Performance Evaluation of a Submerged-Membrane Bioreactor for Lunar Applications

An aerobic submerged membrane bioreactor was evaluated at Kennedy Space Center for possible use in lunar applications treating generated wastewater streams. The bioreactor contained an internal membrane (pore size = 0.2 μm), which allows for an infinite mean cell residence time (SRT) and also improved effluent quality. An analog waste stream simulating a the daily output of a 2-person crew was fed to the reactor continuously. The simulated waste stream contained a mixture of two surfactants and a urine analog. In previous studies at KSC, complete surfactant degradation was observed, however no nitrification (NH₄⁺ → NO₂^– and NO₃^–) was established. The goals of this study were to establish both surfactant and nitrifying bacterial populations. To promote the establishment of nitrifying populations, pH control and the addition of a nitrifying inoculm were implemented into the study. Results from the study show that 100 % surfactant disappearance was achieved in the reactor. Nitrification was also established during the study (180 day duration). Rates associated with nitrification varied dependent on set pH values, with 30% obtained at pH = 6.7 and 80% at pH = 7.5.