AWWA WQTC69485

This paper focuses on water treatment plant design, specifically how innovative process and hydraulic design translates into real world conditions at operating facilities. Data presented here compares original design values with field measurements and operational data. Treatment performance of the new facility is quantified and compared to the original plant. The new 150-million-gallon-per-day (mgd) Scott Candler Water Treatment Plant (SCWTP), located in the Atlanta metropolitan area, is one of the largest and most sophisticated facilities in the southeastern United States. The new plant replaced the original 128-mgd conventional surface water treatment plant, first built in 1942 and expanded eight times afterward. During planning and preliminary design, DeKalb County staff recognized the need for additional treatment barriers and reduced disinfection byproduct (DBP) concentrations. To accomplish these goals, a combination of advanced treatment techniques and proven technology were selected including high-rate sedimentation, ozonation, and deep-bed biological filtration. The new facility was designed to achieve current and future regulatory requirements, and to meet high standards for reliability and risk-based redundancies. Since full scale production began in July 2007, the SCWTP has been meeting or exceeding treatment and process goals set during design phase. Settled water turbidities have been reduced. TOC removal within the treatment process has increased. DBP levels in the distribution system have been reduced. In addition to notable process design for the new plant, the hydraulic design includes several unique features. The intermediate ozone facility includes six contactors, three on either side of a central gallery, with each side having a tapered inlet channel to aid in flow distribution. The contactors are also equipped with an innovative design feature to turn inlet flow downward toward the ozone diffusers located at the bottom of the first cell. Includes figures.