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The Operator's Guide to Monitoring Secondary Clarifier Performance

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The State Point Analysis (SPA) procedure provides exceptional insight into the expected performance of activated sludge secondary sedimentation basins. Yet, the operating guidance offered by the SPA is not applied regularly and with confidence – particularly in day-to-day operations. Such lack of use may stem from the perceived complexity of the procedure, including the (unnecessary) need to perform graphical constructions. The paper seeks to encourage the application of SPA principles by presenting straightforward algebraic and spreadsheet calculations for assessing the risks of clarification or thickening failure in clarifiers. Clarifier performance is monitored by evaluating a Clarification Safety Factor, based on comparing the observed settling velocity of the sludge with the overflow rate in the clarifiers. Similarly, a calculated Thickening Safety Factor provides warning of impending process limitations due to deteriorating settleability or limited return sludge pumping capacity. The mathematical background is summarized and step-by-step calculations are detailed in the paper.


Document Type: Research Article

DOI: http://dx.doi.org/10.2175/193317708X339349

Affiliations: Carollo Engineers, 10540 Talbert Ave., Fountain Valley, CA

Publication date: June 1, 2008

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  • Water Practice™ publishes peer-reviewed articles and reports focusing on applied water studies. Topics include monitoring, facility operations and maintenance, management, policy, and other issues of interest and concern to water practitioners. The Journal publishes on a monthly to bi-monthly basis and is available online only.
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