Determination of the required surface area of a final clarifier for an activated-sludge system

A generic methodology for determining the required surface area of a final clarifier is presented. Clarification and thickening requirements are integrated to form a unified procedure for final clarifier design. The new method is based on results obtained by Yuen (2002) on the solids flux theory for a secondary clarifier; it does not require the specification of recycle rate, which is computed as an output of the method. ne author shows that there is a minimum required surface area (A(m)) for a final clarifier under the thickening requirement when the designed recycle rate is set at the maximum allowable value (F-R)(m) (at the critical state). The designed surface area and the return activated sludge pumping capacity can be determined by applying a safety factor to A(m) and (F-R)(m) respectively. The method is shown to conform to conventional design criteria under typical design conditions.