Corrosion Control Optimization Using Lead Pipe Loops

摘要

In an effort to further optimize their corrosion control strategy, a Lake Michigan water utilityrntested several phosphate inhibitors for their effectiveness to control lead. The objective of thisrnresearch was to show through pipe loop testing, the impact of different forms and dosages ofrnphosphate-based corrosion inhibitors on lead levels. Furthermore, this study investigated thernimpact of seasonal temperature variations on lead levels and the role of deposition formation inrncorrosion control.rnTesting was completed using multiple pipe loop systems. Each loop was constructed of two 15-rnfoot legs of 1-inch lead service line gathered from the utility's distribution system. Water flowedrnthrough the loops at 2 feet per second (ft/s) for 16 hours and then stagnated for 8 hours. Samplesrnwere collected after approximately 7 hours of stagnation. Several conditions were tested over arnthree year period. Overall results from the testing showed the following:rn□ Orthophosphate was more effective than polyphosphate for controlling lead levelsrn□ Orthophosphate alone was as effective as blended phosphate in controlling lead levelsrn□ Lead levels were moderately impacted by temperature – lead levels increased at higherrntemperaturesrn□ Short-term variations in phosphate feed did not seem to impact lead levelsrn□ Phosphate application may result in the formation of a deposit as it combines with waterrntreatment chemicals, such as aluminumrn□ Lead levels and phosphate doses can be optimized to meet multiple objectives.