Have You Tried Oxygen Injection for Odor Control? MSD’s Success Story Authors: Mike Brazel (Louisville and Jefferson County MSD) Bruce Koetter, P.E. (Webster Environmental Associates, Inc.) Sharon Worley, P.E. (Webster Environmental Associates, Inc.) ABSTRACT Louisville MSD tried for years to treat the high hydrogen sulfide (H2S) in MSD’s Ohio River Force Main (ORFM) with Calcium Nitrate, but despite significant money spent, results were poor. A study recommended that MSD install an Oxygen Injection System. Since this was their first experience with this technology, MSD staff were very cautious at first. But after extensive investigation, they decided to install a system. The system has been in operation for over 3 years now and has proven very successful. The ORFM consists of two parallel PVC forcemains (16 to 24 inches diameter) with 6 cross-connections. The 8 mile long lines are routed south of the Ohio River and culminate on Main Street in downtown Louisville. There are seven pump stations that contribute flow to the ORFM but the biggest and the one furthest upstream is the Barbour Lane Pump Station. There were significant odor and corrosion concerns from the beginning which MSD tried to control using Calcium Nitrate with marginal results. The ORFM discharges into a gravity sewer manhole where there is turbulence which strips out much of the H2S. The resulting corrosion caused a major collapse of the sewer in downtown Louisville in 2017. A structural evaluation concluded that there was more severe corrosion further downstream in the gravity sewer that needed to be addressed. These findings resulted in a project to rehabilitate the gravity sewer, and it prompted MSD to pursue a new treatment method to mitigate future corrosion damage. A 2018 study showed H2S along the length of the forcemain with concentrations at one of the air release valves as high as 1,400 ppm! A thorough analysis of control alternatives concluded Oxygen Injection was the best control alternative for the ORFM. Oxygen Injection had an estimated 20-year present worth of $5.5 million, while Calcium Nitrate addition had an estimated 20-year present worth of $19.9 million. MSD had no experience with Oxygen Injection and had many concerns, but after visiting a few existing Oxygen Injection sites and completing their due diligence, they decided to move forward with the recommendation. Webster Environmental Associates, Inc. (WEA) designed the Oxygen Injection System in 2019. The construction project was completed in December of 2021 at a total capital cost of approximately $1.65 million. Results from recent monitoring show a dramatic drop in H2S when Oxygen is in use. This paper will: 1.Discuss the challenges that developed during the design and construction phases of this project. 2.Explain how these challenges were overcome. 3.Present actual performance data which will include H2S reduction percentages. 4.Present actual oxygen usage and capital and operating costs. 5.Present lessons learned and information that may be helpful to other owners/engineers considering this technology.