AWWA WQTC60662

In an effort to further optimize their corrosion control strategy, a Lake Michigan water utility tested several phosphate inhibitors for their effectiveness to control lead. The objective of this research was to show through pipe loop testing, the impact of different forms and dosages of phosphate-based corrosion inhibitors on lead levels. Furthermore, this study investigated the impact of seasonal temperature variations on lead levels and the role of deposition formation in corrosion control. Testing was completed using multiple pipe loop systems. Each loop was constructed of two 15- foot legs of 1-inch lead service line gathered from the utility's distribution system. Water flowed through the loops at 2 feet per second (ft/s) for 16 hours and then stagnated for 8 hours. Samples were collected after approximately 7 hours of stagnation. Several conditions were tested over a three year period. Overall results from the testing showed the following: orthophosphate was more effective than polyphosphate for controlling lead levels; orthophosphate alone was as effective as blended phosphate in controlling lead levels; lead levels were moderately impacted by temperature and increased at higher temperatures; short-term variations in phosphate feed did not seem to impact lead levels; phosphate application may result in the formation of a deposit as it combines with water treatment chemicals, such as aluminum; and, lead levels and phosphate doses can be optimized to meet multiple objectives. Includes tables, figures.