Trotter and Associates assisted the Village of Glendale Heights in implementing the phosphorus removal upgrades at their wastewater treatment facility. The existing biological process utilized single stage nitrification which took place within the four aeration basins. As part of the project these basins have been converted to an A2O process. Baffle walls were installed to create separate anaerobic, anoxic, and aerobic zones. Additionally, submersible mixers were installed and an internal recycle pump conveys nitrified MLSS to the anoxic zone for denitrification. Chemical polishing facilities were constructed to allow dosing of alum upstream of the secondary clarifiers or prior to solids dewatering. The improvements were completed in October 2024, and TAI is now assisting the Village with process monitoring and optimization.