Phosphate Inhibitors and Red Water in Stagnant Iron Pipes

Document Type

Article

Journal/Book Title/Conference

Journal of Environmental Engineering

Volume

126

Issue

12

Publisher

American Society of Civil Engineering

Publication Date

2000

First Page

1096

Last Page

1102

Abstract

This four-year study evaluated the effect of phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Study parameters included pH and alkalinity, age of the pipe, water stagnation time, and inhibitor type. For iron release, addition of phosphate inhibitors had no statistically significant effect (at 95% confidence) in two-thirds of the experiments. In the remaining experiments, addition of orthophosphate or zinc orthophosphate always increased iron concentration. Polyphosphate addition decreased iron release at only one water quality and increased it at other conditions. For weight loss, polyphosphate inhibitor dosing did not decrease the extent of scale buildup or overall weight loss. Orthophosphate dosing reduced overall weight loss at only one water quality condition; at all other conditions, the addition of orthophosphate had a detrimental effect.

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