Intermittent Aeration Increases Oxygen Transfer Efficiency In Flow-through MABRs: a Laboratory-scale Demonstration

Membrane-aerated biofilm reactors (MABRs) are an energy-efficient technology for nutrient and carbon removal; yet, a trade-off remains between their rate and efficiency of oxygen transfer. We operated nitrifying flow-through MABRs under continuous or intermittent aeration modes. The continuously- and intermittently-aerated MABRs nitrified ammonia at similar rates, even as the (calculated) absolute oxygen partial pressure on the gas side dropped to 0.05 atm during the no-aeration phase. The ammonia-oxidizing bacteria in the intermittently-aerated MABRs were dominated by Nitrosospira, previously shown to be abundant at low oxygen concentrations and provide reactor stability under changing conditions. Intermittent aeration did not affect trace organic chemical transformation, which continued under anoxic conditions and may therefore be driven by heterotrophic bacteria. Our results suggest that intermittent aeration can allow for high oxygen transfer efficiencies and high removal rates, which are facilitated by biofilm adaptation.