AWWA WQTC62406

In an effort to optimize their corrosion control strategy, a Lake Michigan water utility testedseveral phosphate inhibitors for their effectiveness to control lead. The objective of this researchwas to show through pipe loop testing, the impact of different forms and dosages of phosphate-basedcorrosion inhibitors on lead levels in the water. Furthermore, this study investigated theimpact of seasonal temperature variations on lead levels and the role of deposition formation incorrosion 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. To simulatedistribution system flow, water flowed through the loops at 2 feet per second (ft/s) for 16 hoursand then stagnated for eight hours. Samples were collected after approximately seven hours ofstagnation. Several conditions were tested over a four year period. Overall results from thetesting showed the following:orthophosphate levels can be optimized to maintain low lead levels while limiting theamount of deposition in the distribution system;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, lead levels increased at highertemperatures;the results show that once a phosphate layer forms on the walls of the pipes, temporaryinterruptions do not dissolve the scale, which provides the necessary protection againstincreased lead levels, a small or "maintenance" dose of phosphate appears to be sufficientfor maintaining optimized lead levels. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2005

Number of Pages:

12

File Size:

1 file , 780 KB