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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.

The ability to aseptically remove samples and products, and the capability for addition of materials to sterile or otherwise microbially susceptible systems have always been compromised by the lack of a reliable means of sterilizing the mating fixtures. Cultures of mammalian cells are particularly vulnerable to microbial contamination due to the complexity of nutrient media and the lengthy periods required for cell growth. The Microwave Sterilizable Access Port has been developed to overcome this limitation. The system consists of three primary components: a microwave power source, a combined sterilization chamber/in-line valve port assembly, and a specimen transfer interface. Microwave energy is transmitted via coaxial cable to a small pressurized chamber that serves as a sterile transition between the surrounding environment and the system during transfer of materials.

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.

The thermal pretreatment of waste hygiene water was investigated as an approach to reduce the amount of energy required to maintain overall system microbial control. The study was conducted in two phases. The laboratory phase was a series of experiments to quantify the degree of microbial population reduction obtained when hygiene waste water and humidity condensate are heated through various thermal cycles. The laboratory phase also included inoculation of the combined wastewater with a thermophilic bacteria to provide a “worst-case” challenge of the thermal cycle being tested. The large scale system phase determined biofilm formation on the surfaces of a variety of materials with and without thermal cycling. Except for survival of the challenge thermophile and some naturally present thermophiles, thermal treatment above 85° C was successful in eradication of the microbial population in the combined hygiene wastewater and formed biofilms.