Effects of an anaerobic membrane bioreactor upset event on nitrogen speciation and microbial community in a downstream phototrophic membrane bioreactor†

A wastewater treatment architecture with an anaerobic membrane bioreactor and a phototrophic membrane bioreactor was created to close resource loops for use on the Moon and Mars. During an anomaly, an increase of carbon-to-nitrogen ratio led to a shift in the microbial community within PMBR. It is imperative to understand failure modes of the system and the system's ability to respond to perturbations in treatment because of their proposed application in remote, resource-limited locations. During this transient event, the carbon-to-nitrogen ratio in the AnMBR permeate increased from 0.341 to 11.2. Results showed that the microbial community became more diverse during the event and enriched in species related to the remediation of aromatic compounds. The community shift led to conditions required for greater than 90% carbon removal by the PMBR. The inclusion of the PMBR in the treatment architecture increased resilience and robustness for treating high-strength wastewaters in extreme environments.