AWWA ACE62986

DeKalb County, Georgia, is responsible for potable water treatment and distribution for nearly 700,000 citizens of the metro Atlanta region. Due to continued growth in the region, the county decided to build a new potable water treatment plant and decommission their existing facility built in the 1940s. The new facility, designed to be constructed on adjacent property to allow continued use of existing clearwells and high-service pumping stations, is designed to be initially permitted at 150 million gallons per day (mgd). However, it is designed to operate at a hydraulic capacity of 200 mgd, with an additional 30 mgd of redundant capacity. The new plant was designed to use advanced treatment technologies to achieve current and future regulatory requirements and meet high standards for reliability and risk based redundancy. The treatment process for the new facility includes pre-ozonation, high-rate clarification with plate settlers, intermediate ozonation for microbial control and DBP precursor reduction followed by deep-bed GAC biofilters, and finished water chemical application. To minimize water loss, the plant is designed to operate as a zero discharge facility with all filter backwash and solids streams being equalized and clarified and ultimately being recycled. Key recycle streams are treated through an ultraviolet disinfection system. Solids from the facility are treated at a new dewatering building that houses centrifuges and sludge pumping equipment. Innovative approaches in design and construction, such as shared wall construction and utilizing an onsite concrete batching plant to supply more than 120,000 cubic yards of concrete, resulted in final construction costs for this facility of $1.02 /gal of capacity (that includes an additional 25% redundant capacity). Locating the new facility adjacent to the existing facility allowed for county operations and maintenance staff to observe and participate in the construction of their facility, and provided the advantage of being able to recycle water to the raw water reservoirs during startup phase without having to send water to the distribution system. Transition from the existing plant to the new facility included challenges associated with loss of key County staff due to retirement, schedule challenges, and developing a transition plan to transfer operations from the existing facility to the new plant. This paper presents the unique challenges in design, construction, and startup of the southeast's largest and most advanced surface water treatment plant. Includes table, figures.