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Secondary Clarifier Operational Testing Increases Facility Capacity
Author: David J. Kinnear, Leland Myers, Marko Hahn, Denny S. Parker
Date: 10/01
Presented at WEF 74th Annual Conference and Exposition, Atlanta, GA October 13-17, 2001

The Central Davis County Sewer District (CDCSD) conducted a long-term secondary clarifier stress test to verify that state point analysis accurately predicts clarifier capacity. The stress testing indicated that SPA accurately predicted capacity to a much greater degree than previous research as indicated by the following four criteria: 1. Prediction of the thickening failure point. 2. Prediction of relief of thickening failure point. 3. Prediction of equilibrium MLSS concentration. 4. Prediction of sludge blanket elevation. Stress testing included continuos flow meter and solids probe instrumentation ensuring that the clarifier mass balance could be verified. The mathematics of the SPA technique were corrected for situations in which the influent recycle flow does not equal the effluent, as is often the case in treatment facilities with poorly-designed flow splitting structures. At CDCSD, the SPA verification allowed the facility to be successfully rerated to 9.9 mgd from 7.9 mgd without the construction of additional facilities and received approval for the rerating by the Utah Department of Environmental Quality.