In an effort to 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 in the water. 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. To simulate
distribution system flow, water flowed through the loops at 2 feet per second (ft/s) for 16 hours
and then stagnated for eight hours. Samples were collected after approximately seven hours of
stagnation. Several conditions were tested over a four year period. Overall results from the
testing showed the following:
orthophosphate levels can be optimized to maintain low lead levels while limiting the
amount 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 higher
temperatures;
the results show that once a phosphate layer forms on the walls of the pipes, temporary
interruptions do not dissolve the scale, which provides the necessary protection against
increased lead levels, a small or "maintenance" dose of phosphate appears to be sufficient
for maintaining optimized lead levels. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 780 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 12 |
| Published : | 11/01/2005 |
