AWWA JAW56652

In 1994 and 2001, US water providers were surveyed about their use of phosphate inhibitors. Responses pointed to widespread use of phosphate inhibitors, including polyphosphate, orthophosphate, zinc orthophosphate, and phosphate blends. From 1994 to 2001, a number of respondents shifted from poly/orthophosphate blends to orthophosphate, a trend viewed as beneficial because polyphosphate compounds have been shown to be detrimental to metal corrosion under some circumstances. Although many water suppliers used phosphate inhibitors, few conducted any scientific tests to determine the applicability of inhibitors to their particular circumstances. In selecting a phosphate inhibitor, most utilities relied on vendor data or reports of chemical success at another facility. Even at larger utilities, where managers were aware of potential drawbacks of inhibitors, many did not know the exact composition of the phosphate chemicals they were using. Survey results indicate that many utilities are incurring considerable costs to add inhibitors without direct proof of the chemical's efficacy in their particular water. Understanding how and why inhibitors are used is the first step toward helping utilities develop effective strategies to meet the diverse goals of corrosion control and water quality. More support is also needed to help utilities make informed decisions about inhibitor use. Water providers need to look at their phosphate inhibitor use, examine their reasons for using phosphates, and base their phosphate selection on hard data and their individual water conditions. Includes 44 references, tables, figures.