AWWA DSS54635

AWWA DSS54635 Tampa Bay Water Corrosion and Re-Equilibration Study
Conference Proceeding by American Water Works Association, 09/01/2001

Hockley, Lenore C.;Troutt, John;Reiber, Steve

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This paper discusses a corrosion and re-equilibration study developed by Tampa Bay Water to evaluate the extent of iron release and copper corrosion in their member governments' distribution systems. The primary goal of the corrosion and re-equilibration study was to assess the potential for blended water quality issues relative to pipe-water interactions in the distribution system and in the customers' homes. Some of the Tampa Bay Water member utility groundwater sources are heavily mineralized with high concentrations of alkalinity and hardness, as well as chloride, sulfate, and other inorganic constituents. Similarly, the organic content of some baseline water sources is variable in both concentration and character. In the future, some of the historic groundwater will be blended with desalinated seawater treated at a reverse osmosis plant and surface water treated at an ozone/granulated activated carbon plant. This study assesses the potential impacts of various proposed blending scenarios and determined what water chemistry changes may be appropriate and necessary. In terms of materials, there are two distinct concerns relative to re-equilibration and corrosion effects. The first is that iron release from old, small-diameter, galvanized iron service lines and household plumbing has the potential to cause significant degradation in the aesthetic quality (colored water), although not the safety, of the distributed water. The second is that modification of the quality of the distributed water may impact copper and lead-bearing surfaces and change member governments' compliance status relative to the Lead and Copper Rule. Both the surface character and the chemistry of each of the materials at issue are unique and different. Therefore, separate testing protocols were used to evaluate the respective impacts on iron-based pipes versus the impacts to lead and copper surfaces Includes tables, figures.