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Metaphosphate reversion in Laboratory and Pipe‐Rig Experiments
Author(s) -
Holm Thomas R.,
Edwards Marc
Publication year - 2003
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.1002/j.1551-8833.2003.tb10343.x
Subject(s) - reversion , metaphosphate , polyphosphate , sodium , phosphate , chemistry , materials science , mineralogy , metallurgy , biochemistry , gene , phenotype
Reversion of sodium metaphosphate was studied in two types of experiments. The “beaker” experiments used stoppered glass containers, pH‐buffered solutions, variable calcium (Ca) concentrations, and either 2 or 4 mg/L total phosphorus. The rate of orthophosphate [(PO 4 ) –3 ] production increased as the Ca concentration increased. There was <10% reversion after 24 days for systems with no Ca, and >70% reversion for systems with 120 mg/L Ca. (PO 4 ) –3 production was first‐order with respect to total polyphosphate. The rate constants were an approximately linear function of the logarithm of the Ca concentration. The “pipe‐rig” experiments used sections of copper and lead pipe that had been exposed to modified Boulder, Colo., tap water. Metaphosphate reversion was much more rapid in the pipe‐rig experiments than in the beaker experiments, and the rate of reversion increased substantially as the pipes aged over a period of years.