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MEASURING AND MODELING DISINFECTION WALL DEMAND IN METALLIC PIPES
Citation:
Grayman, W. M., L A. Rossman*, M. A. Gill, Y. Li, AND D. E. Guastella. MEASURING AND MODELING DISINFECTION WALL DEMAND IN METALLIC PIPES. ASCE-EWRI Proceedings 2002 Conference on Water Resources Planning and Management, Roanoke, VA, 05/19-22/2002.
Description:
A field test procedure was developed and implemented in Detroit to estimate chlorine loss due to wall demand in older 6" (152 mm) and 8" (203 mm) diameter, unlined cast iron pipes. The test results produced extremely high wall reaction rate coefficients that increased significantly with flow rate. These results could not be represented successfully by the mass transfer-based wall reaction model widely used in most distribution system modeling software. An alternative shear stress model, in which the wall reaction rate coefficient is proportional to the shear stress developed at the pipe wall, was found to be consistent with the observed data. Additional field work is needed to refine and validate the effects of wall demand on chlorine loss in a pipe and to develop characteristic wall demand coefficients for pipes of different age and material. The field testing procedure developed for estimating chlorine wall demand proved to be effective and reproducible for the range of older, small diameter, unlined cast iron pipes that were studied.