Tuesday, September 10, 2024
2:00 PM - 2:30 PM
UV Disinfection at Cahaba WRF: Lessons Learned from Design, Construction, and Startup
Clean Water Technology

The original ultraviolet (UV) disinfection equipment at the Cahaba River Water Reclamation Facility (WRF), owned and operated by the Jefferson County Environmental Services Department, was a medium-pressure lamp system, installed around 2002. The facility’s UV structure has three parallel concrete channels , with disinfection equipment installed in two of these channels, with the third channel available for emergency bypass. The UV system was originally sized for a total treatment capacity of 100 MGD; this was subsequently deemed oversized because the plant’s upstream treatment processes were designed for a peak hourly flow (PHF) of 35 MGD, with an average daily flow (ADF) through the system of 4 MGD. This resulted in the original UV system operating inefficiently at the low end of its practical range, with lamp technology that has become obsolete . As part of the current WRF Improvements Project, the original UV system is being replaced with the latest, most efficient low-pressure, high-output lamp technology. The new UV system is sized for 40 MGD total treatment capacity to better match the PHF of the plant and will operate with two duty channels of 20 MGD each. This presentation will highlight benefits of the new UV system, which include lower power consumption and access to less costly repair parts to maintain the system. Because the new UV system has a much smaller footprint than the existing system, the existing UV channels had to be modified to accommodate the new system and its hydraulic requirements. Elevated platforms were built around the existing UV structure to house the power, control, and hydraulic components. As of October 2023, one of the two UV channels is fully operational, and the second channel is scheduled for completion by January 2024. The complete construction procedures for each channel follow specific requirements for equipment installation, field testing, system startup, and routine effluent monitoring. These procedures help confirm the satisfactory performance of the system under actual long-term operating conditions.