Stress Free Clarifier Operation: Use of State-Point Analysis to Make Secondary Clarifier Operating Decisions at Northwest Cobb WRF

The Northwest Cobb Water Reclamation Facility, located northwest of Atlanta, Georgia is owned and operated by the Cobb County Water System. During 2003, the plant began experiencing some settling problems, and blanket levels began to rise. To address this issue and avoid any potential compliance problems, the plant staff focused on analyzing the clarifier operation, and using state point analysis as an operating tool. State-point analysis is frequently used by engineers in evaluating clarifier capacity, but historically it has not been used widely by plant operators because of its mathematical complexity and lack of user-friendly computer programs. This paper will discuss the experience of the operating staff in using this tool. It will be presented in two parts:(1) Summary paper discussing the Northwest Cobb WRF operation, development of Vesilind settling parameters for different settling conditions, and the operating results at the plant.(2) A User's Manual for operators, with examples of different operating conditions at the Northwest Cobb WRF.