AWWA DSS69201

The City of Northampton, Massachusetts began operations of their 6.5 mgd water treatment plant in January, 2008. Prior to delivering water to its customers, the Massachusetts Department of Environmental Protection (DEP) required that the disinfection contact time of the plant's clearwell be determined with a tracer study. The tracer study was conducted by Metcalf & Eddy in accordance with the guidelines set forth in the U.S. Environmental Protection Agency's Guidance Manual on Determining Disinfection Contact Time. Because the plant was not on-line at the time of the tracer study, several constraints were in place that limited the amount of time and the flow rate at which the study could be conducted. This paper presents details on an efficient approach that M&E used and demonstrates how T₁₀/T was calculated from both the increasing and receding dose tests without achieving a steady fluoride level between tests. Includes tables, figures.