Monday, September 9, 2024
1:30 PM - 2:00 PM
Bye-Bye Rail Cars! Nashville Central's 350 MGD UV Disinfection Facility is Online!
Engineering & Construction

Nashville Metro Water Services’ (MWS) Central Water Reclamation Facility (WRF) has disinfected its treated plant effluent using gaseous chlorine since the facility was originally commissioned in 1958. Sixty-five years later, after 10+ years of planning, design, and construction, a new 350 MGD ultraviolet (UV) disinfection facility was commissioned, and the last 90-ton rail cars were removed from the site. The new UV facility is believed to be one of, if not the largest secondary effluent UV installation in the United States. It is a marquee component of the $400 million Capacity Improvements and CSO Reduction project (Central Optimization), which has increased the Central WRF’s wet weather secondary treatment capacity from 220 to 350 MGD and made the facility easier to operate and maintain. This presentation will provide information related to the new UV disinfection facility and summarize the highlights of each phase of this completed project from the initial planning through commissioning. Over a year of performance data, O&M experience, and “if we could do it all over again insight will be presented by the Central WRF plant manager and the design engineer of record. Utilities, consultants, contractors, and others who are preparing to upgrade their clean water disinfection systems can greatly benefit from this project’s experience and lessons learned. Presentation Highlights Include: --Evaluation of multiple disinfection technologies with cost and non-cost considerations to determine most beneficial long-term solution for MWS. UV disinfection was selected over sodium hypochlorite (bulk and onsite generation), peracetic acid (PAA), ozone. --Low Pressure detailed design collaboration workshops with a cross-section of MWS operations and maintenance staff were critical to the success of this project. These workshops provided an opportunity for the engineer to listen, understand and incorporate MWS’ ideas and preferences into the design and fostered ownership and buy-in from the MWS staff who will “own” the facility once construction is complete. --UV System Overview: TrojanUVSigna® with six ~50-foot long, 9-foot wide channels, two banks per channel, 96 lamps per channel (total 1152 lamps in 12 banks). Lamp drivers are housed in power distribution centers located in a separate conditioned room. Each channel has its own hydraulic systems center which is used to raise/lower the banks from the channel and to control automatic wiping systems to clean the quartz sleeves. --The UV facility was constructed within two existing chlorine contact tanks with all flow routed through the structure for the duration of the project, except for several 2-to-5-day long shutdowns. When sufficient contact time was no-longer available within the existing structure, gaseous chlorine chemical inductors were installed at the upstream ends of the two secondary effluent pipes that convey flow to the existing structure, and the retention time within the pipes was utilized.