City Selects New UV System for Plant Upgrade
In 1999, the City of Goldsboro was faced with an expansion of its 10.8 mgd Water Reclamation Facility (WRF) to 14.2 mgd. There were several hydraulic and process challenges during design...
In 1999, the City of Goldsboro was faced with an expansion of its 10.8 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 city of Goldsboro installed a low pressure/high-intensity horizontal array UV disinfection system.
During the conceptual design phase, the city relayed its 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.
Several disinfection alternates were evaluated. Ultraviolet disinfection ultimately was chosen as the primary disinfection system.
The City of Goldsboro wanted a UV disinfection system with demonstrated reliability and proven low maintenance at a reasonable cost. During the design of this project, the most feasible and available UV technologies for wastewater disinfection included a low pressure/low-intensity horizontal lamp array, a low pressure/high-intensity horizontal lamp array, a low pressure/high-intensity vertical lamp array, and a medium pressure/high-intensity horizontal lamp array.
After careful consideration and an enormous amount of research, the low pressure/high-intensity horizontal array system was chosen as the best alternative for the City of Goldsboro.
The low pressure/high-intensity system requires one-third the number of lamps needed for a traditional low pressure/low-intensity system, therefore reducing the structure footprint and the amount of equipment to be maintained.
Two manufacturers were considered. Both provided automatic lamp cleaning systems, variable power electronic ballasts, and PLC based programming for dosage control. Furthermore, the infrastructure required for the installation was similar for the two systems.
The bid process was planned to collect sufficient information to evaluate each system on the basis of capital cost as well as operational and maintenance cost. The bid results from these two companies were analyzed for a 20-year life cycle using an interest rate of 8%. Labor cost, power cost, and lamp replacement cost were escalated at an inflation rate of 3% each year.
A system offered by Wedeco UV Technologies was selected and placed in service in mid October 2002. Since then, flows at the WRF have ranged from 5 mgd to as high as 25 mgd. Overall, the system has performed well with an average fecal coliform count of 1 to 6 colonies per 100 ml. Operation and maintenance costs are currently being compiled for comparison to the values collected during the bidding process.