purification as a final step for producing pharmaceutical grade water are discussed.

The recovery of resources for reuse from the processing of diverse waste materials produced by a crew in space-based closed life support systems is essential for the success of long duration space missions. Lynntech, Inc. is investigating and developing a waste processor that uses thermal solubilization and wet oxidation at elevated pressure and an electrochemical process for solid waste processing for closed life support systems. The electrochemical process uses a packed bed anode that oxidizes waste at temperatures <100°C and operates at atmospheric pressure. This approach offers an alternative to high temperature thermal processes for solid waste treatment. Incorporated into the packed bed reactor design is a method that shows potential for regenerating a liquid electrolyte enabling the electrochemical process to operate for long periods without having to be replaced.

This paper addresses the development of a novel technology to simultaneously reduce total organic carbon (TOC) and microbial count (MC) in biological water processor (BWP) processed water. This approach also creates a biocidal environment in BWP processed water before being fed into the reverse osmosis (RO) and post processing systems. The technology is based on an advanced oxidation process using an on-demand oxidizer generator, which does not require consumable chemicals. The SBIR (Small Business Innovation Research) Phase I feasibility studies successfully demonstrated the process efficacy in the reduction of both TOC and MC of the BWP effluent. Also, the residual disinfectant and reduced TOC in the treated effluent minimized fouling the RO membrane and water lines. In the Phase II project, a prototype is being fabricated and evaluated for its ability to reduce TOC and MC, and extend RO membrane life.

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.

Monitoring the quality of astronaut potable and hygiene water is one of the highest priorities of a regenerative life support system for manned space missions to the ISS, Moon, Mars, and other remote locations. Real-time monitoring allows analysis of water processing from wastewater to potable water and would enable the rapid diagnosis and correction of a processing failure if a water-related health issue were to arise. Among detectors used to monitor recycled water quality, a total organic carbon (TOC) instrument or its functional equivalent should be used to assess the organic contaminant level. Through the NASA Small Business Innovative Research (SBIR) program, Lynntech has developed a novel, mesofluidic Total Organic Carbon Analyzer (TOCA) for real-time monitoring of water quality. It has been designed for an operational lifetime of 5 years with no maintenance required and no need to supply reagents or water.

A microelectrode-based electrochemical detection method was used for quantitation of bacteria in water samples. The redox mediator, benzoquinone, was used to accept electrons from the bacterial metabolic pathway to create a flow of electrons by reducing the mediator. Electrochemical monitoring electrodes detected the reduced mediator as it diffused out of the cells and produced a small electrical current. By using a combination of microelectrodes and monitoring instrumentation, the cumulative current generated by a particular bacterial population could be monitored. Using commercially available components, an electrochemical detection system was assembled and tested to evaluate its potential as an emerging technology for rapid detection and quantitation of bacteria in water samples.

In bioregenerative life support systems, crop residues represent a source of biochemical energy for production of chemicals, pulp products and secondary foods. Hydrolysis of the structural carbohydrates in biomass produces edible glucose as well as various 5-carbon sugars usable by microorganisms. However, the biomass must be pretreated before hydrolysis to remove minerals useful as plant nutrients, break down lignin, and improve access of the enzymes to the carbohydrates. Some pre-treatments also hydrolyze part or all of the hemicellulose, leaving purified cellulose. For use in space, pretreatments must be safe, rapid and as complete as practicable. This paper will present a process comparison of three “space-compatible” pretreatment methods for lignocellu-losic crop residues from bioregenerative life support systems. Ozonation, alkaline hydrogen peroxide, and strong alkali treatment use only regenerable materials and mild processing conditions.

Water is the single largest resource required for crew sustenance during long-term human space missions. To preserve this resource, water must be reclaimed from waste streams containing minimum concentrations of organic and inorganic impurities. The removal of dissolved ions from waste water is essential to regenerative water reclamation technology for life support systems. The aim of this project was to demonstrate a novel electrochemically driven purification method using tubulated bipolar ion exchange membranes for the separation of dissolved ionic impurities from spacecraft waste water. Generally, electrochemical separation methods have limited applications since they can only be applied to the purification of the water that has a sufficiently high dissolved ion content to make the solution conductive. The new method, however, uses a membrane composed of bilayers of oppositely charged ionically conducting polymers.

A compact, low-power, electrochemically driven fluid cooling pump is currently being developed by Lynntech. With no electric motor and lightweight components, the pump is significantly lighter than conventional rotodynamic and displacement pumps. Reliability and robustness are achieved with the absence of rotating or moving components (apart from the bellows). By employing sulfonated polystyrene-based proton exchange membranes rather than conventional Nafion® membranes, a significant reduction in the actuator power consumption was demonstrated. Lynntech designers also demonstrated that these membranes possess the mechanical strength, durability, and temperature range that are necessary for long-life space operation. The preliminary design for a prototype pump compares very favorably to the design targets of the next generation spacesuit Portable Life Support Systems cooling pump.

The removal of dissolved ions from waste water is essential for water repurification on long-term human space missions. Lynntech, Inc., has demonstrated a novel electrochemically driven purification method using tubulated bipolar ion exchange membranes for the separation of dissolved inorganic impurities as well as charged organic species from waste water. Generally, electrochemical separation methods have limited applications since they can only be applied to the purification of water that has a sufficiently high dissolved ion content to make the water conductive. The novel tubulated bipolar membranes composed of bilayers of oppositely charged ionically conducting polymers can be used to overcome this limitation. This paper deals with the scaling-up of such a device to increase the throughput to process about 100 liters of waste water per day. This is achieved by using stacks of tubulated bipolar membranes.

The post-treatment purification of water recovered from hygiene, metabolic and humidity condensate waste water is essential to regenerative water reclamation technology life support systems. Lynntech, Inc., working with NASA-JSC has developed an electrochemical reactor that generates ozone and hydrogen peroxide. The electrochemical reactor is the basis for an advanced oxidation process in which electrochemically generated oxidants are used in combination with ultraviolet irradiation to produce hydroxyl radicals in a reclaimed water stream which in turn oxidize dissolved organic impurities to carbon dioxide. This paper describes the design and fabrication of an automated breadboard reactor system based on this principle. The system operates at low temperature and requires no chemical expendables. Kinetics and performance test results are presented showing the removal of organic impurities and disinfection features to produce potable water quality.