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Nitrification kinetics is important for process design, optimization and capacity rating of activated sludge wastewater treatment plants. Assessment of nitrification behavior historically has focused on measuring the nitrifier maximum specific growth rate, μA. Very little attention has been directed at the importance of nitrifier organism decay rate, bA (also referred to as kD), and in many instances the decay rate has been assumed negligible. However, incorrect assessment of decay rate leads to errors in the μA estimate; the magnitude of the error depends on the μA measurement method employed. This paper illustrates why decay rate is important when measuring μA, and that the decay rate is significant. The paper also explains why measurement methods for nitrifier decay may have underestimated the decay rate. Analysis demonstrates that the magnitude of the μA growth rate temperature correction coefficient is impacted by the assumed decay rate. A low decay rate results in an overly severe temperature correction; this has important implications for process analysis and plant capacity rating. This research formed part of a WERF project on Standardization and Demonstration of Methods for Measuring Wastewater Characteristics for Activated Sludge Modeling.

Document Type: Research Article


Publication date: January 1, 2002

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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