Microwave Enhanced Freeze Drying of Solid Waste 2007-01-3266

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. Benefits of microwave power include speed-of-light energy transfer and selective heating of water by direct absorption of electromagnetic radiation, thus minimizing conductive and convective losses, and reducing drying times relative to more conventional Freeze Drying processes. This translates directly into reduced size and power requirements, and lower Equivalent System Mass (ESM). Stabilization with respect to microbial growth has been demonstrated using a variety of bacteria and fungi challenge organisms. Water recoveries greater than 98% have been achieved using this technology.