Engineered Struvite Precipitation: Impacts of Component-Ion Molar Ratios and pH
Publication: Journal of Environmental Engineering
Volume 131, Issue 10
Abstract
Struvite precipitation has the potential for removing and recovering phosphorus from agricultural wastewater streams, such as concentrated animal feeding operations wastewater. However, impacts of anticipated component-ion molar ratios and potentially interfering ions are unknown as are the compounding pH relationship with respect to all potential complexes. This research experimentally investigates and mathematically models these factors. Emphasis is placed upon the composition of formed deposits and model validation with experimental data. Results show that calcium is a major interfering ion affecting the deposit composition, decreasing struvite purity. X-ray diffraction (XRD) and scanning electron microscopy + energy dispersive spectrometry were used to study the deposit structure and elemental composition. Results revealed that the precipitates formed at a pH of 8.7 have regular crystal shape, and XRD analysis confirmed that the precipitates are high-purity struvite. Higher leads to the formation of amorphous precipitate and decreases the struvite purity in the deposits. To maximize struvite purity, the ratio of Ca to P should be less than 0.5 and the pH near 8.7.
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Acknowledgments
This research was funded by the United States Environmental Protection Agency (XP-99795901-0). The writers also thank Dr. Eric Bohannan at the Material Research Center and Dr. Scott Miller at the Electron Microscopy Laboratory at the University of Missouri-Rolla for technical assistance in analysis. The writers are also grateful for the help offered by Dr. Cynthia Henny, Dr. George Qiang, Stephen Homan, and other students at the Environmental Research Center, University of Missouri-Rolla.
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Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 131 • Issue 10 • October 2005
Pages: 1433 - 1440
Copyright
© 2005 ASCE.
History
Received: Aug 4, 2004
Accepted: Dec 20, 2004
Published online: Oct 1, 2005
Published in print: Oct 2005
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