In collaboration with the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), the environmental biotechnology research group at Northwestern University (NU) is conducting a laboratory-scale investigation of enhanced biological phosphorus removal (EBPR) integrated with mainstream deammonification using primary effluent as feed. The research presented here includes (1) A feasibility assessment of combining a high rate activated sludge (HRAS) process with EBPR (herein HRAS-P); (2) A feasibility assessment of mainstream deammonification without bioaugmentation in suspended growth and fixed film bioreactors; and (3) A demonstration of stable and efficient integrated HRAS-P + deammonification. After an extended period of variable phosphorus removal performance, HRAS-P discharged an average effluent ortho-P concentration of 0.5 mgP/L at an SRT of 2.5 days and an HRT of 4.8 hours. This was largely achieved through the implementation of sensor-based aeration control. Current results demonstrate the potential feasibility of mainstream deammonification, and also highlight the unique performance characteristics and challenges associated with biofilm and suspended growth deammonification reactors. Efficient retention of anammox biomass was a key advantage of the biofilm reactor, but nitrite oxidizing bacteria out-competition is an ongoing challenge for both. Suspended solids management techniques that achieve selective retention of anammox and ammonium oxidizing bacteria is a crucial ongoing focus for mainstream deammonification improvement.