Application of intermittent aeration in nitrogen removal process: development, advantages and mechanisms

Intermittent aeration has been shown to be one of the most effective and cost-effective strategies for biological wastewater treatment. This review presents an overview of the application and advantages of intermittent aeration, with the mechanisms of improvement in process stability discussed. Intermittent aeration was applied to maximize the utilization of organic carbon for denitrification rather than oxidized by O2. Under that condition, advanced nitrogen removal and sludge settleability were achieved and the energy consumption and N2O emissions were reduced. With the discovery that nitrite oxidation bacteria are selectively inhibited while ammonium oxidation bacteria are less affected under intermittent aeration conditions, intermittent aeration has been applied to the partial nitrification process. Furthermore, the non-aerated phases of intermittent aeration have been found to facilitate the synergism of anaerobic ammonium oxidizing bacteria (AnAOB) and denitrifying bacteria, providing a suitable environment for AnAOB growth. Therefore, intermittent aeration is considered to be an effective operational strategy for anammox-based processes, such as single-stage partial nitrification-anammox. In addition, simultaneous nutrient removal and sludge reduction could also be achieved. In order to regulate the synergism of microbial species, dissolved oxygen (DO) concentrations and the durations of aerated and non-aerated periods can be adjusted based on the monitored parameters such as nitrogen concentrations, pH and oxidation reduction potential profiles. Finally, the current limitations, gaps in knowledge and the areas requiring further research are proposed.