Challenges and Innovative Solutions for an Ultraviolet Disinfection System Upgrade at the Goldsboro Water Reclamation Facility, North Carolina

In 1999, the City of Goldsboro was faced with an expansion of their 10.8 million gallon per day (MGD) Water Reclamation Facility (WRF) to 14.2 MGD. There were several hydraulic and process challenges during design, but one notable challenge was the conversion from chlorine disinfection to an ultraviolet (UV) disinfection facility. The existing disinfection capabilities consisted of gas chlorine disinfection and with gaseous sulfur dioxide for dechlorination. During the conceptual design phase, the City relayed their concerns with gas chlorination relative to the hazardous gasses present on the plant site and in full view of the public, the OSHA requirements for extensive emergency response plans, and the changes in the building code requirements for hazardous gas storage since the last plant expansion. During conceptual design, several disinfection alternates were evaluated. Ultraviolet disinfection was chosen as the primary disinfection system.This purpose of this paper is to highlight the challenges of the upgrade to an UV disinfection system with the concurrent decommission of the gas chlorination and dechlorination facility. Challenges included the navigation of the different available UV disinfection technologies relative to the bidding laws in North Carolina; the selection of an UV disinfection system to optimize operating costs; the evaluation of disinfection methods for alternate water streams, such as off-site reclaimed water use, tertiary filter algae control, and constructed wetlands polishing; and hydraulic considerations and equipment redundancy.The UV low pressure-high intensity disinfection system has been successfully placed in operation at the Goldsboro WRF. Ultimately, the success of the conversion from an existing gas chlorination system to a UV disinfection system depended on meshing the critical design and bidding details with respect to the City of Goldsboro's goal for total water management solutions.