Nutrient management at water resource recovery facilities (WRRFs) is crucial for addressing water quality issues, especially in watersheds facing rapid urbanization and population growth. Conventional biological nutrient removal (BNR) technologies are generally effective at meeting water quality goals, but they are energy-intensive and costly. Therefore, new approaches are needed to intensify treatment processes, reduce energy demand, and reduce chemical dependency. This project will explore the application of low dissolved oxygen (DO) BNR in existing activated sludge as an alternative treatment method. Guidance on implementing low DO BNR will be developed, outlining the fundamental mechanisms associated with low DO BNR operation; a decision tree for low DO BNR to assist in utility decision-making processes; and design, operation, and process modeling guidelines for low DO BNR.