Thermophilic Aerobic Solid Waste Processing for Long-Term Crewed Missions

Biodegradation of wastes generated during a long-term crewed space mission is very promising to reduce waste volume, facilitate recycling of water, carbon, and nutrients and to reduce the resupply needs of such missions. Thermophilic aerobic digestion of biodegradable wastes is under investigation as part of the NASA Center of Research and Training (NSCORT) at Purdue University. The Solids Thermophilic Aerobic Reactor (STAR) is under investigation for the initial treatment of all biodegradable solid wastes that would be generated in a crewed mission, including inedible plant wastes, paper, fecal matter, and food wastes. The projected advantages of the STAR system include a reduced retention time, increased rapid pathogen inactivation, lower reactor volume requirements, and ease of automation as compared to other biological waste treatment systems. Preliminary optimization of the system relative to influent solids loading and start-up pH control are reported. The optimal influent solids loading was determined to be 8% total solids, with an HRT of 10 days. It was determined that initial pH control for the first 8 hours of system start-up was required for successful start-up and optimum performance.