Performance of a lab-scale membrane aerated biofilm reactor treating nitrogen dominant space-based wastewater through simultaneous nitrification-denitrification

A membrane-aerated biofilm reactor (MABR) was designed for the treatment of a source-separated urine wastewater formulated to mimic conditions on an early planetary space habitation. Literature suggested that a MABR would not work effectively for nitrogen removal for this wastewater since it is nitrogen dominant (total organic carbon to nitrogen ratio < 1). The MABR studied in this study confirmed that hypothesis by recording average nitrification and denitrification efficiencies as high as ~65 % and ~35 %, respectively. Nonetheless, the simultaneous nitrification and denitrification performance was unexpectedly high when compared to the reactor's low liquid velocities (0.004 cm/s) and it's relatively high bulk dissolved oxygen (DO) levels (> 2 mg/L). Dissolved organic carbon (DOC) removal and nitrification rates were reported as high as 0.33 ± 0.12 g-C/m²-d and 0.32 ± 0.02 g-N/m²-d, respectively. Additionally, the MABR achieved total nitrogen (TN) removal efficiency of 36.5 %. Additionally, the operational parameters of hydraulic retention time, intramembrane partial oxygen pressure, recycle ratio and liquid velocity linked with bulk DO concentration were evaluated. It was observed that TN removal was significantly impacted by the variation of those parameters, but DOC removal efficiency and nitrification rate did not change significantly. This study helps to establish the efficacy of MABR systems for the treatment of nitrogen dominant, space-based wastewater.