Incorporation of a Membrane-Aerated Bioreactor in a Water Recovery System

The objective of this study was to investigate the potential of membrane-aerated bioreactors as long term microgravity compatible nitrifying biological water processors (BWP). A small-scale (1/20^th) replica of the water recovery system (WRS) at JSC has been operated and extensively analyzed at Texas Tech University (TTU) for the last 3 years. The current nitrifying tubular reactor at JSC and TTU has experienced difficulty in maintaining efficiency and low maintenance. In an attempt to increase the efficiency of the biological portion of the WRS, a membrane-aerated bioreactor (MABR) was constructed and operated using the same parameters as the TTU-WRS in August 2003. The MABR is downstream of an anaerobic packed bed and is designed to promote nitrification (NH₄ → NO_x). The MABR achieved a percent nitrification of 61% and 55% for recycle ratios of 10 and 20, respectively. Performance objectives based upon Finger et al. (1999) include a microgravity compatible design, a minimum of 50% nitrification and a 365 day operation life. Other performance objectives include an increase in reliability and a reduction in astronaut maintenance time when compared to the current design.