Louisville Metropolitan Sewer District (MSD) is the main provider of sanitary sewer, stormwater management, and flood protection for Jefferson County and Louisville Metro. MSD currently operates five (5) Water Quality Treatment Centers (WQTC) within Jefferson County treating nearly 154 million gallons of wastewater per day. In 2018, a new Kentucky law allowed utilities like MSD to own assets outside of their originally chartered borders. Since that time, MSD has acquired several wastewater systems in the surrounding counties. In 2021, MSD took ownership of facilities previously operated by the Bullitt County Sanitation District (BCSD) which serve 4,200 residential customers via eight (8) small "package" wastewater treatment plants. Initial inspection of the wastewater treatment plants indicated that many aspects of the plants had reached their useful life, and improvements were required to continue effective operation. MSD contracted HDR to provide professional services to evaluate and design disinfection process improvements at five (5) WQTC within the BCSD service area: Bullitt Hills, Hillview No. 1, Hillview No. 2, Hillview No. 3, Willabrook, and Pioneer Village. In the preliminary project stages, HDR evaluated two (2) disinfection alternatives: Peracetic Acid (PAA) and UV Disinfection. Keeping client input and industry standards in mind, an analysis was conducted on both alternatives comparing dosing rates, chemical storage, constructability, and safety. Once the evaluation was complete, HDR held a meeting with MSD stakeholders to determine which treatment process was preferred. Design for Pioneer Village WQTC and Hillview No. 3 WQTC was completed in 2023 and construction started in 2024. This presentation will compare the advantages and disadvantages of PAA and UV Disinfection related to wastewater treatment at the five (5) WQTC’s, provide an overview of site constraints and client preferences influencing the decision process, evaluate the preferred disinfection treatment, and give a brief overview of the current progress of the design and construction.