Biological treatment of a synthetic space mission wastewater using a membrane-aerated,membrane-coupled bioreactor (M2BR)

This paper describes the membrane-aerated, membrane-coupled bioreactor (M2BR), which was developed for wastewater treatment during long-term space missions because it achieves aeration and biomass separation using components that are compatible with microgravity conditions. In the experiments described herein, the M2BR was used to treat a synthetic wastewater formulated by NASA to simulate the wastewater typically collected during space missions. The M2BR was able to achieve more than 90% removal of both chemical oxygen demand (COD) and total nitrogen when it was fed a modified NASA wastewater that had a 4:1 COD to nitrogen ratio. When the full-strength synthetic wastewater was fed to the M2BR (COD:N=1), however, the nitrogenous pollutant removal efficiency was adversely affected because of either insufficient oxygen transfer to support nitrification (an air-fed M2BR) or insufficient electron donor to support denitrification (an oxygen-fed M2BR). In conclusion, the M2BR provides considerable promise for wastewater treatment during long-term space missions, although additional research is needed to identify the best approach to treat the space mission wastewater, which poses a unique challenge because of its low COD:N ratio.